science in the media - Science-Education-Research

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

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

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

ChemTeach – is a discussion list for sharing information and expertise among those involved in teaching chemistry. Click here to learn more about, or find out how to join, the group

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

Would you like some rare earths with that?

A chemically illiterate internet meme

Keith S. Taber

The challenge of popular science writing

I often enjoy reading popular accounts of science topics, but sometimes one comes across statements that are vague or dubious or confusing – or simply wrong. Some of this reflects a basic challenge that authors of popular science share with science teachers and other science communicators: scientific ideas are often complex, subtle and abstract. Doing them justice requires detailed text and technical terminology. Understanding them often depends upon already having a good grasp of underpinning concepts. That is fine in a formal report for other scientists, but is not of any value to a non-specialist audience.

So, the author has to simplify, and perhaps round off some of the irregular detail; and to find ways to engage readers by using language and examples that will make sense to them. That is, finding ways to 'make the unfamiliar familiar'.

Read about making the unfamiliar familiar in teaching

I am sure that often the passages in popular science books that I as a scientist ¹ get grumpy about are well motivated, and, whilst strictly inaccurate, reflect a compromise between getting the science perfect and making it accessible and engaging for the wider readership. Sometimes, however, one does get the impression that the author has not fully grasped the science they are writing about.

"Lucy Jane Santos is the Executive Secretary of the British Society for the History of Science…"

Public engagement with radium

I very much enjoyed reading a book, 'Half lives', by the historian of science Lucy Jane Santos, about how in the decades after its discovery by Pierre and Marie Curie, radium was the subject of wide public interest and engagement. One of the intriguing observations about this newly discovered element was that it appeared to glow in the dark. We now know that actually the glow comes from nitrogen in the air, as radium is radioactive and emissions by radium 'excite' (into a higher energy state) nitrogen molecules, which then emit visible light as they return ('relax') to their 'ground' state. This production of light without heating (a phenomenon generally called luminescence), when it is due to exposure to radioactivity, is known as radioluminescence.

Today, many people are very wary of radioactivity – with good reason of course – but Santos describes how at one time radium was used (or at least claimed as an ingredient) in all kinds of patent medicines and spa treatments and cosmetics (and even golf balls). This was a fascinating (and sometimes shocking) story.

What substance(s) can you find in quinine?

I did find a few things to quibble over – although across a whole book it was, only, a few. However, one statement that immediately stood out as dodgy science was the claim that quinine contained phospor:

"Quinine contains phosphor, a substance that luminesces when exposed to certain wavelengths of light…"
Santos, 2020

This may seem an unremarkable statement to a lay person, but to a scientist this is nonsensical. Quinine is a chemical compound (of carbon, hydrogen, nitrogen and oxygen), that is – a single substance. A single substance cannot contain another substance – any more than say, a single year can contain other years. An impure sample of a substance will contain other substances (it is in effect a mixture of substances), but quinine itself is, by definition, just quinine.

Molecular structure of the chemical compound quinine (C₂₀H₂₄N₂O₂) – a pure sample of quinine would contain only (a great many copies of) this molecule.

Note – no phosphorus, and no rare earth metal atoms.

(Image source: Wikimedia)

Confusing terminology

The term 'phosphor' refers to a luminescent material – one that will glow after it has been exposed to radiation (often this will be ultraviolet) or otherwise excited. The term is usually applied to solid materials, such as those used to produce an image in television and monitor screens.

The term derives by reference to the element phosphorus which is a luminescent substance that was accordingly itself given a name meaning 'light-bearing'. The term phosphorescent was used to describe substances that continue to glow for a time after irradiation with electromagnet radiation ceases. But it is now known that phosphorus itself is not phosphorescent, but rather its glow is due to chemiluminescence – there is a chemical reaction between the element and oxygen in the air which leads to light being emitted.

The widely used term phosphor, then, reflects an outdated, historical, description of a property of phosphorus; and does not mean that phosphors contain, or are compounds of, phosphorus. There is clearly some scope for confusion of terms here. ²

term	meaning
luminescence	the emission of light by a cold object (in contrast to incandescence)
– chemiluminescence	a form of luminescence due to a chemical reaction
– – bioluminescence	a form of chemiluminescence that occurs in living organisms
– electroluminescence	a form of luminescence produced by passing electrical current through some materials
– photoluminescence	a form of luminescence due to irradiation by electromagnetic radiation, such as ultraviolet
– – fluorescence	a type of photoluminescence that only occurs whilst the object is being excited (e.g., by exposure to ultraviolet)
– – phosphorescence	a type of photoluminescence that continues for some time after the object has been being excited (e.g., by exposure to ultraviolet)
– radioluminescence	a form of luminescence due to a material being exposed to ionising radiation (e.g., 𝛂 radiation)
– sonoluminescence	a form of luminescence due to a material being exposed to sound
phosphor	a material that exhibits luminescence
phosphorus	a chemical element that exhibits chemiluminescence (when exposed to air)

There is a range of terms relating to luminescence. Here are some of those terms.

Some central ideas about luminescence (represented on a concept map)

A traditional medicine

Quinine, a substance extracted from the bark of several species of Cinchona, has long been used for medicinal purposes (e.g., by the Quechua people of the Americas ³), as it is a mild antipyretic and analgesic. It is an example of a class of compounds produced by plants known as an alkaloids. Plant alkaloids are bitter, and it is thought their presence deters animals from eating the plant. We might say that Quechua pain medication is a bitter pill to swallow.

Modern science has often adopted and developed technologies that had long been part of the 'traditional ecological knowledge' of indigenous groups – such as making extracts from Cinchona bark to use as medicines.

Sadly, the original discovers and owners of such technologies have not always been properly recognised when such technologies have been acquired, transferred elsewhere, and reported. ³

(Image by GOKALP ISCAN from Pixabay)

Quinine is an ingredient of tonic water (and bitter lemon drink) added because of its bitter taste.

(Why deliberately make a drink bitter? Quinine has anti-malarial properties which made it a useful substance to add to drinks in parts of the world where malaria is endemic. People liked the effect!)

Quinine glows when exposed to ultraviolet light. It is luminescent. To be more specific, quinine is photoluminescent. (This is responsible for the notion that someone offered a gin and tonic at a disco should test it under the 'blacklights' to make sure they have not been given pure gin to drink. Although, I am slightly sceptical about whether the kind of people that drink 'G&T's go to the kind of dances that have ultraviolet lighting.)

"I do apologise, I think I might have just splashed a tiny droplet of my tonic water on you"

(Image by Victoria_Watercolor from Pixabay)

It is reasonable to describe quinine as a phosphor in the wider sense of the term – but it does not contain another phosphor substance, any more than, say, iron contains a metallic substance or sulphur contains a yellow substance or sucrose contains a sweet substance or copper a conducting substance. So, a more accurate formulation would have been

"Quinine [is a] phosphor, a substance that luminesces when exposed to certain wavelengths of light…"

or, perhaps better still, simply

"Quinine [is] a substance that luminesces when exposed to certain wavelengths of light…"

Ask the oracle

I was intrigued at why Lucy Jane Santos might have been confused about this, until I did a quick internet search. Then I found a range of sites that claimed that quinine contains phosphors – indeed, often, rare earths are specified.

The rare earths (another unfortunate historic choice of name, as it transpired that they are neither especially rare nor 'earths', i.e., oxides) are a group of metallic elements. They are not as well known as, say, iron, copper, zinc, aluminium or gold, but they have with a wide range of useful applications.

Scandium, the first of the 'rare earth' metals. Probably not what you want in your tonic water.

(Creative Commons Attribution 3.0 Unported License, sourced from https://images-of-elements.com/scandium.php)

If something is repeated enough, does it become true?

Clearly there are not rare earths in quinine. So, the following quotes (from sites accessed on 7^th March 2023) proffer misinformation.

"If you want to get a bit more scientific about it…. quinine contains rare earth compounds called phosphors. These are the substances which glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own colour, in this case glowing blue light."
https://www.iceandaslice.co.uk/blogs/news/why-does-your-gin-and-tonic-glow-blue-in-ultraviolet-light

This claim is odd, as the previous paragraph explained more canonically: "why does quinine absorb UV light (the invisible component of sunlight that produces sun tans and sunburns!)? It is due to the structure of the quinine molecule, which enables it to take in energy in the form of invisible UV light and immediately radiate some of that same energy in the form of visible blue light." Other compounds cannot be inside a molecule – so this more canonical explanation is not consistent with quinine containing other "substances" which were "rare earth compounds."

"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light."
https://sciencing.com/quinine-fluorescent-5344077.html

The following extract appeared under the subheading "Why is quinine fluorescence?" That reflects a category error as quinine is a substance and fluorescence is a process (and fluorescent the property) – so, presumably this should have read why is quinine fluorescent?

Why Quinine Glows

Quinine contains rare earth compounds called phosphors. … Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light.
https://allfamousbirthday.com/faqs/does-tonic-water-make-things-glow-in-the-dark/

"Want to know one more fun fact about quinine? It glows.
Rare Earth compounds called phosphors in quinine glow under certain circumstances."
https://www.mixlycocktailco.com/blogs/news/does-tonic-water-go-bad

Why Does Tonic Water Glow Under UV Rays?

Tonic water glows and [sic] will fluoresce under UV rays because of quinine in it. Quinine is one of the most important alkaloids found in the cinchona bark, among many others. It has some rare earth compounds known as phosphors that glow when they hit certain wavelengths of the UV light. Phosphors in the quinine absorb the UV light and then reflect it or emit it again in the form of glowing blue light.
https://www.sawanonlinebookstore.com/why-does-tonic-water-glow-under-uv-rays/

Making magic mud – or not

Perhaps the most bizarre example was a site, 'emaze' which offered to show me "How to create magic mud…in 17 easy steps"

Step 1 was

"wash your potatoes!!!!"

However, perhaps due to exclamation fatigue(!), this went in a different, if now familiar, direction with step 2:

"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light"
https://app.emaze.com/@AORQCIII#/16

This text was then repeated as each of steps 3-14. (Sadly steps 15-17 seemed to have been missed or lost. Or, perhaps not so sadly if they were just further repeats.) The first screen suggests this presentation was "done by Dr. Meena & Maha" but if Dr. Meena & Maha really exist (if you do, I am sorry, the internet makes me very sceptical) and 'done this', it is not clear if they got bored with their task very quickly, or whether the server managed to corrupt a much more coherent presentation when it was uploaded to the site.

This 'emaze' presentation seems to want to emphasise how quinine contains rare earth compounds…

According to Google, the site 'Course Hero' suggested

"Phosphors, which are found in quinine, are rare earth compounds. These chemicals glow when they are struck with particular wavelengths of the EM spectrum, …"
https://www.coursehero.com › Chemistry › 44733249–I…

but unfortunately (or perhaps fortunately given that snippet), the rest of the text seemed to be behind a pay-wall. This did not offer a strong incitement to pay for material on the site.

Toys coated with phosphorus?

Another website I came across was for a shop which claimed to be selling glow-in-the-dark objects that were made with phosoporus that needed to be illuminated to initiate a glow: a claim which seems not only scientifically incorrect (as mentioned above, phosphorus is not photoluminescent – it glows when in contact with air as it oxidises), and so unlikely; but, otherwise, dangerous and, surely, illegal.

Read about unscientific luminous creations

Defining scientific terms – badly

During my search, I came across a website (grammarist.com) offering to explain the difference between the words phosphorous and phosphorus. It did not discuss rare earths, but informed readers that

"Phosphate: Noun that means an electrically charged particle.
Phosphorus: Also a noun that means a mineral found in phosphate."
…We've already established that phosphorus is the simple mineral found in the particle phosphate, but phosphor is something else altogether."
https://grammarist.com/spelling/phosphorous-phosphorus/

So, that's 'no', 'no', 'no', and…I think at least one more 'no'.

Phosphorus is a reactive element, and is not found in nature as a mineral. To a scientist, a mineral is a material found in nature – as a component of rocks. Unfortunately, in discussing diet, the term minerals is often associated with elements, such as, for example, phosphorus, iodine, potassium and iron that are necessary for good health. However, one would not eat the element iron, but rather some compound of it. (Foods naturally contain iron compounds). And trying to eat phosphorus, iodine or potassium (rather than compounds of them) would be very hazardous.

So, whilst a nutritional supplement might well contain some minerals in the composition, strictly they are there as compounds that will provide a source of biologically important elements, and they will be metabolised into other compounds of those elements. (Iron from iron compounds will, for example, be used in synthesising the haem incorporated into red blood cells.) Unfortunately, learners commonly have alternative conceptions ('misconceptions') about the difference between mixtures and compounds and assume a compound maintains the properties of its 'constituent' elements (Taber, 1996).

"Compound is one or more elements mixed together"
alternative conception elicited from an Advance level chemisty student

The grammarist.com entry helpfully warned us that phosphate was "not to be confused with phosphoric acid, a chemical compound found in detergents and fertilizers". I suspect it is only found in detergents and fertilisers when something has gone wrong with the production process (notwithstanding diluted phosphoric acid has been used directly as a fertiliser) ⁴. It is a corrosive and irritant substance that can cause bronchitis – although tiny amounts are added to some colas. [n.b., cocaine also once featured in some cola, but that is no longer allowed.]

An ion is an electrically charged particle
The phosphate ion is one example of a type of ion.
Phosphates (such as calcium phosphate) are substances that contain phosphate ions.

So, phosphates contain electrically charged particles (phosphate ions), but that does not make phosphate an electrically charged particle, just as

blue does not mean a large marine mammal
bank does not mean a day of celebration where people do not need to go to work
vice does not mean a senior executive officer
motor does not mean a two wheeled vehicle
compact does not mean a flat circular object
final does not mean a simple musical instrument played with the breath
free does not mean a meal taken around noon or soon after, and
meal does not mean a token that provides entry or service

Grammarist invited feedback: I sent it some, so hopefully by the time you read this, the entry will have been changed.

It was on the internet: it must be true

The internet is an immense and powerful tool giving access to the vast resources of the World Wide Web. Unfortunately, the downside of a shared, democratic, free to access, reservoir of human knowledge is that there is no quality control. There is a lot of really good material on the web: but there is also a lot of nonsense on the web.

One example I have referred to before is the statement:

"energy is conserved in chemical reactions so can therefore be neither created nor destroyed"

This has the form of a logical structure

X so therefore Y

which is equivalent to

Y because X:

"energy can be neither created nor destroyed because it is conserved in chemical reactions"

This is just nonsense. There is no logical reason why the conservation of energy in chemical reactions implies a general principle of energy conservation.

We can deduce the specific from the general (days have 24 hours, so Sunday has 24 hours) but not the general from the specific (January has 31 days, so ~~months have 31 days~~).

Perhaps this is easily missed by people who already know that energy is always conserved.

A parallel structure might be:

"association football teams always consist of eleven players so therefore sports teams always consist of eleven players"

"sports teams always consist of eleven players because association football teams always consist of eleven players"

This is 'obviously' wrong because we know that rugby teams and netball teams and volleyball teams and water polo teams (for example) do not consist of eleven players.

Yet, if you search for "energy can be neither created nor destroyed because it is conserved in chemical reactions", you will find that this claim is included on the public websites of many schools (Taber, 2020). That is because, despite being wrong, it has authority – it is included in the English National Curriculum for Science (which I find shocking – we all make mistakes, but did nobody check the document before publication?) The English government department responsible was made aware of the error but does not think that it is a priority to make corrections to the curriculum.

Artificial (ignorant) intelligence

But what about quinine containing rare earth compounds? A notion that is structurally similar to claiming that

France contains South American countries, or
'Great Expectations' contains Jane Austin novels, or
February contains Autumn months, or
Cauliflower contains citrus fruits, or
Beethoven's 5th Symphony contains Haydn concerti

(in other words, something obviously silly to someone who has a basic understanding of the domain – chemistry or geography or literature or the calender or botany/horticulture or music – because it suggest one basic unit contains other units of similar status).

How does this error appear so often? Quite likely, a lot of website now are populated with material collected and collated by machines from other websites. If so, it only takes one human being (or government department) to publish something incorrect, and in time it is likely to start appearing in various places on the web.

There is currently a lot of talk of how artificial intelligence (AI) is getting better at writing essays, and answering questions, and even drafting lectures for busy academics. AI seemingly has great potential where it is provided with high quality feedback. Perhaps, but where the AI is based on finding patterns in publicly available texts, and has no real ability to check sense, then I wonder if the www is only going to become more and more polluted with misinformation and nonsense.

I do not know where Lucy Jane Santos got the idea that there are other substances in the single substance quinine (akin to having other countries in France), but if she did a web-search and relied on what she read, then I am in no position to be critical. I use the web to find things out and check things all the time. I am likely to spot gross errors in fields where I already have a strong background…but outside of that? I do seek to evaluate the likely authority of sources – but that does not mean I could not be taken in by a site which looked professional and authoritative.

The web started with imperfect people (because we all are) posting all kinds of material – with all kinds of motivations. I expect most of it was well-meaning, and usually represented something the poster actually believed; and indeed much of it was valid. However, a 'bot' can search, copy, and paste far quicker than a person, and if the internet is increasingly authored by programs that are indiscriminately copying bits and pieces from elsewhere to collage new copy to attract readers to advertising, then one cannot help wonder if the proportion of web-pages that cannot be trusted will be incrementally coming to dominate the whole network.

I (a fallible, but natural intelligence) hope not, but I am not very optimistic.

Work cited:

Santos, Lucy Jane (2020) Half lives. The unlikely story of radium. Icon.
Taber, K. S. (1996). Chlorine is an oxide, heat causes molecules to melt, and sodium reacts badly in chlorine: a survey of the background knowledge of one A level chemistry class. School Science Review, 78(282), 39-48. [ Download this article]
Taber, K. S. (2020). Conceptual confusion in the chemistry curriculum: exemplifying the problematic nature of representing chemical concepts as target knowledge. Foundations of Chemistry, 22: 309-334. https://doi.org/10.1007/s10698-019-09346-3 [Open Access – download for free]

Notes:

¹ Although my own research has been in science education and not one of the natural sciences, I am pleased that the learned societies (e.g. the Institute of Physics, the Royal Society of Chemistry, etc.) and the UK's Science Council, recognise the work of science educators as professional contributions to science.

² One internet site suggests:

Luminescence is caused by various things like electric current, chemical reactions, nuclear radiation, electromagnetic radiation, etc. But phosphorescence takes place after a sample is irradiated with light.

• Phosphorescence remains for sometime even after the lighting source is removed. But luminescence is not so.
https://www.differencebetween.com/difference-between-luminescence-and-vs-phosphorescence/

The second paragraph is nonsensical since phosphorescence is a type of luminescence. (It should be, "…fluorescence" that does not.) The first paragraph seems reasonable except that the 'but' seems misplaced. However 'in the light of' the second sentence (which sees phosphorescence and luminescence as contrary) it seems that the (contrasting) 'but' was intended, and whoever wrote this did not realise that light is a form of electromagnetic radiation.

Another, more technical, site suggests,

Luminescence is the emission of light by a substance as a result of a chemical reaction (chemiluminescence) or an enzymatic reaction (bioluminescence).
https://www.moleculardevices.com/technology/luminescence

Here again a contrast is set up:

chemiluminescence (due to a chemical reaction) versus
bioluminescence (due to an enzymatic reaction).

However, the keen-eyed will have spotted that "an enzymatic reaction" is simply a chemical reaction catalysed by an enzyme. So, bioluminescence is a subtype of chemiluminescence, not something distinct.

³ Some sources claim that the medicinal properties of cinchona bark were discovered by Jesuit missionaries that travelled to South America as part of European imperial expansion there.

Nataly Allasi Canales of the Natural History Museum of Denmark, University of Copenhagen is reported as explaining that actually,

"Quinine was already known to the Quechua, the Cañari and the Chimú indigenous peoples that inhabited modern-day Peru, Bolivia and Ecuador before the arrival of the Spanish…They were the ones that introduced the bark to Spanish Jesuits."
https://www.bbc.com/travel/article/20200527-the-tree-that-changed-the-world-map

Learning about the history of indigenous technologies can be complicated because:

often they are transmitted by an oral and practice culture (rather than written accounts);
traditional practices may be disrupted (or even suppressed) by colonisation by external invaders; and
European colonisers, naturalists and other travellers, often did not think their indigenous informants 'counted', and rather considered (or at least treated) what they were shown as their own discoveries.

⁴ This again seems to reflect the common alternative conception that confuses mixtures and compounds (Taber, 1996): phosphoric acid is used in reactions to produce fertilizers and detergents, but having reacted is no longer present. It is a starting material, but not an ingredient of the final product.

Just as we do not eat iron and phosphorus, we do not use washing powders that contain phosphoric acid, even if they have been prepared with it. (Increasingly, phosphates are being replaced in detergents because of their polluting effects on surface water such as rivers and lakes.)

⁵ This gives the impression to me that the Department of Education sees schooling as little more than a game where students perform and are tested on learning whatever is presented to them, rather than being about learning what is worth knowing. There is surely no value in learning a logically flawed claim. Any student who understands the ideas will appreciate this statement is incorrect, but perhaps the English Government prefers testing for recall of rote learning rather than looking for critical engagement?

Unscientific luminous creations

Q: Which form of phosphorus both glows and is non toxic?

Keith S. Taber

I have just sent of an email to a company claiming to be selling glow-in-the-dark products containing non-toxic phosphorus…

The site offers answers to a range of questions, but unfortunately gets a lot wrong

Dear Pete's Luminous Creations

I am writing to raise concern about misleading information on your website, specifically some of the claims made on the page:

https://www.darkniteglow.com/phosphorus-glow-in-the-dark-vs-radium-glow-in-the-dark/

(accessed today, 18th March 2023).

This page contains a number of scientifically incorrect statements, but I am most concerned about your misleading characterisation of phosphorus as a 'safe' material.

Scientific errors

Your site claims that

"phosphorus…has the ability to absorb and store surrounding light"
"the ability to absorb and store surrounding light…works similar to the natural process of photosynthesis"
"Phosphorus glow absorbs and stores surrounding light. When it is dark, the stored light is slowly released in the form of a glow"
"Glow in the Dark products contain phosphorus…it needs to be exposed to light before it can work"
"Radium glow produces light on its own through a chemical process."

All of these claims are mistaken.

1. Luminescent materials do not store light. Light cannot be stored, it is a form of electromagnetic radiation. (In LASERS light is contained within a cavity by reflecting it back and forth by mirrors, but phosphorus is not able to do anything like this.) When the radiation is absorbed by a photoluminescent material the radiation ceases to exist. Because the molecules of the absorbing material are excited into a higher energy state, new electromagnetic radiation (light) may later be emitted – but it is not light that has been stored. (The energy transferred to the luminescent material by the radiation may be considered as stored: but not the light).

2. The process of photosynthesis does not involve "the ability to absorb and store surrounding light" – absorb, yes, but the light is not stored – it ceases to exist once absorbed.

3. Materials which absorb energy from radiation, and then release it slowly ('glow') are called phosphorescent. This does not (only) occur 'when it is dark', but from immediately after irradiation. (The process occurs regardless of whether it is dark enough to observe.)

4. Phosphorus is not itself a phosphorescent material. The glow seen around white phosphorus is due to a chemical reaction with oxygen in the air. Not only does this not store any light, but, also, it does not need light to initiate.

5. Radium does NOT produce light through a chemical process. Radium is radioactive. It undergoes radioactive decay (due to a change in the atomic nucleus). This is NOT considered a chemical process.

Now I turn to what I consider a more serous problem with your site.

Potentially dangerous misinformation

The more serious matter concerns your claim that to be selling products containing 'non toxic' phosphorus:

"Glow in the Dark products contain phosphorus (a non toxic substance) which has the ability to absorb and store surrounding light…"
"Phosphorus is non toxic and safe for general use."
"Phosphorus is a natural mineral found in the human body. Phosphorus Glow in the dark products is perfectly safe for everyday use"
"Many get confused and associate all green glow products to be radioactive. This is not true. Phosphorus glow is non toxic and non radioactive."

You may wonder why I think this matters enough to contact you.

It is very misleading to suggest to people reading the site (which could include children who might well be interested in glow-in-the-dark toys) that phosphorus is harmless, and this is completely wrong.

Phosphorus is not found as a natural mineral, as it is much too reactive to be found native (that is, as phosphorus) on earth – although many minerals are compounds of phosphorus (and thus do NOT share its chemical properties), and so sources of the element for use in agriculture etc. The human body does contain compounds of phosphorus, notably in the bones, but again there is no phosphorus (the substance phosphorus) in the human body – if you introduced some it would very quickly react. Sources of phosphorus are important in the diet, but it would be very unwise to try to eat phosphorus itself.

Phosphorus can be obtained in different forms (this is called allotropy where the same element can have different molecular structures – like graphite and diamond both being pure forms – allotropes -of carbon). Some allotropes of phosphorus are not especially dangerous. However, the form which glows is white (or yellow) phosphorus, and this is a very hazardous material.

So, handling phosphorus is dangerous and needs special precautions. (If you really did use phosphorus in your products, I imagine you would know that?) Here is some information from authoritative websites

"Ingestion of elemental white or yellow phosphorus typically causes severe vomiting and diarrhea [diarrhoea], which are both described as "smoking," "luminescent," and having a garlic-like odor. Other signs and symptoms of severe poisoning might include dysrhythmias, coma, hypotension, and death. Contact with skin might cause severe burns within minutes to hours…"
US Centres for Disease Control

"White phosphorus is extremely toxic to humans, while other forms of phosphorus are much less toxic. Acute (short-term) oral exposure to high levels of white phosphorus in humans is characterised by three stages: the first stage consists of gastrointestinal effects; the second stage is symptom-free and lasts about two days; the third stage consists of a rapid decline in condition with gastrointestinal effects, plus severe effects on the kidneys, liver, cardiovascular system, and central nervous system (CNS). Inhalation exposure has resulted in respiratory tract irritation and coughing in humans. Chronic (long-term) exposure to white phosphorus in humans results in necrosis of the jaw, termed "phossy jaw."
US Environmental Protection Agency

Please feel free to check on this information for yourself.

However, I recommend you change the information on your website. In particular, please stop suggesting that phosphorus is a safe, non-toxic material, when the form of phosphorus which glows is highly toxic. I trust that now this has been brought to your attention, you will appreciate that it would be highly irresponsible for you to continue to advertise your products using misleading information about a hazardous substance.

Best wishes

Keith

Batteries – what are they good for?

Okay, 'energy storage' – but what else are they good for?

Keith S. Taber

I was struck by an item on the BBC Radio 4 news headlines at 09.00 this morning (27th Feb. 2023):

"The collapsed battery maker Britishvolt which went into administration last month has been bought by an Australian company.
The new owners will focus initially on batteries for energy storage rather than electric vehicles."
BBC Radio 4 news item

Now on reflection, this was an ambiguous statement. I heard it as

"The new owners will focus initially on batteries for

energy storage, rather than

electric vehicles."

Which immediately provoked in my mind the question what batteries might be used for in electric vehicles – if not 'energy storage'?

It is possible to charge up an electric car because it includes a battery
(Image by Sabine Kroschel from Pixabay)

Conceptions of energy

Now, this whole area is, metaphorically, a bit of a linguistic minefield as when people say batteries they do not usually distinguish between an individual cell and a battery (of cells). Traditional electrochemical cells we are familiar with have a specific and usually modest e.m.f. – 1.5V or 1.2 V for example. The old 6V and 9V batteries that used to be commonly sold for many purposes (before the switch to most appliances having internal batteries) would be batteries of cells connected in series to work together to provide (1.5V + 1.5V + 1.5V + 1.5V = ) 6V (or whatever). Car batteries were traditionally batteries of lead-acid cells connected together. If each cell has an e.m.f. of 2V, then a dozen connected in series (i.e., the battery) offers 24V.

Moreover, energy is a highly abstract idea, such that even physics teachers do not always agree on how to describe it – the model of energy coming in a number of flavours, 'forms', and processes involving transformations in the form of the energy (e.g., a filament lamp converts electrical energy into heat energy) that many of us learnt (and some of us taught) has come to be seen as misleading and unhelpful by some (it not all) educators. Oh, and if you think I made a mistake there and forget that a lamp produces light energy – not at all. In the 'forms of energy' typology, heat is energy transferred due to a difference in temperature – so that covers all the radiation being emitted by the hot filament.

No wonder, that energy is a common topic for student alternative conceptions, as energy permeates (so to speak) all areas of science, but is a highly abstract notion.

Read about conceptions of energy

An alternative hearing?

Yet, I realised that the statement I had heard was ambiguous and could be parsed differently. It perhaps meant

"The new owners will focus initially on

batteries for energy storage

rather than

electric vehicles."

That is, I was putting my imaginary brackets in the wrong place and perhaps the company had previously intended to build complete electric cars and not just the batteries? If so, the news was not

The new owners will focus initially on batteries (for energy storage rather than electric vehicles).

but rather that

The new owners will focus initially on (batteries for energy storage) rather than (electric vehicles).

If this was the intention, it might have been better to have assumed listeners would know that batteries were used for 'energy storage', and to have simplified the statement to

"The new owners will focus initially on batteries rather than electric vehicles."

Batteries for under-performing sports cars?

That made more sense, as surely the BBC's news journalists do not think electric batteries in cars are used for something other than 'energy storage'. So, I checked on the BBC news website, where I found

"The company intends to start by focusing on batteries for energy storage and hopes to have those products available by the end of 2025.

It then intends to produce batteries for high-performance sports cars."
https://www.bbc.co.uk/news/business-64754879

So, I did not misinterpret the news item. According to the BBC (and to be fair, they are probably just reporting, albeit uncritically, what they have been told) under its new owners Britishvolt will

first work on batteries that can be used for energy storage, and
then shift attention to batteries for sports cars.

My best guess is that "batteries for energy storage" is shorthand for large scale devices for long term storage (that could, for example, be charged by wind generators when it is windy, and then later fed into the National Grid at times of high power demand). The characteristics of these devices would surely be different in detail from batteries used in electric vehicles.

However, I am pretty sure that "batteries for high-performance sports cars" also need to provide 'energy storage' or else those cars are not going to offer the kind of performance Britishvolt and the car manufacturers they will supply are looking for. After all, besides 'energy storage', what else are batteries actually good for?

Another late night writing copy in the newsroom?
(Image by mohamed_hassan from Pixabay)

A molecular Newton's cradle?

A chain reaction with no return

Keith S. Taber

Have chemist's created an atomic scale Newton's cradle?

(Image by Michelle from Pixabay)

Mimicking a Newton's cradle

I was interested to read in an issue of Chemistry World that

"Scientists in Canada have succeeded in setting off a chain of reactions in which fluorine atoms are passed between molecules tethered to a copper surface. The sequence can be repeated in alternating directions, mimicking the to-and-fro motions of a Newton's cradle."
Blow, 2022

The Chemistry World report explained that

"The team of researchers…affixed fluorocarbons to a [copper] surface by chemisorption, constructing chains of CF₃ molecules terminated by a CF₂molecule – up to four molecules in total….

The researchers applied an electron impulse to the foremost CF₃ molecule, causing it to spit out a fluorine atom along the chain. The second CF₃ absorbed this atom, but finding itself unstable, ejected its leading fluorine towards the third molecule. This in turn passed on a fluorine of its own, which was taken up by the taken up by the CF₂ molecule in fourth position."
Blow, 2022

There is some interesting language here – a molecule "spits out" (a metaphor?) an atom, and another "finds itself" (a hint of anthropomorphism?) unstable.

Molecular billiards?
Can a line of molecules 'tethered' onto a metal surface behave like a Newton's cradle?

Generating reverse swing

The figure below was drawn to represent the work as described, showing that "another electron impulse could be used to set… off…a reverse swing".

A representation of the scheme described in *Chemistry World*. The different colours used for the fluorine 'atoms' ¹ are purely schematic to give a clear indication of the changes – the colours have no physical significance as all the fluorine atoms are equivalent. ² The molecules are shown here as if atoms were simply stuck to each other in molecules (rather than having become one larger multi-nuclear structure) for the same reason. ¹ In science we select from different possible models and representations for particular purposes.³

That reference to "another electron impulse" being needed is significant,

"What was more, each CF₃ had been flipped in the process, so the Newton's cradle as a whole was a mirror image of how it had begun, giving the potential for a reverse swing. Unlike a desk Newton's cradle, it did not swing back on its own accord, but another electron impulse could be used to set it off."
Blow, 2022

"***…the Newton's cradle as a whole was a mirror image of how it had begun***"

Mirroring a Newton's cradle

Chemistry World is the monthly magazine of the Royal Society of Chemistry (a learned society and professional body for chemists, primarily active in the UK and Eire) sent to all its members. So, Chemistry World is part of the so-called secondary literature that reports, summarises, and comments on the research reports published in the journals that are considered to comprise the primary academic literature. The primary literature is written by the researchers involved in the individual studies reported. Secondary literature is often written by specialist journalists or textbook authors.

The original report of the work (Leung, Timm & Polanyi, 2021) was published in the research journal Chemical Communications. That paper describes how:

"Hot [sic] F-atoms travelling along the line in six successive 'to-and-fro' cycles paralleled the rocking of a macroscopic Newton's cradle."
Leung, Timm & Polanyi, 2021, p.12647

A simple representation of a Newton's cradle (that is, "*a macroscopic Newton's cradle*")

These authors explain that

"…energised F can move to- and-fro. This occurs in six successive linear excursions, under the influence of electron-induced molecular dissociation at alternate ends of the line…. The result is a rocking motion of atomic F which mirrors, at the molecular scale, the classic to-and-fro rocking of a macroscopic Newton's cradle. Whereas a classic Newton's cradle is excited only once, the molecular analogue [⁴] here is subjected to opposing impulses at successive 'rocks' of the cradle.

The observed multiple knock-on of F-atoms travelling to-and-fro along a 1D row of adsorbates [molecules bound to a substrate] is shown…to be comparable with the synchronous motion of a Newton's cradle."
Leung, Timm & Polanyi, 2021, p.12647-50

Making molecules rock?

'Rocking' refers to a particular kind of motion. In a macroscopic context, there are familiar example of rocking as when a baby is cradled in the arms and gently 'rocked' back and forth.

A rocking chair is designed to enable a rocking motion where the person in the chair moves back and forth through space.

The molecular system described by Leung and colleagues is described as "mirror[ing], at the molecular scale…to-and-fro rocking"

[Image by OpenClipart-Vectors from Pixabay]

The researchers are suggesting that, in some sense, the changes in their molecular scale system are equivalent to "the synchronous motion of a Newton's cradle".

Titles and texts in scientific writing

One feature of interest here is a difference between the way work is described in the article titles and the main texts.

	Chemistry society professional journal	Academic research journal
Title	*"…molecular Newton's cradle"*	*"…an atomic-scale Newton's cradle"*
Text	The effect was "mimicking … a Newton's cradle."	The effect "paralleled… mirrors… [is] comparable with" Newton's cradle

Bold titles: nuanced details

Titles need to capture the reader's attention (and in science today the amount of published material is vastly more than only one person could read) so there is a tendency to be bold. Both these articles have titles suggesting that they are reporting a nanoscopic Newton's cradle. The reader enticed to explore further then discovers that there are caveats. What is being claimed is not a Newton's cradle at minuscule scale but something which though not actually a Newton's cradle, does have some similarity to (mimics, parallels, mirrors) one.

This is important as "the molecular analogue" is only analogous in some respects.

The analogy

There is an analogy, but the analogy can only be drawn so far. In the analogy, the suspended balls of the Newton's cradle are seen as analogous to the 'chemisorbed' molecules lined up on the surface of a copper base.

Analogies are used in teaching and in science communication to help 'make the unfamiliar familiar', to show someone that something they do not (yet) know about is actually, in some sense at least, a bit like something they are already familiar with. In an analogy, there is a mapping between some aspect(s) of the structure of the target ideas and the structure of the familiar phenomenon or idea being offered as an analogue. Such teaching analogies can be useful to the extent that someone is indeed highly familiar with the 'analogue' (and more so than with the target knowledge being communicated); that there is a helpful mapping across between the analogue and the target; and that comparison is clearly explained (making clear which features of the analogue are relevant, and how).

Analogies only map some features from analogue to target. If there was a perfect transfer from one system to the other, then this would not be an analogy at all, but an identity! So, in a sense there are no perfect analogies as that would be an oxymoron. Understanding an analogy as intended therefore means appreciating which features of the analogue do map across to the target, and which do not. Therefore in using analogies in teaching (or communicating science) it is important to be explicit about which features of the analogue map across (the 'positive' analogy) and which do not, including features which it would be misleading to seek to map across – the so called 'negative analogy.' For example, when students think of an atom as a tiny solar system, they may assume that atom, like the solar system, is held together by gravitational force (Taber, 2013).

It probably seems obvious to most science teachers that, if comparing the atom with a solar system, the role that gravity has in binding the solar system maps across to the electrical attraction between a positive nucleus and negative electrons; but when a sample of 14-18 year-olds were asked about atoms and solar systems, a greater number of them suggested the force binding the atom was gravitational than suggested it was electrical (Taber, 2013)!

Perhaps the most significant 'negative analogy' in the research discussed here was pointed out in both the research paper and the subsequent Chemistry World report, and relates to the lack of inherent oscillation in the molecular level system. The nanoscopic system is like a Newton's cradle that only has one swing, so the owner has to reset it each half cycle.

"Unlike a desk Newton's cradle, it did not swing back on its own accord, but another electron impulse could be used to set it off."
"Whereas a classic Newton's cradle is excited only once, the molecular analogue here is subjected to opposing impulses at successive 'rocks' of the cradle"

That is quite a major difference when using the Newton's cradle for an analogy.

Image by Peggy und Marco Lachmann-Anke from Pixabay

Who wants a Newton's cradle as an executive toy if it needs to be manually reset after each swing?

The positive and negative analogies

We can consider that the Newton's cradle is a little like a simple pendulum that swings back and forth, with the complication that instead of a single bob swinging back and forth, the two terminal spheres share the motion between them due to the momentum acquired by one terminal sphere being transferred thorough the intermediate spheres to the other terminal sphere.

In understanding the analogy it is useful to separately consider these two features of a Newton's cradle

a) the transfer of momentum through the sequence
b) moving a mass through a gravitational field

If we then think of the Newton's cradle as a 'pendulum with complications' it seems that the molecular system described by Leung and colleagues fails to share a critical feature of a pendulum.

A chain reaction – the positive analogy

The two systems map well in so far as that they comprise a series of similar units (spheres, molecules) that are carefully aligned, and constrained from moving out of alignment, and that there is a mechanism that allows a kind of chain reaction.

In the molecular scenario, the excitation of a terminal molecule causes a fluorine atom to become unbound from the molecule and to carry enough momentum to collide with and excite a second molecule, binding to it, whilst causing the release of one of the molecule's original fluorine atoms which is similarly ejected with sufficient momentum to collide with the next molecule…

This 'chain reaction' ⁵ is somewhat similar to how, in a Newton's cradle, the momentum of a swinging sphere is transferred to the next, and then to the next, and then the next, until finally all the momentum is transferred to the terminal sphere. (This is an idealised cradle, in any real cradle the transfer will not be 100% perfect.) This happens because the spheres are made from materials which collide 'elastically'.⁶

The positive analogy: The notion of an atomic level Newton's cradle makes use of a similarity between two systems (at very different scales) where features of one system map onto analogous features of the other.

The negative analogy

Given that positive mapping, a key difference here is the way the components of the system (suspended spheres or chemisorbed molecules) are 'tethered'.

Chemisorbed molecules

The molecules are attached to the copper surface by chemical bonding, which is essentially an electromagnetic interaction. A sufficient input of energy could certainly break these bonds, but the the impulse being applied parallel to the metal surface is not sufficient to release the molecules from the substrate. It is enough to eject a fluorine atom from a molecule where carbon is already bound to the surface and three other fluorines atoms (carbon is tetravalent, but it is is bonded to the copper as well as the fluorines) – but the final molecule is an adsorbed CF₂ molecule, which 'captures' the fluorine and becomes an absorbed CF₃ molecule.

Now, energy is always conserved in all interactions, and momentum is also always conserved. If the kinetic energy of the 'captured' fluorine atom does not lead to bond breaking it must end up somewhere else. The momentum from the 'captured' atom must also be transferred somewhere.

Here, it may be useful to think of chemical bonds as having a similarity to springs – in the limited sense that they can be set vibrating. If we imagine a large structure made up of spheres connected by springs, we can see that if we apply a force to one of the spheres, and the force is not enough to break the spring, the sphere will start to oscillate, and move any spheres connected to it (which will move spheres attached to them…). We can imagine the energy from the initial impulse, and transferred through the chain of molecules, is dissipated though the copper lattice, and adds to its internal energy. ⁷

The fluorocarbon molecules are bound to the surface by chemical bonding. If the energy of impact is insufficient to cause bond breaking, it will be dissipated.

Working against gravity

In a simple pendulum, work is done on a raised sphere by the gravitational field, which accelerates the bob when it is released, so that it is moving at maximum speed when it reaches the lowest point. So, as it is moving, it has momentum, and its inertia means it continues to swing past the equilibrium position which is the 'attractor' for the system. In a Newton's cradle the swinging sphere cannot continue when it collides with the next sphere, but as its momentum is transferred through the train of spheres the other terminal sphere swings off, vicariously continuing the motion.

In an ideal pendulum with no energy losses the bob rises to its original altitude (but on the other side of the support) by which time it has no momentum left (as gravitational force has acted downwards on it to reduce its momentum) – but gravitational potential energy has again built up in the system to its original level. So, the bob falls under gravity again, but, being constrained by the wire, does not fall vertically, rather it swings back along the same arc.

It again passes the equilibrium position and returns to the point where it started, and the process is repeated. In an ideal pendulum this periodic oscillation would continue for ever. In a real pendulum there are energy losses, but even so, a suitable bob can swing back an forth for some time, as the amplitude slowly reduces and the bob will eventually stop at the attractor, when the bob is vertical.

In a (real) Newton's cradle, one ball is raised, so increasing the gravitational potential energy of the system (which is the configuration of the cradle, with its spheres, plus the earth). When it is released, gravity acts to cause the ball to fall. It cannot fall vertically as it is tethered by a steel (or similar) wire which is barely extendible, so the net force acting causes the ball to swing though an arc, colliding with the next ball.

The Newton's cradle design allows the balls to change their 'height' in relation to a vertical gravitational field direction – in effect storing energy in a higher gravitational field configuration that can do work to continue the oscillation. The molecular analogue⁴ does not include an equivalent mechanism that can lead to simultaneous oscillation.
(Image by 3D Animation Production Company from Pixabay)

Two types of force interactions

The steel spheres, however, are actually subject to two different kinds of force. They are, like the molecules, also tethered by the electromagnetic force (they are attached to steel wires which are effectively of fixed length due to the bonding in the metal ⁸), but, in addition, subject to the gravitational field of the earth. ⁹ The gravitational field is relevant because a sphere is supported by a wire that is fixed to a rigid support (the cradle) at one end, but free to swing at the end attached to the sphere.

The Newton's cradle operates in what is in effect a uniform gravitational field (neither the radial nature or variation with altitude of the earth's field are relevant on the scale of the cradle) – and the field direction is parallel to the plane in which the balls hang. So, the gravitational potential of the system changes as a sphere swings higher in the field.

In a Newton's cradle, a tethered sphere's kinetic energy allows it to rise in a gravitational field, before swinging back gaining speed (and regaining kinetic energy)

The design of the system is such that a horizontal impulse on a sphere leads to it swinging upwards – and gravity then acts to accelerate it towards a new collision. ¹⁰ This collision, indirectly, gives a horizontal impulse to the sphere at the other end of the 'train' where again the nature of the support means the sphere swings upward – being constrained by both the wire maintaining its distance from the point of suspension at the rigid support of the frame, and its weight acting downwards.

The negative analogy concerns the means of constraining the system components

The two systems then both have a horizontal impulse being transferred successively along a 'train' of units. Leung and colleagues' achievement of this at the molecular scale is impressive.

However, the means of 'tethering' in the two systems is different in two significant ways. The spheres in the Newton's cradle are suspended from a rigid frame by inextensible wires that are free to swing. Moreover, the cradle is positioned in a field with a field direction perpendicular to the direction of the impulse. This combination allows horizontal motion to be converted to vertical motion reversibly.

The molecular system comprises molecules bound to a metal substrate. The chemisorbtion is less like attaching the molecules with long wires that are free to swing, and more like attaching them with short, stiff springs. Moreover, at the scale of the system, the substrate is less like a rigid frame, and more like a highly sprung mattress. So, even though kinetic energy from the 'captured' fluorine atom can be transferred to the bond, this can then be dissipated thorough the lattice.

The negative analogy: the two systems fail to map across in a critical way such that in a Newton's cradle one initial impulse can lead to an extended oscillation, but in the molecular system the initiating energy is dissipated rather than stored to reverse the chemical chain reaction.

The molecular system does not enable the terminal molecule to do work in some form that can be recovered to reverse the initial process. By contrast, a key feature of a Newton's cradle is that the spheres are constrained ('tethered') in a way that allows them to move against the gravitational field – they cannot move further away from, nor nearer to, their point of support, yet they can swing up and down and change their distance from the earth. Mimicking that kind of set-up in a molecular level system would indeed be an impressive piece of nano-engineering!

Work cited:

Blow, M. (2022). Molecular Newton's cradle challenges theory of transition states. Chemistry World, 19(1), 38.
Leung, L., Timm, M. J., & Polanyi, J. C. (2021). Reversible 1D chain-reaction gives rise to an atomic-scale Newton's cradle. Chemical Communications, 57(94), 12647-12650. doi:10.1039/D1CC05378G
Taber, K. S. (2013). Upper Secondary Students' Understanding of the Basic Physical Interactions in Analogous Atomic and Solar Systems. Research in Science Education, 43(4), 1377-1406. doi:10.1007/s11165-012-9312-3 (The author's manuscript version may be downloaded here.)

Notes

¹ Strictly they are no distinct atoms once several atoms have been bound together into a molecule, but chemists tend to talk in a shorthand as if the atoms still existed in the molecules.

² Whilst I expect this is obvious to people who might choose to read this posting, I think it is worth always being explicit about such matters as students may develop alternative conception at odds with scientific accounts.

In the present case, I would be wary of a learner thinking along the lines "of course the atom will go back to its own molecule"

Students will commonly transfer the concepts of 'ownership' and 'belonging' from human social affairs to the molecular level models used in science. Students often give inappropriate status to the history of molecular processes (as if species like electrons recall and care about their pasts). One example was a student who suggested to me that in homolytic bond breaking each atom would get its own electron back – meaning the electrons in the covalent bond would return to their 'own' atoms.

I have also been told that in double decomposition (precipitation) reactions the 'extra' electron in an anion would go back to its own cation in the reagents, before the precipitation process can occur (that is, precipitation was not due to the mutual attraction between ions known to be present in the reaction mixture: they first had to become neutral atoms that could then from an ionic bond by electron transfer!) In ionic bonding it is common for learners to think that an ionic bond can only be formed between ions that have been formed by a (usually fictitious) electron transfer event.

Read about common alternative conceptions of ionic bonding

Read about a classroom resource to diagnose common alternative conceptions (misconceptions) of ionic bonding

Read about a classroom resource to support learning about the reaction mechanism in precipitation reactions

³ I have here represented the same molecules both as atoms linked by bonds (where I am focusing on the transfer of fluorine atoms) and in other diagrams as unitary spheres (where I am focusing on the transfer of energy/momentum). All models and representations used for atoms and molecules are limited and only able to reflect some features of what is being described.

⁴ A note on terminology. An analogy is used to make the unfamiliar familiar by offering a comparison with something assumed to already be familiar to an audience, in this case the molecular system is the intended target, and the (that is, a generic) Newton's cradle is the analogue. However, analogy – as a mapping between systems – is symmetrical so each system can be considered the analogue of the other.

⁵ In some way's Leung's system is more like a free radical reaction than a Newton's cradle. A free radical is an atom (or molecule) with an unpaired electron – such as an unbound fluorine atom!

In a free radical reaction a free radical binds to a molecule and in doing so causes another atom to be ejected from the molecule – as a free radical. That free radical can bind to another molecule, again causing it to generate a new free radical. In principle this process can continue indefinitely, although the free radical could also collide with another free radical instead of a molecule, which terminates the chain reaction.

⁶ The balls need to be (near enough) perfectly elastic for this to work so the total amount of kinetic energy remains constant. Momentum (mv) is always conserved in any collision between balls (or other objects).

If there were two balls, then the first (swinging) sphere would be brought to a stop by the second (stationary) sphere, to which its momentum would be transferred. So, the first ball would stop swinging, but the second would swing in its place. The only way mv and mv² (and so kinetic energy) can be both conserved in collisions between balls of the same mass is if the combination of velocities does not change. That is, mathematically, the only solutions are where neither of the two balls' velocities change, or where they are swapped to the other permutation (here, the velocity of the moving ball becomes zero, but the stationary ball moves off with the velocity that the ball that hit it had approached it with).

The first solution would require the swinging steel ball to pass straight through the stationary steel ball without disturbing it. Presumably, quantum mechanics would suggest that ('tunnelling') option has a non-zero (but tiny, tiny – I mean really tiny) probability. To date, in all known observations of Newton's cradles no one has reported seeing the swinging ball tunnel though the stationary ball. If you are hoping to observe that, then, as they say, please do not hold your breath!

With more balls momentum is transferred through the series: only the final ball is free to move off.

⁷ We can imagine that in an ideal system of a lattice of perfectly rigid spheres attached to perfect springs (i.e., with no hysteresis) and isolated from any other material (n.b., in Leung et al 's apparatus the copper would not have been isolated from other materials), the whole lattice might continue to oscillate indefinitely. In reality the orderliness will decay and the energy will have in effect warmed the metal.

⁸ Strictly, the wires will be longest when the spheres are directly beneath the points of support, as the weight of a sphere slightly extends the wire from its equilibrium length, and it will get slightly shorter the further the sphere swings away from the vertical position. In the vertical position, all the weight is balanced by a tension in the wire. As the ball swings away from the vertical position, the tension in the wire decreases (as only the component of weight acting along the wire needs to be balanced) and an increasing component of the weight acts to decelerate it. But the change in extension of the wire is not significant and is not noticeable to someone watching a Newton's cradle.

When the wire support is not vertical a component of the weight of the sphere acts to change the motion of the sphere

⁹ Molecules are also subject to gravity, but in condensed matter the effect is negligible compared with the very much stronger electromagnetic forces acting.

¹⁰ We might say that gravity decelerates the sphere as is swings upwards and then accelerates as it swings back down. This is true because that description includes a change of reference direction. A scientist might prefer to say that gravity applies a (virtually) constant downward acceleration during the swing. This point is worth making in teaching as a very common alternative conception is to see gravity only really taking effect at the top of the swing.

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.

The passing of stars

Birth, death, and afterlife in the universe

Keith S. Taber

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

One of the themes I keep coming back to here is the challenge of communicating abstract scientific ideas. Presenting science in formal technical language will fail to engage most general audiences, and will not support developing understanding if the listener/reader cannot make good sense of the presentation. But, if we oversimplify, or rely on figures of speech (such as metaphors) in place of formal treatments of concepts, then – even if the audience does engage and make sense of the presentation – audience members will be left with a deficient account.

Does that matter? Well, often a level of understanding that provides some insight into the science is far better than the impression that science is so far detached from everyday experience that it is not for most people.

And the context matters.

Public engagement with science versus science education

In the case of a scientist asked to give a public talk, or being interviewed for news media, there seems a sensible compromise. If people come away from the presentation thinking they have heard about something interesting, that seems in some way relevant to them, and that they understood the scientist's key messages, then this is a win – even if it is only a shift to an over-simplified account, or an understanding in terms of a loose analogy. (Perhaps some people will want to learn more – but, even if not, surely this meets some useful success criterion?)

In this regard science teachers have a more difficult job to do. ¹ The teacher is not usually considered successful just because the learners think they have understood teaching, but rather only when the learners can demonstrate that what they have learnt matches a specified account set out as target knowledge in the curriculum. This certainly does not mean a teacher cannot (or should not) use simplification and figures of speech and so forth – this is often essential – but rather that such such moves can usually only be seen as starting points in moving learners onto temporary 'stepping stones' towards creditable knowledge that will eventually lead to test responses that will be marked correct.

The Death of Stars

With this in mind, I was fascinated by an episode of the BBC's radio show, 'In Our Time' which took as its theme the death of stars. Clearly, this falls in the category of scientists presenting to a general public audience, not formal teaching, and that needs to be borne in mind as I discuss (and perhaps even gently 'deconstruct') some aspects of the presentation from the perspective of a science educator.

The show was broadcast some months ago, but I made a note to revisit it because I felt it was so rich in material for discussion, and I've just re-listened. I thought this was a fascinating programme, and I think it is well worth a listen, as the programme description suggests:

"Melvyn Bragg and guests discuss the abrupt transformation of stars after shining brightly for millions or billions of years, once they lack the fuel to counter the force of gravity. Those like our own star, the Sun, become red giants, expanding outwards and consuming nearby planets, only to collapse into dense white dwarves. The massive stars, up to fifty times the mass of the Sun, burst into supernovas, visible from Earth in daytime, and become incredibly dense neutron stars or black holes. In these moments of collapse, the intense heat and pressure can create all the known elements to form gases and dust which may eventually combine to form new stars, new planets and, as on Earth, new life."
https://www.bbc.co.uk/sounds/play/m0018128

I was especially impressed by the Astronomer Royal, Professor Martin Rees (and not just because he is a Cambridge colleague) who at several points emphasised that what was being presented was current understanding, based on our present theories, with the implication that this was open to being revisited in the light (sic) of new evidence. This made a refreshing contrast to the common tendency in some popular science programmes to present science as 'proven' and so 'certain' knowledge. That tendency is an easy simplification that distorts both the nature and excitement of science.

Read about scientific certainty in the media

Presenter Melvyn Bragg's other guests were Carolin Crawford (Emeritus Member of the Institute of Astronomy, and Emeritus Fellow of Emmanuel College, University of Cambridge) and Mark Sullivan (Professor of Astrophysics at the University of Southampton).

Public science communication as making the unfamiliar familiar

Science communicators, whether professional journalists or scientists popularising their work, face similar challenges to science teachers in getting across often complex and abstract ideas; and, like them, need to make the unfamiliar familiar. Science teachers are taught about how they need to connect new material with the learners' prior knowledge and experiences if it is to make sense to the students. But successful broadcasters and popularisers also know they need to do this, using such tactics as simplification, modelling, metaphor and simile, analogy, teleology, anthropomorphism and narrative.

There were quite a few examples of the speakers seeking to make abstract ideas accessible to listeners in such ways in this programme. However, perhaps the most common trope was one set up by the episode title, and one which could very easily slip under radar (so to speak). In this piece I examine the seemingly ubiquitous metaphor (if, indeed, it is to be considered a metaphor!) of stars being alive; in a sequel I discuss some of the wide range of other figures of speech adopted in this one science programme.

Science: making the familiar, unfamiliar?

If when working as a teacher I saw a major part of my work as making the unfamiliar familiar to learners, in my research there was a sense in which I needed to make the familiar unfamiliar. Often, the researcher needs to focus afresh on the commonly 'taken-for-granted' and to start to enquire into it as if one does not already know about it. That is, one needs to problematise the common-place. (This reflects a process sometimes referred to as 'bracketing'.)

To give one obvious example. Why do some students do well in science tests and others less well? Obviously, because some learners are better science students than others! (Clearly in some sense this is true – but is it just a tautology? ²) But one clearly needs to dig into this truism in more detail to uncover any insights that would actually be useful in supporting students and improving teaching!

The same approach applies in science. We do not settle for tautologies such as fire burns because fire is the process of burning, or acids are corrosive because acids are the category of substances which corrode; nor what are in effect indirect disguised tautologies such as heavy objects fall because they are largely composed of the element earth, where earth is the element whose natural place is at the centre of the world. (If that seems a silly example, it was the widely accepted wisdom for many centuries. Of course, today, we do not recognise 'earth' as a chemical element.)

I mention this, because I would like to invite readers to share with me in making the familiar unfamiliar here – otherwise you could easily miss my point.

"so much in the Universe, and much of our understanding of it, depends on changes in stars as they die after millions or billions of stable years"
Tag line for 'the Death of Stars'

The lives of stars

The episode opens with

"Hello. Across the universe, stars have been dying for millions of years…
Melvyn Bragg introducing the episode

The programme was about the death of stars – which directly implies stars die, and, so, also suggests that – before dying – they live. And there were plenty of references in the programme to reinforce this notion. Carolin Crawford suggested,

"So, essentially, a star's life, it can exist as a star, for as long as it has enough fuel at the right temperature at the right density in the core of the star to stall the gravitational collapse. And it is when it runs out of its fuel at the core, that's when you reach the end of its lifetime and we start going through the death processes."
Prof. Carolin Crawford talking on 'In Our Time'

Not only only do stars have lives, but some have much longer lives than others,

"…more massive stars can … build quite heavy elements at their cores through their lifetimes. And … they actually have shorter lifetimes – it is counter-intuitive, but they have to chomp through their fuel supply so furiously that they exhaust it more rapidly. So, the mass of the star dictates what happens in the core, what you create in the core, and it also determines the lifetime of the star."

"The mass of the star…determines the lifetime of the star….
our sun…we reckon it is about halfway through its lifetime, so stars like the sun have lifetimes of 10 billions years or so…"

Prof. Carolin Crawford talking on 'In Our Time'

This was not some idiosyncratic way that Professor Crawford had of discussing stars, as Melvyn's other guests also used this language. Here are some examples I noted:

"this is a dead, dense star" (Martin Rees)
"the lifetime of a stable star, we can infer the … life cycles of stars" (Martin Rees)
"stars which lived and died before our solar system formed…stars which have more complicated lives" (Martin Rees)
"those old stars" (Martin Rees)
"earlier generations of massive stars which had lived and died …those long dead stars" (Martin Rees)
"it is an old dead star" (Mark Sullivan)
"our sun…lives by itself in space. But most stars in the universe don't live by themselves…" (Mark Sullivan)
"two stars orbiting each other…are probably born with different masses" (Mark Sullivan)
"when [stars] die" (Mark Sullivan)
"when [galaxies] were very young" (Martin Rees)
"stars that reach the end point of their lives" (Carolin Crawford )
"a star that's younger" (Martin Rees)

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 processes that support a star's luminosity come to an end: but does the star therefore die?

(Cover art for the Royal Philharmonic Orchestra's recording of David Bedford's composition Star's End. Photographer: Monique Froese)

Are stars really alive?

Presumably, the use of such terms in this context must have originally been metaphorical. Life (and so death) has a complex but well-established and much-discussed meaning in science. Living organisms have certain necessary characteristics – nutrition, (inherent) movement, irritability/sensitivity, growth, reproduction, respiration, and excretion, or some variation on such a list. Stars do not meet this criterion. ³ Living organisms maintain a level of complex organisation by making use of energy stores that allow them to decrease entropy internally at the cost of entropy increase elsewhere.

Animals and decomposers (such as fungi) take in material that can be processed to support their metabolism and then the 'lower quality' products are eliminated. Photosynthetic organisms such as green plants have similar metabolic processes, but preface these by using the energy 'in' sunlight to first facilitate endothermic reactions that allow them to build up the material used later for their mortal imperative of working against the tendencies of entropy. Put simply, plants synthesise sugar (from carbon dioxide and water) that they can distribute to all their cells to support the rest of the metabolism (a complication that is a common source of alternative conceptions {misconceptions} to learners ⁴).

By contrast, generally speaking, during their 'lifetimes', stars only gain and lose marginal amounts of material (compared with a 70 kg human being that might well consume a tonne of food each year) – and do not have any quality control mechanism that would lead to them taking in what is more useful and expelling what is not.

As far as life on earth is concerned, virtually all of that complex organisation of living things depends upon the sun as a source of energy, and relies on the process by which the sun increases the universe's entropy by radiating energy from a relatively compact source into the diffuse vastness of space. ⁴ In other words, if anything, a star like our sun better reflects a dead being such as a felled tree or a zebra hunted down by a lion, providing a source of concentrated energy for other organisms feeding on its mortal remains!

Are the lives and deaths of stars simply pedagogical devices?

So, are stars really alive? Or is this just one example of the kind of rhetorical device I referred to above being adopted to help make the abstract unfamiliar becomes familiar? Is it the use of a familiar trope employed simply to aid in the communication of difficult ideas? Is this just a metaphor? That is,

Do stars actually die, or…
are they only figuratively alive and, so, only suffer (sic) a metaphorical death?

I do not think the examples I quote above represent a concerted targeted strategy by Professors Crawford, Rees and Sullivan to work with a common teaching metaphor for the sake of Melvyn and his listeners: but rather the actual language commonly used in the field. That is, the life cycles and lifetimes of stars have entered into the technical lexicon of the the science. If so, then stars do actually live and die, at least in terms of what those words now mean in the discipline of astronomy.

Gustav Strömberg referred to "the whole lifetime of a star" in a paper in the The Astrophysical Journal as long ago as 1927. He did not feel the need to explain the term so presumably it was already in use – or considered obvious. Kip Thorne published a paper in 1965 about 'Gravitational Collapse and the Death of a Star". In the first paragraph he pointed out that

"The time required for a star to consume its nuclear fuel is so long (many billions of years in most cases) that only a few stars die in our galaxy per century; and the evolution of a star from the end point of thermonuclear burning to its final dead state is so rapid that its death throes are observable for only a few years."
Thorne, 1965, p.1671

Again, the terminology die/death/dead is used without introduction or explanation.

He went on to refer to

deaths of stars
different types of death
final resting states

before shifting to what a layperson would recognise as a more specialist, technical, lexicon (zero point kinetic energy; Compton wavelength of an electron; neutron-rich nuclei; photodistintegration; gravitational potential energy; degenerate Fermi gas; lambda hyperons; the general relativity equation of hydrostatic equilibrium; etc.), before reiterating that he had been offering

"the story of the death of a star as predicted by a combination of nuclear theory, elementary particle theory, and general relativity"
Thorne, 1965, p.1678

So, this was a narrative, but one intended to be fit for a professional scientific audience. It seems the lives and deaths of stars have been part of the technical vocabulary of astronomers for a long time now.

When did scientists imbue stars with life?

Modern astronomy is quite distinct from astrology, but like other sciences astronomy developed from earlier traditions and at one time astronomy and astrology were not so discrete (an astronomical 'star' such as Johannes Kepler was happy to prepare horoscopes for paying customers) and mythological and religious aspects of thinking about the 'heavens' were not so well compartmentalised from what we would today consider as properly the realm of the scientific.

In Egyptian religion, Ra was both a creative force and identified with the sun. Mythology is full of origin stories explaining how the stars had been cast there after various misadventures on earth (the Greek myths but also in other traditions such as those of the indigenous North American and Australian peoples ⁵) and we still refer to examples such as the seven sisters and Orion with the sword hanging in his belt. The planets were associated with different gods – Venus (goddess of love), Mars (the god of war), Mercury (the messenger of the gods), and so on.⁶ It was traditional to refer to some heavenly bodies as gendered: Luna is she, Sol is he, Venus is she, and so on. This usage is sometimes found in scientific writing on astronomy.

Read about examples of personification in scientific writing

Yet this type of poetic license seems unlikely to explain the language of the life cycles of stars, even if there are parallels between scientific and poetic or spiritual accounts,

Stars are celestial objects having their own life cycles. Stars are born, grow up, mature and eventually die. …The author employs inductive and deductive analysis of the verses of the Quran and the Hadith texts related with the life and death of stars. The results show that the life and death of the stars from Islamic and Modern astronomy has some similarities and differences.
Wahab, 2015

After all, the heavenly host of mythology comprised of immortals, if sometimes starting out as mortals subsequently given a kind of immorality by the Gods when being made into stars. Indeed the classical tradition supported by interpretation of Christian orthodoxy was that unlike the mundane things of earth, the heavens were not subject to change and decay – anything from the moon outwards was perfect and unchanging. (This notion was held onto by some long after it was established that comets with their varying paths were not atmospheric phenomena – indeed well into the twentieth century some young earth creationists were still insisting in the perfect, unchanging nature of the heavens. ⁷)

So, presumably, we need to look elsewhere to find how science adopted life cycles for stars.

A natural metaphor?

Earlier in this piece I asked readers to bear with me, and to join with me in making the familiar unfamiliar, to 'bracket' the familiar notion that we say starts are born, live and later die, and to problematise it. In one scientific sense stars cannot die – as they were never alive. Yet, I accept this seems a pretty natural metaphor to use. Or, at least, it seems a natural metaphor to those who are used to hearing and reading it. A science teacher may be familiar with the trope of stars being born, living, and dying – but how might a young learner, new to astronomical ideas, make sense of what was meant?

Now, there is a candidate project for anyone looking for a topic for a student research assignment: how would people who have never previously been exposed to this metaphor respond to the kinds of references I've discussed above? I would genuinely like to know what 'naive' people would make of this ⁸ – would they just 'get' the references immediately (appreciate in what sense stars are born, live, and die); or, would it seem a bizarre way of talking about stars? Given how readily people accept and take up anthropomorphic references to molecules and viruses and electrons and so forth, I find the question intriguing.

Read about anthropomorphism in science

What makes a star alive or dead?

Even if for the disciplinary experts the language of living stars and their life cycles has become a 'dead metaphor 'and is now taken (i.e., taken for granted) as technical terminology – the novice learner, or lay member of the public listening to a radio show, still has to make sense of what it means to say a star is born, or is alive, or is nearing the end of its life, or is dead.

The critical feature discussed by Professors Crawford, Rees and Sullivan concerns an equilibrium that allow a star to exist in a balance between the gravitational attraction of its component matter and the pressure generated through its nuclear reactions.

A star forms when material comes together under its mutual gravitational attraction – and as the material becomes denser it gets hotter. Eventually a sufficient density and temperature is reached such that there is 'ignition' – not in the sense of chemical combustion, but self-sustaining nuclear processes occur, generating heat. This point of ignition is the 'birth' of the star.

Fusion processes continue as long as there is sufficient fissionable material, the 'fuel' that 'feeds' the nuclear 'furnace' (initially hydrogen, but depending on the mass of the star there can be a series of reactions with products from one stage undergoing further fusion to form even heavier elements). The life time of the star is the length of time that such processes continue.

Eventually there will not be sufficient 'fuel' to maintain the level of 'burning' that is needed to allow the ball of material to avoid ('resist') gravitational collapse. There are various specific scenarios, but this is the 'death' of the star. It may be a supernova offering very visible 'death throes'.

The core that is left after this collapse is a 'dead' star, even if it is hot enough to continue being detectable for some time (just as it takes time for the body of a homeothermic animal that dies to cool to the ambient temperature).

It seems then that there is a kind of analogy at work here.

Organisms are alive as long as they continue to metabolise sufficiently in order to maintain their organisation in the face of the entropic tendency towards disintegration and dispersal.

Stars are alive as long as they exhibit sufficient fusion processes to maintain them as balls of material that have much greater volumes, and lower densities than the gravitational forces on their component particles would otherwise lead to.

It is clearly an imperfect analogy.

Organisms base metabolism on a through-put of material to process (and in a sense 'harvest' energy sources).	Stars do acquire new materials and eject some, but this is largely incidental and it is essentially the mass of fissionable material that originally comes together to initiate fusion which is 'harvested' as the energy source.
Organisms may die if they cannot access external food sources, but some die of built-in senescence and others (those that reproduce by dividing) are effectively immortal. We (humans) die because the amazing self-constructing and self-repairing abilities of our bodies are not perfect, and somatic cells cannot divide indefinitely to replace no longer viable cells.	Stars 'die' because they run out of their inherent 'fuel'. Stars die when the hydrogen that came together to form them has substantially been processed.

Read about analogy in science

One person's dead star is another person's living metaphor

So, do stars die? Yes, because astronomers (the experts on stars) say they do, and it seems they are not simply talking down to the rest of us. The birth and death of stars seems to be based on an analogy: an analogy which is implicit in some of the detailed discussion of star life cycles. However, through the habitual use of this analogy, terms such as the birth, lifetimes, and death of stars have been adopted into mainstream astronomical discourse as unmarked (taken-for-granted) language such that to the uninitiated they are experienced as metaphors.

And these perspectival metaphors ⁹ become extended to describe stars that are considered young, old, dying, long dead, and so forth. These terms are used so readily, and so often without a perceived need for qualification or explanation, that we might consider them 'dead' metaphors within astronomical discourse – terms of metaphorical origin but now so habitually used that they have come to be literal (stars are born, they do have lifetimes, they do die). Yet for the uninitiated they are still 'living' metaphors, in the sense that the non-expert needs to work out what it means when a star is said to live or die.

There is a well recognised distinction between live and dead metaphors. But here we have dead-to-the-specialists metaphors that would surely seem to be non-literal to the uninitiated. These terms are not explained by experts as they are taken by them as literal, but they cannot be understood literally by the novice, for whom they are still metaphors requiring interpretation. That is, they are perspectival metaphors – zombie words that may seem alive or dead (as figures of speech) according to audience, and so may be treated as dead in professional discourse, but may need to be made undead when used in communicating to the public.

Other aspects of the In Our Time discussion of 'The death of stars' are explored as The complicated social lives of stars: stealing, escaping, and blowing-off in space

Sources cited:

Strömberg, G. (1927). The Motions of Giant M Stars. The Astrophysical Journal, 65, 238.
Thorne, K. S. (1965). Gravitational Collapse and the Death of a Star. Science, 150(3704), 1671-1679. http://www.jstor.org.ezp.lib.cam.ac.uk/stable/1717408
Wahab, R. A. (2015). Life and death of stars: an analysis from Islamic and modern astronomy perspectives. International Proceedings of Economics Development and Research, 83, 89.

Notes

¹ In this regard, but not in all regards. As I have suggested here before, the teacher usually has two advantages:

a) generally, a class has a limited spread in terms of the audience background: even a mixed ability class is usually from a single school year (grade level) whereas the public presentation may be addressing a mixed audience of all ages and levels of education.

b) usually a teacher knows the class, and so knows something about their starting points, and their interests

² Some students do well in science tests and others less well.

If we say this is because

some learners are better science students than others
and settle for defining better science students as those who achieve good results in formal science tests (that is tests as currently administered, based on the present curriculum, taught in our usual way)

then we are simply 'explaining' the explicandum (i.e., some students do better on science tests that others) by a rephrasing of what is to be explained (some students are better science students: that is, they perform well in science tests!)

Read about tautology

³ Criterion (singular) as a living organism has to satisfy the entries in the list collectively. Each entry is of itself a necessary, but not sufficient, condition.

⁴ A simple misunderstanding is that animals respire but plants photosynthesise.

In a plant in a steady state, the rates of build-up and break down of sugars would be balanced. However, plants must photosynthesise more than they respire overall in order to to grow and ultimately to allow consumers to make use of them as food. (This needs to be seen at a system level – the plant is clearly not in any inherent sense photosynthesising to provide food for other organisms, but has evolved to be a suitable nutrition source as it transpires [no pun intended] that increases the fitness of plants within the wider ecosystem.)

A more subtle alternative conception is that plants photosynthesise during the day when they are illuminated by sunlight (fair enough) and then use the sugar produced to respire at night when the sun is not available as a source of energy. See, for example, 'Plants mainly respire at night because they are photosynthesising during the day'.

Actually cellular processes require continuous respiration (as even in the daytime sunlight cannot directly power cellular metabolism, only facilitate photosynthesis to produce the glucose that that can be oxidised in respiration).

Schematic reflection of the balance between how photosynthesis generates resources to allow respiration – typically a plant produces tissues that feed other organisms.
The area above the line represents energy from sunlight doing work in synthesising more complex substances. The area below the lines represents work done when the oxidation of those more complex substances provides the energy source for building and maintaining an organism's complex organisation of structure and processes (homoestasis).

⁵ Museum Victoria offers a pdf that can be downloaded and copied by teachers to teach about how "How the southern night sky is seen by the Boorong clan from north-west Victoria":

'Stories in the Stars – the night sky of the Boorong people' shows the constellations as recognised by this group, the names they were given, and the stories of the people and creatures represented.

(This is largely based on the nineteenth century reports made by William Edward Stanbridge of information given by Boorong informants – see 'Was the stellar burp really a sneeze?')

The illustration shown here is of 'Kulkunbulla' – a constellation that is considered in the U.K. to be only part of the constellation known here as Orion. (Constellations are not actual star groupings, but only what observers have perceived as stars seeming to be grouped together in the sky – the Boorong's mooting of constellations is no more right or wrong than that suggested in any other culture.)

⁶ The tradition was continued into modern times with the discovery of the planets that came to be named Neptune and Uranus after the Gods of the sea and sky respectively.

⁷ Creationism, per se, is simply the perspective or belief that the world (i.e., Universe) was created by some creator (God) and so creationism as such is not necessarily in conflict with scientific accounts. The theory of the big bang posits that time, space and matter had a beginning with an uncertain cause which could be seen as God (although some theorists such as Professor Roger Penrose develop theories which posit a sequence of universes that each give rise to the next and that could have infinite extent).

Read about science and religion

Young earth creationists, however, not only believe in a creator God (i.e., they are creationists), but one who created the World no more than about 10 thousand years ago (the earth is young!), rather than over 13 billion years ago. This is clearly highly inconsistent with a wide range of scientific findings and thinking. If the Young Earth Creationists are right, then either

a lot of very strongly evidenced science is very, very wrong
some natural laws (e.g. radioactive decay rates) that now seem fixed must have changed very substantially since the creation
the creator God went to a lot of trouble to set up the natural world to present a highly misleading account of its past history

⁸ I am not using the term naive here in a discourteous or demeaning way, but in a technical sense of someone who is meeting something for the first time.

⁹ That is, terms that will appear as metaphors from the perspective of the uninitiated, but now seem literal terms from the perspective of the specialist. We cannot simply say they are or are not metaphors, without asking 'for whom?'

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