anthropomorphism

The supernova and the quasar: the hungriest guy in the universe followed the ultimate toaster

Keith S. Taber

Communicating astronomical extremes

I was recently listening to a podcast of an episode of a science magazine programme which included two items of astronomy news, one about a supernovae, the next about a quasar. I often find little snippets in such programmes that I think work making a note of (quite a few of the analogies, metaphors and similes – and anthropomorphisms – reported on this site come from such sources). Here, I went back and listened to the items again, and decided the discussions were rich enough in interesting points to be worth taking time to transcribe them in full. The science itself was fascinating, but I also thought the discourse was interesting from the perspective of communicating abstract science. ¹

I have appended my transcriptions below for anyone who is interested – or you can go and listen to the podcast (episode 'Largest ever COVID safety study' of the BBC World Service's Science in Action).

Space, as Douglas Adams famously noted, is big. And it is not easy for humans to fully appreciate the scales involved – even of say, the distance to the moon, or the mass of Jupiter, let alone beyond 'our' solar system, and even 'our' galaxy. Perhaps that is why public communication of space science is often so rich with metaphor and other comparisons?

When is a star no longer a star (or, does it become a different star?)

One of the issues raised by both items is what we mean by a star. When we see the night sky there are myriad visible sources of light, and these were traditionally all called stars. Telescopes revealed a good many more, and radio telescopes other sources that could not detected visually. We usually think of the planets as being something other than stars, but even that is somewhat arbitrary – the planets have also been seen as a subset of the stars – the planetary or wandering stars, as opposed to the 'fixed' stars.

At one time it was commonly thought the fixed stars were actually fixed into some kind of crystalline sphere. We now know they are not fixed at all, as the whole universe is populated with objects influenced by gravity and in motion. But on the scale of a human lifetime, the fixed stars tend to appear pretty stationary in relation to one another, because of the vast distances involved – even if they are actually moving rather fast in human terms.

Wikipedia (a generally, but not always, reliable source) suggests "a star is a luminous spheroid of plasma held together by self-gravity" – so by that definition the planets no longer count as stars. What about Supernova 1987A (SN 1987A) or quasar J0529-4351?

"This image, taken with Hubble's Wide Field and Planetary Camera 2in 1995, shows the orange-red rings surrounding Supernova 1987A in the Large Magellanic Cloud. The glowing debris of the supernova explosion, which occurred in February 1987, is at the centre of the inner ring. The small white square indicates the location of the STIS aperture used for the new far-ultraviolet observation. [George Sonneborn (Goddard Space Flight Center), Jason Pun (NOAO), the STIS Instrument Definition Team, and NASA/ESA]" [Perhaps the supernova explosion did not actually occur in February 1987]

Supernova 1987A is so-called because it was the first supernova detected in 1987 (and I am old enough to remember the news of this at the time). Stars remain in a more-or-less stable state (that is, their size, temperature, mass are changing, but, in proportional terms, only very, very slowly²) for many millions of years because of a balance of forces – the extremely high pressures at the centre work against the tendency of gravity to bring all the matter closer together. (Imagine a football supported by a constant jet of water fired vertically upwards.) The high pressures inside a star relate to a very high temperature, and that temperature is maintained despite the hot star radiating (infra-red, visible, ultraviolet…) into space ³ because of the heating effect of the nuclear reactions. There can be a sequence of nuclear fusion reactions that occur under different conditions, but the starting point and longest-lasting phase involves hydrogen being fused into helium.

The key point is that when the reactants ('fuel') for one process have all (or nearly all) been reacted, then a subsequent reaction (fusing the product of a previous phase) becomes more dominant. Each specific reaction releases a particular amount of energy at a particular rate (just as with different exothermic chemical reactions), so the star's equilibrium has to shift as the rate of energy production changes the conditions near the centre. Just as you cannot run a petrol engine on diesel without making some adjustments, the characteristics of the star change with shifts along the sequence of nuclear reactions at its core.

These changes can be quite dramatic. It is thought that in the future the Earth's Sun will expand to be as large as the Earth's orbit – but that is in the distant future: not for billions of years yet.

Going nova

Massive stars can reach a point when the rate of energy conversion drops so suddenly (on a stellar scale) that there is a kind of collapse, followed by a kind of explosive recoil, that ejects much material out into space, whilst leaving a core of condensed nuclear matter – a neutron star. For even more massive stars, not even nuclear material is stable, as there is sufficient gravity to even collapse nuclear matter, and a black hole forms.

It was such an explosion that was bright enough to be seen as a 'nova' (new star) from Earth. Astronomers have since been waiting to find evidence of what was left behind at the location of the explosion – a neutron star, or a black hole. But of course, although we use the term 'nova', it was not actually a new star, just a star that was so far away, indeed in another galaxy, that it was not noticeable – until it exploded.

Dr. Olivia Jones (from the UK Astronomy Technology Centre at The Royal Observatory, Edinburgh) explained that neutron stars form from

"…really massive stars like Supernova 1987A or what it was beforehand, about 20 times the mass of a Sun…

So, what was SN 1987A before it went supernova? It was already a star – moreover, astronomers observing the Supernova were studying

…how it evolves in real time, which in astronomy terms is extremely rare, just tracing the evolution of the death of a star…

So, it was a star; and it died, or is dying. (This is a kind of metaphor, but one that has become adopted into common usage – this way of astronomers talking of stars as having births, lives, careers, deaths, has been discussed here before: 'The passing of stars: Birth, death, and afterlife in the universe.') What once was the star, is now (i) a core located where the star was – and (ii) a vast amount of ejected material now "about 20 light years across" – so spread over a much larger volume than our entire solar system. The core is now a "neutron star [which] will start to cool down, gradually and gradually and fade away".

So, SN 1987A was less a star, than an event: the collapse of a star and its immediate aftermath. The neutron star at is core is only part of what is left from that event (perhaps like a skeleton left by a deceased animal?) Moreover, if we accept Wikipedia's definition then the neutron star is not actually a star at all, as instead of being plasma (ionised gas – 'a phase of matter produced when material is too hot to exist as, what to us seems, 'normal' gas) it comprises of material that is so condensed that it does not even contain normal atoms, just in effect a vast number of atomic nuclei fused into one single object – a star-scale atomic nucleus. So, one could say that SN 1987A was no so much a star, as the trace evidence of a star that no longer existed.

And SN 1987A is not alone in presenting identity problems to astronomers. J0529-4351 is now recognised as being possibly the brightest object in the sky (that is, if we viewed them all from the same distance to give a fair comparison) but until recently it was considered a fairly unimpressive star. As doctoral researcher Samuel Lai (Research School of Astronomy and Astrophysics, Australian National University) pointed out,

this one was mis-characterised as a star, I mean it just looks like one fairly insignificant point, just like all the other ones, right, and so we never picked it up as quasar before

But now it is recognised to only appear insignificant because it is so far away – and it is not just another star. It has been 'promoted' to quasar status. That does not mean the star has changed – only our understanding of it.

But is it a star at all? The term quasar means 'quasi–stellar object', that is something that appears much like a star. But, if J0529-435 is a quasar, then it consists of a black hole, into which material is being attracted by gravity in a process that is so energetic that the material being accreted is heated and radiates an enormous amount of energy before it slips from view over the black hole's event horizon. That material is not a luminous spheroid of plasma held together by self-gravity either.

This video from the European Southern Observatory (ESO) gives an impression of just how far away (and so how difficult to detect) the brightest object in the galaxy actually is.

These 'ontological' questions (how we classify objects of different kinds) interest me, but for those who think this kind of issue is a bit esoteric, there was a great deal more to think about in these item.

"A long time ago, in a galaxy far, far away"

For one thing, it was not, as presenter Roland Pease suggested, strictly the 37th anniversary of the SN 1987A – at least not in the sense that the precursor star went supernovae 37 years ago. SN 1987A is about 170 000 light years away. The event, the explosion, actually occurred something like 170 000 years before it could be detected here. So, saying it is the 37th anniversary (rather than, perhaps, the 170 037^th anniversary ⁴) is a very anthropocentric, or, at least, geocentric take on things.

Then again, listeners are told that the supernova was in "the Large Magellanic Cloud just outside the Milky Way galaxy" – this is a reasonable description for someone taking an overview of the galaxies, but there is probably something like 90,000 light-years between what can be considered the edges of our Milky Way galaxy and this 'close by' one. So, this is a bit like suggesting Birmingham is 'just outside' London – an evaluation which might make more sense to someone travelling from Wallaroo rather than someone from Wolverhampton.

It is all a matter of scale. Given that the light from J0529-4351 takes about twelve billion years to reach us, ninety thousand light years is indeed, by comparison, just outside our own galaxy.

But the numbers here are simply staggering. Imagine something the size of a neutron star (whether we think it really is a star or not) that listeners were informed is "rotating…around 700 times a second". I do not think we can actually imagine that (rather than conceptualise it) even for an object the size of a pin – because our senses have not evolved to engage with something spinning that fast. Similarly, material moving around a black hole at tens of thousands of kilometres per second is also beyond what is ready visualisation. Again, we may understand, conceptually, that "the neutron star is over a million degrees Celsius" but this is just another very big number way that is outside any direct human experience.

Comparisons of scale

Thus the use of analogies and other comparisons to get across something of the immense magnitudes involved:

"If you think of our Sun as a tennis ball in size, the star that formed [SN] 87A was about as big as the London Eye."
"A teaspoon of this material, of a neutron star, weighs about as much as Everest"
the black home at the centre of the quasar acquires an entire Sun worth of mass every single day
the black hole at the centre of the quasar acquires the equivalent of about four earths, every single second
the quasar is about five hundred trillion times brighter than the Sun, or equivalent to about five hundred trillion suns

Often in explaining science, everyday objects (fridges, buses – see 'Quotidian comparisons') are used for comparisons of size or mass – but here we have to shift up to a mountain. The references to 'every single day' and 'every single second' include redundancy: that is, no meaning is lost by just saying 'every day' and 'every second' but the inclusion of 'single' acts a kind of rhetorical decoration giving greater emphasis.

Figurative language

Formal scientific reports are expected to be technical, and the figurative language common in most everyday discourse is, generally, avoided – but communication of science in teaching and to the public in journalism often uses devices such as metaphor and simile to make description and explanations seem more familiar, and encourage engagement.

Of course, it is sometimes a matter of opinion whether a term is being used figuratively (as we each have our own personal nuances for the meanings of words). Would we really expect to see a 'signature' of a pulsar? Not if we mean the term literally, a sign made by had to confirm identify, but like 'fingerprint' the term is something of a dead metaphor in that we now readily expect to find so-called 'signatures' and 'fingerprints' in spectra and D.N.A. samples and many other contexts that have no direct hand involvement.

Perhaps, more tellingly, language may seem so fitting that it is not perceived as figurative. To describe a supernova as an 'evolving fireball' seems very apt, although I would pedantically argue that this is strictly a metaphor as there is no fire in the usual chemical sense. Here are some other examples I noticed:

"we have been searching for that Holy Grail: has a neutron star formed or has a black hole been left behind"
"the quasar is not located in some kind of galactic desert"
there is a "storm, round the black hole"
"the galaxies are funnelling their material into their supermassive black hole"
"extraordinarily hot nuclear ember"
"a dense dead spinning cinder"
"the ultimate toaster"

Clearly no astronomer expects to find the Holy Grail in a distant galaxy in another part of the Universe (and, indeed, I recently read it is in a Museum in Ireland), but clearly this is a common idiom to mean something being widely and enthusiastically sought.⁵

A quasar does exist in a galactic desert, at least if we take 'desert' literately as it is clearly much too hot for any rain to fall there, but the figurative meaning is clear enough. The gravitational field of the black hole causes material to fall into it – so although the location, at the centre of a galaxy (not a coincidence, of course), means there is much material around, I was not sure how the galaxy was actively 'funnelling' material. This seems a bit light suggesting spilt tea is being actively thrown to the floor by the cup.

A hot ember or cinder may be left by a fire that has burned out, and one at over a million degrees Celsius might indeed 'toast' anything that was in its vicinity. So, J0529-4351 may indeed be the ultimate toaster, but not in the sense that it is a desirable addition to elite wedding lists.

Anthropomorphism is a particular kind of metaphor that describes non-human entities as if they had the motivations, experiences, drives, etc., of people. The references to dying stars at least suggest animism (that the stars are in some sense alive – something that was once commonly believed ⁶), but there are other examples (that something is 'lurking' in the supernova remnant) that seem to discuss stellar entities as if they are deliberate agents like us. In particular, a black hole acquiring matter (purely due to its intense gravitational field) was described as feeding:

quasars are basically supermassive black holes just swallowing up all the stars and rubbish around
a quasar is feeding from the accretion disc
a monstrous black hole gobbling up anything within reach
just sat [sic] there, gobbling up everything around it
it has to have been feeding for a very, very long time
it will eat about four of those earths, every single second
in a particularly nutritious galaxy
a quasar that has been declared the hungriest object in the universe

There is clearly some kind of extended metaphor being used here.

Feeding frenzy?

The notion of a black hole feeding on surrounding material seems apt (perhaps, again, because the metaphor is widely used, and so familiar). But there seems a lot more 'negative analogy' than 'positive analogy: that is the ways in which (i) a black hole acquires matter, and (ii) an organism feeds, surely have more points of difference than similarity?

For advanced animals like mammals, birds, fish, snails and the like, feeding is a complex behaviour that usually involves active searching for suitable food, whereas the black hole does not need to go anywhere.
The animal has specialist mouth-parts and a digestive system that allows it to break apart foodstuff. The black-hole just tears all materials apart indiscriminately:"it's just getting chopped up, heated up, shredded".
The organism processes the foodstuff to release specific materials (catabolism) and then processes these is very specific ways to support is highly complex structure and functioning, including the building up of more complex materials (anabolism). The black hole is just a sink for stuff.
The organism takes in foodstuffs to maintain equilibrium, and sometimes to grow in very specific, highly organised ways. The black hole just gets more massive.

A black hole surely has more in keeping with an avalanche or the collapse a tall building than feeding?

One person's garbage…?

Another feature of the discourse that I found intriguing was the relative values implicitly assigned to different material found in distant space. There is a sense with SN 1987A that, after the explosion, the neutron star in some sense deserves to be considered the real remnant of the star, whilst the other material has somehow lost status by being ejected and dispersed. Perhaps that makes sense given that the neutron star remains a coherent body, and is presumably (if the explosion was symmetrical) located much where the former star was.

But I wonder if calling the ejected material – which is what comprises the basis of "an absolutely stunning supernova [which is] beautiful" – as 'debris' and 'outer debris"? Why is this material seen as the rubbish – could we not instead see the neutron star as the debris being the inert residue left behind when the rest of the star explored in a magnificent display? (I am not suggesting either should be considered 'debris', just playing Devil's advocate.)

Perhaps the reference to being able to "isolate the core where the explosion was from the rest of the debris" suggests all that is left is debris of a star, which seems fairer; but the whole history of the universe, as we understand it, involves sequences of matter changing forms quite drastically, and why should we value one or some of these successive phases as being the real product of cosmic evolution (stars?) and other phases as just rubbish? This is certainly suggested by the reference to "supermassive black holes in the middle of a galaxy … swallowing up all the stars and rubbish".

Let's hear it for the little guys

Roland Pease's analogy to "the muck at the bottom of your sink going down into the blender" might also suggest a tendency to view some astronomical structures and phenomenon as intrinsically higher status (the blender/black hole) than others (clouds of dust, or gas or plasma – the muck). Of course, I am sympathetic to the quest to better understand "these guys" (intense quasars already formed early in the universe), but as objectively minded scientists we should be looking out for the little guys (and gals) as well.

Appendix A: "the star hidden in the heart of [the] only supernova visible from Earth"

"If you are listening to this live on Thursday, then you're listening to the 37th anniversary of the supernova 1987A, the best view astronomers have had of an exploding star in centuries, certainly during the modern telescope era. So much astrophysics to be learned.

All the indications were, back then, that amidst all the flash and glory, the dying star should have given birth to a neutron star, a dense dead spinning cinder, that would be emitting radio pulses. So, we waited, and waited…and waited, and still there's no pulsing radio signal.

But images collected by the James Webb telescope in its first weeks of operation, peering deep into the ejecta thrown out by the explosion suggest there is something powerful lurking beneath.
Olivia Jones is a James Webb Space Telescope Fellow at Edinburgh University and she helped in the analysis."

"87A is an absolutely stunning supernova , it's beautiful, and the fact that you could see it when it first exploded with the naked eye is unprecedented for such an object in another galaxy like this.

We have been able to see how it evolves in real time, which in astronomy terms is extremely rare, just tracing the evolution of the death of a star. It's very exciting."

"I mean the main point is the bit which we see when the star initially explodes , we see all the hot stuff which is being thrown out into space, and then you've got this sort of evolving fireball which has been easiest to see so far."

"Yes, what see initially is the actual explosion of the star itself right in the centre. What happens now is then we had a period of ten years when you couldn't actually see very much in the centre. You needed these new telescopes like Webb and JWST to see the mechanics of the explosion and then, key to this is what was left behind, and we have been searching for that Holy Grail: has a neutron star formed or has a black hole been left behind at the centre of this explosion. And we've not seen anything for a very long time."

"And this neutron star, so this is the bit where the middle of the original star which at the ends of its life is mostly made of iron, just gets sort of crushed under it's own weight and under the force of the explosion to turn itself entirely into this sort of ball of neutron matter."

"Yeah, it's the very, very core of the star. So the star like the Sun, right in the centre is a very dense core, but really massive stars like Supernova 1987A or what it was beforehand, about 20 times the mass of a Sun.

If you think of our Sun as a tennis ball in size, the star that formed 87A was about as big as the London Eye. So it's a very massive star. The pressure and density right in the centre of that star is phenomenal. So, it creates this really, really, compact core. A teaspoon of this material, of a neutron star, weighs about as much as Everest. So, it's a very, a very dense, very heavy, core that is left behind."

"These were the things which were first detected in the 1960s, because they have magnetic fields and they rotate, they spin very fast and they cause radio pulsations and they're called pulsars. so When the supernova first went off I know lots of radio astronomers were hoping to see those radio pulsations from the middle of this supernova remnant."

"Yes. So, we know really massive stars will form a black hole in the centre, 30, 40, 50 solar masses will form a black hole when it dies. Something around 20 solar masses you'd expect to form a neutron star, and so you'd expect to see these signatures, like you said, in the radiowaves or in optical light of this really fastly rotating – by fastly rotating it can be around 700 times a second – but you would expect to see that signature or some detection of that. But even with all these telescopes – with the radio telescopes, X-ray observatories, Hubble – we've not seen that signature, before and so we are wondering, has a black hole been formed? We've seen neutrinos, so we thought the neutron star had formed, but we've not had that evidence before now."

"So, as I understand it, what your research is doing is showing that there's some unexplained source of heat in the middle of the debris that's been thrown out, and that's what your associating which what ought to be a neutron star in the middle, is that roughly speaking the idea?"

"So, the wonderful thing thing about the Webb telescope, you can see at high resolution both the ring, the outer debris of the star, and right at the very centre where the explosion was, but it's not just images we take, so it's not just taking a photograph, we also have this fantastic instrument or two instruments, called spectrographs, which can break down light into their individual elements, so very small wavelengths of light, it's like if you want to see the blue wavelength or the red wavelength, but in very narrow bands."

"And people may have done this at school when they threw some salt into a Bunsen burner and saw the colours, it's that kind of analysis?"

"Yes. And so what we see where the star was and where it exploded was argon and sulphur, and we know that these needed an awful lot of energy, to create these, and I mean a lot, of energy. And the only thing that can be doings this, we compared to many different kinds of scenarios, is a neutron star."

"So this is basically an extraordinarily hot nuclear ember, that's sort of sitting in the middle."

"Yes, right in the middle and you can see this, cause Supernova 1987A is about 20 light years across, in total, and we can isolate the core where the explosion was from the rest of the debris in this nearby galaxy, which I think is fantastic."

"Do you know how hot the surface of this star is and is it just sort of the intense heat, X-ray heat I imagine, that's coming off, that's causing all this radiation that you're seeing."

"I hope you are ready for a very big number."

"Go on."

"The neutron star is over a million degrees Celsius."

"And so, that's just radiating heat, is it, from, I mean this is like the ultimate toaster?"

"Yes, so what eventually will happen over the lifetime of the universe is this neutron star will start to cool down, gradually and gradually and fade away. But that'll be many, many billions of years from now.

What we currently have now is one of the hottest things you can imagine, in a very small location, heating up all its surroundings. I would not want to be anywhere nearby there."
Roland Pease interviewing Dr. Olivia Jones (Edinburgh University)

Appendix B: "possibly the brightest object in our universe"

"Now 1987A was, briefly, very bright. Southern hemisphere astronomy enthusiasts could easily spot it in the Large Magellanic Cloud just outside [sic] the Milky Way galaxy. But it was nothing like as bright as JO529-4351 [J0529-4351], try memorising that, its a quasar twelve or so billion light years away that has been declared the brightest object in the universe and the hungriest. At first sight, it's an anonymous, unremarkable spot of light of trillions on [sic] an astronomical photo. But, if you are an astronomer who knows how to interpret the light, as Samual Lai does, you will find this is a monstrous black hole gobbling up anything within reach. Close to the edge of all that we can see."

"So this quasar is a record breaking ultra-luminous object, in fact it is the most luminous object that we know of in the universe. Its light has travelled twelve billion years to reach us, so it's incredibly far object, but it's so intrinsically luminous that it appears bright in the sky."

"And as I understand it, you identified this as being a very distant and bright object pretty recently though you have gone back through the catalogues and its was this insignificant speck for quite a long time."

"Yes, indeed. In fact we were working on a survey of bright quasars, so we looked at about 80% of the sky using large data sets from space satellites. Throughout our large data sets, this one was mis-characterised as a star, I mean it just looks like one fairly insignificant point, just like all the other ones, right, and so we never picked it up as quasar before. Nowadays we are in the era of extremely astronomical, pardon the pun, data sets where in order to really filter thorough them we have these classification algorithms that we use. So, we have the computer, look at the data set, and try to learn what we are looking at, and pick out between stars and quasars."

"Now, is it also interesting, they were discovered about sixty years ago, the first quasars. These are basically supermassive black holes in the middle of a galaxy that's just swallowing up all the stars and rubbish just around it, and that's the bit that for you is quite interesting in this instance?"

"Yes, exactly, and the quasar owes its luminosity to the rate at which it is feeding from this accretion disc, this material that's swirling around, like a storm, with the black hole being the eye of the storm."

"I mean, I think of it as being a bit like the muck at the bottom of your sink going down into the blender at the bottom, it's just getting chopped up, heated up, shredded, and, I mean what sort of temperatures are you talking about? What, You know, what kind of energy are you talking about being produced in this system?"

"Yes ,so the temperatures in the accretion disc easily go up to tens of thousands of degrees, but talking about brightness, the other way that we like to measure this is in terms of the luminosity of the Sun, which gives you are sense of scale. So, this quasar is about five hundred trillion times brighter than the Sun, or equivalent to about five hundred trillion suns."

"And it's been doing this sort of constantly, or for really for a long time, I mean it's just sat there, gobbling up everything around it?"

"Yeah, I mean the mass of the quasar is about 17 billion solar masses, so in order to reach that mass it has to have been feeding for a very, very long time. We work it out to be about one solar mass per day, so that's an entire Sun worth of mass every single day. Or if you like to translate that to more human terms, if you take the Earth and everybody that's on it, and you add up all of that mass together, it will eat about four of those earths, every single second."

"I suppose what I find gob-smacking about this is (a) the forces, the gravitational forces presumably involved in sweeping up that amount of material, but (b) it must be an incredibly busy place – it can't be doing this in some kind of galactic desert."

"Yes, indeed, I mean these quasars, these super-massive black holes are parts of their galaxies, right, they're always in the nuclear regions of their host galaxies, and in some way the galaxies are funnelling their material into their supermassive black hole."

"But this one must be presumably a particularly, I don't know, nutritious galaxy, I guess. It is so far away, you can't make out those kinds of details."

"We can however make out that some of that material moving around, inside the storm, round the black hole, their dynamics are such that their velocities reach up to tens of thousands of kilometres per second."

"Why are you looking for then? Is it because you just want to break records – I'm sure it's not. Or is it, that you can see these things a long way away? Is it, it tells you about the history of galaxies?"

"I mean we can learn a lot about the universe's evolution by looking at the light from the quasars. And in fact, the quasar light it tells you a lot about not just the environment that the quasar resides in, but also in anything the quasar light passes through. So, you can think of this, lights from the quasar, as a very distant beacon that illuminates information about everything and anything in between us and the quasar."

"I mean the thing that I find striking is, if I've read the numbers right, this thing is so far away that the universe was about a billion years old. I mean I suppose what I'm wondering is how did a black hole becomes so massive so early in the universe?"

"Ah see, I love this question because you are reaching to the frontier of our current understanding, this is science going as we speak. We are running into an issue now that some of these black holes are so massive that there's not enough time in the universe, at the time that we observe them to be at, in order for them to have grown to such masses as they are seen to be. We have various hypotheses for how these things have formed, but at the moment we observe it in its current state, and we have to work backwards and look into the even older universe to try to figure out how these guys came to be."
Roland Pease interviewing Dr. Samuel Lai (Australian National University)

Notes

¹ Having been a science teacher, I find myself listening to, or reading, science items in the media at two levels

I am interested in the science itself (of course)
I am also intrigued by how the science is presented for the audience

So, I find myself paying attention to simplifications, and metaphors, and other features of the way the science is communicated.

Teachers will be familiar with this. Curriculum selects some parts of science and omits other parts (and there is always a debate to be had about wither the right choices are made about what to include, and what to omit). However, it is rare for the selected science itself to be presented in 'raw' form in education. The primary science literature is written by specialists for other specialists, and to a large extent by researchers for other researchers in the same field – and is generally totally unsuitable for a general audience.

Curriculum science is therefore an especially designed representation of the science intended to be accessible to learners at a particular stage in their education. Acids for twelve years olds or natural selection for fifteen year olds cannot be as complex, nuanced and subtle as the current state of the topic as presented in the primary literature. (And not just because of the level f presentation suitable for learners, but also because in any live field, the work at the cutting edge will by definition be inconsistent across studies as this is just where the experts are still trying to make the best sense of the available evidence.)

The teacher then designs presentations and sequences of learning activities to engage particular classes of learners, for often teaching models and analogies and the like are needed as stepping stones, or temporary supports, even to master the simplified curriculum models set out as target knowledge. Class teaching is challenging as every learner arrives with a unique nexus of background knowledge, alternative conceptions, relevant experiences, interests, vocabulary, and so forth. Every class is a mixed ability class – to some extent. The teacher has to differentiate within a basic class plan to try and support everyone.

I often think about this when I listen to or read science journalism or popular science books. At least the teacher usually knows that all the students are roughly the same age, and have followed more-or-less the same curriculum up to that point. Science communicators working with the public know very little about their audience. Presumably they are interested enough in the topic or science more generally to be engaging with the work: but likely of a very diverse age, educational level, background knowledge: the keen ten year old to the post-doctoral researcher; the retired engineer to the autistic child with an intense fascination in every detail of dinosaurs…

I often find myself questioning some of the simplifications and comparisons used on science reports in the media – but I do not underestimate the challenge of reporting on the latest findings in some specialist area of science in an 'academically honest' way (to borrow a term from Jerome Bruner) in a three minute radio slot or 500 words in a magazine. So, in that spirit, I was fascinated by the way in which the latest research into Supernova 1987A and J0529-4351 was communicated, at least as much as the science itself.

² That is, the flux of material emitted by our Sun, for example, is quite significant in human terms, but is minute compared to its total mass. Our sun has cooled considerably in the past few billions of years, but that's long time for it to change! (The Earth's atmosphere has also changed over the same time scale, which has compensated.)

³ Some very basic physics (Isaac Newton's law of cooling) tells us that objects radiate energy at a rate according to their temperature. Stars are (very large and) very hot so radiate energy at a high rate. An object will also be absorbing radiation – but the 'bath' of radiation it experiences depends on the temperature of its surroundings. A hot cup of coffee will cool as it is radiating faster than it is absorbing energy, because it is hotter than its surroundings. Eventually it will be as cool as the surroundings and will reach a dynamic equilibrium where it radiates and absorbs at the same rate. (Take the cooled cup of coffee into the sauna and it will actually get warmer. But do check health and safety rules first to see if this is allowed.)

The reference to how

"what eventually will happen over the lifetime of the universe is this neutron star will start to cool down, gradually and gradually and fade away. But that'll be many, many billions of years from now"

should be understood to mean that the cooling process STARTED as soon as there was no internal source of heating (form nuclear reactions or gravitational collapse) to maintain the high temperature; although the process will CONTINUE over a long period.

⁴ That weak attempt at humour is a variant on the story of the museum visitors who asked the attendant how old some ancient artefacts were. Surprised at the precision of the reply of "20 012 " years, they asked how the artefacts could be dated so precisely. "Well", the attended explained, "I was told they were twenty thousand years old when I started, and I've worked here for twelve years."

Many physics teachers will not find this funny at all, as it is not at all unusual for parallel mistakes to be made by students. (And not just students: a popular science book suggested that material in meteors can be heated in the atmosphere to temperatures of up to – a rather precise – 36 032 degrees! (See 'conceptions of precision').

⁵ The Holy Grail being the cup that Jesus is supposed to have used at the last supper to share wine with his disciples before he was arrested and crucified. Legend suggests it was also used to collect some of his blood after his execution – and that it was later brought to England (of all places) by Joseph of Arimathea, and taken to Glastonbury. The Knights of King Arthur's Round Table quested to find the Grail. It was seen as a kind of ultimate Holy Relic.

⁶ Greek and Roman cultures associated the planets (which for them included the Sun and Moon) with specific Gods. Many constellations were said to be living beings that have been placed in the heavens after time on earth. Personification of these bodies by referring to them in gendered ways ('he', 'she') still sometimes occurs.

Read about personification

In his cosmogony, Plato had the stars given a kind of soul. Whereas Aristlotle's notion of soul can be understood as being something that emerges from the complexity of organisation (in organisms), Plato did imply something more supernatural.

And then the plant said…

Do plants deliberately deceive insects?

Keith S. Taber

Do plants deceive insects by deliberately pretending to be rotting meat? (Spoiler alert. No, they do not.)
[Image credits: Rafflesia – Maizal, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons; Amorphophallus titanum – ailing moose, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons; fly and beetle – by Clker-Free-Vector-Images from Pixabay]

Mysterious plants

Earlier this week I heard an episode of BBC Radio 4's 'Start the Week' programme entitled 'Mysterious Plants' ¹ (which can be heard here). It is always good to hear science-related episodes of series such as this. The mysterious plants included Amorphophallus titanum ² believed to have the largest un-branched inflorescence of any plant in the world; and the parasitic genus Rafflesia, one species of which is thought to have the largest individual flowers in the world. ³

I could not help notice, however, that according to the guests, some plants are sentient beings, able to reflect on their circumstances, and to deliberately act in the world. Botanist Dr Chris Thorogood (of University of Oxford's Oxford Botanic Garden and Arboretum) described the parasitic plant Rafflesia as being 'pretty sneaky'. This is anthropomorphic, because – if taken literally – it implies deliberate behaviour.

No insects were deceived in the making of this programme

He was outdone, in this sense though, by evolutionary chemical ecologist Dr Kelsey Byers (of The John Innes Centre, Norwich) who told listeners,

"So these flies and beetles like to lay their eggs on rotting meat', and the flower goes 'oh, what if I also looked and smelled like rotting meat', or like the Amorphophallus titanum you might see at Kew Gardens for example, 'what if I also emitted heat, just like a pile of rotting meat?' …

So, what it's attracting are flies and beetles that essentially are going 'Ooh, that smells like food, that looks like food, I'm going to lay my eggs here, it's going to be great, my babies will have a great chance to survive'.

But there's, there's no food, it is deceiving them, it's basically saying 'I'm, mimicking the food, come and stay'."
Dr Kelsey Byer speaking on Radio 4

Now, I assume that Dr Byers does not intend this as a literal account of the biology discussed. In strict scientific terms, it is rather misleading

"flies and beetles like to lay their eggs on rotting meat"

I get a little uneasy when non human entities are described as liking things, as this does not reflect the subjective human experience of liking, say chocolate or Pink Floyd. But this unease probably links to the common alternative conception that students acquire in chemistry that atoms 'like' or 'want' full shells of electrons. Dr Byers could quite reasonably suggest that "flies and beetles tend to lay their eggs on rotting meat"; that their behaviour reflects a preference; and that is what 'likes' means. Fair enough.

"the flower goes 'oh, what if I also looked and smelled like rotting meat' … 'what if I also emitted heat, just like a pile of rotting meat?'…"

Now, flowers do not express themselves in language, and in any case (I'm fairly certain) do not have thoughts to potentially be expressed in language. Plato (2008) has his spokesperson Timaeus suggest that plants were "the kind of living being that…knows nothing of belief, reasoning, and intelligence". ⁴ So, no, plants do not do this – at least not literally.

"flies and beetles essentially are going 'Ooh, that smells like food, that looks like food, I'm going to lay my eggs here, it's going to be great, my babies will have a great chance to survive'…"

So insects are animals, and I can be less sure they do not have any kind of thought processes. (But it seems likely conscious thought requires a much more complex nervous system than that of any insect.) The 'essentially' means that Dr Byers is not suggesting they are directly expressing these ideas, but only indirectly (perhaps, those behavioural preferences again?) But I am pretty sure that even if insects could be said to 'think' at some level, they do not have formal concepts of food. I do not doubt that the fly experiences something when it eats that is different to when it is not eating, but I really doubt it is meaningful to suggest a fly has any concept of eating or can be said to 'know' when it is eating.

Surely, a fly feeding is pure instinct. It responds to cues (smell much more than sight I should think given the fly's compound eye {perhaps excellent for spotting movement, but – identifying potential meals?}, and the likely distance away that food might be found) to approach some material (without thinking, 'oh good, that smells like food!') and then further cues (greater intensity of the smell, perhaps; texture underfoot?) trigger eating, or egg laying. To be honest, I think even as a human I have sometimes behaved this way myself when distracted by a problem occupying all my conscious attention! (To clarify, that's when eating, not laying eggs.)

I do not think flies or beetles have any concept of 'babies'. I am pretty sure they do not know that egg laying is a reproductive function (even if they can be said to have any awareness that they are laying eggs), and will lead to offspring. I'm also pretty sure they are not aware of the issue of infant mortality, and that that they have a greater chance to be a grandparent if they choose the right place to lay their eggs.

The plant is deceiving the insects, it's basically saying 'I'm, mimicking the food, come and stay'.

Again, the plant is not saying anything. If does not have a notion of mimicry, and is not aware it is mimic. It does not have any notions. It is not deliberately deceiving the flies or beetles. It does not know there are flies or beetles in the world. It does not do anything deliberately.

I am not even sure it is right to say the plant deceives. You can only deceive an entity capable of being deceived. Insects are not deceived, just following instincts. The plant does not do anything to deliberately attract or entice the insects – their attraction to the plant is just a consequence of a match of the animal's instincts (not under the control of the insect), and the plant's evolved anatomy, physiology and biochemistry.

Now, as I suggested above, I am pretty sure Dr Byers knows all this (much better than me!) Perhaps this is just a habitual way of talking she has adopted to discuss her work, or perhaps she was deliberately using figurative language on this occasion to help communicate the science to a diverse radio audience. To 'make the unfamiliar familiar' the abstract concepts of science need to be related to more familiar everyday experiences. The narrative here helps to humanise science.

Read about 'making the unfamiliar familiar' in teaching

Dr Byers is not alone in this way of presenting science – it is very common when scientists talk to general audiences (e.g., so, no, vegetarians bees did not realise they were missing out on a potential food source and so decide to start eating meat).

Anthropomorphism and teleology

This type of figurative language is anthropomorphic. That is, it treats non-humans (flowers, whole plants, insects, clouds, atoms…) as if they were human – with human cognition (concepts, deliberate conscious thinking) and motivations and emotions. Humans are part of the natural world, and the extent to which anthropomorphism distorts scientific accounts surely varies. An atom cannot be jealous. Nor a bacterium. But I would think a chimp can be.⁵ What about a fish?

This is a serious issue for science educators because learners often use anthropomorphic language in science lessons, and it is less clear they are doing so figuratively. They may mean this literally – and even if not, may come to habitually use this kind of language and so feel that in doing so they really they can explain phenomena 'scientifically'. But from a technical scientific perspective these are only pseudo-explanations (Taber & Watts, 2000).

Read about the types of pseudo-explanations learners commonly offer

So, sodium reacts with chlorine because the atoms want to fill their shells (Taber & Watts, 1996). So wrong, on so many levels, but so many students think that is the scientific account! Bacteria want to infect us, and seek to become resistant to antibiotics. And so many more examples.

Read about anthropomorphism in students' thinking

Read examples of anthropomorphic explanations in science

The canonical biological explanation is that living things are the way they are because they have evolved to be so, through natural selection. It is natural selection that has led to insects laying eggs in conditions where they are likely to hatch – such as in rotting meat. It is natural selection that has led to some plants attracting insect pollinators by becoming similar to rotting meat – similar, that is, in how those plants are perceived within the insect's unwelt.

But lay people often tend to prefer teleological explanations because they appeal more to our own instincts. It seems that things are the way they are for a purpose: as if a plant was guided towards a new structure because there is an end point, identified from the outset, of becoming attractive to insects that will fertilise the flowers.

As humans behave deliberately and work towards goals, it is easy to transfer this familiar scheme to non-human species. Because human artefacts (the Eiffel Tower, the Pyramids, the iPhone, the international space station) have been designed and built with purposes in mind, it is easy to also see the intricate and effective structures and mechanisms of the living world as also designed with purpose in mind.

Read about teleology

Of course, some of these biological structures can seem so unlikely to have evolved through 'chance' or 'trial and error' that many people find the canonical scientific account non-feasible. (And, it is very hard for people to conceptualise the sheer number of generations over which species have evolved.) Of course, although chance is involved, at each step there is feedback into the system: there is preferential selection of some outcomes. What 'works' is selected not so much because it works, but by virtual of it working.

Evolution is contingent – natural selection can only select the features that are 'in play' at a particular time. But which features remain in play is not just down to chance. ⁶ So, to adopt an analogy, natural selection is not simply a matter of chance, like a number coming up on a roulette wheel. It is more like a game of poker where the cards dealt may be at random, but one can then select which cards to keep, to build up a winning hand. ⁷

Darwin's book on 'various contrivances'

Darwin was very aware of this general problem, and the specific example of how it came to be that some plants need to be fertilised in very particular ways, by particular insects – and would seem to have structures so specific and well matched to their pollinators that it seems incredible they could have evolved rather than had been deliberately designed.

Darwin knew that many people found his account of evolution unconvincing in the face of the subtlety and intricacies of natural forms. He chose to study the orchids in some detail because they showed great diversity in flower structures and often seemed especially well 'designed' (with 'various contrivances') for their particular animal fertilisers. Darwin argued that all these odd structures could be understood to have slowly evolved from a common ancestor plant by myriad small modification of ancestral structures that collectively led to the wide diversification of forms (Darwin, 1862)

A difficult balance for science communicators

So, science communicators – whether teachers or journalists or scientists themselves – have a challenge here. The kind of language that is most likely to engage an audience and make science seem accessible can actually come to stand in the way of genuine understanding of the scientific principles.

I do not think that means figurative language should be completely avoided in discussing science, but it is very important to remember that an account which is intended to obviously be metaphorical may be understood literally because anthropomorphism and teleology seem to make perfectly good sense to most people.

These kinds of pseudo-explanations may not score any credit in science exams, but this way of thinking is perhaps as instinctively appealing to many humans as, say, laying eggs in rotting meat is to some insects.

Work cited:

Darwin, C. (1862) On the various contrivances by which British and foreign orchids are fertilised by insects, and on the good effects of intercrossing. London: John Murray
Plato (2008) Timaeus and Critias (Translator: Robin Waterfield).Oxford University Press, 2008.
Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568. (Download this paper)
Taber, K. S., & Watts, M. (2000). Learners' explanations for chemical phenomena. Chemistry Education: Research and Practice in Europe, 1(3), 329-353. (Download this paper)

Notes:

¹ The enticing episode description is:

"The plant Rafflesia has the world's largest flowers and gives off one of the worst scents; it's also something of a biological enigma, a leafless parasite that lives off forest vines. For the botanist Chris Thorogood, an expert in parasitic and carnivorous plants at the Oxford Botanic Garden and Arboretum, Rafflesia is also an obsession. In his book, Pathless Forest, he goes in search of this mysterious plant in some of the last wildernesses in South East Asia.

Dr Kelsey Byers is an evolutionary chemical ecologist who specialises in floral scent and its influence on the evolution of flowering plants. In her laboratory at the John Innes Centre in Norwich she studies how flowers use different smells to attract their pollinator of choice. From sweet aromas to the stink of rotting flesh, she explores how plants use con-artistry and sexual deception to thrive.

The ethnobotanist William Milliken from Kew Gardens has spent much of his career working with indigenous people in the Amazon to preserve traditional plant knowledge. Now he's focused on collecting folklore about the use of plants to treat ailments in animals in Britain. From wild garlic treating mastitis in cows, to cabbage for flatulence in dogs, he hopes to uncover a cornucopia of plant-based veterinary medicines."
https://www.bbc.co.uk/sounds/play/m001wxkb

² Dr Thorogood helpfully explained that what Amorphophallus titanum actually means is 'giant distorted penis'.

Does a sunflower have large flowers?

³ Some plants have a great many flowers on the same 'head' or inflorescence. Consider the sunflower. From a distance it seems each of the flowers are large, but, on closer inspection, each inflorescence has a great many tiny individual flowers – each one able to produce pollen and be fertilised.

Photograph of bee on sunflower — A bee on a sunflower collecting nectar and pollen. Each of the tiny structures is an individual flower.

A photo-essay showing sunflowers at different stages of development including close-ups of the structures can be seen here.

⁴ Although, to be fair, he went on to suggest that a plant "is aware only of the pleasures and pains that accompany its appetites". I would suggest, not.

⁵ Am I over-cautious? We assume all normal humans beings can potentially feel anger, jealousy, love, fear, etc. But actually no one really knows if anyone else has the same subjective experiences when two people report they are envious, or in love. People could be experiencing something quite different and still using the same label. (This is the qualia issue – e.g., how do I know if the experience I have of red is what you experience? This is something quite different from agreeing on which objects are red.) After all, some people find odours and flavours attractive that others find unpleasant, and the same mode of tickling can lead to quite different responses from different patients.

I think a dog could be sad, and a rabbit can be scared. But I doubt [sic, I mean really doubt] an earthworm could be proud. Unless we can decide where to draw the lines, we really have to wonder if these terms meaningfully transfer across species.

⁶ At the level of an individual's survival and reproduction, there is a lot of chance involved. Being in the right, or wrong, place when a mate, or a predator, appears; or when a flood, or a forest fire, happens, may have little to do with the variations in features within a population. But a slight advantage in attracting the mate or escaping the peril means that over a large population, across many generations, some features will be preferentially passed on.

⁷ Strictly these processes are not random, but 'near enough' for human purposes. A roulette ball is large enough to be a classical object (that is we can ignore the indeterminacy that seems to be part of quantum mechanics) so given the spin of the wheel, and the initial trajectory and entry point of the ball (and such factors as the fiction produced due to the materials involved) it is in principle possible to consider this a deterministic process. That is, particular, precise, starting conditions will lead to distinct, in principle predictable, outcomes. In practice though, no human could control the wheel and ball precisely enough to manufacture a specific outcome. It may as well not be deterministic.

Much the same is true of a pack of cards. Given the original order of the deck and a finite number of specific moves to shuffle the deck, only one new order is possible. It is however again difficult to deliberately shuffle a deck and control the new order (though perhaps not quite impossible – which is why often the person shuffling the deck invites other players to choose cuts within the process).

Sometimes in research, the methodology adopted requires randomisation (for example of individual participants to different experimental conditions) and usually such process as rolling dice or drawing blind ballots are 'good enough' even if not strictly random, as no person could control the outcomes obtained.

Read about the criterion for randomisation in research

Teenage lust and star-crossed electrons

A new study reports a creative approach to modelling the atom motivated by a love story

Keith S. Taber

Perhaps it would be better not to introduce an orbital model until we feel learners are ready to appreciate the quantum jump from concentric orbits to fuzzy, overlapping, infinitely-extended patterns of electronic probability, and the associated complex patterns of energy levels they generate.

A scene from the play 'Romeo and Juliet' — "Grade: B-.
Comment: Your model of the heteronuclear molecule of Romeo-Juliet was creative and aesthetically pleasing, but it was inconsistent because you used rope to stand for the covalent bond when you are representing electrons with apples." (Image by Николай Оберемченко from Pixabay)

The science curriculum contains a good deal of abstract material that is both challenging, and – sadly – not always found intrinsically interesting, to many learners. The teacher has to find what can 'make the unfamiliar familiar', something I have written quite a lot about on this site.

Read about teaching as making the unfamiliar familiar

Modelling 'the' atom

One such abstract topic is the structure of 'the' atom ¹ – an area where learners will likely come across multiple models and diverse representations, and where what is being modelled and represented (as a quanticle – a quantum object) simply cannot be adequately represented concretely. Given that, it is hardly surprising that often even keen and capable learners show alternative conceptions in this topic (Taber, 2002 [Download paper]).

I was therefore intrigued by a recent research paper that described an approach to progressing learners' ideas about atomic structure by asking them to engage with a story. Narrative is a recognised way of helping make the unfamiliar familiar, and here a story was referenced that is familiar to many people: that of Shakespeare's 'star-crossed lovers': Romeo and Juliet.

So, in the storyline, electrons were named after characters from the tragic tale. It is common to relate abstract chemical ideas to social relations (chemistry uses such metaphors as 'sharing electrons', 'nucleus loving' species, reagent species that 'attack' other molecules, and substances that 'compete') – but this does risk the anthropomorphism (that is, treating non-human entities as if they have human qualities) actually confusing learners.

Read about anthropomorphism and science

That is, molecules and ions, and nuclei and electrons are not like people, and do not think or have desires, and so they do not act from motivations such as love or hate or jealousy…

Perhaps this seems SO OBVIOUS that only the weakest student could possibly get confused and think otherwise?

But I know from my own research (e.g., Taber & Watts, 1996 [download paper]) that actually even studious, intelligent learners can come to habitually use anthropomorphic language without noticing that they are explaining chemistry in terms that would only make sense if atoms and molecules and ions and electrons did have preferences, and could think for themselves, and did act accordingly!

Atoms can not care about anything – so they do not care about how many electrons they have, and they never deliberately do anything in order to obtain full shells or octets (as they cannot act under their own volition, of course). But many generally successful, hard-working, intelligent, learners in chemistry classes all over the world seem to think otherwise (Taber, 1998 [Download paper]).

Read about the octet framework – an alternative conceptual framework

Likewise, electrons do not care if they are in an atom or not, or whether they are spin-paired or not (and if so, which other, indistinguishable, electron they are paired with), or which energy level of a system they populate.

The authors of the recent paper (which is open access, so freely available for anyone who wishes to download/read it) claim that students found the story-related activity engaging (which certainly seems likely) and that it helped address some misconceptions about atomic structure. They note that:

"Students do not clearly understand the concept of an orbital" (Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024)

This is a topic that has long interested me so I took a look at the activity the researchers had devised. The learners were

"10th-grade classes, with the participants' average age being between 15 and 16, attending a technical computer science high school ¹…[who] had already studied the atomic model in their chemistry classes during the first half of the year."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

I have taught a basic (planetary) model of atomic structure to students at this age, and also more advanced models to 16-19 year old learners (on A level courses), so I was keen to read about the activity. The authors did not include an explicit statement of the curriculum content which was being treated as target knowledge, although they did include a discussion of their rationale for the story, as well as comments on student work, from which some features could be deduced or inferred. (I would have found it useful to have read an explicit statement of just what the learners were expected to know – what the 'correct' model was meant to be – at the outset of the paper.)

I approached the paper thinking it was ambitious to teach an orbital model of the atom to students of this age. My reading of the story (reproduced below) reinforced that initial impression (I admit, I was challenged in places!) – although the authors certainly felt the students in their research coped well with the challenge.

Although I felt I struggled interpreting some features of the narrative,

A student with a specific learning disorder (SLD), mentioned, "The connection of a fairly complicated topic with such a simple story"
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

It is important to note that the teaching scheme adopted a dialogic approach, where class discussions were included at two points after the students had worked in groups on parts of the activity. The activity was also conceptualised as being part of an enquiry-based learning cycle. So, the material below should be read accordingly, as it does not reflect this wider classroom context.

Read about dialogic teaching

Read about enquiry-based science education

The story

The story is broken into four parts, each leading to a task for the learners (working in groups) to engage in.

Prologue

"Romeo is a bold and dynamic electron found in an atom with seven energy levels. He is at the 4s energy level, together with the faithful Mercutio, his companion on raids. Always upside down compared to him, but then there is no place for two equal electrons in their crew. The two are part of the Montague family, known for being particularly lively.

Juliet is an electron in 2s, she is more tied to her nucleus and in fact she is a Capulet, a rival family to that of the Montagues and decidedly more calm. Juliet is always accompanied by her nurse; they too are turned upside down with respect to each other.

There is a grand ball to which everyone is invited, and, to better organize their arrangement, there is a need to schematize their position."

[Instructions to learners: "Discuss with your classmates what should be the design of the atom where the two families «are» and build
a model"]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Chapter 1 – part 1

"At one point during the dance, Romeo notices Juliet in her orbital, and, even if he occasionally gets close to her, he is unable to stay there permanently: quivering with love, he asks who knows her and what her tastes are in terms of radiations (electrons are well known to be romantics). He discovers that Juliet is obsessed with color harmony and that the color she prefers is purple "486 nm". To get noticed he wants to perform his famous photon–spectroscopic serenade and jump to emit a purple trail.

[Instructions to learners: "Discuss with your teammates to help Romeo understand how far he will have to jump and whether or not he would have gotten closer to Juliet in this way."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Chapter 1 – part 2

"The two are deeply in love and would like to spend the rest of their days together. But Juliet's family hinders them, crying scandal: a Montague cannot be so tied to the nucleus! What to do? The nurse offers Romeo the chance to take her place, but, for her, this would mean losing her place next to Juliet. Romeo and Juliet, very hesitant, then decide to move towards the orbitals occupied by the Montagues. But how to get up there?

While the couple is tormented by this problem, an enlightened friar, Lory, arrives to their rescue with two THz 457s, offering to give them a lift. Despite this help, Romeo and Juliet are unable to reach the Montague orbital, so they loudly invoke another friar, Enzo, asking for new help.

[Instructions to learners: Discuss with your teammates to understand how far they will jump thanks to the first photons and which photons Fra Enzo will have to carry for the two lovers to reach the Montague orbital."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Chapter 2 and epilogue

"Juliet's escape has thrown the entire atomic balance into crisis, forcing some Montagues to change levels in order to maintain overall stability. Then, when the couple comes to the Montagues, they cry out for revenge, and the couple is then forced to flee again.

The Montagues set out in search of Romeo and Juliet but fail because it is not possible to reconstruct the trajectory followed by the two lovers.

The story unfortunately ends in tragedy: the two do manage to free themselves from the influence of their families, but they still understand that they cannot be together. Now condemned to separation, the two lovers decide to draw up a schema of the place (the atom) where they met to remember it forever.

[Instructions to learners: "Discuss with your teammates why this trajectory cannot be reconstructed. End the story with a tragic ending, explaining the reasons for the separation sentence.

EPILOGUE Construct with your teammates a possible model of the scheme realized by Romeo and Juliet."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Interpreting the narrative

Reading the account I had a very mixed response. I am very keen on approaches that use the familiar everyday as ways into teaching complex, abstract ideas; but subject to two provisos:

these everyday analogies are interim supports ('scaffolds'), to be withdraw as soon as they are no longer needed;
teaching needs to focus on the 'negative analogy' (things that do not map across) as well as the 'positive analogy' (the aspects of the comparison that 'work').

The approach here seemed somewhat different. The learners had already been taught a model of the atom earlier in the year, and this activity was intended to be an opportunity to review this prior learning and apply it – and an opportunity for teachers to identify any alternative conceptions elicited by the activity.

Metaphorical meanings?

Romeo and Juliet are not the lovers in the stage play, but electrons. Therefore, in reading the story I identified scientific information (electron Romeo is in a 4s orbital in an atom) and material that seemed to be metaphorical (the electrons Romeo and Mercutio go on 'raids'). I therefore saw the task of reading the story as being in part a decoding of the metaphors that were used.

So, the idea of Romeo and Mercutio being relatively "upside down" was not to be taken literally (electrons do not have ups or downs) but to be a metaphor for spin +¹/₂ and spin –¹/₂, often referred to metaphorically as 'spin up' and 'spin down'. Going on raids was more tricky: in some chemical reactions electron pairs are considered to shift during bond formation (or bond breaking, but that would not refer to an atomic species), but 'raid' suggests a temporary excursion.

I could not understand in what sense Mercutio (the electron, not the fictional character) could be said to be faithful. Electrons respond to physical forces, not personal attachments. Perhaps, I was over-thinking this, and not all the narrative elements did map onto the atomic system? Perhaps that was meant to be part of the challenge for the learners?

A fundamental concern with this kind of comparison is that all electrons are inherently identical, and are only distinguished by the accidental features they acquire in a particular system.

A 2s electron is on average closer to the nucleus, and experiences a greater effective core charge (it is not shielded as much from the nucleus as a 4s electron is) – so the 'tie' (bond) to the nucleus can be understood as analogous to the attractive force operating between the electron and nucleus. ²
The reference to being more calm perhaps refers to how the 2s level is at a 'lower' energy so the 'particularly lively' 4s electrons can be more dynamic?

If Romeo and Mercutio, or even Romeo and Juliet, were swapped it could make absolutely no difference and no one could tell. By giving electrons personal identities they seem to be more like us and less like electrons. Electrons cannot be bold or calm. Romeo and Juliet behave differently because they are in different orbitals at different energy levels, not because they are different electrons. Could learners miss this critical point? If Juliet (or Romeo) moved to a different energy level then she (or he) would change 'personality' – but that would undermine the narrative.

I was not sure how the two families related to anything. Within an atom we could class some electrons alike because they are in the same 'shell' (have the same principal quantum number) – so perhaps the two families were in the n=2 and n=4 levels (the L and N shells being their metaphorical 'houses'). I also could not understand where the ball was meant to be held:

were the electrons to be moved to a new set of orbitals (requiring promotion)
were the electrons meant be moved to outside the atom (requiring ionisation), or
was the ball to take place with the electrons in their current orbitals (but for some reason behaving differently than when no dance was taking place?)

The attraction between Romeo and Juliet (the electrons, not the fictional lovers) was difficult to understand. Certainly, if we adopt a model of electrons moving about in different orbitals ³ then they could sometimes be nearer to each other as atomic orbitals interpenetrate – and if so they would influence each other more (due to their charge and spin) at these times: but this would primarily be a repulsion.

Interpenetrating fields of play. If two sports pitches were marked out overlapping on the same ground, then there would be places that were part of both fields of play.

(Consider a school with very limited space for sports pitches. Perhaps they mark up a soccer pitch and a field hockey pitch overlapping. If both soccer and hockey players train at the same time there will be places that are part of both pitches, and players from the two sports can come close together in those areas. {This is just an analogy. The two sports would need to schedule practice at different times to avoid accidents!})

It seemed to me that the learners were being asked to read the account at two levels – some features of the story were metaphors (such as when the lovers left the atom only to find they had separate indeterminate trajectories) when other features seemed to be simply plot devices to provde an engaging narrative. I thought that the students were being asked to work out which bits of the story they should take seriously as corresponding to part of an atomic model, and which just moved the narrative on. I though this might be challenging for the 14-15 year old learners (as I was struggling!)

Orbitals and transitions

Some features of the story seemed potentially likely to encourage alternative conceptions. Juliet's preference for light of wavelength 486 nm risks the association of a spectral line with an electron or an energy level, rather than with a transition.

The specific references to 486 nm and 457 THz radiation seemed to suggest that a quantative model was needed – where an atom would actually show spectral lines reflecting transitions associated with radiation of these specific characteristics.

The rationale

Unlike the students, I had access to some of the resource designers' thinking as the paper included a rationale for the storyline. This acknowledged that

The specific location of the grand ball remains implicit [?], as it is challenging to conceive of electrons dancing outside the metaphorical context of "moving swiftly". However, all the other character details are essential for initiating the story and allowing mathematical and physical problems and situations to emerge."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

This seemed to confirm that the learners were expected to build a quantitative model. This was reiterated later in the rationale

"Through calculations of energy transitions and the resulting orbital distances, students gain insight into the quadratic proportionality that underlies these phenomena [?], prompting a gradual reshaping of their personal notions regarding orbital distances."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

I was not sure what was mant by 'orbital distances', and return to this point below. I was also not sure how quadratic proportionality underlay energy transitions.

This was only one of the points in the paper where I got the impression that in the teaching model adopted, energy levels and orbitals were not only being associated, but at times almost seen as equivalent and interchangeable.

A diagnostic assessment opportunity

The rationale seemed to confirm that the activity was deliberately testing whether students associated spectral lines with energy levels rather than transitons between levels,

"To elucidate the intriguing connection between emission and electron transitions to different energy levels, we introduce a romantic-comedic twist, employing Juliet's passion for color harmony as a plot device. Juliet's preference for the color purple is strategically chosen to align with her energy level, prompting students to contemplate the intriguing relationship between spectroscopy lines and electron energy transitions."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

On the other hand, my suspicion that I had been reading too much into the narrative, and trying too hard to interpret plot twists was rather undermined by being told,

"Take, for instance, Romeo's desire to gain Juliet's attention and their joint pursuit of a life away from their feuding families. This narrative intricately parallels the fundamental interplay of orbitals within the model, establishing a direct and compelling link between the characters' human drama and the pivotal role of orbitals in the model."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Indeed? I was struggling to map across some of the story, even when (unlike the students) I had access to the rationale:

"At the outset, the consequences of Romeo and Juliet's choices become apparent: the voids within the nucleus [?] are replenished with new electrons [?], ultimately disturbing the equilibrium of the two feuding families. This disruption leads them to share orbits [sic], not fueled by anger but by fate. The Montagues seek revenge, yet they grapple with the inability to reconstruct the electrons' orbitals due to the uncertainty principle."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

A lot of this went over my head.

The uncertainty principle would not interfere with characterising orbitals, only with being able to posit specific electron trajectories. The orbitals do not belong to electrons ("the electrons' orbitals") but are characteristic of an atomic system with its configuration of charges.

A hybrid model?

Perhaps, in part, my confusion was due to my not being clear about what the target knowledge was- exactly which kind of model was it hoped the students would produce?

"After studying the planetary and Bohr atomic models, students cannot easily move beyond them"
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

It seemed clear from the paper that the learners were expected to have moved beyond a model with planetary orbits, to a model with orbitals, and so from the idea of electrons moving on definite trajectories, to being found somewhere within the orbitals. ³

There was historically a range of models of the atom (even 'the Bohr model' was actaully a series of models), and long ago Rosaria Justi and John Gilbert (Justi & Gilbert, 2000) pointed out that often in teaching we end up presenting 'hybrid' models – that is, models which have features drawn from across several of the different scientific models. Did the curriculum these students followed set out such a hybrid model for students to learn? ⁴

An atom with seven energy levels?

At the start of the story, the students were told "Romeo is …found in an atom with seven energy levels". I am not sure any real atom could only have seven energy levels. My understanding is that any atom has in principle an infinite number of energy levels, but the the spacing of the levels gets successively smaller, so they converge on a limit (which makes ionisation feasible). Even the hydrogen atom has an infinite number of energy levels, but only one is populated with an electron.

So, I wondered if possibly this was meant to be read as "Romeo is …found in an atom with seven populated energy levels"?

A sensible starting point for a student is to assume the atom is initially in its ground state (as under normal circumstances they usually are). If the reference to seven energy levels means populated energy levels, and students are to assume the atom starts in the ground state then presumably learners are meant to assume the atom they need to model is one of the first transition series (i.e., elements with electronic configurations from 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹ to 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰: that is an atom from one of the elements scandium to zinc).

However, later there is a reference to electron Romeo wanting to "jump to emit a purple trail". But he needs to jump 'down' (to a lower energy level) both to get closer to Juliet and indeed to "emit a purple trail" (i.e., for Romeo to be promoted, light would need to be absorbed not emitted) – which is only possible if the atom is NOT initially in its ground state, so that there will be an orbital at a lower energy level not fully occupied. That potentially complicates the model to be built.

For one thing, if the atom is not in its ground state, then atoms of elements of lower atomic mass than scandium might be the target atom to be modelled? Indeed, any atom from the element nitrogen (in the highly excited configuration 1s¹ 2s¹ 2p¹ 3s¹ 3p¹ 4s¹ 3d¹ ) on to zinc could theoretically have seven occupied energy levels. It did not help that there seemed to be no information on how many electrons were in this atom – four were specified, and we are told unspecified other 'family' members lived there, and two other characters were name-checked without it being explicit if they were also in the atom or just passing (from the local Abbey perhaps – would that be an atom of a noble gas?)

Interorbital distances?

As noted above, the authors refer to how they "delve into the concept of interatomic orbital distances", but this seems an oxymoron.

"From the analysis of the drawings, it emerges that the students' final drawings can be traced back to three different types of atom representation (R):

R1: orbits/orbitals represented at varying distances to convey the concept of energy levels more effectively;

R2: orbits/orbitals represented at correct distances according to the radius;

R3: attempt to depict the concept of orbitals and the correct distances between them."

Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

The authors refer to how in a figure assigned to category R3, "The distances between the spheres reflect the correct distances according to n²", but this does not strictly relate to an orbital model.

Orbitals do not have edges, so it is not possible to measure how far they are from anything. Strictly, every orbital reaches to infinity (even if the electron density soon gets so rare that it becomes effectively zero). The point is that this is a gradual falling-off and there is no sudden drop that we might think of as an edge.

Commonly orbitals are represented either with

probability contour lines, or
colour or shading showing differnt levels of electron density (i.e., the relative probabilities of an electron in the orbital being 'found' at different regions of the orbital), or
more simply with probability envelopes.

Those envelopes show where, say, 90% or 95% of the electron density is located – which means 10% or 5% of the electron density (that is inside the orbital) lies outside the envelope drawn. So, these lines are to soem degree arbitrary, conventional and do not correspond to anything physical ('real').

One could measure the distance between the centres of two different orbitals, but this would be a trivial issue when the orbitals are in the same atom. (That is, the atomic orbitals are all centred on the nucleus, so the centres have no distance between each other.)

This is different to a planetary type model where electrons are considered to be a certain distance from the nucleus, so the orbits have quantifiable radii. In moving to an orbital model we have to think of fuzzy overlapping volumes of space, and the notion of there being set distances between orbitals just does not work in this model.

Imagine being asked to report the distance between the soccer pitch and the hockey pitch.

And then imagine having that task when there are no marked out edges to the pitches.

The energy levels associated with the orbitals can be considered to have specific values, and so there are definite differences ('distances'?) between the levels in that sense – but these would be energy gaps: analogical 'distances' on an energy scale, not actual distances.

The authors suggest that,

Despite their discussion about orbitals, [for the students' final drawings] all groups drew orbits, representing them as lines depicting the trajectories of electrons
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

But that is not so clear from the diagrams of the models and the students' own comments.

Student 1: "In a circle, we drew lines. But we know that electrons don't follow that precise path; they exist in orbitals, which are regions where electrons are more likely to be found. So, we don't know the precise radius because it's a region. Therefore, in my opinion, since the radius can always vary, you can't use the radius to depict the atomic model; it's more accurate to use energy levels."

…

Teacher: "Here you have drawn the distances increasingly closer. Why?"

Student 2: "Because it represented differences in energy levels."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Some groups of students seem to have drawn concentric circles representing energy levels rather than orbits or shells or orbitals. Normally, energy level diagrams are not drawn like that, but this seems a perfectly reasonable form of representation providing it is explained.

Spherical orbitals

We also have to bear in mind that only s-orbitals have spherical symmetry. (A 'shell' of orbitals in an atom would be spherically symmetrical only if each orbital was singly or fully occupied. But it was not clear how many electrons were in this atom.)

The first seven energy levels in any atom or ion with more than one electron will be associated with p- and d-orbitals as well as s-orbitals. So, even if orbitals were represented with probability envelopes, and these were treated (incorrectly) as if the edges of the orbitals, then there would be no fixed 'distances' between the edges of any comparisons involving these non-spherical orbitals.

Not all orbitals have spherical geometry (Image by Smiley _p0p from Pixabay)

At this point it is interesting to examine the samples of student models represented in the paper. All of them are drawn with circles. The authors of the paper seemed satisfied with this aspect of the models.

Making sense of 486 nm and the 'THz 457s'

I pointed out above that my reading of the information given about the atom that it seemed the target atom could be from one of a wide range of elements. It seems I got this completely wrong,

We conclude this paper by highlighting a limitation of the story we have designed from a physical point of view. Our story does not fit the real atomic structure. Indeed, we chose to consider a hydrogen atom with multiple electrons because we thought it was easier for the students to manipulate. We are aware of the fact that this may represent a critical point of our story, but in the classes where we experienced the activity it has not created problems, since the students noticed this inconsistency and talked about it with the teacher.
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024

Now, by definition, a model is never quite like what is modelled – or it ceases to be a model and becomes a perfect replica. But "a hydrogen atom with multiple electrons" is not an atom at all, but an ion. I am not clear why this is "easier to manipulate" than an atom of a different element, as in models of this kind the nucleus is in effect just a minute point charge – so its composition does not complicate the model in any significant way. If that nuclear charge is +7, say, rather than +1, it makes a difference, certainly (to energy levels), but that does not add any further complexity.

Perhaps the authors chose to retain a hydrogen nucleus because they wanted students to use data from hydrogen spectra? (But if so, this was a little naughty.)

The Balmer series

Again, it did not help that I did not know what the target knowledge set out in the curriculum was.⁴ But, knowing now that hydrogen was the target atom led me to suspect 486 nm and 457 THz radiation linked to lines in the hydrogen spectra – lines in the Balmer series associated with transitions between n=3 and n=2 (656 nm) and n=4 and n=2 (486 nm).

That was all very well, but those transitions referred to the hydogen atom and not to a hydrogen ion. The extra electrons repelling each other in the ion (assuming the ion could be considered stable, which is itself problematic) mean the energy levels (and so the energy gaps; and so the spectral lines) would all be different.

But, if we pretended the ion was stable, and if we pretended that the additional electrons did not change the energy levels (what is what I meant by being somewhat naughty), then the numbers made sense.

A sleight of hand?

Indeed, if we were to adopt the hydrogen atom as the model for our ion, then I sensed I understood why the orbitals were all drawn as circles. In the hydrogen atom, the energy levels are only associated with the principle quantum number. The 2p orbital is at just the same energy level as the 2s orbital. A transition from the N shell to the L shell has the same energy associated with, and so the same frequency of radiation, regardless of whether it involved 2s-4s or 2p-4s or 2s-4p or 2p-4p or 2s-4d or 2p-4d (or indeed 2s-4f or 2p-4f)⁵. That is a considerable simplification, that would make the task much easier for learners.

So, if we are modelling the hydrogen atomic energy levels, we only need to worry about the principle quantum number as there is one level for each value of n. The student diagrams reproduced in the paper suggested all the students understood the reference to an atom with seven energy levels to mean n (that is the principle quantum number related to 'shell') = 1-7.

But an energy level is not an orbital. The n=2 energy level in a hydrogen atom is associated with 4 orbitals, only one of which has spherical symmetry. The n=3 level is associated with 9 orbitals, only one of which has spherical symmetry.

Moreover, this assumption that all the orbtials in a shall are at the same energy level ('degenerate') only applies to a hydrogenic species (H, He⁺, Li²⁺, etc.) – that is, atom-like species with a single electron. The 'atom' (ion) with Romeo and Juliet and Mercutio and the nurse and the rest of the Capulets and Montagues (and possibly some clergy) would not have 2s and 2p orbitals that were degenerate. The presence of interacting electrons (repelling each other, that is, not lusting after each other and "quivering with love") would raze the degeneracy- so the 2s and 2p orbitals would actually be at different energy levels. And so also with 3s and 3p and 3d.

It is not the presence of a hydrogen nucleus which leads to degeneracy between the orbitals within each value of n (each shell), but a system of one nucleus and one electron. So if this 'atom' (ion) had seven energy levels, these would not equate to seven shells of electrons.

The model

So, it looks like the target model was an ion with a hydrogen nucleus, and 7 energy levels occupied by an unspecified number (>4) of electrons, which has the same energy structure and levels as a hydrogen atom, but where each energy level only contained an s orbital.

Models simplify, and in modelling we deliberately leave aside some complexity and nuance. However, we have to balance the gain in simplicity with the loss of authenticity.

A highly charged hydrogen ion could not exist (unless maintained by some very powerful external field)
Atoms have an infinite number of energy levels (but there is no harm in asking learners to ignore most of them for the time being when working on a task)
A hydrogen atom has orbitals of different types (s, p, d…) not all of which are of spherically symmetrical.
The electronic transitions in an ion would not be those found in the related atom, as energy levels of the system depend on the configuration of charges that are interacting. The ion would have many more potential transitions than a single-electron system (such as a hydrogen atom), and these would not have the same energies/frequencies/wavelengths as in the hydrogen atom.
Orbitals do not have edges, and they interpenetrate, so the concept of interatomic orbital distances does not correspond to anything 'realistic' in the orbital model of the atom.

So, the model seems to put aside a lot of the subtlety of the science. But then are these nuanced ideas suitable for treatment with most 15-16 year olds? I would have suspected not (which is why I started from a position of thinking this whole activity was somewhat ambitious), and that may well be why compromises were made in the teaching model adopted in this study.

But perhaps it would be better not to introduce an orbital model until we feel learners are ready to appreciate the quantum jump from concentric orbits to fuzzy, overlapping, infinitely-extended patterns of electronic probability, and the associated complex patterns of energy levels they generate. (But, again, the teaching model used may simply have been reflecting the target knowledge set out in the school curriculum in this particular national context? ⁴)

After all, as the authors had noted,

"Students do not clearly understand the concept of an orbital" (Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024)

Encouraging a new alternative conception?

To take one point. The 486 nm and 457 THz radiation is associated with transitions between n=3 and n=2 (656 nm) and n=4 and n=2 (486 nm) in the hydrogen atom, but NOT in the 'atom' populated with Montagues and Capulets.

Does this matter? After all, the point of the exercise is not to remember these specific values, but to be able to link radiation emitted or absorbed to electronic transitions – so, the particular values of 486 nm and 457 THz are irrelevant. True, but what students are potentially learning here is that the values of energy levels are not affected by the number of electrons repelling each other (here we have an ion with many electrons, but we can simply use the values for a hydrogen atom) – which is an alternative conception.

I also know that this is an alternative conception that learners are likely to readily develop. When students study ionisation energies, and make comparisons between different atoms, they often fail to allow for how the same designation of orbital does not imply an equivalence between differently populated electronic structures.

So, for example, a 2p orbital in an oxygen atom is not only not equivalent to a 2s orbital in the same atom: nor is it equivalent to a 2p orbital in a nitrogen atom. Nor, for that matter, is it entirely equivalent to a 2p orbital in the o^2- anion.

This is not the most serious alternative conception that students can acquire, but given the complexity and challenge of this whole topic area, it might be wise to avoid risk misleading students when possible.

Or am I just being over-critical because I myself found the task too challenging? ☹️

To see through an orbital clearly?

This was an interesting project, and I hope the authors explore the idea further, and perhaps use their experiences with this implementation to further refine the activity. But I am not sure it is helpful in the long term to encourage learners to work with a model that is so constrained that it is likely to encourage new alternative conceptions.

But would that be the case? If the activity is part of a dialogic teaching sequence and the catalyst for engaging students in a discussion of these abstract ideas – a discussion that the teacher carefully steers towards the canonical account – then perhaps the outcome can be more productive. I guess we can only conjecture about this, until someone investigates the long-term effects of learning from the activity.

As usual, it is fair to say "more research is needed".

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Work cited:

Aquilina, G.; Dello Iacono, U.; Gabelli, L.; Picariello, L.; Scettri, G.; Termini, G. "Romeo and Juliet: A Love out of the Shell": Using Storytelling to Address Students' Misconceptions and Promote Modeling Competencies in Science. Education Sciences, 2024, 14, 239. https://doi.org/10.3390/educsci14030239

Justi, R., & Gilbert, J. K. (2000). History and philosophy of science through models: some challenges in the case of 'the atom'. International Journal of Science Education, 22(9), 993-1009.

Taber, K. S. (1998) An alternative conceptual framework from chemistry education, International Journal of Science Education, 20 (5), pp.597-608.
[Download paper]

Taber, K. S. (2002) Conceptualizing quanta – illuminating the ground state of student understanding of atomic orbitals, Chemistry Education: Research and Practice in Europe, 3 (2), pp.145-158 [Download paper]

Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Royal Society of Chemistry.

Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568. [Downlod paper]

Notes

¹ Of course there are many atoms, and indeed many kinds of atoms – so the use of the definite article ('the') is strictly inappropriate. But, this is common usage,

What seems potentially more problematic is the use of the definitive article when the referent is not a specific individual specimen. Chemistry teachers will say things like "the ammonia molecule is pyramidal" when no ammonia molecule is either specified directly or can be inferred to be the case in point from the context. This probably does not seem problematic for the simple reason that it does not matter which ammonia molecule is being referred to: they are all pyramidal. So, statements such as the ammonia molecular is pyramidal; the chlorine atom readily accepts an electron; the K shell is nearest the nucleus; and the iodide ion is a good leaving group; etcetera, will be true regardless.

These statements 'work' in a way that some apparently parallel statements from outside of chemistry would not: the house has a blue door, the man walks with a limp, the baby sneezed all night, the bicycle has squeaky brakes, etcetera. Some houses have blue doors – many do not…So, we should not say 'the house has a blue door' unless we have made it clear which house we are referring to. Yet, we do not need to say which particular water molecule is polar, as they all are (i.e., it may be considered an essential quality of a water molecule). So, the question here is why a teacher would say 'the ammonia molecule is pyramidal' when they are not actually referring to a particular specimen, and the point they are making is actually that (all) ammonia molecules are pyramidal.
Taber, 2019, p.128

And, even if we can refer to 'the carbon atom' when we mean any and all carbon atoms, to simply refer to 'the atom' seems a slight to the periodic table – surely we need to say which (kind of) atom we are modelling? That point certainly proved to be critical in the context of the modelling task discussed in this article!

² The force is symmetrical – the same magnitude force acts on the nucleus and the electron, with each being pulled towards the other. Students commonly have alternative conceptions about this such as thinking the force only acts in one direction (from nucleus to electron) or that the force on the electron is greater.

Read about Newton's third law and common alternative conceptions

³ In the planetary model of the atoms, electrons moved in orbits. In the orbital model we can think of electrons moving about the orbital, and the 'electron density' as a kind of average over time of where they have been. However, it may be more in keeping with the quantum model of the atom to suggest the electrons do not actually move around but rather have probabilities of being located at different points under conditions of observation. (According to a very common interpretation of quantum theory, the notion of an electron being somewhere specific only makes sense at the point of observation.) This is pretty difficult to appreciate (especially for most school-age learners), and I suspect most chemists are happy enough most of the time to think of the electrons moving around in their orbitals.

⁴ Five of the six authors, including the corresponding author, were based in Italy (the other author gave an affiliation based in Canada), so I assume the schools from which the work is reported is in Italy. The paper reports the task set and the student responses in English, so it is not clear if English was used as the language of instruction in the school (this seems unlikely unless this was an International School, but the paper does not report that material has been translated into English).

⁵ 4f orbitals are not usually relevant to atomic structure till we consider cerium, element 58. But the familiar order of filling orbitals as we imagine we are building up atoms (1s < 2s < 2p< 3s < 3p < 4s < 3d < 4p… *) refers to species with more than one electron. For a hydrogen atom, a 4f orbtial is at the same energy level as the 4s orbital, as when occupied the atom's electron, neither would be sheilded at all from the nucleus by other electrons.

(* Ironically, the familiar descriptions of the discrete orbitals designated in this way are based on calculations for a hydrogen atom and do not strictly apply to multi-electron atoms. However the moodel generally works well, and is widely used.)

Ambitious molecules hustle at the World Economic Forum

Keith S. Taber

Composite picture representing people from Kenya, Will.I.Am, Steve Jobs of Apple, former UK minister Rachel Maclean and financial journalist Gillian Tett with a test-tube — The World Economic Forum has been compared to a chemical reaction between disparate molecules. (A group of Kenyans in traditional dress, Apple's co-founder Steve Jobbs, former UK minister Rachel Maclean, musician and activist will.i.am, and journalist Gillian Tett – includes images accessed from Pixabay)

Analogy is a key tool in the teacher's toolbox when 'making the unfamiliar familiar'. Science teachers are often charged with presenting ideas that are abstract and unfamiliar, and sometimes it can help if the teacher can point out how in some ways a seemingly obscure notion is just like something already familiar to the learner. An analogy goes beyond a simile (which simply suggests something is a bit like something else) by offering a sense of how the structure of the 'analogue' maps onto the structure of the 'target'.

Apologies are useful well beyond the classroom. They are used by science journalists reporting on scientific developments, and by authors writing popular science books; and by scientists themselves when explaining their work to the public. But analogies have a more inherent role in science practices: not only being both used in formal scientific accounts written to explain to and persuade other scientists about new ideas, but actually as a tool in scientific discovery as a source of hypotheses.

I have on this site reported a wide range of examples of analogies I have come across for different scientific concepts and phenomena.

Sometimes, however, one comes across an analogy from a scientific concept or phenomenon to something else – rather than the other way round. The logic of using analogies is that the source analogue needs to already be familiar to a reader or listener if it is to help explain something that is novel. So, an analogy between the concept of working memory capacity and fatty acid structure might be used

to explain something about working memory to a chemist – but could also be used
to explain fatty acid structure to a psychologist who already knew about working memory.

So, the use of a scientific idea as the source analogue for some other target idea suggests the user assumes the audience is also familiar with the science. Therefore I deduce that Gillian Tett, journalist at the Financial Times presumably is confident that listeners to BBC Radio 4 will be familiar with the concept of chemical reactions.

Some chemical reactions only proceed at a viable rate on heating. However, an ice bath may be needed to cool some very vigorous reactions to limit their rate. (Image © University of Colorado at Boulder, Department of Chemistry and Biochemistry.)

A cold temperature reaction?

Tett was discussing her experience of the annual World Economic Forum meeting that has just been held in the snow of the Swiss skiing resort of Davos, and suggested that the mixing of various politicians and industry and media and lobbyists had the potential to lead to interesting outcomes – like some kind of chemistry experiment,

"I got jammed into a room with will.i.am, the rapper, who was talking about his views for A.I., and suddenly you've got these activists standing next to somebody from some of the big tech. companies, and a government minister, and a group from Kenya, all talking about whether A.I. could actually be a tool to reduce social inequality, rather than increase it. So, it is a bit like a chemistry experiment where you take all of these ambitious, self-selecting, hustling molecules from around the world, shove them into one test-tube, apply maximum pressure, and force them to collide with each other at close quarters with no sleep, and see what kind of compounds arise."
Gillian Tett talking on the BBC's 'The Week in Westminster'

An experiment (by definition) has uncertain results, and Tett used the analogue of the chemistry experiment to imply that the diverse mixes of people collected together at Davos could lead to unexpected outcomes – just like mixing a diverse range of substances might. Tett saw the way such diverse groups become 'jammed' into rooms in arbitrary combinations as they make their ways around the meeting as akin to increasing the pressure of a reaction mixture of arbitrary reagents. This reflects something of the popular media notion of dangerous 'scientific experiments', as carried out by mad scientists in their basements. Real scientific experiments are carried out in carefully controlled conditions to test specific hypothesis. The outcome is uncertain, but the composition of the reaction mixture is carefully chosen with some specific product(s) in mind.

The figure below represents the mapping between the analogue (a rather undisciplined chemistry experiment) and the reaction conditions experienced by delegates in the melting pot of Davos.

Figure showing analogy between World Economic Forum and a chemistry experiment — the World Economic Forum at Davos is like a chemical experiment because…

Inspection of my figure suggests some indiscipline in the analogy. The reaction conditions are to "apply maximum pressure, and force [the molecules] to collide with each other at close quarters with no sleep". Now this phrasing seems to shift mid-sentence,

from the analogue (the chemical experiment:"apply maximum pressure, and force [the molecules] to collide with each other")
to the target (being jammed into a room at the conference: "at close quarters with no sleep").

One explanation might be that Gillian Tett is not very good at thinking though analogies. Another might be that, as she was being interviewed for the radio, she was composing the analogy off-the-cut without time to reflect and review and revise…

Either of those options could be correct, but I suspect this shift offered some ambiguity that was deliberately introduced rhetorically to increase the impact of the analogy on a listener. Tatt ('an anthropologist by training' and Provost of King's College, Cambridge) had described the molecules anthropomorphically: just as molecules do not sleep,

they cannot be 'ambitious', as this is a human characteristic;
they are not sentient agents, so cannot be 'self-selecting'; and
nor can they 'hustle' as they have no control over their movements.

But the journalists, politicians, activists and industrialists can be described in these terms, reinforcing the mapping between the molecules and the Davos delegates. So, I suspect that whilst this disrupted the strict mapping of the analogy, it reinforced the metaphorical way in which Tett wanted to convey the sense that the ways in which the Davos meeting offered 'experimental' mixing of the reacting groups had the potential to produce novel syntheses.

Read about examples of different science analogies

Read about making the unfamiliar familiar

Read about anthropomorphism in learners' thinking

Read about examples of anthropomorphism in public discussion of science

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Surface tension is due to everybody trying to get into the water

Surely you are joking, Prof. Feynman? ¹

Keith S. Taber

Photo of Richard Feynman, taken in 1984 © Tamiko Thiel (accessed from Wikipedia and shared under Creative Commons Attribution-Share Alike 3.0 Unported)

The late, great, Richard Feynman

Richard Feynman was special. Any one who wins the Nobel prize has to be pretty special, but physics laureate Feynman was even more remarkable as he was an exceptionally high achieving research physicist also known for his…teaching. No one gets a Nobel for being a good teacher, and it is often considered in Academia that teaching (that is, if one tries to give teaching the time and energy required to do it well – as students deserve) distracts from research to such an extent that it is rare to excel in both.

Feynman had something a lot of scientists do not not: great charisma. (That is no insult to fellow scientists – most plumbers and greengrocers and bus drivers and accountants and hairdressers do not – that is what makes it notable). He might be considered the Albert Einstein of the second half of the twentieth century, and because of that timescale we are lucky to have quality recordings of him talking and teaching in a way that could not have happened with previous generations. (A great shame in many cases: if perhaps a blessing with some – Isaac Newton's lectures were apparently avoided by most of his own students.)

Like many people, I find Feynman bewitching – he had a sparkle about him – almost a permanent mischievous twinkle in the eye – and an ability to somehow express the excitement of science (of working out why things are as they are) whilst being able to talk in ways that could be understood by people that lacked his expertise. That is perhaps one trait of a great teacher – being able to talk at the level of the audience, despite personally understanding at a higher, more complex and subtle, level.

That is by way of preamble – as I want to consider an explanation Feynman once offered of surface tension.

Screenshot of Richard Feynman explaining why water forms into drops.

Why does it rain in drops?

The extract I am discussing is taken from a 1983 BBC series of short episodes in a series called 'Fun to Imagine'. Although, at the time of writing, the episodes are "not currently available" from the BBC site, there is a compilation on YouTube. One of the topics Feynman discusses is the origin of surface tension – although he only introduces the technical term after explaining the phenomenon that water forms into droplets,

"you see a little drop of water, a tiny drop
And the atoms [sic, molecules] attract each other, they like to be next to each other
They want as many partners as they can get
Now the guys that are at the surface have only partners on one side
here, in the air on the other side, so they're trying to get in
And you can imagine…this teeming people, all moving very fast
all trying to have as many partners as possible and the guys at the edge are very unhappy and nervous and they keep pounding in
trying to get in, and that makes it a tight ball instead of a flat
and that's what, you know, surface tension
When you realise when you see how sometimes a water drop sits like this on a table then you start to imagine why it's like that
because everybody is trying to get into the water"
Richard Feynman speaking in 1983

Is this a good explanation?

Well, we might suggest Feynman makes a schoolchild error – water is not an atomic substance, but molecular. It does not contain discrete atoms, so he should be referring to the molecules attracting each other. But I do not think this is an error in the sense that Feynman was mistaken, simply that although the distinction is of great importance in chemistry, physicists sometimes use the term 'atom' generically to refer to the individual particles in a gas, for example. That might be unhelpful to a secondary school student studying for examinations, but if Feynman thought of his television audience for the recording as lay people, the general public, then perhaps the distinction between atoms (arguably a more familiar term in everyday discourse) and molecules would be considered an unhelpful detail? I am certainly prepared to give him that. I think it was the wrong choice, but not that Feynman was in error.

But what about the overall argument here. The 'atoms' want to have partners all around them ² so they try to get inside the volume of the liquid. The overall effect of everyone, including these guys at the edge, trying to get inside the water is that it forms a sphere-like shape: "a tight ball instead of [something more] flat". Is that a convincing explanation – and is it a valid one?

What makes for a good explanation?

If anything is central to both science and science teaching, it is explanation.

"Explanation would seem to be central to the essence of science. A naïve view might claim that science discovers knowledge about the World, although it might be more accurate to suggest that science creates knowledge through the development of theories. The theories are used in turn to understand, predict and sometimes control the world, and in these activities, scientific explanations play the key role. We might consider theories and models to be the resources of science, but explanations to be the active processes through which theory is applied to contexts of interest…

An explanation is an answer to a 'why' question: but that in itself neither makes for a good explanation, nor for a scientific one. There is no simple answer to what does count as a good explanation, in science or elsewhere. Explanations have audiences, and to some extent, a good explanation is one that satisfied its audience – in other words it meets the explainee's purpose in seeking an explanation. Additionally, it has been known since at least Aristotle's time that we can talk of different kinds of causes, which suggests that many 'why questions' might have different types of acceptable responses, depending on the type of cause being sought."
Taber, 2007, p.159 [Download the chapter]

That passage is taken from a chapter where I described some activities used with secondary school students to help teach them about the nature of scientific explanation. (Read about the classroom activities here.) In that context, working with learners who were about 14 years of age, students were told that a good scientific explanation would be logical, and would draw upon scientific theory,

"pupils were told that scientific explanations needed to take into account logic and theory, i.e., that the explanation needs to be rational, and the explanation needs to draw upon accepted scientific ideas. As the notion of 'theory' is itself known to be difficult for students, they were also told that scientific theories are ideas about the world which are well supported by evidence; are internally consistent; and which usually fit with other accepted theories."
Taber, 2007, p.159 [Download the chapter]

Feynman's explanation is logical (if incomplete)

In that regard, Feynman's explanation can be considered logical, even if it omits (i.e., he takes as assumed) an important step* that is needed to explain the (approximately) spherical shape of the water drop.

If water quanticles (let's leave aside whether they are atoms or molecules) want to have many partners ², and so try to get inside the volume, then we can understand* that the water drop will tend to the smallest surface area possible, so as few quanticles end up at the surface (with the tenuous air, rather than congregating water partners, on one side) where they will be nervous, and as many quanticles as possible are in the interior of the drop where they will be happy.

* The missing step is to state that a spherical drop will have a smaller surface area than any other shape with the same volume and so fewest quanticles at the surface. Perhaps Feynman assumed everyone would know/see that. Probably there is no such thing as a totally complete explanation.

So, is this a good explanation?

Explanations can have different purposes. Scientific explanations allow us to make effective predictions (and so often to control situations – the application of science through technology). But, in everyday life, explanations have a more subjective purpose ("explanations have audiences, and to some extent, a good explanation is one that satisfied its audience").

If, as a result of hearing Feynman's explanation, the viewers of the BBC televison programme

felt they now understood why sphere-like drops of water form, and
considered they had made sense of some science, and so
appreciated the value of science in explaining everyday phenomena,

then perhaps the explanation achieved its purpose?

Was Feynman's explanation scientific?

Of course, if I am being my usual pedantic self, I could point out that although Feynman's explanation was logical, that does not make it scientific unless it also drew upon accepted scientific principles. It was logical because the explicandum (what was to be explained – here, the drop shape) followed from the premise (i.e., if water quanticles want to have many partners, and act accordingly, then…)

But, in science, quanticles are not understood as sentient actors, but as inanimate entities that are not (and cannot be) aware of their situation and cannot act deliberately to work towards personal goals. Therefore, no matter how convincing someone may have found this explanation, it does not qualify as a scientific explanation as it is not based on accepted scientific principles (…or at least, not directly).

An anthropomorphic explanation

Feynman's explanation uses anthropomorphism, which from a scientific perspective makes it a pseudo-explanation. A pseudo-explanation takes the form of an explanation in that it is presented as if an answer to a why question, but does meet the requirements for a formal explanation (e.g., it does "not logically fit the phenomenon to be explained into a wider conceptual scheme", Taber & Watts, 2000.)

There are various kinds of pseudo-explanations such as tautology (circular explanations that rely on the conclusions as premises) and simply offering a label for the explicandum (e.g., water absorbs a lot of heat for a small change in its temperature because it has a high heat capacity – this is a kind of disguised tautology, as a 'high heat capacity' is a way of characterising something that absorbs a lot of heat for a small change in its temperature).

Read about pseudo-explanations

Anthropomorphism explains by assuming that the entities involved can be considered to be like people, and, so, to be sentient, have feelings and opinions and preferences, and be able to plan and carry out actions that are intended to being about desired consequences.

It relies on an analogy that may not be appropriate:

if people were in a situation like this, they are likely to behave in a certain way
if we treat these entities as if they were people then we might expect them to behave as people would, therefore…

It is an open question to what extent we can assume animals (chimpanzees, dogs, birds, etc.) can be considered to share aspects of human-like experiences, emotions, thoughts, etcetera. Perhaps it is reasonable to suggest a dog can be sad or a chimp can be jealous. It may not be stretching credibility to suggest that members of some species of animals want to be in large groups, like to be in large groups, and perhaps may even get nervous when isolated? However, it stretches credibility when we are told that viruses are clever or that a bacterium can be happy.

And, there is a pretty strong scientific consensus that at the level of individual molecules there is no possibility of emotions, opinions, desires, thoughts, or deliberate actions. Atoms do not want to fill their electron shells, and genes cannot be selfish, except in a figurative sense.

Read about anthropomorphism

So, in order to accept Feynman's explanation as valid, we would have to assume that the quanticles in water, water molecules,

like to be next to each other
want as many partners as they can get ²
can be unhappy and nervous
try to have as many partners as possible ²
try to get into the inside of the volume

So, to find this explanation convincing, we have to accept (contrary to science) that something like a water molecule is able to

have desires and preferences,
be aware of the extent to which is current situation matches its preferences, and,
deliberately act to bring about desired outcomes

[Feynman does not explicitly state that the quanticles know about their situation (point 2), but clearly this is implied as otherwise they would have no reason to be nervous and unhappy, nor to act to bring about change.]

These requirements are clearly not met. A being with a central nervous system as complex as a human can meet these requirements, but there is no conceivable mechanism by which molecules can be considered sentient, or to be deliberate agents in the world.

So, even if Feynman's explanation of surface tension satisfies viewers of the recording (i.e., is is subjectively an effective explanation) it fails as an objective, scientific, explanation. Feynman may indeed have been a 'genius' (Gleick, 1994), and a great physicist, but his explanation here is invalid and simply fails as good science.

Now a reader may suspect I have gone after a 'straw man' target here. Surely, Feynman was speaking figuratively, and not literally. Of course he was, but figurative language cannot support a logical explanation, except through an analogy we suspect to hold.

Consider the following hypothetical claim and two possible consequences if the claim was true

Claim	Consequence 1	Consequence 2
"I managed to get tickets for Toyah and Fripp's sold out concert in Bury St Edmunds, and these tickets are gold dust."	"I could sell these tickets at quite a mark up"	"I could put a sample of these tickets in a mass spectrometer and would find they had an atomic mass of 197."

If the claim was literally true, then consequence 2 would follow. But of course, it is meant as a figurative claim, where 'gold dust' is a metaphor for something of high value because it is rare. So, actually consequence 1 might follow, but not consequence 2.

In the same way, if water particles do not have likes, and do not try to do things, Fenyman's argument seems to fall apart…

A teaching model?

Now I would not presume to know better than Richard Feynman, and I am pretty sure (i.e., about as certain as I can be of anything) that Feynman would not have fallen into the mistake of thinking that atoms or molecules actually act like humans and want things, or try to do things. He surely knew this was not a scientific explanation, but he clearly thought this was a useful way of explaining (to his audience) why water forms into a drop.

Now, I suggested above that Feynman's narrative account of the origin of surface tension "is not based on accepted scientific principles (…or at least, not directly)". But near the outset of this account Feynman states that the water particles "attract each other":

"the [molecules] attract each other, they like to be next to each other"

Feynman was not only a researcher, but a teacher, and teachers use teaching models. I think this is what Feynman is doing here:

"[according to science] the [molecules] attract each other [and we can think of this as if] they like to be next to each other"

Affinity in the sense of human experience is used as a kind of analogy for the affinity between water molecules (which leads to hydrogen bonding and dipole-dipole interactions). Once we model inter-molecular forces as being like attractions between people, we can extend the analogy in terms of how people feel when they do not get what they want, and how they respond by acting in ways that they hope will get them what they want.

Looked at this way, Feynman is doing something that good teachers often do when they judge a scientific model is too abstract, sophisticated, complex, subtle, for their audience; they simplify by substituting a teaching model which represents the scientific model in terms more familiar and accessible to the learners.

Read about making the unfamiliar familiar

From this perspective, Feynman's explanation may not have been a valid scientific explanation, but we might ask if it was an effective intermediate explanation set out in terms of a teaching model. That is, perhaps Feynman's explanation may have satisfied viewers, and also potentially acted as a possible foundation for building up to a more technical, scientifically acceptable explanation.

Teachers and other science communicators often use anthropomorphism as a way of offering accounts of complex scientific topics that will appeal and make sense to learners of a public audience.

Read about anthropomorphism in accounts of science

This can be effective to the extent that it engages learners, leaves the audience with a subjective sense of making sense of the science, and provides accounts that are often remembered later.

Of course that is not so helpful if the audience is studying a science course, and think they have learnt an account which will get them credit in formal examinations! I know from my own teaching career that learners often find anthropomorphic explanations readily come to mind, even when then they have been taught more technical accounts they are expected to apply when assessed.

In public science communication, then, anthropomorphic accounts may be valuable in offering people some sense of the science. But in formal education we need to be careful as even if anthropomorphism offers a useful way of getting learners familiar with some abstract topic (what might be called 'weak' anthropomorphism: Taber & Watts, 1996), we need to avoid them learning and committing to that metaphoric 'social' account thinking it is a valid scientific account ('strong' anthropomorphism).

Mapping Feynman's explanation

If we see Feynman as offering an analogy as a teaching model then we might seek to 'translate' his terms into more scientific concepts. He tells us that attraction is 'liking', and we can perhaps think of 'wanting' and being 'nervous' as indicating a higher (excited) energy state, 'pounding' as being subject to unbalanced forces, and 'trying to get in' as tending to evolving toward a lower energy configuration. At least, someone who already understood the scientific account could suggest such mappings. It seems unlikely any one who did not appreciate the science already could interpret it that way without a knowing and careful guide.

And like all anthropomorphic explanations, it 'suffers' from the very quality that it offers a narrative which is likely to be more easily understood, better related to, and more readily recalled, than the scientific account. This is why I have very mixed feelings about the use of anthropomorphism in formal science teaching, as even when it (a) does a great job of engaging learners and offering them some level of understanding, this may be at the cost of (b) offering an account which many students will find it hard to later let go of and progress beyond.

Screenshot of Richard Feynman explaining why water forms into drops.

As a good teacher, Feynman would know to pitch his teaching for particular audiences depending on their likely level of background knowledge. The explanation discussed here was not how Feynman taught about surface tension in his undergraduate classes at the California Institute of Technology (Feynman, Leighton & Sands, 1963). We can imagine that had he told students at Caltech that water formed into spherical drops because all the molecular guys are trying to get into the water, he might indeed had heard the retort: Surely you are joking, Prof. Feynman?¹

Work cited:

Feynman, R. P., Leighton, R. B., & Sands, M. (Eds.). (1963). The Feynman Lectures on Physics (3 Volumes). Addison-Wesley Publishing Company.
Gleick, J. (1994) Genius: Richard Feynman and Modern Physics. Abacus.
Taber, K. S. (2007). Choice for the gifted: lessons from teaching about scientific explanations. In K. S. Taber (Ed.), Science Education for Gifted Learners (pp.158-171). London: Routledge. [Download the chapter]
Taber, K. S. (2020). Foundations for Teaching Chemistry: Chemical knowledge for teaching. Routledge.
Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568. Download the authors' manuscript version [Download the paper].
Taber, K. S. & Watts, M. (2000) Learners' explanations for chemical phenomena, Chemistry Education: Research and Practice in Europe, 1 (3), pp.329-353. [Free access]

Notes:

¹ My subtitle is a reference to the book 'Surely you're Joking Mr Feynman: Adventures of a Curious Character' in which Feynman tells anecdotes from his life.

² Water was perhaps a poor example to choose as there is extensive hydrogen bonding in liquid water,

"I suspect even some experienced chemists may underestimate the extent of hydrogen bonding in water. According to one source…, in liquid water at the freezing point, the typical water molecule is at any time bonded by three or four hydrogen bonds – compared with the four bonds in the solid ice structure."
Taber, 2020, p.98

So, in Feynman's analogy, a water molecules does not become happy (lower energy state) when it is surrounded by as many other water molecules as possible, but when it is aligned with 3 or 4 other molecules to hydrogen bond, if only transiently. Without the hydrogen bonding, the drop would still be approximately spherical, but it would be smaller and denser as the molecules could get even closer together, but it would evaporate away more readily.

Disease and immunity – a biological myth

Does the medieval notion of the human body as a microcosm of the wider Cosmos – in which is played out an eternal battle between good and evil – still influence our thinking?

Keith S. Taber wants to tell you a story

Are you sitting comfortably?

Good, then I will begin.

Once upon a time there was an evil microbe. The evil microbe wanted to harm a human being called Catherine, and found ways for his vast army of troops to enter Catherine's body and damage her tissues.
Luckily, unbeknown to the evil microbe, Catherine was prepared to deal with invaders – she had a well-organised defence force staffed by a variety of large battalions, including some units of specialist troops equipped with the latest anti-microbe weapons.
There were many skirmishes, and then a series of fierce battles in various strategic locations – and some of these battles raged for days and days, with heavy losses on both sides. No prisoners were taken alive. Many of Catherine's troops died, but knowing they had sacrificed themselves for the higher cause of her well-being.
But, in the end, all of the evil microbe's remaining troops were repelled and the war was won by the plucky defenders. There was much rejoicing among the victorious army. The defence ministry made good records of the campaign to be referred to in case of any future invasions, and the surviving soldiers would long tell their stories of ferocious battles and the bravery of their fallen comrades in defeating the wicked intruders.
Catherine recovered her health, and lived happily ever after.

There is a myth, indeed, perhaps even a fairy story, that is commonly told about microbial disease and immunity. Disease micro-organisms are 'invaders' and immune cells are 'defenders' and they engage in something akin to warfare. This is figurative language, but has become so commonly used in science discourse that we might be excused for forgetting this is just a stylistic feature of science communication – and so slip into habitually thinking in the terms that disease actually is a war between invading microbes and the patient's immune system.

Immunity is often presented through a narrative based around a fight between opposed sentient agents. (Images by Clker-Free-Vector-Images and OpenClipart-Vectors from Pixabay.)

Actually this is an analogy: the immune response to infection is in some ways analogous to a war (but as with any analogy, only in some ways, not others). As long as we keep in mind this is an analogy, then it can be a useful trope for talking and thinking about infectious disease. But, if we lose sight of this and treat such descriptions as scientific accounts, then there is a danger: the myth undermines core biological principles, such that the analogy only works if we treat biological entities in ways that are contrary to a basic commitment of modern science.

In this article I am going to discuss a particular, extensive, use of the disease-as-war myth in a popular science book (Carver, 2017), and consider both the value, and risks, of adopting such a biological fairy-tale.

Your immune system comprises a vast army of brave and selfless soldiers seeking to protect you from intruders looking to do you harm: an immune response is a microcosm of the universal fight between good and evil?
A myth is a story that has broad cultural currency and offers meaning to a social group, usually involving supernatural entities (demons, superhuman heroes, figures with powerful magic), but which is not literally true.

Carver's account of the immune system

I recently read 'Immune: How your body defends and protects you' (henceforth, 'Immune') by Catherine Carver. Now this is clearly a book that falls in the genre 'popular science'. That is, it has been written for a general audience, and is not meant as a book for experts, or a textbook to support formal study. The publishers, Bloomsbury, appropriately describe Carver as a 'seasoned science communicator'. (Appropriately, as metaphorical dining features strongly in the book as well.)

Carver uses a lot of contractions ("aren't", "couldn't", "doesn't", "don't", "isn't", "it's", "there's", "they're", "we've", "what's", "who'd", "wouldn't", "you'd") to make her writing seem informal, and she seems to make a special effort to use metaphor and simile and to offer readers vivid scenes they can visualise. She offers memorable, and often humorous, images to readers. A few examples offer an impression of this:

"…the skin cells…migrate through the four layers of the epidermis, changing their appearance like tiny chameleons…"
"Parietal cells dotted around the surface of the stomach are equipped with proton pumps, which are like tiny merry-go-rounds for ions."
"a process called 'opsonisation' make consuming the bacterial more appealing to neutrophils, much like sprinkling tiny chocolate chips on a bacterial cookie."
"The Kupffer cells hang around like spiders on the walls of the blood vessels…"

In places I wondered if sometimes Carver pushed this too far, and the figurative comparisons might start to obscure the underlying core text…

"…the neutrophil…defines cool. It's the James Dean of the immune system; it lives fast, dies young and looks good in sunglasses."
Carver, 2017, p.7

"The magnificence of the placenta is that it's like the most efficient fast-food joint in the world combined with a communications platform that makes social media seem like a blind carrier pigeon, and a security system so sophisticated that James Bond would sell his own granny to the Russians just to get to play with it for five minutes."
Carver, 2017, p.113

When meeting phrases such as these I found myself thinking about the metaphors rather than what they represented. My over-literal (okay, pedantic) mind was struggling somewhat to make sense of a neutrophil in (albeit, metaphoric) sunglasses, and I was not really sure that James Bond would ever sell out to the Russians (treachery being one of the few major character faults he does not seem to be afflicted by) or be too bothered about playing with a security system (his key drives seem focused elsewhere)…

…but then this is a book about a very complex subject being presented for an audience that could not be assumed to have anything beyond the most general vague prior knowledge of the immune system. As any teacher knows, the learner's prior knowledge is critical in their making sense of teaching, and so offering a technically correct account in formal language would be pointless if the learner (or, here, reader) is not equipped to engage at that level.

'Immune' is a fascinating and entertaining read, and covers so much detailed ground that I suspect many people reading this book would would not have stuck with something drier that avoided a heavy use of figurative language. Even though I am (as a former school science teacher *) probably not in the core intended audience for the book, I still found it very informative – with much I had not come across before. Carver is a natural sciences graduate from Cambridge, and a medical doctor, so she is well placed to write about this topic.

Catherine Carver's account of the immune system is written to engage a popular readership and draws heavily on the disease-as-war analogy.

My intention here is not to offer a detailed review or critique of the book, but to explore its use of metaphors, and especially the common disease-as-war theme (Carver draws on this extensively as a main organising theme for the book, so it offers an excellent exemplar of this trope) – and discuss the role of the figurative language in science communication, and its potential for subtly misleading readers about some basic scientific notions.

The analogy

The central analogy of 'Immune' is clear in an early passage, where Carver tells us about the neutrophil,

"…this cell can capture bubonic plague in a web of its own DNA, spew out enzymes to digest anthrax and die in a kamikaze blaze of microbe-massacring glory. The neutrophil is a key soldier in an eternal war between our bodies and the legions of bacteria, viruses, fungi and parasites that surround us. From having sex to cleaning the kitchen sink, everything we do exposes us to millions of potential invaders. Yet we are safe. Most of the time these invaders' attempts are thwarted. This is because the human body is like an exceedingly well-fortified castle, defended by billions of soldiers. Some live for less than a day, others remember battles for years, but all are essential for protecting us. This is the hidden army that we all have inside of us…"
Carver, 2017, p.7

Phew – there is already a lot going on there. In terms of the war analogy:

We are in a perpetual war with (certain types) of microbes and other organisms
The enemy is legion (i.e., has vast armies)
These enemies will invade us
The body is like a well-protected fort
We have a vast army to defend us
There will be battles between forces from the two sides
Some of our soldiers carry out suicide (kamikaze) missions
Our defenders will massacre microbes
We (usually) win the battles – our defences keep us safe

Some of these specific examples can be considered as metaphors or similes in they own right when they stand alone, but collectively they fit under an all-encompassing analogy of disease-as-war.

Read about analogies in science

Read about metaphors in science

Read about similes in science

But this is just an opening salvo, so to speak. Reading on, one finds many more references to the 'war' (see Boxes 1 and 2 below).

The 'combatants' and their features are described in such terms as army, arsenals, assassins, band of rebels, booby-traps, border guards, border patrol force, commanders, defenders, fighting force, grand high inquisitors, hardened survivor, invaders, lines of defence, muscled henchman, ninjas, soldiers, terminators, trigger-happy, warriors, and weapons.

Disease and immune processes and related events are described in terms such as alliance, armoury, assassination campaign, assault, assault courses, attack, battlefield, bashing, battles, boot camp, border control, calling up soldiers, chemical warfare, cloaking device, craft bespoke weaponry, decimated, dirty bomb, disables docking stations, double-pronged attack, exploding, expose to a severe threat, fight back, fighting on fronts, friendly fire, go on the rampage, hand grenades, heat-seeking missiles, hold the fort, hostile welcome, instant assault , kamikaze, killer payload, massacring, patrolling forces, pulling a pin on a grenade, R & R [military slang for 'rest and recuperation'], reinforcing, security fence, self-destruct, shore up defences, slaughters/slaughtering, smoke signals, standing down, suicidal missions, Swiss army knife, taking on a vast army on its home turf, throwing dynamite, time bomb, toxic cloud, training camp, training ground, trip the self-destruct switch, Trojan horse, victories, war, and wipe out the invader.

Microbes and cells as agents

A feature of the analogue is that war is something undertaken by armies of soldiers, that are considered as having some level of agency. The solder is issued with orders, but carries them out by autonomous decision-making informed by training as well as by conscience (a soldier should refuse to obey an illegal order, such as to deliberately kill civilians or enemy combatants who have surrendered). Soldiers know why they are fighting, and usually buy into at least the immediate objectives of the current engagement (objectives which generally offer a more favourable outcome for them than for the enemy soldiers). A soldier, then, has objectives to be achieved working towards a shared overall aim; purposes that (are considered to) justify the actions taken; and indeed takes deliberate actions intended to bring out preferred outcomes. Sometimes soldiers may make choices they know increase risks to themselves if they consider this is justified for the higher 'good'. These are moral judgements and actions in the sense of being informed by ethical values.

An extensive range of terminology related to conflict is used to describe aspects of disease and the immune response to infection. (Image sources: iXimus [virus], OpenClipart-Vectors [cell], Tumisu [solders in 'Raising the Flag on Iwo Jima'-like poses], from Pixabay.)

Now, I would argue that none of this applies to either disease organisms nor components of a human immune system. Neither a bacterium nor an immune cell know they are in a war; neither have personal, individual or shared, objectives; and neither make deliberate choices about actions to take in the hope they will lead to particular outcomes. No cell knowingly puts itself at risk because it feels a sacrifice is justified for the benefit of its 'comrades' or the organism it is part of.

So, all of this might be considered part of what is called the 'negative analogy', that is, where the analogy breaks down because the target system (disease processes and immune responses) no longer maps onto the analogue (a war). Perhaps this should be very obvious to anyone reading about the immune system? At least, perhaps scientists might assume this would be very obvious to anyone reading about the immune system?

Now, if we are considering the comparison that an immune response is something like a nation's defence forces defending its borders against invaders, we could simply note that this is just a comparison but one where the armies of each side are like complex robotic automatons pre-programmed to carry out certain actions when detecting certain indicators: rather than being like actual soldiers who can think for themselves, and have strategic goals, and can rationally choose actions intended to bring about desired outcomes and avoid undesired ones. (A recent television advertising campaign video looking to recruit for the British Army made an explicit claim that the modern, high-tech, Army could not make do with robots, and needed real autonomous people on the battlefield.)

However, an account that relies too heavily on the analogy might be in danger of adopting language which is highly suggestive that these armies of microbes and immune cells are indeed like human soldiers. I think Carver's book offers a good deal of such language. Some of this language has already been cited.

Immune cells do not commit kamikaze

Consider a neutrophil that might die in a kamikaze blaze of microbe-massacring glory. Kamikaze refers to the actions of Japanese pilots who flew their planes into enemy warships because they believed that, although they would surely die and their planes be lost, this could ensure severe damage to a more valuable enemy resource – where the loss of their own lives was justified by allowing them to remain at the plane's controls until the collision to seek to do maximum damage. Whatever we think of war in general, or the Kamikazi tactics in particular, the use of this term alludes to complex, deliberate, human behaviour.

Immune cells do not carry out massacres

And the use of the term massacre is also loaded. It does not simply mean to kill, or even to kill extensively. For example, the Jallianwala Bagh massacre, or Amritsar massacre, is called a massacre because (British) soldiers with guns deliberately fired at, with intent to kill or seriously injure, a crowd of unarmed Indians who were in their own country, peacefully protesting about British imperial policies. The British commanders acted to ensure the protesters could not easily escape the location before ordering soldiers to fire, and shooting continued despite the crowd trying to flee and escape the gunfire. Less people died in the Peterloo Massacre (1819) but it is historically noteworthy because it represented British troops deliberately attacking British demonstrators seeking political reform, not in some far away 'corner of Empire', but in Manchester.

Amritsar occurred a little over a century ago (before modern, post-Nurenmberg, notions of the legality of military action and the responsibility of soldiers to not always follow orders blindly), but there are plenty of more recent examples where the term 'massacre' is used, such as the violent clearing of protesters in Tiananmen Square in 1989 and the Bogside 'Bloody Sunday' massacre in 1972 (referenced in the title of the U2 song, 'Sunday Bloody Sunday'). In these examples there is seen to be an unnecessary and excessive use of force against people who are not equipped to fight back, and who are not shown mercy when they wish to avoid or leave the confrontation.

'Monument in Memory of Chinese from Tiananmen in Wrocław, Poland' commemorating the massacre of 4th June 1989 when (at least) hundreds were killed in Beijing after sections of the People's Liberation Army were ordered to clear protesters from public places (Masur, Public domain, via Wikimedia Commons)

The term massacre loses its meaning without this sense of being an excessively immoral act – and surely can only apply to an action carried out by 'moral agents' – agents who deliberately act when they should be aware the action cannot be morally justified, and where they can reasonably see the likely outcomes. (Of course, it is more complicated that this, in particular as a soldier has orders as well as a conscience – but that only makes the automatic responses of immune cells towards pathogens even less deserving of being called a massacre.)

The term moral agent does not mean someone who necessarily behaves morally, but rather someone who is able to behave morally (or immorally) because they can make informed judgements about what is right and wrong – they can consider the likely consequence of their actions in terms of a system of values. An occupied building that collapses does harm to people, but cannot be held morally responsible for its 'behaviour' in the way a concentration camp guard or a sniper can be. A fox that takes a farmer's chickens has no conception of farming, or livestock, or ownership, or of the chickens as sentient beings that will experience the episode from a different perspective, but just acts instinctively to access food. Microbes and cells are like the building or the fox, not the guard or the sniper, in this respect.

Moreover, in the analogue, the massacred are also moral agents: human beings, with families, and aspirations for their futures, and the potential for making unique contributions to society… I am not convinced that bacteria or microbes are the kinds of entities that can be massacred.

Anthropomorphic references

Carver then writes about the immune system, or its various components, as well as various microbes and other pathogenic organisms, as though they are sentient, deliberative agents acting in the world with purposes. After all, wars are a purely human phenomenon.¹ Wars involve people: people with human desires, motives, feelings, emotions, cunning, bravery (or not), aims and motivations.

Anthropomorphism is describing non-human entities as if they are people. Anthropomorphism is a common trope in science teaching (and science communication) but learners may come to adopt anthropomorphic explanations (e.g., the atom wants…) as if they are scientific accounts (Taber & Watts, 1996).

Read about anthropomorphism

Bacteria, body cells and the like are not these kinds of entities, but can be described figuratively as though they are. Consider how,

"Some bacteria are wise to this and use iron depletion as an indicator that they are inside an animal. Other bacteria have developed their own powerful iron-binding molecules called 'siderophores' which are designed to snatch the iron from the jaws of lactoferrin. Perhaps an even smarter strategy is just to opt out of the iron wars altogether…

…tear lipocalin, whose neat structure includes a pocket for binding a multitude of molecules. This clever pocket allows tear lipocalin to bind the bacterial siderophores…neutralising the bacterium's ability to steal iron from us…"
Carver, 2017, pp.20-21

Of course, bacteria are only 'wise' metaphorically, and they only 'develop' and 'design' molecules metaphorically, and they only adopt 'smarter strategies' or can 'opt out' of activities metaphorically – and as long as the reader appreciates this is all figurative language it is unproblematic. But, when faced with multiple, and sometimes extended, passages seeming to imply wise and clever bacteria developing tools and strategies, could the reader lose sight of this (and, if so, does that matter?)

If bacteria are not really clever, nor are pockets (or 'pockets' – surely this is a metaphor, as actual pockets are designed features not evolved ones). Stealing is the deliberate taking of something one knows is owned by someone else. Bacteria may acquire iron from us, but (like the fox) they do not steal as they have no notion of ownership and property rights, nor indeed, I suggest, any awareness that those environments from which they acquire the iron are considered by them[our]selves as 'us'.

That is, there is an asymmetrical relationship here: humans may be aware of the bacteria we interact with (although this has been so only very recently in historical terms) but it would be stretching credibility to think the bacteria have any awareness – even assuming they have ANY awareness in the way we usually use the term – of us as discrete organisms. So, the sense in which they "use iron depletion as an indicator that they are inside an animal" cannot encompass a deliberate use of an indicator, nor any inference they are inside an animal. There is simply a purely automatic, evolved, process that responds to environmental cues.

I have referred in other articles posted here to examples of such anthropromorphic language in public discourse being presented apparently in the form of explanations: e.g.,

"Y-negative cells cause an immune evasive environment in the tumour, and that, if you will, paralyses, the T cells, and exhausts them, makes them tired…"

"first responder cells. In humans they would be macrophages, and neutrophils and monocytes among them. These cells usually rush to the site of an injury, or an infection, and they try to kill the pathogen"

"viruses might actually try to…hide…the microbes did not just accept defeat"

"we are entering Autumn and Winter, something that COVID and other viruses, you know, usually like…when it gets darker, it gets colder, the virus likes that, the flu virus likes that"

My focus here is Catherine Carver's book, but it is worth bearing in mind that even respectable scientific journals sometimes publish work describing viruses in such terms as 'smart', 'nasty', 'sneaky' – and, especially it seems, 'clever' (see 'So who's not a clever little virus then?'). So, Carver is by no means an outlier or maverick in using these devices.

'Immune' is embellished throughout with this kind of language – language that suggests that parasites, microbes, body cells, or sometimes even molecules:

act as agents that are aware of their roles and/or purposes;
do things deliberately to meet objectives;
have preferences and tastes.

The problem is, that although this is all metaphorical, as humans we readily interpret information in terms of our own experiences, so a scientific reading of a figurative text may requires us to consciously interrogate the metaphors and re-interpret the language. Historians of chemistry will be well aware of the challenge from trying to make sense of alchemical texts which were often deliberately obscured by describing substances and processes in metaphoric language (such as when the green lion covers the Sun). Science communicators who adopt extensive metaphors would do well to keep in mind that they can obscure as well as clarify.

For example, Carver writes:

"…the key to a game of hide and seek is elementary: pick the best hiding place. In the human body, the best places to hide are those where the seekers (the immune system) find it hard to travel. This makes the brain a very smart place for a parasite to hide."
Carver, 2017, p.132

'There is a strong narrative here ("the eternal game of hide and seek [parasites] play with us")- most of us are familiar with the childhood game of hide and seek, and we can readily imagine microbes or parasites hiding out from the immune cells seeking them. This makes sense, because of course, natural selection has led to an immune system that has components which are distributed through the body in such a way that they are likely to encounter any disease vectors present – as this increases fitness for the creature with such a system – and natural selection has also led to the selection of such vectors that tend to lodge in places less accessible to the immune cells – as this increase fitness of the organism that we² consider a disease organism. Thus evolution has often been described, metaphorically, as an arms race.

But this is not really a game (which implies deliberate play – parasites can not know they are playing a game); and the disease vectors do not have any conception of hiding places, and so do not pick where to go accordingly, or using any other criterion; the immune cells are not knowingly seeking anything, and do not experience it being harder to get to some places than others (they are just less likely to end up in some places for purely naturalistic reasons).

So, a parasite that ends up in the brain certainly may be less accessible to the immune system, but is not deliberately hiding there – and so is no more 'smart' to end up there than boulders that congregate at the bottom of a mountainside because they think it is a good place to avoid being sent rolling by gravity (and perhaps having decided it would be too difficult to ascend to the top of the mountain).⁴

It is not difficult to de-construct a text in the way I have done above for the hide-and-seek comparison- if a reader thinks this is useful, and consequently continually pauses to do so. Yet, one of the strengths of a narrative is that it drives the reader forward through a compelling account, drawing on familiar schemata (e.g., hide and seek; dining; setting up home…) that the reader readily brings to mind to scaffold meaning-making.

Another familiar (to humans) schema is choosing from available options:

"…the neutrophil's killer skills come to the fore…It only has to ask one question: which super skills should be deployed for the problem at hand?"
Carver, 2017, p.27

So, it seems this type of immune cell has 'skills', and can pose itself (and answer) the question of which skills will be most useful in particular circumstances (perhaps just like a commando trained to deal with unexpected scenarios that may arise on a mission into enemy-held territory?) Again, of course, this is all figurative, but I wonder just how aware most readers are of this as they read.

Carver's account of Kupffer cells makes them seem sentient,

"The Kupffer cells hang around like spiders on the walls of the blood vessels waiting to catch any red blood cells which have passed their best before date (typically 120 days). Once caught, the red blood cell is consumed whole by the Klupffer cell, which sets about dismantling the haemoglobin inside its tasty morsel."
Carver, 2017, p.27

Kupffer cells surely do not 'hang around' or 'wait' in anything more than a metaphorical sense. If 'catching' old red blood cells is a harmless metaphor, describing them as tasty morsels suggests something about the Kupffer cells (they have appetites that discriminate tastes – more on that theme below) that makes them much more like people than cells.

Another striking passage suggests,

"Some signals are proactive, for example when cells periscope from their surface a receptor called ULBP (UL16-binding protein). Any NK cell that finds itself shaking hands with a ULBP receptor knows it has found a stressed-out cell. The same is true if the NK cell extends its receptors to the cell only to find it omits parts of the secret-handshake expected from a normal cell. Normal, healthy cells display a range of receptors on their surface which tell the world 'I'm one of us, everything is good'. Touching these receptors placates NK cells, inhibiting their killer ways. Stressed, infected cells display fewer of these normal receptors on their surface and in the absence of their calming presence the trigger-happy NK cells attack."
Carver, 2017, p.27

That cells can 'attack' pathogens is surely now a dead metaphor and part of the accepted lexicon of the topic. But cells are clearly only figuratively telling the world everything is good – as 'telling' surely refers to a deliberate act. The hand-shaking, including the Masonic secret variety (n.b., a secret implies an epistemic agent capable of of knowing the secret), is clearly meant metaphorically – the cell does not 'know' what the handshake means, at least in the way we know things.

If the notion of a cell being stressed is also a dead metaphor (that is 'stressed' is effectively a technical term here {"the concept of stress has profitably been been exported from physics to psychology and sociology" Bunge, 2017/1998}), a stressed-out cell seems more human – perhaps so much so that we might be subtly persuaded that the cell can actually be placated and calmed? The point is not that some figurative language is used: rather, the onslaught (oops, it is contagious) of figurative language gives the reader little time to reflect on how to understand the constant barrage of metaphors…

"…it takes a bit of time for the B cells to craft a specific antibody in large quantities. However the newly minted anti-pollen antibodies are causing mischief even if we can't see evidence of it yet. They travel round the body and latch on to immune cells called masts anywhere they can find them. This process means the person is now 'sensitised' to the pollen and the primed mast cells lie in wait throughout the body…"
Carver, 2017, pp.183-184

…so, collectively the language can be insidious – cells can 'craft' antibodies (in effect, complex molecules) which can cause mischief, and find mast cells which lie in wait for their prey.

Sometimes the metaphors seemed to stretch even figurative meaning. A dying cell will apparently 'set its affairs in order'. In humans terms, this usually relates to someone ensuring financial papers are up to date and sorted so that the executors will be able to readily manage the estate: but I was not entirely sure what this metaphor was intended to imply in the case of a cell.

Animistic language

Even a simple statement such as "First the neutrophil flattens itself"(p.28) whilst not implying a conscious process makes the neutrophil the active agent rather than a complex entity subject to internal mechanisms beyond its deliberate control. ³

So, why write

"Finally, the cell contracts itself tightly before exploding like a party popper that releases deadly NETs [neutrophil extracellular traps] instead of streamers."
Carver, 2017, p.27

rather than just "…the cell contracts tightly…"? I suspect because this offers a strong narrative (one of active moral agents engaged in an existential face-off) that is more compelling for readers.

Neutrophils are said to 'gush' and to 'race', but sometimes to be slowed down to a 'roll' when they can be brought to a stop ("stopping them in their tracks" if rolling beings have tracks?). But on other occasions they 'crawl'. Surely crawling is a rather specific means of locomotion normally associated with particular anatomy. Typically, babies crawl (but so might soldiers when under fire in a combat zone?)

There are many other examples of phrases that can be read as anthropomorphic, or at least animistic, and the overall effect is surely insidious on the naive reader. I do not mean 'naive' here to be condescending: I refer to any reader who is not so informed about the subject matter sufficiently to already understand disease and immunity as natural processes, that occur purely through physical and chemical causes and effects, and that have through evolution become part of the patterns of activity in organisms embedded in their ecological surroundings. A process such as infection or an immune response may look clever, and strategic, and carefully planned, but even when very complex, is automatic and takes place without any forethought, intentions, emotional charge or conscious awareness on the part of the microbes and body cells involved.

There are plenty of other examples in 'Immune' of phrasing that I think can easily be read as referring to agents that have some awareness of their roles/aims/preferences, and act accordingly. And by 'can easily be read', I suspect for many lay readers (i.e., the target readership) this means this will be their 'natural' (default) way of interpreting the text.

So (see Box 3 , below), microbes, cells, molecules and parasites variously are in relationships, boast, can beckon and be beckoned, can be crafty, can be egalitarian, can be guilty, can be ready to do things, can be spurred on, can be told things, can be treacherous, can be unaware (which implies, sometimes they are aware), can dance choreographed, can deserve blame, can find things appealing, can have plans, can mind their own business, can pay attention, can spot things, can take an interest, can wheedle (persuade), congregate, craft things, dare to do things, do things unwittingly, find things, get encouraged, go on quests, gush, have aims, have friends, have goals, have jobs, have roles, have skills, have strategies, have talents, have techniques, insinuate themselves, know things, like things, look at things, look out for things, play, outwit, race, seek things, smuggle things, toy with us, and try to do things.

Microbes moving in

One specific recurring anthropomorphic feature of Carver's descriptions of the various pathogens and the harmless microbes which are found on and in us, is related to finding somewhere to live – to setting up a home. Again, this is clearly metaphorical, a microbe may end up being located somewhere in the body, but has no notion, or feeling, of being at home. Yet the schema of home – finding a home, setting up home, being at home, feeling at home – is both familiar and, likely, emotionally charged, and so supports a narrative that fits with our life-experiences.

A squatter among pathogen society? Images by Peter H (photograph) and Clker-Free-Vector-Images (superimposed virus) from Pixabay

Viruses and bacteria are compared in terms of their travel habits (in relation to which, "The human hookworm…[has] got quite an unpleasant commute to work…"),

"…viruses are the squatters of pathogen society. Unlike bacteria, which tend to carry their own internal baggage for all their disease-making needs, viruses pack light. They hold only the genes they need to gain illegal entry to our cells and then instruct our cells' machinery to achieve the virus's aims. The cell provides a very happy home for the virus, and also gives it cover from the immune system."
Carver, 2017, p.35

These pathogens apparently form a society (where there is a distinction between what is and what is not legal ⁵) and individually have needs and aims. A virus not only lives in a home, but can be happy there. Again, such language does have a sensible meaning (if we stop to reflect on just what the metaphors can sensibly mean), but it is a metaphorical meaning and so should not be taken literally.

The analogy is however developed,

"…the human microbiota is the collective name for the 100 trillion micro-organisms that have made us their real estate. From the tip of your tongue to the skin you sit on, they have set up home in every intimate nook and cranny of our body…The prime real estate for these microbes, the Manhattan or Mayfair equivalent inside you and me, is the large intestine or colon. If you had a Lonely Planet or Rough Guide to your gut, the colon would have an entry something like this: 'The colon is a must-see multi-cultural melting-pot, where up to one thousand species of bacteria mingle and dine together every second of every day. In this truly 24/7 subterranean city, Enterococci rub shoulders with Clostridia; Bacteroides luxuriate in their oxygen-depleted surroundings and Bifidobacteria banquet on a sumptuous all-you-can-eat poo buffet. It's the microbe's place to see, and be seen'. ….[antibiotic's] potential to kill off vast swathes of the normal gut flora. This creates an open-plan living space for a hardy bacterium called Clostridium difficile. This so-called superbug (also known as C. diff) is able to survive the initial antibiotic onslaught and then rapidly multiplies in its newly vacated palace."
Carver, 2017, p.76-78

This metaphor is reflected in a number of contexts in Immune. So, the account includes (see Box 4, below) break ins, camps, communities, homes, lounging, palaces, penthouses, playgrounds, preferred places to live, real estate, residents, shops, squatters, suburban cul-de-sacs, and tenants .

What is for dinner?

The extracts presented above also demonstrate another recurring notion, that microbes and body cells experience 'eating' much like we do ('tasty morsel', 'dine together', 'banquet…buffet'). There are many other such illusions in 'Immune'.

We could explain human eating preferences and habits in purely mechanistic terms of chemistry, physics and biology – but most of us would think this would miss an important level of analysis (as if what people can tell us about what they think and feel about their favourite foods and their eating habits is irrelevant to their food consumption) and would be very reductive. Yet, when considering a single cell, such as a Kupffer cell, surely a mechanistic account in terms of chemistry, physics and biology is not reductionist, but exhaustive. Anything more is (as Einstein suggested about the aether) superfluous.

One favoured dining location is the skin:

"The Demodex dine on sebum (the waxy secretion we make to help waterproof our skin), as well as occasionally munching on our skin cells and even some unlucky commensal bacteria like Propionibacterium acnes…like many of us, P. acnes is a lipophile, which is to say it adores consuming fat. The sebum on our skin is like a layer of buttery, greasy goodness that has P. acnes smacking its lips. However, when P. acnes turns up to dine it has some seriously bad table manners, which can include dribbling chemicals all over our faces…[non-human] animal sebum lacks the triglyceride fats that P. acnes [2 ital] loves to picnic on."
p.82
Carver, 2017, pp.81-82

It is hopefully redundant, by this point, for me to point out that Propionibacterium acnes does not adore anything – neither preferred foodstuffs nor picnics – but has simply evolved to have a nutritional 'regime' that matches its habitat. Whilst this extract immediately offers a multi-course menu of metaphors, it is supplemented by a series of other semantic snacks. So 'Immune' also includes references to buffet carts, chocolate chips, cookies, devouring, easy meals, gobbling up, making food appetising, making food tastier, munching, a penchant for parma ham and rare steak, soft-boiled eggs, tasty treats and yummy desserts.

Can you have too much of a metaphorical good thing?

I am glad I bought 'Immune'. I enjoyed reading it, and learnt from it. But perhaps a more pertinent question is whether I would recommend it to a non-scientist* interested in learning something about immunity and the immune system. Probably, yes, but with reservations.

Is this because I am some kind of scientific purist (as well as a self-acknowledged pedant)? I would argue not: if only because I am well aware that my own understanding of many scientific topics is shallow and rests upon over-simplifications, and in some cases depends upon descriptive accounts of what strictly need to be appreciated in formal mathematical terms. I do not occupy sufficiently high ground to mock the novice learner's need for images and figures of speech to make sense of unfamiliar scientific ideas. As a teacher (and author) I draw on figurative language to help make the unfamiliar become familiar and the abstract seem concrete. But, as I pointed out above, figurative language can sometimes help reveal (to help make the unfamiliar, familiar); but can also sometimes obscure, a scientific account.

I have here before made a distinction between the general public making sense of science communication in subjective and objective terms. Objective understanding might be considered acquiring a creditable account (that would get good marks in an examination, for example). But perhaps that is an unfair test of a popular science book: perhaps a subjective making-sense, where the reader's curiosity is satisfied – because 'yes, I see, that makes sense to me' – is more pertinent. Carver has not written 'Immune' as a text book, and if readers come away thinking they have a much better grasp of the immune system (and I suspect most 'naive' readers certainly would think that) then it is a successful popular science book.

My reservation here is that we know many learners find it difficult to appreciate that cornerstone of modern biology, natural selection (e.g., Taber, 2017), and instead understand the living world in much more teleological terms – that biological processes meet ends – occur to achieve aims – and do so through structures which have been designed with certain functions in mind.

So, microbes, parasites, cells, and antibodies, which are described as though they are sentient and deliberate actors – indeed moral agents seeking strategic goals, and often being influenced by their personal aesthetic tastes – may help immunity seem to make sense, but perhaps by reinforcing misunderstandings of key foundational principles of biology.

In this, Catherine Carver is just one representative of a widespread tendency to describe the living world in such figurative terms. Indeed, I might suggest that Carver's framing of the immune system as a defence force facing hostile invaders makes 'Immune' a main-stream, conventional, text in that it reflects language widely used in public science discourse, and sometimes even found in technical articles in the primary literature.

A myth is a story that has broad cultural currency and offers meaning to a social group, usually involving supernatural entities (demons, superhuman heroes, figures with powerful magic – perhaps microbial aesthetes and sentient cells?), but which is not literally true. e.g., Your immune system comprises a vast army of brave and selfless soldiers seeking to protect you from intruders looking to do you harm: an immune response is a microcosm of the universal fight between good and evil?

My question, then, is not whether Carver was ill-advised to write 'Immune' in the way she has, but whether it is time to more generally reconsider the widespread use of the mythical 'war' analogy in talking about immunity and disease.

Notes

¹ Even if, for example, some interactions between groups of ants from different nests {e.g., see 'Ant colony raids a rival nest | Natural World – Empire of the Desert Ants – BBC'} look just as violent as anything from human history, their 'battles' are surely not planned as part of some deliberate ongoing campaign of hostilities.

² The bacteria infecting us, if they could conceptualise the situation (which they cannot), would have no more reason to consider themselves a disease, than humans who 'infected' an orchard and consumed all the fruit would consider themselves a disease. Microbes are not evil for damaging us, they are just being microbes.

³ If my rock analogy seems silly, it is because we immediately realise that rocks are just not the kind of entities that behave deliberately in the world. The same is true of microbes and body cells -they are just not the kind of entities that behave deliberately in the world, and as long as this is recognised such metaphorical language is harmless. But I am not sure that is so immediately obvious to readers in these cases.

⁴ Such an issue can arise with descriptions about people as well. If I want to share a joke with a friend I may wink. If a fly comes close to my eye I may blink. Potentially these two actions may seem indistinguishable to an observer. However, the first is a voluntary action, but in the second case the 'I' that blinks is not me the conscious entity that ascribes itself self-hood, but an autonomous and involuntary subsystem! In a sense a person winks, but has blinking done to her.

⁵ If entry to our cells was 'illegal' in the sense of being contrary to natural laws/laws of nature, it would not occur.

* A note on being a scientist. Any research scientists reading this might scoff at my characterisation of the readers of popular science books as being non-scientists with the implied suggestion that I, by comparison, should count as a scientist. I have never undertaken research in the natural sciences, and, although I have published in research journals, my work in science education would be considered as social science – which in the Anglophile world does not usually count as being considered 'science' per se. However, in the UK, the Science Council recognises science educators as professional scientists. Learned societies such as the Royal Society of Chemistry and the Institute of Physics will admit teachers of these subjects as professional members, and even Fellows once their contributions are considered sufficient. This potentially allows registration as a Chartered Scientist. Of course, the science teacher does not engage in the frontiers of a scientific research field in the way a research scientist does, however the science teacher requires not only a much broader knowledge of science, but also a specialist professional expertise that enables the teacher to interrogate and process scientific knowledge into a form suitable for teaching. This acknowledges the highly specialised nature of teaching as an expert professional activity which goes far beyond the notion of teaching as a craft that can be readily picked up (as sometimes suggested by politicians).

Work cited

Bunge, M. (2017/1998). Philosophy of Science. Volume 1: From problem to theory. Routledge. (1967)
Carver, C. (2017). Immune. How your body defends and protects you. Bloomsbury Sigma.
Taber, K. S. (2017). Representing evolution in science education: The challenge of teaching about natural selection. In B. Akpan (Ed.), Science Education: A Global Perspective (pp. 71-96). Switzerland: Springer International Publishing.
[Download chapter]
Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568. [Download here.]

"neutrophil is a key soldier"
"the human body is like an exceedingly well-fortified castle, defended by billions of soldiers"
"…the incredible arsenal that lives within us…"
"the hidden army"
"…our adaptive assassins, our T and B cells"
"The innate system is the first line of defence…"
skin: "…an exquisite barrier that keeps unwanted invaders out."
"…your airways are exceedingly well booby-trapped passages lined with goblet cells, which secrete a fine later of mucus to trap dirt and bacteria."
"Initially it was seen as a simple soldier with a basic skills set …Now we know it is a crafty assassin with a murderous array of killing techniques."
"…ninja skill of neutrophils…", "ninja neutrophils"
"macrophages are stationed at strategic sites…what an important outpost the liver is for the immune system"
"NK cells [have] killer ways"
"trigger-happy NK cells"
"Ever neat assassins, NK cells"
"vicious immune cells" compared to "a pack of really hungry Rottweilers"
interleukins are "pro-inflammatory little fire-starters"
"neutrophils, macrophages and other immune system soldiers"
"T cells…activate their invader-destroying skills."
"…a weapon with a name worthy of a Bond villain's invention: the Membrane Attack Complex"
"miniature mercenaries"
"a system whose raise d'etre is to destroy foreign invaders"
"everything we do exposes us to millions of potential invaders."
"…all invaders need an entry point…"
"these tiny sneaks [e.g., E. coli]"
"the dark-arts of pus-producing bacteria…"
Neisseria meningitidis: "this particular invader"
"foreign invaders"
"an aggressive border patrol"
'Tregs are the prefects of the immune system…"
"…the parasite larva has more in common with a time bomb…"
"T cells…are the grand high inquisitors of the immune system, spotting and destroying infected cells and even cancer…these assassins"
"imagining you have to make a Mr Potato Head army, and you know that the more variety in your vegetable warriors the better"
"this process is about …making a mutant army."
"they form a fighting force that rivals Marvel Comic's Fantasic Four"
"each antibody molecule released as a single soldier"
"The pancreas … acts as the commander-in-chief when its comes to controlling blood sugar levels."
"our tiny but deadly defenders"
"cells in the spleen with a specialised killer-skill"
"wears a mask that conceals its killer features from its would-be assassins"
"the microbiological mass murderers…the serial killers"
"PA [protective antigen] is the muscled henchman"
"the murderous cast of immune cells and messengers…this awe-inspiring army"
"a microscopic army, capable of seeking out and destroying bacteria"
"the terminators are targeted killers"
"weaponised E. coli

Box 1: References to the immune system and its components as a defence force

"a kamikaze blaze of microbe-massacring glory"
"an eternal war between our bodies and the legions of bacteria, viruses, fungi and parasites that surround us"
"these invaders' attempts are thwarted"
"battles"
"all my innate defences would essentially hold the fort and in many instances this first line would be enough to wipe out the invader before the adaptive system gets a chance to craft bespoke weaponry."
"the tears we shed [are] a form of chemical warfare."
"…allowing the neutrophils to migrate through the blood vessel and into the battlefield of the tissue beyond"
"the cell contracts itself tightly before exploding"
"their friendly fire contributed to the death of the victim."
"spewing microbe-dissolving chemicals into the surround tissue. This allows the neutrophil to damage many microbes at once, a bit like fishing by throwing dynamite into the water."
"NK [natural killer] cells target the microbes that have made it inside our cells."
"NK cells attack"
"…the initial hole-poking assault…"
"all part of the NK cell's plan to kill the cell."
"…they trip the cell's self-destruct switch"
"expose a cell to a severe, but not quite lethal threat…transform the cell into a hardened survivor"
immune cells have an "ability to go on the rampage"
"call up … immune system soldiers to mount a response"
"leukaemia … has decimated a type of white blood cells called T cells"
"it behaves like a Trojan horse [as in the siege of the City of Troy]"
"telling our soldier cells to kick back and take some R & R"
"the smoke signals of infection"
"…like a showing of tiny hand grenades on the surrounding cells."
"the donor cells would be vastly outnumbered and it would be like a band of rebels taking on a vast army on its home turf"
"the recipient's own immune system is in a weakened state and unable to fight back"
"…the antibodies …are therefore able to give a hostile welcome to alpha-gal-wearing malaria parasites."
"…our gut bacteria effectively provide a training ground for the immune system – a boot camp led by billions of bacteria which teaches us to develop an arsenal of antibodies to tackle common foreign invader fingerprints…"
"fighting on certain fronts"
"edgy alliance"
"shore up the intestinal defences by reinforcing the tight junctions which link the gut cells together"
"our gut's security fence"
"a self-cell that should be defended, not attacked"
"this mouse-shaped Trojan horse"
"the scanning eyes of the immune system"
"a form of border control, policing"
"…the bacteria-bashing brilliance…"
"…the IgA effectively blocks and disables the invaders' docking stations…"
"B cells and their multi-class antibody armoury have the ability to launch a tailored assassination campaign against almost anything"
"the exquisitely tailored assassination of bacteria, viruses and anything else that dares enter the body"
"One of the seminal victories in our war on bugs"
"Some bacteria have a sugar-based cloaking device"
"…tripped by the pollen attaching to the IgE-primed mast cells and, like pulling a pin on a grenade, causing them to unleash their allergy-inducing chemicals."
"The almost instant assault of the immediate phase reaction occurs within minutes as the dirty bomb-like explosion of the mast cell fill the local area with a variety of rapidly acting chemicals."
"..the battle against infectious diseases."
"teaching the patrolling forces of the immune system to stand down if the cell they're interrogating is a healthy cell that belong to the body. It's a bit like a border patrol force wandering through the body and checking passports"
"like a training camp for the newly created border guards".
"ordering those that react incorrectly to self-destruct"
"These bacteria have a sugar-based polysaccharide outer shell, which acts like a cloaking device"
"the [oncolytic] viruses have a Swiss army knife selection of killer techniques"
"This approach slaughters these foot soldiers of our immune system…"
"they [macrophages] have picked up a time bomb"
"antibodies that act like heat-seeking missiles"
"Kadcyla …has a double-pronged attack."
"we are setting up easy antibiotic assault courses all over the place"
"His suicidal minions were engineered to seek out a pneumonia-causing bacterium by the name of Pseudomonas aeruginosa and explode in its presence releasing a toxic cloud of a Pseudomonas-slaughtering chemical called pyocin."
"it could secrete its killer payload"
"stimulate the little terminators to produce and release their chemical warfare."

Box 2: References to disease and immune processes as war and violent activity

"The macrophage's … job as a first responder…"
" osteoclasts and osteoblasts" are "Carver refers to "the bony equivalent of yin and yang…osteoblasts are the builders in this relationship" (said to be "toiling") …osteoclast, whose role is the constant gardener of our bones"
"…a white blood cell called the regulatory T cell, or 'Treg' to its friends…"
"…this biological barcode lets the T cell know that it's looking at a self-cell …"
"…the ball of cells that makes up the new embryo finishes bumbling along the fallopian tube and finds a spot in the uterus to burrow into…"
"By using this mouse-shaped Trojan horse the parasite gets itself delivered directly into the cat's gut, which is where Toxoplasma likes to get it on for the sexual reproduction stage of its lifecycle."
"It's as if the trypanosome has a bag of hats that it can whip out and use to play dressing-up to outwit the immune system."
"proteins… help smuggle the ApoL1 into the parasite"
"Some parasites have a partner in crime…"
"the chosen strategy of the roundworm Wuchereria bancrofti…uses a bacterium to help cloak itself from the immune system."
"the work of a master of disguise…precisely what Wuchereria bancrofti is."
"…its bacterial side-kick"
"parasites that act as puppet masters for our white blood cells and direct our immune response down a losing strategy"
"parasites with sartorial skills that craft themselves a human suit made from scavenged proteins"
"parasites toy with us"
"B cells have one last technique"
"Chemical messengers beckon these B cells"
"what AID [activation induced deaminase] seeks to mess with"
"Each class [of antibody] has its own modus operandi for attacking microbes"
"in terms of skills, IgG can activate the complement cascade"
"…one of its [IgA] key killer skills is to block any wannabe invaders from making their way inside us."
"the helper T cell and the cytotoxic T cell, which take different approaches to achieve the same aim: the exquisitely tailored assassination of bacteria, viruses and anything else that dares enter the body."
"B cells, cytoxic T cells and macrophages in their quest to kill invaders"
"T cells interact with their quarry"
"add a frisson of encouragement to the T cell, spurring it on to activation."
"the brutally egalitarian smallpox"
"Polio is another virus that knows all about image problems."
"the guilty allergen"
"IgE and mast cells are to blame for this severe reaction [anaphylaxis]"
"…The T regulatory cells identify and suppress immune cells with an unhealthy interest in normal cells."
"the skills of a type of virus well versed in the dark arts of integrating into human DNA"
"The spleen is a multi-talented organ"
"to get rid of the crafty, cloaked bacteria"
"Even once cells are able to grow despite the chemical melting pot they're stewing in telling them to cease and desist…"
"It is believed that tumour cells bobbing about in the bloodstream try to evade the immune system by coating themselves in platelets…"
"the cancer's ability to adorn itself"
"They [oncolytic viruses] work by …drawing the attention of the immune system"
"when the replicating virus is finally ready to pop its little incubator open"
"…anthrax, which lurks in the alveoli awaiting its cellular carriage: our macrophages…"
"The macrophages are doing what they ought … Completely unaware that they have picked up a time bomb…"
"the microbial thwarting talents of interferons"
"…your mAbs will do the legwork for you, incessantly scouring the body for their target destination like tiny, demented postal workers without a good union."
"One of the tumour techniques is to give any enquiring T cells a 'these aren't the cells you're looking for' handshake that sends them on their way in a deactivated state, unaware they have let the cancer cells off the hook. Checkpoint inhibitor mAbs bind to the T cell and prevent the deactivating handshake from happening. This leaves the T cell alert and able to recognise and destroy the cancer cells."
"A third neutrophil strategy…"
"all part of the NK cell's plan to kill the cell."
"…a majestic dance of immune cells and messengers, carefully choreographed…"
"So my immune system's bag of tricks might not currently include a smallpox solution, but if I were to contract the disease my adaptive immune response would try its hardest to create one to kill the virus before it killed me."
"Thus earwax can catch, kill and kick out the multitude of microbes that wheedle their way into out ears…"
"Up to 200 million neutrophils gush out of our bone marrow and into the blood stream every day. They race around the blood on the look-out for evidence of infection."
"a process called 'opsonisation' make consuming the bacterial more appealing to neutrophils"
"the same siren call of inflammation and infection that beckoned the neutrophils."
"…a set of varied and diverse circumstances can prompt multiple macrophages to congregate together and, like a massive Transformer, self-assemble into one magnificent giant cell boasting multiple nuclei."
"The cell responds to the initial hole-poking assault by trying to repair itself…At the same time that it pulls in the perforin holes, the cell unwittingly pulls in a family of protein-eating granzymes…"
"the gigantosome is more than just a pinched-off hole-riddled piece of membrane; its creation was all part of the NK cell's plan to kill the cell."
caspases in cells "play an epic game of tag"
Arachidonic acid: "Normally it just minds its own business"
"The interferon molecule insinuates itself into the local area"
"The chemokines …their ability to beckon a colourful array of cells to a particular location…they can call up neutrophils, macrophages and other immune system soldiers to mount a response to injury and infection…"
"chemicals that can tell these cells where to go and what to do. These crafty chemicals…"
"…the triad of goals of the complement system…"
"It's the T cell's job to spot infected or abnormal cells."
"Microbes aren't easy bedfellows"
"…the 'lean' microbes won out over the 'obese' ones."
"IgD is the most enigmatic of all the immunoglobins"
"the parasite larva …treacherous"

Box 3: Examples of phrasing which might suggest that microbes, cells, etc., are sentient actors with human motivations

"Bifidobacterium infantis, a normal resident of the healthy infant gut"
"trillions of microbes that make us their home"
"…a much more diverse community of inner residents…"
"Entamoeba … just happened to prefer to live in a multicultural colon."
"…the mouth had the least stable community, like the microbial equivalent of transient squatters, while the vagina was the quiet suburban cul-de-sac of the map, with a fairly fixed mix of residents."
"that's where they [Mycobacteria] set up home"
"Neisseria meningitidis "sets up shop inside our cells…it breaks in…"
"…Heliocobacter pylori (a.k.a H. pylori), a bacterium that makes its home in the sticky mucus that lines the stomach. While the mucus gives H. pylori some protection from the gastric acid, it also employed a bit of clever chemistry to make its home a touch more comfortable."
Dracunculus medinensis will "seek out a mate, turning the abdominal wall into their sexual playground."
"…plenty of creepy crawlies have been known to to call the human brain home, lounging among our delicate little grey cells…"
the tapeworm Spirometra erinaceieuropaei : "…this particular tenant ensconced in their grey matter."
"the worm…wriggled up through his body to reach its cranial penthouse where it could enjoy the luxury of a very special hiding spot."
"There are flatworms, roundworms hookworms, whipworms, fleas and ticks, lice and amoeba. They're all queuing up to get a room at the palace of parasites"
Clostridium tetani "can often set up camp in soil",
"About 75 million people worldwide are thought to carry the dwarf tapeworm in their small intestine, where it lives a fairly innocuous life and causes its host few if any symptoms."
"Though it may not seem like it, our nostrils are prime real estate and rival bacteria fight each other for resources, a fight which includes chemical warfare."
"…we'll meet the creepy critters that like to call us home and the ways our immune system tries to show them the door."

Box 4: Microbes and cells described as the kind of entities which look for and set up homes.

"an all-you-can-eat oligosaccharide buffet for B. infantis [Bifidobacterium infantis]"
"…complement's ability to make these bacteria seem tastier to our macrophages…"
"Mycobacteria… actually want to be gobbled up by our macrophages…"
"sprinkling C3b on the surface of bacteria makes them much more appetising to microbe-munching cells"
macrophages 'devour' the remains of dead cells
"…Salmonella, which likes a soft-boiled egg, and Toxoplasma gondii, which shares my penchant for parma ham and rare steak."
Dracunculus medinensis "looks like an easy meal for a peckish water flea. Sadly for the water flea the parasite larva has more in common with a time bomb than a tasty snack ever should, and the treacherous morsel spends the next 14 days inside the flea…"
"…flagging a microbe as munchable for macrophages…"
"IgG …can mark targets as munchable. Thus any bacterium, virus or parasite coated in IgG finds itself the yummiest dessert on the buffet cart and every hungry macrophage rushes to get itself a tasty treat."
"…from our brain to our bones, we are riddled with munching macrophages…"
opsonisation: "much like sprinkling tiny chocolate chips on a bacterial cookie"
"Demodex dine on sebum…as well as occasionally munching on our skin cells"
"P. acnes is a lipophile, which is to say it adores consuming fat. The sebum on our skin is like a layer of buttery, greasy goodness that has P. acnes smacking its lips."
"when "P. acnes turns up to dine it has some seriously bad table manners"
" P. acnes loves to picnic."

Box 5: References to the culinary preferences and habits of entities such as microbes and immune cells

Making molecular mechanisms familiar

A reflection on the pedagogy in Andrew Scott's 'Vital Principles'

Keith S. Taber

Andrew Scott's introduction to the chemistry of the cell is populated by a diverse cast of characters, including ballot machines, beads; blind engineers and blind-folded art-seekers; builders and breaker's yards; cars, freight vehicles and boats; Christmas shoppers, dancers; gatecrashers (despite gatekeepers) and their hosts; invaders, jack-in-the-boxes, legal summonses, light bulbs, mixing bowls, maelstroms, music tapes, office blocks; oceans, seas, rivers, streams, floods and pools; skeletons and their bones, split personalities, springs; sorting offices and postal systems; turnstiles, the water cycle, water wheels, ropes, pulleys and pumps; work benches and work stations; and weeding and seaweed forests.

Scott, A. (1988). Vital Principles. The molecular mechanisms of life. Basil Blackwell.

The task of the popular science writer

This piece is not a formal review of, what is, now, hardly a recent title ¹, but a reflection on an example of a science book aimed at – not a specific level of student, but – a more general audience. The author of a 'popular science book' has both a key advantage over the author of many science textbooks, and a challenge. The advantage is being able to define your own topic – deciding what you wish to cover and in how much detail. By contrast, a textbook author, certainly at a level related to formal national examination courses, has to 'cover' the specified material. ²

However the textbook author has the advantage of being able to rely on a fairly well defined model of the expected background of the readership. ³ Students taking 'A level' physics (for example) will be expected to have already covered a certain range of material at a known level through science teaching at school ('G.C.S.E. level') and to have also demonstrated a high level of competence against the school maths curriculum. This is important because human learning is incremental, and interpretive, and so iterative: we can only take in a certain amount of new material at any time, and we make sense of it in terms of our pool of existing interpretative resources (past learning and experiences, etc.) ⁴

The teacher or textbook author designs their presentation of material based on a mental model of the interpretive resources (e.g., prerequisite learning, familiar cultural referents that may be useful in making analogies or similes, etc.) available to, and likely to be activated in the mind of, the learner when engaging with the presentation.

So, the science teacher works with a model of the thinking of the students, so as to pitch material in manageable learning quanta, that should relate to the prior learning. The teacher's mental model can never be perfect, and consequently teaching-learning often fails (so the good teacher becomes a 'learning doctor' diagnosing where things have gone wrong). However, at least the teacher has a solid starting point, when teaching 11 year olds, or 15 year olds, or new undergraduates, or whatever.

The textbook author shares this, but the popular science author has a potential readership of all ages and nationalities and levels of background in the subject. Presumably the reader has some level of interest in the topic (always helpful to support engagement) but beyond that…

Now the role of the science communicator – be they research scientist with a general audience, teacher, lecturer, textbook author, journalist, documentary producer, or popular science author – is to make what is currently unfamiliar to the learner into something familiar. The teacher needs to make sure the learners both have the prerequisite background for new teaching and appreciate how the new material relates to and builds upon it. Even then, they will often rely on other techniques to make the unfamiliar familiar – such as offfering analogies and similes, anthropomorphism, narratives, models, and so forth.

Read about making the unfamiliar familiar

As the popular science writer does not know about the background knowledge and understanding of her readers, and, indeed, this is likely to be extremely varied across the readership, she has to reply more on these pedagogic tactics. Or rather, a subset of these ways of making the unfamiliar familiar (as the teacher can use gestures, and computer animations, and physical models; and even get the class to role-play, say, electrons moving through a circuit, or proteins binding to enzymes). Thus, popular science books abound with analogies, similes, metaphors and the like – offering links between abstract scientific concepts, and what (the author anticipates) are phenomena or ideas familiar to readers from everyday life. In this regard, Andrew Scott does not disappoint.

Andrew Scott

Scott's website tells us he has a B.Sc. in biochemistry from Edinburgh, and a Ph.D. from Cambridge in chemistry, and that he has produced "science journalism published by academic publishers, newspapers, magazines and websites", and he is an "author of books translated into many languages". I have not read his other books (yet), but thought that Vital Principles did a good job of covering a great deal of complex material – basically biochemistry. It was fairly introductory (so I doubt much could be considered outdated) but nonetheless tackled a challenging and complex topic for someone coming to the book with limited background.

I had a few quibbles with some specific points made – mainly relating to the treatment of underpinning physics and chemistry ⁵ – but generally enjoyed the text and thinking about the various comparisons the author made in order to help make the unfamiliar familiar to his readership.

Metaphors for molecular mechanisms

Andrew Scott's introduction to the chemistry of the cell is populated by a diverse cast of characters, including ballot machines, beads; blind engineers and blind-folded art-seekers; builders and breaker's yards; cars, freight vehicles and boats; Christmas shoppers, dancers; gatecrashers (despite gatekeepers) and their hosts; invaders, jack-in-the-boxes, legal summonses, light bulbs, mixing bowls, maelstroms, music tapes, office blocks; oceans, seas, rivers, streams, floods and pools; skeletons and their bones, split personalities, springs; sorting offices and postal systems; turnstiles, the water cycle, water wheels, ropes, pulleys and pumps; work benches and work stations; and weeding and seaweed forests.

A wide range of metaphors are found in the book. Some are so ubiquitous in popular science discourse that it may be objected they are not really metaphors at all. So, do "… 'chloroplasts'…trap the energy of sunlight…"? This is a simplification of course (and Scott does go into some detail of the process), but does photosynthesis actually 'trap' the energy of sunlight? That is, is this just a simplification, or is it a figurative use of language? Scott is well aware that energy is not a concept it is easy to fully appreciate,

"Energy is really an idea invented by mankind, rather than some definite thing…

energy can be thought of as some sort of 'force resistance' or 'antiforce' able to counteract the pushes or pulls of the fundamental forces."
pp.25-26

But considerable ingenuity has been used in making the biochemistry of the cell familiar through metaphor:

lipids "have split personalities" (and they have 'heads' and 'tails' of course)
proteins can "float around within a sea of lipid"
proteins are "the molecular workers"
the inside of cells can be a "seething 'metabolite pool' – a maelstrom of molecules"; "a swirling sea of chemical activity…the seething sea of metabolism" (so, some appealing alliteration, as well, here ⁶);
the molecules of the cell cytosol are "dancing"
"...small compressed springs of ATP, can be used to jack up the chemistry of the cell…"
"…thermal motion turns much of the chemical microworld into a molecular mixing bowl."
"The membranes of living cells…form a boundary to all cells, and they cordon off specific regions within a cell into distinct organelles."
"Some of these gatecrashers within other cells would then have slowly evolved into the mitochondria and chloroplasts of present-day life..."
"the 'Ca²⁺ channels' to open up, this causes Ca²⁺ ions to flood into the cell …"
"the 'ribosomes' … are the chemical automatons…"

The figurative flavour of the author's language is established early in the book,

"In a feat of stunning self-regulating choreography, billions of atoms, molecules and ions become a part of the frantic dance we call life. Each revolution of our planet in its stellar spotlight raises a little bit of the dust of earth into the dance of life, while a little bit of the life crumbles back into dust."
p.1

Phew – there is quite a lot going on there. Life is a dance, moreover a frantic dance, of molecular level particles: but not some random dance (though it relies on molecular motion that is said to be a random dance, p.42), rather one that is choreographed, indeed, self-choreographed. Life has agency. It is a dance that is in some sense powered by the revolution of the earth (abound its axis? around its star?) which somehow involves the cycling of dust into, and back out, of life – dust to dust. The reference to a stellar spotlight seems at odds with the Sun as symmetrically radiating in all directions out into the cosmos – the earth moves through that radiation field, but could not escape it by changing orbit. Perhaps this image is meant to refer to how the daily rotation of the earth brings its surface into, and out of, illumination.

So, there is not a spotlight in any literal, sense (the reference to "the central high energy furnace", p.39, is perhaps a more accurate metaphor), but the 'stellar spotlight' is a metaphor that offers a sense of changing illumination.

Similarly, the choreographed dance is metaphorical. Obviously molecules do not dance (a deliberate form of expression), but this gives an impression of the molecular movement within living things. That movement is not choreographed in the sense of something designed by a creator. But something has led to the apparently chaotic movements of billions of molecules and ions, of different kinds, giving rise to highly organised complex entities (organisms) emerging from all this activity. Perhaps we should think of one of those overblown, heavily populated, dance sequences in Hollywood films of the mid 20th century (e.g., as lampooned in Mel Brook's Oscar winning 'The Directors')?

So, in Vital Principles, Scott seeks to make the abstract and complex ideas of science seem familiar through metaphors that can offer a feel for the basic ideas of biochemistry. The use of metaphor in science teaching and other forms of science communication is a well established technique.

Read about science metaphors

Nature and nurture

Later in the book a reader will find that the metaphorical choreographer is natural selection, and natural selection is just the tautological selection of what can best reproduce itself in the environment in which it exists,

"…the brute and blind force of natural selection can be relied upon to weed out the harmful mutations and nurture the beneficial ones. We must always remember, however, that the criterion by which natural selection judges mutations as harmful or beneficial is simply the effect of the mutations on an organism's ability to pass its genetic information on to future generations."
p.182

So, natural selection is a force which is brute and blind (more metaphors) and is able to either weed out (yes, another metaphor) or nurture. That is an interesting choice of term given the popular (but misleadingly over-simplistic) contrast often made in everyday discourse between 'nature' (in the sense of genetics) and 'nurture' (in the sense of environmental conditions). Although natural selection is 'blind', it is said to be able to make judgements.

Form and function in biology

Here we enter one of the major issues in teaching about biology: at one level, that of a naturalistic explanation ⁷, there is no purpose in life: and anatomical structures, biochemical processes, even instinctive behaviours, have no purpose – they just are; and because they were components of complexes of features that were replicated, they have survived (and have 'survival value').

Yet, it seems so obvious that legs are for walking, eyes are for seeing, and the heart's function is to pump blood around the body. A purist would deny each of these (strictly these suggestions are teleological) and replace each simple statement with a formally worded paragraph completely excluding any reference to, or hint at, purpose.

So, although it seems quite natural to write

"…hormones… are released from one cell to influence the activity of other cells;

…neurotransmitters…are released from nerve cells to transmit a nerve impulse…"
pp.120-121

we might ask: is this misleading?

One could argue that in this area of science we are working with a model which is founded on the theory of natural selection and which posits the evolved features of anatomy, physiology, biochemistry,etc., that increase fitness are analogous to designed and purposeful features that support the project of the continuation of life.

Something that scientists are very quick to deny (that organisms have been designed with purposes in mind) is nevertheless the basis of a useful analogy (i.e., we can consider the organism as if a kind of designed system that has coordinated component parts that each have roles in maintaining the 'living' status of the overall system). We then get the economy of language where

hormones and neurotransmitters are released for 'this' purpose, to carry out 'that' function;

being selected (!) over

more abstract and complex descriptions of how certain patterns of activity are retained because they are indirectly selected for along with the wider system they are embedded in.

Do scientists sometimes forget they are working with a model or analogy here? I expect so. Do learners appreciate that the 'functions' of organs and molecules in the living thing are only figurative in this sense? Perhaps, sometimes, but – surely -more often, not; and this probably both contributes to, and is encouraged by, the known learning demand of appreciating the "blind [nature of the] force of natural selection".

Scott refers to proteins having a particular task (language which suggests purpose and perhaps design) whilst being clear he is only referring to the outcomes of physical interactions,

"A protein folds up into a conformation which is determined by its amino acid sequence, and which presents to the environment around it a chemical surface which allows the protein to perform its particular chemical task; and the folding and the performance of the task (and, indeed, the creation of the protein in the first place) all proceed automatically governed only by physical laws and forces of nature – particularly the electromagnetic force."
pp.54-55

In practice, biologists and medical scientists – and indeed the rest of us – find it much more convenient to understand organisms in terms of form and function. That is fine if you always keep in mind that natural selection only judges mutations metaphorically. Natural selection is not the kind of entity which can make a judgement, but it is a process that we can conceptualise as if it makes judgements.

This is a difficult balancing act:

"Nature is a blind but a supremely effective engineer. Through the agency of undirected mutation she continually adjusts the structure and the mechanisms of the living things on earth."
p.182

Nature is here treated as if a person: she is an engineer tinkering with her mechanisms. Personification of nature is a long-standing trope, once common among philosophers and not always eschewed by scientists in their writings (e.g., Nicolaus Copernicus, Henri Poincaré, Michael Faraday, even Albert Einstein have personified Nature) – and she is always female.

But usually a competent engineer tinkers according to a plan, or at least with a purpose in mind, whereas nature's tinkering is here described as 'undirected' – it is like she arbitrarily changes the size of a gear or modifies the steam pressure in a cylinder or changes the number of wheels on the locomotive, and then tinkers some more with those that stay on the tracks and manage to keep moving.

Read about personification in science

"All proteins begin life…"

Anthropomorphism: living metaphors

Personification (by referring to her, she, etc.) is not needed to imply entities have some human traits. Indeed, a very common pedagogic technique used when explaining science, anthropomorphism, is to use a kind of metaphorical language which treats inanimate objects or non-human beings as if they are people – as if they can feel, and think, and plan, and desire; and so forth.

"Once an enzyme had met and captured the required starting materials …"
"Some [non-protein metabolites] act as 'coenzymes', which becomes bound to enzymes and help them to perform their catalytic tasks."
"Cells, which had previously been aggressively independent individualists, discovered the advantages of communal life."
"…descendants of cells which took up residence within other cells and then became so dependent on their hosts, and also so useful to them, that neither hosts nor gatecrashers could afford to live apart."

So, for example, plants are living beings, but do not have a central nervous system and do not experience and reflect on life as people do: so, they do not wish for things,

"…the oxidation of sugars, is also performed by plants when they wish to convert some of their energy stores (largely held in the form of complex carbohydrates) back into ATP."
p.144

Again, such phrasing offers economy of language. Plants do not wish, but any technically correct statement would likely be more complicated and so, arguably, more difficult to appreciate.

Dead metaphors

A key issue in discussing metaphors is that in many cases different readers are likely to disagree over whether a term is indeed being used figuratively or literally. Language is fluid (metaphorically speaking), and a major way language grows is where the need for new terms (to denote newly invented artefacts or newly discovered phenomena) is satisfied by offering an existing term as a metaphor. Often, in time the metaphor becomes adopted as standard usage – so, no longer a metaphor. These examples are sometimes called dead metaphors (or clichéd metaphors). So, for example, at some point, many decades ago, astronomers started to talk of the 'life cycle' of stars which have a moment of 'birth' and eventual 'death'. These metaphors have become so established they are now treated as formal terms in the language of the discipline, regularly used in academic papers as well as more general discourse (see 'The passing of stars: Birth, death, and afterlife in the universe').

So, when Scott writes of "how some micro-organism, say a virus, invades the body…"(p.109) it is very likely most readers will not notice 'invade' as being a metaphor, as this usage is widely used and so probably familiar. The (former?) metaphor is extended to describe selective immune components "binding to foreign invaders [that] can act as a very effective means of defence against disease." These terms are very widely used in discussing infections: though of course there are substantive differences, as well as similarities, with when a country defends itself against actual foreign invaders.

I suspect that considering the lipid bilayer to be "a stable sandwich of two layers of lipid molecules" (p.115) is for many, a dead metaphor. The reference to a DNA double-helix leading to"two daughter double-helices" reflects how atomic nuclei and cells are said to give rise to 'daughters' on fission: again terminology that has become standard in the field.

Sharing a psuedo-explanation for covalent bonding

One phrase that seems to have become a dead metaphor is the notion of electrons being 'shared' in molecules, which "…are formed when their constituent atoms come together to leave at least some of their electrons shared between them" (pp.28-29). Whilst this seems harmless as a description of the structure, it is also used as an explanation of the bonding:

"'hydrogen molecules and water molecules (and all other molecules) are held together by virtue of the fact that electrons are shared between the individual atoms involved, a similarity recognised by saying that in such cases the atoms are held together by 'covalent' bonds.
p.29

But we might ask: How does 'sharing' a pair of electrons explain the molecule being 'held together'? Perhaps a couple with a strained relationship might be held together by sharing a house; or two schools in a confederation by sharing a playing field; or two scuba divers might be held together if the breathing equipment of one had failed so that they only had one functioning oxygen cylinder shared between them?

In these examples, there is of course a sense of ownership involved. Atoms do not 'own' 'their' electrons: the only bonds are electromagnetic; not legal or moral. This may seem so obvious it does not deserve noting: but some learners do come to think that the electrons are owned by specific atoms, and therefore can be given, borrowed, stolen, and so forth, but should ultimately return to their 'own' atom! So, if we acknowledge that there is no ownership of electrons, then what does it even mean for atoms to 'share' them?

So, why would two atoms, each with an electron, become bound by pooling these resources? (Would sharing two houses keep our couple with a strained relationship together; or just offer them a ready way to separate?) The metaphor does not seem to help us understand, but the notion of a covalent bond as a shared electron pair is so well-established that the description commonly slips into an explanation without the explainer noticing it is only a pseudo-explanation (a statement that has the form of an explanation but does not explain anything, e.g., "a covalent bond holds two atoms together because they share a paired of electrons").

Read about types of pseudo-explanation

Elsewhere in the book Scott does explain (if still anthropomorphically) that viable reactions occur because:

"In the new configuration, in other words, the electromagnetic forces of attraction and repulsion between all the electrons and nuclei involved might be more fully satisfied, or less 'strained' than they were before the reaction took place."
p.36

How are metaphors interpreted?

The question that always comes to my mind when I see metaphorical language used in science communication, is how is this understood by the audience? Where I am reading about science that I basically understand reasonably well (and I was a science teacher for many years, so I suspect I cannot be seen a typical reader of such a book) I do reflect on the metaphors and what they are meant to convey. But that means I am often using the familiar science to think about the metaphor, whereas the purpose of the metaphor is to help someone who does not already know the science get a take on it. This leads me to two questions:

to what extent does the metaphor give the reader a sense of understanding the science?
to what extent does the metaphor support the reader in acquiring an understanding that matches the scientific account?

These are genuine questions about the (subjective and objective) effectiveness of such devices for making the science familiar. There is an interesting potential research programme there.

Shifting to similes

The difference between metaphors and similes is how they are phrased. Both make a comparison between what is being explained/discussed and something assumed to be more familiar. A metaphor describes the target notion as being the comparison (nature is an engineer), but the listener/reader is expected to realise this is meant figuratively, as a comparison. A simile makes the comparison explicit. The comparison is marked – often by the use of 'as' or 'like' as when physicist Max Planck suggested that the law of conservation of energy was "like a sacred commandment".

Read about examples of similes in science

So, when Scott refers to how proteins "act as freight vehicles transporting various chemicals around the body", and "as chemical messages which are sent from one cell to another" (p.10), these are similes.

Springs are used as similes for the interactions between molecules or ions in solids or the bonds within molecules

"…even in solids the constituent molecules and atoms and ions are constantly jostling against one another and often vibrating internally like tiny sub-microscopic springs. All chemical bonds behave a bit like tiny springs, constantly being stretched and compressed as the chemicals they are part of are jostled about by the motion of the other chemicals all around them."
p.39

[Actually the bonds in molecules or crystals are behaving like springs because of the inherent energy of the molecule or lattice: the 'jostling' can transfer energy between molecules/ions and 'springs' so that the patterns of "being stretched and compressed" change, but it is always there. The average amount of 'jostling' depends on the temperature of the material. ⁵]

In the way the word is usually used in English, jostling is actually due to the deliberate actions of agents – pushing through a crowd for example, so strictly jostling here can be seen as an anthropomorphic metaphor, but the intended meanings seems very clear – so, I suspect many readers will not even have noticed this was another use of figurative language.

One way of marking phrases meant as similes is putting then in inverted commas, so-called scare-quotes, as in

"A rather simple chemical 'cap', for example, is added to the start of the RNA, while a long 'tail' consisting of many copies of the nucleotide A is added to its end…The most significant modifications to the precursor, however, involve the removal of specific portions from the interior [sic] of the RNA molecule, and the joining together of the remaining portions into mature mRNA… This 'splicing' process …"
p.79

Here we have something akin to a cap, and something akin to a tail. As noted above, a difficulty in labelling terms as metaphors or similes is that language is not static, but constantly changing. In science we often see terms borrowed metaphorically from everyday life to label a technical process as being somewhat like something familiar – only for the term to become adopted within the field as a technical term. The adopted terms become literal, with a related, but somewhat different – and usually more precise – meaning in scientific discourse. (This can be the basis of one class of learning impediments as students may not realise the familiar term has specials affordances or restrictions in its technical context.)

Here 'splicing' is marked as a simile – there is a process seen as somewhat similar to how, for example, radio programmes and musical recordings used to be edited by the cutting and resequencing strips of magnetic tape. Yet gene splicing is now widely accepted as a literal use of splicing, rather than being considered figurative. [I suspect a young person who was told about, for example, the Beatles experiments with tape splicing might guess the term is used because the process is like gene splicing!]

The following quote marks a number of similes by placing them within inverted commas:

"The interior of the cell is criss-crossed by a network of structural proteins which is known as the cytoskeleton. The long protein 'bones' of this skeleton are formed by the spontaneous aggregation of many individual globular protein molecules…

Cells use many strong chemical 'pillars' and 'beams' and 'glues' and 'cements', both inside them, to hold the internal structure of cells together, and outside of them, to hold different cells together; but the electromagnetic force is the fundamental 'glue' upon which they all depend."
pp.995-6

Again the phrasing here suggests something being deliberately undertaken towards some end by an active agent (teleology): the cell uses these construction materials for a purpose.

There are various other similes offered – some marked with inverted commas, some with explicit references to being comparisons ('kind of', 'act as', 'sort of', etc.)

"…amino acids comprise the chemical 'alphabet' from which the story of protein-based life (i.e., all life on earth) is constructed"
"the endoplasmic reticulum is a kind of molecular 'sorting office'…"
- endosomes and lysomes "form a kind of intracellular digestive system and 'breaker's yard'."
- "Proteins can act as gatekeepers of the cell…"
- "Proteins can…act as chemical controllers"
- proteins "can act as defensive weapons…"
- "The proteins which perform these feats are not gates, but 'pumps'..."
- "Proteins could be described as the molecular workers which actually construct and maintain all cells…"
- "…proteins are the molecular 'labourers' of life, while genes are the molecular 'manuals' which store the information needed to make new generations of protein labourers…"
- "Membrane proteins often float around within a sea of lipid (although they can also be 'held at anchor' in the one spot if required)"
- "A ribosome travels down its attached mRNA, a bit like a bead running down a thread (or sometimes like a thread being pulled through a bead)..."
- "…the 'ribosomes' – molecular 'work-benches' composed of protein and RNA…"
- Nucleic acids "act as genetic moulds"
- "the high energy structure of ATP really is very similar to the high energy state of a compressed spring"
- "Some vital non-protein metabolites act as a sort of 'energy currency'…"

Advancing to analogies

Metaphors and similes point out a comparison, without detailing the nature and limits of that comparison. A key feature of an analogy is there is a 'structural mapping': that is that two systems can be represented as having analogous structural features. In practice, the use of analogy goes beyond suggesting there is a comparison, to specifying, at least to some degree, how the analogy maps onto the target.

Read about examples of analogies in science

Scott employs a number of analogies for readers. He develops the static image of the cell skeleton (met above) with its 'bones', 'pillars' and 'beams' into a dynamic scenario:

"Structural proteins are often referred to as the molecular scaffolding of life, and the analogy is quite apt since so many structural proteins are long fibres or rods; but we think of scaffolding as a static, unchanging, framework. Imagine, however, a structure built of scaffolding in which some of the scaffolding rods were able to slide past one another and then hold the whole framework in new positions."
p.96

Many good metaphors/similes may be based upon comparisons of this type, but they do not become analogies until this is set out, rather than being left to the listener/reader to deduce. For this reason, analogies are better tools to use in teaching than similes as they do not rely on the learners inferring (guessing?) what the points of comparison are intended to be. ⁸

So, Scott offers the simile of molecules released as 'messengers', but then locates this in the analogy of the postal system, before using another analogy to specify the kind of message being communicated,

"Cells achieve such chemical communication in various ways, but the most vital way is by releasing chemical 'messenger' molecules (the biological equivalent of the postal system, if you like analogies), and many of these messengers are either proteins, or small fragments of proteins."
…
"A biological messenger molecular is more like a legal summons than a friendly note or some junk mail advertisement – it commands the target cell to react in a precise way to the arrival of the message."
pp.102-103

In the following analogy the mapping is very clear:

"One gene occupies one region of a chromosome containing many genes, much like one song occupies one region of a music tape containing many songs overall."
p.7

Song on music tape is to gene on chromosome

For an analogy to be explicit the mapping between target and analogue must be clear, as here, where Scott spells out how workstations on a production line map onto enzymes,

"The production line analogy is a very good one. The individual 'work stations' are the enzymes, and at these molecular work stations various chemical components are brought together and fashioned into some new component of product. The product of one enzyme can then pass down the line, to become the substrate of the next enzyme, and so on until the pathway is complete."
p.147

Some analogies offer a fairly basic mapping between relatively simple systems:

"If there is lots of A around in the cell, for example, then the rate at which A tends to meet up with enzyme E_AB will obviously increase (just as an increase in the number of people you happen to know entering a fairground will increase the chances of you meeting up with someone you know)."
p.150

fairground	cell
people at a fairground	molecules in the cytosol
you at the fairground	a specific enzyme in the cytosol
people entering the fairground that know you personally	molecules of a type that binds to the specific enzyme
chance of you meeting someone you know	rate of collision between enzyme and the specific molecules it binds to

An analogy with a vote counting machine

Scott compares a nerve cell, the activity of each of which is influenced by a large number of 'input' signals, to a ballot counting machine,

"…most nerve cells receive inputs, in the form of neurotransmitters, from many different cells, so the 'decision' about whether or not the cell should fire depends on the net effect of all the different inputs, some of which will be excitatory, and some inhibitory, with the pattern of input perhaps varying all the time.

So any single nerve cells acts like an [sic] tiny automatic ballot machine, assessing the number of 'yes' and 'no' votes entering it at any one time and either firing or not firing depending on which type of vote predominates at any one time.

…Nerve cells receive electrochemical signals from other cells, and each signal represents a 'yes' or a 'no' vote in an election to determine whether the cell should fire."
pp.166-8

Turnstiles in Alewife station, image from Wikimedia Commons (GNU Free Documentation License)

Scott uses the image of a turnstile, a device that blocks entry unless triggered by a coin or ticket, and which automatically locks once a person has passed through, as a familiar analogue for an ion channel into a cell. The mapping is not spelt out in detail, but should be clear to anyone familiar with turnstiles of this kind,

"When it is sitting in a polarised membrane, this protein is in a conformational state in which it is unable to allow any ions to pass through the cell. When the membrane around it becomes depolarised, however, the protein undergoes a conformational change which causes it briefly to form a channel through which Na⁺ ions can pass. The channel only remains open for a short time, however, since the conformational upheaval [sic] of the protein continues until it adopts a new conformation in which the passage of Na⁺ ions is once again blocked. The overall effect of this conformational change is a bit like the operation of a turnstile – it moves from one conformation which prevents anything from passing, into a new conformation which also prevents anything from passing, but in the process of changing from one conformation to another there is a brief period during which a channel allowing passage through is opened up."
p.163

An analogy between a sodium ion channel in a membrane, and a turnstile of the kind sometimes used to give entry to a sporting ground or transport system.

Whether there is an absolute distinction between metaphors/similes and analogies in practice can be debated. So, for example, Scott goes beyond simply suggesting that the nanoscale of molecules is like a mixing bowl, but does not offer a simple mapping between systems,

"Thermal motion turns much of the chemical microworld into a 'molecular mixing bowl' … So the solution of the cytosol acts as an all pervading chemical sea in which many of the chemicals of life are mixed together by random thermal motion as if in a molecular mixing bowl."
p.40

We could see the ocean as a simile (marked by 'acts as an') and the mixing bowl as another (marked by the scare quotes, and then 'as if in a') – but there is a partial mapping with a macroscopic mixing bowl: we are told (i) what is mixed, and (ii) the agent that mixes at the molecular scale, but it is assumed that we already know these should map to (i) the ingredients of a dish being mixed by (ii) a cook.

In places, then, Scott seems to rely on his readers to map features of analogies themselves. For example, in the following (where "The chaos of a large department store on Christmas Eve, or during the January sales, is a reasonable analogy [for the cell, as] there is order and logic within a scene of frantic and often seemingly chaotic activity"), the general point about scale was well made, but (for this reader, at least) the precise mapping remained obscure,

"The frantic chaos of chemistry proceeds too fast and too remotely for us to follow it without great difficulty. We are in the position of airborne observers who see trainloads of shoppers flowing into the city on Christmas Eve morning, and trainloads of the same shoppers laden with purchases flowing back to the suburbs in the evening. From the air we can see the overall effect of suburban shoppers 'reacting' with the shops full of goods, but we remain unaware of the hidden random chaos which allows the reaction to proceed!
p.44

Perhaps other readers immediately see this, but I am not sure what the shoppers are: molecules? but then they are unchanged by reactions? As they flow together into and out of the city (cell?) they could be ions in a nerve cell, but then what are the purchases they carry away (and have they paid for them in energy)? What are the trains? (ion channels? ribosomes?) What are the shops (mitochondria)? Perhaps I am trying to over-interpret an image that is not meant to be specific – but elsewhere Scott seems to have designed his analogies carefully to have specific mappings.

A reference to "a cofactor called 'heme' which actually acts as the chemical vessel on which the oxygen is carried"seems, by itself to be a metaphor, but when read in the context of text that precedes it, seems part of a more developed analogy:

"The most obvious system of bulk transport in the human body is the blood, which flows through our arteries, capillaries and veins like a 'river of life', bringing chemical raw materials (oxygen, water and food) to every cell of the body, and taking waste products away. Within this bulk system, however, the actual job of transporting specific substances is sometimes performed by small 'freighters' such as individual blood cells and even individual protein molecules."
p.98

The precise form of transport acting as an analogue shifts when the discussion shifts from the transport process itself to what I might refer to as the loading and unloading of the 'freighter',

"So the binding of one oxygen molecule to one subunit of an empty [sic] haemoglobin complex greatly encourages the binding of oxygen to the other three available sites. This makes the multi-subunit haemoglobin complex a bit like a four-seater car in which the first person into the car unlocks the door for another three passengers. The crucial step in loading the car is getting the first person in, after which the first person helps all the others to climb aboard.

An opposite effect occurs when loaded haemoglobin reaches a tissue in need of oxygen: the loss of one oxygen molecule from one subunit causes a conformational change in the complex which allows the other three oxygen molecules to be off-loaded much more readily. A suitable analogy to this would be an unstable four-man boat, since, if one man jumps overboard, he may rock the boat sufficiently to make the other three fall out!"
pp.100-101

Why is a child like an office block?

Child is to zygote as office building is to light bulb? (Images from Pixabay)

Scott compares the development of the child from a single cell with a self-assembling office block,

"When a human egg cell begins to divide and create a newborn child it achieves an enlargement equivalent to a lightbulb giving rise to a massive office block 250 metres high; which then, over the next 15 years or so, stretches and widens to an astounding 1,000 metres in height and nearly 250 metres across. In the 'office block' that is you all the plumbing, heating, lighting, telecommunication and ventilation systems were assembled automatically and work together smoothly to sustain a bewildering diversity of very different 'suites' and 'offices'.
p.4

Scott later revisits his office analogy, though now the building is not the growing organism, but just a single cell (one of the 'offices' from the earlier analogy?),

"Cells are not stable and unchanging structures like office blocks. Instead, most parts of a cell are in a state of continual demolition and renewal, known as 'metabolic turnover'. Imagine an office block in which a large team of builders is constantly moving through, knocking down existing walls and using the bricks to build up new ones; ripping apart the furniture and then reassembling it into new forms; peeling off wallpaper, then using it as the raw material to produce new paper which is then put back up again; and all the time some new materials are arriving through the door, to assist in the continual rebuilding, while some of the older materials are constantly being discarded out of the windows. The living cells is in a very similar siltation, with teams of enzymes constantly ripping down the structure of the cell while other teams of enzymes build it up.

… Life in the office block imagined earlier might sometimes be a little difficult and chaotic, but at least when change was required it could be brought about quickly, since the necessary tradesmen and supplies would always be on hand; and any mistakes made during the building process could always quickly be put right. Metabolic turnover bestows similar advantages on the living cell."
pp.118-119

The reference to 'teams' of enzymes is another subtle anthropomorphic metaphor. Those in a team are conscious of team membership and coordinate their activities towards a common goal – or at least that is the ideal. Enzymes may seem to be working together, but that is a just a slant we put on processes. Presumably the two sets of teams of enzymes (a catabolic set and an anabolic set) map onto the large team of builders – albeit the enzymes seem to be organised into more specialised working teams than the builders.

Some of Scott's prose, then, combines different ways of making the science familiar, as when he tells the reader

"Water, in other words, is the solvent of life, meaning that it is the liquid which permeates into all the nooks and crannies of the cell and in which all the chemical reactions of life take place. There are various small regions of the cell from which water is excluded, especially within the interior of some large molecules; but the chemistry of life largely proceeds in an ocean of water. It is not a clear ocean – thousands of different types of chemical are dissolved in it, and it is criss-crossed by a dense tangle of giant molecules which form 'fibres' or 'cables' or 'scaffolding' throughout the cell. Swimming through the cell 'cytosol' (the internal 'fluid' of the cell) would be like struggling through a dense underwater forest of seaweed, or through a thick paste or jelly, rather than darting though clear ocean."
p.6

On the molecular level, the water inside of a cell is "an ocean" (a metaphor), which can access the "nooks and crannies of the cell" (a metaphor). The ocean is interrupted by "giant molecules which form 'fibres' or 'cables' or 'scaffolding'…" These terms seem to be used as similes, marked by the use of inverted commas, although Scott also uses this convention to introduce new terms – 'cytosol' is not a simile. Presumably 'fluid' (marked by inverted commas) is being used as a simile as the cytosol is not a pure liquid, but a complex solution.

[The quote implies that "It is not a clear ocean – [as/because] thousands of different types of chemical are dissolved in it", but dissolved solutes would not stop a solution being clear: the actual ocean is very salty, with many different types of ions dissolved in it, but can be clear. Lack of transparency would be due to material suspended, but not actually dissolved, in the water.]

If this is a metaphorical ocean, it is an ocean that would be difficult to swim in, as the tangle of giant molecules is analogous to "a dense underwater forest of seaweed" so it would be like swimming trough "a thick paste or jelly".

The water cycle of life

Perhaps the pièce de résistance in terms of an analogy adopted in the book was the use of a comparison between metabolism and the water cycle,

"I have drawn an analogy between the creation of living things containing many high energy chemicals (i.e. those in which the electromagnetic force is resisted much more than it could be), and the raising water vapour from the sea into the sky. We can continue with this analogy as we look deeper into the energetics of the living cell."
pp.126-127

Scott does indeed develop the analogy, as can be seen from the quotations parsed into the table below:

target concept		analogue
	"…thermodynamic law determines that the energy of the sun must disperse out to the earth and raise the energy level of the things that are found there.
The raw materials of life are some of the things that are found there, and the energy from the sun raises these raw materials up into the higher energy levels associated with organised life,
	just as
		it raises water up into the sky and deposits some of it in tidy little mountain pools."
	⧟
	"…I have drawn an analogy between
the creation of living things containing many high energy chemicals…
	and
		the raising water vapour from the sea into the sky."
	⧟
		"The raising of water to the skies is not an isolated and irreversible event, but part of a cycle in which the water eventually loses the energy gained from the sun and returns to the earth as rain, only to absorb some more energy and be lifted up once more, and so on…
	Similarly, of course,
the creation of a living being such as yourself is not an isolated and irreversible event, but is part of a cycle of life and death, of growth and decay…"
	⧟
"If we look inside the chemical mechanisms of the living cell we find that they can harness the energy available in the environment, most of which ultimately comes from the sun,
	in a manner similar to
		the [person] who has built a water wheel, a pump, a reservoir and many secondary wheels used to power many different tasks…."
	⧟
"In living things
	the roles of
		the water-wheels and pumps
	are played by
various systems of proteins and membranes,
	whilst
the the most common immediate energy reservoir is a chemical known as 'adenosine triphosphate' (ATP). ATP is the cell's
	equivalent of
		water stored in a high level reservoir or a tank
	because
it takes an energy input to make it, while energy is given out when it breaks apart into ADP and phosphate."
	⧟
"The considerable resistance to the electromagnetic force embodied in the structure of ATP imposes a strain on the ATP molecule.
	It is like
		the compressed spring of a jack-in-the-box just waiting to be released;
and when it is released in some appropriate chemical reaction, then the energy level of the molecule falls as it splits up into ADP and phosphate.
		Just as the force of water falling from a high gravitational energy level to a lower one can be harnessed to make various energy-requiring processes proceed,
	so
the force of an ATP molecule falling from a high chemical energy level to a lower one can be harnessed to make a wide variety of energy-requiring chemical reactions proceed…"
	⧟
"The ATP manufacturing enzyme
	is closely analogous to
		a water-wheel,
	for
as the hydrogen ions are allowed to flow back through the enzyme,
	just as
		water flows over a water-wheel,
	so
the ensuing chemical reactions 'lift up' the precursors of ATP into their high energy ATP state."
	⧟
"The principle of such energy coupling
	can be understood by the simple analogy of
		the water flowing downhill over a water-wheel, and thus serving to turn the wheel and, for example, raise some weight from the ground using a pulley."
	⧟
"These proteins are the molecular machines
	which take the place of
		the water-wheels and ropes and pulleys which can couple the falling of water down a mountainside to the lifting of some weight beside the stream"

An extended analogy between two systems

Whether this should be seen as one extended analogy, or more strictly as several, somewhat distinct but related, comparisons is moot, as becomes clear when trying to map out the different features. My best attempt involved some duplication and ambiguity. (Hint to all designers of teaching analogies – map them out as parallel concept maps to help you visualise and keep track of the points being made.)

An analogy (or set of analogies) between biological/biochemical and physical systems

Visualisation – mental simulation

Teaching analogies usually link to what is expected to be (for the members of the audience) a familiar situation, experience, or phenomenon. Readers will be familiar with an office block, or swimming in water.

However, it is also possible for the science communicator to set up an analogy based on a scenario which is unlikely to be familiar, but which can be readily imagined by the reader.

"To appreciate the power of random motion to bring about seemingly purposeful change, imagine a room full of blindfolded people all instructed to walk about at random 'bouncing' off the walls and one another. Imagine also that they have been told to stop moving only when they bump into a small picture hanging from a wall. Finally, suppose that all the pictures are hung in a second room, linked to the room full of people by a narrow open doorway…"
p.40

Few if any readers will have been familiar with this scenario, but the components – groups of people in rooms, blindfolding, adjoining rooms, pictures hung on walls – are all familiar and there is nothing inherently problematic about the scenario even it does not seem very likely. So, here the reader has to build up the analogy from a number of familiar but distinct images.

So, we might consider this a kind of 'gedankenexperiment' or thought experiment – the reader is prompted to consider what would happen if…(and then to transfer what would happen to the target system at the molecular scale). Perhaps some readers immediately 'see' (intuit) what happens in this situation, but otherwise they can 'run' a mental simulation to find out – a technique scientists themselves have used (if probably not regarding blindfolded people in picture galleries).

Analogies only reflect some aspects of the target being compared. The features that map unproblematically are known as the positive analogy, but there is usually a negative analogy as well: features that do not match, and so which would be misleading if carried across. Realistically, the negative analogy will usually have more content than the positive analogy, although much of the negative analogy will be so obviously irrelevant that it is unlikely to confuse anyone.

So, for example, in the analogy the blindfolded people will be wearing clothes, may exchange apologies (or curses) on bumping into each other, and will likely end up bruised – and human nature being what it is, some may cheat by sneaking a look past the edge of the blindfold – but no reader is likely to think these are features that transfer across to the target! Perhaps, however, a reader might wonder if the molecules, like the blindfolded people, are drawing on a source of energy to keep up the activity, and would tire eventually?

There are some other potentially more problematic aspects of the negative analogy. In the thought experiment, the people have been given instructions about what to do, and when to stop, and are acting deliberately. These features do not transfer across, but a reader might not realise this, and could therefore understand the analogy anthropomorphically. It is in situations like this where the teacher can seek feedback on how the analogy is being interpreted (that is, use informal formative assessment), but an author of a book loses control once the manuscript is completed.

Molecular mechanisms made familiar?

There is nothing unusual in Scott's use of metaphor, simile and analogy in seeking to help readers understand abstract scientific ideas. This is an approach common to a good deal of science communication, within and beyond formal teaching. Vital Principles offers many examples, but such devices are common in books seeking to explain science.

I did raise two questions about these techniques above. How do we know if these comparisons are effective in communicating the science? To find out, we would need to talk to readers and question them about their interpretations of the text.

In formal science teaching the focus of such research would likely be the extent to which the presentation supported a learner in acquiring a canonical understanding of the science.

However, as I suggested above, if such research concerned popular science books, we might ask whether the purpose of such books is to teach science or satisfy reader interest. Thus, above, I distinguished an objective and a subjective aspect. If a reader selected a book purely for interest, and is satisfied by what they have read – it made sense to them, and satisfied their curiosity – then does it matter if they may have not understood canonically?

When I read such texts, I wonder about both how a general readership responds to the comparisons offered by authors to make the unfamiliar familiar, and what sense the readers come away with of the science. I guess to some extent popular science authors at least get some level of feedback on the former question – if readers come back for their other titles, then they must be doing something right.

I thought Scott showed a good deal of ingenuity and craft in setting out an account of a challenging and complex area of science – but I would love to know how his different readers interpreted some of his comparisons.

Work cited:

Scott, A. (1988). Vital Principles. The molecular mechanisms of life. Basil Blackwell.
Taber, K. S. (1994) Misunderstanding the ionic bond, Education in Chemistry, 31 (4), pp.100-103.
Taber, K. S. (2001) The mismatch between assumed prior knowledge and the learner's conceptions: a typology of learning impediments, Educational Studies, 27 (2), 159-171. [Download article]

Notes:

¹ I have picked up a good many 'popular science books' over the years, but quite a few of them got put on the shelves till I had time to engage with them in any depth. Other things usually got in the way – lesson/lecture preparation being the most demanding imperative for soaking up time over my 'working' life. Retirement has finally allowed me to start going through the shelves…

² In the English context, perhaps elsewhere, the textbook is now also often expected to not only cover the right content, but follow the examination board's line on the level of treatment, even to the degree of what is acceptable phrasing. Indeed, there are now textbooks associated with the different exam board syllabuses for the 'same' qualification (e.g., A level Chemistry). This seems very unhealthy, and come the revolution…

³ The model I am referring to here is the mental model in the teacher's mind of the learner or reader – the background knowledge they have available, their existing level of understanding, the sophistication of their thinking, the range of everyday references they are familiar with which might be useful in making comparisons, their concentration span for dealing with new material or complex language …

If we think of teaching-learning as a system, many system failure (failures of students to understand teaching as intended) can be considered to be due to a mismatch – the teacher's mental model is inaccurate in ways that leads to non-optimal choices in presenting material (Taber, 2001 [Download article]).

This is the basis of the 'learning doctor' approach.

Read about Science learning doctors

⁴ This is the crux of the so called 'constructivist' perspective on teaching science – a perspective discussed in depth elsewhere on the site.

Read about constructivism

⁵ There was little in the book I really would have argued with. However, there were a few questionable statements:

"Yet this apparent miracle is completed thousands of times each day throughout the world [in humans], and similar miracles create all manner of simpler creatures, from elephants and birds and flies to bacteria and flowers and mighty oaks."
p.5

This statement seemed to reflect the long-lasting notion of nature as a 'great chain of being' with humans (in the middle of the chain, below a vast range of angelic forms, but) top of the natural world. Bacteria are simpler than humans, I would acknowledge; but I am less sure about flies; even less sure about birds; and question considering trees and other flowering plants, or elephants, as (biologically) simpler than us. This seems an anthropocentric (human-centred), rather than a scientific, take.

"…the periodic table… lists the 92 naturally occurring atoms (plus a few man-made ones) which are the basic raw materials of chemistry…"
p.19

There are clearly more than 92 naturally occurring atoms in the universe. I believe we think there are 90 naturally occurring elements. That is 90 "naturally occurring [kinds of, in the specific sense of proton number] atoms".

Similarly, "a 'compound' is any chemical [sic] composed of two or more atoms chemically bonded together" (pp.29-30) would imply that H₂, C₆₀, N₂, O₂, F₂, P₄, S₈, Cl₂, etc are all compounds (when these are elements, not compounds).

Another slightly questionable suggestion was that

"…electrons appear to surround the atomic nucleus, but in a way that allows them to dart to and fro in a seemingly chaotic manner within a particular region of space."
p.21

The notion of electrons darting back and forth does not really reflect the scientific model, but the orbital/quantum model of the atom is subtle and difficult to explain, and was not needed at the level of the description being presented.

A more obvious error was that

"…'heat' is just a measure of the kinetic energy with which particles of matter are moving…"
p.26

In physics, the temperature of a material is considered to reflect the average kinetic energy of the particles (e.g., molecules). But heat is a distinct concept from temperature. Heat is the energy transferred between samples of matter, due to a difference in temperature. So, when Scott writes

"We all know that heat energy moves inevitably from hot places to cold places, and that it will never spontaneously move in the opposite direction."
p.32

this could be seen as a tautology: like saying that imports always come into the county rather than leave – because of how imports are defined.

Although heat and temperature are related concepts, confusing or conflating them is a common alternative conception found among students. Confusing heat with temperature is like confusing a payment into your bank account with the account balance.

Moreover, Scott uses the wrong term when writes,

"[The molecules of?] Chemicals come into contact with one another because they are all constantly moving with the energy we call heat."
p.191

This internal energy that substances have due to the inherent motion of their particles is not heat – it is present even when there is a perfectly uniform temperature throughout a sample (and so no heating going on).

Scott tells readers that "Another name for … a voltage difference is a 'potential difference'…" (p.162) but the term voltage (not voltage difference) normally refers to a potential difference, p.d.. (So, the term voltage difference implies a difference between potential differences, not a difference in potential. If you had one battery with a p.d. across its terminals of 6.0V, and another with a p.d. across its terminals of 4.5V, you could say the 'voltage difference' between the batteries was 1.5V.)

A common alternative conception which Scott seems to share, or at least is happy to reinforce, is the 'fairy tale'* of how ionic bonding results from the transfer of an electron from a metal atom to a neutral non-metal atom,

"When sodium atoms react with chlorine atoms electrons are actually transferred from one atom to the other (see figure [which shows electron transfer from one atom to another]). One electron which is relatively loosely held by a sodium atom can move over to become attached to a chlorine atom."
p.30

This describes a chemically very unlikely scenario (neither sodium nor chlorine are found in the atomic state under normal conditions on earth), and if a sodium atom were to somehow collide with a chlorine atom, the process Scott describes would be thermodynamically non-viable – it requires too much energy to remove even the outermost 'relatively loosely held' electron from the neutral sodium atom. Perhaps this is why in the school laboratory NaCl tends to be prepared from solutions that already contain the sodium ions [NaOH(aq)] and the chloride ions [HCl(aq)].

* For example, read 'A tangible user interface for teaching fairy tales about chemical bonding'

It is hard to be too critical of Scott here, as this account is found in many chemistry text books (and I have even seen it expected in public examinations) although from a scientific point of view, it is a nonsense. That many learners come to think that ionic bonding is due to (or even, 'is') a process of electron transfer is surely a pedagogic learning impediment (Taber, 1994) – a false idea that is commonly taught in school chemistry.

⁶ As the author of a paper called ' Mediating mental models of metals: acknowledging the priority of the learner's prior learning', I must confess to being somewhat partial to some decent alliteration.

⁷ Many scientists will believe there is a purpose underpinning the evolution of life on earth, and will see creation as the unfolding of a supernatural plan. (Some others will vehemently reject this. Others still will be agnostic.) However, natural science is concerned with providing natural explanations of the world in terms of natural mechanisms. Even if a scientist thinks things are the way they are because that is God's will, that would be inadmissible as a scientific argument, as it does not explain how things came about through natural processes.

Read more about science and religion

⁸ Teaching, or for that matter writing a science book, is informed by the teacher's/author's mental model of how the reader/listener will make sense of the text (see above). How they actually make sense of the text depends on the interpretive resources they have available, and bring to mind, and it is common for learners/readers not to interpret texts in the way intended – often they either do not make sense of the information, or make a different sense to that intended. A teacher who is a 'learning doctor' can seek to diagnose and treat these 'teaching-learning system failures' when they inevitably occur, but teachers can avoid a good many potential problems by being as explicit as possible and not relying on learners to spontaneously make intended associations with prior learning or cultural referents.

Read about being a learning doctor

As suggested above, authors have an even more challenging task as their readerships may have a diverse range of prior knowledge and other available interpretive resources (e.g., a popular television programme or pop star in one country may be unknown to readers from another); and the author cannot check they have been understood as intended, in the way a teacher usually can.

Explaining Y T cells stop working

Communicating oncology research

Keith S. Taber

…to the best of my knowledge, there is absolutely no reason to suspect that Prof. Theodorescu falsified his academic credentials…

The following text is an extract from a podcast item reporting recently published research into bladder cancer:

"The Y-negative cells cause an immune evasive environment in the tumour, and that, if you will, paralyses, the T cells, and exhausts them, makes them tired and ineffective, and this prevents the Y-negative tumour from being rejected, therefore allowing it to grow much better."

"Exhausted T cells have lost their ability to kill cancer cells, and have lots of proteins on their surface known as checkpoints, which put the brakes on immune responses.

But this exhausting environment made by the tumours could actually be their undoing"

"What they also did, inadvertently I'm sure, is made themselves a lot more vulnerable to one of the most useful and prevalent therapeutics in cancer today, which is immune checkpoint inhibitors."

"Immune checkpoint inhibitors are a class of drugs that block those checkpoint proteins that sit on the surface of T cells, effectively taking the brakes off immune responses, causing T cells to become more aggressive."
Dan Theodorescu & Nick Petrić Howe speaking on the Nature Podcast

Prof. Dan Theodorescu MD, PhD, is the Director of the Samuel Oschin Comprehensive Cancer Institute at Cedars-Sinai, Professor of Surgery, Pathology and Laboratory Medicine; and corresponding author on the paper (Abdel-Hafiz et al., 2023) published in Nature, and discussed in the podcast.

Nick Petrić Howe, Senior Multimedia Editor at Nature Research, was the journalist presenting the item on the podcast.

Communicating science

Scientific research is communicated to other specialist scientists through research reports which reflect a particular genre of writing, and are written with specialist researchers in the same field as the main target readership. Such reports are usually of a quite technical nature, and (appropriately) assume that readers will have a high level of prior understanding of concepts in the field and the technical language used. Such tropes as simile and analogy certainly can sometimes feature, but generally figurative language is kept to a minimum.

Communication to a wider audience of people with a general interest in science needs to adopt a different register. As I have noted on this site before, this is quite challenging as a general public audience is likely to be very diverse in terms of its level of knowledge and understanding of background to any scientific research. Perhaps that is why as a former teacher (and so a science communicator that could make reasonably informed assumptions about the background of my audience in any particular lesson) I find the language of this type of science dissemination fascinating.

Read about science in public discourse and the media

The gist

The study discussed in the podcast reported on a line of research exploring the genomics of bladder cancer, and in particular how tumours that develop from cells that have deficiencies in the Y chromosome seem to have particular characteristics.

Put simply, tumours of this kind were likely to be inherently more damaging to the patient, although also likely to be more responsive to an existing class of medicines. (At this stage the work has largely relied on in vitro studies and 'animal models' (mice) so the implications for actual human cancer patients are reasonable, but speculative.)

The language used

The short extract of the dialogue I have transcribed above seems quite 'dense' in interesting language when de-constructed:

Y-negative cells – a new technical term?

The extract starts with reference to Y-negative cells. Earlier in the item it had been explained that some cells have no Y chromosome, or an incomplete Y chromosome. (For someone to understand this information, they would need to have some background knowledge relating to what chromosomes are, and why they are important in cells. ¹ ) The term Y-negative cell therefore, given that context, refers to a cell which lacks the usual Y chromosome. ² If such a cell turns cancerous it will give rise to a tumour which is Y-negative (as all the tumour cells are formed from the division of that cancerous cell). The published report notes "Loss of the Y chromosome (LOY) is observed in multiple cancer types, including 10-40% of bladder cancers" (Abdel-Hafiz et al., 2023), an observation which motivates the area of research.

An immune evasive environment?

The word 'evasion' appears in the title of the paper. To evade something means to avoid it, which might suggest a sense of deliberation. Immune evasion is a recognised issue, as in cancers "interactions between the immune system and the tumour occur through complex events that usually eventually climax either in successful tumour eradication or immune evasion by the tumour" (Vinay et al., 2015): that is, either the immune system destroys the cancer, or the cancer is able to grow due to some mechanism(s) that prevent the immune system killing the tumour cells. The 'immune evasive environment' then refers to the environment of the tumour's cells in a context where aspects of the normal immune mechanisms are inoperative or restricted.

Paralysed, exhausted and tired T cells

T cells are one of the classes of cell that make up the immune system, and the item was suggesting that with 'LOY' the T cells are unable to function in the way they normally do when interacting with cancer cells that have an intact Y chromosome. ('LOY' is the acronym for a process, viz., "loss of the Y chromosome", but once defined can be used in a way that reifies LOY as if it refers to an object. ³ In "…with 'LOY'…", I am treating LOY as a medically diagnosable condition.)

Are the T cells paralysed? That normally means not able to move, which is not the case here. So 'paralysed' seems to be used as a metaphor, a way of 'making the unfamiliar familiar' for a non specialist audience. A large part of the task of a science teacher is to make the unfamiliar [become] familiar to learners.

Read about making the unfamiliar familiar

Actually, I would better class this specific use as a simile rather than a metaphor:

"The Y-negative cells cause an immune evasive environment in the tumour, and that, if you will, paralyses, the T cells"

A simile in poetic language normally refers to something being 'like' or 'as' something else, as when the star Betelgeuse was said to be "like an imbalanced washing machine tub" or a laser was described as being used as a "kind of spark plug". Here, Prof. Theodorescu marks the term 'paralyses' with 'if you will' in a similar way to how when selection theory has been said to be "like a Tibetan prayer-wheel…" the word 'like' marks that this is noting a similarity, not an identity (selection theory is not suggested to be a prayer-wheel, but rather to be in some way like one).

Read examples of similes used in discussing science

The T cells were said to be as if paralysed, but they were also exhausted and tired. Yet, again, 'exhausted' does not seem to be meant literally. The T cell has not used up its supply of something (energy, or anything else), so this is another metaphor. 'Tired' can be seen as synonymous to exhausted, except usually 'tired' refers to a subjective experience. The T cells are not sentient and presumably do not feel tired – so, this is another metaphor; indeed an anthropomorphic metaphor, as it refers to the cells as though they have subjective experience like a person.

Read examples of metaphors used in discussing science

Hey, you immune cells – are you feeling tired? How about taking a break, and doing some stretching exercises and a little yoga?

Images from Pixabay

Anthropomorphism is a common trope in science discourse, especially in biological contexts. It can sometimes help communication of abstract material to present scientific phenomena in a narrative that relates to human subjective experience – perhaps referring to disease 'evading' the immune system – but consequently often gets adopted into in students' pseudo-explanations (e.g., the reaction happened because the atom wanted another electron, the gas expands because the molecules wanted more space). ⁴

Read about types of pseudo-explanations

Read examples of anthropomorphism in science discourse

Yet the term 'exhausted' also appears in the published research report ("Y_low bladder cancers contained a higher proportion of exhausted and progenitor exhausted CD8⁺ T cells..."). So, this is a term that is being adopted into the terminology of the research field. A paper from 2019 set out to define what this means: "'T cell exhaustion' is a broad term that has been used to describe the response of T cells to chronic antigen stimulation, first in the setting of chronic viral infection but more recently in response to tumours" (Blank, et al., 2019). Another study notes that

"It is now clear that T cells are not necessarily physically deleted under conditions of antigen persistence but can instead become functionally inept and incapable of elaborating the usual array of effector activities typically associated with robust, protective, effector and memory T-cell populations."
Yi, Cox, & Zajac, 2010

It is not unusual for terms that seem to be initially used metaphorically, to become adopted in a scientific field as technical terms (such as the 'birth' and 'death' of stars in astronomy). Indeed, inept seem to me a term that is normally applied to people who have agency and can learn skills, but lack skill in an area where the are active. The field of oncology seems to have adopted the notion of ineptitude, to label some T cells as 'inept'.

Unlike in human hereditary, where we would not assume a child can directly inherit a lack of skill in some area of activity from its parents (there is no gene for playing chess, or spraying cars, or heart surgery, or balancing account books), at the cellular level it is possible to have "inept T-cell lineages" (Fredholm et al, 2018). If one is going to anthropomorphise cells, then perhaps 'inept' is an unfair descriptor for structural changes that modify functionality, and can be passed on to 'daughter' cells: should these cells be considered to have a disability rather than be inept? For that matter, an exhausted T-cell seems to have more in common with a metamorphosed caterpillar than an exhausted marathon runner.

Rejection – a dead metaphor?

'Rejection' is a technical terms used in medical science for when the immune system 'attacks' something that it 'identifies' as not self: be that a tumour or a transplanted tissue. Note that here terms such as 'attacks' and 'identifies' are really also anthropomorphic metaphors to label complex processes and mechanisms that we gloss in human terms.

What actually happens is in effect some chemistry – there is nothing deliberate about what the cancer cells or the immune cells are doing. Tumours that grow quickly are described as 'aggressive' ("…causing T cells to become more aggressive") another term that might be understood as an anthropomorphic metaphor, as aggression normally refers to an attitude adopted. The tumour cells are just cells that grow and divide: they have no attitude nor intentions, and do not deliberately harm their host or even deliberately divide to grow the cancer.

When the term 'rejection' was first suggested for use in these contexts it will have been a metaphor itself, a word transplanted [sic] from one context where it was widely used to another novel context. However, the 'transplant took' (rather than being 'rejected'!) and came to be accepted as having a new biological meaning. Such a term is sometimes called a dead metaphor (or a clichéd metaphor) as it has lost its metaphorical status, and become a technical term. Tumours are now literally rejected. And T cells do now become exhausted (and inept). And tumours can now be aggressive.

Within the specialist field, such words now have nuanced technical meanings, related to, but subtly different from, their source words' usage in general language. Experts know that – but lay people may not always realise. Strictly, the words aggressive in 'an aggressive drunk' and 'an aggressive tumour' are homonyms.

Seated checkpoints: quo vardis, friend or foe?

The same is the case with 'checkpoints'. Referring to proteins on the immune cell surface that interact with proteins on tumour cells, the label 'checkpoints' will have been a metaphorical transplant of an existing term (as in border checkpoints, where it is checked that someone's papers are in order for entry to a country); but, now, this is accepted usage.

T cells are able to destroy other cells. However, they have proteins on their surfaces which can bind to proteins on other cells, and when these are bound the T cells do not destroy the other cells. (Do these proteins really "sit on the surface of T cells" – or is sitting an action only available to organisms with certain types of anatomic features – such as buttocks and jointed legs perhaps? So, this is another metaphor, but one that conveys meaning so readily that most listeners will not have noticed it. ⁶ )

So, immune cells have evolved because they 'protect' the organism from 'foreign' cells, and the checkpoints have evolved because they prevent the immune cells destroying cells from the same individual organism. ⁵ This works to the extent that the binding of the checkpoints is specific. Tumour cells (which are derived from the individual) can sometimes bind, and so the T cells may be ineffective in destroying them. Immune checkpoint inhibitors can interfere with the mechanism by which tumour cells act on the T cells as 'self' cells – something sometimes referred to as a checkpoint 'blockade' (yet another metaphor) – something represented in the following image:

Figure entitled "Immune checkpoint blockade for T-cell activation" (note the 'exhausted' T cells) (Fig. 2, from Darvin, et al., 2018. Open access under http://creativecommons.org/licenses/by/4.0/). [There is an interesting mix of iconic (cell shapes) and symbolic (e.g., lightning strikes?) signs in the figure.]

The extract of dialogue quoted above suggests that the checkpoints "put the brakes on immune responses". There are of course no actual brakes, so this is again metaphorical. However, we might consider 'putting the brakes' on as having become an English idiom, that is, the term is now widely understood as applying to any situation where a process is brought to a stop, regardless of whether or not there are actual brakes involved. A raise in bank interest rates might be said to be intended to put the brakes on inflation. (Indeed, as my O level economics teacher at North Romford Comp. habitually explained managing the economy in terms of driving a car – which of course we were all too young to legally have experienced – he may well have actually said this.)

Can tumours behave advertently?

At one point Prof. Theodorescu, suggested that "what [the tumours] also did, inadvertently I'm sure, is made themselves a lot more vulnerable to one of the most useful and prevalent therapeutics in cancer today". I am also sure that this effect was inadvertent. Otherwise, the tumour acted advertently, which would mean it behaved deliberately with this outcome in mind.

It clearly would not seem to be in a tumour's interest to make itself more susceptible to therapeutics, but then agents do sometimes behave in ways that seem irrational to others – for example, because of bravado. So, I do not rule out apparently self-destructive behaviour from being deliberate (as I drafted this piece, the news broadcast reports on an apparent coup attempt in Russia, suggesting that a few tens of thousands of men are looking to take over a nation of over 140 million that had been paying them to fight in the illegal invasion of Ukraine). Rather, my reason for being sure this not deliberate, is that I do not think that a tumour is the kind of entity that can behave advertently. ⁷

So, I do not disagree with Prof. Theodorescu, but I do think that stating that, in this case, the behaviour was inadvertent seems to imply that that a tumour can in some circumstances act deliberately (i.e., anthropomorphism, again). I am sure that was not the intention, but it seems, inadvertently I'm sure, to reflect the tactic of conspicuously stating someone is not guilty of some act as a means of starting a contrary rumour.

So, I would like to make it absolutely clear, without any sense of ambiguity, that, certainly to the very best of my knowledge, there is absolutely no reason to suspect that Prof. Theodorescu falsified his academic credentials using red crayons and recycled cereal packets.

Work cited:

Abdel-Hafiz, H.A., Schafer, J.M., Chen, X. et al. Y chromosome loss in cancer drives growth by evasion of adaptive immunity. Nature (2023). https://doi.org/10.1038/s41586-023-06234-x
Blank, C. U., Haining, W. N., Held, W., Hogan, P. G., Kallies, A., Lugli, E., . . . Zehn, D. (2019). Defining 'T cell exhaustion'. Nature Reviews Immunology, 19(11), 665-674. https://doi.org/10.1038/s41577-019-0221-9
Darvin, P., Toor, S. M., Sasidharan Nair, V., & Elkord, E. (2018). Immune checkpoint inhibitors: recent progress and potential biomarkers. Experimental & Molecular Medicine, 50(12), 1-11. https://doi.org/10.1038/s12276-018-0191-1
Fredholm , S., Willerslev-Olsen, A., Met, O., Kubat, L., Gluud, M., Mathiasen, S. L., . . . Ødum, N. (2018). SATB1 in Malignant T Cells. Journal of Investigative Dermatology, 138(8), 1805-1815. https://doi.org/https://doi.org/10.1016/j.jid.2018.03.1526
Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568. (Download a copy of the paper)
Vinay, D. S., Ryan, E. P., Pawelec, G., Talib, W. H., Stagg, J., Elkord, E., . . . Kwon, B. S. (2015). Immune evasion in cancer: Mechanistic basis and therapeutic strategies. Seminars in Cancer Biology, 35, S185-S198. https://doi.org/https://doi.org/10.1016/j.semca n cer.2015.03.004
Yi, J. S., Cox, M. A., & Zajac, A. J. (2010). T-cell exhaustion: characteristics, causes and conversion. Immunology, 129(4), 474-481. https://doi.org/10.1111/j.1365-2567.2010.03255.x

Notes:

¹ Any communication of science will inevitably have to assume some background. In teaching, we can use conceptual analysis to break down any topic and identify pre-requisite prior knowledge that will be needed before introducing new information. Science education builds up understanding slowly over many years, 'building on' what learners have already been taught. Anyone asked to give an account or explanation to a general audience has to make an informed judgement of where it is reasonable to start.

² It might seem that the cells of females are 'Y-negative' as these do not usually contain Y chromosomes. However, from the context (the discussion of loss of, or incomplete, Y-chromosomes) the term is being used to refer to cells with no Y chromosomes that derived ultimately (by imperfect copying) from a cell which did have a Y chromosome. That is, this is a feature of tumours in men.

Although women do not (usually) have Y chromosomes, it is sometimes suggested that the man's Y chromosome can be considered an incomplete X chromosome, so in a sense all men might be considered as incomplete, imperfect women, as some readers might have long suspected.

³ This is not meant as some kind of criticism, but rather an observation on one of the affordances of language in use. It is very useful for the scientist to package up an idea (here, the loss of the Y chromosome from a cell's set of nuclear chromosomes) in a new term or acronym, which can then be put to work as a neologism, thus simplifying sentence structure. The reader then needs to decode this new term in various contexts. That is perfectly reasonable within the genre of research reports (as this only adds minimally to the interpretative load of a specialist reader who is likely to have strong enough background to have capacity to readily make sense of the new term in various contexts). So, in the published paper (Abdel-Hafiz, 2023), we find, inter alia,

"…LOY correlates with…"
"…naturally occurring LOY mutant bladder cancer cells…"
"In ageing men, LOY has been associated with many adverse health consequences."
"…cancer cells with LOY…"
"…mouse tumours with LOY…"
"…human bladder cancer specimens with LOY…"
"…LOY is present early in disease progression…"
"…the lack of Y chromosome gene expression in the MB49 sublines was due to LOY"
"…the important role of these two genes in conferring the LOY phenotype…"
"…patients with LOY had a reduced overall survival following surgery…"
"…tumours with LOY grew more aggressively…"
"…the mechanism of LOY-driven tumour evasion…"

There is even a case of LOY being taken as a sufficiently familiar to be compounded into a further acronym, 'MADLOY':

"we used TCGA DNA sequencing data and mosaic alteration detection for LOY (MADLOY) to detect LOY".

⁴ Unfortunately, thinking anthropomorphically about viruses, cells, molecules, etc., can become a habit of mind. Students may come to see such anthropomorphisms as having the status of genuine scientific explanations (that they can use in exams, for example). Therefore, care is needed with using anthropomorphism in science teaching (Taber & Watts, 1996).

Read about anthropomorphism and science learning

⁵ So, we might suggest that

'checkpoints' is a recently deceased metaphor, with its new meaning only familiar in the technical language community of oncologists and cognate specialists, whereas
'sits' is a long dead metaphor as its broader meaning is likely to be understood widely within the natural language community of English speakers.

⁶ My use of 'because' is not to be read in a teleological sense as

~~immune cells have evolved in order to protect the organism from 'foreign' cells~~
~~the checkpoints have evolved in order to prevent the immune cells destroying cells form the same individual organism~~

Rather in the sense of the reason something has evolved is because it has a property that offers an advantage, and so was selected for:

immune cells have evolved because they were selected for because they protect the organism from 'foreign' cells
the checkpoints have evolved because they were selected for because they prevent the immune cells destroying cells from the same individual organism

⁷ I am making an 'ontological judgement'. I might say I am doing ontology. In my teaching of graduate students I found some were wary of terms like ontology and epistemology, but actually I would argue that we all 'do ontology' every time we make a judgement about the kind of entity something is (and we do epistemology every time we make a judgement about the likely truth value of some claim).

If you judge that fairies are imaginary or that dinosaurs are extinct, I suggest that you are doing ontology. For that matter, if you judge that fairies and dinosaurs are alive and well, and live at the bottom of your garden, then you are also doing ontology – if perhaps not so well.

Read about ontology

How to avoid birds of prey

…by taking refuge in the neutral zone

Keith S. Taber

Fact is said to be stranger than (science) fiction

Regular viewers of Star Trek may be under the impression that it is dangerous to enter the neutral zone between the territories claimed by the United Federation of Planets and that of the Romulan Empire in case any incursion results in an attack by a Romulan Bird of Prey.

A bird of prey (with its prey?)
(Image by Thomas Marrone, used by permission – full-size version at the source site here)

However, back here on earth, it may be that entering the neutral zone is actually a way of avoiding an attack by a bird of prey

A bird of prey (with its prey). Run rabbit, run rabbit…*into the neutral zone*
(Image by Ralph from Pixabay)

At least, according to the biologist Jakob von Uexküll

"All the more remarkable is the observation that a neutral zone insinuates itself between the nest and the hunting ground of many raptors, a zone in which they seize no prey at all. Ornithologists must be correct in their assumption that this organisation of the environment was made by Nature in order to keep the raptors from seizing their own young. If, as they say, the nestling becomes a branchling and spends its days hopping from branch to branch near the parental nest, it would easily be in danger of being seized by mistake by its own parents. In this way, it can spend its days free of danger in the neutral zone of the protected area. The protected area is sought out by many songbirds as a nesting and incubation site where they can raise their young free of danger under the protection of the big predator."
Uexküll, 1934/2010

This is a very vivid presentation, but is phrased in a manner I thought deserved a little interrogation. It should, however, be pointed out that this extract is from the English edition of a book translated from the original German text (which itself was originally published almost a century ago).

A text with two authors?

Translation is a process of converting a text from one natural language to another, but every language is somewhat unique regarding its range of words and word meanings. That is, words that are often considered equivalent in different language may have somewhat different ranges of application in those languages, and different nuances. Sometimes there is no precise translation for a word, and a single word in one language may have several near-equivalents in another (Taber, 2018). Translation therefore involves interpretation and creative choices.

So, translation is a skilled art form, and not simply something that can be done well by algorithmically applying suggestions in a bilingual dictionary. A good translation of an academic text not only requires someone fluent in both languages, but also someone having a sufficient understanding of the topic to translate in the best way to convey the intended meaning rather than simply using the most directly equivalent words. A sequence of the most equivalent individual words may not give the best translation of a sentence, and indeed when translating idioms may lead to a translation with no obvious meaning in the target language. It is worth bearing in mind that any translated text has (in effect) two authors, and reflects choices made by the translator as well as the original author.

Read about the challenges of translation in research writing

I am certainly not suggesting there is anything wrong with the translation of Uexküll's text, but it should be born in mind I am commenting on the English language version of the text.

A neutral zone insinuates itself

No it does not.

The language here is surely metaphorical, as it implies a deliberate action by the neutral zone. This seems to anthropomorphise the zone as if it is a human-like actor.

Read about anthropomorphism

The zone is a space. Moreover, it is not a space that is in any way discontinuous with the other space surrounding it – it is a human conception of a region of space with imagined boundaries. The zone is not a sentient agent, so it can not insinuate itself.

Ornithologists must be correct

Science develops theoretical knowledge which is tested against empirical evidence, but is always (strictly) provisional in that it should be open to revisiting in the light of further evidence. Claims made in scientific discourse should therefore be suitable tentative. Perhaps

ornithologists seem to be correct in suggesting…, or
it seems likely that ornithologists were correct when they suggested…or even
at present our best understanding reflects the suggestions made by ornithologists that...

Yet a statement that ornithologists must be correct implies a level of certainty and absoluteness that seems inconsistent with a scientific claim.

Read about certainty in accounts of science

The environment was made by Nature in order to…

This phrasing seems to personify Nature as if 'she' is a person. Moreover, this (…in order to…) suggests a purpose in nature. This kind of teleological claim is often considered inappropriate in science as it suggests natural events occur according to some pre-existing plan rather than unfolding according to natural laws. ¹ If we consider something happens to achieve a purpose we seem to not need to look for a mechanism in terms of (for example) forces (or entropy or natural selection or…).

Read about personification of nature

Read about teleology in science

Being seized by mistake

We can understand that it would decrease the biological fitness of a raptor to indiscriminately treat its own offspring as potential food. There are situations when animals do eat their young, but clearly any species that's members committed considerable resources to raising a small number of young (e.g., nest building, egg incubation) but were also regular consumers of those young would be at a disadvantage when it came to its long-term survival.

So, in terms of what increases a species' fitness, avoiding eating your own children would help. If seeking a good 'strategy' to have descendants, then, eating offspring would be a 'mistake'. But the scientific account is not that species, or individual members of a species, seek to deliberately adopt a strategy to have generations of descendants: rather behaviour that tends to lead to descendants is self-selecting.

Just because humans can reflect upon 'our children's children's, children', we cannot assume that other species even have the vaguest notions of descendants. (And the state of the world – pollution, deforestation, habitat destruction, nuclear arsenals, soil degradation, unsustainable use of resources, etcetera – strongly suggests that even humans who can conceptualise and potentially care about their descendants have real trouble making that the basis for rational action.)

Even members of the very rare species *capable of conceptualising a future for their offspring* struggle to develop strategies taking the well-being of future generations into account.
(Image: cover art for '***To our children's children's children***' {The Moody Blues}).

Natural selection is sometimes seen as merely a tautology as it seems to be a theory that explains the flourishing of some species (and not others) in terms that they have the qualities to flourish! But this is to examine the wrong level of explanation. Natural selection explains in general terms why it is that in a particular environment competing species will tend to survive and leave offspring to different extents. (Then within that general framework, specific arguments have to be made about why particular features or behaviours contribute to differential fitness in that ecological context.)

Particular evolved behaviours may be labelled as 'strategies' by analogy with human strategies, but this is purely a metaphor: the animal is following instincts, or sometimes learned behaviours, but is not generally following a consciously considered plan intended to lead to some desired outcome in the longer term.

But a reader is likely to read about a nestling being "in danger of being seized by mistake by its own parents" as the birds themselves making a mistake – which implies they have a deliberate plan to catch food, while excluding their own offspring from the food category, and so intended to avoid treating their offspring as prey. That is, it is implied that birds of prey are looking to avoid eating their own, but get it wrong.

Yet, surely, birds are behaving instinctively, and not conceptualising their hunting as a means of acquiring nutrition, where they should discriminate between admissible prey and young relatives. Again this seems to be anthropomorphism as it treats non-human animals as if their have mental experiences and thought processes akin to humans: "I did not mean to eat my child, I just failed to recognise her, and so made a mistake".

The protected area is sought out

Similarly, the songbirds also behave instinctively. They surely do not 'seek out' the 'protected' area around the nest of a bird of prey. There must be a sense in which they 'learn' (over many generations, perhaps) that they need not fear the raptors when they are near their own nests but it seems unlikely a songbird conceptualises any of this in a way that allows them to deliberately (that is, with deliberation) seek out the neutral zone.

In terms of natural selection, a songbird that has no fear of raptors and so does not seek to avoid or hide or flee from them would likely be at a disadvantage, and so tend to leave less offspring. Similarly, a songbird that usually avoided birds of prey, but nested in the neutral zone, would have a fitness advantage if other predators (small cats say) kept clear of the area. The bird would not have to think "hey, I know raptors are generally a hazard, but I'll be okay here as I'm close enough to be in the zone where they do not hunt", as long as the behaviour was heritable (and there was initially variation in the extent to which individuals behaved that way) – as natural selection would automatically lead to it becoming common behaviour.

(In principle, the bird could be responding to some cue in the environment that was a reliable but indirect indicator they were near a raptor nesting site. For example, perhaps building a nest very close to a location where there is a regular depositing of small bones on the ground gives an advantage, so this behaviour increases fitness and so is 'selected'.)

Under the protection of the big predator

Why are the songbirds under the protection of the raptors? Perhaps because other potential predators do not come into the neutral zone as they are vulnerable when approaching this area, even if they would be safe once inside. Again, if this is so, it surely does not reflect a conscious conceptualisation of the neutral zone.

For example, a cat that preys on small birds would experience a different 'unwelt' from the bird. A small songbird with a nest where it has young experiences the surrounding space differently to a cat (already a larger animal so experiencing the world at a different scale) that ranges over a substantial territory. Perhaps the songbird perceives the neutral zone as a distinct space, whereas to the cat it is simply an undistinguished part of a wider area where the raptors are regularly seen.

Or, perhaps, for the smaller predator, the area around the neutral zone offers too little cover to risk venturing into the zone. (Again, this does not mean a conscious thinking process along the lines "I'd be safe once I was over there, but I'm not sure I'd make it there as I could easily be seen moving between here and there", but could just be an inherited tendency to keep under cover.)

The birds of prey themselves will not take the songbirds, so the smaller birds are protected from them in the zone, but if this is simply an evolved mechanism that prevents accidental 'infanticide' this can hardly be considered as other birds being under the protection of the birds of prey. Perhaps the birds of prey do scare away other predators – but, if so, this is in no sense a desired outcome of a deliberate policy adopted by the birds of prey because they want to protect their more vulnerable neighbours.

One could understand how the birds of prey might hypothetically have evolved behaviour of not preying on smaller birds (which might include their own offspring) near their nest, but would still attack smaller predators that might threaten their own chicks. In that scenario ², the birds of prey might have indeed protected nearby songbirds from potential predators (even if only incidentally), but this does not apply if, as Uexküll suggests, "they seize no prey at all" in the neutral zone.

Again the, 'under the protection of the big predator' seems to anthropomorphise the situation and treat the birds of prey as if they are acting deliberately to protect songbirds, and so this phrasing needs to be understood metaphorically.

Does language matter?

Uexküll's phrasing offers an engaging narrative which aids in the communication of the idea of the neutral zone to his readers. (He is skilled in making the unfamiliar familiar.) It is easier to understand an abstract idea if it seems to reflect a clear purpose or it can be understood in terms of human ways of thinking and acting, for example:

it is important to keep your children safe
it is good to look out for your neighbours

But we know that science learners readily tend to accept explanations that are teleological and/or anthropomorphic, and that sometimes (at least) this acts as an impediment to learning the scientific accounts based on natural principles and mechanisms.

Therefore it is useful for science teachers in particular to be alert to such language so they can at least check that learners are seeing beyond the metaphor and not mistaking a good story for a scientific account.

Work cited:

Taber, K. S. (2018). Lost and found in translation: guidelines for reporting research data in an 'other' language. Chemistry Education Research and Practice, 19, 646-652 doi:10.1039/C8RP90006J [Free access]
Uexküll, J. v. (1934/2010). A Foray into the Worlds of Animals (J. D. O'Neil, Trans.). In A Foray into the Worlds of Animals; with, A Theory of Meaning (pp. 39-135). University of Minnesota Press.

Notes:

¹ Many people, including some scientists, do believe the world is unfolding according to a pre-ordained plan or scheme. This would normally be considered a matter of religious faith or at least a metaphysical commitment.

The usual stance taken in science ('methodological naturalism'), however, is that scientific explanations must be based on scientific principles, concepts, laws, theories, etcetera, and must not call upon any supernatural causes or explanations. This need not exclude a religious faith in some creator with a plan for the world, as long as the creator is seen to have set up the world to unfold through natural laws and mechanisms. That is, faith-based and scientific accounts and explanations may be considered to work at different levels and to be complementary.

² That this does not seem to be the case might reflect how a flying bird perceives prey – if it has simply evolved to swoop upon and take any object in a certain size range {that we might explain as small enough to be taken, but not so small as not to repay the effort} that matches a certain class of movement pattern {that we might interpret as moving under its own direction and so being animate} then the option of avoiding smaller birds but taking other prey would not be available.

After all, studies show parent birds will try and feed the most simple representations of a hatchling's open beak – suggesting they do not perceive the difference between their own children and crude models of an open bird mouth.

The general form of a chick's open mouth (as shown by these hatchlings) is enough to trigger feeding behaviour in adult birds.
(Image by Tania Van den Berghen from Pixabay )

Uexküll himself reported that,

"…a very young wild duck was brought to me; it followed me every step. I had the impression that it was my boots that attracted it so, since it also ran occasionally after a black dachshund. I concluded from this that a black moving object was sufficient to replace the image of its mother…"
Uexküll, 1934/2010

(A year later, Lorentz would publish his classic work on imprinting which reported detailed studies of the same phenomenon.)

What the jet tried to do next…

Anthropomorphising surface tension

Keith S. Taber

it seems good training for a scientist to always read accounts of science with a critical filter primed to notice figurative language and to check that the communication can be understood in a non-metaphorical way

When water is poured from a bottle or other container the stream of liquid can take up complex shapes. In particular, it has long been noted how the stream can appear to have the shape of a chain or string of beads, with the flow seeming to be wider in some places that others.

A stream of poured water does not form a perfect cylinder – something that physics should be able to explain.

(Image by tookapic from Pixabay)

This is just the kind of thing that physicists think they should be able to explain…using physics. An article in Physics World (Jarman, 2022) reports some recent work on just this outstanding problem,

"If you pour water out of a bottle, the liquid stream will often adopt a chain-like structure….At the heart of the effect is the non-cylindrical profile of the jet as it emerges. To minimize surface tension, the jet tries to become a cylinder, but this motion overshoots and results in an oscillation in the profile shape."
Article in Physics World

What intrigued me here was the choice of phrasing: "To minimize surface tension, the jet tries to become a cylinder…". This language could be considered to reflect teleology, and even anthropomorphism.

Teleology?

Teleological explanations are those that explain something in terms of some kind of endpoint. Something happens in order to bring about some specific state of affairs. The sun shines to allow us to find our way. Plants produce oxygen so we can breathe. That is, there is seen to be purpose in nature, something that is characteristic of mythical and supernatural thinking. In science, teleological explanations are strictly considered a kind of pseudo-explanation – something that has the form of an explanation, but does not really explain anything. Sometimes we find apparently teleological explanations in science because they are being used as a kind of shorthand. For example, if we know that science suggests entropy always increases in processes, we might interpret a scientist's comment that something happens 'in order to increase entropy' to be a loose (or lazy) way of saying that some suggested mechanism or action is considered likely because it is consistent with the assumption that entropy will increase.

Read about pseudo-explanations

Read about teleology in science

Here it is suggested that the odd shape is formed in order "to" minimise surface tension. Scientists have observed that many phenomena (such as rain forming roundish drops) can be explained in terms that surface tension tends to be minimised (cf. entropy tends to increase, objects tend to roll down hills, people tend to get older). But the language here might suggest minimising surface tension is an end that nature seeks – that would be a teleological explanation.

Although perhaps this is not simple teleology, as it is not that the water forms into the shape it does to minimise surface tension, but something more nuanced is going on – the jet of water is actively trying, but not quite managing, to minimise surface tension.

anthropo… (to do with humans, as in anthropology)
…morphism (to do with form, as in morphology, amorphous)

…and anthropomorphism?

Anthropomorphic language refers to non-human entities as if they have human experiences, perceptions, and motivations. Both non-living things and non-human organisms may be subjects of anthropomorphism. Anthropomorphism may be used deliberately as a kind of metaphorical language that will help the audience appreciate what is being described because of its similarly to some familiar human experience. In science teaching, and in public communication of science, anthropomorphic language may often be used in this way, giving technical accounts the flavour of a persuasive narrative that people will readily engage with. Anthropomorphism may therefore be useful in 'making the unfamiliar familiar', but sometimes the metaphorical nature of the language may not be recognised, and the listener/reader may think that the anthropomorphic description is meant to be taken at face value. This 'strong anthropomorphism' may be a source of alternative conceptions ('misconceptions') of science.

Read about anthropomorphism

So, in our present case, we are told that "the "the jet tries to become a cylinder". This is anthropomorphic, as to try to do something means having a goal in mind and deliberately behaving in a way that it is believed, expected, or – at least – hoped, will lead to that goal. Human beings can try to achieve things. We can perceive our environment, have goals, conceptualise possibilities and means to reach them, and put in practice an intention.

Whether, and, if so, which, animals can try to do things rather than simply following evolved instincts is a debated issue.

Does a dog try to please its human companion by bringing the newspaper?
Does the dolphin try to earn a fish by jumping through a hoop? Perhaps.
Does the salmon try to get to a suitable spawning site ('ground', sic) by swimming upstream?
Does the spider try to make a symmetrical web?
Does the bee try to collect nectar by visiting flowers. Probably not.
Does she try to fertiliser those flowers with pollen to ensure there will be flowers for her to visit in future seasons? Almost certainly not!

Jets of water?

Do jets of water think that being cylindrical is desirable (perhaps because they recognise minimal surface tension as an inherent good?) , and so make efforts to bring this about? Clearly not. So, they do not try to do this. They do not try to do anything. They are not the kind of entities that can try.

So, this language is metaphorical. The reader is meant to read that "the jet tries to become a cylinder" to mean something other than "the jet tries to become a cylinder". Now, often figures of speech are used in science communication because the ideas being communicated are abstract and complex, and metaphorical language that describes the science in more familiar terms makes the text more accessible and increases engagement by the audience/readership.

A question here then, is what "the jet tries to become a cylinder" communicates that was more likely to be inaccessible to the reader. Physics World is the house magazine of the Institute of Physics, which means it is sent to all it members working across all areas of physics. So a broad readership, though largely a readership of physicists.

Tracing the stream back to the source

Another question that occurred to me was whether the reporter (Jarman) was simply reporting the original researchers' (Jordan, Ribe, Deblais and Bonn) ways of communicating their work. That report was in an academic journal, Physical Review Fluids, where formal, technical language would be expected. So, I looked up the paper, to see how the work was described there.

Under a heading of 'phenomenology', Jordan and colleagues explain

"Chain oscillations are most readily observed when the viscosities of the jet and the ambient fluid are low and the interface has a high surface tension. Water jets in air satisfy these criteria, and so it is no surprise that chain oscillations occur in many everyday situations. Deformation and vibration of a jet are capillary phenomena in which surface tension acts to reduce the jet's surface area. If the cross section is not circular, its highly curved portions are pulled inward and its weakly curved portions pushed outward relative to a circular section with the same area. But due to inertia the movement overshoots, with the result that the long and short axes of the section are interchanged. The shape of the section therefore evolves as it moves along the axis of the jet, producing a steady liquid chain when observed in the laboratory frame…"
Jordan, Ribe, Deblais & Bonn, 2022

"The shape of the section therefore evolves as it moves along the axis of the jet, producing a steady liquid chain when observed"

(Image by Kevin Phillips from Pixabay)

(This seemed to be a somewhat different meaning of 'phenomenology' to that sometimes used in science education or social science more generally. Phenomenology looks to explore how people directly experience and perceive the world. Jordan and colleagues include here a good deal of re-conceptualisation and interpretation of what is directly observed. ¹ )

The effect Jordan and colleagues describe seems analogous to how a pendulum bob that is released and so accelerated (by gravity) towards the point directly beneath its support (where gravitational potential is minimised) acquires sufficient momentum to overshoot, and swing upwards, beginning an oscillatory motion. Something similar is seen in an ammeter where the needle often overshoots, and initially oscillates around the value of a steady current reading (unless the spring is 'critically damped'). The effect is also made use on in striking a tuning fork.

No need to try

There is no mention here of 'trying', so no clear anthropomorphism. So, this was a gloss added in the report in Physics World, perhaps because anthropomorphic narratives are especially engaging and readily accepted by audiences; perhaps because the reporter needed to rephrase so as not to borrow too much of the original text, or perhaps as part of preparing brief copy to an editorially assigned word length. Or, perhaps Sam Jarman was not even conscious of the anthropomorphism being used, as this seems such a natural way to communicate. ²

Surface tension acting up

Did the original authors avoid teleology? They do write about how "surface tension acts to reduce the jet's surface area?" This could be read as teleological – as there seems to be a purpose or goal in the 'action', even if it is not here presented as a premeditated action. Could any suggestions of such a purpose be avoided?

One response might be that, yes, a physicist might suggest the 'true' description is a mathematical formula (and there are plenty of formulae in Jordan et al's paper) and that a verbal description is necessarily the translation of an objective description into an inherently figurative medium (natural language).

And, of course, this is not some special case. We might read that gravity acts to pull something to the ground or air resistance acts to slow a projectile down and so forth. 'To' may just imply a cause of an outcome, not a purpose.

I think a rewording along the lines "the action of the surface tension reduces the jet's surface area"conveys the same meaning, but is more of a neutral description of a process, avoiding any suggestion that there is a purpose involved.

Reading and interpreting

But does this matter? In teaching young people such as school children, there is evidence that some figurative language that is anthropomorphic or teleological may be understood in those terms, and student thinking may later reflect this. Part of science education is offering learners an insight into how science does seek to (oh, science personified: sorry, scientists seek to) describe in neutral terms and not to rely on nature having inherent goals, or comprising of the actions of sentient and deliberate agents.

The readership of Physics World is however a professional audience of members of the community of inducted physicists who are well aware that, actually, surface tension does not try to do anything; and that minimising surface tension is a common observed pattern, not something set out as a target for physical systems to aim for. These physicists are unlikely to be led astray by the engaging prose of Sam Jarman and will fully appreciate the intended meaning.

That said, there is an intimate bidirectional relationship between our thinking and our speech – our speech reflects our thought pattens, but our language also channels our thinking. So, it seems good training for a scientist to always read accounts of science with a critical filter primed to notice figurative language and to check that the communication can be understood in a non-metaphorical way. That includes checking that our understanding of what we have read is in keeping with scientific commitments to exclude explanations that are framed in terms of nature's end goals, or the deliberate agency of non-sentient 'actors'.

Jarman, S. (2022). Flowing liquid 'chains' are best described by Niels Bohr, not Lord Rayleigh. Physics World, 35(12).
Jordan, D. T. A., Ribe, N. M., Deblais, A., & Bonn, D. (2022). Chain oscillations in liquid jets. Physical Review Fluids, 7(10), 104001. doi:10.1103/PhysRevFluids.7.104001

Notes

¹ However, none of us are able to be completely naive observers of the world. As William James long ago pointed out, the un-mediated sensory experience of a newborn is a chaos of noise and shapes and colours and so on. Even recognising another person or the presence of a table is an act of interpretation that we learn.

So, experts in a field do see things others do not. A field palaeontologist sees a fossil fragment where the rest of us see undifferentiated dirt and stones. The biochemist sees a steroid structure in a patterns of lines. The football pundit sees a 4-4-2 formation where the occasional viewers just sees people running around. The experienced poker player sees a 'tell' that others would not notice. The professional musician hears a passage in E minor, when most of us just hear a tune.

² This kind of language reflects a way of thinking and talking often called 'the natural attitude'. Science can be seen in part as a deliberate move to look beyond the common-sense world of the natural attitude to problematise phenomena that might be readily taken as given.

We may get used to, and simply accept, that ice is cold, fire burns, the Lord/King makes decisions and owns the land (and people!), rivers flow, things fall down, the heretic must die, the sun moves across the sky, etc. – and probably most people did for much of human history – where the critical (scientific) attitude is to always ask 'why?'

The complicated social lives of stars

Stealing, escaping, and blowing-off in space

Keith S. Taber

"After a lecture on cosmology and the structure of the solar system, James [William James] was accosted by a little old lady.

'Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it's wrong. I've got a better theory,' said the little old lady.

'And what is that, madam?' inquired James politely.

'That we live on a crust of earth which is on the back of a giant turtle.'

Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command, James decided to gently dissuade his opponent by making her see some of the inadequacies of her position.

'If your theory is correct, madam,' he asked, 'what does this turtle stand on?'

'You're a very clever man, Mr. James, and that's a very good question,' replied the little old lady, 'but I have an answer to it. And it's this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him.'

'But what does this second turtle stand on?' persisted James patiently.

To this, the little old lady crowed triumphantly,

'It's no use, Mr. James – it's turtles all the way down.'
Ross, 1967, iv

"The Hindoos [sic] held the earth to be hemispherical, and to be supported like a boat turned upside down upon the heads of four elephants, which stood on the back of an immense tortoise. It is usually said that the tortoise rested on nothing, but the Hindoos maintained that it floated on the surface of the universal ocean. The learned Hindoos, however, say that these animals were merely symbolical, the four elephants meaning the four directions of the compass, and the tortoise meaning eternity." (*The Popular Science Monthly*, March, 1877; image via Wikipedia)

It's metaphors all the way down

A well-known paper in the journal 'Cognitive Science' is entitled 'The metaphorical structure of the human conceptual system' (Lakoff & Johnson, 1980). What the authors meant by this was that metaphor, or perhaps better analogy, was at the basis of much of our thinking, and so our language.

This links to the so-called 'constructivist' perspective on development and learning, and is of great significance in both the historical development of science and in science teaching and learning. Consider some of the concepts met in a science course (electron, evolution, magnetic flux, hysteresis, oxidation state, isomerism…the list is enormous) in comparison to the kind of teaching about the world that parents engage in with young children:

That is a dog
That is a tree
That is round
This is hot
This is aunty
etc.

Pointing out the names of objects is not a perfect technique – just as scientific theories are always underdetermined by the available data (it is always possible to devise another scheme that fits the data, even if such a scheme may have to be forced and convoluted), so the 'this' that is being pointed out as a tree could refer to the corpse of trees, or the nearest branch, or a leaf, or this particular species of plant, or even be the proper name of this tree, etc. ¹

Pointing requires the other person to successfully identify what is being pointed at
(Images by Joe {background} and OpenClipart-Vectors {figures} from Pixabay)

But, still, the 'this' in such a case is usually more salient than the 'this' when we teach:

This is an electron
This is reduction
This is periodicity
This is electronegativity
This is a food web
This is a ᴨ-bond
This is a neurotransmitter
etc.

Most often in science teaching we are not holding up a physical object or passing it around, but offering a 'this' which is at best a model (e.g., of a generalised plant cell or a human torso) or a complex linguistic structure (a definition in terms of other abstract concepts) or an abstract representation ('this', pointing to a slope of an a graph, is acceleration; 'this', pointing to an image with an arrangement of a few letters and lines, is a transition state…).

So, how do we bridge between the likes of dogs and trees on one hand and electrons and the strong nuclear force on the other (so to speak!)? The answer is we build using analogy and we talk about those constructions using a great deal of metaphor.² That is, we compare directly, or indirectly, with what we can experience. This refers to relationships as well as objects. We can experience being on top of, beneath, inside, outside, next to, in front of, behind, near to, a long way from (a building, say – although hopefully not beneath in that case), and we assign metaphorical relationships in a similar way to refer to abstract scenarios. (A chloroplast may be found in a cell, but is sodium found in (or on) the periodic table? Yes, metaphorically. And potassium is found beneath it!)

In a wall, the bricks on the top layer are supported by the bricks in the layer beneath – but those are in turn supported by those beneath them.

In building, we have to start at the foundations, and build up level by level. The highest levels are indirectly supported by the foundations.

(Image by OpenClipart-Vectors from Pixabay)

In science, we initially form formal concepts based on direct experience of the world (including experience mediated by our interventions, i.e., experiments), and then we build more abstract concepts from those foundational concepts, and then we build even more abstract concepts by combining the abstract ones. In the early stages we refine 'common sense' or 'life-world' categories into formal concepts so we can more 'tightly' (and operationally, through standard procedures) define what count as referents for scientific terms (Taber, 2013). So, the everyday phenomenon of burning might be reconceptualised as combustion: a class of chemical reactions with oxygen.

This is not just substituting a technical term, but also a more rigid and theoretical (abstract) conceptualisation. So, in the 'life-world' we might admit the effects of too much sunshine or contact with a strong acid within the class of 'burning' by analogy with the effect of fire (it hurts and damages the skin); but the scientific categorisation is less concerned with direct perception, and more with explanation and mechanism. So, iron burning in chlorine (in the absence of any oxygen) is considered combustion, but an acid 'burn' is not.

Combustion without oxygen: A Royal Society of Chemistry video demonstrating the reactions of iron with the halogens.

This is what science has done over centuries, and is also what happens in science education. So, one important tool for the teacher is concept analysis, where we check which prerequisite concepts need to be part of a student's prior learning before we introduce some new concept that is built upon then (e.g., do not try to teach mass spectroscopy before teaching about atomic structure, and do not teach about atomic structure before introducing the notion of elements; do not try to teach about the photoelectric effect to someone who does not know a little about the structure of metals and the nature of electromagnetic radiation.)

This building up of abstract concepts, one on another, is reflected in the density of metaphor we find in our language. (That is a metaphorical 'building', metaphorically placed one upon another, with a metaphorical 'density' which is metaphorically 'inside' the language and which metaphorically 'reflects' the (metaphorical) building process! You can 'see' (a metaphor for understand) just how extensive (oops, another metaphorical reference to physical space) this is. Hopefully, the (metaphorical) 'point' is (metaphorically) 'made', and so I am going to stop now, before this gets silly. ³

A case study of using language in science communication: the death of stars

Rather, I am going to discuss some examples of the language used in a single science programme, a BBC radio programme/podcast in the long-running series 'In Our Time' that took as its theme 'The Death of Stars'. The programme was hosted by Melvyn Bragg, and The Lord Bragg's guests were Professors Carolin Crawford (University of Cambridge), the Astronomer Royal Martin Rees (University of Cambridge) and Mark Sullivan (University of Southampton). This was an really good listen (recommended to anyone with an interest in astronomy), so I have certainly not picked it out to be critical, but rather to analyse the nature of some of the language used from the perspective of how that language communicates technical ideas.

An episode of 'In Our Time' on 'The Death of Stars'
"The image above is of the supernova remnant Cassiopeia A, approximately 10,000 light years away, from a once massive star that died in a supernova explosion that was first seen from Earth in 1690"

A science teacher may be familiar with stars being born, living, and dying – but how might a young learner, new to astronomical ideas, make sense of what was meant?
The passing of stars: birth, death, and afterlife in the universe

The lives and deaths of stars

Now there is already a point of interest in the episode title. Are stars really the kind of entities that can die? Does this mean they are living beings prior to death?

There are a good many references in the talk of these three astronomers in the episode that suggests that, in astronomy at least, stars do indeed live and die. That is, this does not seem to be consciously used as a metaphor – even if the terminology may have initially been introduced that way a long time ago. The programme offered so much material on this theme, that I have separated it out for a post of its own:

"So, in the language of astronomy, stars are born, start young, live; sometimes living alone but sometimes not, sometimes have complicated lives; have lifetimes, reach the end of their lives, and die, so, becoming dead, eventually long dead; and indeed there are generations of stars with life-cycles."
The passing of stars: birth, death, and afterlife in the universe

In this post I am going to consider some of the other language used.

Making the unfamiliar familiar

Language is used in science communication to the public, as it is in teaching, to introduce abstract technical ideas in ways that a listener new to the subject can make reasonable sense of. The constructivist perspective on learning tells us that meaning is not automatically communicated from speaker (or author or teacher) to listener (or reader or student). Rather, a text (spoken or written, or even in some other form – a diagram, a graph, a dance!) has to be interpreted, and this relies on the interpretive resources available to the learner. ⁴ The learner has to relate the communication to something familiar, and the speaker can help by using ways to make the new idea seem like something already familiar.

Read about constructivism in education

This is why it it is so common in communicating science to simplify, to use analogies and similes, to gesture, to use anthropomorphism and other narrative devices. There was a good deal of this in the programme, and I expect I have missed some examples. I have divided my examples into

simplifications: where some details are omitted so not to overburden the listener;
anthropomorphism: where narratives are offered such that non human entities are treated as if sentient actors, with goals, that behave deliberately;
analogies where an explicit comparison is made to map a familiar concept onto the target concept being introduced; ⁵
similes and metaphors: that present the technical material as being similar to something familiar and everyday.

Simplification

Simplification means ignoring some of the details, and offering a gloss on things. The details may be important, but in order to get across some key idea it is introduced as a simplification. Progress in understanding would involve subsequently filling in some details to develop a more nuanced understanding later.

In teaching there are dangers in simplification, as if the simplified idea is readily latched onto (e.g., there are two types of chemical bonds: ionic and covalent) it may be difficult later to shift learners on in their thinking. This may mean that there is a subtle balance to be judged between

giving learners enough time to become comfortable with the novel idea as introduced in a simplified form,

and

seeking to develop it out into a more sophisticated account before it become dogma.

In a one-shot input, such as a public lecture or appearance in the media, the best a scientist may be able to do is to present an account which is simple enough to understand, but which offers a sense of the science.

Simplification: all elements/atoms are formed in stars

When introducing the 'In Our Time' episode, Lord Bragg suggested that

"…every element in our bodies, every planet, was made in one of those stars, either as they burned, or as they exploded".

Clearly Melvyn cannot be an expert on the very wide range of topics featured on 'In our time' but relies on briefing notes provided by his guests. Later, in the programme he asks Professor Rees (what would clearly be considered a leading question in a research context!) "Is the sun recycled from previous dead stars?"

"Yes it is because we believe that all pristine material in the universe was mainly just hydrogen and helium, and all the atoms we are made of were not there soon after the big bang. They were all made in stars which lived and died before our solar system formed. And this leads to the problem of trying to understand more massive stars which have more complicated lives and give rise to supernovae…

The cloud from which our solar system formed was already contaminated by the debris, from earlier generations of massive stars which had lived and died more than say five billion years ago so we're literally the ashes of those long dead stars or if you are less romantic we're the nuclear waste from the fuel that kept those old stars shining."
Prof. Martin Rees

There is a potential for confusion here.

"…all the atoms we are made of were not there soon after the big bang. They were all made in stars which lived and died before our solar system formed…"

seems to be meant to convey something like

not all the atoms we are made of were there soon after the big bang.
[Some were, but the rest/others] were all made in stars which lived and died before our solar system formed…

A different interpretation (i.e., that all atoms/elements are formed in stars) might well be taken, given Lord Bragg's introductory comments.

Professor Rees referred to how "…the idea that the elements, the atoms we are made of, were all synthesised in stars…" first entered scientific discourse in 1946, due to Fred Hoyle, and to

"this remarkable discovery that we are literally made of the ashes of long dead stars"
Prof. Martin Rees

Before the first star formation, the only elements present in the universe were hydrogen and helium (and some lithium) and the others have been produced in subsequent high energy nuclear processes. Nuclear fusion releases energy when heavier nuclei are formed from fusing together lighter ones, up to iron (element 56).

Forming even heavier elements requires an input of energy from another source. It was once considered that exploding stars, supernovae, gave rise to the conditions for this, but recently other mechanisms have been considered: and Prof. Sullivan described one of these:"we think these combining neutron stars are the main sites where heavy elements like strontium or plutonium, perhaps even gold or silver, these kinds of elements are made in the universe in these neutron stars combining with each other".

A human body includes many different elements, though most of these in relatively small amounts. Well represented are oxygen, carbon, calcium, and nitrogen. These elements exist because of the processes that occur in stars. However, hydrogen is also found in 'organic' substances such as the carbohydrates, proteins, and fats found in the human body. Typically the molecules of these substances contain more hydrogen atoms than atoms of carbon or any other element.

substance	formula
glucose (sugar)	C₆H₁₂O₆
leucine (amino aid)	C₆H₁₃NO₂
leukotriene B4 (inflammatory mediator)	C₂₀H₃₂O₄
thymine (nucleobase)	C₅H₆N₂O₂
adreneline (hormone)	C₉H₁₃NO₃
insulin (hormone)	C₂₅₇H₃₈₃N₆₅O₇₇S₆
cholesterol (lipid)	C₂₇H₄₆O
cobalamin (vitamin B₁₂)	C₆₃H₈₈CoN₁₄O₁₄P

formulae of some compounds found in human bodies

The body is also said to be about 60% water, and water has a triatomic molecule: two hydrogen atoms to one of oxygen (H₂O). That is, surely MOST of "the atoms we are made of" are hydrogen, which were present in the universe before any stars were 'born'.

So, it seems here we have a simplification ("every element in our bodies…was made in one of those stars, either as they burned, or as they exploded"; "atoms we are made of … were all made in stars") which is contradicted later in the programme. (In teaching, it is likely the teacher would feel the need to draw the learner's attention to how the more detailed information was actually developing an earlier simplification, and not leave a learner to work this out for themselves.)

Simplification: mass is changed into energy

Explaining nuclear fusion, Prof. Crawford suggested that

"Nuclear fusion is when you combine nuclei of elements to form heavier elements, and when you do this there is a loss of mass, which is converted to energy which provides the thermal pressure and that is what counteracts the gravity and stalls the gravitational collapse."
Prof. Carolin Crawford

This seems to reflect a common alternative conception ('misconception') that, in nuclear processes, mass is converted to energy. This is often linked to Albert Einstein's famous equation E = mc².

Actually, as discussed before here, this is contrary to the scientific account. The equation presents an equivalence between mass and energy, but does not suggest they can be inter-converted. In nuclear fusion, the masses of the new nuclei are very slightly less than the masses of the nuclei which react to form them (the difference is known as the mass defect), but this is because this omits some details of the full description of the process. If the complete process is considered then there is no loss of mass, just a reconfiguration of where the mass can be located.

The formation of helium from hydrogen in a star

(Image source: Wikamedia Commons)

Although the ⁴He formed has slightly less mass than four ¹H; the positrons, neutrinos and gamma rays produced all have associated (energy and) mass, so that overall there is conservation of mass.

This is a bit like cooking some rice, and finding that when the rice is cooked the contents of the saucepan had slightly less weight than when we started – as some of the water we began with has evaporated and is no longer registering on our balance. In a similar way, if we consider everything that is produced in the nuclear process, then the mass overall is conserved.

As E = mc² can be understood to tell us that mass follows the energy (or vice versa) we should expect mass changes (albeit very, very small ones) whenever work is done: when we climb the stairs, or make a cup of tea, or run down a mobile 'phone 'battery' (usually a cell?) – but mass is always conserved when we consider everything involved in any process (such as how the 'phone very, very slightly warms -and so very marginally increases the mass of – the environment).

Read 'How much damage can eight neutrons do?'

Despite the scientific principles of conservation of energy and conservation of mass always applying when we make sure we consider everything involved in a process, I have mentioned on this site another example of an astrophysicist suggesting mass can be converted into energy: "an electron and the positron, and you put them together, they would annihilate…they would annihilate into energy" (on a different episode of 'In Our Time': come on Melvyn…we always conserve mass).

Read 'The missing mass of the electron'

Perhaps this is an alternative conception shared by some professional scientists, but I wonder if it sometimes seems preferably to tell the "mass into energy" narrative because it is simpler than having to explain the full details of a process – which is inevitably a more complex story and so will be more difficult for a novice to take in. After all, the "mass into energy" story is likely to seem to fit with a listener's interpretive resources, as E=mc² is such a famous equation that it can be assumed that it will be familiar to most listeners, even if only a minority will have a deep appreciation of how the equivalence works.

Anthropomorphic narratives

In science learning, anthropomorphism is (to borrow a much used metaphor) a double edged sword that can cut both ways. Teachers often find that using narratives that present inanimate entities which are foci of science lessons as if they are sentient beings with social lives and motivations engages learners and triggers mental images that a student can readily remember. So, students may recall learning about what happens at a junction in a circuit in terms of a story about an electron that had to make a decision about which way to go – perhaps she took one branch while her friend tried another? They recall that covalent bonds are the 'sharing' of electrons between atoms, and indeed that atoms want, perhaps even need, to fill their electron shells, and if they manage this they will be happy.

Read about anthropomorphism

The danger here is that for many students such narratives are not simply useful ways to get them thinking about the science concepts (weak anthropomorphism) but seem quite sufficient as the basis of explanations (strong anthropomorphism) – and so it may become difficult to shift them towards more canonical accounts. They will then write in tests that chemical reactions occur because the atoms want full shells, or that only one electron can be removed from a sodium atom because it then has a full shell. (That is, a force applied to an electron in an electric field is seen as irrelevant compared with the atom's desires. These are genuine examples reflecting what students have said.)

However, there is no doubt that framing scientific accounts within narratives which have elements of human experience as social agent does seem to help make these ideas engaging and accessible. Some such anthropomorphism is explicit, such as when gas molecules (are said to) like to move further apart, and some is more subtle by applying terms which would normally be used in relation to human experiences (not being bothered; chomping; escaping…).

What gravity did next

Consider this statement:

"All stars have the problem of supporting themselves against gravitational collapse, whether that is a star like our sun which is burning hydrogen into helium, and thus providing lots of thermal pressure to stop collapse, or whether it is a white dwarf star, but it does not have any hydrogen to burn, because it is an old dead star, fading away, so it has another method to stop itself collapsing and that is called degeneracy pressure. So, although a white dwarf is very dense, gravity is still trying to pull that white dwarf to be even denser and even denser."
Prof. Mark Sullivan

There is an explicit anthropomorphism here: from the scientific perspective gravity is not trying to pull the white dwarf to be even denser. Gravity does not try to do anything. Gravity is not a conscious agent with goals that it 'tries' to achieve.

However, there is also a more subtle narrative thread at work – that a star has the problem of supporting itself, and it seems that when its first approach to solving this problem fails, it has a fallback method "to stop itself collapsing". But the star is just a complex system where various forces act and so processes occur. A star is not the kind of entity that can have a problem or enact strategies to achieve goals. Yet, this kind of language seems to naturally communicate abstract ideas though embedding them within an accessible narrative.

Star as moral agents

In the same way, a star is not the type of entity which can carry out immoral acts, but

"A star like our sun will never grow in mass, because it lives by itself in space. But most stars in the universe don't live by themselves, they live in what are called binary systems where you have two stars orbiting each other, rather than just the single star that we have as the sun. They are probably born with different masses, and so they evolve at different speeds and one will become a white dwarf. Now the physics is a bit complicated, but what can happen, is that that white dwarf can steal material from its companion star."
Prof. Mark Sullivan

The meaning here seems very clear, but again there are elements of using an anthropomorphic narrative. For one star to steal material from another star, that material would have to first belong to that other star, and its binary 'partner' would have to deliberately misappropriate that material knowing it belongs to its 'neighbour' (indeed, "companion").

Such a narrative breaks down on analysis. If we were to accept that the matter initially belongs to the first star (leaving aside for the moment what kind of entities can be considered to own property) then given that the material in a star got to be there through mutual gravitational attraction, the only obvious basis for ownership is that that matter has become gravitationally bound as part of that star.

If we have no other justification than that (as in the common aphorism, possession is nine points of the law), then when the material is transferred to another star because its gravitational field gives rise to a net force causing the matter to become gravitationally bound to a different star, then we should simply consider ownership to have changed. There is no theft in a context where ownership simply depends on pulling with the greater force. Despite this, we readily accept an analogy from our more familiar human social context and understand that (in a metaphorical sense) one star has stolen from another!

Actually, theft can only be carried out by moral agents – those who have capacity to intend to deprive others of their property

"A person [sic] is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it; and "thief" and "steal" shall be construed accordingly"
U.K. Theft Act 1968

Generally, these days (though this was not always so), even non-human animals are seldom considered capable of being responsible for such crimes. Admittedly, the news agency Reuters reported that as recently as 2008 "A Macedonian court convicted a bear of theft and damage for stealing honey from a beekeeper", but this seems to have been less a judgement on the ability of the bear (convicted it its absence) to engage in ethical deliberation, and more a pragmatic move that allowed the bee-keeper to be awarded criminal damages for his losses.

But, according to astronomers, stars are not only involved in the petty larceny of illicitly acquiring gas, but observations of exoplanets suggests some stars may even commit more daring, large-scale, heists,

"fairly small rocky planets two or three times the mass of the earth, in quite tight orbits around their star and you can speculate that they were once giant planets like Jupiter that have had the outer gassy layers blasted off and you are left with the rocky core, or maybe those planets were stolen from another star that got too close"
Prof. Carolin Crawford

A ménage à trois?

And there were other suggestions of anthropomorphism. It is not only stars that "don't live by themselves" in this universe,

"Nickel-56 [⁵⁶Ni] is what's called an iron peak element, so it lives with iron and cobalt on the periodic table…"
Prof. Mark Sullivan

And, it is not only gravity which seems to have preferences:

"And like Mark has described with electrons not wanting to be squeezed, you have neutron degeneracy pressure. Neutrons don't like to be compressed, at some point they resist it."
Prof. Carolin Crawford

Neither electrons nor neutrons actually have any preferences: but this is an anthropomorphic metaphor that efficiently communicates a sense of the natural phenomena. 'Resist' originally had an active sense as in taking a stand, but today would not necessarily be understood that way. Wanting and liking (or not wanting and not liking), however, strictly only refer to entities that can have desires and preferences.

Navigating photons

Professor Rees explained why some imploding stars are not seen as very bright stars that fade over years, but rather observed through extremely intense bursts of high energy radiation that fade quickly,

"The energy in the form of ordinary photons, ordinary light, that's arisen in the centre of a supernova, diffuses out and takes weeks to escape, okay, but if the star is spinning, then it will be an oblate spheroid, it will have a minor axis along the spin axis, and so the easy way out is for the radiation not to diffuse through but to find the shortest escape route, which is along the spin axis, and I mention this because gamma ray bursts are … when a supernova occurs but because the original star was sort of flattened there is an easy escape route and all the energy escapes in jets along the spin axis and so instead of it diffusing out over a period of weeks, as it does in a supernova, it comes out in a few seconds."
Prof. Martin Rees

Again, the language used is suggestive. Radiation is not just emitted by the star, but 'escapes' (surely a metaphor?). The phrasing "an easy way out" implies something not being difficult. Inanimate entities like photons do not actually (literally) find anything difficult or easy. Moreover, the radiation might "find the shortest escape route": language that does not reflect a playing out of physical forces but an active search – only a being able to seek can find. Yet, again, the language supports an engaging narrative, 'softening' the rather technical story by subtly reflecting a human quest.

Professor Rees also referred to how,

"when those big stars face a crisis they blow off their outer layers"
Prof. Martin Rees

again using phrasing which seems to present the stars as deliberate actors – they actively "blow off" material when they "face a crisis". A crisis is (or at least was originally) a point where a decision needs to be made. A star does not reach the critical point where it reluctantly decides it needs to shed some material – but rather is subject to changing net forces as the rate of heat generation from nuclear processes starts to decrease.

A sense of anthropomorphic narrative also attaches to Professor Crawford's explanation of how more massive stars process material faster,

"…more massive stars … actually have shorter lifetimes …they have to chomp through their fuel supply so furiously that they exhaust it more rapidly
Prof. Carolin Crawford

'Chomping', a term for vigorous eating (biting, chewing, munching), is here a metaphor, as a star does not eat – as pointed out in the companion piece, nutrition is a characteristics feature of living things, but does not map across to stars even if they are described as being born, living, dying and so forth. To be furious is a human emotional response: stars may process their remaining hydrogen quickly, but there is no fury involved. Again, though, the narrative, perhaps inviting associated mental imagery, communicates a sense of the science.

Laid-back gas

Another example of anthropomorphism was

"…if you have a gas cloud that's been sitting out in space for billions of years and has not bothered to contract because it's been too hot or it's too sparse…"
Prof. Carolin Crawford

This is an interesting example, as Prof. Crawford explicitly explains here that the gas cloud has not contracted because of the low density of material (so weak gravitational forces acting on the particles) and/or the high temperature (so the gas comprises of energetic, so fast moving, particles), so the suggestion that the material cannot be bothered (implication: that the 'cloud' operates as a single entity, and is sentient if perhaps a little lazy) does not stand in place of a scientific explanation, but rather simply seems to be intended to 'soften' (so to speak) the technical nature of the language used.

Analogy

An analogy goes beyond a simile or metaphor because there is some kind of structural mapping to make it explicit in what way or ways the analogue is considered to be like the target concept. ⁵ (Such as when explaining mass defect in relation to the material lost from the saucepan when cooking rice!)

Read about science analogies

So, Prof. Rees suggests that scientists can test their theories about star 'life cycles' by observation, even though an individual star only moves through the process over billions of years, and uses an analogy to a more familiar everyday context:

"We can test our theories, not only because we understand the physics, but because we can look at lots of stars. It is rather like if you had never seen a tree before, and you wandered around in a forest for a day, you can infer the life cycles of trees, you'd see saplings and big trees, etcetera. And so even though our lifetime is minuscule compared to the lifetime of a stable star, we can infer the population and life cycles of stars observationally and the theory does corroborate that fairly well."
Prof. Martin Rees

This would seem to make the basis of a good teaching analogy that could be discussed with students and would likely link well with their own experiences.

The other explicit analogy introduced by Prof. Rees is one well-known to physics teachers (sometimes in an ice-skater variant),

"If a contracting cloud has even a tiny little bit of spin, if it is rotating a bit, then as it contracts, then just like the ballerina who pulls in her arms and spins faster, then the contracting cloud will start to spin faster…"
Prof. Martin Rees

Stellar similes

I take the difference between a simile and a metaphor as the presence of an explicit marker (such as '…as…',…like…') to tell the listener/reader that a comparison is being made – so 'the genome is the blueprint for the body' would be a metaphor, where 'the genome is like a blueprint for the body' would be a simile.

As if a black hole cuts itself off

So, when Professor Rees describes how a massive black hole forms, he uses simile (i.e., "…as if were…"),

"So, if a neutron star gets above that mass, then it will compress even further, and will become a black hole – it will go on contracting until it, as it were, cuts itself off from the rest of the universe, leaving a gravitational imprint frozen in the space that's left. It becomes a black hole that things can fall into but not come out."
Prof. Martin Rees

There is an element of anthropomorphic narrative (see above) again here, if we consider the choice of active, rather than passive, phrasing

…as it were, cuts itself off from the rest of the universe, compared with
…as it were, becomes cut off from the rest of the universe

This is presented as something the neutron star itself does ("it will compress…become a black hole – it will go on contracting until it, as it were, cuts itself off…") rather than a process occurring in/to the matter of which it is comprised.

As if galaxies drop over the horizon

Prof. Rees uses another simile, when talking of how the expansion of space means that in time most galaxies will disappear from view,

"All the more distant universe which astronomers like Mark [Sullivan] study, galaxies far away, they will all have expanded their distance from us and in effect disappeared over a sort of horizon and so we just wouldn't see them at all. They'd be too faint, rather like …an inside-out black hole as it were, but in this case they moved so far away that we can't see them any more …"
Prof. Martin Rees

The term horizon, originally referring to the extent of what is in sight as we look across the curved Earth, has become widely used in astronomical contexts where objects cease to be in sight (i.e., the event horizon of a black hole beyond which any light being emitted by an object will not be able to leave {'escape!'} the black hole because of the intense gravitation field), but here Prof. Rees clearly marks out for listeners ("…in effect…a sort of…") that he is making a comparison with the familiar notion of a horizon that we experience here on Earth.

There is another simile here, the reference to the expansion of space leading to an effect "rather like…an inside-out black hole as it were" – but perhaps that comparison would be less useful to a listener new to the topic as it uses a scientific idea rather than an everyday phenomenon as the analogue.

Through a glass onion darkly?

Another simile used by Professor Rees was a references to a "sort of onion skin structure". Now 'onion skin' sometimes refers to the hard, dry, outer material (the 'tunic') usually discarded when preparing the onion for a dish. To a science teacher, however, this is more likely to mean the thin layer of epithelial tissue that can be peeled from the scales inside the bulb. These scales, which are potentially the bases of leaves that can grow if the bulb is planted, are layered in the bulb.

The skin is useful in science lessons as it is a single layer of cells, that is suitable for students to dissect from the onion, and mount for microscopic examination – allowing them to observe the individual cells. There is something at least superficially analogous to this in stars. Observations of the Sun show that convection processes gives rise to structures referred to as convection 'cells'.

Convection 'cells' at the Sun's surface (Source: NASA)

Yet, when Professor Rees' simile is heard in context, it seems that this is not the focus of the comparison:

"…all the nuclear processes which would occur at different stages in the heavy stars…which have this sort of onion skin structure with the hotter inner layers"
Prof. Martin Rees

Very large stars that have processed much of their hydrogen into helium can be considered to have a layered structure where under different conditions a whole sequence of processes are occurring leading to the formation of successively heavier and heavier elements, and ultimately to a build-up of iron near the centre.

The onion model of the structure of a large star (original image by Taken from Pixabay)

When I heard the reference to the onion, this immediately suggested the layered nature of the onion bulb being like the structure of a star that was carrying out the sequence of processes where the products of one fusion reaction become the raw material for the next. Presumably, my familiarity with the layered model of a star led me to automatically make an association with onions which disregarded the reference to the skin. That is, I had existing 'interpretive resources' to understand why the onion reference was relevant, even though the explicit mention of the skin might make the comparison obscure to someone new to the science.

Metaphors – all the way back up?

Some metaphors can easily be spotted (if someone suggests mitochondria are the power stations of the cell, or a lion is King of the jungle), but if our conceptual systems, and our language, are built by layers of metaphor upon metaphor then actually most metaphors are dead metaphors.

That is, an original metaphor is a creative attempt to make a comparison with something familiar, but once the metaphor is widely taken up, and in time becomes common usage and so a part of standard language, it ceases to act as a metaphor and becomes a literal meaning.

This presumably is what has happened with the adoption of the idea that stars are born, live out their lives, and then die: originally it was a poetic use of language, but now among astronomers it reflects an expanded standard use of terms that were once more restricted (born, live, lifetime, die etc.).

"…Stars dived in blinding skies / Stars die / Blinding skies…"
Stars die, but only due to artistic license
(Artwork from 'Star's die' by *Porcupine Tree*, photographer: Chris Kissadjekian)

If you see a standard candle…

When Professor Sullivan refers to a "standard candle", this is now a widely used astronomical notion (in relation to how we estimate distances to distant stars and galaxies that are much too far away to triangulate from parallax as the earth changes its position in the solar system) – but at one time this was used as a figure of speech.

Some figures of speech are created in the moment, but never widely copied and adopted. The astronomical community adopted the 'standard candle' such that it is now an accepted term, even though most young people meeting astronomical ideas for the first time probably have very little direct experience of candles. What might once have seemed a blatantly obvious allusion may now need explaining to the novice.

When Sir Arthur Eddington (famous for collecting observations during an eclipse consistent with predictions from relativity theory about the gravitational 'bending' of starlight) gave a public lecture in 1932, he seems to have assumed that his audience would understand the analogy between an astronomer's 'standard candles' (Cepheid variables) and standard candles they might themselves use!

"If you see a standard candle anywhere and note how bright it appears to you, you can calculate how far off it is; in the same way an astronomer observes his [or her] 'standard candle' in the midst of a nebula, notes its apparent brightness or magnitude, and deduces the distance of the nebula"
Eddington, 1933/1987, pp.7-8

This ongoing development in language means that it may not always be entirely clear which terms are still engaged with as if metaphors and which have now become understood as literal. That is, in considering whether some phrase is a metaphor we can ask two questions:

did the author/speaker intend this as a comparison, or do they consider the term has direct literal meaning?
does the reader/listener understand the term to have a literal meaning, or is it experienced as some novel kind of comparison with another context which has to be related back to the focus?

In the latter case we might also think it is important to distinguish between cases where the audience member can decode the intention of the comparison 'automatically' as part of normal language processing – and cases where they would have to consciously deliberate on the meaning. (In the latter case, the interpretation is likely to disrupt the flow of reading, and when listening could perhaps even require the listener to disengage from the communication such that subsequent speech is missed.)

(Metaphorical?) hosts

So, when Prof. Crawford suggests that

"The supernovae, particularly, are of fundamental importance for the host galaxy…"
Prof. Carolin Crawford

her use of the term 'host' is surely metaphorical (at least for a listener – this term is widely used in the literature of academic astronomy ⁶). A host offers hospitality for a guest. That does not seem to obviously reflect the relationship between a supernova and the galaxy it is found in and is part of. It is not a guest: rather, in Prof. Sullivan's terms we might suggest that star has 'lived its entire life' in that galaxy – it is its galactic 'home'. Despite this comparison not standing up to much formal analysis, I suspect the metaphor can be automatically processed by anyone with strong familiarity with the concept of a host. Precise alignment may not be a strong criterion for effective metaphors.

Another meaning of host refers to a sacrificial victim (as in the host in the Christian Eucharist) which seems unlikely to be the derivation here, but perhaps fits rather well with Prof. Crawford's point. A supernova too close to earth could potentially destroy the biosphere – an unlikely but not impossible event.

(Metaphorical?) bubbles

Professor Crawford described some of the changes during a supernova,

"You have got your iron core, it collapses down under gravity in less than a second, that kind of leaves the outer layers of the star a little behind, they crash down, bounce on the surface of the core, and then there's a shockwave, that propels all this stellar debris, out into space. So, this is part of the supernova explosion we have been talking about, and it carves out a bubble within the interstellar medium."
Prof. Carolin Crawford

There are a number of places here where everyday terms are applied in an unfamiliar context such as 'core', 'bouncing', 'layers' and 'debris'. But the idea of carving a bubble certainly seems metaphorical, if only because a familiar bubble would have a physical surface, where surely, here, there is no strict interface between discrete regions of gases. But, again, the term offers an accessible image to communicate the process. (And anyone looking at the NASA image above of convection cells in the Sun might well feel that these can be perceived as if bubbles.)

(Metaphorical?) pepper

Similarly, the idea of heavy elements from exploding suns being added to the original hydrogen and helium in the interstellar medium as like adding pepper also offers a strong image,

"…this is the idea of enrichment, you start off with much more primordial hydrogen and helium gas that gets steadily peppered with all these heavy elements…"
Prof. Carolin Crawford

Perhaps 'peppered' is now a dead metaphor, as it is widely used in various contexts unrelated to flavouring food.

(Metaphorical?) imprints

When Professor Rees referred to a neutron star that has become a black hole leaving a "gravitational imprint frozen in the space that's left" this makes good sense as the black hole will not be visible, but its gravitational field will have effects well beyond its event horizon. Yet, one cannot actually make an imprint in space, one needs a suitable material substrate (snow, plater, mud…) to imprint into; and nor has anything been 'frozen' in a literal sense. Indeed, the gravitational field will change as the black hole acquires more material through gravitational capture (and in the very long term loses mass though evaporates Hawking radiation – which is said to cause the black hole to 'evaporate'). So, this is a kind of double metaphor.

(Metaphorical?) blasts and blows

I report above both the idea that rocky planet close to large stars might have derived from 'giant' planets "that have had the outer gassy layers blasted off" and how "big stars…blow off their outer layers". Can stars really blow, or is this based on a metaphor. Blasts usually imply explosions, sudden events, so perhaps these are metaphorical blasts? And it is not just larger stars that engage in blowing off,

"[The sun] will blow off its outer layers and become a red giant, expanding so it will engulf the inner planets, but then the core will settle down to what's called a white dwarf, this is a dead, dense star, about a million times denser than normal stuff…."
Prof. Martin Rees

Metaphors galore!

Perhaps those last examples are not especially convincing – but this reflects a point I made earlier. Language changes over time: it is (metaphorically-speaking) fluid. If language started from giving names to things we can directly point at, then anything we cannot directly point at needs to be labelled in terms of existing words. Most of the terms we use were metaphors at some point, but became literal as the language norms changed.

But society is not a completely homogeneous language community. The requirements of professional discourse in astronomy (or any other specialised field of human activity) drive language modifications in particular regards ahead of general language use. It is not just people in Britain and the United States who are divided by a common language – we all are to some extent. What has become literal meaning for for one person (perhaps a science teacher) may well only be a metaphor to another (a student, say).

After all, when I look up what it is to blow off, I find that the most common contemporary meaning relates to a failure to meet a social obligation or arrangement – I am pretty sure (from the context) that that is not what Professor Rees was suggesting ("…when those big stars face a crisis they [let down] their outer layers".) Once we start looking at texts closely, they seem to be 'loaded' with figures of speech. A planet is not materially constrained in space, yet we understand why an orbit might be considered 'tight'.

In the proceeding quote, the core of a star seems to need no explanation although it presumably derives by analogy with the core of an apple or similar fruit, which itself seems to derive metaphorically form an original meaning of the heart. Again, what is meant by engulf is clear enough although originally it referred to the context of water and the meaning has been metaphorically (or analogously) extended.

The terms red giant and white dwarf clearly derive from metaphor. (Sure, a red giant is gigantic, but then, on any normal scale of human experience, so is a white dwarf.) These terms might mystify someone meeting them for the first time so not already aware they are used to refer to classes of star. This might suggest the value of a completely objective language for discussing science where all terms are tightly (hm, too metaphorical…closely? rigidly? well-) defined, but that would be a project reminiscent of the logical positivist programme in early twentieth century that ultimately proved non-viable. We can only define words with more words, and there are limits to the precision possible with a usable, 'living', language.

Take the "discovery that we are literally made of the ashes of long dead stars". Perhaps, but the term ashes normally refers to the remains of burnt organic material, especially wood, so perhaps we are not literally, but only metaphorically made of the ashes of long dead stars. Just as when when Professor Sullivan noted,

"the white dwarf is made of carbon, it's made of oxygen, and the temperature and the pressure in the centre of that white dwarf star can become so extreme, that carbon detonation can occur in the centre of the white dwarf, and that is a runaway thermonuclear reaction – that carbon burns in astronomer speak into more massive elements…"
Prof. Mark Sullivan

Are we stardust, ashes or just waste?

Burning is usually seen in scientific terms as another word for combustion. So, the nuclear fusion, 'burning' "in astronomer speak" of its nuclear 'fuel' in a star represents an extension of the original meaning by analogy with combustion. ⁹ Material that is deliberately used to maintain a fire is fuel. A furnace is an artefact deliberately built to maintain a high temperature – the nuclear furnace in a star is not an artefact but a naturally occurring system (gravity holds the material in place), but is metaphorically a furnace. A runaway is a fugitive who has absconded – so to describe a thermonuclear reaction (which is not going anywhere in spatial terms) as 'runaway' adopts what was a metaphor. (Astronomers also use the term 'runaway' to label a class of star that seem to be moving especially fast compared with the interstellar medium – a somewhat more direct borrowing of the usual meaning of 'runaway'.)

To consider us to be made from 'nuclear waste' relies on seeing the star-as-nuclear-furnace as analogous to a nuclear pile in a power station. In nuclear power stations we deliberately process fissile material to allow us to generate electrical power: and material is produced as a by-product of this process (that is, it is a direct product of the natural nuclear processes, but a by-product of our purposeful scheme to generate electricity). To consider something waste means making a value judgement.

If the purpose of a star is to shine (a teleological claim) and the fusion of hydrogen is the means to achieve that end, then the material produced in that process which is no longer suitable as 'fuel' can be considered 'waste'. If the universe does not have any purpose(s) for stars then there is no more basis for seeing this material as waste than there is for seeing stars themselves as the waste products of a process that causes diffuse matter to come together into local clumps. That is, this is an anthropocentric perspective that values stars as of more value than either the primordial matter from which they formed, or the 'dead' matter they will evolve into when they no longer shine 'for us'. Nature may not have such favourites! If it has a purpose, then stars seem to only be intermediate steps towards its ultimate end.

What does support the turtle? *Surely*, it's metaphors all the way down.
(Source: Pintrest)

Sources cited:

Eddington, A. (1933/1987). The Expanding Universe. Cambridge: Cambridge University Press.
Lakoff, G., & Johnson, M. (1980). The metaphorical structure of the human conceptual system. Cognitive Science, 4(2), 195-208.
Ross, J. R. (1967). Constraints on variables in syntax. (Ph.D.), Massachusetts Institute of Technology. https://babel.ucsc.edu/~hank/ross67.pdf
Taber, K. S. (2013). Revisiting the chemistry triplet: drawing upon the nature of chemical knowledge and the psychology of learning to inform chemistry education. Chemistry Education Research and Practice, 14(2), 156-168. doi:10.1039/C3RP00012E (Manuscript version can be downloaded here).
Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Cambridge: Royal Society of Chemistry.
Ulmer, M., Grace, V., Hudson, H., & Schwartz, D. (1972). Upper Limits to the X-Ray Luminosities of Five Supernovae. The Astrophysical Journal, 173, 205.

Notes:

¹It may seem fanciful that we give a specific individual tree a proper name but should a child inherently appreciate that we commonly name individual hamsters (say, or ships, or roads), but not individual trees? 'Major Oak' is a particular named Oak tree in Sherwood Forest, so the idea is not ridiculous. (It is very large, but apparently the name derives from it being described by an author with the army rank of major. Of course, this term for a soldier leading others derives metaphorically from a Latin word meaning bigger, so…)

² "So how do we bridge between dogs and trees on one hand and electrons and the strong nuclear force on the other (so to speak!)? The answer is we build using analogy and we talk about those constructions using a great deal of metaphor."

We understand what is meant by bridge here in relation to an actual bridge that physically links two places – such as locations on opposite sides of a river or railway line.
There is no actual building up of materials, but we understand how we can 'build' in the abstract by analogy.
These things are not actually at hand, but we make a metaphorical comparison in terms of distinguishing items held in 'opposite' hands. We understand what is meant by a great deal of something abstract by analogy with a great deal of something we can directly experience, e.g., sand, water, etcetera.

Justice personified, on the one hand weighing up the evidence and on the other imposing sanctions

(Image by Sang Hyun Cho from Pixabay)

We construct scientific concepts and models and theories by analogy with how we construct material buildings – we put down foundations then build up brick by brick so that the top of the structure is only very indirectly supported by the ground.

(Image by joffi from Pixabay)

³ A point is a hypothetical, infinitesimally small, location in space, which is not something a person could actually make. The 'point' of an argument is metaphorically like the point of a pencil or spear which is metaphorically an approximation to an actual point. Of course, we (adult members of the English language community) all know what is meant by the point of an argument – but people new to a language (such as young children) have to find this out, without someone holding up the point of an argument for them to learn to recognise.

⁴ In part, this means linguistic resources. Each individual person has a unique vocabulary, and even though sharing most words with others, often has somewhat unique ranges of application of those words. But it also refers to personal experiences that can be drawn upon (e.g., having cared for an ill relative, having owned a pet, having undertaken part-time work in a hospital pharmacy, having been taken to work by a parent…) and the cultural referents that are commonly discussed in discourse (cultural icons like the Mona Lisa or Beethoven's fifth symphony; familiarity with some popular television show or film; appreciating that Romeo and Juliet were tragic lovers, or that Gandhi is widely considered a moral role model, and so forth.)

"Penny, I'm a physicist. I have a working knowledge of the entire universe and everything it contains."

"Who's Radiohead?"

"I have a working knowledge of the important things in the universe."

Still from 'The Big Bang Theory' (Chuck Lorre Productions / Warner Bros. Television)

The interpretive resources are whatever mental resources are available to help make sense of communication.

⁵ I am using the term concept in an 'inclusive' sense (Taber, 2019), in that whenever a person can offer a discrimination about whether something is an example of some category, then they hold a concept (vague or detailed; simple or complex; canonical or alternative).

That is, if someone can (beyond straight guesswork) try to answer one of the questions "what is X? ", "is this an example of X?" or "can you suggests an example of X?", then they have a relevant concept – where X could be…

a beaker
a force
a bacterium
opaque
a transition metal
an isomer
distillation
neutralisation
a representation of the ideal gas law
and so forth

Read more about concepts

⁶ The earliest reference to 'host galaxies' I found in a quick search of the scientific literature was from 1972 in a paper which used the term 'host galaxy' 8 times, including,

"We estimated the distances [of observed supernovae]…by four different methods:

(1) Estimating the absolute luminosity of the host galaxy.

(2) Estimating the absolute luminosity of the supernova.

(3) Using the measured redshift of the host galaxy and assuming the Hubble constant H = 75 km (s Mpc)^-1 …

(4) Identifying the host galaxy with a cluster of galaxies for which the distance from Earth had already been estimated.

Ulmer, Grace, Hudson & Schwartz, 1972, p.209

The term 'host galaxy' was not introduced or defined in the paper, suggesting that either it was already in common use as a scientific term (and so a dead metaphor within the astronomical community) in 1972 or Ulmer and colleagues assumed it was obvious enough not to need explanation.

⁷ It should be pointed out that 'In Our Time' is not presented as succession of mini-lectures, or as a tightly scripted programme, but as a conversation between Melvyn as his guests. Of course, there is some level of preparation by those involved, but in adopting a conversational style, avoiding the sense of prepared statements, it is inevitable that a guest's language will sometimes lack the precision of a drafted and much revised account.

⁸ A supernova may appear as a new star in the sky if it is so far away that the star was not previously detectable, or as a known star quick;y becoming very much brighter.

⁹ One should be careful in making such equivalences, as in that although we may equate burning with combustion, burning is an everyday ('life world') phenomenon, and combustion is a scientific concept: often our scientific concepts are more precisely defined than the related everyday terms. (Which is why melting has a broader meaning in everyday life {the sugar melts in the hot tea; the stranger melted away into the mist} than it does in science.) But although we might say, as suggested earlier in the text, we have been burned by exposure to the sun's ultraviolet rays, or by contact with a caustic substance, in those contexts we are unlikely to consider our skin as 'fuel' for the process.

Was the stellar burp really a sneeze?

Pulling back the veil on an astronomical metaphor

Keith S. Taber

It seems a bloated star dimmed because it sneezed, and spewed out a burp.

'Pardon me!' (Image by Angeles Balaguer from Pixabay)

I was intrigued to notice a reference in Chemistry World to a 'stellar burp'.

"…the dimming of the red giant Betelgeuse that was observed in 2019…was later attributed to a 'stellar burp' emitting gas and dust which condensed and then obscured light from the star"
Motion, 2022

The author, Alice Motion, quoted astrophysics doctoral candidate and science communicator Kirsten Banks commenting that

"In recorded history…It's the first time we've ever seen this happen, a star going through a bit of a burp"
Kirsten Banks quoted in Chemistry World

although she went on to suggest that the Boorong people (an indigenous culture from an area of the Australian state Victoria) had long ago noticed a phenomena that became recorded in their oral traditions ¹, which

"was actually the star Eta Carinae which went through a stellar burp, just like Betelgeuse did"
Kirsten Banks quoted in Chemistry World

Composite image (optical appearing as white; ultraviolet as cyan; X-rays as purple) of Eta Carinae,

Source: NASA

Clearly a star cannot burp in the way a person can, so I took this to be a metaphor, and wondered if this was a metaphor used in the original scientific report.

A clump and a veil

The original report (Montargès, et al, 2021) was from Nature, one of the most prestigious science research journals. It did not seem to have any mention of belching. This article reported that,

"From November 2019 to March 2020, Betelgeuse – the second-closest red supergiant to Earth (roughly 220 parsecs, or 724 light years, away) – experienced a historic dimming of its visible brightness…an event referred to as Betelgeuse's Great Dimming….Observations and modelling support a scenario in which a dust clump formed recently in the vicinity of the star, owing to a local temperature decrease in a cool patch that appeared on the photosphere."
Montargès, et al., 2012, p.365

So, the focus seemed to be not on any burping but a 'clump' of material partially obscuring the star. That material may well have arisen from the star. The paper in nature suggests that Betelgeuse may loose material through two mechanisms: both by a "smooth homogeneous radial outflow that consists mainly of gas", that is a steady and continuous process; but also "an episodic localised ejection of gas clumps where conditions are favourable for efficient dust formation while still close to the photosphere" – that is the occasional, irregular, 'burp' of material, that then condenses near the star. But the word used was not 'burp', but 'eject'.

A fleeting veil

Interestingly the title of the article referred to "A dusty veil shading Betelgeuse". The 'veil' (another metaphor) only seemed to occur in the title. There is an understandable temptation, even in scholarly work, to seek a title which catches attention – perhaps simplifying, alliterating (e.g., '…mediating mental models of metals…') or seeking a strong image ('…a dusty veil shading…'). In this case, the paper authors clearly thought the metaphor did not need to be explained, and that readers would understand how it linked to the paper content without any explicit commentary.

Word	Frequency in Nature article
clump(s)	25 (excluding reference list)
eject(ed, etc.)	4
veil	1 (in title only)
burp	0
blob	0

There's no burping in Nature

The European Southern Observatory released a press release (sorry, a 'science release') about the work entitled 'Mystery of Betelgeuse's dip in brightness solved', that explained

"In their new study, published today in Nature, the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse's stellar surface.

Betelgeuse's surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust.

'We have directly witnessed the formation of so-called stardust,' says Montargès, whose study provides evidence that dust formation can occur very quickly and close to a star's surface. 'The dust expelled from cool evolved stars, such as the ejection we've just witnessed, could go on to become the building blocks of terrestrial planets and life', adds Emily Cannon, from KU Leuven, who was also involved in the study."
https://www.eso.org/public/news/eso2109/

So, again, references to ejection and a veil – but no burping.

Delayed burping

Despite this, the terminology of the star burping, seems to have been widely taken up in secondary sources, such as the article in Chemistry World

A New Scientist report suggested "Giant gas burp made Betelgeuse go dim" (Crane, 2021). On the website arsTECHNICA, Jennifer Ouellette wrote that "a cold spot and a stellar burp led to strange dimming of Betelgeuse".

On the newsite Gizmodo, George Dvorsky wrote a piece entitled "A dusty burp could explain mysterious dimming of supergiant star Betelgeuse". Whilst the term burp was only used in the title, Dvorsky was not shy of making other corporeal references,

"a gigantic dust cloud, which formed after hot, dense gases spewed out from the dying star. Viewed from Earth, this blanket of dust shielded the star's surface, making it appear dimmer from our perspective, according to the research, led by Andrea Dupree from the Centre for Astrophysics at Harvard & Smithsonian.

A red supergiant star, Betelgeuse is nearing the end of its life. It's poised to go supernova soon, by cosmological standards, though we can't be certain as to exactly when. So bloated is this ageing star that its diameter now measures 1.234 million kilometers, which means that if you placed Betelgeuse at the centre of our solar system, it would extend all the way to Jupiter's orbit."

The New York Times published an article (June 17, 2021) entitled "Betelgeuse Merely Burped, Astronomers Conclude", where author Dennis Overbye began his piece:

"Betelgeuse, to put it most politely, burped."
The New York Times

Overbye also reports the work from the Nature paper

"We have directly witnessed the formation of so-called stardust," Miguel Montargès, an astrophysicist at the Paris Observatory, said in a statement issued by the European Southern Observatory. He and Emily Cannon of Catholic University Leuven, in Belgium, were the leaders of an international team that studied Betelgeuse during the Great Dimming with the European Southern Observatory's Very Large Telescope on Cerro Paranal, in Chile.

Parts of the star, they found, were only one-tenth as bright as normal and markedly cooler than the rest of the surface, enabling the expelled blob to cool and condense into stardust. They reported their results on Wednesday in Nature."
The New York Times

So, instead of the clumps referred to in the Nature article as ejected, we now have an expelled blob (neither word appears in the nature article itself). Overbye also explains how this study followed up on earlier observations of the star

"Their new results would seem to bolster findings reported a year ago by Andrea Dupree of the Harvard-Smithsonian Center for Astrophysics and her colleagues, who detected an upwelling of material on Betelgeuse in the summer of 2019.

'We saw the material moving out through the chromosphere in the south in September to November 2019,', Dr. Dupree wrote in an email. She referred to the expulsion as 'a sneeze.'
The New York Times

'**…material moving out through the chromosphere in the south…**': Hubble space telescope images of Betelgeuse (Source: NASA) ²

Bodily functions and stellar processes

I remain unsure why, if the event was originally considered a sneeze, it became transformed into a burp. However the use of such descriptions is not so unusual. Metaphor is a common tool in science communication to help 'make the unfamiliar familiar' by describing something abstract or out-of-the-ordinary in more familiar terms.

Read about metaphors in science

Here, the body [sic] of the scientific report keeps to technical language although a metaphor (the dust cloud as a veil) is considered suitable for the title. It is only when the science communication shifts from the primary literature (intended for the science community) into more popular media aimed at a wider audience that the physical processes occurring in a star became described in terms of our bodily functions. So, in this case, it seems a bloated star dimmed because it sneezed, and spewed out a burp.

Coda

The astute reader may have also noticed that the New York Times article referred to Betelgeuse as an "ageing star" that is "nearing the end of its life": terms that imply a star is a living, and mortal, being. This might seem to be journalistic license, but the NASA website from which the sequence of Betelgeuse images above are taken also refers to the star as ageing (as well as being 'petulant' and 'injured').² NASA employs scientifically qualified people, but its public websites are intended for a broad, general audience, perhaps explaining the anthropomorphic references.

Thus, we might understand references to stars as alive as being a metaphorical device used in communicating astronomical ideas to the general public. Yet, an examination of the scientific literature might instead suggest instead that astronomers DO consider stars to be alive. But, that is a topic for another piece.

Work cited:

Crane, L. (2021). Giant gas burp made Betelgeuse go dim. New Scientist, 250(3340), 22. doi:10.1016/S0262-4079(21)01094-0
Hamacher, D. W., & Frew, D. J. (2010). An aboriginal Australian record of the great eruption of Eta Carinae. Journal of Astronomical History and Heritage, 13(3), 220-234.
Montargès, M., Cannon, E., Lagadec, E., de Koter, A., Kervella, P., Sanchez-Bermudez, J., . . . Danchi, W. (2021). A dusty veil shading Betelgeuse during its Great Dimming. Nature, 594(7863), 365-368. doi:10.1038/s41586-021-03546-8
Motion, A. 2022, Space for more science. Astrophysics and Aboriginal astronomy on TikTok, Chemistry World, December 2022, p.15 (https://www.chemistryworld.com/opinion/space-for-more-science/4016585.article)

Notes

¹ William Edward Stanbridge (1816-1894) was an Englishman who moved to Australia in 1841. He asked Boorong informants about their astronomy, and recorded their accounts. He presented a report to the Philosophical Institute of Victoria in 1857 and published two papers (Hamacher & Frew, 2010). The website Australian Indigenous Astronomy explains that

"The larger star of [of the binary system] Eta Car is unstable and undergoes occasional violent outbursts, where it sheds material from its outer shells, making it exceptionally bright. During the 1840s, Eta Car went through such an outburst where it shed 20 solar masses of its outer shell and became the second brightest star in the night sky, after Sirius, before fading from view a few years later. This event, commonly called a "supernova-impostor" event, has been deemed the "Great Eruption of Eta Carinae". The remnant of this explosion is evident by the Homunculus Nebulae [see figure above – nebulae are anything that appears cloud-like to astronomical observation]. This identification shows that the Boorong had noted the sudden brightness of this star and incorporated it into their oral traditions."
Duane Hamacher

A paper in the Journal of Astronomical History and Heritage concludes that

"the Boorong people observed 𝜂 Carinae in the nineteenth century, which we identify using Stanbridge's description of its position in Robur Carolinum, its colour and brightness, its designation (966 Lac, implying it is associated with the Carina Nebula), and the relationship between stellar brightness and positions of characters in Boorong oral traditions. In other words, the nineteenth century outburst of 𝜂 Carinae was recognised by the Boorong and incorporated into their oral traditions"
Hamacher & Frew 2010, p.231

² The images reproduced here are presented on a NASA website under the heading 'Hubble Sees Red Supergiant Star Betelgeuse Slowly Recovering After Blowing Its Top'. This is apparently not a metaphor as the site informs readers that"Betelgeuse quite literally blew its top in 2019". Betelgeuse is described as a "monster star", and its activity as "surprisingly petulant behaviour" and a "titanic convulsion in an ageing star", such that "Betelgeuse is now struggling to recover from this injury."

This seems rather anthropomorphic – petulance and struggle are surely concepts that refer to sentient deliberate actors in the world, not massive hot balls of gas. However, anthropomorphic narratives are often used to make scientific ideas accessible.

Read about anthropomorphism

The recovery (from 'injury') is described in terms of two similes,

"The star's interior convection cells, which drive the regular pulsation may be sloshing around like an imbalanced washing machine tub, Dupree suggests. … spectra imply that the outer layers may be back to normal, but the surface is still bouncing like a plate of gelatin dessert [jelly] as the photosphere rebuilds itself."
NASA Website

Read about science similes

Communicating astronomical extremes

When is a star no longer a star (or, does it become a different star?)

Going nova

"A long time ago, in a galaxy far, far away"

Comparisons of scale

Figurative language

Anthropomorphism

Feeding frenzy?

One person's garbage…?

Let's hear it for the little guys

Appendix A: "the star hidden in the heart of [the] only supernova visible from Earth"

Appendix B: "possibly the brightest object in our universe"

Notes

Do plants deliberately deceive insects?

Mysterious plants

No insects were deceived in the making of this programme

Anthropomorphism and teleology

Darwin's book on 'various contrivances'

A difficult balance for science communicators

Work cited:

Notes:

Does a sunflower have large flowers?

A new study reports a creative approach to modelling the atom motivated by a love story

Modelling 'the' atom

The story

Prologue

Chapter 1 – part 1

Chapter 1 – part 2

Chapter 2 and epilogue

Interpreting the narrative

Metaphorical meanings?

Orbitals and transitions

The rationale

A diagnostic assessment opportunity

A hybrid model?

An atom with seven energy levels?

Interorbital distances?

Spherical orbitals

Making sense of 486 nm and the 'THz 457s'

The Balmer series

A sleight of hand?

The model

Encouraging a new alternative conception?

To see through an orbital clearly?

Work cited:

Notes

A cold temperature reaction?

Surely you are joking, Prof. Feynman? 1

The late, great, Richard Feynman

Why does it rain in drops?

What makes for a good explanation?

Feynman's explanation is logical (if incomplete)

So, is this a good explanation?

Was Feynman's explanation scientific?

An anthropomorphic explanation

A teaching model?

Mapping Feynman's explanation

Work cited:

Notes:

Does the medieval notion of the human body as a microcosm of the wider Cosmos – in which is played out an eternal battle between good and evil – still influence our thinking?

Carver's account of the immune system

The analogy

Microbes and cells as agents

Immune cells do not commit kamikaze

Immune cells do not carry out massacres

Anthropomorphic references

Animistic language

Microbes moving in

What is for dinner?

Can you have too much of a metaphorical good thing?

Notes

Work cited

A reflection on the pedagogy in Andrew Scott's 'Vital Principles'

The task of the popular science writer

Andrew Scott

Metaphors for molecular mechanisms

Nature and nurture

Form and function in biology

Anthropomorphism: living metaphors

Dead metaphors

Surely you are joking, Prof. Feynman? ¹