Category: science communication

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.

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"

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.

WordFrequency in Nature article
clump(s)25 (excluding reference list)
eject(ed, etc.)4
veil1 (in title only)
burp0
blob0
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

Cells are buzzing cities that are balloons with harpoons

What can either wander door to door, or rush to respond; and when it arrives might touch, sniff, nip, rear up, stroke, seal, or kill?

Keith S. Taber

a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts

BBC Radio 4's 'Start the week' programme is not a science programme, but tends to invite in guests (often authors of some kind) each week according to some common theme. This week there was a science theme and the episode was titled 'Building the Body, Opening the Heart', and was fascinating. It also offers something of a case study in how science gets communicated in the media.

Building the Body, Opening the Heart

The guests all had life-science backgrounds:

Their host was geneticist and broadcaster Adam Rutherford.

Communicating science through the media

As a science educator I listen to science programmes both to enhance and update my own science knowledge and understanding, but also to hear how experts present scientific ideas when communicating to a general audience. Although neither science popularisation nor the work of scientists in communicating to the public is entirely the same as formal teaching (for example,

  • there is no curriculum with specified target knowledge; and
  • the audiences
    • are not well-defined,
    • are usually much more diverse than found in classrooms, and
    • are free to leave at any point they lose interest or get a better offer),

they are, like teachers, seeking to inform and explain science.

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.

Perhaps one of the the biggest differences between science teaching and science communication in the media is the ultimate criterion of success. For science teachers this is (sadly) usually, primarily at least, whether students have understood the material, and will later recall it, sufficiently to demonstrate target knowledge in exams. The teacher may prefer to focus on whether students enjoy science, or develop good attitudes to science, or will consider working in science: but, even so, they are usually held to account for students' performance levels in high-stakes tests.

Science journalists and popularisers do not need to worry about that. Rather, they have to be sufficiently engaging for the audience to feel they are learning something of interest and understanding it. Of course, teachers certainly need to be engaging as well, but they cannot compromise what is taught, and how it is understood, in order to entertain.

With that in mind, I was fascinated at the range of ways the panel of guests communicated the science in this radio show. Much of the programme had a focus on cells – and these were described in a variety of ways.

Talking about cells

Dr Rutherford introduced cells as

  • "the basic building blocks of life on earth"; and observed that he had
  • "spent much of my life staring down microscopes at these funny, sort of mundane, unremarkable, gloopy balloons"; before suggesting that cells were
  • "actually really these incredible cities buzzing with activity".

Dr. Mukherjee noted that

"they're fantastical living machines" [where a cell is the] "smallest unit of life…and these units were built, as it were, part upon part like you would build a Lego kit"

Listeners were told how Robert Hooke named 'cells' after observing cork under the microscope because the material looked like a series of small rooms (like the cells where monks slept in monasteries). Hooke (1665) reported,

"I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen as a Razor, I cut a piece of it off, and…cut off from the former smooth surface an exceeding thin piece of it, and…I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars

…these pores, or cells, were not very deep, but consisted of a great many little Boxes, separated out of one continued long pore, by certain Diaphragms, as is visible by the Figure B, which represents a sight of those pores split the long-ways.

Robert Hooke
Hooke's drawing of the 'pores' or 'cells' in cork

Components of cells

Dr. Mukherjee described how

"In my book I sort of board the cell as though it's a spacecraft, you will see that it's in fact organised into rooms and there are byways and channels and of course all of these organelles which allow it to work."

We were told that "the cell has its own skeleton", and that the organelles included the mitochondria and nuclei ,

"[mitochondria] are the energy producing organelles, they make energy in most cells, our cells for instance, in human cells. In human cells there's a nucleus, which stores DNA, which is where all the genetic information is stored."

A cell that secretes antibodies which are like harpoons or missiles that it sends out to kill a pathogen?

(Images by by envandrare and OpenClipart-Vectors from Pixabay)

Immune cells

Rutherford moved the conversation onto the immune system, prompting 'Sid' that "There's a lovely phrase you use to describe T cells, which is door to door wanderers that can detect even the whiff of an invader". Dr. Mukherjee distinguished between the cells of the innate immune system,

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

and the cells of the adaptive system, such as B cells and T cells,

"The B cell is a cell that eventually becomes a plasma cell which secretes antibodies. Antibodies, they are like harpoons or missiles which the cell sends out to kill a pathogen…

[A T cell] goes around sniffing other cells, basically touching them and trying to find out whether they have been altered in some way, particularly if they are carrying inside them a virus or any other kind of pathogen, and if it finds this pathogen or a virus in your body, it is going to go and kill that virus or pathogen"

A cell that goes around sniffing other cells, touching them? 1
(Images by allinonemovie and OpenClipart-Vectors from Pixabay)

Cells of the heart

Another topic was the work of Professor Harding on the heart. She informed listeners that heart cells did not get replaced very quickly, so that typically when a person dies half of their heart cells had been there since birth! (That was something I had not realised. It is believed that this is related to how heart cells need to pulse in synchrony so that the whole organ functions as an effective pumping device – making long lasting cells that seldom need replacing more important than in many other tissues.)

At least, this relates to the cardiomyocytes – the cells that pulse when the heart beats (a pulse that can now be observed in single cells in vitro). Professor Harding described how in the heart tissue there are also other 'supporting' cells, such as "resident macrophages" (immune cells) as well as other cells moving around the cardiomyocytes. She describe her observations of the cells in Petri dishes,

"When you look at them in the dish it's incredible to see them interact. I've got a… video [of] cardiomyocytes in a dish. The cardiomyocytes pretty much just stay there and beat and don't do anything very much, and I had this on time lapse, and you could see cells moving around them. And so, in one case, the cell (I think it was a fibroblast, it looked like a fibroblast), it came and it palpated at the cardiomyocyte, and it nipped off bits of it, it sampled bits of the cardiomyocyte, and it just stroked it all the way round, and then it was, it seemed to like it a lot.

[In] another dish I had the same sort of cardiomyocyte, a very similar cell came in, it went up to the cardiomyocyte, it touched it, and as soon as it touched it, I can only describe it as it reared up and it had, little blobs appeared all over its surface, and it rushed off, literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off, so what had it found, why did one like it and the other one didn't?"

Making the unfamiliar, familiar

The snippets from the broadcast that I have reported above demonstrate a wide range of ways that the unfamiliar is made familiar by describing it in terms that a listener can relate to through their existing prior knowledge and experience. In these various examples the listener is left to carry across from the analogue features of the familiar (the city, the Lego bricks, human interactions, etc.) those that parallel features of the target concept – the cell. So, for example, the listener is assumed to appreciate that cells, unlike Lego bricks, are not built up through rigid, raised lumps that fit precisely in depressions on the next brick/cell. 2

Analogies with the familiar

Hooke's original label of the cell was based on a kind of analogy – an attempt to compare what we has seeing with something familiar: "pores, or cells…a great many little Boxes". He used the familiar simile of the honeycomb (something directly familiar to many more people in the seventeenth century when food was not subject to large-scale industrialised processing and packaging).

Other analogies, metaphors and similes abound. Cells are visually like "gloopy balloons", but functionally are "building blocks" (strictly a metaphor, albeit one that is used so often it has become treated as though a literal description) which can be conceptualised as being put together "like you would build a Lego kit" (a simile) although they are neither fixed, discrete blocks of a single material, nor organised by some external builder. They can be considered conceptually as the"smallest unit of life"(though philosophers argue about such descriptions and what counts as an individual in living systems).

The machine description ("fantastical living machines") reflects one metaphor very common in early modern science and cells as "incredible cities" is also a metaphor. Whether cells are literally machines is a matter of how we extend or limit our definition of machines: cells are certainly not actually cities, however, and calling them such is a way of drawing attention to the level of activity within each (often, apparently from observation, quite static) cell. B cells secrete antibodies, which the listener is old are like (a simile) harpoons or missiles – weapons.

Skeletons of the dead

Whether "the cell has its own skeleton" is a literal or metaphorical statement is arguable. It surely would have originally been a metaphoric description – there are structures in the cell which can be considered analogous to the skeleton of an organism. If such a metaphor is used widely enough, in time the term's scope expands to include its new use – and it becomes (what is called, metaphorically) a 'dead metaphor'.

Telling stories about cells

A narrative is used to help a listener imagine the cell at the scale of "a spacecraft". This is "organised into rooms and there are byways and channels" offering an analogy for the complex internal structure of a cell. Most people have never actually boarded a spacecraft, but they are ubiquitous in television and movie fiction, so a listener can certainly imagine what this might be like.

Endoplastic reticulum? (Still from Star Trek: The Motion Picture, Paramount Pictures, 1979)
Oversimplification?

The discussion of organelles illustrates how simplifications have to be made when introducing complex material. This always brings with it dangers of oversimplification that may impede further learning, or even encourage the development of alternative conceptions. So, the nucleus does not, strictly, 'store' "all the genetic information" in a cell (mitochondria carry their own genes for example).

More seriously, perhaps, mitochondria do not "make energy". 'More seriously' as the principle of conservation of energy is one of the most basic tenets of modern science and is considered a very strong candidate for a universal law. Children are often taught in school that energy cannot be created or destroyed. Science communication which is contrary to this basic curriculum science could confuse learners – or indeed members of the public seeking to understand debates about energy policy and sustainability.

Anthropomorphising cells

Cells are not only compared to inanimate entities like balloons, building bricks, cities and spaceships. They are also described in ways that make them seem like sentient agents – agents that have experiences, and conscious intentions, just as people do. So, some immune cells are metaphorical 'first responders' and just as emergency services workers they "rush to the site" of an incident. To rush is not just to move quickly, buy to deliberately do so. (By contrast, Paul McAuley refers to "innocent" amoeboid cells that collectively form into the plasmodium of a slime mould spending most of their lives"bumbling around by themselves" before they "get together". ) The immune cells act deliberately – they "try" to kill. Other immune cells "send out" metaphorical 'missiles' "to kill a pathogen". Again this language suggests deliberate action (i.e., to send out) and purpose.

That is, what is described is not just some evolved process, but something teleological: there is a purpose to sending out antibodies – it is a deliberate act with an aim in mind. This type of language is very common in biology – even referring to the 'function' of the heart or kidney or a reflex arc could be considered as misinterpreting the outcome of evolutionary developments. (The heart pumps blood through the vascular system, but referring to a function could suggest some sense of deliberate design.)

Not all cells are equal

I wonder how many readers noticed the reference above to 'supporting' cells in the heart. Professor Harding had said

"When you look inside the [heart] tissue there are many other cells [than cardiomyocytes] that are in there, supporting it, there are resident macrophages, I think we still don't know really what they are doing in there"

Why should some heart cells be seen as more important and others less so? Presumably because 'the function' of a heart is to beat, to pump, so clearly the cells that pulse are the stars, and the other cells that may be necessary but are not obviously pulsing just a supporting cast. (So, cardiomyocytes are considered heart cells, but macrophages in the same tissue are only cells that are found in the heart, "residents" – to use an analogy of my own, like migrants that have not been offered citizenship!)3

That is, there is a danger here that this way of thinking could bias research foci leading researchers to ignore something that may ultimately prove important. This is not fanciful, as it has happened before, in the case of the brain:

"Glial cells, consisting of microglia, astrocytes, and oligodendrocyte lineage cells as their major components, constitute a large fraction of the mammalian brain. Originally considered as purely non-functional glue for neurons, decades of research have highlighted the importance as well as further functions of glial cells."

Jäkel and Dimou, 2017
The lives of cells

Narrative is used again in relation to the immune cells: an infection is presented as a kind of emergency event which is addressed by special (human like) workers who protect the body by repelling or neutralising invaders. "Sniffing" is surely an anthropomorphic metaphor, as cells do not actually sniff (they may detect diffusing substances, but do not actively inhale them). Even "touching" is surely an anthropomorphism. When we say two objects are 'touching' we mean they are in contact, as we touch things by contact. But touching is sensing, not simply adjacency.

If that seems to be stretching my argument too far, to refer to immune cells "trying to find out…" is to use language suggesting an epistemic agent that can not only behave deliberately, but which is able to acquire knowledge. A cell can only "find" an infectious agent if it is (i.e., deliberately) looking for something. These metaphors are very effective in building up a narrative for the listener. Such a narrative adopts familiar 'schemata', recognisable patterns – the listener is aware of emergency workers speeding to the scene of an incident and trying to put out a fire or seeking to diagnose a medical issue. By fitting new information into a pattern that is familiar to the audience, technical and abstract ideas are not only made easier to understand, but more likely to be recalled later.

Again, an anthropomorphic narrative is used to describe interactions between heart cells. So, a fibroblast that "palpates at" a cardiomyocyte seems to be displaying deliberate behaviour: if "nipping" might be heard as some kind of automatic action – "sampling" and "stroking" surely seem to be deliberate behaviour. A cell that "came in, it went up [to another]" seems to be acting deliberately. "Rearing up" certainly brings to mind a sentient being, like a dog or a horse. Did the cell actually 'rear up'? It clearly gave that impression to Professor Harding – that was the best way, indeed the "only" way, she had to communicate what she saw.

Again we have cells "rushing" around. Or do we? The cell that had reared up, "rushed off". Actually, it appeared to "rush" when the highly magnified footage was played at 720 times the speed of the actual events. Despite acknowledging this extreme acceleration of the activity, the impression was so strong that Professor Harding felt justified in claiming the cell "literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off…". Whatever it did, that looked like rushing with the distortion of time-lapse viewing, it certainly did not literally rush anywhere.

But the narrative helps motivate a very interesting question, which is why the two superficially similar cells 'behaved' ('reacted', 'responded' – it is actually difficult to find completely neutral language) so differently when in contact with a cardiomyocyte. In more anthropomorphic terms: what had these cells "found, why did one like it and the other one didn't?"

Literally speaking?

Metaphorical language is ubiquitous as we have to build all our abstract ideas (and science has plenty of those) in terms of what we can experience and make sense of. This is an iterative process. We start with what is immediately available in experience, extend metaphorically to form new concepts, and in time, once those have "settled in" and "taken root" and "firmed up" (so to speak!) they can then be themselves borrowed as the foundation for new concepts. This is true both in how the individual learns (according to constructivism) and how humanity has developed culture and extended language.

So, should science communicators (whether scientists themselves, journalists or teachers) try to limit themselves to literal language?

Even if this were possible, it would put aside some of our strongest tools for 'making the unfamiliar familiar' (to broadcast audiences, to the public, to learners in formal education). However these devices also bring risks that the initial presentations (with their simplifications and metaphors and analogies and anthropomorphic narratives…) not only engage listeners but can also come to be understood as the scientific account. That is is not an imagined risk is shown by the vast numbers of learners who think atoms want to fill their shells with octets of electrons, and so act accordingly – and think this because they believe it is what they have been taught.

Does it matter if listeners think the simplification, the analogy, the metaphor, the humanising story,… is the scientific account? Perhaps usually not in the case of the audience listening to a radio show or watching a documentary out of interest.

In education it does matter, as often learners are often expected to progress beyond these introductory accounts in their thinking, and teachers' models and metaphors and stories are only meant as a starting point in building up a formal understanding. The teacher has to first establish some kind of anchor point in the students' existing understandings and experiences, but then mould this towards the target knowledge set out in the curriculum (which is often a simplified account of canonical knowledge) before the metaphor or image or story becomes firmed-up in the learners' minds as 'the' scientific account.

'Building the Body, Opening the Heart' was a good listen, and a very informative and entertaining episode that covered a lot of ideas. It certainly included some good comparisons that science teachers might borrow. But I think in a formal educational context a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts.

Read about science analogies

Read about science metaphors

Read about science similes

Read about anthropomorphism

Read about teleology

Work cited:

Notes:

1 The right hand image portrays a mine, a weapon that is used at sea to damage and destroy (surface or submarine) boats. The mine is also triggered by contact ('touch').

2 That is, in an analogy there are positive and negative aspects: there are ways in which the analogue IS like the target, and ways in which the analogue is NOT like the target. Using an analogy in communication relies on the right features being mapped from the familiar analogue to the unfamiliar target being introduced. In teaching it is important to be explicit about this, or inappropriate transfers may be made: e.g., the atom is a tiny solar system so it is held together by gravity (Taber, 2013).

3 It may be a pure coincidence in relation to the choice of term 'resident' here, but in medicine 'residents' have not yet fully qualified as specialist physicians or surgeons, and so are on placement and/or under supervision, rather than having permanent status in a hospital faculty.

The missing mass of the electron

Annihilating mass in communicating science

Keith S. Taber

An episode of 'In Our Time' about the electron

The BBC radio programme 'In Our Time' today tackled the electron. As part of the exploration there was the introduction of the positron, and the notion of matter-antimatter annihilation. These are quite brave topics to introduce in a programme with a diverse general audience (last week Melvyn Bragg and his guests discussed Plato's Atlantis and next week the programme theme is the Knights Templar).

Prof. Victoria Martin of the School of Physics and Astronomy at the University of Edinburgh explained:

If we take a pair of matter and antimatter, so, since we are talking about the electron today, if we take an electron and the positron, and you put them together, they would annihilate.

And they would annihilate not into nothingness, because they both had mass, so they both had energy from E=mc2 that tells us if you have mass you have energy. So, they would annihilate into energy, but it would not just be any kind of energy: the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light. And it will have a very specific amount of energy. Its energy will be equal to the sum of the energy of electron and the positron that they had initially when they collided together.

Prof. Victoria Martin on 'In Our Time'
"An electron and the positron, and you put them together, they would annihilate…they would annihilate into energy" – but this could be misleading.

Now, I am sure that is somewhat different from how Prof. Martin would treat this topic with university physics students – of course, science in the media has to be pitched at the largely non-specialist audience.

Read about science in the media

It struck me that this presentation had the potential to reinforce a common alternative conception ('misconception') that mass is converted into energy in certain processes. Although I am aware now that this is an alternative conception, I seem to recall that is pretty much what I had once understood from things I had read and heard.

It was only when I came to prepare to teach the topic that I realised that I had a misunderstanding. That, I think, is quite common for teachers – when we have to prepare a topic well enough to explain it to others, we may spot flaws in our own understanding (Taber, 2009)

So, for example, I had thought that in nuclear processes, such as in a fission reactor or fusion in stars, the mass defect (the apparent loss of mass as the resulting nuclear fragments have less mass than those present before the process) was due to that amount of mass being converted to energy. This is sometimes said to explain why nuclear explosions are so much more violent than chemical explosions, as (given E=mc2): a tiny amount of mass can be changed into a great deal of energy.

Prof. Martin's explanation seemed to support this way of thinking: "they would annihilate into energy".

An alternative conception of particle annihilation: This scheme seems to be implied by Prof. Martin's comments

What is conserved?

It is sometimes suggested that, classically, mass and energy were considered to be separately conserved in processes, but since Einstein's theories of relativity have been adopted, now it is considered that mass can be considered as if a form of energy such that what is conserved is a kind of hybrid conglomerate. That is, energy is still considered conserved, but only when we account for mass that may have been inter-converted with energy. (Please note, this is not quite right – see below.)

So, according to this (mis)conception: in the case of an electron-positron annihilation, the mass of the two particles is converted to an equivalent energy – the mass of the electron and the mass of the positron disappear from the universe and an equivalent quantity of energy is created. Although energy is created, energy is still conserved if we allow for the mass that was converted into this new energy. Each time an electron and positron annihilate, their masses of about 2 ✕ 10-30 kg disappear from the universe and in its place something like 2 ✕ 10-13 J appears instead – but that's okay as we can consider 2 ✕ 10-30 kg as a potential form of energy worth 2 ✕ 10-13 J.

However, this is contrary to what Einstein (1917/2004) actually suggested.

Einstein did not suggest that matter could be changed to energy

Equivalence, not interconversion

What Einstein actually suggested was not that mass could be considered as if another kind/form of energy (alongside kinetic energy and gravitational potential, etc.) that needed to be taken into account in considering energy conservation, but rather that inertial mass can be considered as an (independent) measure of energy.

That is, we think energy is always conserved. And we think that mass is always conserved. And in a sense they are two measures of the same thing. We might see these two statements as having redundancy:

  • In a isolated system we will always have the same total quantity of energy before and after any process.
  • In a isolated system we will always have the same total quantity of mass before and after any process.

As mass is always associated with energy, and so vice versa, either of these statements implies the other. 1

Two conceptions of the shift from a Newtonian to a relativistic view of the conservation of energy (move the slider to change the image)
No interconversion?

So, mass cannot be changed into energy, nor vice versa. The sense in which we can 'interconvert' is that we can always calculate the energy equivalence of a certain mass (E=mc2) or mass equivalence of some quantity of energy (m=E/c2).

So, the 'interconversion' is more like a change of units than a change of entity.

Although we might think of kinetic energy being converted to potential energy reflects a natural process (something changes), we know that changing joules to electron-volts is merely use of a different unit (nothing changes).

If we think of a simple pendulum under ideal conditions 2 it could oscillate for ever, with the total energy unchanged, but with the kinetic energy being converted to potential energy – which is then converted back to kinetic energy – and so on, ad infinitum. The total energy would be fixed although the amount of kinetic energy and the amount of potential energy would be constantly changing. We could calculate the energy in joules or some other unit such as eV or ergs (or calories or kWh or…). We could convert from one unit to another, but this would not change anything about the physical system. (So, this is less like converting pounds to dollars, and more like converting an amount reported in pounds {e.g., £24.83} into an amount reported in pence {e.g., 2483p}.)

Using this analogy, the electron and positron being converted to a photon is somewhat like kinetic energy changing to potential energy in a swinging pendulum (something changes), but it is not the case that mass is changed into energy. Rather we can do our calculations in terms of energy or mass and will get (effectively, given E=mc2) the same answer (just as we can add up a shopping list in pounds or pence, and get the same outcome given the conversion factor, 1.00£ = 100p).

So, where does the mass go?

If mass is conserved, then where does the mass defect – the amount by which the sum of masses of daughter particles is less than the mass of the parent particle(s) – in nuclear processes go? And, more pertinent to the present example, what happens to the mass of the electron and positron when they mutually annihilate?

To understand this, it might help to bear in mind that in principle these process are like any other natural processes – such as the swinging pendulum, or a weight being lifted with pulley, or methane being combusted in a Bunsen burner, or heating water in a kettle, or photosynthesis, or a braking cycle coming to a halt with the aid of friction.

In any natural process (we currently believe)

  • the total mass of the universe is unchanged…
    • but mass may be reconfigured
  • the total energy of the universe is unchanged…
    • but energy may be reconfigured; and
  • as mass and energy are associated, any reconfigurations of mass and energy are directly correlated.

So, in any change that involves energy transfers, there is an associated mass transfer (albeit usually one too small to notice or easily measure). We can, for example, calculate the (tiny) increase in mass due to water being heated in a kettle – and know just as the energy involved in heating the water came from somewhere else, there is an equivalent (tiny) decrease of mass somewhere else in the wider system (perhaps due to falling of water powering a hydroelectric power station). If we are boiling water to make a cup of tea, we may well be talking about a change in mass of the order of only 0.000 000 001 g according to my calculations for another posting.

Read 'How much damage can eight neutrons do? Scientific literacy and desk accessories in science fiction.'

The annihilation of the electron and positron is no different: there may be reconfigurations in the arrangement of mass and energy in the universe, but mass (and so energy) is conserved.

So, the question is, if the electron and positron, both massive particles (in the physics sense, that they have some mass) are annihilated, then where does their mass go if it is conserved? The answer is reflected in Prof. Martin's statement that "the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light". The mass is carried away by the photon.

The mass of a massless particle?

This may seem odd to those who have learnt that, unlike the electron and positron, the photon is massless. Strictly the photon has no rest mass, whereas the electron and positron do have rest mass – that is, they have inertial mass even when judged by an observer at rest in relation to them.

So, the photon only has 'no mass' when it is observed to be stationary – which nicely brings us back to Einstein who noted that electromagnetic radiation such as light could never appear to be at rest compared to the observer, as its very nature as a progressive electromagnetic wave would cease if one could travel alongside it at the same velocity. This led Einstein to conclude that the speed of light in any given medium was invariant (always the same for any observer), leading to his theory of special relativity.

So, a photon (despite having no 'rest' mass) not only carries energy, but also the associated mass.

Although we might think in terms of two particles being converted to a certain amount of energy as Prof. Martin suggests, this is slightly distorted thinking: the particles are converted to a different particle which now 'has' the mass from both, and so will also 'have' the energy associated with that amount of mass.

Mass is conserved during the electron-positron annihilation

A slight complication is that the electron and position are in relative motion when they annihilate, so there is some kinetic energy involved as well as the energy associated with their rest masses. But this does not change the logic of the general scheme. Just as there is an energy associated with the particles' rest masses, there is a mass component associated with their kinetic energy.

The total mass-energy equivalence before the annihilation has to include both the particle rest masses and their kinetic energy. The mass-energy equivalence afterwards (being conserved in any process) also reflects this. The energy of the photon (and the frequency of the radiation) reflects both the particle masses and their kinetic energies at the moment of the annihilation. The mass (being perfectly correlated with energy) carried away by the photon also reflects both the particle masses and their kinetic energies.

How could 'In Our Time' have improved the presentation?

It is easy to be critical of people doing their best to simplify complex topics. Any teacher knows that well-planned explanations can fail to get across key ideas as one is always reliant on what the audience already understands and thinks. Learners interpret what they hear and read in terms of their current 'interpretive resources' and habits of thinking.

Read about constructivism

A physicist or physics student hearing the episode would likely interpret Prof. Martin's statement within a canonical conceptual framework. However, someone holding the 'misconception' that mass is converted to energy in nuclear processes would likely interpret "they would annihilate into energy" as fitting, and reinforcing, that alternative conception.

I think a key issue here is a slippage that apparently refers to energy being formed in the annihilation, rather than radiation: (i.e., Prof. Martin could have said "they would annihilate into [radiation]"). When the positron and electron 'become' a photon, matter is changed to radiation – but it is not changed to energy, as matter has mass, and (as mass and energy have an equivalence) the energy is already there in the system.

Energy is reconfigured, but is not formed, in the annihilation process.

So, this whole essay is simply suggesting that a change of one word – from energy to radiation – could potentially avoid the formation of, or the reinforcing of, the alternative conception that mass is changed into energy in processes studied in particle physics. As experienced science teachers will know, sometimes such small shifts can make a good deal of difference to how we are interpreted and, so, what comes to be understood.

Addenda:

Reply from Prof. Victoria Martin on twitter (@MamaPhysikerin), September 30:

"E2 = p2c2 + m2c4 is a better way to relate energy, mass and momentum. Works for both massive and massless states."

@MamaPhysikerin
Work cited:

Notes

1 In what is often called a closed system there is no mass entering or leaving the system. However, energy can transfer to, or from, the system from its surroundings. Classically it might be assumed that the mass of a closed system is constant as the amount of matter is fixed, but Einstein realised that if there is a net energy influx to, or outflow from, the system, than some mass would also be transferred – even though no matter enters or leaves.

2 Perhaps in a uniform gravitational field, not subject to to any frictional forces, with an inextensible string supporting the bob, and in thermal equilibrium with its environment.

Are these fossils dead, yet?

Non-living fossils and dead metaphors

Keith S. Taber

Fossil pottery?
(Images by by Laurent Arroues {background}) and OpenClipart-Vectors from Pixabay)

I was intrigued by some dialogue that was part of one of (physicist) Jim Al-Khalili's interviews for the BBC's 'The Life Scientific' series, where Prof. Al-Khalili "talks to leading scientists about their work, finding out what inspires and motivates them and asking what their discoveries might do for mankind".

The Life Scientific – interviews with scientists about their lives and work

This week he was talking to Dr Judith Bunbury of St. Edmund's College and the Department of Earth Sciences at Cambridge ('Judith Bunbury on the shifting River Nile in the time of the Pharaohs'). It was a fascinating interview, and in particular discussed work showing how the Nile River has repeatedly changed its course over thousands of years. The Nile is considered the longest river in Africa (and possibly the world – the other contender being the Amazon).

Over time the river shifts is position as it unevenly lay down sediment and erodes the river banks – (Image by Makalu from Pixabay)

The exchange that especially piqued my interest followed an account of the diverse material recovered in studies that sample the sediments formed by the river. As sediments are laid down over time, a core (collected by an auger) can be understood to have formed on a time-line – with the oldest material at the bottom of the sample.

Within the sediment, researchers find fragments of animal bone, human teeth, pottery, mineral shards from the working of jewels…

"Are you sure the Nile flows this far?" Using an auger to collect a core (of ice in this case) (Image by David Mark from Pixabay)

Dr Bunbury was taking about how changing fashions allowed the pottery fragments to be useful in dating material – or as the episode webpage glossed this: "pottery fragments which can be reliably time-stamped to the fashion-conscious consumers in the reign of individual Pharaohs".

This is my transcription of the exchange:

[JAK]: …a bit like fossil hunting
[JB]: well, I mean, we're just treating pottery as a kind of fossil
a kind of fossil, yeah, > no, absolutely >
< and it is a fossil <
yes, well quite, I can see the similarities.

Prof. Jim Al-Khalili interviewing Dr Judith Bunbury

Now Prof. Jim has a very gentle, conversational, interview style, as befits a programme with extended interviews with scientists talking about their lives (unlike, say, a journalist faced with a politician where a more adversarial style might be needed), so this exchange probably comes as close to a disagreement or challenge as 'The Life Scientific' gets. Taking a slight liberty, I might represent this as:

  • Al-Khalili: your work is like fossil hunting, the pottery fragments are similar to fossils
  • Bunbury: no, they ARE fossils

So, here we have an ontological question: are the pottery fragments recovered in archaeological digs (actually) fossils or not?

Bunbury wants to class the finds as fossils.

Al-Khalili thinks that in this context 'a kind of fossil' and 'like fossil hunting' are similes ("I can see the similarities") – the finds are somewhat like fossils, but are not fossils per se.

Read about science similes

So, who is right?

Metaphorical fossils

The term fossil is commonly used in metaphorical ways. For example, for a person to be described as a fossil is to be characterised as a kind of anachronism that has not kept up with social changes.

The term also seems to have been adopted in some areas of science as a kind of adjective. One place it is used is in relation to evidence of dampened ocean turbulence,

"The term 'fossil turbulence' refers to remnants of turbulence in fluid which is no longer turbulent."

Gibson, 1980, p.221

If that seems like a contradiction, it is explained that

"Small scale fluctuations of temperature, salinity, and vorticity in the ocean occur in isolated patches apparently caused by bursts of active turbulence. After the turbulence has been dampened by stable stratification the fluctuations persist as fossil turbulence."

Gibson, 1980, p.221

So, 'fossil turbulence' is not actually turbulence, but more the afterglow of the turbulence: a bit like the aftermath of a lively party which leaves its traces: the the chaotic pattern of abandoned debris provides signs there has been a party although there is clearly no longer a party going on.

An analogy for 'fossil turbulence'

Another example from astronomy is fossil groups of galaxies, which are apparently "systems with a very luminous X-ray source …and a very optically dominant central galaxy" (Kanagusuku, Díaz-Giménez & Zandivarez, 2016). It seems,

"The true nature of fossil groups in the Universe still puzzles the astronomical community. These peculiar systems are one of the most intriguing places in the Universe where giant elliptical galaxies are hosted [sic]."

Kanagusuku, Díaz-Giménez & Zandivarez, 2016

('Hosted' here also seems metaphorical – who or what could be acting as a host to an elliptical galaxy?)

The term 'fossil group' was introduced for "for an apparently isolated elliptical galaxy surrounded by an X-ray halo, with an X-ray luminosity typical of a group of galaxies" (Zarattini, Biviano, Aguerri, Girardi & D'Onghia, 2012): so, something that looks like a single galaxy, but in other respsects resembles a whole group of galaxies?

Close examination might reveal other galaxies present, yet the 'fossil' group is "distinguished by a large gap between the brightest galaxy and the fainter members" (Dariush, Khosroshahi, Ponman, Pearce, Raychaudhury & Hartley, 2007). Of course, there is normally a 'large gap' between any two galaxies (space contains a lot of, well, space), but presumably this is another metaphor – there is a 'gap' between the magnitude of the luminosity of the brightest galaxy, and the magnitudes of the luminosities of the others.

Read about science metaphors

Dead metaphors

One way in which language changes over time is through the (metaphorical) death of metaphors. Terms that are initially introduced as metaphors sometimes get generally adopted and over time become accepted terminology.

Many words in current use today were originally coined in this way, and often people are quite unaware of their origins. References to the hands of a clock or watch will these days be taken as simply a technical term (or perhaps for those who only familiar with digital clocks, a complete mystery?) In time, this may happen to 'fossil turbulence' or 'fossil galaxy groups'.

What counts as a fossil?

But it seems reasonable to suggest that, currently at least, these are still metaphors, implying that in some sense the ocean fluctuations or the galactic groups are somewhat like fossils. But these are not actual fossils, just as tin-pot dictators are not actually fabricated from tin.

So, what are actual fossils. The 'classic' fossil takes the form of an ancient, often extinct, living organism, or a part thereof, but composed of rock which has over time replaced the original organic material. In this sense, Prof. Al-Khalili seems correct in suggesting bits of pottery are only akin to fossils, and not actually fossils. But is that how the experts use the term?

According to the British Geological Survey (BGS):

Fossils are the preserved remains of plants and animals whose bodies were buried in sediments, such as sand and mud, under ancient seas, lakes and rivers. Fossils also include any preserved trace of life that is typically more than 10 000 years old. 

https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/fossils/ 1

Now, pottery is not the preserved remains of plants or animals or other living organisms, but the site goes on to explain,

Preserved evidence of the body parts of ancient animals, plants and other life forms are called 'body fossils'. 'Trace fossils' are the evidence left by organisms in sediment, such as footprints, burrows and plant roots.

https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/fossils 1

So, footprints, burrows, [evidence of] plant roots 2…or shards of pottery…can be trace fossils? After all, unearthed pottery is indirect evidence of living human creatures having been present in the environment, and, as the BGS also points out "the word fossil is derived from the Latin fossilis meaning 'unearthed'."

However, if the term originally simply meant something unearthed, then although the bits of pot would count as fossils – based on that argument so would potatoes growing in farmers' fields. So, clearly the English word 'fossil' has a more specific meaning in common use than its Latin ancestor.

But going by the BGS definition, Dr Bunbury's unearthed samples of pottery are certainly evidence of organisms left in sediment, so might be considered fossils. These fossils are not the remains of dead organisms, but neither is 'fossil' here simply a metaphor (not even a dead metaphor).

Work cited:
  • Dariush, A, Khosroshahi, H. G., Ponman, T. J., Pearce, F., Raychaudhury, S. & Hartley, W. (2007), The mass assembly of fossil groups of galaxies in the Millennium simulation, Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, 21 November 2007, Pages 433-442, https://doi.org/10.1111/j.1365-2966.2007.12385.x
  • Gibson, Carl H. (1980) Fossil Temperature, Salinity, and Vorticity Turbulence in the Ocean. In Jacques C.J. Nihoul (Ed.) Marine Turbulence, Elsevier, pp. 221-257.
  • Kanagusuku, María José, Díaz-Giménez, Eugenia & Zandivarez, Ariel (2016) Fossil groups in the Millennium simulation – From the brightest to the faintest galaxies during the past 8 Gyr, Astronomy & Astrophysics, 586 (2016) A40, https://doi.org/10.1051/0004-6361/201527269.
  • Romero, I. C., Nuñez Otaño, N. B., Gibson, M. E., Spears, T. M., Fairchild, C. J., Tarlton, L., . . . O'Keefe, J. M. K. (2021). First Record of Fungal Diversity in the Tropical and Warm-Temperate Middle Miocene Climate Optimum Forests of Eurasia [Original Research]. Frontiers in Forests and Global Change, 4. https://doi.org/10.3389/ffgc.2021.768405
  • Zarattini, S., Biviano, A., Aguerri, J. A. L., Girardi, M. & D'Onghia, E. (2012) Fossil group origins – XI. The dependence of galaxy orbits on the magnitude gap, Astronomy & Astrophysics, 655 (2021) A103, DOI: https://doi.org/10.1051/0004-6361/202038722.
Notes:

1 "Fossils are the preserved remains of plants and animals whose bodies …". But this suggests that fungi do not form fossils. The same site points out that "We tend to think of fungi, such as mushrooms and toadstools, as being plants — but they are not. They neither grow from embryos nor photosynthesise and are put in a separate kingdom" (https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/plants-2/) – yet does not seem to mention any examples of fungi that have been fossilised (so the comment could be read to be meant to suggest that fossil fungi are found as well as fossil plants; but could equally well be read to mean that as fungi are not plants they do not fossilise).

The second quote here is more inclusive: "Preserved evidence of the body parts of ancient animals, plants and other life forms…" The site does also specify that "Remains can include microscopically small fossils, such as single-celled foraminifera…" (https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/fossils/).

So, just to be clear, fossil fungi have been found.



Fungal spores found in Thailand – figure 3 from Romero et al, 2021. These fossils were recovered form lignite (a form of coal) deposited in the Miocene epoch.
Copyright © 2021 Romero, Nuñez Otaño, Gibson, Spears, Fairchild, Tarlton, Jones, Belkin, Warny, Pound and O'Keefe; distributed under the terms of the Creative Commons Attribution License (CC BY).

2 If the roots were themselves fossilised then these would surely be body fossils as roots are parts of plant. Presumably this is meant to refer to the channels in soil when the roots grow through the soil.


Is the Big Bang Theory mistaken?

Not science fiction, but fictional science

Keith S. Taber

we are made of particles that have existed since the moment the universe began…those atoms travelled 14 billion years through time and space

The Big Bang Theory (but not quite the big bang theory).

What is the Big Bang Theory?

The big bang theory is a theory about the origin and evolution of the universe. Being a theory, it is conjectural, but it is the theory that is largely taken by scientists as our current best available account.

According to big bang theory, the entire universe started in a singularity, a state of infinite density and temperature, in which time space were created as well as matter. As the universe expanded it cooled to its present state – some, about, 13.8 billion years later.

Our current best understanding of the Cosmos is that the entire Universe was formed in a 'big bang'
(Image by Gerd Altmann from Pixabay)

The term 'big bang' was originally intended as a kind of mockery – a sarcastic description of the notion – but the term was adopted by scientists, and has indeed become widely used in general culture.

Which brings me to 'The Big Bang Theory', which is said to have been the longest ever running sitcom ('situation comedy') – having been in production for longer than even 'Friends'.

The Big Bang Theory: Not science fiction, but fictional science? (Five of these characters have PhDs in science: one 'only' has a master's degree in engineering.)

A situation comedy is set around a situation. The situation was that two Cal Tech physicists are sharing an apartment. Leonard (basically a nice guy, but not very successful with women) is flatmate to Sheldon, a synaesthete, and kind of savant (a device on which to lever much of the humour) – a genius with an encyclopaedic knowledge of most areas of science but a deficient 'theory of mind' such that he lacks

  • insight into others, and so also
  • empathy, and
  • the ability to tell when people are using humour or being sarcastic to him.

If most physicists were like Sheldon we could understand why the big bang theory is still called the big bang theory even though the term was intended to be facetious. The show writers claim that Sheldon was not deliberately written to be on the autistic spectrum, but he tends to take statements literally: when it is suggested that he is crazy, he responds that he knows he is not as his mother had him tested as a child.

Sheldon (at right, partially in shot) has been widely recognised by viewers as showing signs of high-functioning Autism or Aspergers syndrome. (Still from The Big Bang Theory)

These guys hang out with Raj (Rajesh), an astrophysicist and Cambridge graduate so shy he is unable to speak to women, or indeed in their presence (presumably not a problem inherited from his father who is is a successful gynaecologist in India), and an engineer, Howard, who to my viewing is just an obnoxious creep with no obvious redeeming qualities. (But then I've not seen the full run.) When Howard becomes a NASA astronaut, he is bullied by the other astronauts, and whilst bullying is never acceptable, it is difficult to be too judgemental in his case.

This group are scientists, and they are 'nerds'. They watch science fiction and superhero movies, buy comic books and action figures, play competitive board games and acquire all the latests technical gadgets. And, apart from Sheldon (who has a strong belief in following a principled rigorous regime of personal hygiene that makes close contact with other humans seem repulsive) they try, and largely fail, to attract women.

In case this does not seem sufficiently stereotypical, the situation is complete when a young woman moves into in the flat opposite Leonard and Sheldon: Penny is the 'hot' new neighbour, who comes across as a 'dumb blonde' (she wants to be an actress – she is actually a waitress whilst she works at that), something of a hedonist, and not having the slightest knowledge of, or interest in, science. Penny's plan in life is to become a movie star, and her back-up plan is to become a television star.

If Sheldon and his friends tend to rather fetishise science and see it as inherently superior to other ways of engaging in the world, then Penny seems to reflect the other side of 'the two cultures' of C. P. Snow's famous lecture/essay that described an arts-science divide in mid-twentieth century British public life. That is, not only an acknowledged ignorance of scientific matters, but an ignorance that is almost worn as a badge of honour. Penny, of course, actually has a good deal of knowledge about many areas of culture that our 'heroes' are ignorant of.

Initially, Penny is the only lead female character in the show. This creates considerable ambiguity in how we are expected to see the show's representations of scientists during the early series. Is the viewer meant to be sharing their world where women are objects of recreation and sport and a distraction from the important business of the scientific quest? Or, is the audience being asked to laugh at these supposedly highly intelligent men who actually have such limited horizons?

Sheldon: I am a physicist. I have a working knowledge of the entire universe and everything it contains.

Penny. Who's Radiohead?

[pause]

Sheldon: I have a working knowledge of important things in the universe.

Penny has no interest in science

So, the premise is: can the nerdy, asthmatic, short-sighted, physicist win over the pretty, fun-loving, girl-next-door who is clearly seen to be 'out of his league'.

Spoiler alert

Do not read on if you wish to watch the show and find out for yourself.  😉

A marriage made in the heavens?

I recently saw an episode in series n (where n is a large positive integer) where Leonard and Penny decided to go to Las Vagas and get married. Leonard said he had written his own marriage vows – and it was these that struck me as problematic. My complaint was nothing to do with love and commitment, but just about physics.

Cal Tech physicist Leonard Hofstadter (played by Johnny Galecki) wrote his own vows for marriage to Penny (Kaley Cuoco) in 'The Big Bang Theory'

A non-physical love?

I made a note of Leonard's line:

"Penny, we are made of particles that have existed since the moment the universe began. I like to think those atoms travelled 14 billion years through time and space to create us so that we could be together and make each other whole."

Leonard declares his love

Sweet. But wrong.

Perhaps Leonard had been confused by the series theme music, the 'History of Everything', by the band Barenaked Ladies. The song begins well enough:

"Our whole universe was in a hot dense state

Then nearly fourteen billion years ago, expansion started…"

Lyrics to History of Everything (The Big Bang Theory Theme)

but in the second verse we are told

"As every galaxy was formed in less time than it takes to sing this song.

A fraction of a second and the elements were made."

Lyrics to History of Everything (The Big Bang Theory Theme)

which seems to reflect a couple of serious alternative conceptions.

So, the theme song seems to suggest that once the big bang had occurred, "nearly fourteen billion years ago", the elements were formed in a matter of seconds, and the galaxies in a matter of minutes. Leonard goes further, and suggests the atoms that he and Penny are comprised of have existed since "the moment the universe began". This is all contrary to the best understanding of physicists.

Surely Leonard, who defended his PhD thesis on particle physics, would know more about the canonical theories about the formation of those particles? (If not, he could ask Raj who once applied for a position in stellar evolution.)

The "hot dense state" was so hot that no particles could have condensed out. Certainly, some particles began to appear very soon after the big bang, but for much of the early 'history of everything' the only atoms that could exist were of the elements hydrogen, helium and lithium – as only the nuclei of these atoms were formed in the early universe.

The formation of heavier elements – carbon, oxygen, silicon and all the rest – occurred in stars – stars that did not exist until considerable cooling from the hot dense state had occurred. (See for example, 'A hundred percent conclusive science. Estimation and certainty in Maisie's galaxy'.) Most of the matter comprising Leonard, Penny, and the rest of us, does not reflect the few elements formed in the immediate aftermath of the big bang, but heavier elements that were formed billions of years later in stars that went supernovae and ejected material into space. 1 As has often been noted, we are formed from stardust.

"…So don't forget the human trial,
The cry of love, the spark of life, dance thru the fire

Stardust we are
Close to divine
Stardust we are
See how we shine"

From the lyrics to 'Stardust we are' (The Flower Kings – written by Roine Stolt and Tomas Bodin)

Does it matter – it is only pretend

Of course The Big Bang Theory (unlike the big bang theory) is not conjecture, but fiction. So, does it matter if it gets the science wrong? The Big Bang Theory is not meant to be science fiction, but a fiction that uses science to anchor it into a situation that will allow viewers to suspend disbelief.

Leonard is a believable character, but Sheldon is an extreme outlier. Howard and Raj are caricatures, exaggerations, as indeed are Amy (neurobiologist) and Bernadette (microbiologist) the other core characters introduced later.

But the series creators and writers seem to have made a real effort at most points in the show to make the science background authentic. Dialogue, whiteboard contents, projects, laboratory settings and the like seem to have been constructed with great care so that the scientifically literate viewer is comfortable with the context of the show. This authentic professional context offers the credible framework within which the sometimes incredible events of the characters' lives and relationships do not seem immediately ridiculous.

In that context, Leonard getting something so wrong seems incongruent.

Then again, he is in love, so perhaps his vows are meant to tell the scientifically literate viewer that there is a greater truth than even science – that in matters of the heart, poetic truth trumps even physics?

A Marillion song tells us:

A wise man once wrote
That love is only
An ancient instinct
For reproduction
Natural selection
A wise man once said
That everything could be explained
And it's all in the brain

Lyrics from 'This is the 21st Century' (Hogarth)

But as the same song asks: "where is the wisdom in that?"

Source cited:
  • Snow, C. P. (1959/1998). The Rede Lecture, 1959: The two cultures. In The Two Cultures (pp. 1-51). Cambridge University Press.
Note:

1 I was tempted to write 'most of the atoms'. Certainly most of the mass of a person is made up of atoms 2 that were formed a long time after the big bang. However, in terms of numbers of atoms, there are more of the (lightest) hydrogen atoms than of any other element: we are about 70% water, and water comprises molecules of H2O. So, that is getting close to half the atoms in us before we consider all the hydrogen in the fats and proteins and so forth.

2 That, of course, assumes the particles we are made of are atoms. Actually, we are comprised chemically of molecules and ions and relatively very, very few free atoms (those that are there are accidentally there in the sense they are not functional). No discrete atoms exist within molecules. So, to talk of the hydrogen atoms in us is to abstract the atoms from molecules and ions.

Leonard confuses matters (and matter) by referring initially to particles (which could be nucleons, quarks?) but then equating these to atoms – even though atoms are unlikely to float around for nearly 14 billion years without interacting with radiation and other matter to get ionised, form molecules, that may then dissociate, etc.

For many people reading this, I am making a pedantic point. When we talk of the atoms in a person's body, we do not actually mean atoms per se, but component parts of molecules of compounds of the element indicated by the atom referred to*. A water molecule does not contain two hydrogen atoms and an oxygen atom, but it does contain two hydrogen atomic nuclei, and the core of an oxygen atom (its nucleus, and inner electron 'shell') within an 'envelope' of electrons.

* So, it is easier to use the shorthand: 'two atoms of hydrogen and one of oxygen'.

The reason it is sometimes important to be pedantic is that learners often think of a molecule as just a number of atoms stuck together and not as a new unitary entity composed of the same set of collective components but in a new configuration that gives it different properties. (For example, learners sometimes think the electrons in a covalent bond are still 'owned' by different atoms.) There is an associated common alternative conception here: the assumption of initial atomicity, where students tend to think of chemical processes as being interactions between atoms, even though reacting substances are very, very rarely atomic in nature.

Read about the assumption of initial atomicity

Fingerprinting an exoplanet

Life, death, and multiple Gaias

Keith S. Taber

NASA might be said to be engaged in looking for other Gaias beyond our Gaia, as Dr Milam explained to another Gaia.

This post is somewhat poignant as something I heard on a radio podcast reminded me how science has recently lost one of its great characters, as well as an example of that most rare thing in today's science – the independent scientist.

Inside Science episode "Deep Space and the Deep Sea – 40 years of the International Whaling Moratorium", presented, perhaps especially aptly, by Gaia Vince

I was listening to the BBC's Inside Science pod-cast episode 'Deep Space and the Deep Sea – 40 years of the International Whaling Moratorium' where the presenter – somewhat ironically, in view of the connection I was making, Gaia Vince – was talking to Dr Stefanie Milam of Nasa's Goddard Space Flight Centre about how the recently launched James Webb Space Telescope could help scientists look for signs of life on other planets.

From: https://jwst.nasa.gov/content/meetTheTeam/people/milam.html

Dr Milam explained that

"spectra…give us all the information that we really need to understand a given environment. And that's one of the amazing parts about the James Webb space telescope. So, what we have access to with the wavelengths that the James Webb space telescope actually operates at, is that we have the fingerprint pattern of given molecules, things like water, carbon monoxide, carbon dioxide, all these things that we find in our own atmosphere, and so by using the infrared wavelengths we can look for these key ingredients in atmospheres around other planets or even, actually, objects in our own solar system, and that tells us a little bit about what is going on as far as the dynamics of that planet, whether or not its has got geological activity, or maybe even something as crazy as biology."

Dr Stefanie Milam, interviewed for 'Inside Science'
"Webb has captured the first clear evidence of carbon dioxide (CO2) in the atmosphere of a planet outside of our solar system!" (Hot Gas Giant Exoplanet WASP-39 b Transit Light Curve, NIRSpec Bright Object Time-Series Spectroscopy.)
Image: NASA, ESA, CSA, and L. Hustak (STScI). Released under 2.0 Generic (CC BY 2.0) License – Some rights reserved by James Webb Space Telescope
Do molecules have fingerprints

Fingerprints have long been used in forensic work to identify criminals (and sometimes their victims) because our fingerprints are pretty unique. Even 'identical' twins do not have identical fingerprints (thought I suspect that fact rather undermines some crime fiction plots). But, to have fingerprints one surely has to have fingers. A palm print requires a palm, and a footprint, a foot. So, can molecules, not known for their manual dexterity, have fingerprints?

Well, it is not exactly by coincidence (as the James Webb space telescope has had a lot of media attention) that I very recently posted here, in the context of new observations of the early Universe, that

"Spectroscopic analysis allows us to compare the pattern of redshifted spectral lines due to the presence of elements absorbing or emitting radiation, with the position of those lines as they are found without any shift. Each element has its own pattern of lines – providing a metaphorical fingerprint.

from: A hundred percent conclusive science. Estimation and certainty in Maisie's galaxy

In chemistry, elements and compounds have unique patterns of energy transitions which can be identified through spectroscopy. So, we have 'metaphorical fingerprints'. To describe a spectrum as a chemical substance's (or entity's, such as an ion's) fingerprint is to use a metaphor. It is not actually a fingerprint – there are no fingers to leave prints – but this figure of speech gets across an idea though an implicit comparison with something already familiar. *1 That is, it is a way of making the unfamiliar familiar (which might be seen as a description of teaching!)

Dead metaphors

But perhaps this has become a 'dead metaphor' so that now chemicals do have fingerprints? One of the main ways that language develops is by words changing their meanings over time as metaphors become so commonly used they case to be metaphorical.

For example, I understand the term electrical charge is a dead metaphor. When electrical charge was first being explored and was still unfamiliar, the term 'charge' was adopted by comparison with the charging of a canon or the charge of shot used in a shotgun. The shot charge refers to the weight of shot included in a cartridge. Today, most people would not know that, whilst being very familiar with the idea of electrical charge. But when the term electrical charge was first used most people knew about charging guns.

So, initially, electrical 'charge' was a metaphor to refer to the amount of 'electricity' – which made use of a familiar comparison. Now it is a dead metaphor, and 'electrical charge' is now considered a technical tern in its own right.

Another example might be electron spin: electrons do not spin in the familiar sense, but really do (now) have spin as the term has been extended to apply to quanticles with inherent angular momentum by analogy with more familiar macroscopic objects that have angular momentum when they are physically rotating. So, we might say that when the term was first used, it was a metaphor, but no longer. (That is, physicists have expanded the range of convenience of the term spin.)

Perhaps, similarly, fingerprint is now so commonly used to mean a unique identifier in a wide range of contexts, that it should no longer be considered a metaphor. I am not sure if that is so, yet, but perhaps it will be in, say, a century's time – and the term will be broadly used without people even noticing that many things have acquired fingerprints without having fingers. (A spectrum will then actually be a chemical substance's or entity's fingerprint.) After all, many words we now commonly use contain fossils of their origins without us noticing. That is, metaphorical fossils, of course. *2

James Lovelock, R.I.P.

The reason I found this news item somewhat poignant was that I was listening to it just a matter of weeks after the death (at age 103) of the scientist Jim Lovelock. *3 Lovelock invented the device which was able to demonstrate the ubiquity of chlorofluorocarbons (CFCs) in the atmosphere. These substances were very commonly used as refrigerants and aerosol propellants as they were very stable, and being un-reactive (so non-toxic) were considered safe.

But this very stability allowed them to remain in and spread through the atmosphere for a very long time until they were broken down in the stratosphere by ultraviolet radiation to give radicals that reacted with the ozone that is so protective of living organisms. Free radical reactions can occur as chain reactions as when a radical interacts with a molecule it leads to a new molecule, plus a new radical which can often take part in a further interaction with another molecule: so, each CFC molecule could lead to the destruction of many ozone molecules. CFCs have now been banned for most purposes to protect the ozone 'layer', and so us.

Life is chemistry out of balance

But another of Lovelock's achievements came when working for NASA to develop means to search for life elsewhere in the universe. As part of the Mariner missions, NASA wanted Lovelock to design apparatus that could be sent to other worlds and search for life (and I think he did help do that), but Lovelock pointed out that one could tell if a planet had life by a spectroscopic analysis.

Any alien species analysing light passing through earth's atmosphere would see its composition was far from chemical equilibrium due to the ongoing activity of its biota. (If life were to cease on earth today, the oxygen content of the atmosphere would very quickly fall from 21% to virtually none at all as oxygen reacts with rocks and other materials.) If the composition of an atmosphere seemed to be in chemical equilibrium, then it was unlikely there was life. However, if there were high concentrations of gases that should react together or with the surface, then something, likely life, must be actively maintaining that combination of gases in the atmosphere.

"Living systems maintain themselves in a state of relatively low entropy at the expense of their nonliving environments. We may assume that this general property is common to all life in the solar system. On this assumption, evidence of a large chemical free energy gradient between surface matter and the atmosphere in contact with it is evidence of life. Furthermore, any planetary biota which interacts with its atmosphere will drive that atmosphere to a state of disequilibrium which, if recognized, would also constitute direct evidence of life, provided the extent of the disequilibrium is significantly greater than abiological processes would permit. It is shown that the existence of life on Earth can be inferred from knowledge of the major and trace components of the atmosphere, even in the absence of any knowledge of the nature or extent of the dominant life forms. Knowledge of the composition of the Martian atmosphere may similarly reveal the presence of life there."

Dian R. Hitchcock and James E. Lovelock – from Lovelock's website (originally published in Icarus: International Journal of the Solar System in 1967)

The story was that NASA did not really want to be told they did not need to send missions with spacecraft to other words such as Mars to look for life, rather that they only had to point a telescope and analyse the spectrum of radiation. Ironically, perhaps, then, that is exactly what they are now doing with planets around other star systems where it is not feasible (not now, perhaps not ever) to send missions.

Gaia and Gaia

But Lovelock became best known for his development and championing of the Gaia theory. According to Gaia (the theory, not the journalist), the development of life on earth has shaped the environment (and not just exploited pre-existing niches) and developed as a huge integrated and interacting system (the biota, but also the seas, the atmosphere, freshwater, the soil,…) such that large scale changes in one part of the system have knock-on effect elsewhere. *4

So, Gaia can be understood not as the whole earth as a planet, or just the biota as the collective life in terms of organisms, but rather as the dynamic system of life of earth and the environment it interacts with. In a sense (and it is important to see this is meant as an analogy, a thinking tool) Gaia is like some supra-organism. Just as snail has a shell that it has produced for its self, Gaia has shaped the biosphere where the biota lives. *4

The system has built in feedback cycles to protect it from perturbations (not by chance, or due to some mysterious power, but due to natural selection) but if it is subject to a large enough input it would shift to a new (and perhaps very different) equilibrium state. *5 This certainly happened when oxygen releasing organisms evolved: the earth today is inhospitable to the organisms that lived here before that event (some survived to leave descendants, but only in places away from the high oxygen concentrations, such as in lower lays of mud beneath the sea), and most organisms alive today would die very quickly in the previous conditions.

It would be nice to think that Gaia, the science journalist that is, was named after the Gaia theory – but Lovelock only started publishing about his Gaia hypothesis about the time that Gaia was born.*6 So, probably not. Gaia is a traditional girl's name, and was the name of the Greek goddess who personified the earth (which is why the name was adopted by Lovelock).

Still, it was poignant to hear a NASA scientist referring to the current value of a method first pointed out by Lovelock when advising NASA in the 1970s and informed by his early thinking about the Gaia hypothesis. NASA might be said to now be engaged in looking for other Gaias on worlds outside our own solar system, as Dr Milam explained to – another – Gaia here on earth.

Notes:

*1 It is an implicit comparison, because the listener/reader is left to appreciate that it is meant as a figure of speech: unlike in a simile ('a spectrum is like a fingerprint') where the comparison is made explicit .

*2 For some years I had a pager (common before mobile phones) – a small electronic device which could receive a text message, so that my wife could contact me in an emergency if I was out visiting schools by phoning a message to be conveyed by a radio signal. If I had been asked why it was called a pager, I would have assumed that each message of text was considered to comprise a 'page'.

However, a few weeks ago I watched an old 'screwball comedy' being shown on television: 'My favourite wife' (or 'My favorite [sic] wife' in US release).

(On the very day that Cary Grant remarries after having his first wife, long missing after being lost at sea, declared legally dead, wife number one reappears having been rescued from a desert island. That this is a very unlikely scenario was played upon when the film was remade in colour, as 'Move Over Darling', with Doris Day and James Garner. The returned first wife, pretending to be a nurse, asks the new wife if she is not afraid the original wife would reappear, as happened in that movie; eliciting the response: 'Movies. When do movies ever reflect real life?')

Some of the action takes place in the honeymoon hotel where groom has disappeared from the suite (these are wealthy people!) having been tracked down by his first wife. The new wife asks the hotel to page him – and this is how that worked with pre-electronic technology:

Paging Mr Arden: Still from 'My Favorite Wife'

*3 So, although I knew Lovelock had died (July 26th), he was still alive at the time of the original broadcast (July 14th). In part, my tardiness comes from the publicly funded BBC's decisions to no longer make available downloads of some of its programmes for iPods and similar devices immediately after broadcast. (This downgrading of the BBC's service to the public seems to be to persuade people to use its own streaming service.)

*4 The Gaia theory developed by Lovelock and Lyn Margulis includes ideas that were discussed by Vladimir Vernadsky almost a century ago. Although Vernadsky's work was well known in scientific circles in the Soviet Union, it did not become known to scientists in Western Europe till much later. Vernadsky used the term 'biosphere' to refer to those 'layers' of the earth (lower atmosphere to outer crust) where life existed.

*5 A perturbation such as as extensive deforestation perhaps, or certainly increasing the atmospheric concentrations of 'greenhouse' gases beyond a certain point.

*6 Described as a hypothesis originally, it has been extensibility developed and would seem to now qualify as a theory (a "consistent, comprehensive, coherent and extensively evidenced explanation of aspects of the natural world") today.

A hundred percent conclusive science

Estimation and certainty in Maisie's galaxy

Keith S. Taber

An image from the James Webb Space Telescope
(released images are available at https://webbtelescope.org/resource-gallery/images)

NASA's James Webb Space Telescope is now operational, and offering new images of 'deep space'. This has led to claims of finding images of objects from further away in the Universe, and so from further back in time, than previously seen. This should support a lot of new scientific work and will surely lead to some very interesting findings. Indeed, it seems to have had an almost immediate impact.

Maisie's galaxy

One of these new images is of an object known as:

CEERSJ141946.35-525632.8

or less officially (but more memorably) as

Masie's galaxy.

A red smudge on one of the new images has been provisionally identified as evidence of a galaxy as it was less than 300 000 000 years after the conjectured 'big bang' event understood as the origin of the universe. The galaxy is so far away that its light has taken since then to reach us.

Three hundred million years seems a very long time in everyday terms, but it a small fraction of the current age of the universe, believed to be around fourteen billion years. 1

300 000 000 years

≪ 14 000 000 000 years

The age estimate is based on the colour of the object, reflecting its 'redshift':

"Scientists with the CEERS Collaboration have identified an object–dubbed Maisie's galaxy in honor of project head Steven Finkelstein's daughter–that may be one of the earliest galaxies ever observed. If its estimated redshift of 14 is confirmed with future observations, that would mean we're seeing it as it was just 290 million years after the Big Bang."

University of Texas at Austin, UT News, August 04, 2022

(CEERS is the Cosmic Evolution Early Release Science Survey.)

This finding is important in understanding the evolution of the universe – for example, observing the earliest galaxies puts a limit on how long the universe existed before star formation started. (Although the episode was called 'The first galaxies at the universe's dawn' Masie's galaxy is thought to contain heavier elements that were produced in even earlier stars.)

Uncertainty in science (and certainty in reporting science)

So, the claim is provisional. It is an estimate awaiting confirmation.

Strictly, science is concerned with provisional knowledge claims. This is not simply because scientists can make mistakes. All measurements are subject to limits in precision (measurement 'errors'). More fundamentally, all measurements depend on a theory of the instrumentation used, and theoretical knowledge is always open to being revisited on the basis of new ways of understanding.

We may not expect the theory behind the metre rule to change any time soon (although even there, our understanding shifted somewhat with Einstein's theories) but many scientific observations depend on highly complex apparatus, both for data collection and analysis. Despite this, science is often represented in the media, both by commentators and sometimes scientists themselves, as if it produced absolute certainty.

Read about science in public discourse and the media

Read about scientific certainty in the media

A rough estimate?

In the case of Maisie's galaxy, the theoretical apparatus seems to be somewhat more sophisticated than the analytical method used to provisionally age the object. This was explained by Associate Professor Steve Finkelstein when he was interviewed on the BBC's Science in Action episode 'The first galaxies at the universe's dawn'.

Masie's galaxy – it's quite red.
The first galaxies at the universe's dawn. An episode of 'Science in Action'

Professor Finkelstein explained:

"We can look deep into out past by taking these deep images, and we can find the sort of faintest red smudges and that tells us that they are extremely far away, and from exactly how red they are we can estimate that distance."

Associate Professor Steve Finkelstein

So, the figure of 290 000 000 years after the big bang is an estimate. Fair enough, but what 'caught my ear', so to speak, was the contrast between the acknowledged uncertainty of the current estimate, and the claimed possibility of moving from this to absolute knowledge,

"If this distance we have measured for Masie's galaxy, of a red shift of 14, holds true, and I can't stress enough that we need spectroscopic confirmation to precisely measure that distance. [*] Where you take a telescope, could be James Webb, could be a different telescope, you observe it [the galaxy] and you split the light into its component colours, and you can actually precisely measure – measure the red shift, measure the distance – a hundred percent conclusively."

Associate Professor Steve Finke
[* To my ear, there might well be an edit at this point – the quote is based on what was broadcast which might omit or re-sequence parts of the interview.]

Spectroscopic analysis allows us to compare the pattern of redshifted spectral lines due to the presence of elements absorbing or emitting radiation, with the position of those lines as they are found without any shift. Each element has its own pattern of lines – providing a metaphorical fingerprint. A redshift (or blueshift) moves these lines to different parts of the spectrum, but does not change their collective profile as all the lines are moved to the same extent.

Spectral lines can be used like fingerprints to identify substances.
(Image by No-longer-here from Pixabay)

Some of these lines are fine, allowing precise measurements of wavenumber/frequency, and there are enough of them to be able to make very confident assignments of the 'fingerprints', and use this to estimate the shift. We might extend our analogy to a fingerprint on a rubber balloon which had been stretched since a fingerprint was made. In absolute terms, the print would no longer (or 'no wider' for that matter) fit the finger that made it, but the distortion is systematic allowing a match to be made – and the degree of stretching to be calculated.

If a pattern is distorted in a systematic way, we may still be able to match it to an undistorted version
(Original images by Clker-Free-Vector-Images (balloon), OpenClipart-Vectors (print) and Alexander (notepad) from Pixabay)

Yet, even though this is a method that is considered well-understood, reliable, and potentially very accurate and precise 2, I am not sure you can "precisely measure, measure the redshift, measure the distance. A hundred percent conclusively". Science, at least as I understand it, always has to maintain some small level of humility.

Scientists may be able to confirm and hone the estimate of 290 000 000 years after the big bang for the age of Maisie's galaxy. Over time, further observations, new measurements, refinement in technique, or even theory, may lead to successive improvements in that age measurement and both greater accuracy and greater precision.2 But any claim of a conclusive measurement to a precision of 100% has a finality that sounds like something other than science to me.

Notes

1 Oddly, most webages I've seen that cite values for the age of the universe do not make it explicit whether these are American (109) or English (1012) billions! It seems to be assumed that, as with sulfur [i.e., sulphur], and perhaps soon aluminum and fosforus, we are all using American conventions.

2 Precision and accuracy are different. Consider an ammeter.

An ammeter (Image by Gerd Altmann from Pixabay)

Due to the method of reading a needle position against a scale there is a limit to precision (perhaps assumed to the nearest calibration, so to ±0.5 calibrations). This measurement error of ±0.5 units is, in effect, a limit in detail or resolution, but not an 'error' in the everyday sense of getting something wrong. However, if the meter had been miscalibrated, or over time has shifted from calibration, so the needle is misaligned (so perhaps the meter reads +0.15 A when it is not connected into a circuit) then that is inaccuracy. There is always some level of imprecision (some limit on how precise we can be), even when we have an accurate reading.

In science, a measurement normally offers a best estimate of a true value, with an error range acknowledging how far the real value might be from that best estimate. See the example below: Measurement B claims the most precision, but is actually inaccurate. Measurement A is the most accurate (but least precise).

If we imagine that a galaxy was being seen as it was

275 000 000 years after the big bang

and three measurements of its age were given as:

A: 280 000 000 ± 30 000 000 years after the big bang

(i.e., 250 000 000 – 310 000 000)

B: 290 000 000 ± 10 000 000 years after the big bang

(i.e., 280 000 000 – 300 000 000)

C: 260 000 000 ± 20 000 000 years after the big bang

(i.e., 240 000 000 – 280 000 000)

then measurement B is more precise (it narrows down the possible range the most) but is inaccurate (as the actual age falls outside the range of this measurement). Of course, unlike in such a hypothetical example, in a real case we would not know the actual age to allow us to decide which of the measurements is more accurate.

Neuroadaptation gremlins on the see-saw in your brain

The brain's reward pathway is like a teeter-totter because…

Keith S. Taber

in your brain there is a teeter-totter like in a kids' playground…these neuroadaptation gremlins hopping on the pain side of the balance…the gremlins hop off …But if we …accumulate so many gremlins on the pain side of our balance …we've crossed over into the disease of addiction…we are craving because …it's the gremlins jumping up and down

Dr Anna Lembke talking on 'All in the mind'
Is there a see-saw in your brain?
(Original images by Image by mohamed Hassan and OpenClipart-Vectors from Pixabay) 

Dr Anna Lembke, Professor of Psychiatry at Stanford University explained how addiction relates to dopmaine and the brain's reward pathway with an analogy of a see-saw. She was talking to Sana Qadar for an episode of the the ABC programme 'All in the Mind' called 'How dopamine drives our addictions'.

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).

Read about science analogies

A fried brain

During the programme the interviewer (Qadar) uses a metaphor for how addiction influences brain chemistry:

Sana Qadar: "The problem is when we are becoming addicted to something, our brain's ability to naturally produce dopamine gets fried."

Anna Lembke: "So essentially what happens in the brain as we tip toward the compulsive cycle of overconsumption or addiction is that we start to down-regulate our own dopamine production and dopamine transmission in order to compensate for the ways that we are bombarding our brain's reward pathway with too much dopamine through ingestion of these incredibly potent and rewarding substances and behaviours."

What does Sana Qadar mean by 'fried'? Presumably not destroyed, as the subsequent interview suggests that recovery is possible (see below) – although the brain's ability to naturally produce dopamine would surely not recover from actual frying. So, perhaps, fried means disturbed, or damaged? Given the following dialogue it might mean thrown out of balance.

Perhaps Qadar was thinking of the brain as circuitry as the term is commonly applied to damaged circuits (I think the term derives from damage caused by overheating, as can happen when there is a 'short' for example, which does stop the 'fried' components functioning permanently). So, perhaps for Qadar this is a dead metaphor – a term which started as a metaphor but which, with habitual use, has come to be treated as having literal meaning – at least in relation to electrical circuits and, by analogy, brain circuitry?

A fried brain?
(Images by OpenClipart-Vectors and y Roger YI from Pixabay)

Balancing those gremlins

What I found especially interesting is the way Dr Lembke made extensive use of an analogy in her explanation, much in the way teacher might keep referring back to the same metaphor or analogy or model when introducing an abstract topic.

Sana Qadar tells listeners that "to explain how this process unfolds in the brain's reward pathway, Dr Lembke uses the analogy of a teeter-totter or seesaw":

"Because pleasure and pain are processed in the same part of the brain and work like opposite sides of the balance, it means for every pleasure there is a cost and that cost is pain.

So, if you imagine that in your brain there is a teeter-totter like in a kids' playground, that teeter-totter will tip to one side when we experience pleasure, and the opposite side when we experience pain.

But no sooner has that balance tipped to the side of pleasure, for example when I eat a piece of chocolate, then my brain will work very hard to restore a level balance or what neuroscientists call homeostasis. And it does that not just by bringing the balance level again but first by tipping it an equal and opposite amount to the to the side of pain, that is the after-effect, the come-down. I imagine that as these neuroadaptation gremlins hopping on the pain side of the balance to bring it level again.

Now, if we wait long enough, the gremlins hop off and homeostasis is restored as we go back to our baseline tonic level of dopamine firing. But if we continue to ingest addictive substances or behaviours over very long periods of time, we essentially accumulate so many gremlins on the pain side of our balance that we are in a chronic dopamine deficit state, and that is essentially where we get when we've crossed over into the disease of addiction.

Dr Anna Lembke talking on 'All in the mind'

As part of the programme of treatment Dr Lembke has developed for those suffering from additions she often recommends a period of complete abstinence – asking her clients to abstain for at least 30 days

Because 30 days is about the minimum amount of time it takes for the brain to restore baseline dopamine firing. Another way of saying this is 30 days is about the minimum amount of time it takes for the gremlins to hop off the pain side of the balance so that homeostasis or balance can be restored.

… I think in many people it is possible with abstinence to reset the reward pathway, the brain has an enormous amount of plasticity.

Dr Anna Lembke talking on 'All in the mind'

Abstinence is obviously not easy when the person is constantly faced with relevant triggers, as

"…what happens when we are triggered is that we release a little bit of dopamine in the reward pathway. … But if we wait long enough, those gremlins will hop off the pain side of the balance, and balance is restored….we are craving because we are in a dopamine deficit state, it's the gremlins jumping up and down on the pain side of the balance. But if we can just wait a few more moments, they will get off, homeostasis will be restored and that feeling will pass."

"…It's a fine line between pleasure and pain
You've done it once you can do it again
Whatever you've done don't try to explain
It's a fine, fine line between pleasure and pain.."

From the lyrics of the song 'Pleasure and Pain' (covered by Manfred Mann's Earth Band), by Holly Knight & Michael Donald Chapman

It's a fine line between pleasure and pain

Sana Qadar suggests that certain kinds of pain can actually be good for us. From a biological perspective this is clearly so, as pain provides signals to motivate us to change our behaviour (move away from the fire, put down the very heavy object), but that is not what she is referring to. Rather, that "Dr Lembke says it has to do with the fact that pleasure and pain are processed in the same part of the brain":

Well, just like when we press on the pleasure side of the balance the gremlins hop on the pain side and ultimately shift our hedonic setpoint or our joy setpoint to the side of pain, it's also true that when we press on the pain side of the balance, so we intentionally invite psychologically or physically painful experiences into our lives, that those neuroadaptation gremlins will then hop on the pleasure side of the balance and we will start to up-regulate our own endogenous dopamine, not as the primary response to the stimulus but as the after-response

…I'm absolutely not talking about extreme forms of pain like cutting [which is] not a healthy way to get dopamine

…[For example] Michael was somebody who was addicted to cocaine and alcohol, and got into recovery and immediately experienced the dopamine deficit state, those gremlins on the pain side of the balance, he was anxious, he was irritable, and he also felt very numb, kind of an absence of emotions, which was really scary for him.

And he serendipitously discovered in early recovery that if he took a very cold shower, that created for him the same kinds of feelings, in a muted way, that he used to get from drugs, so he got into this practice of every morning taking a cold shower, and it worked great for him."

Dr Anna Lembke talking on 'All in the mind'

Gremlins, indeed?

Of course there is no see-saw in the brain, but a see-saw is a familiar everyday object that people understand can be balanced – or not. And that if more children (of similar size) load up one side than the other it will be out of balance – and it will only level up once the loads are balanced.

Strictly, there are some complications here with the analogue. If the children are at different distances from the fulcrum that will change their turning effect (so two children could balance one of similar mass according to where they are positioned). Similarly, when the moments are balanced the see-saw will not necessarily be level: as 'balance' means no overall turning effect. So, if the see-saw was already at an angle to the horizontal, loading it up in a balanced way should not shift it back to being level.

Perhaps there is something comparable in the reward system to whereabouts children sit on the see-saw – (perhaps some synapses are more sensitive to the effects of dopamine than others?), but this would be over-complicating an analogy that is intended to offer a link to a simple everyday phenomenon.

Are gremlins like children – do they come in different sizes? Perhaps it seems a little childish even to talk of such things in the brain. But there was once a strong (if discouraged these days 1) tradition of considering a homunculus, a little observer, inside the brain as if in a control room. Moreover, if the lauded physicist James Clerk Maxwell could invoke his famous demon to explain aspects of thermodynamics, we should not censure Lembke's metaphorical gremlins.

If this comparison was being used as a teaching analogy in a formal course, then we might want a more careful setting out of the positive and negative aspects of the analogy (those things that do, and do not, map across from the see-saw to the reward system). But Dr Lembke is not trying to teach her clients to pass tests about brain science, but rather give them a way of thinking about their problems that can help them plan and change behaviour – that is, a useful and straightforward model they can apply in overcoming their addictions.

An episode of the radio progrmme/podcast 'All in the mind'
To find out more

Prof. Lembke was talking about a very important topic and here I have only abstracted particular comments to illustrate her use of the analogy. For a fuller account of the topic, and in particular Prof. Lembke's clinical work to help people struggling with addiction, please refer to the full interview.

Work cited:
Note

1 The term is still use, but in a somewhat different sense:

"in neuroanatomy, the cortical homunculus represents either the motor or the sensory distribution along the cerebral cortex of the brain. The motor homunculus is a topographic representation of the body parts and its correspondents along the precentral gyrus of the frontal lobe. While the sensory homunculus is a topographic representation of the body parts along the postcentral gyrus of the parietal lobe."

Nguyen and Duong, 2021

So, nowadays we each have two 'little men' in our brains.

Plus รงa change – balancing forces is hard work

Confusing steady states and equilibrium?

Keith S. Taber

"…I am older than I once was
And younger than I'll be
But that's not unusual
No, it isn't strange
After changes upon changes
We are more or less the same
After changes we are more or less the same…"

From the lyrics of 'The Boxer' (Simon and Garfunkel song) by Paul Simon

In a recent post I discussed the treatment of Newtonian forces in a book (Thomson, 2005) about the history of natural theology (a movement which sought to study the natural world as kind of religious observance – seeking to glorify God by the study of His works) and its relationship to the development of evolutionary theory.

The book was written by a prestigious scientist, who had held Professorships at both Yale in the US and at Oxford. Yet the book contained some erroneous physics – 'howlers' of the kind that are sometimes called 'schoolboy errors' (as presumably most schoolgirls would be careful not to make them?)

Read 'Even Oxbridge professors have misconceptions'

'The Watch on the Heath'

by Prof. Keith Thomson

My point is not to imply that this is a poor read – the book has much to commend it, and I certainly thought it was worth my time. I found it an informative read, and I have no reason to assume that the author's scholarship in examining the historical sources was was not of the highest level – even if his understanding of some school physics seemed questionable. I think this highlights two features of science:

  1. Science is so vast that research scientists setting out to write 'popular' science books for a general readership risk venturing into areas outside their specialist knowledge – areas where they may lack expertise 1
  2. Some common alternative conceptions ('misconceptions') are so insidious that we confidently feel we understand the science we have been taught whilst continuing to operate with intuitions at odds with the science.

Out of specialism

In relation to the first point, I previously highlighted a reference to "Einstein's relativity theory" being part of quantum physics, and later in the book I found another example of a non-physicist confusing two ideas that may seem similar to the non-specialist but which to a physicist should not be confused:

"In the 1930s, Arthur Holmes worked out the geology of the mechanism [underpinning plate tectonics] and the fact that the earth's inner heat (like that of the sun) comes from atomic fission."
p.190

Thomson, 2005: 190

The earth contains a good deal of radioactive material which, through atomic fission, heats up the earth from within. This activity has contributed to the, initially hot, earth cooling much more slowly than had once been assumed – most notably according to modelling undertaken by Thomson's namesake, Lord Kelvin.2 Kelvin did not know about nuclear fission.

But the sun is heated by a completely different kind of nuclear reaction: fusion. The immense amount of energy 'released' during this process enables stars to burn for billions of years without running out of hydrogen fuel.3

Lord Kelvin did not know about that either, leading to him suggesting

"…on the whole most probable that the sun has not illuminated the earth for 100,000,000 years, and almost certain that he has not done so for 500,000,000 years"

Thomson, 1862

Kelvin suggested this was 'almost' but not 'absolutely' certain – a good scientist should always keep an open mind to the possibility of having missed something (take note, BBC's Nick Robinson).

We now think the sun has been 'illuminating' for about 4 600 000 000 years, almost ten times as long as Kelvin's upper limit. It may seem strange that a serious scientist should refer to the sun as 'he', but this kind of personification was once common in scientific writings.

Read about personification in science

The first atomic weapons were based on fission processes of the kind used in nuclear power stations.

Hydrogen bombs are much more devastating still, making use of fusion as occurs deep in the sun.

(Image by Gerd Altmann from Pixabay)

A non-scientist may feel this conflation of fission and fusion is a minor technical detail. But it is a very significant practical distinction.

For one thing the atomic bombs that were used to devastate Hiroshima and Nagasaki were fission devices. The next generation of atomic weapons, the 'hydrogen bombs' were very much more powerful – to the extent that they used a fission device as a kind of detonator to set off the main bomb! It is these weapons, fusion weapons, which mimic the processes at the centre of stars such as the sun.

…The rusty wire that holds the cork that keeps the anger in
Gives way and suddenly it's day again
The sun is in the east
Even though the day is done
Two suns in the sunset, hmph
Could be the human race is run…

From the lyrics of 'Two suns in the sunset' (Pink Floyd song) by Roger Waters

In terms of peaceful technologies, fission-based nuclear power stations, whilst not using fossil fuels, have been a major concern because of the highly radioactive waste which will remain a high health risk for many thousands of years, and because of the dangers of radiation leaks – very real risks as shown by the Three Mile Island (USA) and Windscale (England) accidents, and much more seriously at Fukushima (Japan) and, most infamously, Chernobyl (then USSR, now Ukraine). There are also serious health and human rights issues dogging the mining of uranium ore, which is, of course, a declining resource.

For decades scientists have been trying to develop, as an alternative, nuclear fusion based power generation which would be a source of much cleaner and sustainable power supplies. This has proved very challenging because the conditions under which fusion takes place are so much more extreme. Critically, no material can hold the plasma at the extreme temperatures, so it has to be magnetically suspended well away from the containment vessel 'walls'.

The tenacious nature of some misconceptions

My second point, the insidious nature of some common alternative conceptions, is a challenge for science teachers as simply giving clear, accurate presentations with good examples may not be enough to bring about change in well-established and perhaps intuitive ways of thinking, even when students study hard and think they have learnt what has been taught.

I suggested this was reflected in Prof. Thomson's text (Keith, that is, not Sir William) in his use of references to Newton's ideas about force and motion. Prof. Thomson was not as a biologist therefore seeking to avoid referring to physics, but rather actively engaging with Newton's notions of inertia and the action of forces to make his points. Yet, also, seemingly misusing Newtonian mechanics because of a flawed understanding. Likely, as with many students, Prof. Thomson's intuitive physics was so strong that although he had studied Newton's laws, and can state them, when he came to apply them his own 'common-sense' conceptions of force and motion insidiously prevailed.

The point is not that Prof. Thomson has got the physics wrong (as research suggests most people do!) but that he was confident enough in his understanding to highlight Newtonian physics in his writing and, in effect, seek to teach his readers about it.

Newton's laws

What are commonly known as 'Newton' three laws of motion' can be glossed simply as:

N1: When no force is acting, an object does not change its motion: if stationary, it remains stationary; if moving, it carries on moving at the same speed in the same direction.

Indeed, this is also true if forces are acting, but they cancel because they are balanced, i.e.,

N1': When no net (overall, resultant) force is acting, an object does not change its motion: if stationary, it remains stationary; if moving, it carries on moving at the same speed in the same direction.

N2: When a net force is acting on a body it changes its motion in a way determined by the magnitude and direction of the force. (The change in velocity takes place in the direction of the force, and at a rate depending on the magnitude of the force).

So, if the force acts along the direction of motion, then the speed will change but not direction; but if the force acts in any other direction it will lead to a change in direction.

Strictly, the law relates to the 'rate of change of momentum' but assuming the mass of the body is fixed, we can think in terms of changes of velocity. 4

N3: Forces are interactions between two bodies/objects (that attract or repel each other): the same size force acts on both. (This is sometimes unfortunately phrased as 'every action having an equal and opposite reaction') 5.

These (perhaps) seem relatively simple, but there are complications in applying them. Very simply, the first law,when applied to moving bodies does not seem to fit our experience (moving bodies often seem to come to a stop by themselves – due to forces that we do not always notice).

The second law relates an applied force to a process of change, but it is very easy to instead think of the applied force directly leading to an outcome. That is people often equate the change in direction with the final direction. The change occurs in the direction of the force: that does not mean the final direction is the direction of the force.

The third law is commonly misapplied by assuming that if 'forces come in pairs' these will be balanced and cancel out. But they cannot cancel out because they are acting on the two bodies. (If your friend hits you in the eye after one too many pedantic complaints about her science writing you cannot avoid a black eye simply by hitting her back just as hard!)

A N3 force 'pair' does not balance out!

Often objects are in equilibrium because the forces acting on them are balanced. But they are never in equilibrium just because a force on them is also acting on another body! An apple hangs from a tree because the branch pulls it up the same amount as its weight pulls it down: these are two separate forces, each of which is also acting on the other body involved (the branch, and the earth, respectively).

Read about learning difficulties and Newton's third law

Thomson's 'Newtonian Physics'

In the previous posting I noted that Prof. Thomson had written

  • "Any trajectory other than a straight line must be the result of multiple forces acting together."
  • "the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun…
  • "a Newtonian balance of forces… rocks: gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again"

The first two statements are simply wrong according to conventional physics. Curved paths are often the result of a single force acting. The earth and moon orbit because they are both the subject of unbalanced forces.

Those two statements are contrary to N1 and N2.

The third statement seemed to suggest that a balance of forces was somehow considered to bring about changes. The suggestion appeared to be that a cycle of changes might be due to a balance of forces. But I acknowledged that "this reference to Hutton's ideas seems to preview a more detailed treatment of the new geology in a later chapter in the book (that I have not yet reached), so perhaps as I read on I will find a clearer explanation of what is meant by these changes being based on a theory of balance of forces".

Now I have finished the book, I wanted to address this.

A sort of balance

Prof. Thomson discusses developing ideas in geology about how the surface of the earth came to have its observed form. Today we are familiar with modern ideas about the structure of the earth, and continental drift, and most people have seen this represented in various ways.

Image by Venita Oberholster from Pixabay
Image by Clker-Free-Vector-Images from Pixabay
Original images by by Michel Müller from Pixabay

However, it was once widely assumed that the earth's surface was fairly static , but had been shaped by violent events in the distant past – a view sometimes called 'catastrophism'. One much referenced catastrophe was the flood associated with the biblical character Noah (of Ark fame) that was sometimes considered to have been world-wide deluge. (Those who considered this were aware that this required a source of water beyond normal rainfall – such as perhaps vast reservoirs of water escaping from underground).

The idea that the earth was continually changing, and that forces that acted continuously over vast periods of time could slowly (much too slowly for us to notice) lead to the formation of, for example, mountain ranges seemed less feasible.

Yet we now understand how the tectonic plates float on a more fluid layer of material and how these plates slowly collide or separate with the formation of new crust where they move apart. Vast forces are at work and change is constant, but there are cyclic processes such that ultimately nothing much changes.

Well, nothing much changes on a broad perspective. Locally of course, changes may be substantial: land may become submerged, or islands appear from the sea; mountains or great valleys may appear – albeit very, very slowly. But crust that is subsumed in one place will be balanced by crust formed elsewhere. And – just as walking from one side of a small boat to another will lead to one side rising out of the water, whilst the opposite side sinks deeper into the water – as land is raised in one place it will sink elsewhere.

This is the kind of model that scientists started to develop, and which Prof. Thomson discusses.

"[Dr John Woodward (1665-1728) produced] "an ingenious theory, parts of it quite modern, parts simply seventeenth century sophistry within a Newtonian metaphor. Woodward's earth, post deluge, is stable, but not in fact unchanging. This is possible because it is in a sort of balance – a dynamic balance between opposing forces."

Thomson, 2005: 156

Plus ça change, plus c'est la même chose

James Hutton (1726 – 1797) was one of the champions of this 'uniformitarianism',

"Hutton's earth is in a constant state of flux due to processes acting over millions of years as mountains are eroded by rain and frost. In turn, the steady raising up of mountains, balances their steady reduction through erosion.

…for Hutton the evidence of the rocks demonstrated a cyclic history powered by Newtonian steady-state dynamics: the more it changed, the more it stayed the same."
p.181

Thomson, 2005: 181

The more it changed, the more it stayed the same: plus ça change, plus c'est la même chose. This, of course, is an idiom that has found resonance with many commentators on the social, as well as the physical, world,

"…A change, it had to come
We knew it all along
We were liberated from the fold, that's all
And the world looks just the same
And history ain't changed
'Cause the banners, they all flown in the last war
…
There's nothing in the street
Looks any different to me
And the slogans are effaced, by-the-bye
And the parting on the left
Is now parting on the right
And the beards have all grown longer overnight…"

From the lyrics of 'Won't get fooled again' (The Who song), by Pete Townsend

Steady states

So, there are vast forces acting, but the net effect is a planet which stays substantially the same over long periods of time. Which might be considered analogous to a body which is subject to very large forces, but in such a configuration that they cancel.

Where Prof. Thomson is in danger of misleading his reader is in confusing a static equilibrium and a macroscopic overall steady state that is the result of many compensating disturbances. This is an important difference when we consider energy and not just the forces acting.

A steady state can be maintained by nothing happening, or by several things happening which effectively compensate.

If we consider a very heavy mass sitting on a very study table, then the mass has a large weight, but does not fall because the table exerts a balancing upward reaction force. Although large forces are acting, nothing happens. In physics terms, no work is done. 6

Now consider a sealed cylinder, perfectly insulted and shielded from its surroundings, containing some water, air and too much salt to fully dissolve. It would reach a stead state where the

  • the mass of undissolved salt is constant
  • the height of the solution in the tube is constant

On a macroscopic level, nothing then happens – it is all pretty boring (especially as if the cylinder was perfectly insulated we would not be able to monitor it anyway!)

Actually, all the time,

  1. salt is dissolving
  2. salt is precipitating
  3. gases from the air are dissolving in the solution
  4. gases are leaving the solution
  5. water is evaporating into the air
  6. water vapour is condensing

But the rates of 1 and 2 are the same; the rates of 3 and 4 are the same; and the rates of 5 and 6 are the same. In terms of molecules and ions, there is a lot of activity – but in overall terms, nothing changes: we have a steady state, due to the dynamic equilibria between dissolving and precipitating; between dissolving and degassing; and between evaporation and condensation.

This activity is possible because of the inherent energy of the particles. In the various interactions between these particles a molecule is slowed here, an ion is released from electrical bonds – and so. But no energy transfer takes place to or from the system, it is only constantly redistributed among the ensemble of particles. No work is done.

Cycling is hard work

But macroscopic stable states maintained by cyclic processes are not like that. A key difference is that in the geological cycles there are significant frictional effects. In our sealed cylinder, the processes will continue indefinitely as the energy of the system is constant. In the geological systems, change is only maintained because there is source of power – the sun drives the water cycle, radioactive decay in effect drives the rock cycle.

Work is done in forming new crust under the sea between two plates. More work is done pushing one plate beneath another at a plate boundary. It does not matter if the compensating changes were produced by identical magnitude forces pushing in opposite directions – these are not balanced forces in the sense of cancelling out (they act on different masses of material) – if they had been, nothing would have happened.

You cannot move tectonic plates around without doing a great deal of work – just as you cannot cycle effortlessly by using a circular track that brings you back to where you started, even though when cycling in one direction the ground was pushing you one way, and on the way back the ground was pushing you in the opposite direction! (Your tyres pushed on the track, and as Newton's third law suggests, it pushed back on the tyres in the opposite direction – but those equal forces did not cancel as they were acting on different things: or you would not have moved.)

Perhaps Prof. Thomson understands this, but his language is certainly likely to mislead readers:

"Hooke realised that there was a balance of forces: while the geological strata were being formed and mountains were raised up, at the same time the land was constantly being eroded…"

Thomson, 2005: 179

No, there was not a balance of forces.

It could be that Prof. Thomson's use of the phrase 'balance of forces' is only intended as a metaphor or an analogy. 7 However, he also repeats errors he had made earlier in the book

  • "the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun"
  • "any trajectory other than a straight line must be the result of multiple forces acting together"

which suggests a genuine confusion about how forces act.

One of these mistakes is that planetary orbits (which require a net {unbalanced} force), are due to 'opposing forces',

"…Paley's tortured dancing on the heads of all these metaphysical pins is pre-shadowing of modern ecological thinking and a metaphysical extension of Hooke and Newton's explanation of planetary orbits in terms of opposing forces, or Woodward's theory of matter, or Hutton's geology – it is the living world as a dynamic system of force and counterforce, of checks and balances."
p.242

Thomson, 2005: 242 (my emphasis)

The other was that a single force cannot lead to a curved path,

"…the philosophical concept of reduction, namely that any complex system can be reduced to the operation of simple causes. Thus the parabolic trajectory of a projectile is the product of two straight-line forces acting on each other [sic];…"
p.264

Thomson, 2005: 264 (my emphasis)

Forces are interactions between bodies, they are abstractions and do not act on each other. The parabolic path is due to a single constant force acting on a body that is already moving (but not in the direction of the applied force). It can be seen as the result of the combination of a force (acting according to N2) and the body's existing inertia (i.e., N1). Prof. Thomson seems to be thinking of the motion itself as corresponding to a force, where Newton suggested that it is only a change of motion that corresponds to a force.

However, whilst Prof. Thomson is wrong, he is in good company – as one of the most common alternative conceptions reported is assuming that a moving body must be subject to a force. Which, as I pointed out last time, is not so daft as in everyday experience cars and boats and planes only keep on moving as long as their propulsion systems function (to balance resistive forces); and footballs and cricket balls and javelins that do not have a source of motive power (to overcome resistive forces) soon fall to earth. So, these are understandable and, in one sense, very forgiveable slips. It is just unfortunate they appear in an otherwise informative book about science.

Sources cited:
  • Thomson, K. (2005). The Watch on the Heath: Science and religion before Darwin. HarperCollins.
  • Thomson, W. (1862). On the Age of the Sun's Heat. Macmillan's Magazine, 5, 388-393.
  • Thorn, C. E., & Welford, M. R. (1994). The Equilibrium Concept in Geomorphology. Annals of the Association of American Geographers, 84(4), 666-696. http://www.jstor.org/stable/2564149
Notes

1 Although there are plenty of 'academic' books in many fields of scholarship (usually highly focused so the author is writing about their specialist work), the natural sciences tend to be communicated and debated in research journals. Most books written by scientists tend to be for a more general audience – and publishers expect popular science books to appeal to a wide readership, so these books are likely to have a much broader scope than academic monographs.

2 When he was ennobled, William Thomson chose to be called Baron Kelvin – after his local river, the river Kelvin. So the SI unit of temperature is named, indirectly, after a Scottish River.

Kelvin's reputation was such that when he modelled the cooling earth and suggested the planet was less that a 100 000 000 years old, this caused considerable concerns given that geologists were suggesting that much longer had been needed for it to have reached its present state.

3 For a brief discussion regarding energy changes during processes of this kind, see 'How much damage can eight neutrons do?'

4 The rate of change of momentum is proportional to the magnitude of the applied force and takes place in the direction of the applied force.

As momentum is mv, and as mass is usually assumed fixed (if the motion is well below light speeds) 'the rate of change of momentum' is the mass times the rate of change of the velocity – or ma. (F=ma.)

The key point about direction is that it is not that the body moves in the direction of the force, but the change of momentum (so change of velocity) is in the direction or the force.

As the body's momentum is a vector, and the change in momentum is a vector, the new momentum is the vector sum of these two vectors: new momentum = old momentum + change in momentum.

The object's new direction after being deflected by a force is in the direction of the new momentum

5 When there is force between two bodies (let's call them A, B) the force acting on body B is the same size as the force acting on body A, but is anti-parallel in direction.

The force between the earth and the sun acts on both (not shown to scale)

6 This is an ideal case.

A real table would not be perfectly rigid. A real table would initially distort ever so slightly with the area under the mass being ever so slightly compressed, and the weight dropping to an ever so slightly lower level. The very slight lowering of the weight does a tiny amount of work compressing the table surface.

Then, nothing more happens, and no more work is done.

7 Thorn and Welford (1994) have referred to "the fuzzy and frequently erroneous use of the term…equilibrium in geomorphology" (p.861), and how an 1876 introduction of the "concept of dynamic equilibrium resembles the balance-of-forces equilibrium that appears in dynamics, but by analogy rather than formal derivation" (p.862).

Even Oxbridge professors have misconceptions

Being a science professor is no assurance of understanding Newton's mechanics

Keith S. Taber

…this author had just written that
all matter is in uniform motion unless acted upon by an external force
but did not seem to appreciate that
any matter acted upon by an external force will not be in uniform motion

I started a new book today. 'The Watch on the Heath. Science and Religion before Darwin' had been on my pile of books to read for a while (as one can acquire interesting titles faster than find time to actually read them).

'The Watch on the Heath'

by Prof. Keith Thomson

The title is a reference to the analogy adopted at the start of William Paley's classic book on natural theology. Paley (1802) argued that if one was out walking across a heath and a foot struck an object on the ground, one would make very different assumptions if the object transpired to be a stone or a pocket watch. The stone would pass without much thought – there was no great mystery about how it came to be on the heath. But a pocket watch is an intricate mechanism composed of a multitude of especially shaped and arranged pieces fashioned from different materials. A reasonable person could not think it was an arbitrary and accidentally collated object – rather it clearly had a purpose, and so had a creator – a watchmaker.

 
Paley developed a detailed argument based on the analogy that organisms are like intricate mechanisms that offer obvious evidence of having been designed (Images by  Thomas Wolter and  Gerd Altmann  from Pixabay)

Paley used this as an analogy for the complexity of the living world. Analogies are often used by teachers and science communicators as a means of making the unfamiliar familiar – a way of suggesting something that is being introduced is actually like something the audience already knows about and feels comfortable with.

Read about analogies in science

Paley was doing something a little different – his readers would already know about both watches and living things, and he was developing the analogy to make an argument about the nature of living things as being designed. (Living things would be familiar, but Paley wanted to invite his reader to think about them in a way they might find unfamiliar.) According to this argument, organisms were so complex that, by analogy with a watch, it followed they also were created for a purpose, and by a creator.

Even today, Paley's book is an impressive read. It is 'one long argument' (as Darwin said of his 'Origin of Species') that collates a massive amount of evidence about the seeming design of human anatomy and the living world. Paley was not a scientist in the modern sense, and he was not even a naturalist who collected natural history specimens. He was a priest and philosopher / theologian who clearly thought that publishing his argument was important enough to require him to engage in such extensive scholarship that in places the volume gives the impression of being a medical textbook.

Paley's work was influential and widely read, but when Darwin (1859) presented his own long argument for evolution by natural selection there began to be a coherent alternative explanation for all that intricate complexity. By the mid-twentieth century a neo-Darwinian synthesis (incorporating work initiated by Mendel, developments in statistics, and the advent of molecular biology) made it possible to offer a feasible account that did not need a watch-maker who carefully made his or her creatures directly from a pre-designed pattern. Richard Dawkins perverted Paley's analogy in calling one of his books 'The Blind Watchmaker' reflecting the idea that evolution is little more than the operation of 'blind' chance.

Arguably, Darwin's work did nothing to undermine the possibility of a great cosmic architect and master craft-person having designed the intricacies of the biota – but only showed the subtlety required of such a creator by giving insight into the natural mechanisms set up to slowly bring about the productions. (The real challenge of Darwin's work was that it overturned the idea that there was any absolute distinction between humans and the rest of life on earth – if humans are uniquely in the image of God then how does that work in relation to the gradual transition from pre-human ancestors to the first humans?)

Read 'Intergenerational couplings in the family. A thought experiment about ancestry'

Arguably Darwin said nothing to undermine the omnipotence of God, only the arrogance of one branch of the bush of life (i.e., ours) to want to remake that God in their image. Anyway, there are of course today a range of positions taken on all this, but this was the context for my reading some questionable statements about Newtonian mechanics.

Read about science and religion

Quantum quibbling

My reading went well till I got to p.27. Then I was perturbed. It started with a couple of quibbles. The first was a reference to

"…the modern world of quantum physics, where Einstein's relativity and Heisenberg's uncertainty reign."

Thomson, 2005: 27

"Er, no" I thought. Relativity and quantum theory are not only quite distinct theories, but, famously, the challenge of finding a way to make these two areas of physics, relativity theory and quantum mechanics, consistent is seen as a major challenge. The theories of relativity seem to work really well on the large scale and quantum theory works really well on the smallest scales, but they do not seem to fit together. "Einstein's relativity" is not (yet, at least) found within the "world of quantum physics".

Still, this was perhaps just a rhetorical flourish.

The Newtonian principle of inertia

But later in the same paragraph I read about how,

"Newton…showed that all matter is in uniform motion (constant velocity, including a velocity of zero) unless acted upon by an external force…Newton showed that an object will remain still or continue to move at a constant speed in the same direction unless some external force changes things."

Thomson, 2005: 27

This is known as Newton's first law of motion (or the principle of inertia). Now, being pedantic, I thought that surely Newton did not show this.

It is fair to say, I suggest, that Newton suggested this, proposed it, mooted it; perhaps claimed it was the case; perhaps showed it was part of a self-consistent description – but I am not sure he demonstrated it was so.

Misunderstanding Newton's first law

This is perhaps being picky and, of itself, hardly worth posting about, but this provides important background for what I read a little later (indeed, still in the same paragraph):

"Single forces always act in straight lines, not circles. Any trajectory other than a straight line must be the result of multiple forces acting together."

Thomson, 2005: 27

No!

The first part of this is fair enough – a force acts between two bodies (say the earth and the sun) and is considered to act along a 'line of action' (such as the line between the centres of mass of the earth and the sun). In the Newtonian world-view, the gravitational force between the earth and sun acts on both bodies along that line of action. 1

However, the second sentence ("any trajectory other than a straight line must be the result of multiple forces acting together") is completely wrong.

These two sentences are juxtaposed as though there is a logical link: "Single forces always act in straight lines, not circles. [So therefore] any trajectory other than a straight line must be the result of multiple forces acting together." This only follows if we assume that an object must always be moving in the direction of a force acting on it. But Newton's second law tells us that acceleration (and so the change in velocity) occurs in the direction of the force.

This is confusing the sense of a change with its outcome – a bit like thinking that a 10 m rise in sea level will lead to the sea being 10 m deep, or that if someone 'puts on 20 kilos' they will weigh 200 N. A 'swing to Labour' in an election does not assure Labour of a victory unless the parties were initially on par.

The error here is like assuming that any debit from a bank account must send it overdrawn:
taking £10 from a bank account means there will be £10 less in the account,
but not necessary that the balance becomes -£10!

Changing direction is effortless (if there is an external force acting)

Whenever a single force acts on a moving object where the line of action does not coincide with the object's direction of travel then the object will change direction. (That is, a single force will only not lead to a change of direction in the very special case where the force aligns with or directly against to the direction of travel.) So, electrons in a cathode ray tube can be shown to follow a curved path when a (single) magnetic force is applied, and an arrow shot from a castle battlement horizontally will curve down to the grounds because of the (single) effect of gravitational force. (There are frictional forces acting as well, but they only modify the precise shape of that curve which would still be found if the castle was on a planet with no atmosphere – as long as the archer could hold her breath long enough to get the arrow away.)

The lyrics of a popular song declare "arc of a diver – effortlessly". 2 But diving into a pool is only effortless (once you have pushed off) because the diver is pulled into an arc by their gravitational attraction with the earth – so even if you dive at an angle above the horizontal, a single force is enough to change your direction and bring you down.

"Arc of a diver – effortlessly"

© Pelle Cass. This image is used with kind permission of the artist.

(This amazing artwork is by the photographer Pelle Cass. This is one of a series ('Crowded Fields') that can be viewed at https://pellecass.com/crowded-fields.)

So, there is a mistake in the science here. Either the author has simply made a slip (which can happen to anyone) or he is operating with an alternative conception inconsistent with Newton's laws. The same can presumably be said about any editor or copy editor who checked the manuscript for the publisher.

Read about alternative conceptions

Misunderstanding force and motion

That might not be so unlikely – as force and motion might be considered the prototype case of a science topic where there are common alternative conceptions. I have seen estimates of 80%+ of people having alternative conceptions inconsistent with basic Newtonian physics. After all, in everyday life, you give something a pull or a push, and it usually moves a bit, but then always come to a stop. In our ordinary experience stones, footballs, cricket balls, javelins, paper planes, darts – or anything else we might push or pull – fail to move in a straight line at a constant speed for the rest of eternity.

That does not mean Newton was wrong, but his ideas were revolutionary because he was able to abstract to situations where the usual resistive forces that are not immediately obvious (friction, air resistance, viscosity) might be absent. That is, ideal scenarios that probably never actually occur. (Thus my questioning above whether Newton really 'showed' rather than postulated these principles.)

So, it is not surprising an author might hold a common alternative conception ('misconception') that is widely shared: but the author had written that

  • all matter is in uniform motion unless acted upon by an external force

yet did not seem to appreciate the corollary that

  • any matter acted upon by an external force will not be in uniform motion

So, it seems someone can happily quote Newton's laws of motion but still find them so counter-intuitive that they do not apply them in their thinking. Again, this reflects research which has shown that graduates who have studied physics and done well in the examinations can still show alternative conceptions when asked questions outside the formal classroom setting. It is as if they learn the formalism for the exams, but never really believe it (as, after all, real life constantly shows us otherwise).

So, this is all understandable, but it seems unfortunate in a science book that is seeking to explain the science to readers. At this point I decided to remind myself who had written the book.

We all have alternative conceptions

Keith Thomson is a retired academic, an Emeritus Fellow at Kellog College Oxford, having had an impressive career including having been a Professor of Biology at Yale University and later Director of the Oxford University Museum and Professor of Natural History. So, here we have a highly successful academic scientist (not just a lecturer in some obscure university somewhere – a professor at both Yale and Oxford), albeit with expertise in the life sciences, who seems to misunderstand the basic laws of physics that Newton postulated back in 1687.

Prof. Thomson seems to have flaws in his knowledge in this area, yet is confident enough of his own understanding to expose his thinking in writing a science book. This, again, is what we often find in science teaching – students who hold alternative conceptions may think they understand what they have been taught even though their thinking is not consistent with the scientific accounts. (This is probably true of all of us to some degree. I am sure there must be areas of science where I am confident in my understanding, but where that confidence is misplaced. I likely have misconceptions in topics areas where Prof. Thomson has great expertise.)

A balance of forces?

This could have been just a careless slip (of the kind which once made often looks just right when we reread our work multiple times – I know this can happen). But, over the page, I read:

"…in addition to the technical importance of Newton's mathematics, the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun, quickly became a valuable metaphor…"

Thomson, 2005: 27

Again – No!

If there is 'balance of forces' then the forces effectively cancel, and there is no net force. So, as "all matter is in uniform motion (constant velocity, including a velocity of zero) unless acted upon by an external force", a body subject to a balance of forces continues in "uniform motion (constant velocity…)" – that is, it continues in a straight line at a constant speed. It does not circle (or move in an ellipse). 3

Again, this seems to be an area where people commonly misunderstand Newton's principles, and operate with alternative conceptions. Learners often think that Newton's third law (sometimes phrased in terms of 'equal and opposite forces') implies there will always be balanced forces!

Read about learning difficulties and Newton's third law

The reason the moon orbits the earth, and the reason the earth orbits the sun, in the Newtonian world-view is because in each case the orbiting body is subject to a single force which is NOT balanced by any countering force. As the object is "acted upon by an external force" (which is not balanced by any other force) it does not move "in uniform motion" but constantly changes direction – along its curved orbit. According to Newton's law of motion, one thing we can always know about a body with changing motion (such as one orbiting another body) is that the forces on it are not balanced.

But once circular motion was assumed as being the 'natural' state of affairs for heavenly bodies, and I know from my own teaching experience that students who understand Newtonian principle in the context of linear motion can still struggle to apply this to circular motion. 4

Two conceptions of orbital motion (one canonical, the other a misconception commonly offered by students). From Taber, K. S., & Brock, R. (2018). A study to explore the potential of designing teaching activities to scaffold learning: understanding circular motion.

I even developed a scaffolding tool to help students make this transition, by helping them work through an example in very simple steps, but which on testing had modest effect – that is, it seemed to considerably help some students apply Newton's laws to orbital motion, but could not bridge that transition for others (Taber & Brock, 2018). I concluded even more basic step-wise support must be needed by many learners. Circular motion being linked to a net (unbalanced) centripetal force seems to be very counter-intuitive to many people.

To balance or not to balance

The suggestion that a balance of forces leads to change occurs again a little later in the book, in reference to James Hutton's geology,

"…Hutton supported his new ideas both with solid empirical evidence and an underlying theory based on a Newtonian balance of forces. He saw a pattern in the history of the rocks: gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again."

Thomson, 2005: 39

A balance of forces would not lead to rocks being "gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again". Indeed if all the relevant forces were balanced there would be no erosion, washing, sedimentation, or raising.

Erosion, washing, sedimentation, raising up ALL require an imbalance of forces, that is, a net force to bring about a change. 5

Reading on…

This is not going to stop me persevering with reading the book*, but one can begin to lose confidence in a text in situations such as these. If you know the author is wrong on some points that you already know about, how can you be confident of their accounts of other topics that you are hoping to learn about?

Still, Prof. Thomson seems to be wrong about something that the majority of people tend to get wrong, often even after having studied the topic – so, perhaps this says more about the hold of common intuitive conceptions of motion than the quality of Prof. Thomson's scholarship. Just like many physics learners – he has learnt Newton's laws, but just does not seem to find them credible.

Sources cited:
  • Darwin, C. (1859). The Origin of Species by Means of Natural Selection, or the preservation of favoured races in the struggle for life. John Murray.
  • Dawkins, R. (1988). The Blind Watchmaker. Penguin Books.
  • Paley, W. (1802/2006). Natural Theology: Or Evidence of the Existence and Attributes of the Deity, Collected from the Appearances of Nature (M. D. Eddy & D. Knight, Eds.). Oxford University Press.
  • Rosen, E. (1965/1995) Copernicus on the phases and the light of the planets, in Rosen, E. (1995). Copernicus and his successors (E. Hilfstein, Ed.). The Hambledon Press.
  • Taber, K. S., & Brock, R. (2018). A study to explore the potential of designing teaching activities to scaffold learning: understanding circular motion. In M. Abend (Ed.), Effective Teaching and Learning: Perspectives, strategies and implementation (pp. 45-85). New York: Nova Science Publishers. [Read the author's manuscript version]
  • Thomson, K. (2005). The Watch on the Heath: Science and religion before Darwin. HarperCollins.
  • Watts, M. and Taber, K. S. (1996) An explanatory gestalt of essence: students' conceptions of the 'natural' in physical phenomena, International Journal of Science Education, 18 (8), pp.939-954.
Notes

1 Though not in the world-view offered by general relativity where the mass of the sun distorts space-time enough for the earth to orbit.

2 The title track from Steve Winwood's 1980 solo album 'Arc of a Diver'

3 We have known since Kepler that the planets orbit the sun following ellipses (to a first order of approximation*), not perfect circles – but this does not change the fundamental point here: moving in an ellipse involves continuous changes of velocity. (* i.e., ignoring the perturbations due to the {much smaller} forces between the orbiting bodies.**)

[Added, 20220711]: these perturbations are very small compared with the main sun-planet interactions, but they can still be significant in other ways:

"…the single most spectacular achievement in the long history of computational astronomy, namely, the discovery of the planet Neptune through the perturbations which it produced in the motion of Uranus."

Rosen, 1965/1995, p.81

4 What is judged as 'natural' is often considered by people as not needing any further explanation (Watts and Taber, 1996).

5 This reference to Hutton's ideas seems to preview a more detailed treatment of the new geology in a later chapter in the book (that I have not yet reached), so perhaps as I read on I will find a clearer explanation of what is meant by these changes being based on a theory of balance of forces.* Still, the impression given in the extract quoted is that, as with orbits, a balance of forces brings about change.

* Addendum: I have now read on, see: 'Plus ça change – balancing forces is hard work'

Counting both the bright and the very dim

What is 1% of a very large, unknown, number?

Keith S. Taber

1, skip 99; 2, skip 99; 3, skip 99; 4,… skip 99, 1 000 000 000!
(Image by FelixMittermeier from Pixabay)

How can we count the number of stars in the galaxy?

On the BBC radio programme 'More or Less' it was mooted that there might be one hundred billion (100 000 000 000) stars in our own Milky Way Galaxy (and that this might be a considerable underestimate).

The estimate was suggested by Prof. Catherine Heymans who is
the Astronomer Royal for Scotland and Professor of Astrophysics at the University of Edinburgh.

Programme presenter Tim Harford was tackling a question sent in by a young listener (who is very almost four years of age) about whether there are more bees in the world than stars in the galaxy? (Spoiler alert: Prof. Catherine Heymans confessed to knowing less about bees than stars.)

An episode of 'More or Less' asks: Are there more bees in the world or stars in the galaxy?

Hatford asked how the 100 billion stars figure was arrived at:

"have we counted them, or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"

The last suggestion here is of course the basis for many surveys. As long as there is good reason to think a sample is representative of the wider population it is drawn from we can collect data from the sample and make inferences about the population at large.

Read about sampling a population

So, if we counted all the detectable stars in a typical 1% of the sky and then multiplied the count by 100 we would get an approximation to the total number of detectable stars in the whole sky. That would be a reasonable method to find approximately how many stars there are in the galaxy, as long as we thought all the detected stars were in our galaxy and that all the stars in our galaxy were detectable.

Prof. Heymans replied

"So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out 1% of all the stars in our Milky Way galaxy, creating a three dimensional map. So, that's looking at 1 billion of the stars, and then to get an idea of how many others are there we look at how bright all the stars are, and we use our sort of models of how different types of stars live [sic] in our Milky Way galaxy to give us that estimate of how many stars are there."

Prof. Catherine Heymans interviewed on 'More or Less'

A tautology?

This seemed to beg a question: how can we know we are mapping 1% of stars, before we know how many stars there are?

This has the appearance of a tautology – a circular argument.

Read about tautology

To count the number of stars in the galaxy,
  • (i) count 1% of them, and then
  • (ii) multiply by 100.

So,

  • If we assume there are one hundred billion, then we need to
  • count one billion, and then
  • multiply by 100 to give…
  • one hundred billion.

Clearly that did not seem right. I am fairly sure that was not what Prof. Haymans meant. As this was a radio programme, the interview was presumably edited to fit within the limited time allocated for this item, so a listener can never be sure that a question and (apparently immediately direct) response that makes the edit fully reflects the original conversation.

Counting the bright ones

According to the website of the Gaia mission, "Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye)." Hartman's suggestion that "you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?" seems very reasonable, until you realise that even with a powerful telescope sent outside of the earth's atmosphere, many of the stars in the galaxy may simply not be detectable. So, what we see cannot be considered to be fully representative of what is out there.

It is not then that the scientists have deliberately sampled 1%, but rather they are investigating EVERY star with an apparent brightness above a certain critical cut off. Whether a star makes the cut, depends on such factors as how bright it is (in absolute terms – which we might imagine we would measure from a standard distance 1) and how close it is, as well as whether the line of sight involves the starlight passing through interstellar dust that absorbs some (or all) of the radiation.

Of course, these are all strictly, largely, unknowns. Astrophysics relies a good on boot-strapping, where our best, but still developing, understanding of one feature is used to build models of other features. In such circumstances, observational tests of predictions from theory are often as much testing the underlying foundations upon which a model used to generate a prediction is built as that specific focal model itself. Knowledge moves on incrementally as adjustments are made to different aspects of interacting models.

Observations are theory-dependent

So, this is, in a sense, a circular process, but it is a virtuous circle rather than just a tautology as there are opportunities for correcting and improving the theoretical framework.

In a sense, what I have described here is true of science more generally, and so when an experiment fails to produce a result predicted by a new theory, it is generally possible to seek to 'save' the theory by suggesting the problem was (if not a human error) not in the actual theory being tested, but in some other part of the more extended theoretical network – such as the theory underpinning the apparatus used to collect data or the the theory behind the analysis used to treat data.

In most mature fields, however, these more foundational features are generally considered to be sound and unlikely to need modifying – so, a scientist who explains that their experiment did not produce the expected answer because electron microscopes or mass spectrometers or Fourier transform analyses do not work they way everyone has for decades thought they did would need to offer a very persuasive case.

However, compared to many other fields, astrophysics has much less direct access to the phenomena it studies (which are often vast in terms of absolute size, distance and duration), and largely relies on observing without being able to manipulate the phenomena, so understandably faces special challenges.

Why we need a theoretical model to finish the count

Researchers can use our best current theories to build a picture of how what we see relates to what is 'out there' given our best interpretations of existing observations. This is why the modelling that Prof. Heymans refers to is so important. Our current best theories tell us that the absolute brightness of stars (which is a key factor in deciding whether they will be detected in a sky survey) depends on their mass, and the stage of their 'evolution'.2

So, completing the count needs a model which allows data for detectable stars to be extrapolated, bearing in mind our best current understanding about the variations in frequencies of different kinds (age, size) of star, how stellar 'densities' vary in different regions of a spiral galaxy like ours, the distribution of dust clouds, and so forth.

…keep in mind we are off-centre, and then allow for the thinning out near the edges, remember there might be a supermassive black hole blocking our view through the centre, take into account dust, acknowledge dwarf stars tend to be missed, take into account that the most massive stars will have long ceased shining, then take away the number you first thought of, and add a bit for luck… (Image by WikiImages from Pixabay)

I have taken the liberty of offering an edited exchange

Hartford: "have we counted [the hundred billion stars], or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"

Heymans "So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out…all the stars in our Milky Way galaxy [that are at least magnitude 20 in brightness], creating a three dimensional map. So, that's looking at 1 billion of the [brightest] stars [as seen from our solar system], and then to get an idea of how many others are there we look at how bright all the stars are, and we use our models of how different types of stars [change over time 2] in our Milky Way galaxy to give us that estimate of how many stars are there."

No more tautology. But some very clever and challenging science.

(And are there more bees in the world or stars in the galaxy? The programme is available at https://www.bbc.co.uk/sounds/play/m00187wq.)

Note:

1 This issue of what we mean by the brightness of a star also arose in a recent post: Baking fresh electrons for the science doughnut

2 Stars are not alive, but it is common to talk about their 'life-cycles' and 'births' and 'deaths' as stars can change considerably (in brightness, colour, size) as the nuclear reactions at their core change over time once the hydrogen has all been reacted in fusion reactions.