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
What is it like to be a mosquito? At the risk of an early spoiler, I admit I do not know. But I know of a couple of professors who might think they do. I have learned from Prof. Leslie Vosshall (Chief Scientific Officer of the Howard Hughes Medical Institute at Rockefeller University) that mosquitoes actually enjoy the experience of piercing human skin to feed on blood, but according to Prof. Sarah Reece (Professor of Evolutionary Parasitology at the University of Edinburgh) they feel rubbish if they gorge on blood too soon after waking up or just before going to sleep.
Female mosquitoes of some species feed on human blood (picture by FotoshopTofs sourced from Pixabay)
How can we know what it is like to experience the world as another?
I cannot deny these claims, but I am sceptical we can justifiably make them.
The philosopher Thomas Nagel famously posed the question of what it is like to be a bat. He could have substituted a cat or a dolphin or a pigeon. Bats are mammals, like us. But they are quite different from humans in many respects. They are nocturnal, unlike most of us; and they eat more insects than most of us. They tend to sleep hanging upside down, which we generally do not. Perhaps more significantly, they fly in a way humans unaided do not, and in flying around in the dark navigate by echolocation – which again is quite unlike us.
The point is that the bat's sensory apparatus is so different from ours that we have no experience of what it might be like to be a bat. But this is jut one example. Almost a century ago the biologist Jakob von Uexküll proposed the term 'umwelt' to describe the environment as perceived by an organism, and attempted to imagine how the organism's scale and habitat and sensory and cognitive apparatus would influence its perception of the world. Being a spider 'tuned in' the vibrations of a the threads of a web is quite different to being a bat, but also quite different from being the fly using its compound eye to avoid the spider's web.
The issue is not just the array of sensory organs, but the cognitive system that has evolved to function with it. How can we appreciate what it is like to be a dolphin which sleeps half a brain at a time? How can we understand what it might be like to be an octopus which has a central brain that delegates to subsidiary organs in each tentacle, so they work as somewhat autonomous units. Imagine only finding out you are going for a walk 'second hand' – the octopus head must be a bit like a traveller on a train who notices when pulling out of a station but has no direct input into the action. 'A bit like', but we can never really know what it is actually like to be an octopus.
Qualia-tative experience
Some birds and insects have differently tuned colour receptors in their eyes, so for example some can see into what we call ultraviolet. So some insects see lines on petals that lead to the nectar – lines that we just do not see. Their visual world is simply different to ours.
But why stop there? My father was colour blind. He saw the same objective world as me, but could not make the same red-green distinctions that I can. This never bothered him – he had no idea what he was missing (and, critically, it did not seem to affect his golf). We might say his umwelt was different to mine because of these differences in our sensory apparatus.
Yet this touches upon the notion of qualia, the word used to describe our direct sense experiences. I have an experience of red – something I experience when I look at a red object. I have a different qualia if I see something green. That is, I have a subjective experience when I perceive a particular colour.
Physics tells us that colours are not objective properties of objects, rather our visual system processes the reflected spectrum from an object, and somehow does a comparison with the rest of the visual field to 'allow' for overall viewing conditions (so the light at midday compared with the light when the sun is setting makes a great difference to the spectrum of light being reflected from an object for example) and usually maintains a reasonable continuity in the qualia – the colour as perceived in a person's consciousness. (Questions of the processing in terms of chemistry and physics and cell biology are clearly scientific questions – but it is less clear if natural science can ever fully explain the subjective experiences.)
Presumably, my father did not experience red and green as I do – perhaps he experienced what I see as green when looking at red as well as when he looked at something green – or perhaps he saw my yellow in both cases, or perhaps he had completely different colour qualia that I have never experienced. And, this might be true of people with 'normal' colour vision. What I experience as red is not (as far as we know) inherently directly linked to anything physical about red objects but perhaps is something that emerged from my developing sensory-cognitive system as it interpreted perceptual data when I was very young. Maybe another person, with a different unique selection of genes, and with a different developing brain, and somewhat different early visual experiences, will experience my red when they see something that is blue? Or again, perhaps what they experience is something different to any of my colour qualia?
After all, if we agree on what is red and what is blue and what is green (and let's face it, we do not always even agree on that) this would be just as true if we are experiencing different subjective colours, as long as the qualia are consistent within each person. How could we ever know? Perhaps those people mocked for having poor taste in colour combinations (mea culpa) are seeing wonderful juxtapositions when their mockers see clashes? Again: how could we ever know?
Our brains do not arrive fully formed, but develop in response to our experiences. So, how we hear sound develops in relation to the early sound environment – certainly in relation to speech. We often find it difficult to discriminate the sounds of a very unfamiliar language as repeated early exposure to our specific native language has led to modifications in the way we process sounds.1 It is like the brain grows its own filters and interpretation algorithms to make best sense of what is experienced in early life.
And the somewhat mysterious sense of smell is likely much more individual than sight or sound, such that it varies much more according to one's personal genetic profile, much like our immune systems.
So perhaps we can never really know how another person experiences the world, let alone how a bat, a dolphin or an octopus experiences their lives. Or, surely, a mosquito.
Now to be totally clear, I am not suggesting that because other organisms may not experience the world as we do, we can treat them as though they do not have experiences. The Cartesian distinction between humans as having minds and everything else being mere machinery is not convincing when we consider the common evolutionary basis of life on earth.
I imagine that bats and dolphins and octopuses have rich lived experiences, just that these are incommensurable with our human experiences. I am not convinced that there is anything it is like to be a bacterium or a protozoan (they have senses, but surely not consciousness), but I would not rule out spiders, flies and mosquitoes having some kind of conscious experience – even if, surely, with their tiny brains, this would be much less rich than ours. And that is what leads me to be sceptical of some of what I heard from Profs Vosshall and Reece.
The curious case of the reflective mosquito
What sparked these thoughts was listening to an episode of the BBC Radio 4 programme/podcast 'Curious Cases', a popular science programme aimed at a general audience. The episode was about mosquitoes that bite people, and why they seem to prey on some people more often than others.
In discussing those species of mosquitoes that bite humans, the guest scientists made a number of claims that I considered it would be difficult to justify.
Prof. Sarah Reece told listeners that,
"We feel rubbish if we eat a massive meal just before we go to bed or immediately if we wake up. The same is going to be true for mosquitoes as well."
Perhaps she is right – but does that seem likely?
Reece compared the mosquito feeding (we might say gorging) on blood to be like a human drinking a bath of soup. Excessive eating before bedtime is unwise for humans. But then we are not mosquitoes. Modern humans in many contexts are able to engage in eating behaviours that are not healthy, but which would have matched a sensible strategy (i.e., eat whenever food is available) during most of human evolution when food was not as abundant. The modern standards of living allowing over-consumption experienced by many people today have not existed long enough for natural selection to have changed our eating behaviours. Perhaps mosquitoes have evolved to feed in the way they do because they, as mosquitoes, have different life-cycles, and experience different environmental affordances and constraints, to us.
We may feel 'rubbish' if we have a large meal too close to bedtime – but can we assume this transfers to an insect? (Image by OpenClipart-Vectors from Pixabay)
Perhaps they do feel something after talking a blood meal, and perhaps it feels different according to the time of day – but who knows? I do not, and I am not convinced by the justification that what is true for a human must be the case for an insect. (Humans may feel guilt or regret or shame afer eating an immoderate meal – so do mosquitoes? Humans often belch after excessive eating: so does this mean mosquitoes will burp after engorging themselves on human blood?)
Prof. Leslie Vosshall made a number of claims I found questionable:
"They love everything about humans…they like the feeling of piercing skin"
"The blood-feeding mosquitoes have figured out how to get a giant protein-rich meal mostly from humans and they need that to make eggs….They're being good mums, they want to provision their offspring with the biggest meal possible
"The mosquitoes say like 'haha, you are all like sleeping under these nets where we can't get at you' and so slowly the population moves to day biting…because they realise that we are not going to walk around wearing bed nets, as we go about our day."
Mosquitoes enjoy piercing skin
So, according to Prof. Leslie Vosshall mosquitoes enjoy the experience of piercing the skin of people they feed off. Now on the face of it I do not think this is unreasonable. Humans enjoy eating, as well as other activities that support species survival – sexual activity, a good sleep, being with a pair-bonded partner, keeping young children close at hand and petting them…. I expect chimpanzees enjoy grooming each other as they remove parasites. It makes sense that evolution would lead to people and other complex organisms enjoying essential activities. Natural selection for finding eating unpleasant or for being indifferent to human offspring would not work out so well.
But does a mosquito have a sufficiently complex neural system for this kind of experience to evolve, or is biting people no more than an instinctive behaviour? Do mosquitoes have a subjective experience we can reasonably describe as liking the feeling of piercing skin? I cannot be certain that they do not, but I am doubtful; and I wonder how Prof. Leslie Vosshall thinks she knows they do.
Mosquitoes want to be good mums
I can understand how a good blood meal may allow a female mosquito to provide the nutrients needed for healthy eggs. But then as an adult human being I have the ability to engage in abstract thought – what is known as 'formal operations'. I have abstractconcepts relating to nutrition, and reproduction, and I am able to link these concepts in patterns to see how sucking blood relates to a healthy brood (such as understanding how proteins from the blood can be broken down into the amino acids used to build up new proteins in the egg).
But does a mosquito really know it is to be a mum, and does it have any idea at all that its feeding activity is related to its reproductive activity? I really would take some persuading (by argument that is based on evidence, as is the way in science) that mosquitoes want to provision their offspring with the biggest meal possible.
I doubt this is literally true. Does a female fish have any concept of males, and does she actually know that she will spawn eggs that develop into 'baby' fish that (if not predated first, as most are) will grow into adults like herself? I am pretty sure the fish has no understanding of any of this, and simply follows instincts that have evolved, rather than having a preference based on a deliberate mothering strategy.
Could I be wrong about the fish?
Could I really be wrong about the mosquitoes?
Mosquitoes work things out for themselves
Two other claims here seem even more extreme. If I take Prof. Vosshall's comments literally then she thinks that mosquitoes worked out that (a) feeding off humans rather than plants was a good way to access dietary protein; and also that (b) humans sleep under mosquito nets which make them inaccessible, but that the humans will leave the nets behind when they go about daily activities, and so will then be more susceptible to 'bites'.
No, I am sorry – but I do not think that mosquitoes have any kinds of mental experiences that we would reasonably describe in these terms. We are reflective beings, that analyse situations in abstract terms; imagine possible futures; make plans, and (sometimes at least) act deliberately in accord with our reasoning. Our large, highly evolved, brains and the cultural representational tools – language and other symbol systems, that we, in effect, 'load up' as 'apps' during our extended development and enculturation – allow us to do this.
By contrast, an adult mosquito has a tiny brain, is not social, and lives to feed and breed for about a month if it is lucky. I do not think any mosquito has ever figured out anything about its nutritional requirements or the behavioural patterns of other species. I am happy to accept a mosquito has some kind of subjective experience, but not that it has abstract thought or reasoning. It reacts to behavoural stimuli, and perhaps engages in some level of learning – but it does not reflect on experience and reason things out.
It is just anthropomorphism
Do Profs Vosshall and Reece really think that a mosquito can have this level of awareness of its physiology and environment, and this reasoning power? Perhaps they do – they surely know a great deal more about mosquitoes than I do. But I suspect not. I suspect they are speaking figuratively – either deliberately or inadvertently.
'Curious Cases' is aimed at a general audience, not science specialists. It is possible that Profs Vosshall and Reece are deliberately seeking to use language that will engage and be accessible to the target audience. Alternatively, perhaps these scholars are so used to using this kind of language that they have fallen into habits of speech (and thought?) which were originally meant as a kind of shorthand, and so it does not occur to them that their audience may not share that assumption.
Is this a problem?
Anthropomorphism is one way of engaging young people with science – after all, all teachers seek to make the unfamiliar familiar by relating it to what learners find familiar. What we all find most familiar is being human – human experience. We experience the world as a human um965674welt, and we understand through human-developed concepts. We can help learners relate to other species by presenting them as if human-like beings in different bodies.
The problem is that these types of accounts are pseudo-explanations. They appear to explain natural phenomena, but they surely cannot be true. Yet we know learners often adopt these anthropomorphic accounts as if they are formal scientific explanations (so, a chemical reaction occurs because the atoms want to get full electron shells). Anthropomorphism may help introduce unfamiliar ideas about other species, but it can also act as an impediment to appreciating how these beings are different to us (Taber & Watts, 1996).
If we think that mosquitoes started feeding on humans because they appreciated the protein content of human blood, or that some species of moth decided after due consideration that eating clothes was the means to a better life, then we have an explanation for that phenomenon – but surely not a valid one.
So, I do not claim to know what it is like to be a mosquito, but I am pretty sure it is not quite like being a human. I would suggest that one human's experience is an imperfect guide to how other humans experience the world, and an even more imperfect guide to what it is like to be a chimp; let alone a bat, a dolphin, or an octopus. Certainly, I suspect human experience is a very limited and potentially misleading guide to what it is like to be a mosquito.
Because I have thought about these issues a lot over the years, I was primed to be immediately sceptical of the claims made by Profs Vosshall and Reece. But presumably most of the audience are not professional scientists. I just wonder how many of the listeners accepted these claims at face value, and thought they were learning robust scientific notions?
Note:
1 Learning a language is like mapping out an archipelago
A visual analogy for how we parse sounds to recognise expected phonemes. From 'Student Thinking and Learning in Science'
"A new born child certainly does not have to learn to make sense of sensory experiences entirely from scratch. The neural connections that develop to allow the processing of visual information, for example, develop in highly complicated ways apparently largely as a result of the unfolding of genetic instructions. We are hard-wired to be able to readily spot edges and movement in the visual field. However, it also seems that our brains are set up to recognise common patterns in sensory information, and to then in effect 'hard wire' themselves to subsequently expect and notice those patterns….
An example of this effect occurs in learning a language. The human vocal apparatus can produce a wide range of sounds, and only a selection of these are used in any particular language. One of the reasons learning a foreign language is sometimes so difficult is because of the need to hear and produce sounds quite unlike those familiar from ones native language. So the sounds used in a particular language are a bit like an archipelago of islands rising above the sea, if the sea is considered to represent the range of sounds that could be used in spoken languages. Different languages offer different patterns of islands.
Now when children are born they do not know in advance which language they will hear and learn – they have no map of the sea to show them where the local islands are. That would not matter if people were precise in speech production and all members of the same language community clearly produced precisely the same sounds. In practice people have different voices and sometimes only approximate the 'right' sounds when they speak. In effect, some of the sounds produced by people are not on the islands at all, but are like swimmers or even boats that are some distance from shore. Incredibly, as the young child hears its local language it comes to recognise similarities in the sounds used, and their brain in effect produces a map of where the islands are – the locations of sounds most commonly used as clumps on the map of the 'sound sea'. Once the map is developed the brain no longer treats each sound heard as being like a map grid reference, but assigns it to the relevant island. Those sounds which occur off-shore (so to speak) are also assigned to the closest island and considered to be located there.
This process means that the person's perception of vocal sounds changes so that they in effect only hear the sounds expected in their language community, even when speech production is not perfect. To shift metaphors, the effect is like having an automatic spell-checker on your email in-box. People might send you mis-spelt messages, and occasionally you may be sent email written in a different language to your own, but (due to the spell-checker) when you open your emails you always find everything is perfectly spelt. Of course, a spell-checker only makes best guesses, so sometimes sentences do not make sense when the wrong spelling is selected automatically, or a word not in the spell-checker's dictionary is replaced, or entire swathes of another language are rendered into a nonsense string of local words.
This effect has been demonstrated using sound synthesisers that can produce fine variations in sound. These can be set up to produce a whole sequence of sounds that gradually shift between two sounds that are used in local spoken language – say a 'p' sound and a 'b' sound. The synthesizer starts with a canonical 'p', say and then shifts slowly to a canonical 'b' in a similar way to software which morphs between different images. However what is perceived is not a gradual morphing. Although an oscilloscope display will show a gradual change in the waveform being produced, the person will hear a string that sounds like p-p-p-p-p-p-p-p-p-p-p-p-b-b-b-b-b-b-b-b-b-b-b-b-b-b. The person's brain first recognises the sounds as being closest to the 'p' island, until a point when it 'decides' they are closer to the 'b' island. Of course this 'decision' is made completely pre-consciously – the person is conscious of repeats of one letter which suddenly shifts to being a different letter (even though there is actually no sudden shift in the sounds, but just a very gradual variation across a spectrum between the two endpoints). We are all familiar with the person with the speech defect or the person with a strong accent who is difficult to understand, but generally our brains present to us speech as if people are producing the same canonical sounds, filtering out much of the variation due to age, gender, and so on. [The figure above] offers a visual analogy of this phenomenon:"
Taber (2014)
Work cited:
Nagel, Thomas (1974). "What Is It Like to Be a Bat?". The Philosophical Review. 83 (4): 435-450. doi:10.2307/2183914
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.
Of undead trees, silent genes and chaperone proteins
Keith S. Taber
These zombie metaphors become (like a neutron star) 'undead' as they pass from the expert's text to the novice's mind. They are phantom metaphors in the sense that they will manifest as 'living' metaphors to the uninitiated even though the expert user knows they have been put to death.
…the novice or non-specialist has no way of knowing what is the refined meaning and what is just semantic residue.
I have become a little obsessed with the figurative language used to explain science. Science often involves quite abstract ideas, which – by definition, being abstract – do not directly relate to familiar concrete objects and experiences. Learning theory suggests that to make good sense of new information, we need to relate it existing mental resources (existing knowledge and understanding; familiar experiences or images, and so forth).
This implies a paradox (indeed this is related to a traditional puzzle known as 'the learning paradox'):
we can only make sense of things we can relate to in terms of past experience
the science curriculum sets out a large number of abstract ideas that do not directly relate to the everyday experience of most people
We are all familiar with green plants, and may know from practical experience that they need light and moisture, but that direct everyday, phenomenal, experience is some way from the abstractconcept of photosynthesis. This point could be repeated regarding any number of other ideas met in science courses: magnetic hysteresis, p-orbitals, electron spin, genomes, metabolism, uniform electrical fields, electronegativity…
Now, perhaps any science teachers or scientists who read that passage may feel I am exaggerating – they can no doubt readily bring to mind images representing hysteresis and fields and genomes, and equations for photosynthesis with chemical formulae, and the values electron spin can take (±1/2, obviously). These things will be familiar and can be readily represented in 'working memory' (where we undertake deliberate thinking), so to be applied or mentipulated in various ways. But that is a result of the familiarity of expertise built up over a good deal of time. Sure, I can bring to mind a representation of a double bond or a methane molecule or the earth's magnetic field as easily as I can bring to mind an image of a table or a bus or a blackbird. This is useful for a science educator, but is also a potential barrier to putting oneself in the place of a novice learner.
A key is that "the science curriculum sets out a large number of abstract ideas that do not directly relate to the everyday experience of most people". And teachers, and other science communicators (such as journalists and science writers) can address this in two ways.
The best response, when possible, is to provide experiences (through demonstrations and practical activities) that motivate the concepts to be learnt. By motivate, I mean that this experience provides a recognised need for the explanations (as well as associated technical terminology) to make sense of the experiences. Practical work in science classes can be used in various ways, and rather than teach students about some theory, and then demonstrate it, it may be possible to offer experiences which raise questions and wonderment that will give the explanations 'epistemic relevance' (Taber, 2015). The learner will not just be learning about concept X because it is in a syllabus, but because they want to know why Y happened. Now that may seem idealistic – but most children start curious (perhaps before the routine nature of formal education somewhat dulls this) and it is something to aim for.
But of course some things are too slow, too fast, too big, or too small (or too dangerous or too expensive) to bring into the classroom. One cannot* teach the big bang by giving learners a direct experience which will lead to them asking questions that can be satisfactory answered by introducing the canonical scientific account. (* Perhaps I am wrong – if so, I would like to see ther lesson plan.)
Tools for making the unfamiliar familiar
So, the other approach to 'making the unfamiliar familiar' needs to be indirect, perhaps with videos and simulations and models which represent the inaccessible experiences – supported by (and where those tools are not available, through) a narrative where the teacher talks new entities into existence in a learner's 'mind (Lemke, 1990).
Important tools here are analogies where the learner is told that the unknown 'X' is in some ways a bit like the very familiar 'A'. There are a great many examples of analogies used in explaining science. Here are just a few:
Now analogies (like models more generally) are never perfect. X is like A in some ways, but in other ways X is not at all like A. (Otherwise, an X would be an A, and so no more familiar than what is being introduced.) This imperfect mapping does not matter because the use of analogy is not just (i) saying 'X' is in some ways a bit like 'A', as having established that anchor in the learner's prior experience, the teacher develops the comparison by exploring with the learners (ii) the ways in which the two things are alike and (iii) the ways they are not alike, and so starts to build up the learner's familiarity with the nature and properties of X.
carefully analyse the analogy in advance and be confident that the analogy, and, in particular, the features of the positive analogy that are useful for teaching, are indeed already familiar to learners in the class;
be explicit about the use of the analogy as a tool, a kind of model or device for generating conjectures to think about;
be very explicit about the structural features being mapped across, so it is very clear which features of the analogue are being drawn upon to introduce the target knowledge…
explore aspects of the negative analogy that could mislead learners (perhaps invite learners to consider other features of the analogue and suggest aspects that may or may not transfer);
consider the analogy as part of a scaffolding strategy – an interim support to be withdrawn as soon as it is no longer needed as learners are comfortable with the target concept."
A weaker technique than analogy is simile: simply pointing out that X is like A. This is clearly not going to do the work of an analogy, as when introducing a whole new theoretical concept, but has a role 'in passing' when pointing out some single feature or function.
Simile is widely used in communicating science. There are descriptive similes that tell us that something unfamiliar physically resembles something familiar ('lacework', 'bristle-like', 'like a boat') : this technique was widely used by naturalists in describing things they observed, such as novel species, and was especially valuable before the invention of photography. Contemporary science communicators also commonly make use of this technique with more abstract comparisons to functions and properties rather than just appearance:
Now metaphor is like simile, except that the comparison is implicit. That is, consider the difference between saying:
a mitochondrion is like the engine room of a cell; and
a mitochondrion is the engine room of a cell;
As in the simile, the user does not go on to explain how the mitochondria may be understood in this way (which would constitute an analogy) and so the audience is required to do some work (so similes should only be used in teaching when the teacher is confident meanings are obvious to the learners). But with the metaphor the audience has to first even recognise there is a comparison being made, as this is not explicit. After all,the following two propositions have parallel structures:
'a mitochondrion is the engine room of a cell'
'a headteacher is the professional leader of a school staff'
In one case identity is intended (a headteacher IS the professional leader of a school staff), but in the other case there is only a figurative identity: a mitochondrion is not an engine room (even if that could be the basis of an analogy that could be productively explored). So, I advise teachers to avoid metaphor in their explanations, and to always make it clear they are using a comparison. It may seem obvious that a tiny organelle is not (and cannot be) the same thing as the engine room in a ship; but why add to the learner's task in making sense of teaching by adding the need for an extra stage of interpretation that could be avoided?
Manifold metaphors
That said, metaphors are very common in science communication. Here are just a few examples of many I have collected.
Perhaps we should not be surprised at metaphors being so ubiquitous because metaphor is a core feature of language. They are so commonplace that we do not always consciously notice them, but can often simply read or listen straight past them. Even if we notice there is a metaphor in a text, where it is successful we immediately grasp the meaning and so it aids understanding rather than confounding it. I am hoping that my use of the metaphor 'anchor', above, worked that way. You may have spotted it was a metaphor – but I hope you did not have to stop reading and puzzle out what I meant by it in that context.
An anchor (Image by Tanya from Pixabay) but what has this got to do with meaningful learning?
In particular, language often develops by metaphor. So a term that is used initially as a metaphor, sometimes get taken up and repeated to such an extent that some decades later it is treated as a conventional meaning for a term and no longer considered a metaphor. Thus the language grows. So 'charge', in 'electrical charge', was initially a metaphor, an attempt to describe something new in terms of something already familiar (the charge that needed to be placed in a firearm ready for the next shot) but is not considered so now. Sometimes the 'new' meaning comes to exist alongside the original as a kind of homonym (as separate meanings – as with the word 'bank' when referring to a river bank and a financial institution), and sometimes the original meaning falls out of use (as few people use firearms today, and even fewer charge them with shot and gun powder before use).
So, terms that are at one time metaphorical can become 'literal' over time, and these are sometimes called deadmetaphors. They are also known as historical or frozenmetaphors. The latter term appeals (although it is a metaphor, of course! – words do not actually freeze) because it suggests a change of state that may take some time. That is, there are active metaphors, and frozen metaphors, and then some 'freezing metaphors' that are beginning to be widely understood directly without being understood as figurative, but where this transformation is not yet complete.
I am sure there are plenty of terms that are in common use in the language where, if people were asked, some, but not all, would recognise them as metaphorical (dyingmetaphors? freezingmetaphors?) – and where perhaps decade-on-decade repeat surveys would show some of these had died/frozen, while new metaphors were appearing, becoming widely used, and slowly starting to solidify.
At the risk of pushing an analogy too far, we might note that the state of a sample of a substance depends on the conditions (there are no ice sheets over the Caribbean islands), so if we extend this freezing metaphor, might we find metaphors that have frozen in some environments but are still fluid in other conditions?
Zombie metaphors?
Actually, I think this is likely very common in technical fields like the sciences. I have written here about some of the language used by astronomers when discussing the births, life-cycles and deaths of stars.
Clearly these terms were introduced metaphorically. But now they are treated as if technical terms – so, now, stars really do get born, and really do die because these terms now refer to what actually happens to stars, rather than just to processes that had some similarity to what happened to stars.
I think this is potentially problematic from an educational perspective, as the novice who reads a popular astronomy book or listens to a podcast or hears a news report where stars are said to be born, live out their long lives, and die, is unfamiliar with the astronomical processes labelled in this way, and can only understand these terms metaphorically by reference to how familiar living [sic, non-figuratively living] things are born, live, and die. A pet dog that dies is no longer around, but a large star that 'dies' in a supernova explosion may then live on as a neutron star – a bit like some phoenix that rises from the funeral ashes to be reborn.
Reincarnation? The Crab Nebula as seen by the Hubble Space Telescope (HST). The Nebula is a Supernova Nebula — One formed from a supernova which left a millisecond pulsar at its center. So was the explosion the death of as star – or was it just a transition to a new phase of the star's life cycle?
I am not suggesting that people will be generally confused about heavenly bodies being actually alive (even if for many centuries they were widely assumed to be so – many people seem to have thought stars and planets are living beings like humans), but because – for the experts 'born', 'live', 'die' are no longer metaphors – they may be are used without awareness of how a novice may struggle to fully appreciate their 'technical' implications.
So, in a sense, these metaphors become 'undead' (like the neutron star?) as they pass from the expert's text to the novice's mind. They are phantom metaphors in the sense that they will manifest as 'living' metaphors to the uninitiated even though the expert user knows they have (through habitual use) been put to death.
Not just out of this world…
I suspect that there are zombie metaphors in use not just in astronomy, but in many technical fields. This means that any of us who are reading 'out of specialism' are likely to mistake phantoms for live metaphors even when an author or speaker is using a term non-figuratively with a meaning that has long ago solidified in that specific discourse environment.
When a pure substance freezes it may exclude impurities. So, for example, a sample of sea water will start to freeze, and the ice forming will exclude the salts dissolved in the water (so the salt concentration in the remaining solution increases). When a metaphor freezes to become a technical term it retains the aspect of the comparison that were originally intended figuratively, but not other features that are not relevant – they get 'frozen out' so to speak. The expert has in mind the 'purified' meaning, and does not bring unintended associations to mind. But the non-specialist has no way of knowing what is the refined meaning and what is just semantic residue.
Figuring out erythrocytes…
Consider, for example, a textbook chapter entitled "Anemias, Red Cells, and the Essential Elements of Red Cell Homeostasis" (Benz, 2018). This chapter uses a range of figures of speech to help communicate technical ideas. Some of these can be glossed:
There are also a couple of places where phrasing might be seen to move beyond simple metaphor to anthropomorphism: that is, writing that seems to imply non-sentient entities have preferences and desires or act after conscious deliberation:
The chapter also refers to the proteins known as Ankyrin. This is a technical term of course. A review article relates that
"Ankyrin is a binding protein linking structural proteins of the cytoplasm to spectrin, a protein present in the membrane cytoskeleton in human erythrocytes that functions as an anchoring system to provide resistance to shear stress."
Caputi & Navarra, 2020
Indeed, ankyrin gets it's name from the Greek word for anchor. So ankyrin is not a metaphor, but derives its name metaphorically in relation to its perceived function.
Ribbon diagram of a fragment of the membrane-binding domain of human erythrocytic ankyrin (left-hand image, from Wikipedia commons), member of a class of proteins named after an anchor (right-hand image).
But I also noticed a number of other terms which manifested as metaphors, but which I do not think would be considered metaphors by specialists. In the field, they would be dead metaphors, but to a novice they might appear as phantoms, assumed to be meant metaphorically:
These can seem to be figures of speech, with the fluid quality of offering the reader the creative act of deciding which properties to transfer across from the metaphor/simile: but actually are all widely used terms in the field, and so actually have definite 'frozen' meanings. A vascular tree has branches (and twigs) but no leaves or fruits.
Perhaps there is not too much potential here to confuse readers (especially given the intended readership for this particular text would be professional / graduate), but it does reinforce the idea that communicating science is a challenge when not only, as is often noted, so much of the language of science texts is technical; but a lot of technical terms are dead metaphors: with frozen meanings that have the potential to melt back to life, and invite more fluid interpretations from learners.
Work cited:
Benz, Edward J. (2018) Anemias, red cells, and the essential elements of red cell homeostasis, in Edward J. Benz, Nancy Berliner, & Fred J. Schiffman, Anemia. Pathophysiology, Diagnosis, and Management, Cambridge University Press, 1-13.
Caputi, Achille Patrizio & Navarra, Pierluigi (2020) Beyond antibodies: ankyrins and DARPins. From basic research to drug approval. Current Opinion in Pharmacology, 51, April 2020, pp.93-101.
Lemke, Jay L. (1990) Talking Science: Language, Learning, and Values, Bloomsbury Academic.
Taber, K. S. (2015) Epistemic relevance and learning chemistry in an academic context. In I. Eilks & A. Hofstein (Eds.), Relevant Chemistry Education: From Theory to Practice (pp. 79-100). Sense Publishers. [Download chapter]
"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.
"in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals have to work a lot harder to get to the ozone layer"
Language as a source of understanding – or confusion
Language can seem more like sorcery than science.
A person has an idea, something that is an internal, personal, mental experience, and by making some sounds or inscribing some symbols on a page or board, another person can acquire the idea.
But, like all powerful magic, it only works in the right circumstances, when the ritual is followed carefully – or else the spell may be broken. In other words, although it is quite amazing how we can effectively communicate through language (something humans have evolved over an extended period to be able to learn to do), successful communication is by no means assured. Teachers are only to well aware of that. A carefully designed, clearly explained, well-paced, presentation may lead to
And, indeed, sometimes in the classroom the same presentation can lead to all three. Communication is effective to the extent it is designed to fit with the characteristics of the 'receiving device'. And just as an F.M. transmission will not be effectively picked up by a radio tuned to medium wave or long wave frequencies (or, for young readers, who only know about digital radios – perhaps think about those times when you have a device with one type of output cable, which you are trying to connect to another device which only has input sockets for other types of connector), every learner in the class brings a unique set of interpretive resources for making sense of teaching.
A large part of the work of the teacher (or other science communicator) is helping to make the unfamiliar seem familiar by using language to describe it, or comparing it to something learners will hopefully already be familiar with.1 We use various comparisons like analogies (e.g., 'molecules in a solid are like angry dogs on short chains') and figures of speech such as similes ('an immune response is like a fire'), to help learners get an initial image they can understand, even if often this is only a starting point that needs to be further developed. The teacher, then, is operating with a model (if sometimes only a tacit one) of the resources available to learners for interpreting teaching – and clearly there is a limit to how much teachers can know about what their students are already familiar with.
These kind of tropes (similes, metaphors, etc.) are also found in popular science writing, science journalism, and scientists' own accounts of their work. Since retiring from my own teaching role, I have had more time for reading, and have become quite obsessed with just how common such comparisons are -as well as how obscure some examples seem to be.
That is, figurative language is meant to communicate by linking to something already familiar, but sometimes I do wonder just what the average reader of popular science works or science journalism make of some of the examples I come across. If I was still in post (and had the energy to match my inquisitiveness) I would love to set up some research to find out just what learners would make of some of these examples. Some instances, I am sure, are clear enough, but others seem to require much interpretation or draw upon references that may not be familiar. In the case of historical writings, what were at the time useful references may now be archaic (as when Charles Darwin describes the shape of part of a flower as being like those devices used in London [sic] kitchens to catch cockroaches – you know the ones!)
In some cases I suspect I can only understand the comparison because I already know the science. If you want some convincing of that, you might like to take a look at some examples I have noted down and see which you feel are clear and obvious enough to get an idea across to someone new to the science:
A particular type of figurative language is anthropomorphism where we refer to non-human entities (ants, trees, crystals, clouds, etc.) as if they were humans with human attributes – feelings, competencies, thoughts, motivations, desires and so on (e.g., 'the biosphere has learned to recycle phosphorus'). When anthropomorphism occurs in scientific explanations it can be considered as a kind of pseudo-explanation: something which gives the impression of an explanation, but without employing valid scientific concepts and reasoning.2 (The biosphere has not learned to do anything.)
Although anthropomorphic language may only be used figuratively, and so is not meant to be taken literally, learners may not fully appreciate this. How many students, even at A level, think that chemical reactions occur because the atoms involved want or need to acquire full electrons shells or outer-shell octets? That is a rhetorical question – but I know from experience, many. (Of course, it is a nonsense, even in its own terms, as nearly all the reactions learners meet in school science involve both products and reactants which fit the octet rule.) 3
But then, sometimes, such figurative language offers economy, avoiding the need for complex explanations. So, perhaps there is a balance of considerations – but I am always somewhat wary of anthropomorphic explanations in science.
Hard working chemicals?
These thoughts were (once again) provoked by something I heard on a podcast this morning. I was listening to an episode of the BBC Inside Science programme/podcast, and heard:
"…our aircraft only really release chemicals up until about ten to twelve km, whereas these rockets are going all the way to eighty, a hundred kilometres, so putting these chemicals into multiple layers in the atmosphere. One of these layers is a layer of ozone that is crucial for protecting us from harmful UV radiation. And so, you know, in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals have to work a lot harder to get to that layer, but now, with rockets, we can just put them directly into that layer."
Prof. Eloise Marais (Professor of Atmospheric Chemistry and Air Quality, UCL)
Now what struck me was the phrase " the chemicals have to work a lot harder to get to that layer". This is anthropomorphic as it implies that these chemicals are deliberately acting in order to reach the so-called 'ozone layer'.4 Of course they are not. These are just natural processes – physical processes that do not involve any chemicals working hard. Indeed, the molecules of these chemicals are passive subjects moved around without their knowledge or consent! (Because, of course, they are not the type of entities capable of knowing anything or giving consent, let alone actively working towards a goal.)
But the phrasing was economic. I challenged myself to rewrite the phrase "in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals have to work a lot harder to get to that layer" without the anthropomorphism.
anrthropomorphic
rewritten
"…in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals have to work a lot harder to get to that layer…"
"…in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals take a lot longer to reach that layer because this relies on the diffusion of gas molecules through the air, and the effect of convection currents mixing up different regions of the atmosphere…"
Now, I am not an atmospheric chemistry expert (unlike Prof. Marais) but that seems a more scientific explanation. And I would imagine that in her mind Prof. Marais understands this process in a similar – if likely more sophisticated, and certainly more detailed – way. But she chose (perhaps deliberately, perhaps not given our use of language in speech is partially automatic – we do not fully script what we are going to say before we start to talk) to anthropomorphise rather than specify a scientific mechanism. I doubt many listeners took the figure of speech here as literal (although you never know!) and Prof. Marais kept her comments more economic by not introducing ideas that were perhaps peripheral to her message: anthropocentric inputs into the atmosphere reach the stratosphere, where some polluting chemicals react with ozone, much more readily if we send them directly there by rocket, rather than release them near the ground.
Anthropomorphism, as a kind of humanising language, has been said to be useful to engage learners, as well as sometimes (as in the example here) being a way to avoid the need to go into technical details that may be quite unrelated to the main point being made. People can respond well to anthropomorphism, being more attentive and receptive to ideas presented in human terms (so, perhaps referring to hard working chemicals engaged listeners more than simply saying: "in the past we have tried to address this by controlling industrial sources that are close to the earth where the chemicals take a lot longer to reach that layer").5
Therefore, I am not saying this was wrong or poorly judged, but whenever I hear such examples it makes we wonder if the causal listener who is not a scientist would notice the anthropomorphism, and realise that it was being used as an engaging alternative to a dry technical phrase, or even as an abbreviated placeholder for a more technical description. And this is not an example of something rare – anthropomorphic explanations are again very common in science writing and discourse. I have compiled some examples that I have noticed:
In some of those cases I suspect non-scientists may well find the language used quite persuasive, and not appreciate that 'explanations' presented in anthropomorphic terms are not scientifically valid. So, although I can certainly see the case for its use, I tend to be uneasy when I hear or read anthropomorphic statements that stand in the place of scientific accounts, as I know they can be persuasive and are sometimes adopted as explanations by learners.
I wonder what other science teachers think?
Notes:
1 In order for learners to make sense of abstract, complex ideas these need to:
preferably be experienced or demonstrated; or when that is not possible,
modelled/simulated; or when that is not possible,
explained in terms of ideas the learners can already relate to.
2 There are different types of pseudo-explanations, such as tautology, presenting a description as if it is an explanation, offering a label as though that explains, etc.
3 I think this is perhaps the most widespread type of misconception in school chemistry – that reactions occurs so that atoms can get full shells (or octets), that entities with full shells are always the more stable, that atoms of ions with fulls shells cannot be ionised, that atoms will spontaneously lose electrons to get a full shell, etc., and, indirectly from this, that the bonding power of ions is determined by electrovalency (so, in NaCl, the Na+ ion and the Cl– ion are each thought to be restricted to forming one ionic bond).
4 Experts, such as science teachers, know that the 'ozone layer' is not a layer of ozone, but it should not surprise us when learners think that is what the term means!
5 Perhaps, metaphorically, "…the chemicals have to work a lot harder to get to that layer…" is a 'warmer' expression than the 'colder' phrase "the chemicals take a lot longer to reach that layer"?
Does discriminatory language suggest biologists are ashamed of some of their ancestors?
Keith S. Taber
Historically, some offspring have been classed as illegitmate and so unable to claim the same rights as those recognised as legitimate children.
But are biologists treating some of our ancestors as illegitimate?
This is a bit like judges in a court of appeal announcing their decision as "the appeal is successful – the criminal is innocent".
I was listening to an old podcast recently. The first item was about how nearly all Inuits have a particular genetic variation that is adaptive to living in the Arctic with the extreme cold and restricted diet that involves. These particular genes are not unique to that group, but are only found with much lower incidence in other groups living elsewhere. These genes are in the human 'gene pool', but have been strongly selected for among Inuit communities where they are now ubiquitous.
However, what was seen as especailly interesting about this particular genetic resource was its 'origins' – from another species. These genes are considered to have arisen in Homo sapiens by transfer from another species: Denisovans.
I do not think that any present day humans have any Denisovan or Neanderthal genes
So, the claim is that modern humans have some Denisovan genes just as (according to scientific studies) we have some Neanderthal genes, and probably genes from some other archaic human species as well. Actually I argue below this is not the case, but my argument is in terms of semantics rather than being a rejection of the substantive claims.
So – spoiler alert – I do not think that any present day humans have any Denisovan or Neanderthal genes, but I am happy to accept that we may have genes acquired from other human species such as the Denisovans and Neanderthals. To explain the distinction it is useful to ask how did 'we' modern humans come to be given this genetic gift?
Who counts as an ancestor?
What I thought was of special note in this item of the episode of BBC Inside Science was the language in which it was explained. The programme description suggested:
"Can Inuit people survive the Arctic cold thanks to deep past liaisons with another species? Adam Rutherford talks to geneticist Rasmus Nielsen who says that's part of the answer. His team's research has identified a particular section of the Inuit people's genome which looks as though it originally came from a long extinct population of humans who lived in Siberia 50,000 years ago. The genes concerned are involved in physiological processes advantageous to adapting to the cold. The conclusion is that at some point, the ancestors of Inuits interbred with members of this other species of human (known as the Denisovans) before people arrived in Greenland."
https://www.bbc.co.uk/programmes/b08558n5
The expert interviewed on the episode explained:
"…what we think we can conclude now is that in fact this D.N.A. that we find in the inuits, that we think was important for them in adapting to this extreme environment, that actually was transferred to them from Denisovans or from somebody related to the Denisovans, and by transferred, how does that work, well that works by interbreeding, so in the past we know there has been some interbreeding between these Denisovans and the ancestors of modern humans, and when they interbreed of course you transfer D.N.A."
Prof. Rasmus Nielsen, University of California at Berkely
At the end of the item, the presenter reiterated:
"So, the ancestors of Inuits bred with the Denisovans, and the gift of that blessed union, were genes that helped with cold adaptation."
Dr Adam Rutherford
Now I am not a biologist, and so am perhaps I missing a nuance of how terms tend to be used in biological discourse, but all three of these statements seem to include the same logical fault.
The 'interbreeding' events being referred to are a great many generations back in time, but to ilustrate my complaint, I have prepared a much simplified diagram modelling the scenario presented in the programme, but with just a few generations:
A simplified representation of who counts as an ancestor – according to some biological discourses
Excluding ancestors from minority groups
Now it seems the account being presented by biology here only makes sense if we distort the usual meaning of 'ancestor'. Surely a person's ancestors are all those people who feature on direct lines of descent to that person? In my simplified figure the individual at the bottom has eight great-grandparents.1 In my understanding of 'ancestor', each of these eight people is an ancestor of the individual shown in the final generation. If that is accepted then each of the quotes above is misphrased:
at some point, the ancestors of Inuits interbred with members of this other species of human (known as the Denisovans)
in the past we know there has been some interbreeding between these Denisovans and the ancestors of modern humans
the ancestors of Inuits bred with the Denisovans
Well, no. Surely what is meant here is:
at some point, those ancestors of Inuits considered members of Homo sapiens interbred with other ancestors of Inuits who were members of this other species of human (known as the Denisovans)
in the past we know there has been some interbreeding between these Denisovans and the other ancestors of modern humans
the ancestors of Inuits considered members of Homo sapiens bred with the ancestors of Inuits considered Denisovans
The original statements are akin to telling someone that they are the result of their parent coupling with a communist (or: an Australian / a graphic designer / a Liverpool supporter / a goth / a sociologist, etc.), as if a communist (or sociologist, or whatever) does not deserve to be recognised as a genuine parent.
There seems to be discriminatory language here, a kind of speciesism, where only those ancesters we consider part of 'our' species count as proper ancestors, and so other kinds of human are illegitimate as ancestors.
Two types of sex: Normal sex…and something a little shameful?
This is reflected in implying that there is some abnormal type of sex going on between these different classes of humans. Normal sex is all about genetic recombination (that is, the advantage of sexual over asexual reproduction is the 'shuffling' of genes from two individuals to give different, and pretty much unique, genetic permutations in the offspring).2
But the 'interbreeding' between species is described in particular language – a 'transfer' of genes. Now, in some parts of the living world we do see a kind of transfer of genes where one organism 'donates' copies of some its genes to another organism.
That is somewhat different from breeding in human populations that relies on meiosis to produce gametes that each have half of the parental nuclear genes; and which co-contribute to a new version of the human genone when fertilisation occurs due to the fusion of two gametes – nothing is actually transferred. Like downloading a file from a website where there is not really a 'file transfer' but the copying of an orginal that remains where it was. 3
That process of sexual reproduction is what occured when two ancestors bred – regardless of whether both were Homo spaiens or one is Denisovan (or Neanderthal or some other type). So, what is meant by 'transfer' is presumably that some 'Denisovan genes' were copied into the H. sapiens gene pool.
The species question
This description would make sense if species were ontologically discrete entities. But, as Darwin (1959) long ago realised, there are not sharp, absolute distinctions between species, and biological demacractions of species are more matters of 'convenience'. If we have some 'Denisovan D.N.A.' or 'Neanderthal D.N.A.' in our genomes, then – assuming the Denisovans or Neanderthals did not have genetic engineering skills long before 'us' – then the Denisovans or Neanderthals are our ancestors.
And why not? The very logic of evolution is that if we go back far enough in time we have:
non H. Sapiens, indeed, eventually,
non-human,
non-primate, even
non-mammalian, ancestors.
Humans today may be different from Denisovans or Neanderthals, but then we are also surely somewhat different to early sapiens who had not yet got friendly enough with Denisovans or Neanderthals to have received 'transferred' genes.
So, is the language here, of transferring genetic matieral by interbreeding (contrasted with the genetic recombination occuring when speciments of H. sapiens bred), reflecting a traditonal view of species that Darwin invalidated?
That is, under the old definition, members of two different species cannot breed to provide offspring, or at least, not fertile offspring. But the Denisovans and Neanderthals that 'interbred' with our (other) ancestors and passed copies of their genes indirectly down to humans today, clearly had no trouble in that department. Nor can it be argued that these were geographically separated populations that never overlapped, and so can be considered consequently as if separate species. Clearly there must have been some degree of co-habitation between these groups to allow matings to occur.
There may be significant enough objective differences between the morphology of early Sapiens, Denisovans and Neanderthals for biologists to feel these should be considered different species, but the notion that Denisovans and Neanderthals can simply be considered as being distinct entities on other discrete branches of the evolutionary bush is challenged by the evidence that at least some of themare among our direct ancestors. Perhaps only a minority of the Denisovans and Neanderthals that shared the world with Homo sapiens have offspring alive today – but then that would likely also be true for their sapien peers.
The science teacher and philsopher Gaston Bachelard has described how science is often impeded by retaining the 'fossilised' infuence of historical ideas that science has supposedly moved on from. Is this an example? The BBC Inside Science podcast seems to be telling us we need to rethink what we mean by our ancestors, whilst using that very word without taking this into account. This is a bit like the judges in a court of appeal announcing their decision as "the appeal is successful – the criminal is innocent".
No more discriminatory language
Or, is this an example of using language loosely to communicate effectively, because being precise would lead to convoluted expressions [like my 'at some point, the ancestors of Inuits considered members of Homo sapiens interbred with other ancestors of Inuits who were members of this other species of human (known as the Denisovans)']?
Modern humans do not actually have Denisovan or Neanderthal genes, or Denisovan or Neanderthal D.N.A., but rather have some genes that are identical (or very similar) to – in effect indirect copies of – some genes of their Denisovan or Neanderthal ancestors. And no doubt those genes (or rather identical genes 4) could also be found in some of their even more distant ancestors who are in turn considered a different species again. After all, humans share many genes with many other living things, such as bananas, so references to 'human genes' or 'Denisovan genes' it is a bit like referring to characters in the Roman alphabet as 'English letters', when they are equally 'French letters' or 'Dutch letters', etcetera. They are letters that appear in English language texts, but they are not exclusive to English language texts: just as there are genes found in human genones that are not exclusive to human genones.
Referring to 'Denisovan genes' or 'Denisovan D.N.A.' speeds communication. But it has potential to mislead the non-specialist.
So, I object to any of my forebearers who happen not to be considered specimens of Homo sapiens being said to 'transfer' genes when they 'interbred' with my ancestors: they are just as much my ancestors as those partners they engaged in genetic recombination with.
So, please, no more more discriminatory language directed against some of our ancestors, just because they were in minority human groups.
Work cited:
Bachelard, G. (1938/2002). The formation of the scientific mind. A contribution to a psychoanalysis of objective knowledge (M. McAllester Jones, Trans.). Clinamen Press.
1 In a genuine family 'tree' there are likely to be mulitple offspring from some unions, and indeed often some people will parent children with multiple partners – but this would over-complicate the diagram as it is not central to the argument being made.
In a case such as this with just four generations we would expect a person to normally have eight different great grandparents who are all unambigously three generations distant from that individual. As we consider much longer time periods it becomes increasing likely that the same ancestor occupies several (indeed, many) 'slots' on the tree (you have many fewer than 2ndistinct ancestors going back n generations once n gets large) and indeed these individuals may appear in the tree across several generations.
Another way of thinking about this is that not all of your (great)n grandparents will have been alive at the same time, once n starts is more than a small number. As an extreme case, it is quite possible that the offspring of a union between a 50 year old man and a 20 year old woman (unusual but not unknown) might quite feasibly have had one pair of grandparents who died before the other grandparents were born. This is unlikely, but plausible. With each additional generation it becomes less likely that all your ancesters at that remove were alive at the same time.
2 The advantage of asexual reproduction is that the outcome should be a viable specimen in the envrionment occupied by the parent that has been cloned. Perhaps the most advanced reproducers are those species that are able to reproduce by either strategy?
3 And, just as teaching does not seek to 'transfer knowledge' from the teacher.
4 Perhaps one issue here is how we can use the term, gene, to refer both to functional sequences of nucleic acid in abstract (as we might refer to 'the carbon atom' when we mean all and any carbon atoms, not a specific one), and actual material samples. In the first sense, a parent and offspring can share the same gene; in the second sense, a copy of a parent's gene can be passed to the child. In neither sense does the 'transfer' of genes occur.
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
