Should we legislate against actions and reactions in introductory physics?
Keith S. Taber
Even apparently authoritative sources can sometimes encourage alternative conceptions (misconceptions). I've recently been reading entries in John Gribbin's 'Companion to the Cosmos'. This 'Companion' is a large book styled as a reference book – like a dictionary or encyclopaedia in that it is a series of entries arranged alphabetically – so, something that presents as an authoritative source. That may not sound like a good read, but (even though is is now quite dated, being published in 1996) actually it contains a lot of really fascinating material. I have come across a good deal of intriguing and interesting detail in its pages.
John Gribbin's 'Campanion to the Cosmos': a worthy companion
I did not expect to learn anything new from the entry on 'Newton's laws of motion', but I did find something to take note of. The statement of the third law was presented as follows:
"Whenever a force (or, as Newton put it, an action) is applied to an object, the object pushes back with an equal and opposite reaction. So, for example, gravity pulls me downwards with a force equal to my weight, and the chair I am sitting on pushes back with an equal and opposite reaction, leaving me sitting still, not accelerating downwards (as I would if there were no intervening chair or floor) to the centre of the Earth. And while gravity pulls me towards the centre of the Earth, the mass of my body is pulling the Earth towards me with an equal force."
Gribbin's presentation of Newton's Third Law
Now if I had been an editor asked to comment on this I would have suggested some deletions to give a much more focused treatment:
"Whenever a force (or, as Newton put it, an action) is applied to an object, the object pushes back with an equal and opposite reaction. So, for example, gravity pulls me downwards with a force equal to my weight…and while gravity pulls me towards the centre of the Earth, the mass of my body is pulling the Earth towards me with an equal force."
An edited version of Gribbin's account less likely to confuse a novice?
I am not sure I like the 'mass' doing the pulling, rather than perhaps the 'matter' of my body. But this edited version does seem to reflect the law: Gribbin's body is pulled towards the centre of the earth and also pulls the earth with an equal force. Two bodies, Gribbin's and the earth, are attracted towards each other, and the same magnitude of forces acts on both. Gribbin is pulled towards the earth with a force of perhaps 700N in which case the earth is also being pulled with a force of 700N towards Gribbin.
Action and delayed reaction?
But I think the terms 'action' and 'reaction' are unhelpful as it suggests a sequence of actions: A attracts (or repels) B, and in response, B then attracts (or repels A). But it is more helpful to think not of a pair of forces, but rather as a force as being something (singular) which acts between (and so on) two bodies – such as an attractive force between John Gribbin and planet Earth.
A common misconception
There are a number of common alternative conceptions concerning the area of forces, acceleration and motion that Newton's laws of motion describe. One of these common 'misconceptions' involves misidentifying the 'action' – 'reaction' pair as both acting on the same body, and determining that because the forces are 'opposite and equal' they must cancel.
Not an example of action and reaction. (Apple Image by Rosy / Bad Homburg / Germany from Pixabay)
So, for example, consider an apple hanging securely from a tree (as Newton once did). There is a downwards force on the apple (due to its weight) but it does not fall as there is also a balancing upwards force provided by the stem (stalk) from which the apple hangs. This is a fair description, BUT this does not describe the so-called 'action' and 'reaction' of Newton's third law. If it did, and we generalised this, we would end up with a situation where we ascribe balanced forces to every body (as there must always be an equal and opposite force acting, Newton said so). This would mean no acceleration.
In that universe (assuming Newton's first law still applied), every stationary body must remain stationary, and every moving body must continue to move in the same direction at the same speed. That would not be a very interesting universe. It would be a universe with no need for Newton's second law which tells us how a body is accelerated under net forces, as there would be no net forces if every force was balanced by its reaction! If that universe exists, it is not our universe.
Formulations of the law
The more wordy "if [or perhaps,'whenever'is better] a body A exerts a force on a body B, then body B exerts a force on body A that is equal in magnitude and opposite in direction" is perhaps more difficult for some learners to unpick – but has the advantage of making it clear the force[s] act[s] on two different bodies. If the apple is pulled down by the earth, then the earth is pulled up by the apple. Simultaneously: While the apple is pulled down by the earth, the earth is pulled up by the apple.
I think from the teaching perspective I would prefer a law definition something like 'A force is an interaction between two bodies and always acts on both with equal magnitude (along a line joining the centres of the bodies)'. Perhaps there is some good reason we do not always teach it that way, but I suspect it is more a matter of Newton's first law (of teaching) acting – that is, inertia. The terms 'action' and 'reaction' have become established. And perhaps by deference to Newton (who like everyone else had to come to terms with his own laws: having previously suggested that, as it was moving around the sun rather than being attracted into it, a comet may be directed by magnetism as well as being attracted to the Sun).
The apple is not falling (and the earth is not rising – though to be fair it is rather hard to notice the earth rising even when the apple does fall *) so the forces on the apple are balanced – but these are not an 'action-reaction' pair. Rather we have a pair of such 'pairs' ,and we are equating across these pairs. (This is much mote obvious if we avoid talk of 'reactions' and 'action-reaction' pairs and just define a force as acting between two different bodies as then two forces acting on the same body should not get confused in this way – as Newton's third law refers and applies separately to each individual interaction/force).
Forces always act between two different bodies (Apple image by Rosy / Bad Homburg / Germany from Pixabay)
The apple hangs form the branch by a connecting stem (also known as the stalk). The apple pulls down on the stem with the same magnitude force that the stem pulls the apple up (Newton's third law), and the earth pulls down on the apple with the same force as the apple pulls up on the earth (Newton's third law); AND as the full weight of the apple is supported by the stem – as it is robust enough: not due to Newton's third law but simply as a fact about the tree structure at this point in time – and so the stem is pulling up with a force that happens to be equivalent to the apple's weight . This means there is no net force on the apple, and so it goes nowhere (Newton's first law).
But one day the stem, the apple's connection to the branch, will have changed such that it can no longer support the weight of the apple and the apple will fall; while Newton's third law continues to apply to the apple, the earth, the tree, and everything else. An area of the stem called the abscission zone becomes changed by the changing pattern of plant hormones triggered by the environment such that the cells in this part of the stem become less strongly adhered together. (Crudely, the tree physiology includes a system which dissolves the 'glue' holding cells together in this region of the stalk once the fruit has matured.)
For a moment the stem will be pulling up on the apple, but now with a force less than the apple's weight. (And by Newton's third law, at that moment the apple will be pulling the stem with an equal force that is somewhat less than its weight.) The apple's weight has not changed, and so the force between the apple and and earth is still the same – and the net force on the apple is no longer balanced, so it starts to accelerate towards the ground in the manner that Newton noticed.
A tree branch is subjected to an incidental momentary contingency (Image by PDPhotos from Pixabay)
In the simplified case, we can imagine the stem slowly changing, and its tensile strength very gradually diminishing from a value more than sufficient to support the apple to reaching a critical point where it just drops below what can support the weight of the apple – at which point the stem structure fails, and the apple falls. Realistically, this 'ideal' scenario is unlikely, as winds (as well as birds, squirrels and naughty children) lead to branches moving about, such that the fruit is subject to various forces – so the stalk will likely reach breaking point earlier, when subject to the apple's weight plus some additional stress due to some incidental momentary contingency. But the principle is sound even if the actual situation is likely more complex because the apple may well fall during a dynamic episode rather than when hanging in an equilibrium state. When the stem cannot support the apple, it will fall.
A misleading account?
The point is that Newton' third law is very simple, but it is easily (and often) misunderstood and misapplied. So, as I started to read Gribbin's presentation of the law, I though 'whoa (or something equivalent), that's not right!'
"Whenever a force (or, as Newton put it, an action) is applied to an object, the object pushes back with an equal and opposite reaction. So, for example, gravity pulls me downwards with a force equal to my weight, and the chair I am sitting on pushes back with an equal and opposite reaction, leaving me sitting still, not accelerating downwards (as I would if there were no intervening chair or floor) to the centre of the Earth."
The initial section of Gribbin's presentation.
I think Gribbin is meaning that "[as (i)] gravity pulls me downwards with a force equal to my weight, and [ii] the chair I am sitting on [because it is therefore subject to a downwards force from my weight] pushes back with an equal and opposite reaction." At least, that is how I think we need to read this according to physics.
The third law force here is between the chair (pushing upwards on Gribbin) and Gribbin (pushing down on the chair), and this is fine. But my initial reading assumed the intended pairing was between the downward force on Gribbin due to gravity and the upward ('normal') force from the chair. I am sure Gribbin understood this basic physics, but I thought his wording is unhelpful, as he seems to be referring to two forces acting on the same body:
"Whenever a force (or, as Newton put it, an action) is applied to an object, the object pushes back with an equal and opposite reaction. So, for example, gravity pulls me downwards …and the chair I am sitting on pushes back [on me]…"
A misreading of Newton's third law
Moreover, the reference to not accelerating relies on another pair of balanced forces not mentioned in the presentation. For "the chair I am sitting on pushes back with an equal and opposite reaction" only because it is also supported by the ground. Gribbin refers to the floor, and the chair is only able to support him because it is supported by the floor. And that is because it is robust enough to push upwards on a chair with a force that balances the weight of {Gribbin + his chair}. So there are three distinct action-reaction pairs (or if you prefer, simply forces) acting: Gribbin-earth; Gribbin-chair; chair-floor, and Gribbin does not accelerate due his weight because {the floor pushes up on the chair} AND so {the chair pushes up on him}.
Perhaps you might argue that we have to also consider how the floor is supported by the building foundations and those foundations by the ground below…before we can explain why the earth is pulling on Gribbin without him accelerating? But my point is that in introducing Newton's third law, it might be better to focus on one interaction rather than complicate the scenario. Newton's third law tells us that if Gribbin is seated then the chair pushes up on Gribbin as he pushes down in it, but it does not (of itself) – as might seem to be implied by the text – tell us why he is able to sit on the chair or why the chair does not fall through the floor .
Seeing the science at the resolution of the learner
As is often the case, someone who already knows the science can interpret the text in an orthodox way (I wonder how often examiners give the benefit of the doubt to misconceived explanations?) – but if the point is to communicate an idea to someone who has not yet mastered it, then avoiding potentially confusing complications may be the best strategy.
Yes, I am being pedantic about wording, but with reason. We know learners commonly misidentify where the 'action' and 'reaction' are acting, and so come to explain balanced forces as necessarily due to Newton's third law. The law actually tells us that a force always acts (with equal magnitude, if not always equal effect) on a pair of bodies – so can neverdirectly be a valid explanation for why the forces on any single body are balanced. Teachers and authors need to be very careful in their phrasing if they are not to encourage learners to acquire alternative conceptions that many will find convincing, and, indeed, to reinforce such misconceptions where they are already in place.
* That is a whole other common misconception, not distinguishing the force itself from the effect produced – so another common alternative conception is that the larger earth must attract the moon more than the little moon attracts the earth, and the atomic nucleus must (except in hydrogen) attract an electron more than the electron attracts the nucleus.
But, actually, no, the wind-shield experienced just as much force as fly on the wind-shield – but the effect is usually more critical for the poor fly. This is worth thinking about when considering how some footballers respond to tackles: in any interaction both players experience exactly the same force of impact! Of course, the same force can do different levels of damage depending upon where it is applied and at what angle, but it is still interesting just how often one player is floored and pole-axed by another who seems barely to notice any contact.
Me ref? I hardly touched him.
The same force acts on both players – in that respect (if not in terms of who might be fouling) it is irrelevant who initiates contact (Image from Pixabay)
Work cited:
John Gribbin (1996) Companion to the Cosmos. London: Weidenfeld & Nicolson
It is something of a cliché, so it was not the phrase itself ("…that's my theory anyway and I'm sticking to it") that caught my attention, but that I heard it used by a scientist.
why, when I put a duvet cover in the washing machine with other items, they all end up inside the duvet cover when the programme finishes
Now this is a phenomenon I have observed myself, and I was not sure of the explanation. As it happened, Dr Sarchet had also wondered about this, indeed she had apparently "thought about this on a weekly basis for as long as I can remember", and had a – well let me say for the moment – suggestion.
"what might be going on here is, obviously when you've got a duvet cover and if you have not sort of buttoned it up before putting it in the wash, you've got a very wide opening, so that's easy statistically for things to enter it, and then as it twists around in the wash, it's actually harder to leave. So, what you've got is kind of a difficulty gradient, things are more likely to go in than they are to come out; and my reckoning is if that keeps happening for a long enough period, enough cycles, eventually everything ends up inside."
Now, I tried to visualise this, and was not convinced. In my mental simulation, the configuration of the duvet cover is such that:
initially, ingress and egress are both readily possible; then,
as twisting begins, possible but less readily; then,
when the duvet becomes very twisted, both ingress and egress are blocked.
There seems to be a 'difficulty gradient' over time, but in my mind this seemed symmetrical in relation to the direction of passage – moving in and out of the duvet cover. Perhaps some items will enter the duvet before the passage is closed – but why should this be all of them, if items can leave as well as enter up to that point?
I am not sure I am right here because I might just be lacking sufficient creative simulation capacity (imagination), or I may not have fully appreciated the mechanism being suggested. After all, a communicator has a meaning in mind, but the text produced (what they say or write, etc.) only represents that meaning and does not inherently contain it. It is up to the audience to make good sense of it. Perhaps I failed. After all, the phenomenon seems to be a real one, so something is going on.
An insight (Image of woman with washing by Amine Tadri, Image of lamp by GraphicsSC from Pixabay)
Analogy in scientific discovery
But what intrigued me about the suggestion was less its veracity, but rather two features of how it was presented. As my heading suggests, Dr Sarchet closed here proposal with the statement that "that's my theory anyway and I'm sticking to it". She prefaced her proposal by reporting on its origin:
"I'd like to argue this might be a little bit like cell biology…"
Dr Sarchet is a biologist, with her doctorate in development genetics, and I thought it was interesting that she was making sense of washing dynamics in terms of cells. Interesting, but not strange: we all seek to make sense of things, and to do so we draw on the range of interpretive resources we have available – the knowledge and understanding, language, images, experiences, and so forth that we carry around represented in our heads. That a biologist might derive a suggestion from a biological source therefore seems quite natural.
Moreover, the process operating is one that is common in science itself. The process I refer to is that of analogy,
"the reason I kind of try to claim that's like cell biology is sometimes, certain substance, it is much easier for them to get into the cell, through the cell membrane because of the way it is made than it is for them to randomly diffuse out again. And that's a really sort of clever, not kind of actively driven way, of creating order"
I have written a lot about analogy on this site, but mostly in relation to science teaching and science communication more widely. That is, how teachers 'make the unfamiliar familiar' by suggesting that some abstract notion to be learnt is actually, in some way, just like something the learners are already familiar and quite comfortable with – it is like a ladder, or the high jump, or the way people arrange themselves sitting on a bus, or like water passing through a drain hole, or whatever.
However analogy is also actually used within scientific practice itself, in the discovery process. Perhaps we should not be surprised then that analogies are often found when scientists talk or write about their work, as well as commonly being used by journalists and authors of popular science books.
Many examples of science analogies are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
Sometimes the use of analogy within science itself may be making such small jumps that we may not notice analogy is being used:
Element X is in the same group of the periodic table as element Y, and element Y forms a compound with element A with the properties I am interested in, so I wonder if element X also forms a compound with element A with those properties?
Sometimes however, the jumps are across topics or even sciences.
Does this strange new property of the atomic nucleus suggest the nucleus can behave a bit like a drop of liquid; and, if so, can ideas from the physics of fluids be useful in this different area of nuclear physics?
In this way, the recognition of a potential analogy suggests conjectures that can be tested. Use of such analogies is therefore part of the creative aspect of science.
Perhaps the ultimate use of analogy occurs in physics where equations are found to transfer from one context to another with the right substitutions (e.g., 'it's a wave phenomenon, so we can apply this set of equations that work for all wave phenomena'). As learners will find if they continue with physics as an elective school subject:
We have an equation for the flow of charge in an electrical conductor, and fluid flows, so the same basic equation could work there. And we talk of heat flow, so we should be able to adopt the same basic equation…
I once designed a teaching activity for upper secondary learners (Taber, 2011a) based about the ways certain phenomena are analogous in the sense of following exponential decays (e.g., capacity discharge, radioactive decay, cooling…). For learners not yet introduced to the exponential decay equation this analogy can be built upon the common feature of a negative feedback loop where the magnitude of a driver (excess temperature, radioactive material, p.d.) is reduced by the effect it drives (heat, radioactivity, current);
An exponential decay occurs when a negative feedback loop operates.
In capacitor discharge, A could be p.d. across capacitor, and B current (+ indicates the more p.d. across the plates, the more current flows; – indicates the more current flows {removing charge from the plates}, the lower the p.d. across the plates).
As p.d. falls, the current falls (and so the rate of drop of charge across plates fall) and so the rate of p.d. dropping also falls. …
Similar arguments apply to radioactivity and amount of radioactive material; and cooling and excess temperature.
Progress in science relies on empirical studies to test ideas: but empirical tests can only be carried out afteran act of creative imagination has produced a hypothesis to test. Because science is rightly seen as rational and logical, we can easily lose sight of the creative aspect:
"Creativity is certainly a central part of science, and indeed part of the expectation of the major qualification for any researcher, the Ph.D. degree, is that work should be original. Originality in this context, means offering something that is new to the literature in the field concerned. The originality may be of various kinds: applying existing ideas in a novel context; developing new instrumentation or analytical techniques; offering a new synthesis of disparate literature and so forth. However, the key is there needs to be some novelty. Arthur Koestler argued that science, art, and humour, all relied on the same creative processes of bringing together previously unrelated ideas into a new juxtaposition."
Science teaching needs to reflect how science is creative and so open to speculative divergent thought (as well as being logical and needing disciplined convergent thinking!)
"Science teachers need to celebrate the creative aspects of science – the context of discovery. They should emphasise
how scientific models are thinking tools created by scientists for exploring our understanding of phenomena;
how teaching models are speculative attempts to 'make the unfamiliar familiar' by suggesting that 'in some ways it's a bit like something you already know about'; and in particular
how scientists always have to trust imagination as a source of ideas that may lead to discovery.
However, it is equally important that the creative act is always tempered by critical reflection. Scientific models have limitations; teaching models and analogies may be misleading; and all of us have to select carefully from among the many imaginative possibilities we can generate if we seek ideas that help us understand rather than just fantasise."
But the other point I noted, which I raised at the beginning of this piece, was how Dr Sarchet signed off "…that's my theory anyway and I'm sticking to it" which from a scientific perspective seemed problematic at two levels.
I am not being critical of Dr Sarchet as she was just using a chiché in a humorous vein, and I am sure was not expecting to be taken seriously. Other scientists listening to the programme will have surely realised that. I am not so sure if lay people, or school age learners, will have picked up on the humour though.
As a scientist, Dr Sarchet would, I am sure, acknowledge the provisional nature of scientific knowledge: all our theories are open to being replaced if new evidence or new ways of understanding the evidence suggest they are inadequate. Scientists, being human, do get attached to their 'pet' theories, but a good scientist should be prepared to give up an idea and move on when this is indicated. Scientists should not 'stick to' a theory come what may. Just as well, or we would still be operating with phlogiston, caloric and the aether.
But in any case, I am not convinced that Dr Sarchet had a theory here. A theory is more than an isolated idea – a theory is usually more extensive, a framework connecting related concepts, perhaps encompassing one or more empiricalgeneralisations (laws), and being supported by a body of evidence.
What Dr Sarchet had was a conjecture or hypothesis that she had not yet tested. Certainly having a testable hypothesis is an important starting point for developing a theory – but it is not sufficient.
The hypothesis of continental drift was proposed decades before sufficient investigations and evidence led to the modern theory of tectonics. This is the general situation: the hypothesis or conjecture is a critical step, but by itself does not lead to new knowledge.
Common conceptions of scientific theories
I do not imagine Dr Sarchet really considered her suggestion had reached theory status either. Again, she was just using a common expression. But this is just one example of how words that have precise technical meanings in science (element, energy, force, momentum, plant, substance…) are used with more flexible and fluid meanings in everyday life.
For most people, a 'theory' (let me denote this theorylifeworld to mean how the word is used in everyday discourse) is nothing special – we all have theorieslifeworld all the time. Perhaps a theorylifeworld that a particular football team will win on Saturday, or that next door's cat hates you, or that they are putting less biscuits in these packets than they used to. A theorylifeworld can be produced with little effort, held with various degrees of commitment (often quickly forgotten when experience does not fit, but sometimes 'stuck to' regardless!) and often abandoned with little cost.
Now scientific theories are not like that. In one curriculum context, theoriesscience were defined as 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world'. But, if learners come to class having long heard and used the term 'theory' with its 'lifeworld' (that is, everyday, informal) meaning then they think they already know what a theory is (and it is not a consistent, comprehensive, coherent and extensively evidenced source of explanations of aspects of the natural world!)
This is not just speculation, as studies have asked school age learners how they understand such terms. One study, undertaken in that curriculum context that suggested theories are 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world' found most respondents had quite a different idea (Taber, et al., 2015). They generally saw a theory as something a scientist made up effortlessly (almost on a whim). Accordingly, they did not think that theories had a very high status – as they had not yet been tested in any way. Once tested, any 'theory' that passed the test ceased to be a theory – perhaps becoming a law: something seen as proven and having (unlike the theory) high epistemological status.
This common pattern is caricatured in the figure:
From Taber et al., 2015
So, laws were seen as of higher status than theories. Laws were proven and so not open to questioning (that is, their conjectural nature as generalisations that could never be proven were not recognised), whereas theories were little more than the romanced flotsam and jetsam of someone's imagination.
It is just a theory
Now of course, I am generalising here from a small sample (of 13-14 year olds learners from a few schools in one country) and individual learners have their own nuanced understandings – aligned to the curriculum account to different degrees.
One interviewed learner confused theories with theorems from mathematics . But, as a generalisation, the learners interviewed tended to see a theory much more as a hypotheses or conjecture than as a worked through conceptual framework of related ideas that are usually supported by a range of evidence, often collected by deliberate testing.
This is useful for the teacher to bear in mind as clearly when the teacher refers to theory, the learners will often understand this as something quite different from what was intended. Probably the only response to this is to review the intended meaning of 'scientific theory' each time one is discussed. Learners can overcome their alternative conceptions with sufficient support and engagement, but the teacher has to work hard when the existing idea is not only long-established but also being reinforced by everyday discourse (and scientists in the media such as Dr Sarchet shifting to the vernacular, as non-scientists may not recognise the transition from a technical to an everyday code).
So, for example , the theory of natural selection (or general relativity if you prefer), is not proven because in science we can never prove general ideas, and so it is just a theory. But theories are all we are ever going to get in science (for certainties look elsewhere), and some of them are so well tested and supported that in practice we treat them as secure and almost as if certain knowledge.
Perhaps it does not matter enormously if many learners leave school thinking general relativity is only a theorylifeworld. Perhaps it does not even matter that much for many learners if they leave school thinking natural selection is only a theorylifeworld. But when people dismiss climate change or the basis of vaccination as 'just a theory' this is much more problematic, as it invites an attitude that these 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world' are of no more merit than your neighbour's 'theory' about the next set of winning lottery numbers or a politician's 'theory' about the merits of high import tariffs for reducing the price of eggs. And that is a problem, as climate change and vaccination really matter – critical to individual and collective survival.
At least, that's my theory, and I'm sticking to it.
"Correction: this episode incorrectly states that lithium is lighter than air. Lithium has a lower atomic mass than oxygen or nitrogen."
So, someone at the BBC had spotted the mistake, or it had already been pointed out to them.
But I thought the correction was interesting in itself, as it made perfect sense to someone who would have the subject knowledge to have noticed the error and appreciated how it came about. I was less sure it would explain much to someone who did not already appreciate the ambiguity of the labels we give to both substances and also to the nanoscopic particles from which the are composed. More on that below, but first there is another clarification needed.
The bearable lightness of beings
Lightness strictly contrasts with heaviness, and so is about weight. Thus the 'old chestnut'1:
which is heavier: a tonne of lead or a tonne of feathers?
Of course, by definition, the mass of a tonne of anything is fixed – so a tonne of feathers has the same mass (and so, in the same gravitational field, the same weight) as a tonne of lead, even if our instinct is that feathers are lighter.
So, really this is about density. When someone (sorry, Misha Glenny) makes the reference:
the lightest metal on earth, lighter in fact than air, lithium
We might respond in various ways:
this is a meaningless comparison as without knowing how much of each we are comparing it is not possible to draw any conclusion (a great deal of air would be heavier than a tiny amount of lithium);
to make sense of this we must assume we are considering the same amount of each; or
yes, that seems reasonable: the lithium metal on earth weighs less than the air.
Option 1 is clearly a pedantic response – 'we will not assume something you do not tell us: it is not for us to add necessary information you have omitted'. Now this would be my response, but then I know I have a mind which tends to such pedantry. I would like to think this is due to my scientific training but actually think it predates that. Perhaps I am just a pedantic person.
Option 3 follows a line of argument that as we have not been told how much is being considered, then the only admissible assumption from the claim is this refers to the earth ("metal on earth"). Lithium is a reactive element (which is why it is stored under oil to avoid oxygen reaching the surface – see the image below), not found native, so any lithium metal on earth is the result of deliberate processing – and, surely, there is much less weight of lithium metal here than the weight of the atmosphere. (However, invoking the earth as a whole complicates the mass:weight relationship, so we would need to specify where we are doing the weighing – say at the earth's surface beneath the atmosphere.) I suspect most people would immediately dismiss this as not being the intended meaning.
The sensible option?
Option 2 would surely be how most people would interpret "lighter than"given the context of the claim. As long as we agree on what we mean by 'the same amount', we have no problem. We have already considered one option which clearly does not work: same amount = same mass.
In chemistry, amount of substance is measured in moles. One mole of lithium weighs about 7 g. But we only apply moles to collections of what we take as identical entities. Lithium metal is comprised of lithium atoms2, and although these atoms are not all identical (natural lithium has a small proportion of 6Li with only three nuclear neutrons mixed with the majority 7Li) they can be assumed near enough so for most purposes.
Air, however, is a mixture of different substances: mainly nitrogen, oxygen and argon, but also including many others in smaller amounts. And its composition is not fixed. In particular, the water vapour levels change a good deal; but also CO2 levels (say, over a forest as opposed to a dessert, even ignoring anthropogenic inputs due to human activity); SO2 levels being higher near active volcanoes; higher nitrogen oxides and ozone levels from car emissions in built up areas; carbon disulphide levels from algae being higher over some sea areas, etc, etc.
But dry air is mostly nitrogen and oxygen, and a mole of nitrogen weighs about 28g and a mole of oxygen about 32g, so a gas mixture which is nearly all nitrogen and oxygen and which contains 'a cumulative mole'* of these gases (say about 0.78 moles of nitrogen and 0.21 moles of oxygen, and a small amount of other atmospheric material) will weigh more than our 7g of lithium.
* But we had to do some violence there to the proper use of the mole concept.
The sharp-eyed will also have noticed that the molar masses of the substances oxygen and nitrogen were based on molecular masses – for the good reason that in the air these substances exist as diatomic molecules. That is, while it is true that "lithium has a lower atomic mass than oxygen or nitrogen" that cannot be a full explanation as atomic mass is not the most relevant factor for these gases. 3
So, 'same amount' cannot be weight, and it is not moles, but rather can sensibly be volume. Volume for volume, a denser material is heavier than a rarer (less dense) one. Sensibly, then, the claim being made in the radio programme/podcast can be understood to be that lithium is less dense than air – thus explaining all those lithium balloons we see floating around.4
A sample of the metal lithium in oil (source: wikimedia. This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.)
The metal is floating in the oil, showing it has a lower density (is 'lighter') than the oil. However, the metal is clearly not 'lighter than' air.
The chemist's triplet
Now I have rather made a lot of a single broadcast error, that it seems had already been acknowledged (though I doubt more than a very small proportion of radio listeners systematically check out webpages to find out if the programmes they listen to contain any acknowledged errors). But I think what happened here is symptomatic of a core issue in chemistry, and the teaching of chemistry.
This refers to something first widely highlighted by the Glasgow based scholar Prof. Alex Johnstone in 1982, and known as his triangle. Chemistry deals with substances which are handled at bulk scale in the laboratory and explains the proprieties of these substances in terms of models concerning theoretical entities at the nanometre scale: electrons, bonds, ions, molecules, atoms and so forth. Johnstone referred to the 'microscopic' level as opposed to the 'macroscopic level', and so this term is widely used, but a better term might be submicroscopic (or nanoscopic, cf. the nanometre) as single ions and discrete molecules are not even close to being visible under any optical microscope. 5
Further, chemistry has its specialised symbolic language, such that, for example, a chemical reaction would commonly be represented in terms of a reaction equation using chemical formulae. The expert chemist or science teacher moves effortlessly around the macroscopic/microscopic/symbolic apices of this chemist's triangle, but Johnstone strongly argued that classroom presentations that readily moved back and forth between bench phenomena, equations, and talk of molecules, would overwhelm the working memory of the novice learner. (If you are not familiar with the critical notion of working memory, perhaps check out 'how fat is your memory?')
The Johnstone Triangle
The Key to Understanding Chemistry
The idea of this 'chemist's triplet' (as it is sometimes labelled, borrowing a term from spectroscopy) has been considered the most important factor specific to chemistry pedagogy, and indeed there is at least one whole book on the topic (Reid, 2021).
Johnstone was right to alert science teachers to this issue, although an authentic chemistry education does have to work to move learners to a position where they can interpret and move across the triplet. Chemistry students need to learn to associate phenomena (e.g., burning) with both technical descriptions (e.g., combustion, oxidation) and with molecular level models of what is going on in terms of bond breaking and so forth (Taber, 2013). But learners will need much support and practice, and to be given sufficient time, to develop competence in this ability.
Perhaps a trivial example is moving from the everyday description that, say, mercury is 'heavy' (with only an implied notion of how much mercury we are talking about) to the more technical reference to density, and an explanation based on the micro-structure of mercury in terms of ions (and conduction electrons) in the condensed state.
The chemist's triplet (Taber, 2013)
Useful and misleading ambiguity
Part of the challenge for teachers (and so learners) is how key terms can mean different things according to context. So, the labels 'mercury' and 'Hg' can refer to an element in abstract, but they also refer to some of the substance mercury (a macrosopic sample of the element) and to an individual atom of mercury. A chemical equation (such as 2H2 + O2 ⇾ 2H2O) can refer to bulk quantities of substances reacting, but also to individual molecules within the theoretical models used to explain what is going during the reaction.
Often during a chemical explanation the same label ('mercury') or equation (2H2 + O2 ⇾ 2H2O) will be referred to several times, as the focus shifts from macroscopic substance to submicroscopic entities, and back again. This adds to the learning demand, but can also be confusing unless a teacher is very explicit at each point about which is being signified. An ambiguity which can be useful for the fluent, can also be confusing and frustrating for the novice (Taber, 2009).
So, in moving from considering atoms (where lithium has less mass than nitrogen) to substances (where under standard conditions lithium is much more dense than nitrogen) the meanings of 'lithium' and 'nitrogen' change – and perhaps that is what confused journalist Misha Glenny or whoever prepared his script. The experienced science teacher may find this a surprising basic error in a programme from an elite broadcaster like the BBC, but perhaps this is a useful reminder just how easily learners in introductory classes can be confused by the ambiguity reflected in the 'chemist's triplet'.
The radio programme claiming lighter-than-air lithium was part of a short series on 'The Scramble for Rare Earths'. Now 'rare earths' refers to the elements also known as the lanthanides, part of the 'f-block' in the periodic table.
The term 'earth' is also found in the common name of the group of metals, including calcium and magnesium, known as the 'alkaline earths'. 'Earths' is an anachronistic reference to materials such as oxides which were not actually elements. So, the term alkaline earths is misleading as these elements are not 'earths' but the label has become established. (Who would be a chemistry student?)
The 'rare earths' are not earths either, but metallic elements. They are also not all especially rare. They were not initially readily recognised and characterised as different rare earth elements often have similar chemical properties and they occur in the same ores, and so historically they proved difficult to separate and identify. This label of 'rare earth' is then also something of a historical hang-over: although these elements are widely dispersed in the earth's crust so although not actually rare, they are seldom found in highly concentrated sources from which they can be readily extracted.
Rare earths do not seem to be well understood by the lay-person: quite a few websites claim that "quinine contains rare earth compounds" (see 'Would you like some rare earths with that?') As quinine (an antimalarial compound often taken as a 'tonic') is a single chemical substance, it clearly does not contain other compounds: but, in any case, its formula is C20H24N2O2 so its elemental composition is just of hydrogen, carbon, nitrogen and oxygen. Thus the repeated claim about rare earths in quinine seems curious.
"Misha Glenny explores the world of rare earth metals. Reducing CO2 emissions requires critical raw materials like lithium, cobalt and nickel but mining and processing them can pose a serious threat to the environment. Can we solve the paradox?"
Presumably the paradox being that Misha Glenny explores the world of rare earth metals with reference to the alkali metallithium, and transition elementscobalt and nickel: none of which are rare earths. Perhaps he found the rare earths too rare to include? Perhaps I need to listen to the rest of the programme.
Work cited:
Johnstone A.H. (1982). Macro and microchemistry. School Science Review, 64, 377-379.
Taber, K. S. (2009). Learning at the symbolic level. Chapter 4, in J. K. Gilbert & D. F. Treagust (Eds.), Multiple Representations in Chemical Education, Dordrecht: Springer, pp.75-108. [Download chapter]
1 This is an idiom – a phrase which has currency in the language, and has come by convention to have a particular meaning; but where that sense is not clear from the literal meanings of the individual words. An 'old chestnut' is (when it is not a chestnut that is old) something which has been repeated so often it is familiar and loses any impact.
I suspect most readers will have met this question before (or a variation on it) and will not be caught out to suggest the feathers weigh less than the lead.
2 Strictly, solid lithium metal contains an array of Li+ ions in a field of delocalised electrons. No particular electron is associated with any specific lithium ion – they are in molecular orbitals and – being delocalised – do not stay in the same place. So a mole of lithium is a mole of Li+ ions with a mole of (collectively, but not individually) associated electrons. This is just one complication that must make chemistry difficult for learners.
3 We say a mole of lithium is 7g, although this counts the individual 'atoms' (see note 2) even in the solid state where a single metallic crystal could be seen to be more akin to a single molecule. Of course, a mole of lithium crystals would have a mass MUCH more than 7g. Arguably, it is somewhat arbitrary how we define a mole of metallic lithium (and a mole of an ionic solid even more so) compared with a mole of simple molecular substances such as methane or carbon dioxide – but the convention is well established. This is a formalism that could be different – but not if you want to score the marks in a chemistry examination.
4 If lithium was heated to give off vapour, then that vapour would be less dense than air. However lithium is highly reactive and the vapour can only be kept stable in a vacuum or an inert atmosphere (and would only remain a vapour in an atmosphere at a high enough temperature). In the earth's atmosphere any slight leakage from a balloon would likely quickly lead to an explosive failure. Perhaps there is a planet somewhere with a hot enough argon atmosphere where lithium filled balloons could in principle be safely used if a suitable inert material could be found to make the balloon itself – but I doubt this would ever be a preferred option.
5 Arguably, a pure single crystal diamond could be considered a molecule, but that is not what we normally mean by a molecule. Again the choice of how to label different entities is somewhat arbitrary (in the sense that different decisions could rationally have been reached), and learners have to acquire the canonical, historically contingent, labels.
A plea for consistent and coherent labelling of times
Keith S. Taber
Stardate: -297795.016615931
To call noon either 'before noon' (a.m.) or 'after noon' (p.m.) is a crime against good nomenclature.
I saw a reference to a webinar for teachers, 'Teaching Organic Chemistry with videos', on a social media site, and thinking it looked useful was tempted to retweet the message. However, I thought I should do some due diligence first in case I was about to promote somethings dodgy. (That sounds a little paranoid, but as I routinely get invited to contribute to dubious 'predatory' conferences and journals, I try not to take anything on-line at face value).
Checking the website, I found the webinar was being offered several times to suit people in different parts of the world – which seemed very useful.
However, I then noticed that two of the sessions were scheduled for 12 PM in their local time zones. But what is 12 PM? Perhaps that is pretty basic and everybody (apart from me) knows. To my mind the term 12 PM must mean 12 midnight (as I explain below), but that seemed as unlikely choice of webinar time. Checking some websites, it seems the conventional take is that 12 PM means 12 noon: but that is both an inconsistent, and indeed self-contradictory, idea.
(Image by PIRO from Pixabay)
The 24 hour clock
Of course all such uncertainty is avoided by using the 24 hour clock. The hours then run sensibly through 00.00, 01.00, 02.00, 03.00…10.00, 11.00, 12.00, 13.00, 14.00…21.00, 22.00, 23.00, (24.00 which re-sets as) 0.00.
The 24 hour clock avoids ambiguity, unlike the 12 hour version which runs twice a day. Often there will be enough context in communication for this not to be problematic…
meet me at 11 of the clock (11 o'clock) for morning coffee
shall we lunch at 1 o'clock
the after-work meeting will start at 6 o'clock
I'll be getting home from work about seven-thirty
…unless you do not realise your interlocutor works night shifts!
But in this era of the global village, a colleague from the other side of the world who tells you they will be contacting you at seven o'clock could easily mean either seven in the morning or seven in the evening. So, distinguishing 07.00 from 19.00 is useful.
Now, it might seem that the 24 clock is not needed if we always specify whether a time is a.m. or p.m. – ante meridiem or post meridiem. Well, perhaps, but as I argue below I really do not think that can work for 12 noon. ('Meridiem' comes from the Latin for noon or midday.)
We might wonder why we run the hours twice in a day, and do not simply use a single count each day. And here, we need to be careful to acknowledge potential ambiguity in the word 'day 'itself – which often means a 24 period, but is also used in contrast to night, as in the idiom "like day and night" *. And in terms of that ambiguity, we might note that traditionally there were 12 hours in the day. For our double daily cycle of hours is historically contingent – that is, it is a hang over from a different time (sic).
* Ambiguity can be undermined by context. The Kinks famously sang about "all day…", but presumably did not intend that to mean a 24 hour period as they specified "…all of the night" as well.
12 hours of daylight, 12 hours of nighttime, 12 hours of sunset
These days we (nearly) all have 24 hour electricity 1, so it can be as bright as we like any time of day or night. But only a few centuries ago the ambient light levels affected people's lives much more. Even if a fire gave off light inside the home, there were no streetlights, and so being outside at night was more of an event.
Students of British social history will have heard of the Lunar Society that operated around Birmingham at the time when the industrial revolution was underway, and that included such luminaries (luniaries?) as the chemist Joseph Priestley, the potter and industrialist Josiah Wedgwood (grandfather of Charles Darwin), Matthew Boulton and James Watt (producers of Boulton & Watt steam engines), and the physician, poet, and evolutionary speculator Erasmus Darwin (the other grandfather of Charles Darwin).
The group were not called the Lunar Society from astrological sensibilities, but because they met on the day of the full moon each month – for the perfectly pragmatic reason that before street lighting it was very easy to have accidents travelling after dark, and the night of the full moon had the best chance (British weather notwithstanding) of a safe level of natural illumination.
So, for most of human history (and all of its prehistory) the distinction between day and night was even more significant than it is today. So it became common to keep time separately in these two periods. The 'day' was divided into 12 equal parts – hours, and the night was also divided into twelve equal hours. That involves a very different organisation to that we are familiar with today.
The day began at dawn, and after twelve hours of day, night begins at dusk, and then after twelve hours of nighttime another dawn brings the new day. Measuring the start of a new day by the rising or setting of the sun is still practiced today in some communities – so the Jewish and Islamic day starts at nightfall. (In the Biblical account of the creation evening is mentioned before morning, suggesting a mythical first day started with the evening).
But clearly, with this system, the day and night are only of equal duration at the equinoxes. During the Summer the daylight hours last much longer than the nighttime hours and in the Winter the nighttime hours last much longer than the daytime hours (given that there are twelve of each). That is possible because an hour was not directly tied to the Earth's rotation (1 hour = 1/24 of a day) but was one twelfth of the daytime, or of the nighttime, at that particular point in the year.
Schematic representation of how unequal hours were counted from dusk and dawn, with the day and night times each divided into 12 hours. Daytime hours were longer in summer and shorter in Winter.
Unequal hours – an alternative conception 2
These 'unequal', 'temporal' or 'seasonal' hours were then not of a fixed duration. At an equinox an hour was much like our modern hour. So, at the vernal equinox the hours all matched up. But the daytime hours then got longer as the Summer solstice approached, with a corresponding shortening of the nighttime hours. Then the daytime hours shortened, with a corresponding lengthening of the nighttime hours, till at the autumnal equinox they were again matched; but the shift continued to Winter solstice when the daytime hours were at their shortest (and the nighttime hours their longest).
Now clearly such a system is geographically linked – as the amount of daytime one gets depends where on the globe one lives (latitude) – so each location could have its own version of unequal hours starting from its own determination of when the day started (depending on longitude). Up here 3 in the U.K. where the the contrast in 'day' length between Summer and Winter is quite stark, we can imagine a mid-summer day having daylight hours twice as long as nighttime hours – and the converse in Winter. Further North, up 3 near Arctic circle, if the convention was ever adopted there, the situation would get even more extreme!
That notion of local time survived long after the fixed-duration (equal) hour was established. Today we have time zones that often encompass vast areas, but once each town made its own determination of high noon when the sun reached its highest point in the sky, which would vary with longitude. This practice changed with the advent of personal timepieces and fast transportation. When it took several days to ride from London to Bristol, with a portable sundial in the pocket, it was of little import that the difference in longitude led to a different local timezone.
But once people could get on a train in one location, with their watch set to the town clock, and get off in another town a few hours later, the importance of a consistent time zone mattered more than the sun being at its highest point at midday wherever you lived in the country.4 With easy and quick international travel, the adoption of some kind of agreed global standard also become important. So although today there are different time zones, they are all referenced to Coordinated Universal Time (which aligns with GMT, Greenwich Mean Time). So, even if travel disorientates the body clock, you will know how to reset your watch when you arrive at your destination. If you fly from London to Vancouver you will know that local time is 7 hours displaced from GMT.
"Twelve hours of sunset, six thousand miles Illusions and movies, far away smiles Twelve hours of sunset, half a day in the skies I'll see you tomorrow as the steel crow flies Oh, how time flies"
(From the lyrics of 'Twelve hours of sunset' by Roy Harper)
By flying towards the setting sun at a sufficient speed its position in the sky can be kept constant. (Image by u_37suikdl from Pixabay)
AM or PM?
So, nowadays, we have 24 hours in a day, and they are all equal – of the same duration – regardless of the time of year or where we live. But we commonly keep the 2 x 12 labelling, and sometimes we distinguish the two 7 o'clocks as 7 a.m. and 7 p.m. And the same with the two 3 o'clocks and the two 8.15s and the two 11.30s. Which is fine – but I think this runs into trouble when we get to noon.
By noon, I mean what is sometimes called midday as it comes halfway through the 24 day. But I do not think we should call it 12 p.m. I have two reasons to object to this.
One is simply continuity. If we call noon '12 p.m.', then something very odd happens with our hours: we pass from
…9 a.m. to 10 a.m. to 11 a.m. to 12 p.m. to 1 p.m. to 2 p.m. to 3 p.m….
That surely is bonkers!
The conventional designation of times to a.m. and p.m. leads to bizzare reversals of labelling (at 12.59 a.m. to 1.00 a.m. and 12.59 p.m. to 1.00 p.m.) – enough to give one a saw tooth if not a sore head.An alternative representation of the conventional designation of times to a.m. and p.m. over two days (In science, graphical representations with abrupt shifts in gradient tend to reflect a natural discontinuity, such as a phase change.)
If, instead, we were to call noon '12 a.m.' then we would have a much more sensible progression of hours:
…9 a.m. to 10 a.m. to 11 a.m. to 12 a.m. to 1 p.m. to 2 p.m. to 3 p.m….
Which seems to work much better. Until we think about minutes – as 12.01 afternoon has a different denotation (p.m.) to 12.00:
11.57 a.m. to 11.58 a.m. to 11.59 a.m. to 12.00 a.m. to 12.01 p.m. to 12.02 p.m. to 12.03 p.m….
Perhaps this does not matter? It could be avoided by keeping the a.m. designation till we shift from 12 back to 1:
12.57 a.m. to 12.58 a.m. to 12.59 a.m. to 1.00 p.m. to 1.01 p.m. to 1.02 p.m. to 1.03 p.m….
In many ways, that works much better- at least in terms of the flow of numbers and the resetting back to the hour 1. In the UK we have 'British Summer Time' (BST) for half of the year, and during BST (which is an hour ahead of GMT) noon is actually closer to 1 o'clock anyway, so in one sense this would correct for switching to daylight saving time. 4
So, if we have todesignate noon as a.m. or p.m., I would prefer that system. But clearly whatever is used has to be used by everyone for it to be workable.
And there is another good reason to avoid both of these conventions.
12 a.m. and 12 p.m. should both be midnight
That is, that to call noon either 12 a.m. or 12 p.m. is internally inconsistent (and one thing we do not like in science is inconsistencies: we do not like them when they arise from relating two areas of science, and we really do not like them when they are inherent within a single field).
12. a.m. means 12 ante meridian, that is 12 hours, before noon. And 12 hours before noon is midnight. 12 p.m. means 12 post meridiem, that is 12 hours, after noon. And 12 hours after noon is midnight (the next midnight after the 12 a.m.).
To call noon either 'before noon' (a.m.) or 'after noon' (p.m.) is a crime against good nomenclature. So, I really do not think we should use either 12 a.m. or 12 p.m. to describe 12 noon. (And if 12 p.m. is midnight, is that the midnight at the end of the day, and 12 a.m. the midnight at the start of the day? In which case, is 12 p.m. Thursday the same as 12 a.m. Friday?)
Midnight is equally (that is 12 hours) ante meridiem and post meridiem so even if calling 12 midnight a.m. or p.m. is not strictly self-contradictory, it does not seem especially clear and helpful. So, it seems labelling 12 o'clock, either of the daily 12 o'clocks, with a.m. or p.m. is simply inviting confusion.
Noon is neither before noon nor after noon
There are two 12s in the day – 12 midnight and 12 noon (or midday). So, we should stick to those terms and use a.m. and p.m. for all the other times that clearly can be seen to reasonably be labelled as before noon or after noon on a particular day.
…9 a.m. to 10 a.m. to 11 a.m. to 12 noon to 1 p.m. to 2 p.m. to 3 p.m…. …9 p.m. to 10 p.m. to 11 p.m. to 12 midnight to 1 a.m. to 2 a.m. to 3 a.m…
I hope we can all agree to that simple convention – or just use the 24 hour clock.
I am pleased that is now sorted. Next we have do away the disruptive twice yearly time-shifts moving to and from so-called daylight saving time and stick to G.M.T. (or even B.S.T. – or any other option as long as we keep to it all year round) – and then I will be a lot happier.
Notes:
* One could avoid that problem by using different terms or suffixes – but both meanings of 'day' are so well accepted I will avoid distinguishing them as, say, daysolar for the time for a full rotation of the earth compared to the Sun, as from one noon to the next; and daylight for the period between dawn and dusk. Daysolar is also called nycthemeron, but that is not a term I've heard a lot in public discourse.
It actually takes the earth about 23 hours 56' 4" to rotate once on its axis as measured by the distant stars – daysidereal – but it needs to turn a little more to "catch up with the sun" due to the effect of the Earth's orbit around the Sun.
"…Length of the tropical year: equinox equinox 365.24 days Length of the sidereal year: fixed star fixed star 365.26 days Length of the mean solar day: 24 hours and 3 minutes and 56.555 seconds at mean [sidereal] time Length of the mean sidereal day: 23 hours and 56 minutes and 4.091 seconds at mean solar time…"
From the (spoken word) lyrics of 'Albedo 0.39' (Vangelis) [I have made a correction to an apparent error in the lyrics – thanks to colleagues on PTNC for confirming my suspicion that there was a mistake in the original]
1 I am only too aware that I am writing these words at a time when the people of Gaza have had their electricity supplies stopped as a tactic of the Israeli's state's genocidal war against the Palestinian people, with its declared aim to destroy Hamas. The extensive destruction of Gaza, including the deliberate targeting of journalists, hospitals, refuge camps, ambulances, international aid workers; and the killing and maiming (and orphaning) of many, many thousands of completely innocent children, is supposedly in part justified by acts of terrorism against Israeli people which are just as evil and equally deserving of condemnation. The torturing, raping and murdering of fellow humans is just as despicable and an affront to humanity (and God, for those who believe) regardless of the ethnicity, nationality or religion of the oppressors or victims.
The genocide continues despite the international outcry, including condemnation by many Jewish people from around the world, and, indeed, by many Israeli citizens. Just as the Gazans should not all be treated as guilty of terrorism, neither the Jewish people, nor Israeli citizens, should be collectively identified with the ongoing war crimes of the Israeli state.
2 We commonly use the term 'alternative conception' to imply a wrong idea inconsistent with the canonical conception – a 'misconception'. However two different conceptions of the same target phenomena may both be incorrect, or there may be situations were alternative conceptions are not right or wrong just different. So deciding an hour would be 1/12 of the night or daytime (and so would change in duration during the year) or be 1/24 of the whole daily cycle (and so be of constant duration) is a choice of which option is most convenient, clear or practical rather than being right or wrong.
Our labelling of times cannot be 'wrong' as it is a convention, but I think I had an alternative conception of 12 p.m. as I have always assumed that must mean midnight. Perhaps I was taught differently as a child, but just rejected the idea that anyone would think to designate noon as 12 p.m. as just too illogical and unlikely.
3 'Up' given the convention that North comes at the top of the map, which is completely arbitrary. If we assume visitors from outside this solar system would chart earth and put the equator half way down their map (another arbitrary choice – William Gilbert's representations of the Earth is his classic 'On the magnet' – arguably the first full length science book – showed the equator vertically), there is a 50:50 chance of which way up they would present the Earth – with Mercator or McArthur.
McArthur's map of the world
4 The actual time of high noon varies a little day to day on a system where we have fixed day lengths (rather than days being of slightly different lengths at different times of year) and a fixed 'hour' duration: so solar noon can actually be up to about a quarter of an hour before or after 12.00 GMT (13.00 BST) – even if you live in Greenwich. So, nominal 'midday' is usually not quite exactly midday, even living on the Greenwich meridian. We can either work with a system that matches natural patterns, or one that has consistent fixed points and fixed duration. These days we find the latter option more attractive.
So, to sum up, one could choose to align the clocks with the daily cycle of nature and still define noon as when the sun is seen to be at its zenith (highest point in the sky that day according to an observer in some place), but some days would be slightly shorter and some slightly longer, and your time would not match that of someone living in a town or city to the West or East of your position.
Instead, 12 noon GMT is based on an averaging for when the sun is at its zenith (over Greenwich) that keeps all days as of equal duration and means everyone in the time zone agrees on the time – and someone in another time zone has a different time by a constant and known differential. Well, in principle, anyway.
Making unfamiliar cultures familiar using scientific concepts
Keith S. Taber
Clifford Geertz may have been a social scientist, but he clearly thought that some abstract ideas about culture, society and politics were best explained using concepts and terminology from the natural sciences.
Clifford Geertz was a social scientist who referenced a goof deal of scientific vocabulary
I first came across the anthropologist Clifford Geertz when teaching research methods to graduate students. Geertz had popularised the notion of the importance of thick description, or rich description, in writing case studies. I acquired his book 'The Interpretation of Cultures' (a collection of his papers and essays) to read more about this. I found Geertz was an engaging and often entertaining author.
"Getting caught, or almost caught, in a vice raid is perhaps not a very generalisable recipe for achieving that mysterious necessity of anthropological field work, rapport, but for me it worked very well."
(From 'Deep play: notes on the Balinese cockfight')
Anthropology: A rather different kind of science – largely based on case studies.
Generalisation in natural science
Case studies are very important in social sciences, in a way that does not really get reflected in natural science.
It has long been recognised that in subjects such as chemistry and physics we can often generalise from a very modest number of specimens. So, any sample of pure water at atmospheric pressure will boil around 100˚C.1 All crystals of NaCl have the same cubic structure. All steel wires will stretch when loaded. And so on. Clearly scientists have not examined, say, all the NaCl crystals that have ever formed in the universe, and indeed have only actually ever examined a tiny fraction, in one local area (universally speaking), over a short time period (cosmologically, or even geologically, speaking) so such claims are actually generalisationssupported by theoretical assumptions. Our theories give us good reasons to think we understand how and why salt crystals form, and so how the same salt (e.g., NaCl) will always form the same type of crystal.2
Even in biology, where the key foci of interest, organisms, are immensely more complex than salt crystals or steel wires, generalisation is, despite Darwin 3, widespread:
"We might imagine a natural scientist, a logician, and a sceptical philosopher, visiting the local pond. The scientist might proclaim,
"see that frog there, if we were to dissect the poor creature, we would find it has a heart".
The logician might suggest that the scientist cannot be certain of this as she is basing her claim on an inductive process that is logically insecure. Certainly, every frog that has ever been examined sufficiently to determine its internal structure has been found to have a heart, but given that many frogs, indeed the vast majority, have never been specifically examined in this regard, it is not possible to know for certain that such a generalisation is valid. (The sceptic, is unable to arbitrate as he simply refuses to acknowledge that he knows there is a frog present, or indeed that he can be sure he is out walking with colleagues who are discussing one, rather than perhaps simply dreaming about the whole episode.)
…I imagine most readers are still siding with the scientist's claim. So, can we be confident this particular frog has a heart, without ourselves being heartless enough to cut it open to see?
Strictly, in an absolute sense, we cannot know for certain the entity identified as a frog has a heart. After all,
perhaps it is a visiting alien from another solar system that looks superficially like our frogs but has very different anatomy;
perhaps it is a mechanical automaton disguised as a frog, that is covertly collecting intelligence data for a foreign power;
perhaps it is a perfectly convincing holographic image of a 'late' frog that, since being imaged, was eaten by a predator;
perhaps other logically possible but barely feasible options come to mind?
But if it really is a living (Terran) frog, then we know enough about vertebrate evolution, anatomy and physiology, to be as near to certain it has a functioning heart as we could be certain of just about anything. 4
Generalisation in social science
Often, however, this type of generalisation simply does not work in social science contexts. If we find that a particular specimen of gorilla has seven cervical vertebrae then we can probably assume: so do other gorillas. But if we find that one school has 26 teachers, we clearly cannot assume this will apply to the next school we look at. Similarly, the examination results and truancy levels will vary greatly between schools. If we find one 14 year old learner thinks that plants only respire during the night time, then it is useful to keep this in mind when working with other students, but we cannot simply assume they will also think this.
The distinction here is not absolute, as clearly there are many things that vary between specimens of the same species, which is why many biological studies use large samples and statistics. In general [sic], generalisation gets more problematic as we shift from physical sciences through life sciences to social sciences. And this is partially why case study is so common within the social sciences.
The point is that the assumption that we can usually safely generalise from one NaCl crystal to another, but not from one biology teacher to another, is based on theoretical considerations that tell us why the shape (but not the mass or temperature) of a crystal transfers from one specimen of a substance to another, but why the teaching style or subject knowledge of one teacher depends on so many factors that it cannot be assumed to transfer to other teachers.
Drawing upon both a quotidian comparison and a scientific simile, Geertz warned against seeing "a remote locality as the world in a teacup or as the sociological equivalent of a cloud chamber".
A case study examines in depth one instance from among many instances of that kind: one teacher's teaching of entropy; one school's schemes of work for lower secondary science; one learner's understanding of photosynthesis; the examples, similes and analogies used in one textbook; …
Case studies look at a single instance (e.g., one school, one classroom, one lesson, one teaching episode) in great detail. Case studies are used when studying complex phenomena that are embedded in their context and so have to be studied in situ. You can study a crystal in the lab. You can also study extract cells from an organism and look at them in a Petri dish – but those isolated cells in vitro will only tell you so much about how they normally function in vivo within the original tissue.
Similarly, if you move a teacher and her class out of their normal classroom embedded in a particular school in order to to study a lesson in a special teaching laboratory in a research institution set up with many cameras and microphones, you cannot assume you will see the lesson that would have taken place in the normal context. Case studies therefore need to be 'naturalisic' (carried out in their usual context) rather than involving deliberate researcher manipulation. Geertz rejected the description of the field research site as a natural laboratory, reasonably asking "what kind of laboratory is it where none of the parameters are manipulatable?"
When I worked in further education I recall an inspection where one colleague told us that the external inspector had found her way to her classroom late, after the lesson had already started, and so asked the teacher to start the lesson again. This would have enabled the inspector to see the teacher and class act out the start of the lesson, but clearly she could not observe an authentic teaching episode in those circumstances.
Case study is clearly a sensible strategy when he have a particular interest in the specific case (why do this teacher's students gets such amazing examination results?; why does this school have virtually zero truancy rates?), but is of itself a very limited way of learning about the general situation. We learn about the general by a dual track (and often iterative) process where we use both surveys to find out about typicality, and case studies to understand processes and to identify the questions it is useful to include in surveys.
If case studies are to be useful, they need to offer a detailed account (that 'thick description') of the case, including its context: so to understand something about an observed lesson it may be useful to know about the teacher's experience and qualifications; about the school demographic statistics and ethos; about the curriculum being followed, and other policies in place; and so forth.
As one example, to understand why a science teacher does not challenge a student's clear misconceptions about natural selection (is the teacher not paying attention, or not motivated, or herself ignorant of the science?), it may sometimes be important to know something about the local community and and administrative practices. In the UK, a state school teacher (who is legally protected from arbitrary, capricious or disproportionate disciplinary action) is not going to get in trouble for explaining science that is prescribed in the curriculum, even if some parents do not like what is taught; but that may not be true in a very different context where the local population largely holds fundamentalist, anti-science, views, and can put direct pressure on school leaders to fire staff.
Beware of unjustified generalisation
This use of 'thick description' provides the context for a reader to better understand the case. However, no matter how detailed a case study is, and regardless of the insight it offers into that case, a single case by itself never provides the grounds for generalisation beyond the case. It can certainly offer useful hypotheses to be tested in other cases – but not safe conclusions!
Geertz was an anthropologist who knew that much field work involves specific researchers (with their idiosyncraticinterpretive resources – background knowledge, past experiences, perspectives, beliefs, etc. -and individual personalities and inter-personal skills) spending extended periods of time in very specific contexts – this village, that town, this monastery, that ministry… The investigators were not just meant to observe and record, but also to look to make sense of (and so interpret) the cultures they were immersed in – but this invites over-generalisation. Geertz warns his readers of this at one point,
"I want to do two things which are quintessentially anthropological: to discuss a curious case from a distant land; and to draw from that case some conclusions of fact and method more far-reaching than any such isolated example can possibly sustain."
(From: 'Politics past, politics present: some notes on the uses of anthropology in understanding the new states')
Using science to make the unfamiliar familiar
One of the features of Geertz's writings that I found interesting was his use of scientific notions. Often on this site I have referred to the role of the teacher in 'making the unfamiliar familiar' and suggested that science communicators (such as teachers, but also journalists, authors of popular science books and so forth) seek to make abstract scientific ideas familiar for their audience by comparing them with something assumed to already be very familiar. As when Geertz suggests that the 'human brain resembles the cabbage'. I have also argued that whilst this may be a very powerful initial teaching move, it needs to be just a first step, or learners are sometimes left with new misconceptions of the science.
For a science teacher, the scientific idea is thetarget knowledge to be introduced, and a comparison with something familiar is sought which offers a useful analogue. I list myriad examples on this site – some being science teachers' stock comparisons, some being more original and creative, and indeed some which are perhaps quite obscure. Here are just a few examples:
But this can be flipped when the audience has a strong science knowledge, and so a scientific phenomenon or notion can be used to introduce something less familiar. (As one example, the limited capacity of working memory and the idea of 'chunking' may be introduced by comparison with different triglycerides: see How fat is your memory? A chemical analogy for working memory. But this is only useful if the audience already knows about the basic structure of triglycerides.)
Geertz may have been a social scientist, but he clearly assumed some abstract ideas about culture, society and politics were best explained using concepts and terminology from the natural sciences. So, for example, he made the argument for case study approaches in research,
"The notion that unless a cultural phenomenon is empirically universal it cannot reflect anything about the nature of man is about as logical as the notion that because sickle-cell anaemia is, fortunately, not universal, it cannot tell us anything about human genetic processes. It is not whether phenomena are empirically common that it is critical in science – else why should Becquerel have been so interested in the peculiar behaviour of uranium? – but whether they can be made to reveal the enduring natural processes that underlie them. Seeing heaven in a grain of sand 5 is not a trick that only poets can accomplish."
(From: 'The impact of the concept of culture on the concept of man')
Geertz was also aware of another failing that I have seen many novice (and some experienced) researchers fall into. In education, as in anthropology, we often rely on research participants as informants, but we have to be careful not to confuse what they tell us with direct observations:
'the teacher is careful to involve all learners in the class in answering questions and classroom discussion' (when it should be: the teacher reports that he is careful to involve all learners in the class in answering questions and classroom discussion )
'the learner was very good at using mathematics in physics lessons' (when it should be: the learner thought that she very good at using mathematics in physics lessons.
'the school had a highly qualified, and select group of teachers who were all enthusiastic subject experts' (or so the headteacher told me).
If such slips seem rather amateur affairs, it is not uncommon to see participant ratings mis-described: so a statements like '58% of the teachers were highly confident in using the internet in the classroom' may be based on participants responding to a scale item on a questionnaire (asking 'How confident are you…') where 58% of respondents selected the 'highly confident' rating.
So, actually '58% of the teachers rated themselves as highly confident in using the internet in the classroom'. For these two things to be equivalent we have to ourselves be 'highly confident' in a number of regards – some more likely than others. Here are some that come to mind:
the teachers took the questionnaire seriously, and did not just tick boxes arbitrarily to complete the activity quickly (I am sure none of us have ever done that 😎);
the teachers read the question carefully, and ticked the box associated with their genuine rating (i.e., did not tick the wrong box by mistake, perhaps misaligning response boxes for a different item);
the teachers understood and shared the researcher's intended meaning of the item (e.g., researcher and responder mean the same thing by 'confidence in using the internet in the classroom');
the teachers had a stable level of confidence such that a rating reflected more than their feeling at that moment in time (perhaps after an especially successful, or fraught, lesson);
a teacher's assessment of confidence clearly fitted with one of the available response options (here, highly confident – perhaps the only options presented to be selected from were 'highly competent'; 'neither professionally competent nor incompetent'; 'completely hopeless');
the teachers were open and honest about their responses (so, not influenced by how the researcher might perceive them, or who else might gain access to the data and for what purpose);
the teacher was a good judge of their own level of confidence (and does not come from a cultural context where it would be shameful to boast, or where exaggeration is expected).
As scientists we tend to come to rely on instrumentation even though it is fallible. We may report distances and temperatures and so forth without feeling we need to add a caveat such as "according to the thermometer" each time. 6 But instrumentation in social science tends to be subject to more complications. Geertz realised that in his field there was commonly the equivalent of writing that '58% of the teachers were highly confident in using the internet in the classroom' when the data only told us '58% of the teachers rated themselves as highly confident in using the internet in the classroom':
"In finished anthropological writings, including those collected here, this fact – that what we call our data are really our own constructions of other people's construction of what they and their compatriots are up to – is obscured because most of what we need to comprehend a particular vent, ritual, custom, idea, or whatever is insinuated as background information before the thing itself is is directly examined."
(From 'Thick description: toward an interpretative theory of culture.')
Some scientific comparisons
In discussing a teknonymous system of reference – where someone who had been named Joe at birth but who is now the father of Bert, is commonly known as 'Father of Bert' rather than Joe; at least until Bert and Bertha bring forth Susie (and take on new names themselves accordingly), at which point Joe/Father of Bert is then henceforth referred to as 'Grandfather of Susie' – Geertz suggests what "looks like a celebration of a temporal process is in fact a celebration of the maintenance of what, borrowing a term from physics, Grgory Batesaon has aptly called 'steady state'." This is best seen as a simile, as the figurative use of the term 'steady state' is clearly marked (both by the 'scare quotes' and the acknowledgement of the borrowing of the term).
Many of Geertz's figures of speech are metaphors where the comparison being used is not explicitly marked (so the state capital 'was' the nucleus). Another 'doubly marked' simile (by scare quotes and the phrase 'so to speak') concerned the idea of a centre of gravity:
"The two betting systems, though formally incongruent, are not really contradictory to one another, but are part of a single larger system, in which the centre bet is, so to speak, the 'centre of gravity', drawing , the larger it is the more so, the outside bets toward the short-odds end of the scale."
(From 'Deep play: notes on the Balinese cockfight')
Among the examples of Geertz using scientific concepts as the 'familiar' to introduce ideas to his readers that I spotted were:
Not all of these examples seemed to be entirely coherent, or strictly aligned with the technical concept. Geertz was using the ideas as figures of speech, relying on the way a general readership might understand them. Although, in some of these cases I wonder how familiar his readership might be with the scientific idea. We can only 'make the unfamiliar familiar' by comparing what is currently unfamiliar with what is – already – familiar.
Making the unfamiliar familiar, by using something else unfamiliar?
My general argument on this site has been that if the comparison being referred to is not already familiar to an audience, then it cannot help explain the target concept – unless the unfamiliar comparison is first itself explained; which would seem to make it self-defeating as a teaching move.
However, while I think this is generally true, I can see possible exceptions.
One scenario might be where the target idea is seen as so abstract, that the teacher or author feels it is worth first introducing, and explaining, a more concrete or visualisable comparison as a potential stepping stone to the target concept.
Another scenario might be where the teacher or author has a comparison which is considered especially memorable (perhaps controversial or risque, or a vivid or bizarre image), and so again thinks the indirect route to the target concept may be effective (or, at least, entertaining).
There might also be an argument, at least with some audiences, that because using a comparison makes the (engaged) reader process the comparison it aids understanding and later recall even when it needs to be explained before it will work as a comparison.
So, for example, typical readers of anthropology reports may know little about the neural organisation of cephalopods, but when being told that "the octopus, whose tentacles are in large part separately integrated, neurally quite poorly connected with one another and with what in the octopus passes for a brain … nonetheless manages…to get around…", perhaps this elicits reflection on how being an octopus must be such a different experience to being human, such that the reader pauses for thought, and then (while imagining the octopus moving around without a"smoothly coordinated synergy of parts" but rather "by disjointed movements of this part, then that") pays particular attention to how this offers a "appropriate image [for] cultural organisation".
These are tentacled, sorry, tentative suggestions, and I would imagine they all sometimes apply – but empirical evidence is needed to test out their range of effectiveness. Perhaps this kind of work has been done (I do not recall seeing any studies) but, if not, it should perhaps be part of a research programme exploring the effectiveness of such devices (similes, metaphors, analogies, etc.) in relation to their dimensions and characteristics, modes of presentation, and particular kinds of audiences (Taber, 2025).
Some of Geertz's references could certainly be seen as fitting the wider zeitgeist – references to DNA with its double helix may be seen to tap into a common cultural motif:
"So far as culture patterns, that is, systems or complexes of symbols, are concerned…that they are extrinsic sources of information. By 'extrinsic', I mean only that – unlike genes for example – they lie outside the boundaries of the individual organism …By 'source of information', I mean only that – like genes – they provide a blueprint of template in terms of which processes external to themselves can be given a definite form. As the order of bases in a strand of DNA forms a coded program, a set of instructions, or a recipe, for the synthesis of the structurally complex proteins which shape organic functioning, so culture patterns provide such programmes for the institution of the social and psychological processes which shape human behavior …this comparison of gene and symbol is more than a strained analogy …
"Symbol systems…are to the process of social life as a computer's program is to its operations, the genic helix to the development of the organism…
There is a sense in which a computer's program is an outcome of prior developments in the technology of computing, a particular helix of phylogenetic history…But …one can, in principle anyhow, write out the program, isolate the helix…"
(From 'Religion as a cultural system' and 'After the revolution: The fate of nationalism in the new states')
Geertz also goes beyond simply offering metaphors, as in this extract from an essay review of the classic structuralist anthropology text with a title normally rendered into English as 'The Savage Mind':
"That Lévi-Strauss should have been able to transmute the romantic passions of Tristes Tropiques into the hypermodern intellectualism of La Pense Sauvage is surely a startling achievement. But there remain the questions one cannot help but ask. Is this transmutation science or alchemy? Is the 'very simple transformation' which produced a general theory out of a persona disappointment real or a sleight of hand? Is it a genuine demolition of the walls which seem to separate mind from mind by showing that the walls are surface structures only, or is it an elaborately disguised evasion necessitated by a failure to breach them when they were directly encountered?"
(From 'The cerebral savage: on the work of Claude Lévi-Strauss')
It is worth noting here that whenever a work is translated from one language to another, there is an interpretive process, as many words do not have direct equivalents (covering precisely the same scope or range, with exactly the same nuances) in other languages. 'Savage' in English suggests (to me at least) aggression, and an association with violence. The French original 'sauvage' could be translated instead as 'wild' or 'untamed' which do not necessarily have the same negative associations. This is why when educational, and other social, research is reported in a language other than that in which data was collected, it is important for investigators to report this, and explain how the authenticity of translation was tested (Taber, 2018).
This device of an extended metaphor, where a comparison is not just mentioned at one point but threaded through a passage, can approach analogy – but without the explicit mapping of analogue-to-target expected in a formal teaching analogy. Here the idea of a property of meaning is compared with physical or chemical properties, but without the techniques the scientist has to identify and quantify such properties:
"And so we hear cultural integration spoken of as a harmony of meaning, cultural change as an instability of meaning, and cultural conflict as an incongruity of meaning, with the implication that the harmony, the instability, or the incongruity are properties of meaning itself, as, say, sweetness is a property of sugar or brittleness of glass.
Yet, when we try to treat these properties as we would sweetness or brittleness, they fail to behave, 'logically', in the expected way. When we look for the constituents of the harmony, the instability, or the incongruity, we are unable to find them resident in that of which they are presumably properties. One cannot run symbolic forms through some sort of cultural assay to discover their harmony content, their stability ratio, or their index of incongruity; one can only look and see if the forms in question are in fact coexisting, changing, or interfering with one another in some way or other, which is like tasting sugar to see if it is sweet or dropping a glass to see if it is brittle, not like investigating the chemical composition of sugar or the physical structure of glass."
"But, details aside, the point is that there swirl around the emerging governmental institutions of the new states, and the specialised politics they tend to support, a whole host of self-reinforcing whirlpools of primordial discontent, and that the parapolitical maelstrom is a great part an outcome – to continue the metaphor, a backwash – of that process of political development itself."
(From 'The integrative revolution: The primordial sentiments and civil politics in the new states')
Offering manifold comparisons
Sometimes Geertz offers several alternative comparisons for his readers: so, above, the genetic helix is offered in parallel with a computer program, a blueprint for building a bridge, the score of a musical performance, and a recipe for cake. Another example might be:
"The second law of thermodynamics, or
the principle of natural selection, or
the production of unconscious motivation, or
the organisation of the means of production
does not explain everything, not even everything human, but it still explains something; and our attention shifts to isolating just what that something is, to disentangle ourselves from a lot of pseudoscience to which, in the first flush of its celebrity, it has also given rise."
(From 'Thick description: toward an interpretative theory of culture')
There are several ways to explain use of this technique. One is that Geertz is sometimes not confident in his comparisons, so offers alternatives – if one does not 'hit home' with a reader, another might. Perhaps this is about diversity and personalisation – after all, each reader brings their own unique set of interpretive resources (based on their idiosyncratic array of knowledge and experience), so if you do not know about the physics or biology, perhaps you do know about the example from psychology, or economics.
Alternatively, I sometimes got a sense that Geertz was simply enjoying the writing process, and not wanting to censor the creative spark as ideas presented themselves to him. Of course, that is a personal interpretation based on my unique set of interpretive resources: I have also sometimes got the feeling that I am getting carried away with my writing – carried along by the 'flow' experience described by Mihaly Csikszentmihalyi – enjoying my own prose (which at least means that a minimum of one person does), and so possibly at risk of writing too much and consequently boring the reader. Reading Geertz gave me the feeling that he enjoyed the writing process, and that he crafted his writing with a concern for style as well as to communicate information.
From a pedagogic point of view, comparisons (similes, metaphors, analogies) are like models, always imperfect reflections of the target. Greetz suggested that not only was metaphor strictly wrong, but that it could be most effective when most wrong! In teaching it is important to highlight the positive and negative analogy (how this model is like a cell or a star or a molecule, and also how it is not), and that level of explication would be suitable for a textbook; but otherwise could (as well as disrupting style) come across as too didactic. By offering multiple comparisons, each of which are wrong in different ways, perhaps the common target feature can be highlighted?
"To put the matter this way is to engage in a bit of metaphoricalrefocusing of one's own, for it shifts the analysis of cultural forms form an endeavour in general parallel to
dissecting an organism,
diagnosing a symptom,
deciphering a code, or
ordering a system
– the dominant analogies in contemporary anthropology – to one in general parallel with penetrating a literary text."
(From 'Deep play: notes on the Balinese cockfight')
"The meanings that symbols, the material vehicles of thought, embody are often elusive, vague, fluctuating, and convoluted, but they are, in principle, as capable of being discovered through systematic investigation – especially if the people who perceive them will cooperate a little –
as the atomic weight of hydrogen or
the function of the adrenal glands."
(From 'Person, time, and conduct in Bali')
Even if this is not the case; we can expect that if the reader does mental work comparing across the multiple comparisons then this will have brought focal attention to the point being made as the reader passes through the passage of text. (Again, there is a useful theme here for any research programme on the use of figures of speech in science communication: how do readers or listeners process multiple comparisons of this kind, and does this figurative device lead to greater understanding?)
Cultural crystallisation
One recurring image in Geertz's writing is that of crystallisation.
"It is the crystallisation of a direct conflict between primordial and civil sentiments – this 'longing not to belong to any other group' – that gives to the problem variously called tribalism, parochialism, communalism, and so on, a more ominous and deeply threatening quality that most of the other, also very serious and intractable, problems the new states face…
"The actual foci around which such discontent tends to crystallise are various"
"In the one case where [a particular pattern of social organisation] might have crystallised, with the Ashanti in Ghana, the power of the central group seems to have, at least temporarily, been broken."
"The pattern that seems to be developing and perhaps crystallising, is one in which a comprehensive national party…comes almost to comprise the state…"
"…raises the spectre of separatism by superimposing a comprehensive political significance upon those antagonisms, and, particularly when the crystallising ethnic blocs outrun state boundaries…"
(From 'The integrative revolution: The primordial sentiments and civil politics in the new states')
Crystallisation occurs when existing parts (ions, molecules) that are in a fluid (in solution, in the molten state) come together into a unified whole as a result of interactions between the system and its surroundings (evaporation of solvent, thermal radiation). Some of these quoted examples might stand up to being developed as analogies (where features of the social phenomenon can be mapped onto features of the physical change), but when used metaphorically the requirement is simply that there is some sense of parallel.
An interesting question might be whether such metaphors are understood differently by subject experts (here, chemists or mineralogists for example) who may be (consciously or otherwise) looking to map a scientific model onto the author's accounts, rather than a general reader who may have a much less technical notion of 'crystallisation' but might find the reference triggers a strong image?
We might also ask if 'crystallisation' has become something of a dead metaphor: that is, has it been used as a metaphor (a comparison with the change of state) so widely that it has taken on a new general meaning (of little more than things coming together)?
Balanced and unbalanced (social) forces
Another motif that I noticed in Geertz's writing was talking about social/cultural 'forces' as if they were indeed analogous to physical forces. In the following example, the force metaphor is extended:
"In sum, nineteenth century Balinese politics can be seen as stretched taut between two opposing forces; the centripetal one of state ritual and the centrifugal one of state structure."
(From 'Politics past, politics present: some notes on the uses of anthropology in understanding the new states')
The following example also features (as opposed to crystallisation) dissolving,
"In Malaya one of the more effective binding forces that has, so far at least, held Chinese and Malays together in a single state despite the tremendous centrifugal tendencies the racial and cultural differences generates is the fear on the part of either group that should the Federation dissolve they may become a clearly submerged minority in some other political framework: the Malays through the turn of the Chinese to Singapore or China; the Chinese through the turn of the Malays to Indonesia."
(From 'The integrative revolution: The primordial sentiments and civil politics in the new states')
There seems to be another extendedmetaphor here as well, in that following dissolution, there is a danger of becoming submerged in the fluid. This quote also features the notion of 'centrifugal' force, which reappears elsewhere in Geertz's work (see below).
Canonical and alternative conceptions
I associate references to centrifugal force with the common alternative conception that orbiting bodies are subject to balancing forces – a centripetal force that pulls an orbiting body towards the centre, which is balanced or cancelled by a centrifugal force which pulls the object away from the centre. This (incorrect) notion is very common (read about 'Centrifugal force').
From a Newtonian perspective, orbital motion is accelerated motion, which requires a net force – if there was not a centripetal force, then the orbiting body would leave orbit (as, incredibly, happened to the moon in the sci-fi series 'Space: 1999' 7) and move off along a straight line. So, circular motion requires an unbalanced force (at least if we ignore the way mass effects the geometry of space 8).
Martin Landau and Barbara Bain – in 'Space: 1999' (created by Gerry and Sylvia Anderson, produced by ITC Entertainment)
I wondered whether the quote above would be interpreted differently according to a person's level of scientific literacy. Two possible readings are:
"…one of the more effective binding forces…has…held Chinese and Malays together in a single state despite the tremendous centrifugal tendencies…" because the binding forces were stronger than the centrifugal force.
"…one of the more effective binding forces…has…held Chinese and Malays together in a single state despite the tremendous centrifugal tendencies…" because the binding forces balance the centrifugal force.
The implication in the quote is that there is a steady state (if you will pardon the pun), so there must be an equilibrium of forces (that is, option 2). But, this is an area where learners will commonly have alternative conceptions: for example suggesting that gravity must be larger than the reaction force with the floor, or else they would float away; or that in a solid structure the attractive forces between molecules must be greater than the repulsive forces to hold the structure together.
"When [English A level students in a Further Education College] were shown diagrams of stable systems (objects stationary on the ground, or on a table) they did not always recognise that there was an equilibrium of forces acting. Rather, several of the students took the view that the downward force due to gravity was the larger, or only force acting. Two alternative notions were uncovered. One view was that no upward force was needed, as the object was supported instead, or simply that the object could not fall any lower as the ground was in the way. The other view was the downward force had to be greater to hold the object down: if the forces had been balanced there would have been nothing stopping the object from floating away."
Geertz was writing about society, and using the notion of forces metaphorically, but we know that when a learner is led to activate something in memory this reinforces that prior learning. For someone holding this common misconception for static equilibrium (as being due to a larger maintaining force overcoming some smaller force) then reading Geertz's account is likely to lead to:
interpreting the social example in terms of the misconception: binding forces are larger so they hold the state together;
thus rehearsing and reinforcing the prior (mis)understanding of forces!
That is, even though the topic is cultural not physical, and even though Geertz may well have held a perfectly canonical understanding of the physics, his metaphorical language has the potential to reinforce a scientific misconception!
This is not a particular criticism of Geertz: whenever a learner comes across an example that fits their prior conceptions, they are likely to activate that prior knowledge, and so reinforce the prior learning. This is helpful if they have learnt the principles as intended, but can reinforcemisconceptions as well as canonical ideas. References to a scientific phenomenon or principle that assume, and so do not make explicit, the scientific ideas, always risk reinforcing existing misconceptions. (The teacher therefore tends to reiterate the core scientific message each time a previously taught principle is referenced in class – what might be called a 'drip-feed' tactic!)
Geertz seemed to be quite keen on the 'centrifugal' reference:
"It is the Alliance…where the strong centrifugal tendencies, as intense as perhaps any state…"
"the integrative power of a generally mid-eastern urban civilisation against the centrifugal tendencies of tribal particularism".
In the following extract, Geertz has two opposed centrifugal influences:
"Yet out of all this low cunning has come not only the most democratic state in the Arab world [Lebanon], but the most prosperous; and one that has in addition been able to – with one spectacular exception – to maintain its equilibrium under intense centrifugal pressures from two of the most radially opposed extrastate primordial yearnings extant: that of the Christians, especially the Maronites, to be part of Europe, and that of the Moslems especially the Sunnis, to be part of pan-Arabia."
(From 'The integrative revolution: The primordial sentiments and civil politics in the new states')
A cursory reading might be that as these two opposed forces balance there is an equilibrium between them – but the scientist would realise this must be read as there being a strong enough cohesive force to hold the centre together against the combined effect of these forces – think perhaps of the famous Magdeburg hemispheres where two teams of forces were unable to pull apart two hemispheres with a vacuum between them (so that the pressure of air pushing on the outside spheres applied sufficient force to balance the maximum pull the horses could manage).
Engraving showing Otto von Guericke's 'Magdeburg hemispheres' experiment (Source: https://commons.wikimedia.org/wiki/File:Magdeburg.jpg)
Again, the metaphor might well lead a reader to apply, and so reinforce, their notions of forces acting – whether these notions match the canonical science account or not.
Some other scientific references.
Among the other scientific concepts I noticed referenced were
"A cockfight is …not vertebrate enough to be called a group…"
"…the intense stillness that falls with instant suddenness, rather as someone had turned off the current…"
"…that is like saying that as a perfectly aseptic environment is impossible, one might as well conduct surgery in a sewer."
"there has almost universally arisen around the developing struggle for governmental power as such a broad penumbra of primordial strife."
Sharing scientific and cultural resources
The very way that language evolves means that words change, or acquire new, meanings, and also shift between domains. If scientific terms are used enough figuratively, metaphorically, as part of non-scientific contexts then in time they will acquire new accepted non-technical meanings. We see this shift from metaphorical to widely accepted meanings in the establishment of idioms which must sometimes be quite mystifying to those not familiar with them, like non-native language speakers (Taber, 2025): understanding an idiom is not rocket science to the initiated, but the language learner might feel they've missed the boat or are having their leg pulled – and, if already struggling with the language, may consider them the last straw.
Indeed, there is a scholarly equivalent. So, I suspect many natural scientists may not know what a Procrustean bed is, or the significance of finding yourself between Scylla and Charybdis ("I'll have a chocolate and strawberry Scylla in a cone, and a bottle of 1990 Charybdis please"?), but such references are common in academic writing in some fields.
But scientists are in no position to complain when technical terms drift into figurative use in everyday language. After all, scientists are not above borrowing everyday terms metaphorically, and then through repeated use treating them as if technical terms. Certainly (as I describe in detail elsewhere, 'The passing of stars: Birth, death, and afterlife in the universe'), references to the 'births' and 'deaths' of stars are now used as formal technical terms in astronomy; but this is nothing new, for 'charge', as in electrical charge, was borrowed from the charge used in early firearms; and quarks originated in James Joyce – and calling them 'up', 'down', 'truth'/'top', 'beauty'/'bottom' and their qualities as 'strangeness' and 'charm' gave new meanings to terms taken from common usage. And having been sequestered by physics, they have then been borrowed back into popular culture again by the likes of Hawkwind and Florence and the Machine. 9
So, I have no criticisms of Geertz in using scientific terms figuratively in his writings about culture- even if sometimes those uses seem a little forced; and even if inevitably (simply because this is how human memory works) when such terms are used without definition or explication they may actually activate and reinforcealternative conceptions in those who already hold misconceptions of the science. A communicator has to draw upon the resources they have available, and which they hope will resonate (sic) with their audience in order to bring about the challenging task of sharing ideas between minds.
I read Geertz to find out a little more about his area of (social) science, but ended up reflecting especially upon how he used the language of natural science and how this might be understood by non-scientists. It has been suggested there is no privileged meaning to a text, as each reader brings their own personal reading. I do not entirely agree, at least with regard to non-fiction. There is certainly no meaning in the text itself (it is just the representation of the author's ideas and needs to be interpreted) but there is an intended meaning that the author hopes to communicate, and which the author seeks to privilege by using all the rhetorical tools available in the hope that readers will understand the texts much as intended. As every teacher likely knows: that is not an automatic or easy task.
Sources:
Change, H. (2004) Inventing Temperature: Measurement and Scientific Progress. Oxford University Press.
Clifford Geertz (2000) After the revolution: The fate of nationalism in the new states (first published 1971), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books, pp.234-254
Clifford Geertz (2000) Deep play: notes on the Balinese cockfight (first published 1972), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books.
Clifford Geertz (2000) Person, time, and conduct in Bali (first published 1966), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books, pp.360-411.
Clifford Geertz (2000) Politics past, politics present: some notes on the uses of anthropology in understanding the new states (first published 1967), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books.
Clifford Geertz (2000) Religion as a cultural system (first published 1966), in The Interpretation of Cultures. Selected Essays. 2nd Edition. New York. Basic Books, pp.87-125.
Clifford Geertz (2000) The cerebral savage: on the work of Claude Lévi-Strauss (first published 1967), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books, pp.345-359.
Clifford Geertz (2000) The impact of the concept of culture on the concept of man (first published 1966), in The Interpretation of Cultures. Selected Essays. 2nd Edition. New York. Basic Books, pp.33-54.
Clifford Geertz (2000) The integrative revolution: The primordial sentiments and civil politics in the new states (first published 1963), in The Interpretation of Cultures. Selected Essays (2nd Edition). New York. Basic Books, pp.255-310
Clifford Geertz (2000) Thick description: toward an interpretative theory of culture, in The Interpretation of Cultures. Selected Essays. 2nd Edition (1973), pp.3-30.
1 We often say exactly 100˚C, but in practice factors such as the container used do make measurable differences – (Chang, 2004) – that we generally ignore.
2 Life is not always so simple. Sulphur, for example, forms different crystal structures at different temperatures; and many metals also undergo 'phase transitions' between structures at different temperatures. But we think our theories can also explain this, so we can generalise about, say, the shape of all sulphur crystals formed below 96˚C.
3 That is, before Darwin it was widely believed that species represented clear cut types of beings where in principle clear demarcation lines could be established between different natural kinds. We now understand that even if at any one time this is approximately true (see the figure), taking a broader perspective informed by Darwin's work we find different types of organisms blend into each other and there is no absolute boundary around one species distinguishing it from others. See, for example, 'Can ancestors be illegitimate?'
The scientific perspective on the evolution of living things considers 'deep time' whereas the everyday experience of learners is limited to a 'snapshot' of the species alive at one geological moment (from Taber, 2017).
4 This is a tricky area for the science educator. Scientists should always be open to alternative explanations, and even the overthrow of long accepted ideas. But sometimes the evidence is so overwhelming that for all practical purposes we assume we have certain knowledge. There are alternative explanations for the vast evidence for evolution (e.g., an omnipotent creator who wants to mislead us) but these seem so unfeasible and convoluted that we would be foolish to take them too seriously.
When it comes to climate change, we can never be absolutely sure the effects we are seeing are due to the anthropogenic actions we believe to be damaging, but the case is so strong, and the consequences of not changing our behaviours so serious, that no reasonable person should suggest delaying remedial action. This would be like someone playing 'Russian roulette' with a revolver with only one empty chamber. They cannot be sure they would shoot themselves, so why not go ahead and pull the trigger?
Similar arguments relate to the Apollo moon landings. One can imagine a highly convoluted ongoing global conspiracy to fake the landings with all the diverse evidence – but this requires accepting a large number of incredibly infeasible propositions. (Read: 'The moon is a long way off and it is impossible to get there'.)
5 The radical poet (and engraver and visionary) William Blake:
"To see a world in a grain of sand
And a heaven in a wild flower,
Hold infinity in the palm of your hand
And eternity in an hour."
6 Even in the natural sciences, this depends upon how we think about the instrument used. If the instrument and technique are considered basic and simple and relivable, and 'standard' for the job in hand (part of the 'disciplinary matrix' of an established research field), we may not bother adding 'as measured with the metre rule' or 'according to the calibrated markings on the measuring cylinder' and then describe how we used the rule or cylinder. However, if a technique or instrument is new, or considered problematic, or known to be open to large errors in some contexts, we would be expected to give details.
7 Supposedly, according to the premise of 'Space: 1999', by 1999 the people of earth had amassed a vast stockpile of nuclear waste which was stored on one location on the moon. Even more supposedly, this was meant to have exploded with sufficient force to eject the moon from earth orbit and indeed the solar system, but without the moon actually losing its structural integrity. Just as unlikely, the space through which the moon moved was so dense with other planetary systems that the humans stranded on the moon at the time of the accident were able to engage in regular interplanetary adventures. Despite the fact that
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space."
Douglas Adams
and that generally interstellar distances are vast, the projectile moon moved fast enough to quickly reach new alien civilizations but slowly enough to allow some interaction before passing by. (It was just entertainment. Extremely long sequences of episodes where the moon just moved through very tenuous gas and the odd dust cloud, and incrementally approaches some far star, may have been much more realistic, but would not have made for exciting television.)
Actors Martin Landau and Barbara Bain (seen in the publicity shot for 'Space: 1999' reproduced above) were a married couple who starred in 'Space: 1999', having previously appeared together in the classic series 'Mission: Impossible' – which also featured one Leonard Nimoy (see below) who also famously later ventured into space as Mr Spock.
The 'Mission: Impossible' team. "No Jim, not impossible captain, just very challenging."
8 From the perspective of general relativity, an orbiting body is simply following a geodesic in the curved space around a massive body, so gravitational force might be seen as an epiphenomenon: fictitious – a bit like centrifugal force.
9
"Copernicus had those Renaissance ladies Crazy about his telescope And Galileo had a name that made his Reputation higher than his hopes Did none of these astronomers discover While they were staring out into the dark That what a lady looks for in her lover Is charm, strangeness and quark"
From the lyrics of 'Quark, strangeness and charm' (Dave Brock, Robert Newton Calvert)
"The static of your arms, it is the catalyst Oh the chemical it burns, there is nothing but this It's the purest element, but it's so volatile An equation heaven sent, a drug for angels Strangeness and Charm"
From the lyrics of 'Strangeness and Charm' (Florence Welch Paul Epworth)
An alternative conception we may share with molluscs
Keith S. Taber
A book I was reading claimed that if a winkle is placed on a rotating turntable, it would move towards the centre (much like a record stylus). Moreover, this was explained as the mollusc getting its forces confused (Brown, 1950) .
A winkle knows which way is up – unless taken for a spin, apparently.
The common periwinkle or winkle (Photographed by Guttorm Flatabø, image from Wikipedia, Creative Commons Attribution-Share Alike 3.0 Unported license).
Yet, to my reading it was the author who was getting their forces confused, as the explanation relied on a non-existent 'centrifugal' force.
Given I considered the explanation flawed, I was intrigued to find whether the phenomena was genuine. Do these animals actually head for the spindle if placed upon a rotating turntable? I expected that if this was well known I could soon confirm this with a websearch, and no doubt would find videos on Youtube or similar sites offering empirical evidence. But I could not easily find any (only that for a cost of about €7000 I could purchase a record deck where the turntable levitated when playing a disc).
Life, death and taxes?
The explanation for this claimed (and I would like to think, genuine) phenomenon related to taxes. That is not taxes of the sort which are supposedly, according to scientist and statement Benjamin Franklin, the only certainty in life apart from death. Rather the biological types of taxes, such as ther phototaxis which leads to plant shoots growing upwards although the roots head in a different direction. There are various mechanisms that allow organisms to move or grow towards, or away from, certain features of the environment that act as stimuli. Even single-celled organisms exhibit some forms of taxis.
Brown described taxes exhibited by the winkle
"The winkle … is found just above the high tide level, and it has a set of automatic movements which enable it to regain this position if, as sometimes happens it falls back into the sea. In the sea, it moves away from light (towards the rock base), and against gravity (up the rock face)."
So this organism is sensitive to and responds to gravity – something known as geotaxis, as well as exhibiting phototaxis. This behavior will have evolved over a very long period of time, as very many generations of winkles interacted with features of their shoreline environment. For nearly all of that time their environment did not include any record turntables, so winkles have not had the opportunity to adapt to the (for them) unusual context of being rotated on stereo equipment.
Who has got their forces confused?
Brown argues that in the unusual context, the winkle gets confused in the sense of misidentifying a centrifugal force for gravity:
"This complicated set of movement is entirely automatic, so that if, for example, a winkle is placed on the rotating table of a gramophone, it necessarily moves towards the centre, that is to say, against the direction of the force, and 'mistakes' the centrifugal force for a gravitational force."
But this does not make a lot of sense, because the winkle is experiencing a gravitational force as normal, and there is no centrifugal force.
A centrifugal force is one which acts on a object radially away form the centre of a circle (whereas a centripetal force acts towards the centre.) But a common alternative conception (misconception) is to identify imaginary forces as centrifugal.
For example, when an object is moving in a circle, a force is needed to maintain that motion. A winkle on a turntable is constantly changing its velocity as its direction is being shifted, and a changing velocity is an acceleration – which requires a force to be acting. This is a centripetal force which is directed to the centre of the rotation. The force deflects the winkle just enough that it does not continue to move in a straight line, but rather along the circumference of a circle. When a centripetal force is maintained, the winkle continues to move in a circle.
But a common intuition is that a object moving with circular motion is stable (after all, it repeatedly returns to the same point) and subject to no overall force. A common alternative conception, then, is that in circular motion a centrifugal (outward) force must be balancing the centripetal (inward) force. This misconception is reflected in the concept cartoon below:
Figure showing family discussing roundabout motion (photograph by facethebook from Pixabay)
The winkle is subject to gravitational force (downwards, countered by a reaction force from the turntable), and also centripetal force acting towards the centre of rotation. The (unbalanced) centripetal force provides the acceleration that causes the turntable and winkle to move in a circular motion. If there is insufficient friction between winkle and turntable to provide the centripetal force, then the winkle's inertia would lead to it sliding off the turntable – but in the direction it was moving 1, not moving off radially! There is no centrifugal force acting.
I would be interested in learning more about this phenomenon, which I had not seen referenced anywhere else. If it is true, then why does the winkle head for the centre of the turntable?
This episode also intrigued me in another way. The author was Reader in Physics at University College London, and this seems an odd error for a physicist to make (but then, we are all prone to having alternative conceptions, and even those highly qualified in a subject may be mislead by their intuitions at time).
Winkles may be like us?
But then perhaps winkles are no different to us. Someone sitting in the back seat of a car may perceive a force pushing them outwards as the car goes around a roundabout. An observer located in a helicopter above could see that this is really just their inertia – the tendency to continue on a straight line – which a centripetal force has to overcome for the car to turn. There is no outward force – even if it feels like it.
So, perhaps what Brown meant was that, like us, the winkle does get confused – it mistakes the effect of inertia for an outward force that it then seeks to nullify by heading inward. If so, then the winkle, like many humans in equivalent situations, 'confuses its forces' in the sense of mistaking its own inertia for a force?
Work cited:
Brown, G. Burniston (1950) Science. Its method and its philosophy. London. George Allen & Unwin Ltd.
Notes
1 If there was zero friction the winkle would move off the turntable in a straight line. That is not realistic, so more likely there would be some friction but insufficient to maintain circular motion, and the net force would have the winkle gradually move away from the centre of rotation till it reaches the edge of the turntable. BUT this does not mean it would leave radially (directed away from the centre) rather than tangentially (continuing in a straight line) – it would have quite the opposite effect in that the winkle would spiral out but continue to rotate at increasing distances from the centre till reaching the edge.
Plants have a mechanism to protect themselves from cold radiation
Let me begin by acknowledging I am a great admirer of Charles Darwin who surely did more than anyone else to hasten the transition from botany and zoology just being branches of natural history to becoming part of an integrated scientific biology. I wanted to make that point, because I suspect that Darwin may have held an alternative conception which will likely seem to most readers quite bizarre. I may be wrong (and am very open to be enlightened, if so) but I suspect that Darwin thought cold could be radiated – that is, that there is cold radiation just as there is, say infra-red radiation or beta radiation or cosmic radiation.
Do, as Darwin suggested, some plants have a mechanism to protect their leaves from nightime radiation?
My evidence for this is modest, but it is really the only sense I can make of something Darwin wrote. Of itself, this limited textual evidence could easily be dismissed, except I have also read things written by other historical scientists that seem to treat 'cold' as an entity in its own right alongside 'heat'. So, James Hutton (sometimes called the 'father of 'geology') referred to cold as if it was something active in itself ('we are but limited in the art of increasing the cold of bodies') and Johannes Kepler also wrote as if cold was a distinct agent in its own right ('cold will force its way through gaps') and indeed one early supporter of the chemical atom went as far as to suggest that the atoms of cold are tetrahedral.
Darwin – adventurer and recluse; and conservative revolutionary
Darwin is most famous, perhaps, for three things:
spending almost five years on a natural history collecting expedition aboard HMS Beagle after accepting the position of the Captain's companion 1 during a voyage to better survey coasts around South America;
from his observations of geological and biological phenomena during the voyage (including a lot of time he was ashore while the surveying was being carried out) coming to a new perspective on the origin of species, based on a process which facilitated evolution – natural selection;
many years later publishing his ideas in a book known as the Origin of Species.
It is often suggested that the long delay (as Darwin turned from an adventurous young man climbing volcanoes and exploring jungles, to a reclusive middle-aged family man who seldom left his home town) was due to Darwin's awareness that his theory contradicted literal aspects of Biblical faith, and would likely lead to him being labelled an 'atheist' (something largely undesirable at the time when adherence, at least apparently, to the Anglican Church's articles of faith was often considered a prerequisite for being included in polite society) and cause tensions in his otherwise loving marriage to the devout Emma (who by the time of their wedding was already worried that Charles's scientific scepticism might put his immortal soul in danger).
There is likely something in that, but the reality is not that Darwin put off sharing his work deliberately, but rather that after the Beagle returned, Darwin effectively spent the rest of his life testing and developing his ideas. He wanted to develop a water-tight and well supported argument. (Indeed, he would not have published Origins when he did, as he felt he was only part way in drafting a much more detailed account, had he not learnt from Alfred Russel Wallace that he had hit upon much the same principle as Darwin's 'natural selection'.)
His vast collections from the Beagle Voyage (that needed to be described and catalogued for publication) kept him busy enough for some considerable time after his return. He then followed up testing out his ideas against as much evidence as he could access. Darwin famously corresponded with naturalists (and gardeners and farmers and anyone who he thought could provide relevant data) all around the world, and got them to send him observations and specimens. He consulted with various scientific experts in areas where he knew his own knowledge was not cutting edge. And he carried out his own experiments at home (for example, on whether plant seeds could survive extended periods in salt water). And he wrote to a range of periodicals about his findings, as well as passing on interesting information from his overseas correspondents.
Plants move their leaves to avoid radiation
And it was in a couple of his published letters that I read his description of how some plants change the positions of their leaves (a common enough phenomenon) along with Darwin's suggestion that in certain cases plants repositioned their leaves at night to protect them from radiation. He refers to work he had undertaken with support from one of his sons, Francis Darwin. In the first letter to Nature in March 1881, Darwin Sn writes, how a correspondent of his from Brazil had written to tell him of
"…striking instances of … plants, which place their leaves vertically at night, by widely different movements; and this is of interest as supporting the conclusion at which my son Francis and I arrived, namely, that leaves go to sleep in order to escape the full effect of radiation. In the great family of the Graminere the species in one genus alone, namely Strephium, are known to sleep, and this they do by the leaves moving vertically upwards; but Fritz Müller finds in a species of Olyra…that the leaves bend vertically down at night.
Two species of Phyllanthus (Euphorbiacere) grow as weeds near Fritz Müller's house; in one of them with erect branches the leaves bend so as to stand vertically up at night. In the other species with horizontal branches, the leaves move vertically down at night, rotating on their axes, in the same manner as do those of the Leguminous genus Cassia. Owing to this rotation, combined with the sinking movement, the upper surfaces of the opposite leaflets are brought into contact in a dependent position beneath the main petiole; and they are thus excellently protected from radiation, in the manner described by us. On the following morning the leaflets rotate in an opposite direction, whilst rising so as to resume the diurnal horizontal position with their upper surface exposed to the light."
The 'us' who had previously described this kind of movement being Charles and Francis Darwin. Their theory was then that at least some plants 'sleep' at night (an interesting notion in itself), and protect their leaves from radiation by changing their position.
When I first read this I was a little confused. Certainly 'sunlight' contains high energy frequencies which can potentially damage tissues (but, of course, is also essential for photosynthesis, so avoiding the sun's radiation during the day would be counter-productive). Darwin also refers to some leaves taking positions to protect them from the direct effect of strong sunlight which makes sense if we assume that there is sometimes more than sufficient light to support photosynthesis, given strong sunlight may both cause radiation damage and encourage faster transpiration. But that was not going to be an issue at night.
Perhaps Darwin meant cosmic rays? But no, as his letter preceded their discovery by several decades. The same was true for the radioactivity found naturally in soils and the atmosphere – but even if Darwin had known about that, it is not clear how the position of leaves would make much difference. So, what kind of radiation could damage the leaves at night?
Darwin goes on to report that
"Fritz Müller adds that the tips of the horizontal branches of this Phyllanthus curl downwards at night, and thus the youngest leaves are still better protected from radiation."
This seems to suggest that whatever radiation Darwin was concerned about originated above, in the sky. A few weeks later, Darwin wrote to Nature again reporting that "FRITZ MUELLER [sic] has sent me some additional observations on the movements of leaves, when exposed to a bright light". There follow more observations on the various positions that leaves take up in some specified plants when they 'sleep' – but no more explanation of what Darwin thinks the leaves are being protected from.
So, I took a look at the book Darwin (1880) had written with assistance from Francis, about movement in plants, to see if there were any references there to 'radiation'. There it is suggested
"The leaves of various plants are said to sleep at night, and it will be seen that their blades then assume a vertical position through modified circumnutation, in order to protect their upper surfaces from being chilled through radiation."
Now, of course, leaves will radiate heat away from the plant on a cold night. Any body that is above absolute zero will radiate according to its temperature, and will consequently cool by this process if it is radiating faster than absorbing radiation (that is, in effect if it is in an environment colder than itself). Reducing exposed surface area (curling up, to reduce radiation away) or moving to be surrounded by other leaves at the same temperature (to increase absorption of incident radiation) would reduce cooling in this way: so, was this what Darwin was suggesting?
Perhaps – but this is not clear from Darwin's account. He is certainly concerned about damage done by frost when plants are exposed to low temperatures on cold nights. However, to my reading his phrasing in places seems to point less at reducing the heat emitted by the leaves, and more about avoiding or limiting exposure to radiation (of cold?) from the sky. Here are some pertinent extracts so readers can make up their own minds:
"The fact that the leaves of many plants place themselves at night in widely different positions from what they hold during the day, but with the one point in common, that their upper surfaces avoid facing the zenith [i.e., directly above], often with the additional fact that they come into close contact with opposite leaves or leaflets, clearly indicates, as it seems to us, that the object gained is the protection of the upper surfaces from being chilled at night by radiation. There is nothing improbable in the upper surface needing protection more than the lower, as the two differ in function and structure. All gardeners know that plants suffer from radiation. It is this and not cold winds which the peasants of Southern Europe fear for their olives. Seedlings are often protected from radiation by a very thin covering of straw; and fruit-trees on walls by a few fir-branches, or even by a fishing-net, suspended over them. There is a variety of the gooseberry, the flowers of which from being produced before the leaves, are not protected by them from radiation, and consequently often fail to yield fruit. … This view that the sleep of leaves saves them from being chilled at night by radiation, would no doubt have occurred to Linnaeus, had the principle of radiation been then discovered…
We doubted at first whether radiation would affect in any important manner objects so thin as are many cotyledons and leaves, and more especially affect differently their upper and lower surfaces; for although the temperature of their upper surfaces would undoubtedly fall when freely exposed to a clear sky, yet we thought that they would so quickly acquire by conduction the temperature of the surrounding air, that it could hardly make any sensible difference to them, whether they stood horizontally and radiated into the open sky, or vertically and radiated chiefly in a lateral direction towards neighbouring plants and other objects. …
But in every country, and at all seasons, leaves must be exposed to nocturnal chills through radiation, which might be in some degree injurious to them, and which they would escape by assuming a vertical position. …
…there can be no doubt that the position of the leaves at night affects their temperature through radiation to such a degree, that when exposed to a clear sky during a frost, it is a question of life and death. We may therefore admit as highly probable, seeing that their nocturnal position is so well adapted to lessen radiation, that the object gained by their often complicated sleep movements, is to lessen the degree to which they are chilled at night. It should be kept in mind that it is especially the upper surface which is thus protected, as it is never directed towards the zenith, and is often brought into close contact with the upper surface of an opposite leaf or leaflet. …
If a cotyledon or leaf is inclined at 60° above or beneath the horizon, it exposes to the zenith about one-half of its area; consequently the intensity of its radiation will be lessened by about half, compared with what it would have been if the cotyledon or leaf had remained horizontal [see my figure below]. This degree of diminution certainly would make a great difference to a plant having a tender constitution. … when the angular rise of cotyledons or of leaves is small, such as less than 30°, the diminution of radiation is so slight that it probably is of no significance to the plant in relation to radiation. For instance, the cotyledons of Geranium Ibericum rose at night to 27° above the horizon, and this would lessen radiation by only 11 per cent.: those of Linum Berendieri rose to 33°, and this would lessen radiation by 16 per cent."
I am not sure what to make of this. In places it seems clear that Darwin knows it is the leaves that are radiating away heat. Yet he makes much of the angle to the open sky, as if the leaves need protecting from something originating there. Changing the angle of a leaf from the horizontal would certainly reduce the surface area exposed to any radiation from above, but in itself makes no difference to the intensity of radiation emitted by the leaf. So, in places, the treatment seems based on the leaf's assumed exposure to incoming radiation rather than on any factors that might reduce the heat emitted.
Darwin thought that a plant could reduce potential damage by radiation on a cold night by re-orientating its leaves to reduce the surface area exposed to the sky above.
Of course, Darwin was not a physicist, but he was widely read and a deep thinker. He seems to be reporting a mechanism by which plants might be protected from the effects of low temperatures by repositioning their leaves – but his explanation in terms of radiation does not seem to work. If he is referring to the leaves radiating (and in some places, that certainly seems to be the case), then repositioning of the leaves does not of itself directly change that (though it might, for example, move them nearer the ground where the air may be not so cold); and if the critical factor is the apparent area of exposed leaf from directly above the plant, then this suggests a concern with something (cold?) radiated from the sky above – as the leaf will continue to emit the same level of radiation regardless of its relative angle to the sky.
Perhaps my difficulty in making sense of Darwin's explanation here is because his thought was in a kind of transitional or hybrid state? We see this in historical accounts of the development of science, and also in the classroom as learners undergo conceptual change (as, for example, when having learned that ionic bonding is the effect of lattice forces between oppositely charged ions, but still thinking that an ionic bond was a transfer of an electron from one atom to another).2 The French philosopher (and former school science teacher) Gaston Bachelard argued that scientists inevitably retain in their thinking vestiges of historical scientific notions that have nominally been refuted and discarded.
The mechanisms that Darwin describes might indeed reduce the NET thermal radiation from leaves, despite the radiation emitted being unchanged, if repositioning leaves increased the amount of radiation absorbed. (Positioning leaves in warmer air, or in positions better protected from cold breezes, will have reduced losses – but not by reducing the amount of radiation emitted.3)
Darwin seems aware that the (relatively warmer) leaves radiate away heat in the cold night, but at some level he seems to hold a vestige of an earlier historical notion (from a time before temperature was understood in molecular terms), and when it was common to understand phenomena in terms of contrasting qualities and properties (hot-cold and wet-dry being critical opposites in archaic ideas about the elements, the heavenly bodies, and medicine). So, at one time, levity was seen as property in its own right, acting in an opposite way to gravity; and rarity considered as a property in its own right having an opposite sense to density. So, thinking of cold as an entity (not just a lack of heat, or a low temperature) which had active effects fitted in a long-standing tradition of thought.
Even if Darwin did not actually, explicitly, think cold existed as something that could be radiated in its own right, his account of the importance of leaves changing their angle to sky above them on a cold night does certainly seems to have vestiges of a notion of cold as an active agent radiating down from above.
Work cited:
Darwin, C. (1881). Movements of plants. Nature, 23 409.
Darwin, C. (1881). The movement of leaves. Nature, 23, 603-604.
Darwin, C. with Darwin, F. (1880) The Power of Movement in Plants. London: John Murray.
Note
1 Although Darwin acted as a ship's naturalist, this role would normally have fallen to the ship's surgeon. Captain Fitzroy wanted someone who he could dine with, and engage in intelligent conversation, and by social convention at the time this should be someone of the right status – a gentleman. This was likely a sensible precaution on such a long voyage (even without knowing with hindsight that much later – after Governing New Zealand and establishing weather forecasts – Fitzroy would commit suicide). One might wonder whether none of the other officers on the ship came from a 'suitable' background; but a good Captain was probably also aware of the risks for maintaining ship's discipline of fraternizing with members of his crew.
2 See for example: Taber, K. S. (2000) Multiple frameworks?: Evidence of manifold conceptions in individual cognitive structure, International Journal of Science Education, 22 (4), pp.399-417. https://doi.org/10.1080/095006900289813 [Download this paper]
3 For example, if two (relatively warm) leaves move to have their surfaces adjacent, then each will absorb some of the radiation emitted by the other, reducing each leaf's net heat loss. If a leaf is in a breeze then the air around it is constantly being renewed, whereas in still air the warmer leaf will raise the temperature of the surrounding air, and although diffusion will still slowly occur, this warmer air will offer some level of insulation.
Many undergraduates seem to think molecules like to hang around rather than moving on
Keith S. Taber
A representation of a small part of a layer of molecules in a solid substance – with one molecule highlighted by colour. If the solid were melted, and then refrozen, where would the highlighted molecule be?
If you are a science teacher: what would your students think?
In this article I offer my own version (actually two versions, see below) of a question I saw used in a published study (Smith & Villarreal, 2015a). As I no longer have any students, I cannot easily try this out, but perhaps a reader who is currently teaching science might be tempted to see what their pupils or students might think? (If you do, I would apreciate hearing about what you find!)
The two versions of the question can be downloaded from the links below.
The question could be given to individual learners, or as the basis of small group discussion, or perhaps just projected onto the screen for a 'show of hands' for each response option. (Exploring student thinking to detect misconceptions is known as diagnostic assessment.)
Alternative conceptions abound
I am very familiar with the extensive evidence which shows that is very common for learners, at all levels, and in any topic, to hold alternative conceptions ('misconceptions') at odds with canonical science and the target knowledge set out in the science curriculum. So, I am seldom surprised when I read about a study which reports finding learners demonstrating such conceptions.
Yet one study I read which reported learners commonly holding an alternative conception did surprise me. I would have not been surprised if the respondents had been secondary levels students, and a minority of them had demonstrated this particular conception, but I would not have expected how the study found a high incidence of the alternative conceptionamong undergraduates studying chemistry.
The research asked about what happens when a solid is either dissolved, or melted, and then returns to the solid state. It used an instrument that presented a figure representing the particles in a small section of a solid, with one particle marked out, and asked the learners to draw the equivalent images after the solid had either dissolved and then been recrystallised, or melted and then been refrozen.
I an going to limit myself to the easier context (melt, then freeze – no solvent molecules involved). According to the researchers, the results suggested that a large proportion of the undergraduates indicated that the atom that had been marked out would be found in the same position in the solid at the end of the process: the exact proportion shifted in two versions of the study (65%, 50%) but a very rough gloss was that at least half of the learners located the marked particle back at its original point.
"These results indicated that a large proportion of the students viewed the [marked] molecule as being near to the same position after melting as it was before melting, and being in the position it was originally in after the liquid froze back to the solid."
Smith & Villarreal, 2015a: 277-278
Perhaps this should not have surprised me – I have been told by very bright A level students that on homolytic bond fusion each atom would always get its own electrons back, and this seems something of a parallel notion.
Now there was some questioning of the methodology and instrument used here (Langbeheim, 2015; see also Smith & Villarreal, 2015b) – as there often is in educational research – but it seemed a substantial proportion of learners thought the solid would reform with particles in their original positions, and this suggests a rather limited understanding of the level of molecular motion in the dissolved or molten state. I would not have been so surprised if this work had been carried out with, say, twelve year olds – but such a high level of misconception among undergraduates did surprise me as it reflects a failure to imagine the nature of the molecular world, and that surely makes learning high level (e.g., degree level) chemistry very difficult.
Now there are serious challenges in representing the nanoscale (thus the questioning of the representations used in the study) simply because molecules, ions, electron, atoms – are not the kinds of things we can draw realistically – they are fuzzy objects with no surfaces that somewhat blend into their neighbours. This raises a possible defence for students in such studies
'yes, your honour, I did show the particle as having returned to the same position, but as the focal figure had been drawn unrealistically as a set of circles I did not think authenticity was being asked for!'
It seems unlikely any learner really did think that – and the researchers did ask learners about their reasoning. The most common type of explanations were (Smith & Villarreal, 2015a: 278):
In the molten state: The molecule doesn't move far from its original position
After resolidification: The molecule ends up near where it was positioned in the liquid
Representing quanticles
Molecules, ions, atoms are 'quantum objects' which do not have the properties of familiar macroscopic objects. The nanoscopic particles in a lattice or liquid are not like the particles in table salt (grains) or sugar (granules) which each have a definite volume and surface, and which cannot be made to overlap their neighbours.
The following is my representation of a section of a layer of molecules in a solid substance. I have shown them round as that is simpler. Most molecules are not round (but 'molecules' of, say, neon or argon, are.) I have tried to show them as being fuzzy rather than as if ball-bearings with definite surfaces as the 'substance' of atoms, ions and molecules is largely electric fields and electron 'clouds' (a rather appropriate metaphor) rather than anything 'solid'. (And, of course, the word solid loses its meaning for a single molecule. We might, figuratively, suggest the atom is like a tiny liquid drop surrounded by an immense volume of gas – but it is probably best to avoid using such comparisons with learners becasue of the potential for them taking the terms literally.)
Should the molecules be touching in the solid? That is a problematic question as how do we decide whether things are touching when the things concerned do not have distinct surfaces but rather fade away to infinity? (If the gas giants Jupiter and Saturn were to ever come together, how would we decide at what point they had actually physically collided?)
Often in science teaching we cheat and show molecules touching in solids when teaching about the differences between condensed and gaseous states; but then hope students have forgotten this by the time we want to teach about thermal expansion of solids.
My diagram shows a layer of the regular crystal structure, so if you think my 'molecules' should touch then you can imagine that they would once the adjacent layers were drawn in.
The image I have used might suggest too much space between molecules…
…adding another layer might help give the appearance of close packing, but if a different colour is used this may suggest some physical difference…
yet making both layers the same colour makes the figure more dificult to interpret.
It is a problem of scale
The real issue for the novice learner here is one of scale. The scale of atoms is far beyond our ready grasp. My figure shows a much more extended section of material than that in the original study – but still, a tiny, tiny, tiny fraction of a solid we could readily see and manipulate. If the solid substance melted, then (e.g., around room temperature) we would expect molecular speeds of the order of hundreds of metres per second. In the gas phase that might be somewhat reflected in how far some molecules get (but diffusion is still much slowed by collisions), but in a condensed phase, so in a liquid, the molecules are not going to get very far at all before colliding with a 'neighbour' and being deflected off course.
The so-called 'random walk' of any molecule in a liquid will reflect mean speeds orders of magnitude less than the hundreds of metres per second instantaneous speed (as it is constantly being shifted to a new direction, and is just as likely to be sent back in the direction it originated).
But then, given the size of the sample represented, the distance from one end of the image to the other is of the order of maybe 0.000 000 001 metres. If a molecule with an instantaneous speed of hundreds of metres per second only has to travel of the order of perhaps 0.000 000 000 1m before colliding with the next molecule, it is going to have an awful lot of collisions each second – many billions. So, a molecule bumping around at say 300 m/s would not take very long to move 0.000 000 001 m (and so off the region of lattice shown in my figure) even with all those restrictive collisions!
Two versions of the diagnostic question for use in class
Even if the solid melts and is a liquid for only a few minutes (that is, a few hundred seconds), and even if we have placed the original solid in a tightly constricting container such that the liquid does not change overall shape, what are the chances of the molecule ending up in the same lattice position? Or even being in the frame when we represent such a small section of the lattice?
If we are only representing one layer of molecules, then what are the chances of the molecule even ending up in the same layer (it is likely to have moved 'up'/'down' just as much as laterally along the plane represented whilst in the liquid state).
Each of the options (in both versions of the question) are possible outcomes.
Given that the section of the latice shown is so limited, all the positions shown are pretty much local to the starting point, so I would argue the molecule could almost equally likely end up in any of the lattice positions in the figure (so: A, C and D are, in effect, equally likely – as would be any other lattice position you selected from the image).
What about Option B?
Option B reflects all the possibilities where the molecule ends up outside the small section of lattice layer illustrated, including all the options where it has moved to a different layer. There will be billions and billions of these options, including, at least, many thousands of options close enough for the molecule to have easily moved there in the number of 'random walk' steps feasible in the time scale.
So, the answer to the question of which option is most likely (in either version of the question) is easy – option B is by farmost likely.
But I wonder if most students who have been taught about particle models and states of matter would agree with me? If Smith and Villarreal's undergraduate sample is anything to go by, then I guess not.
Work cited:
Smith, K. C., & Villarreal, S. (2015a). Using animations in identifying general chemistry students' misconceptions and evaluating their knowledge transfer relating to particle position in physical changes [10.1039/C4RP00229F]. Chemistry Education Research and Practice, 16(2), 273-282. https://doi.org/10.1039/C4RP00229F
Langbeheim, E. (2015). Reinterpretation of students' ideas when reasoning about particle model illustrations. A Response to "Using Animations in Identifying General Chemistry Students' Misconceptions and Evaluating their Knowledge Transfer Relating to Particle Position in Physical Changes" [10.1039/C5RP00076A]. Chemistry Education Research and Practice, 16(3), 697-700. https://doi.org/10.1039/C5RP00076A
Smith, K. C., & Villarreal, S. (2015b). A Reply to "Reinterpretation of Students' Ideas when Reasoning about Particle Model Illustrations. A Response to 'Using Animations in Identifying General Chemistry Students' Misconceptions and Evaluating their Knowledge Transfer Relating to Particle Position in Physical Changes' by Smith & Villarreal (2015)" [10.1039/C5RP00095E]. Chemistry Education Research and Practice, 16, 701-703. https://doi.org/10.1039/C5RP00095E
Alternative conceptions underpin some, but not all, learning difficulties
Keith S. Taber
I recently wrote here about a paper published in a research journal which used a story about the romance between two electrons, Romeo and Juliet, as a context for asking learners to build models of the atom. (I thought the approach was creative, but I found it quite dificult to decode some aspects of the story in terms of the science).
But something else I noticed about that study (Aquilina et al., 2024) was that the authors listed a number of 'misconceptions' that their teaching approach was meant to address (see the Table reproduced above). These were:
Students, after studying planetary and Bohr's atomic models, cannot move beyond them easily.
Students rarely reflect on and/or understand the need for the development of new atomic models.
Students find it difficult to associate spectral lines with transitions between energy levels.
Students do not describe photon emission processes properly.
Students do not clearly understand the concept of an orbital.
Students find it difficult to understand atomic quantum-mechanical models.
There is a very large literature reporting student misconceptions, or alternative conceptions, in science subjects.1 A misconception, or alternative conception, is a conception that is judged to be inconsistent with the scientific account (or the version of the scientific account presented in the curriculum). The points listed in Aquilina and colleagues' table are not conceptions, so cannot be alternative conceptions – just as a postbox cannot be a red car, because it is not a car; and nor can Boyle's law be a refuted theory, because it is not a theory; and a mushroom cannot be a leafless plant, because it is fungi not plant.
So, what is a conception?
We might understand a conception to be one facet of a concept (Taber, 2019). Consider a student has some ideas about atoms. We might consider the learner's concept of the atom to be the collection of all those ideas about atoms. Imagine a learner thinks:
atoms are very small
an atom contains a nucleus
atoms contain electrons arranged in shells
there are many different types of atoms
gold atoms are gold coloured
everything is made of atoms 2
an exploding atom can destroy a city
If this was the full extent of their ideas about atoms, we might collectively see this list as comprising their atom concept. We could represent it by drawing a concept map showing how the learner sees 'atom' to be linked to other concepts such as 'nucleus', 'electron', etc.
But we might consider each one of these separate statements to be a conception.
Our conceptions vary across a number of dimensions (after Figure 2.3 in Taber, 2014)
There are complicatons:
A person may have (implicit / tacit) 'conceptions' that they could not easily put into words to express as statements. (A researcher might elicit what a learner is thinking and represent it as a sentence, but for the learner it may be more a vague intuition that they only put in words in response to the researcher's questions.)
A person may also show different levels of commitments to conceptions – perhaps our hypothetical learner is pretty certain that atoms are very small, but only has a hunch that gold atoms are gold coloured. Perhaps the learner was told by a friend that an atom bomb that is powerful enough to destroy a city is based on exploding a single atom at its centre – and our learner remembers this, but is actually very sceptical.
We usally say a learner has an alternative conception when they hold a conception which is inconsistent with (so alternative to) the scientific account. A great many such alternative conceptions have been elicited in research that explores people's thinking about science. Much of this work has been undertaken with science learners, but some simply with people in the general population (when alternative conceptions may be termed as 'folk science' or 'urban myths'). Here are just a few of the examples discussed elewhere on this site:
These are 'alternative' because they are contrary to the scientific account, and they are significant to science teachers because they are contrary to the target knowledge the teacher is expected to teach to students.
One reason to perhaps prefer the term 'alternative conception' to 'misconceptions' is that the latter term may seem to imply the outcome of misunderstanding teaching. Alternative conceptions certainly can be linked to misunderstanding teaching, but often this occurs because the learner already has an intuitive idea that is contrary to the science, and this leads to them misinterpreting teaching. But consider this example:
an atom of an element in the first period has a full shell with two eletrons, all other atoms would need to have eight electrons in the outer shell for it to be a full shell
This is an alternative conception that learners sometimes do hold, whereas eight electorns only counts as a full shell in period 2 (Li, Be, B, C, N, O, F, Ne) and not for any of the other elements. So, a chloride atom (electronic configuration 2.8.7) does not have a full outer shell when it joins with an electron to become a chloride ion (2.8.8).
But I have seen school textbooks aimed at secondary levels learners (c.14-16 year old students) that actually state quite clearly that all atoms, apart from H and He have a full outer shell with eight electrons. If a learner had read that in the textbook issued by the school, and so believes it to be so, then they have not misconceived what they read – they have accurately understood the intended meaning. But it is still an alternative conception ('misconception').
Learning blocks and misconceptions
So, something cannot be an alternative conception (misconception), unless it is both a conception, and counter to the scientific account. But there are other reasons a learner may struggle to understand the science in the curriculum.
A learner may lack specifc prerequisite background knowldge needed to make sense of a new idea; or the learner may not appreciate that cetain prior knowledge is meant to be applied in understanding the new material. Learners may indeed misinterpet teaching due to an existing alternative conception, but they may also sometimes make an unhelpful association with unrelated prior learning. (That is, they interpet teaching in terms of some prior learning that they think is related, but which from the scientific perspective is not relevant.) Sometimes that may relate to how scientific terms may be understood through the learner's language resources (such as assuming a 'neturalisation' reaction will always lead to a neutral product becasue that's exactly what a reasonable person might expect 'neutralisation' to mean!) or it may relate to not appreciating the limitations of a teacher's model, or to how an analogy or metaphor (e.g., electron shell) is intended to be figurative, not literal.
Learners may not always understand teaching as intended
So, alternative conceptions are indeed very relevant to the challenge of teaching science, but not all learning difficulties are due toalternative conceptions; and certainly not all learning dificulties should be labelled as 'misconceptions'.
Beyond misconceptions
So, what about Aquilina and colleagues' list of supposed 'misconceptions'?
Students, after studying planetary and Bohr's atomic models, cannot move beyond them easily.
Students rarely reflect on and/or understand the need for the development of new atomic models.
Students find it difficult to associate spectral lines with transitions between energy levels.
Students do not describe photon emission processes properly.
Students do not clearly understand the concept of an orbital.
Students find it difficult to understand atomic quantum-mechanical models.
There are a number of well-recognised issues here. Two in particular stand-out.
The unfamiliar abstract
For one thing the subject matter is unfamiliar and abstract. People can only understand teaching if they can link it to existing experience or prior learning. Teachers have to find ways 'to make the unfamiliar familiar'. (This is why Aquilina and colleagues devised a narrative based on a tragic love story that they expected the students to be familiar with.)
But learning about the abstract in terms of the familiar only moves a learner so far when the familiar is only a little like the target. Learners know about shells, so can imagine electrons in shells – but electron shells are not really like more familiar shells (such as those that protect snails and cockles or bird's eggs). Learners can imagine electrons spinning like spinning topics, but electron spin is not like that – the electron does not spin.
The behaviour of quanticles, quantum objects, is quite unlike the behaviour of familiar objects. An orbital is not really an object at all, but more a description of the solution of a mathematical equation – those diagrams showing the different atomic or molecular orbitals are a bit like the map of the London underground: schematic representations that are useful for some purposes, but not realistic images of the orbital/rail line.
Acquiring model nous (epistemologial sophistication)
The second issue relates to epistemological niavety, which comes from not appreciating the subtle nature of science. If we teach students that an atom is like THIS (say, electrons orbitting a central nucleus like planets orbiting the sun), why shoud we then be surprised that students think that is what an atom is like – and so then struggle to understand why we are now teaching them the atom is quite different from this? The defence that we did point out this was a model is only convincing if we are sure the students understood what a scientific model is.
We might describe thinking that electrons in atoms have definite trajectories as being a 'misconception' – but if we have taught such a model then the learner's real misconception is in thinking that such a model is meant to be a realistic representation. If we never taught them that the model was something other than a scale replica of an atom, then this is a 'pedagogic learning impediment'. That is, the student is only guilty of learning what they have been taught!
Perhaps more attention to this aspect of the nature of science throughout school science might avoid this problem. Imagine that from a young age learners had regularly been asked in their science lessons to:
devise different models and representations of various scientific phenomena
identify the strength and limitations of different models (both those produced by learners, and mulitpile representations presented by the teacher)
discuss why having several different (imperfect) models might sometimes be useful
be asked to choose between alternative models/representations for different specified purposes
In contexts where science has tended to be taught as though it offers a single, realistic account of phenomena, then we should not be surprised
that students do not see the need to move beyond the models they have been taught (they consider them as more like scale replicas than theoretical models)
nor indeed when they complain they have put a lot of effort into learning models they now feel they are being taught were wrong all along!
Learners' alternative conceptions are a major impediment to learning school and college science. However, learning of abstract ideas requires learners to make sense of teaching in terms of the interpetative resources they have available – and that is often challenging enough even when they have no existing alternative conceptions in a topic.
Aquilina, G.; Dello Iacono, U.; Gabelli, L.; Picariello, L.; Scettri, G.; Termini, G. "Romeo and Juliet: A Love out of the Shell": Using Storytelling to Address Students' Misconceptions and Promote Modeling Competencies in Science. Education Sciences, 2024, 14, 239. https://doi.org/10.3390/educsci14030239
Taber, K. S. (2014). Student Thinking and Learning in Science: Perspectives on the nature and development of learners' ideas. New York: Routledge.
Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Cambridge: Royal Society of Chemistry.
Notes:
1 There are a number of other related terms used in the literature, such as intuitive theories and preconceptions. Sometimes these different terms refect subtle distinctions (so preconceptions refers to alternative conceptions a learner has prior to being taught anything about a topic). But, in practice, there is no real consisitency in how various terms are used across different authors.
I try to reserve the term alternative conceptual framework for more large scale conceptual structures than discrete alternative conceptions. (But again, the terms are sometimes used interchangeably) So, for example, the 'octet' framework is a network of related conceptions built around the core alternative conception that chemical change is driven by atoms needing full electron sells or octets of electrons:
2 A teacher might want to ask students what they means by their words. If a student suggests they believe that everythings is made of atoms, or everything is made from atoms, then this may be a canonical understanding, or an alternative conception:
all material substances found under normal conditions can be shown to contain atomic cores surrounded by electrons
if we could examine all materials we would find they are comprised of lots of discrete atoms just stuck together
everything is made from atoms
we can envisage that any substance could be built up by chemiclly joining together a certain number of atoms of various elements – all molecules and other structures can be imagined as being built up from atoms
chemical reactions produce different substances by starting with lots of atoms of the relevant elements
An opinion piece in Education in Chemistry by Kristy Turner recently highlighted the potential bias that may lead to scholars being more likely to access, read and cite research from some parts of the world than others. This was actually an issue I was very aware of when a journal editor, as an international journal should aim to reflect research globally, but needs to apply common quality criteria.
This means that those working in contexts where there are no traditions of educational research, and limited resources to develop capacity, are at a disadvantage. I could think of one country where the journal received regular contributions, but which were almost always rejected (perhaps, always rejected?), as they simply did not amount to substantive accounts of research. These included well-intentioned, if sometimes quite convoluted, suggestions for mnemonic schemes to teach abstract conceptual subject matter, which offered absolutely no evidence that the proposed approach had ever been evaluated (if, indeed, ever applied). I was aware that any simple calculation of success rates in the journal would show that submissions from this particular national context had no chance of publication, and that few indeed ever got as far as referees 1. This might look like prejudice, even if it reflected application of the same quality criteria to all submissions. 2
On the other hand, the situation is slowly shifting. An excellent example is Turkey, which transformed from being a virtual non-participant in science education research publication to one of the most productive national sources of research published in the top journals, in just a couple of decades. I am aware of several other countries that are, if more slowly, supporting similar development in science education. So, the situation is complex: but Turner is absolutely right that we need to also be aware of a possible mind-set that assumes useful, quality research in science education will only be going on in a limited number of national contexts.
Being classified by the colour of my skin
But what really made me reflect on the piece was was not this important point, but that I was name-checked at the start of the article, along with a number of other educational research scholars, before Turner asked:
"What do these names have in common?
To start with they are all men and all White. More significantly, they all worked in the West (although some had collaborations further afield). This means that much of the education research we consume is produced from a Western perspective."
Turner, 2023
I am not sure I have ever seen myself called out in this public way as being "White", and I was not sure I was comfortable with being labelled in this way. For me, this was a mild discomfort – the kind that usefully leads one to reflect. By contrast, many people in this world experience being referred to by colour labels every day of their lives.
I readily identify as English, British and European, as simply a matter of fact: so, I suppose, 'Western' – guilty as charged. I have no qualms about being publicly labelled as a man. (Though I had no problem with being called 'Miss' by new secondary school students just moving up from primary schools where their class teacher had been 'Miss'. The pupils tended to be more embarrassed than me on these occasions – as was the tutee who once inadvertently called me 'Dad'. Yes, Tamsin, I still remember that.)
When I went to school, the world (at least as it was usually talked about) seemed simple in that regard. Humans came in two types – males and females. In my class in school there were boys and girls, and there was absolutely no ambiguity about this, and the difference was clearly marked: the boys wore shorts, the girls skirts or dresses. When I got to secondary school I studied metalwork and woodwork and technical drawing, whilst the girls studied their own subjects such as cookery. (Yes, I am that old.) Science dichotomised people into these classes of males and females (this was strictly known to be a simplification, but I do not recall any mention of other possibilities when I was a child), and there was a widely assumed perfect correlation with gender.
Of course, we now know this is utterly simplistic, and if such a regimented approach is imposed on people it is a burden that does not reflect the range of ways that people themselves experience their lives. It is now very common for people to attach their preferred pronouns to their web-pages and emails footers, and we appreciate that people have a right to self-identify in gender terms, and should not be assigned such an identify from the outside.
Original image by Krzysztof Niewolny from Pixabay
Should what is good for the goose also be good for the gander?
So, if we respect people's right to claim their own gender identity, what gives us the right to assign them to 'colour' categories? These categories were historically linked to what many scientists considered distinct varieties of human being – the different 'races'. That is, just as scientists might have recognised different varieties of a species, say different breeds of sheep, so there was considered to be a substantive and biologically justifiable basis for classifying people as members of different 'races'.
Those classifications were also not just seen as categorical, but often as ordinal – there were not only considered to be different races, but some of them were widely thought of (*) as more advanced, more civilised, perhaps even more evolved, than others; and it sometimes followed to many people that members of some races were of more inherent worth than others. (* At least, this was a common stance among people who self-identified as White!)
As is well known, this attitude led to many terrible events, and such bizarre notions as long-inhabited lands being 'discovered' by newcomers who therefore felt entitled to take possession of them: perhaps because they did not consider the inhabitants worthy of land and resource ownership; or perhaps because often the indigenous population took an attitude to the land and biota that it was not open to their ownership, but rather was sacred and deserving of being seen as in a form of relationship, rather than just being a source for exploitation. (That is, in many senses, the supposed 'more primitive' people had a more sophisticated and ecologically viable Worldview than those making the comparisons and seeing themselves as 'more civilised'.) That was one historical form of the 'Western perspective' that Tuner rightly warns about. 3
Science progresses: but not everyone keeps up
Science has moved on. We now know that, from a scientific perspective, there is only one human race. We all descend from early human ancestors that lived in Africa – so, for example, all of us in Britain are, if not ourselves migrants, ultimately the descendants of African migrants.
There are no strong categorical differences that allow us to form clear-cut classes of people (such as we can nearly dichotomise sex, even if we now realise that does not correlate to gender in a simple, direct way). Certainly, there are differences in populationsthat have long lived in different parts of the world: some groups are more likely to be lactose intolerant; more likely to suffer from, or be resistant to, specific diseases, and so forth. But these are statistical differences, not absolute ones.
An analogy for categorising people into 'races' based on physical characteristics (original image by Mote Oo Education from Pixabay)
To divide people into racial groups on that kind of basis makes as much sense as dichotomising adult people into males and females purely on height (i.e., the tallest 50% are male, by definition) simply because there is a statistical correlation between biological sex and adult height. Throughout human history, there has been social and genetic interchange between populations, and that is now more so than ever. We all have a mix of genes from a diverse range of ancestors – indeed most of us have few percent of genes that are considered Neanderthal. 4 So being 'White' is not simply a matter of genetics: any notion of a pure European genome is simply fantasy, akin to the deluded Nazi fantasies of Aryan blood lines. 5
Race is not a biological classification. Race is a socialsystem of categorising people, not a scientific system. There are different races in the world only in a similar sense to how there are different styles of art or architecture in the world, or different modes of fashion (or styles of music, or genres of literature): because people have constructed such a system and imbued certain perceived differences with significance. But, there are not races in the world 'naturally' in the sense that there are different elements or different minerals out there for scientists to find. 6
The idea of several distinct human races can be seen as a historical scientific concept that was once given serious credence (just like phlogiston, or the luminiferous æther), but today should be seen as an alternative conception – a bit of folk-science that is actually a misconception.
So, if I am seen as White, this is because I have certain physical characteristics that others perceive as being 'White' (i.e., physiognomy). Presumably skin colour is a primary factor, although I certainly do not have white skin (I have never seen anyone who actually looks white or black, and suspect this choice of labels is in part a reflection of the historical associations of these colours 7). I am basically a pink colour, although at certain times of year I go somewhat orange. I am not being flippant here – I am obviously of pale skin tone as would be associated with someone of European descent. But, again, we know that skin tone does not simply divide into a few clear categories: there is a whole spectrum out there, and most of us do not have entirely even pigmentation over all parts of the body, and/or are subject to some variation depending on environmental factors (and in England the average potential exposure to the Sun's rays in June is VERY different to in December!)
Now, I am not suggesting there might not be times when pointing out the colour of someone's skin might be useful – it might be very relevant in giving a description of a missing child or a mugger. But, Turner was not calling me White to help you recognise me, but to label me as someone associated with a 'Western' perspective. This of course is not a perfect correlation either. (I suspect that Rishi Sunak and Barack Obama would be widely considered to have Western perspectives).
'I hate the White man'
The musician Roy Harper wrote a song called 'I hate the white man' which appeared on his 1970 album 'Flat Baroque and Berserk'. He sings it live with real venom. When I first heard this song, it seemed strange to me, as here was a white man [sic, my label] singing how he hated the White man. It was heartfelt, but it seemed ironic. It did not occur to me that I was just assuming Roy was White because he looked white to me. (He is 'obviously' white, just as I, apparently, obviously am – that is, his skin tone is pinkish.) I never entertained another possibility: the notion that he should have the right not to identify with the people who's crimes he was singing about; that is, not to identify as a White man.
So, should I be able to opt out of being put in an unscientific, racial category? Can I decline being White, and simply be a global citizen, a member of the human race, and so deserving the same level of respect and the same human rights as any other?
A dilemma
Of course it is not that easy. It is all very well someone like me refusing to self-identify with a racial label: there is still much discrimination and even targeted violence in many part of the world against people on racial grounds, and that would not be stopped by any personal self-identification of the victims. It is the perceptions of the abusers that matter in such situations, not how those on the receiving end see themselves. The Nazi's decided for themselves who was Jewish and so who deserved to be, say, removed from academic posts, or even incarcerated and exterminated, without regard to, for example, the victim's professed religion or record of Christian Church attendance.
Moreover, even if there are no strong genetic grounds to classify humans into a small number of 'races', the science of epigenetics is starting to reveal the cross-generational effects of extreme life-experiences (Meloni, 2019) such as slavery. The descendants of oppressed and impoverished people will continue to suffer relative to others for several generations. There may be no moral basis for asking children to pay for the 'sins of the fathers', but children of heavily sinned-against parents will still be at a disadvantage in life. That is not all about 'race': it might be about class, or the effects of war, but often racial identity (something with real effects, even if no scientific justification) can certainly be a factor.
If we do not identify with ethnic groups, then this makes monitoring of bias and discrimination difficult. How does an organisation know it is being equitable in relation to ethnic diversity, if no one chooses to self-identify with the traditionally majority, and/or privileged, groupings?
I think there is a genuine conundrum here. I look forward to the day when no rational person would see physiognomy as a useful basis for unscientifically classifying human beings, and, even if I am unlikely to live that long, hope we continue to move in that direction. But I understand why minority and oppressed groups find solidarity in such identification, and I appreciate the need for monitoring progress towards a fairer and more equitable society. So, Kristy, I fully understand why you call me 'White', even if I feel a little uneasy being labelled in that way.
Work cited:
Meloni, M. (2019). Impressionable Biologies: From the archaeology of plasticity to the sociology of epigenetics. Routledge.
Szöllösi-Janze, M. (2001). National Socialism and the sciences: reflections, conclusions and historical perspectives. In M. Szöllösi-Janze (Ed.), Science in the Third Reich (pp. 1-34). Berg.
1 Submissions to a research journal normally undergo editorial screening, so that (unpaid, expert) referees are not asked to spend time evaluating material in peer review that is out of scope for the journal or clearly inadequate (e.g., an empirical study lacking a methodology section).
2 I did highlight this issue at the journals' editorial board. The journal itself could do little about solving the problem, but the wider community might find ways to support development of research capacity in contexts where science educators aspire to be publishing work in international research journals.
3 Without in any sense wishing to undermine the terrible consequences that followed from widely held perceptions of racial differences, this can be seen as part of the wider commonplace phenomenon of categorising humans into various groupings in ways that are then used to justify treating some people as less worthy of respect and rights as others – for example the torture and judicial murder of Catholics/Protestants by Protestants/Catholics in parts of Europe when, sometimes, different members of the same nuclear family were classified into different groups.
4 It is sometimes said that on average a person has about 2% of Neanderthal DNA. Given that all the biota on earth is considered to ultimately have a common descent it is of course not surprising that human beings share some genes with, say, chimpanzees, and for that matter, bananas. However, it is not considered humans have chimpanzee ancestors (or banana ancestors, of course) but rather the two species evolved from a common ancestor population.
The particular interest in Neanderthal genes (and genes from Denisovans) is that it is considered that extant human populations carry genes acquired from Neanderthals when the two different populations co-existed, not from some precursor species they both evolved from. Whilst this is still an area of active research, the findings are widely interpreted to suggests that humans sometimes interbred with Neanderthals.
5 The Nazis thought that the German Volk descended from a distinct, discrete race, the Aryans – and set up scientific research projects to explore and develop the idea. Some of the ideas involved seem incredible:
"…Himmler rejected the Darwinist theory of evolution for the Aryans, presenting instead phantasies, according to which their earthy existence was derived from living shoots conserved in the ice of outer space…"
Szöllösi-Janze, 2001
6 Failure to appreciate this leads to confused questions such as whether discrimination against Jews should be considered racism. From a scientific perspective there are no races, so ipso facto the Jews are not a race. However, this is besides the point: if Jewish people are discriminated against, abused, attacked etc., either because of their religion, or because they are perceived as being members of an identifiable social ('ethnic') group, then this is clearly wrong and to be condemned, regardless of the label used.
If a legal system puts a particular weight on criminal offences that are motivated by racism (so, for example, punishments for those convicted have a premium), then what counts as a race for those purposes needs to be defined within that (social, i.e., legal) system, as natural science can have no role in determining social groupings that have no scientific basis.
7 This was lampooned in 'Star Trek: Enterprise', where Andorian Thy'lek Shran adopts the nickname 'pink skin' for Enterprise's Captain Archer.
From the Paramount Network Television series Star Trek: Enterprise
I often enjoy reading popular accounts of science topics, but sometimes one comes across statements that are vague or dubious or confusing – or simply wrong. Some of this reflects a basic challenge that authors of popular science share with science teachers and other science communicators: scientific ideas are often complex, subtle and abstract. Doing them justice requires detailed text and technical terminology. Understanding them often depends upon already having a good grasp of underpinning concepts. That is fine in a formal report for other scientists, but is not of any value to a non-specialist audience.
So, the author has to simplify, and perhaps round off some of the irregular detail; and to find ways to engage readers by using language and examples that will make sense to them. That is, finding ways to 'make the unfamiliar familiar'.
I am sure that often the passages in popular science books that I as a scientist1 get grumpy about are well motivated, and, whilst strictly inaccurate, reflect a compromise between getting the science perfect and making it accessible and engaging for the wider readership. Sometimes, however, one does get the impression that the author has not fully grasped the science they are writing about.
"Lucy Jane Santos is the Executive Secretary of the British Society for the History of Science…"
Public engagement with radium
I very much enjoyed reading a book, 'Half lives', by the historian of science Lucy Jane Santos, about how in the decades after its discovery by Pierre and Marie Curie, radium was the subject of wide public interest and engagement. One of the intriguing observations about this newly discovered element was that it appeared to glow in the dark. We now know that actually the glow comes from nitrogen in the air, as radium is radioactive and emissions by radium 'excite' (into a higher energy state) nitrogen molecules, which then emit visible light as they return ('relax') to their 'ground' state. This production of light without heating (a phenomenon generally called luminescence), when it is due to exposure to radioactivity, is known as radioluminescence.
Today, many people are very wary of radioactivity – with good reason of course – but Santos describes how at one time radium was used (or at least claimed as an ingredient) in all kinds of patent medicines and spa treatments and cosmetics (and even golf balls). This was a fascinating (and sometimes shocking) story.
What substance(s) can you find in quinine?
I did find a few things to quibble over – although across a whole book it was, only, a few. However, one statement that immediately stood out as dodgy science was the claim that quinine contained phospor:
"Quinine contains phosphor, a substance that luminesces when exposed to certain wavelengths of light…"
Santos, 2020
This may seem an unremarkable statement to a lay person, but to a scientist this is nonsensical. Quinine is a chemical compound (of carbon, hydrogen, nitrogen and oxygen), that is – a single substance. A single substance cannot contain another substance – any more than say, a single year can contain other years. An impure sample of a substance will contain other substances (it is in effect a mixture of substances), but quinine itself is, by definition, just quinine.
Molecular structure of the chemical compound quinine (C20H24N2O2) – a pure sample of quinine would contain only (a great many copies of) this molecule.
Note – no phosphorus, and no rare earth metal atoms.
The term 'phosphor' refers to a luminescent material – one that will glow after it has been exposed to radiation (often this will be ultraviolet) or otherwise excited. The term is usually applied to solid materials, such as those used to produce an image in television and monitor screens.
The term derives by reference to the element phosphorus which is a luminescent substance that was accordingly itself given a name meaning 'light-bearing'. The term phosphorescent was used to describe substances that continue to glow for a time after irradiation with electromagnet radiation ceases. But it is now known that phosphorus itself is not phosphorescent, but rather its glow is due to chemiluminescence – there is a chemical reaction between the element and oxygen in the air which leads to light being emitted.
The widely used term phosphor, then, reflects an outdated, historical, description of a property of phosphorus; and does not mean that phosphors contain, or are compounds of, phosphorus. There is clearly some scope for confusion of terms here. 2
term
meaning
luminescence
the emission of light by a cold object (in contrast to incandescence)
– chemiluminescence
a form of luminescence due to a chemical reaction
– – bioluminescence
a form of chemiluminescence that occurs in living organisms
– electroluminescence
a form of luminescence produced by passing electrical current through some materials
– photoluminescence
a form of luminescence due to irradiation by electromagnetic radiation, such as ultraviolet
– – fluorescence
a type of photoluminescence that only occurs whilst the object is being excited (e.g., by exposure to ultraviolet)
– – phosphorescence
a type of photoluminescence that continues for some time after the object has been being excited (e.g., by exposure to ultraviolet)
– radioluminescence
a form of luminescence due to a material being exposed to ionising radiation (e.g., 𝛂 radiation)
– sonoluminescence
a form of luminescence due to a material being exposed to sound
phosphor
a material that exhibits luminescence
phosphorus
a chemical element that exhibits chemiluminescence (when exposed to air)
There is a range of terms relating to luminescence. Here are some of those terms.
Some central ideas about luminescence (represented on a concept map)
A traditional medicine
Quinine, a substance extracted from the bark of several species of Cinchona, has long been used for medicinal purposes (e.g., by the Quechua people of the Americas 3), as it is a mild antipyretic and analgesic. It is an example of a class of compounds produced by plants known as an alkaloids. Plant alkaloids are bitter, and it is thought their presence deters animals from eating the plant. We might say that Quechua pain medication is a bitter pill to swallow.
Modern science has often adopted and developed technologies that had long been part of the 'traditional ecological knowledge' of indigenous groups – such as making extracts from Cinchona bark to use as medicines.
Sadly, the original discovers and owners of such technologies have not always been properly recognised when such technologies have been acquired, transferred elsewhere, and reported. 3
(Image by GOKALP ISCAN from Pixabay)
Quinine is an ingredient of tonic water (and bitter lemon drink) added because of its bitter taste.
(Why deliberately make a drink bitter? Quinine has anti-malarial properties which made it a useful substance to add to drinks in parts of the world where malaria is endemic. People liked the effect!)
Quinine glows when exposed to ultraviolet light. It is luminescent. To be more specific, quinine is photoluminescent. (This is responsible for the notion that someone offered a gin and tonic at a disco should test it under the 'blacklights' to make sure they have not been given pure gin to drink. Although, I am slightly sceptical about whether the kind of people that drink 'G&T's go to the kind of dances that have ultraviolet lighting.)
"I do apologise, I think I might have just splashed a tiny droplet of my tonic water on you"
(Image by Victoria_Watercolor from Pixabay)
It is reasonable to describe quinine as a phosphor in the wider sense of the term – but it does not contain another phosphor substance, any more than, say, iron contains a metallic substance or sulphur contains a yellow substance or sucrose contains a sweet substance or copper a conducting substance. So, a more accurate formulation would have been
"Quinine [is a] phosphor, a substance that luminesces when exposed to certain wavelengths of light…"
or, perhaps better still, simply
"Quinine [is] a substance that luminesces when exposed to certain wavelengths of light…"
Ask the oracle
I was intrigued at why Lucy Jane Santos might have been confused about this, until I did a quick internet search. Then I found a range of sites that claimed that quinine contains phosphors – indeed, often, rare earths are specified.
The rare earths (another unfortunate historic choice of name, as it transpired that they are neither especially rare nor 'earths', i.e., oxides) are a group of metallic elements. They are not as well known as, say, iron, copper, zinc, aluminium or gold, but they have with a wide range of useful applications.
Scandium, the first of the 'rare earth' metals. Probably not what you want in your tonic water.
If something is repeated enough, does it become true?
Clearly there are not rare earths in quinine. So, the following quotes (from sites accessed on 7th March 2023) proffer misinformation.
"If you want to get a bit more scientific about it…. quinine contains rare earth compounds called phosphors. These are the substances which glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own colour, in this case glowing blue light."
This claim is odd, as the previous paragraph explained more canonically: "why does quinine absorb UV light (the invisible component of sunlight that produces sun tans and sunburns!)? It is due to the structure of the quinine molecule, which enables it to take in energy in the form of invisible UV light and immediately radiate some of that same energy in the form of visible blue light." Other compounds cannot be inside a molecule – so this more canonical explanation is not consistent with quinine containing other "substances" which were "rare earth compounds."
"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light."
The following extract appeared under the subheading "Why is quinine fluorescence?" That reflects a category error as quinine is a substance and fluorescence is a process (and fluorescent the property) – so, presumably this should have read why is quinine fluorescent?
Why Quinine Glows
Quinine contains rare earth compounds called phosphors. … Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light.
Tonic water glows and [sic] will fluoresce under UV rays because of quinine in it. Quinine is one of the most important alkaloids found in the cinchona bark, among many others. It has some rare earth compounds known as phosphors that glow when they hit certain wavelengths of the UV light. Phosphors in the quinine absorb the UV light and then reflect it or emit it again in the form of glowing blue light.
Perhaps the most bizarre example was a site, 'emaze' which offered to show me "How to create magic mud…in 17 easy steps"
Step 1 was
"wash your potatoes!!!!"
However, perhaps due to exclamation fatigue(!), this went in a different, if now familiar, direction with step 2:
"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light"
https://app.emaze.com/@AORQCIII#/16
This text was then repeated as each of steps 3-14. (Sadly steps 15-17 seemed to have been missed or lost. Or, perhaps not so sadly if they were just further repeats.) The first screen suggests this presentation was "done by Dr. Meena & Maha" but if Dr. Meena & Maha really exist (if you do, I am sorry, the internet makes me very sceptical) and 'done this', it is not clear if they got bored with their task very quickly, or whether the server managed to corrupt a much more coherent presentation when it was uploaded to the site.
This 'emaze' presentation seems to want to emphasise how quinine contains rare earth compounds…
According to Google, the site 'Course Hero' suggested
"Phosphors, which are found in quinine, are rare earth compounds. These chemicals glow when they are struck with particular wavelengths of the EM spectrum, …"
but unfortunately (or perhaps fortunately given that snippet), the rest of the text seemed to be behind a pay-wall. This did not offer a strong incitement to pay for material on the site.
Toys coated with phosphorus?
Another website I came across was for a shop which claimed to be selling glow-in-the-dark objects that were made with phosoporus that needed to be illuminated to initiate a glow: a claim which seems not only scientifically incorrect (as mentioned above, phosphorus is not photoluminescent – it glows when in contact with air as it oxidises), and so unlikely; but, otherwise, dangerous and, surely, illegal.
During my search, I came across a website (grammarist.com) offering to explain the difference between the words phosphorous and phosphorus. It did not discuss rare earths, but informed readers that
"Phosphate: Noun that means an electrically charged particle. Phosphorus: Also a noun that means a mineral found in phosphate." …We've already established that phosphorus is the simple mineral found in the particle phosphate, but phosphor is something else altogether."
So, that's 'no', 'no', 'no', and…I think at least one more 'no'.
Phosphorus is a reactive element, and is not found in nature as a mineral. To a scientist, a mineral is a material found in nature – as a component of rocks. Unfortunately, in discussing diet, the term minerals is often associated with elements, such as, for example, phosphorus, iodine, potassium and iron that are necessary for good health. However, one would not eat the element iron, but rather some compound of it. (Foods naturally contain iron compounds). And trying to eat phosphorus, iodine or potassium (rather than compounds of them) would be very hazardous.
So, whilst a nutritional supplement might well contain some minerals in the composition, strictly they are there as compounds that will provide a source of biologically important elements, and they will be metabolised into other compounds of those elements. (Iron from iron compounds will, for example, be used in synthesising the haem incorporated into red blood cells.) Unfortunately, learners commonly have alternative conceptions ('misconceptions') about the difference between mixtures and compounds and assume a compound maintains the properties of its 'constituent' elements (Taber, 1996).
The grammarist.com entry helpfully warned us that phosphate was "not to be confused with phosphoric acid, a chemical compound found in detergents and fertilizers". I suspect it is only found in detergents and fertilisers when something has gone wrong with the production process (notwithstanding diluted phosphoric acid has been used directly as a fertiliser) 4. It is a corrosive and irritant substance that can cause bronchitis – although tiny amounts are added to some colas. [n.b., cocaine also once featured in some cola, but that is no longer allowed.]
An ion is an electrically charged particle
The phosphate ion is one example of a type of ion.
Phosphates (such as calcium phosphate) are substances that contain phosphate ions.
So, phosphates contain electrically charged particles (phosphate ions), but that does not make phosphate an electrically charged particle, just as
blue does not mean a large marine mammal
bank does not mean a day of celebration where people do not need to go to work
vice does not mean a senior executive officer
motor does not mean a two wheeled vehicle
compact does not mean a flat circular object
final does not mean a simple musical instrument played with the breath
free does not mean a meal taken around noon or soon after, and
meal does not mean a token that provides entry or service
Grammarist invited feedback: I sent it some, so hopefully by the time you read this, the entry will have been changed.
It was on the internet: it must be true
The internet is an immense and powerful tool giving access to the vast resources of the World Wide Web. Unfortunately, the downside of a shared, democratic, free to access, reservoir of human knowledge is that there is no quality control. There is a lot of really good material on the web: but there is also a lot of nonsense on the web.
One example I have referred to before is the statement:
"energy is conserved in chemical reactions so can therefore be neither created nor destroyed"
This has the form of a logical structure
X so therefore Y
which is equivalent to
Y because X:
"energy can be neither created nor destroyed because it is conserved in chemical reactions"
This is just nonsense. There is no logical reason why the conservation of energy in chemical reactions implies a general principle of energy conservation.
We can deduce the specific from the general (days have 24 hours, so Sunday has 24 hours) but not the general from the specific (January has 31 days, so months have 31 days).
Perhaps this is easily missed by people who already know that energy is always conserved.
A parallel structure might be:
"association football teams always consist of eleven players so therefore sports teams always consist of eleven players"
"sports teams always consist of eleven players because association football teams always consist of eleven players"
This is 'obviously' wrong because we know that rugby teams and netball teams and volleyball teams and water polo teams (for example) do not consist of eleven players.
But what about quinine containing rare earth compounds? A notion that is structurally similar to claiming that
France contains South American countries, or
'Great Expectations' contains Jane Austin novels, or
February contains Autumn months, or
Cauliflower contains citrus fruits, or
Beethoven's 5th Symphony contains Haydn concerti
(in other words, something obviously silly to someone who has a basic understanding of the domain – chemistry or geography or literature or the calender or botany/horticulture or music – because it suggest one basic unit contains other units of similar status).
How does this error appear so often? Quite likely, a lot of website now are populated with material collected and collated by machines from other websites. If so, it only takes one human being (or government department) to publish something incorrect, and in time it is likely to start appearing in various places on the web.
There is currently a lot of talk of how artificial intelligence (AI) is getting better at writing essays, and answering questions, and even drafting lectures for busy academics. AI seemingly has great potential where it is provided with high quality feedback. Perhaps, but where the AI is based on finding patterns in publicly available texts, and has no real ability to check sense, then I wonder if the www is only going to become more and more polluted with misinformation and nonsense.
I do not know where Lucy Jane Santos got the idea that there are other substances in the single substance quinine (akin to having other countries in France), but if she did a web-search and relied on what she read, then I am in no position to be critical. I use the web to find things out and check things all the time. I am likely to spot gross errors in fields where I already have a strong background…but outside of that? I do seek to evaluate the likely authority of sources – but that does not mean I could not be taken in by a site which looked professional and authoritative.
The web started with imperfect people (because we all are) posting all kinds of material – with all kinds of motivations. I expect most of it was well-meaning, and usually represented something the poster actually believed; and indeed much of it was valid. However, a 'bot' can search, copy, and paste far quicker than a person, and if the internet is increasingly authored by programs that are indiscriminately copying bits and pieces from elsewhere to collage new copy to attract readers to advertising, then one cannot help wonder if the proportion of web-pages that cannot be trusted will be incrementally coming to dominate the whole network.
I (a fallible, but natural intelligence) hope not, but I am not very optimistic.
Work cited:
Santos, Lucy Jane (2020) Half lives. The unlikely story of radium. Icon.
1 Although my own research has been in science education and not one of the natural sciences, I am pleased that the learned societies (e.g. the Institute of Physics, the Royal Society of Chemistry, etc.) and the UK's Science Council, recognise the work of science educators as professional contributions to science.
2 One internet site suggests:
Luminescence is caused by various things like electric current, chemical reactions, nuclear radiation, electromagnetic radiation, etc. But phosphorescence takes place after a sample is irradiated with light.
• Phosphorescence remains for sometime even after the lighting source is removed. But luminescence is not so.
The second paragraph is nonsensical since phosphorescence is a type of luminescence. (It should be, "…fluorescence" that does not.) The first paragraph seems reasonable except that the 'but' seems misplaced. However 'in the light of' the second sentence (which sees phosphorescence and luminescence as contrary) it seems that the (contrasting) 'but' was intended, and whoever wrote this did not realise that light is a form of electromagnetic radiation.
Another, more technical, site suggests,
Luminescence is the emission of light by a substance as a result of a chemical reaction (chemiluminescence) or an enzymatic reaction (bioluminescence).
chemiluminescence (due to a chemical reaction) versus
bioluminescence (due to an enzymatic reaction).
However, the keen-eyed will have spotted that "an enzymatic reaction" is simply a chemical reaction catalysed by an enzyme. So, bioluminescence is a subtype of chemiluminescence, not something distinct.
3 Some sources claim that the medicinal properties of cinchona bark were discovered by Jesuit missionaries that travelled to South America as part of European imperial expansion there.
Nataly Allasi Canales of the Natural History Museum of Denmark, University of Copenhagen is reported as explaining that actually,
"Quinine was already known to the Quechua, the Cañari and the Chimú indigenous peoples that inhabited modern-day Peru, Bolivia and Ecuador before the arrival of the Spanish…They were the ones that introduced the bark to Spanish Jesuits."
Learning about the history of indigenous technologies can be complicated because:
often they are transmitted by an oral and practice culture (rather than written accounts);
traditional practices may be disrupted (or even suppressed) by colonisation by external invaders; and
European colonisers, naturalists and other travellers, often did not think their indigenous informants 'counted', and rather considered (or at least treated) what they were shown as their own discoveries.
4 This again seems to reflect the common alternative conception that confuses mixtures and compounds (Taber, 1996): phosphoric acid is used in reactions to produce fertilizers and detergents, but having reacted is no longer present. It is a starting material, but not an ingredient of the final product.
Just as we do not eat iron and phosphorus, we do not use washing powders that contain phosphoric acid, even if they have been prepared with it. (Increasingly, phosphates are being replaced in detergents because of their polluting effects on surface water such as rivers and lakes.)
5 This gives the impression to me that the Department of Education sees schooling as little more than a game where students perform and are tested on learning whatever is presented to them, rather than being about learning what is worth knowing. There is surely no value in learning a logically flawed claim. Any student who understands the ideas will appreciate this statement is incorrect, but perhaps the English Government prefers testing for recall of rote learning rather than looking for critical engagement?
This page contains a number of scientifically incorrect statements, but I am most concerned about your misleading characterisation of phosphorus as a 'safe' material.
Scientific errors
Your site claims that
"phosphorus…has the ability to absorb and store surrounding light"
"the ability to absorb and store surrounding light…works similar to the natural process of photosynthesis"
"Phosphorus glow absorbs and stores surrounding light. When it is dark, the stored light is slowly released in the form of a glow"
"Glow in the Dark products contain phosphorus…it needs to be exposed to light before it can work"
"Radium glow produces light on its own through a chemical process."
All of these claims are mistaken.
1. Luminescent materials do not store light. Light cannot be stored, it is a form of electromagnetic radiation. (In LASERS light is contained within a cavity by reflecting it back and forth by mirrors, but phosphorus is not able to do anything like this.) When the radiation is absorbed by a photoluminescent material the radiation ceases to exist. Because the molecules of the absorbing material are excited into a higher energy state, new electromagnetic radiation (light) may later be emitted – but it is not light that has been stored. (The energy transferred to the luminescent material by the radiation may be considered as stored: but not the light).
2. The process of photosynthesis does not involve "the ability to absorb and store surrounding light" – absorb, yes, but the light is not stored – it ceases to exist once absorbed.
3. Materials which absorb energy from radiation, and then release it slowly ('glow') are called phosphorescent. This does not (only) occur 'when it is dark', but from immediately after irradiation. (The process occurs regardless of whether it is dark enough to observe.)
4. Phosphorus is not itself a phosphorescent material. The glow seen around white phosphorus is due to a chemical reaction with oxygen in the air. Not only does this not store any light, but, also, it does not need light to initiate.
5. Radium does NOT produce light through a chemical process. Radium is radioactive. It undergoes radioactive decay (due to a change in the atomic nucleus). This is NOT considered a chemical process.
Now I turn to what I consider a more serous problem with your site.
Potentially dangerous misinformation
The more serious matter concerns your claim that to be selling products containing 'non toxic' phosphorus:
"Glow in the Dark products contain phosphorus (a non toxic substance) which has the ability to absorb and store surrounding light…"
"Phosphorus is non toxic and safe for general use."
"Phosphorus is a natural mineral found in the human body. Phosphorus Glow in the dark products is perfectly safe for everyday use"
"Many get confused and associate all green glow products to be radioactive. This is not true. Phosphorus glow is non toxic and non radioactive."
You may wonder why I think this matters enough to contact you.
It is very misleading to suggest to people reading the site (which could include children who might well be interested in glow-in-the-dark toys) that phosphorus is harmless, and this is completely wrong.
Phosphorus is not found as a natural mineral, as it is much too reactive to be found native (that is, as phosphorus) on earth – although many minerals are compounds of phosphorus (and thus do NOT share its chemical properties), and so sources of the element for use in agriculture etc. The human body does contain compounds of phosphorus, notably in the bones, but again there is no phosphorus (the substance phosphorus) in the human body – if you introduced some it would very quickly react. Sources of phosphorus are important in the diet, but it would be very unwise to try to eat phosphorus itself.
Phosphorus can be obtained in different forms (this is called allotropy where the same element can have different molecular structures – like graphite and diamond both being pure forms – allotropes -of carbon). Some allotropes of phosphorus are not especially dangerous. However, the form which glows is white (or yellow) phosphorus, and this is a very hazardous material.
So, handling phosphorus is dangerous and needs special precautions. (If you really did use phosphorus in your products, I imagine you would know that?) Here is some information from authoritative websites
"Ingestion of elemental white or yellow phosphorus typically causes severe vomiting and diarrhea [diarrhoea], which are both described as "smoking," "luminescent," and having a garlic-like odor. Other signs and symptoms of severe poisoning might include dysrhythmias, coma, hypotension, and death. Contact with skin might cause severe burns within minutes to hours…"
"White phosphorus is extremely toxic to humans, while other forms of phosphorus are much less toxic. Acute (short-term) oral exposure to high levels of white phosphorus in humans is characterised by three stages: the first stage consists of gastrointestinal effects; the second stage is symptom-free and lasts about two days; the third stage consists of a rapid decline in condition with gastrointestinal effects, plus severe effects on the kidneys, liver, cardiovascular system, and central nervous system (CNS). Inhalation exposure has resulted in respiratory tract irritation and coughing in humans. Chronic (long-term) exposure to white phosphorus in humans results in necrosis of the jaw, termed "phossy jaw."
Please feel free to check on this information for yourself.
However, I recommend you change the information on your website. In particular, please stop suggesting that phosphorus is a safe, non-toxic material, when the form of phosphorus which glows is highly toxic. I trust that now this has been brought to your attention, you will appreciate that it would be highly irresponsible for you to continue to advertise your products using misleading information about a hazardous substance.
