"Our everyday world, plainly moulded by subatomic forces, also owes its existence to our universe's well tuned expansion rate, the processes of galaxy formation, the forging of carbon and oxygen in ancient stars, and so forth. A few basic physical laws set the 'rules'; our emergence from a simple Big Bang was sensitive to six 'cosmic numbers'. Had these number not been 'well tuned', the gradual unfolding of layer upon layer of complexity would have been quenched. Are there an infinity of other universes that are 'badly tuned', and therefore sterile? Is our entire universe an 'oasis' in a multiverse? Or should we seek other reasons for the providential values of our six numbers?"
Martin Rees
Martin Rees: Just Six Numbers
There are a small number of key physical constants that had they been slightly different would have led to our Universe developing very differently.
Figures of speech
Perhaps appropriately for a book that is about 'just six numbers' I wish to examine some of the figurative (see what I did there?) language used by an author in seeking to explain some abstract scientific ideas for a popular readership.
I have written quite a lot in this blog about the kinds of metaphorical and other figurative language used by teachers and other science communicators when trying to explain science, and here I want, in particular, to make a point about context: about the context in which such language is used,
"A technique that chemistry teachers share with teachers of other disciplines, as well as other communicators (such as journalists, but, indeed, people in general) is to draw comparisons with (what are assumed) familiar ideas, experiences and phenomena, simply by using language. This can be in the form of metaphors, similes and analogies…and these can sometimes be anthropomorphic in nature – that is, to put something (such as the 'behaviour' of a molecule) in terms of human feelings, thoughts and experiences.
Although, later, I make a distinction between metaphors, similes, and analogies – in practice, it is not always straightforward to distinguish between them. For example, our judgement about which category some comparison belongs in may change depending upon whether we consider a specific statement by itself, or examine it in the wider context in which it occurs. That is, material of relevance that is not explicit in the statement may be being assumed by the communicator as it has been previously referenced or alluded to, as part of the wider text or dialogue."
Taber, 2024
In a science classroom, that context might include earlier topics presented in the curriculum; some reading that was set ('homework') as preparation for class; what the teacher said last lesson; or something learners have just been asked to try out or to observe. In a text, such as an extract from a popular science book (as in the example above from 'Just Six Numbers'), the context that is provided is the rest of the text, and especially the part of the text preceding that extract – as this is the part an author can reasonable claim you 'should' have already read (though readers are of course free to engage with a book as they wish).
That is, 'should' does not here imply an imperative, but rather the author's reasonable defence that if you choose to read the text out of order, or just dip in, then the author cannot be considered to be responsible for anything you may have missed that is needed to make good sense of what is presented later in the book. Any teacher who has pointed out to a student claiming not to follow in class that they 'might have understood better if they had not missed the previous lesson' can appreciate this logic.
Interrogating the text
So, bearing in mind I have not reproduced the whole of Prof. Rees's book, but just an extract out of context, I would like readers to consider the extract at the start of this posting, and to ask themselves:
what does this mean?
how do I know what it means?
what would it be reasonable to expect a 'typical' general reader (one with an interest in the topic, but not being a science specialist) to make of the extract?
what terms or phrases in this extract can be considered to be used figuratively here (that is to not here strictly mean what those words, strictly, mean?)
I noticed this extract was rich in figurative language, such as metaphors with teir 'hidden' meanings. And then I re-read it, and further noticed I had actually read-through some of the metaphorswithout initially noticing them – so it was actually even richer in such language than I had first realised.Often we do not notice the metaphors and similes used in texts, but rather simply automatically make sense of them as part of the text. 1 Usually we read a text for meaning (semantics) rather than choice of vocabulary, and we 'automatically' (preconsciously) analyse the text in terms of pragmatics – that is what a term is likely to mean in this specific context:
I am going to the bank to cash this cheque
I am going to the bank to dangle my feet in the river
I am going to the bank to see if we have any AB negative
Language is fluid (so to speak)
The extract from Rees's book presents a range of terms which need to be interpreted to identify what they mean within this particular context. Now I do not intend this as a criticism: I think two relevant general principles here are that:
It is the nature of natural language (e.g., here English – 'other natural languages are available') to be somewhat fluid (so to speak), with many words and phrases being open to somewhat flexible use across a range of meanings: so it is generally the case that words, phrases, sentences, paragraphs, etc., take their specific meanings within a text from the wider textual context.
And indeed, in everyday situations, also the broader shared context. If someone is shouting out 'Fire!' this may mean something quite different in the context of a quiet accounts department in a tall office block than in the context of a Fascist's state's execution of a political prisoner – or indeed at an Arthur Brown concert.
When musician Arthur Brown performed his song 'Fire', and sang loudly 'Fire!', he did not intend his audience to leave the venue. (Though given his stage headgear, which sometimes malfunctioned, a careful risk assessment might have suggested that course of action.)
It is in the nature of unfamiliar abstract science concepts that they will not make good sense to learners (/readers/listeners) who cannot relate them to something already familiar. So science teaching (and science communication more generally) is often about making the unfamiliar familiar by showing how this unfamiliar idea is a bit like something you already understand and are comfortable with. This unfamiliar thing is not the same as that familiar thing (and differences will need to be addressed), but there is a similarity which can be used as a starting point for making the unfamiliar familiar.2
Using figurative language to explain science is therefore not a bad thing – although there can be poor examples which do not help or only confuse as well as very productive examples that support learning (and this may be relative to individuals, as each learner brings their unique set of 'interpretive resources' to make sense of learning). And indeed, sometimes, it may be a necessary teaching tactic if the gist of an abstract idea is to be effectively communicated. My discussion of examples in this blog then is certainly not intended to mock or deter this technique, but rather to highlight something of the complexity of using figures of speech in explaining science.
Let's start at the end…
The extract I present above is from the end of the book, as Prof. Rees concludes by summing up what he has been setting out to readers. This is then (most of) the very final paragraph in the text, so it is quite reasonable for Rees to assume that a reader getting to this point will have the context of having (in effect) read the book.
If you have not read the book, then perhaps that extract above may be too dense with ideas and figures of speech for you to fully appreciate it. But that depends: if you are a cosmologist or astronomer or physics teacher, then it is quite likely that you are sufficiently familiar with the ideas being communicated (and indeed some of the metaphorical language being used) to find the extract unproblematic. As always, each person brings their own unique set of interpretive resources to make sense of a text.
But, as an example, I am going to deconstruct the text to highlight some of the 'interpretation' involved in understanding it. Now, there are references made in the extract to scientific ideas which had been discussed earlier in the book, such as that of a multiverse, the Big Bang, and the expansion of the Universe. But my focus is on the non-technical figurative terms, or at least those that are likely seem non-technical to the general reader. 3
Tuning up the Universe
The terms well tuned (and in the marked form, 'well tuned') and 'badly tuned' are applied to the Universe. This notion has been well developed earlier in the preceding text. Tuning is originally a term used in relation to musical instruments that is figuratively used in other contexts. One might tighten the tension in a guitar string so it plays at the right frequency to give the required musical note.
Engines are also said to be tuned. Presumably this was originally used metaphorically, and because the process was done 'by ear' – by listening to the engine 'note'. Language develops over time so that engine tuning has become an accepted term and is no longer metaphorical. However, clearly there is something of a stretch (so to speak) to extend the notion of tuning to a universe. 4
Being well tuned (or badly tuned) is anthropomorphic or teleological. That is, there is nothing intrinsically right or wrong about a universe having particular qualities. But for a universe to have been suitable for us to appear it needs certain properties – a well tuned universe is one that has particular qualities that are seen (by someone) as desirable. Being well tuned might then imply developing in accord with some sense of purpose. (Again these ideas had been addressed earlier in the text by Rees for anyone reading the whole book.) 5
Moulding and forging
To mould means to shape something, perhaps (as with clay) by manipulation or (as with cooling molten metal) by pouring in a pre-shaped mould. The term is widely used metaphorically, and here the term is extended to the effects of subatomic forces.
Forging is a term relating to metal working, where a blacksmith (for example) uses a forge as a hot environment to shape (and sometimes harden and temper) metals. The forge is (in human terms) very hot – although the forging is itself achieved by hammering the metal once it is hot enough to be sufficiently malleable. The term is again commonly used metaphorically – perhaps a famous example was a much quoted speech by UK Prime Minister Harold Wilson who referred to how his government was
"…re-stating our Socialism in terms of the scientific revolution…. Britain that is going to be forged in the white heat of this revolution…"
The processes by which heavier atomic nuclei (i.e., anything heavier than helium nuclei in this context) are produced are nuclear process that only occur under what we would consider extreme conditions such as in the cores of suns (often considered 'nuclear furnaces') or during supernovae explosions or other events that irradiate material in space with highly energetic radiation. There is no forging as such, but the conditions may be seen as akin to those in a forge – e.g., unusually hot. If using 'forging' metaphorically to refer to the nucleosynthesis of elements, it is important to note that in the scientific context an important aspect of the original meaning does not transfer across: the blacksmith uses his forge to deliberately produce something, perhaps horseshoes, whereas there is no deliberate purpose or design to the nuclear changes going on in stars. 6
Unfolding the layers
The "gradual unfolding of layer upon layer of complexity" offers something of a mixed metaphor. We might argue that by definition it is only possible to unfold something that has previously been folded. But metaphorically we might see the opening of a flower, with its sepals and petals and pistil and stamens as being like a kind of unfolding – we can imagine these structures have been neatly folded away, though of course that never happened.
We might also say, metaphorically, that a story unfolds as new themes and characters and episodes are introduced (though here there is a sense that the author who planned the narrative has likely story-boarded this level of detail, and then (metaphorically) folded it away in the structure of the narrative.
The (metaphorical) unfolding referred to by Rees seems to be akin to that of a flower, in that as the Universe ages new structures appear through a developmental process just as the new organs appear on a plant when the flower develops. (Incidentally, astronomers tend to refer to the 'evolution' of the Universe although clearly there is no evolution in any sense parallel to that seen in organisms – through variation and natural selection. A better analogy would seem to be with the development of an individual living thing that passes through different stages of life.)
The layers of complexity are surely metaphorical, as it is only human cognition which finds it convenient to see them as layers. We can see the world in terms of a series of strata of increasing complexity with new phenomena emerging at the different 'levels': so perhaps sociology from psychology, which emerges from biology, chemistry, and ultimately physics.
We can consider structure in the Universe at 'levels' such as galactic clusters, galaxies, stellar clusters, solar systems…nuclei, quarks, etc. But in the Universe these do not occupy actual levels, rather this is an abstraction we impose to help analyse the complexity (we 'dig down' to the 'level' of molecules or nuclei or quarks or whatever). This is probably obvious to most readers as we are so used to imposing metaphorical layers on conceptual systems (but it might mystify a perfectly normal modern human who had not received a formal education 7).
Quenching
Quenching takes us back to the forge. I strongly remember metal work at school when I was eleven, and having to heat a piece of metal till it glowed a particular colour before plunging it into cold water to 'quench' it: to cool it rapidly. Having hardened the metal it was next 'tempered' by heating again before being thrust into sand to cool less rapidly. While I have forgotten much I did at that age at school, the sheer fear of using lathes, massive drills and blowtorches provided an emotional quality that seems to have 'forged' those memories. (But I do still have the screwdriver I made.)
One can also use water to quench a fire or one's thirst – so quenching is a process of removing. In Rees' text the metaphorical layers of complexity would not have occurred, and so could not have been metaphorically unfolded if the 'six numbers' had had very different values. Some minor shift in one or more of those numbers may have changed the timescale of universal development, so that some of the processes and structures in our Universe would not have had time to develop, or to have developed as much.
In either case it is only a potential which is 'quenched' as nothing that comes into being is removed, and there is no active quenching agent – it is more a (metaphorical) lack of formation of the combustible material than the action of some water to put out a fire.
Does this make for a poor metaphor? This is quite difficult to judge as words have aesthetic and other qualities (such as salience) as well as literal meanings, and a metaphor which seems less apt semantically may still have some impact on a learner/reader/listener and lead to engagement with the ideas being communicated. (And this will vary between individuals of course.) So the crux of the question of whether 'quench' is a good choice here is an empirical one: if it helps communicate Rees's intended meaning to (most of) his readers then it is effective: if instead it mainly mystifies or confuses or misleads them, then not so.
A desert of sterile universes?
If there are other universes which developed with different values of the key cosmic constants (constant, in any particular universe, that is) then in many of those universes there would be no galaxies and stars. And in some that did lead to galaxies and stars there would be no opportunities for life to evolve (if stars burned out rapidly, for example). And in some that gave opportunities for some kind of simple life, there would not be sufficient scope for the evolution of sentient beings capable of asking questions about other universes.
If sterile means unable to reproduce, then this is a metaphor which could be applied to any universe. 8 Sterile can also mean free from organisms (usually especially microorganisms) which could therefore seem as a non-figurative term when applied to some imaginable universes (which might include stars systems etc., but that are) incapable of supporting life.
If there is a multiverse – that is, if our Universe is one of many coexisting but completely non-communicating universes – where the different universes have widely different values of these cosmological constants, then likely most of them will not have developed with the complexity of ours, and so most would not support the evolution of life. Thus if we see the multiverse as a desert, then, metaphorically, a universe like ours would be an oasis – a small location where life can survive in the desert.
The metaphor requires us to step out of our Universe to take a view of the multiverse, and imagine a traveller moving across the desert and entering the oasis; when the 'oasis' is actually a self-contained world, not even hermetically sealed off (so to speak) from any other such worlds as it has no boundary with them, and there is no means of seeing out beyond the oasis. No traveller could move from one universe to another (so there would be no opportunity to look back in anger if they found the grass was not actually greener).
Is the universe like an oasis? (Image by AlexBishop from Pixabay)A galaxy – an island universe? (Image by Kyoung-Sik Choi from Pixabay)
Despite this, my own feeling is this metaphordoes communicate a meaning well, and it reminds me of a long-established metaphor where galaxies are seen as their own island universes in the ocean of space. 8 So again, I do not think we can judge the effectiveness of metaphor simply in terms of the technical aptness of that metaphor, but this does remind us that in interpreting a metaphor the reader or listener is selecting some, but not all, of the associations available for the term (and so of course may select different associations to those the author or speaker had in mind).
Coda: Texts may have their own dark matter
What this analysis is intended to do, is not to critique the specific figures of speech used here (which can only sensibly be evaluated by questioning a representative sample of readers who had finished the book to see how they made sense of the text), but rather to highlight just how many layers of complexity may be enfolded (so to speak) in forging even a short text, and so just how much interpretive work a reader needs to do in making sense of a text.
We think of scientific articles as being as explicit and precise as possible, and so rich in formal technical language; and this is appropriate as the intended readership can be expected to have mastered the relevant concepts and technical vocabulary necessary to make sense of such a text. But in explaining science to a non-expert audience (in teaching; in writing a popular science book) one has to mould an account to resonate with the audience members' available funds of interpretive resources. These resources may be rich and varied, but will be technically more limited.
So such texts can only be populated with the lower density of technical ideas and terminology that can either be assumed as common to the audience, or gradually introduced in the text. Technical terms therefore are widely interspersed among the 'space' of the text, with the meaning being held together by the use of figurative language such as metaphors with their 'hidden' (implicit) meanings. The work of making sense relies on a good understanding of the technical terms used, and a suitable interpretation of the supporting 'dark matter' of figures of speech.
Usually, most of this interpretive work is automatic – occurring outside the 'spotlight' of conscious awareness – but the reader still has to process the text to try and mould it into a reading that makes sense to them. A text needs to be well-tuned for its readers, or else that sense-making will be quenched, making the metaphors sterile. (So to speak.) Or worse? Perhaps being fertile grounds for unintended meanings to germinate.
This 'tuning' is always a challenge given that different readers will have different levels of background knowledge and other interpretive resources, and so may resonate across a wide range of different natural frequencies, so to speak. A well judged (tuned) book will at least largelyresonate with most of its readers regarding most of the metaphors used. Then they will likely not even notice these figures of speech, as interpretation will be automatic and the text will simply, subjectively, make sense. Somewhat like the dark matter thought to make up much of the mass of the Universe, these figures of speech hold the text together semantically without being conspicuous. Of course, sometimes the wrong feature of the metaphor may be adopted, so the reader's meaning may not perfectly match what the author intended.
There may be outliers, including perhaps some readers not well prepared to tackle the text (lacking essential background knowledge or reading level perhaps) who may find themselves in a metaphorical semantic dessert with just the odd oasis that seems fertile with meaning. (So to speak.) An author, unlike a teacher, does not have the opportunity to constantly check on how they are being understood and make adjustments, so this is an unavoidable feature of texts of this kind.
All an author can do is choose their metaphors carefully, bearing in mind their expected readership; and offer context by incrementally forging a kind of customised metaphorical lexicon across the text. 9 As Rees does in his book.
If you are intrigued by the extract discussed, and wish to know more, the full textual context (Rees, 1999) is available!
Sources cited:
Luria, A. R. (1976). Cognitive Development: Its cultural and social foundations. Harvard University Press.
Rees, Martin (1999) Just Six Numbers. The deep forces that shape the Universe. Weidenfeld & Nicolson. London.
1 By similes I mean those figures of speech which are marked by the author, for examples using inverted commas (speech marks) as in 'well tuned' as in "…not been 'well tuned', the gradual…", as well as metaphors such as well tuned in "our universe's well tuned expansion rate". Similes may also be marked by using like, as, in a sense, so to speak, etc.
Many examples of science similes are listed in 'Creative Comparisons: Making Science Familiar through Language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
We usually 'read through' such figures of speech, but as I have become rather obsessed with the use of figurative language in science I tend to notice many of them, often reading a text both for the scientific meaning and also to see the way the author is explaining the science.
3 I make this distinction because sometimes terms which are originally used metaphorically, such as the 'death' of a star, come to be habitually used; and so in effect become technical terms within a scientific field, while still appearing to be metaphorical to a non-expert in that field. They become phantom metaphors (something a non-expert will assume is a figure of speech, although it is being used as if a technical term).
4 Traditionally the Universe referred to everything there is, but (following Rees in his text) we can both consider other potential universes that could perhaps have existed instead of ours, and also that there may be totally separate non-communicating alternatives beyond what we can observer as our Universe which potentially have quite different natural laws. In this usage 'our' Universe may be one element in a 'multiverse'.
5Anthropomorphism is when an inanimate object or non-sentient organism is spoken of as though it has human experience, desires and so forth. The atom needs another electron. The virus tries to hide in the tissue.
Many examples of anthropomorphism are listed in 'Creative comparisons: Making science familiar through language. An illustrative catalogue of figurative comparisons and analogies for science concepts'. Free Download.
Teleology is about having a purpose or goal. Much of the functioning of living things seems purposeful (we can suggestion functions to the heart or to the gene as though they are working towards some outcomes, rather than having evolved to be like they are by natural selection). The idea of a well tuned universe could imply some ultimate goal (e.g., to be suitable for life to evolve) which is only achieved when the cosmic numbers Rees discusses have the 'right' values.
6 I am not here excluding the possibility that there may be a creator who has deliberately set up the system, but science is only concerned with natural mechanisms, not ultimate causes. The star has no purpose or intention – it makes heavier elements simply because that is what happens to that material under those conditions.
7 Some of the habits of mind we take for granted are acquired through the culture. For example, people with a formal academic education tend to readily appreciate the form of syllogism and how it is used. But this is something we learn from culture:
fluency in using syllogism depends upon experience that is acquired through education;
people in some traditional cultures have not received the formal education that introduces, and offers experience of thinking with, syllogisms;
therefore people from such cultures will not tend to show fluency in using syllogism.
At least this was what the Russian psychologist Alexander Luria (1976) found when he did field work among traditional cultures just being introduced (indoctrinated?) into the collectivism of the Soviet Union.
8 Of course, as our Universe is by definition all we can directly know, it could only be speculation about whether a universe could in a sense reproduce. Such speculations exist. For example an expanding universe may slow, and contract, till eventually passing through a 'big crunch' back into a singularity – which some think could rebound into a new 'big bang', perhaps with a resetting of the laws and constants of nature. There is also speculation about the singularities at the 'heart' of black holes.
At one time the galaxy (that is, the milky way, our galaxy) was seen as synonymous with the Universe. The discovery that there was other galaxies at vast distances form our own led to seeing them as other universes: each galaxy an 'island' in the immensity of intergalactic space. Now it is commonly suggested there may be other universes (many with their own vast numbers of distinct galaxies) beside our own.
9 In teaching it is usually better to use simile so that the figurative nature of terms is marked (a 'well tuned' universe), unlike in a metaphor (a well tuned universe). One common textual feature is for a term to be introduced as a simile, perhaps by putting it in square quotes, or making it clear it is only 'like' the thing being discussed; but then moving to use the term metaphorically.
In one example I read of a part of a plant being described as like a boat, but then a few paragraphs later this was referred to as the boat without being marked as a simile. A reader has to recognise the term boat is still being used figuratively. This kind of metaphoricalcreep (or metaphorical encroachment perhaps?) could be problematic if a reader forgets a simile was being used, or only starts reading after if has been introduced and marked as being a comparison.
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]
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)
(Possibly) the first in an occasional series to test the imagination of science teachers and other science communicators.
Those who explain science (such as teachers, scientists themselves, journalists) often seek to 'make the unfamiliar familiar' by suggesting that the novel scientific concept is in some ways like something else – something it is assumed will already be familiar with the audience.
Can you match the science and the comparison?
In the table below I have selected ten examples of comparisons for science concepts (from those reported on this website) – but I have separated the scientific ideas from the comparisons (and then presented both lists alphabetically).
The challenge is to see if you can identify which comparison was used in discussing which scienceconcept:
Can you work out which comparisons were used in explaining the different science concepts?
Of course, it is very unfair of me to present these comparisons stripped of any context – but that is what makes it a challenge.
[All of these examples are featured somewhere on the site, so if you give up (or wish to 'cheat') you could use the 'Search the website' box. If you admit defeat, the answers are at at the bottom of the post.]
A fun activity – with a serious point
I hope some readers may find this a fun activity for a tea break in the prep. room or as a way to relax for those now finally on Summer break. However, I think such comparison invite closer attention.
Devices such as analogies and similes are invaluable in getting across abstract unfamiliar ideas. However, choosing them is itself a challenge as the comparison has to be familiar to the learner/listener/reader or it cannot be helpful (in which case it may be demotivating as it adds an additional burden to what the person does not know!) Moreover, the learner/listener/reader needs to appreciate which aspect of the comparison is being highlighted as relevant. (In an analogy this should be mapped out – but in metaphors and similes it is left implicit).
There is also a danger that these devices – so useful for introducing scientific ideas – outstay their welcome (so to speak). An author of a popular science book may only be concerned with the reader having the (subjective) impression of understanding, feeling 'oh yes, that makes sense'; but the science teacher aims for objective understanding (that would be creditable on examination), and intends the analogy or simile to be a temporary 'scaffold' toward understanding which will not be needed once the scientific concept has been learnt and consolidated. Yet, sometimes, learners do not move beyond the comparison – seeing its meaning as literally accurate (much as learners may not appreciate that many scientific models are not intended to be realistic and complete accounts).
Science communicators – scientists, teachers, science writers and the like – are also often knowledgeable about a wide range of topics and cultural references – but these may not always be shared by some of their target learners/listeners/readers. (This may be particularly true when a source is being used in another part of the world to where it was created, or perhaps when a scientist's work is read many decades after being composed.)
These are also highly intelligent people who may have strong powers of imagination – so sometimes they may form creative connections which others may find obscure and idiosyncratic!
I was recently listening to a podcast of an episode of a science magazine programme which included two items of astronomy news, one about a supernovae, the next about a quasar. I often find little snippets in such programmes that I think work making a note of (quite a few of the analogies, metaphors and similes – and anthropomorphisms – reported on this site come from such sources). Here, I went back and listened to the items again, and decided the discussions were rich enough in interesting points to be worth taking time to transcribe them in full. The science itself was fascinating, but I also thought the discourse was interesting from the perspective of communicating abstract science. 1
I have appended my transcriptions below for anyone who is interested – or you can go and listen to the podcast (episode 'Largest ever COVID safety study' of the BBC World Service's Science in Action).
Space, as Douglas Adams famously noted, is big. And it is not easy for humans to fully appreciate the scales involved – even of say, the distance to the moon, or the mass of Jupiter, let alone beyond 'our' solar system, and even 'our' galaxy. Perhaps that is why public communication of space science is often so rich with metaphor and other comparisons?
When is a star no longer a star (or, does it become a different star?)
One of the issues raised by both items is what we mean by a star. When we see the night sky there are myriad visible sources of light, and these were traditionally all called stars. Telescopes revealed a good many more, and radio telescopes other sources that could not detected visually. We usually think of the planets as being something other than stars, but even that is somewhat arbitrary – the planets have also been seen as a subset of the stars – the planetary or wandering stars, as opposed to the 'fixed' stars.
At one time it was commonly thought the fixed stars were actually fixed into some kind of crystalline sphere. We now know they are not fixed at all, as the whole universe is populated with objects influenced by gravity and in motion. But on the scale of a human lifetime, the fixed stars tend to appear pretty stationary in relation to one another, because of the vast distances involved – even if they are actually moving rather fast in human terms.
Wikipedia (a generally, but not always, reliable source) suggests "a star is a luminous spheroid of plasma held together by self-gravity" – so by that definition the planets no longer count as stars. What about Supernova 1987A (SN 1987A) or quasar J0529-4351?
"This image, taken with Hubble's Wide Field and Planetary Camera 2in 1995, shows the orange-red rings surrounding Supernova 1987A in the Large Magellanic Cloud. The glowing debris of the supernova explosion, which occurred in February 1987, is at the centre of the inner ring. The small white square indicates the location of the STIS aperture used for the new far-ultraviolet observation. [George Sonneborn (Goddard Space Flight Center), Jason Pun (NOAO), the STIS Instrument Definition Team, and NASA/ESA]" [Perhaps the supernova explosion did not actually occur in February 1987]
Supernova 1987A is so-called because it was the first supernova detected in 1987 (and I am old enough to remember the news of this at the time). Stars remain in a more-or-less stable state (that is, their size, temperature, mass are changing, but, in proportional terms, only very, very slowly2) for many millions of years because of a balance of forces – the extremely high pressures at the centre work against the tendency of gravity to bring all the matter closer together. (Imagine a football supported by a constant jet of water fired vertically upwards.) The high pressures inside a star relate to a very high temperature, and that temperature is maintained despite the hot star radiating (infra-red, visible, ultraviolet…) into space 3 because of the heating effect of the nuclear reactions. There can be a sequence of nuclear fusion reactions that occur under different conditions, but the starting point and longest-lasting phase involves hydrogen being fused into helium.
The key point is that when the reactants ('fuel') for one process have all (or nearly all) been reacted, then a subsequent reaction (fusing the product of a previous phase) becomes more dominant. Each specific reaction releases a particular amount of energy at a particular rate (just as with different exothermic chemical reactions), so the star's equilibrium has to shift as the rate of energy production changes the conditions near the centre. Just as you cannot run a petrol engine on diesel without making some adjustments, the characteristics of the star change with shifts along the sequence of nuclear reactions at its core.
These changes can be quite dramatic. It is thought that in the future the Earth's Sun will expand to be as large as the Earth's orbit – but that is in the distant future: not for billions of years yet.
Going nova
Massive stars can reach a point when the rate of energy conversion drops so suddenly (on a stellar scale) that there is a kind of collapse, followed by a kind of explosive recoil, that ejects much material out into space, whilst leaving a core of condensed nuclear matter – a neutron star. For even more massive stars, not even nuclear material is stable, as there is sufficient gravity to even collapse nuclear matter, and a black hole forms.
It was such an explosion that was bright enough to be seen as a 'nova' (new star) from Earth. Astronomers have since been waiting to find evidence of what was left behind at the location of the explosion – a neutron star, or a black hole. But of course, although we use the term 'nova', it was not actually a new star, just a star that was so far away, indeed in another galaxy, that it was not noticeable – until it exploded.
Dr. Olivia Jones (from the UK Astronomy Technology Centre at The Royal Observatory, Edinburgh) explained that neutron stars form from
"…really massive stars like Supernova 1987A or what it was beforehand, about 20 times the mass of a Sun…
So, what was SN 1987A before it went supernova? It was already a star – moreover, astronomers observing the Supernova were studying
…how it evolves in real time, which in astronomy terms is extremely rare, just tracing the evolution of the death of a star…
So, it was a star; and it died, or is dying. (This is a kind of metaphor, but one that has become adopted into common usage – this way of astronomers talking of stars as having births, lives, careers, deaths, has been discussed here before: 'The passing of stars: Birth, death, and afterlife in the universe.') What once was the star, is now (i) a core located where the star was – and (ii) a vast amount of ejected material now "about 20 light years across" – so spread over a much larger volume than our entire solar system. The core is now a "neutron star [which] will start to cool down, gradually and gradually and fade away".
So, SN 1987A was less a star, than an event: the collapse of a star and its immediate aftermath. The neutron star at is core is only part of what is left from that event (perhaps like a skeleton left by a deceased animal?) Moreover, if we accept Wikipedia's definition then the neutron star is not actually a star at all, as instead of being plasma (ionised gas – 'a phase of matter produced when material is too hot to exist as, what to us seems, 'normal' gas) it comprises of material that is so condensed that it does not even contain normal atoms, just in effect a vast number of atomic nuclei fused into one single object – a star-scale atomic nucleus. So, one could say that SN 1987A was no so much a star, as the trace evidence of a star that no longer existed.
And SN 1987A is not alone in presenting identity problems to astronomers. J0529-4351 is now recognised as being possibly the brightest object in the sky (that is, if we viewed them all from the same distance to give a fair comparison) but until recently it was considered a fairly unimpressive star. As doctoral researcher Samuel Lai (Research School of Astronomy and Astrophysics, Australian National University) pointed out,
this one was mis-characterised as a star, I mean it just looks like one fairly insignificant point, just like all the other ones, right, and so we never picked it up as quasar before
But now it is recognised to only appear insignificant because it is so far away – and it is not just another star. It has been 'promoted' to quasar status. That does not mean the star has changed – only our understanding of it.
But is it a star at all? The term quasar means 'quasi–stellar object', that is something that appears much like a star. But, if J0529-435 is a quasar, then it consists of a black hole, into which material is being attracted by gravity in a process that is so energetic that the material being accreted is heated and radiates an enormous amount of energy before it slips from view over the black hole's event horizon. That material is not a luminous spheroid of plasma held together by self-gravity either.
This video from the European Southern Observatory (ESO) gives an impression of just how far away (and so how difficult to detect) the brightest object in the galaxy actually is.
These 'ontological' questions (how we classify objects of different kinds) interest me, but for those who think this kind of issue is a bit esoteric, there was a great deal more to think about in these item.
"A long time ago, in a galaxy far, far away"
For one thing, it was not, as presenter Roland Pease suggested, strictly the 37th anniversary of the SN 1987A – at least not in the sense that the precursor star went supernovae 37 years ago. SN 1987A is about 170 000 light years away. The event, the explosion, actually occurred something like 170 000 years before it could be detected here. So, saying it is the 37th anniversary (rather than, perhaps, the 170 037th anniversary4) is a very anthropocentric, or, at least, geocentric take on things.
Then again, listeners are told that the supernova was in "the Large Magellanic Cloud just outside the Milky Way galaxy" – this is a reasonable description for someone taking an overview of the galaxies, but there is probably something like 90,000 light-years between what can be considered the edges of our Milky Way galaxy and this 'close by' one. So, this is a bit like suggesting Birmingham is 'just outside' London – an evaluation which might make more sense to someone travelling from Wallaroo rather than someone from Wolverhampton.
It is all a matter of scale. Given that the light from J0529-4351 takes about twelve billion years to reach us, ninety thousand light years is indeed, by comparison, just outside our own galaxy.
But the numbers here are simply staggering. Imagine something the size of a neutron star (whether we think it really is a star or not) that listeners were informed is "rotating…around 700 times a second". I do not think we can actually imagine that (rather than conceptualise it) even for an object the size of a pin – because our senses have not evolved to engage with something spinning that fast. Similarly, material moving around a black hole at tens of thousands of kilometres per second is also beyond what is ready visualisation. Again, we may understand, conceptually, that "the neutron star is over a million degrees Celsius" but this is just another very big number way that is outside any direct human experience.
Comparisons of scale
Thus the use of analogies and other comparisons to get across something of the immense magnitudes involved:
"If you think of our Sun as a tennis ball in size, the star that formed [SN] 87A was about as big as the London Eye."
"A teaspoon of this material, of a neutron star, weighs about as much as Everest"
the black home at the centre of the quasar acquires an entire Sun worth of mass every single day
the black hole at the centre of the quasar acquires the equivalent of about four earths, every single second
the quasar is about five hundred trillion times brighter than the Sun, or equivalent to about five hundred trillion suns
Often in explaining science, everyday objects (fridges, buses – see 'Quotidian comparisons') are used for comparisons of size or mass – but here we have to shift up to a mountain. The references to 'every single day' and 'every single second' include redundancy: that is, no meaning is lost by just saying 'every day' and 'every second' but the inclusion of 'single' acts a kind of rhetorical decoration giving greater emphasis.
Figurative language
Formal scientific reports are expected to be technical, and the figurative language common in most everyday discourse is, generally, avoided – but communication of science in teaching and to the public in journalism often uses devices such as metaphor and simile to make description and explanations seem more familiar, and encourage engagement.
Of course, it is sometimes a matter of opinion whether a term is being used figuratively (as we each have our own personal nuances for the meanings of words). Would we really expect to see a 'signature' of a pulsar? Not if we mean the term literally, a sign made by had to confirm identify, but like 'fingerprint' the term is something of a dead metaphor in that we now readily expect to find so-called 'signatures' and 'fingerprints' in spectra and D.N.A. samples and many other contexts that have no direct hand involvement.
Perhaps, more tellingly, language may seem so fitting that it is not perceived as figurative. To describe a supernova as an 'evolving fireball' seems very apt, although I would pedantically argue that this is strictly a metaphor as there is no fire in the usual chemical sense. Here are some other examples I noticed:
"we have been searching for that Holy Grail: has a neutron star formed or has a black hole been left behind"
"the quasar is not located in some kind of galactic desert"
there is a "storm, round the black hole"
"the galaxies are funnelling their material into their supermassive black hole"
"extraordinarily hot nuclear ember"
"a dense dead spinning cinder"
"the ultimate toaster"
Clearly no astronomer expects to find the Holy Grail in a distant galaxy in another part of the Universe (and, indeed, I recently read it is in a Museum in Ireland), but clearly this is a common idiom to mean something being widely and enthusiastically sought.5
A quasar does exist in a galactic desert, at least if we take 'desert' literately as it is clearly much too hot for any rain to fall there, but the figurative meaning is clear enough. The gravitational field of the black hole causes material to fall into it – so although the location, at the centre of a galaxy (not a coincidence, of course), means there is much material around, I was not sure how the galaxy was actively 'funnelling' material. This seems a bit light suggesting spilt tea is being actively thrown to the floor by the cup.
A hot ember or cinder may be left by a fire that has burned out, and one at over a million degrees Celsius might indeed 'toast' anything that was in its vicinity. So, J0529-4351 may indeed be the ultimate toaster, but not in the sense that it is a desirable addition to elite wedding lists.
Anthropomorphism
Anthropomorphism is a particular kind of metaphor that describes non-human entities as if they had the motivations, experiences, drives, etc., of people. The references to dying stars at least suggest animism (that the stars are in some sense alive – something that was once commonly believed 6), but there are other examples (that something is 'lurking' in the supernova remnant) that seem to discuss stellar entities as if they are deliberate agents like us. In particular, a black hole acquiring matter (purely due to its intense gravitational field) was described as feeding:
quasars are basically supermassive black holes just swallowing up all the stars and rubbish around
a quasar is feeding from the accretion disc
a monstrous black hole gobbling up anything within reach
just sat [sic] there, gobbling up everything around it
it has to have been feeding for a very, very long time
it will eat about four of those earths, every single second
in a particularly nutritious galaxy
a quasar that has been declared the hungriest object in the universe
The notion of a black hole feeding on surrounding material seems apt (perhaps, again, because the metaphor is widely used, and so familiar). But there seems a lot more 'negative analogy' than 'positive analogy: that is the ways in which (i) a black hole acquires matter, and (ii) an organism feeds, surely have more points of difference than similarity?
For advanced animals like mammals, birds, fish, snails and the like, feeding is a complex behaviour that usually involves active searching for suitable food, whereas the black hole does not need to go anywhere.
The animal has specialist mouth-parts and a digestive system that allows it to break apart foodstuff. The black-hole just tears all materials apart indiscriminately:"it's just getting chopped up, heated up, shredded".
The organism processes the foodstuff to release specific materials (catabolism) and then processes these is very specific ways to support is highly complex structure and functioning, including the building up of more complex materials (anabolism). The black hole is just a sink for stuff.
The organism takes in foodstuffs to maintain equilibrium, and sometimes to grow in very specific, highly organised ways. The black hole just gets more massive.
A black hole surely has more in keeping with an avalanche or the collapse a tall building than feeding?
One person's garbage…?
Another feature of the discourse that I found intriguing was the relative values implicitly assigned to different material found in distant space. There is a sense with SN 1987A that, after the explosion, the neutron star in some sense deserves to be considered the real remnant of the star, whilst the other material has somehow lost status by being ejected and dispersed. Perhaps that makes sense given that the neutron star remains a coherent body, and is presumably (if the explosion was symmetrical) located much where the former star was.
But I wonder if calling the ejected material – which is what comprises the basis of "an absolutely stunning supernova [which is] beautiful" – as 'debris' and 'outer debris"? Why is this material seen as the rubbish – could we not instead see the neutron star as the debris being the inert residue left behind when the rest of the star explored in a magnificent display? (I am not suggesting either should be considered 'debris', just playing Devil's advocate.)
Perhaps the reference to being able to "isolate the core where the explosion was from the rest of the debris" suggests all that is left is debris of a star, which seems fairer; but the whole history of the universe, as we understand it, involves sequences of matter changing forms quite drastically, and why should we value one or some of these successive phases as being the real product of cosmic evolution (stars?) and other phases as just rubbish? This is certainly suggested by the reference to "supermassive black holes in the middle of a galaxy … swallowing up all the stars and rubbish".
Let's hear it for the little guys
Roland Pease's analogy to "the muck at the bottom of your sinkgoing down into the blender" might also suggest a tendency to view some astronomical structures and phenomenon as intrinsically higher status (the blender/black hole) than others (clouds of dust, or gas or plasma – the muck). Of course, I am sympathetic to the quest to better understand "these guys"(intense quasars already formed early in the universe), but as objectively minded scientists we should be looking out for the little guys (and gals) as well.
Appendix A: "the star hidden in the heart of [the] only supernova visible from Earth"
"If you are listening to this live on Thursday, then you're listening to the 37th anniversary of the supernova 1987A, the best view astronomers have had of an exploding star in centuries, certainly during the modern telescope era. So much astrophysics to be learned.
All the indications were, back then, that amidst all the flash and glory, the dying star should have given birth to a neutron star, a dense dead spinning cinder, that would be emitting radio pulses. So, we waited, and waited…and waited, and still there's no pulsing radio signal.
But images collected by the James Webb telescope in its first weeks of operation, peering deep into the ejecta thrown out by the explosion suggest there is something powerful lurking beneath. Olivia Jones is a James Webb Space Telescope Fellow at Edinburgh University and she helped in the analysis."
"87A is an absolutely stunning supernova , it's beautiful, and the fact that you could see it when it first exploded with the naked eye is unprecedented for such an object in another galaxy like this.
We have been able to see how it evolves in real time, which in astronomy terms is extremely rare, just tracing the evolution of the death of a star. It's very exciting."
"I mean the main point is the bit which we see when the star initially explodes , we see all the hot stuff which is being thrown out into space, and then you've got this sort of evolving fireball which has been easiest to see so far."
"Yes, what see initially is the actual explosion of the star itself right in the centre. What happens now is then we had a period of ten years when you couldn't actually see very much in the centre. You needed these new telescopes like Webb and JWST to see the mechanics of the explosion and then, key to this is what was left behind, and we have been searching for that Holy Grail: has a neutron star formed or has a black hole been left behind at the centre of this explosion. And we've not seen anything for a very long time."
"And this neutron star, so this is the bit where the middle of the original star which at the ends of its life is mostly made of iron, just gets sort of crushed under it's own weight and under the force of the explosion to turn itself entirely into this sort of ball of neutron matter."
"Yeah, it's the very, very core of the star. So the star like the Sun, right in the centre is a very dense core, but really massive stars like Supernova 1987A or what it was beforehand, about 20 times the mass of a Sun.
If you think of our Sun as a tennis ball in size, the star that formed 87A was about as big as the London Eye. So it's a very massive star. The pressure and density right in the centre of that star is phenomenal. So, it creates this really, really, compact core. A teaspoon of this material, of a neutron star, weighs about as much as Everest. So, it's a very, a very dense, very heavy, core that is left behind."
"These were the things which were first detected in the 1960s, because they have magnetic fields and they rotate, they spin very fast and they cause radio pulsations and they're called pulsars. so When the supernova first went off I know lots of radio astronomers were hoping to see those radio pulsations from the middle of this supernova remnant."
"Yes. So, we know really massive stars will form a black hole in the centre, 30, 40, 50 solar masses will form a black hole when it dies. Something around 20 solar masses you'd expect to form a neutron star, and so you'd expect to see these signatures, like you said, in the radiowaves or in optical light of this really fastly rotating – by fastly rotating it can be around 700 times a second – but you would expect to see that signature or some detection of that. But even with all these telescopes – with the radio telescopes, X-ray observatories, Hubble – we've not seen that signature, before and so we are wondering, has a black hole been formed? We've seen neutrinos, so we thought the neutron star had formed, but we've not had that evidence before now."
"So, as I understand it, what your research is doing is showing that there's some unexplained source of heat in the middle of the debris that's been thrown out, and that's what your associating which what ought to be a neutron star in the middle, is that roughly speaking the idea?"
"So, the wonderful thing thing about the Webb telescope, you can see at high resolution both the ring, the outer debris of the star, and right at the very centre where the explosion was, but it's not just images we take, so it's not just taking a photograph, we also have this fantastic instrument or two instruments, called spectrographs, which can break down light into their individual elements, so very small wavelengths of light, it's like if you want to see the blue wavelength or the red wavelength, but in very narrow bands."
"And people may have done this at school when they threw some salt into a Bunsen burner and saw the colours, it's that kind of analysis?"
"Yes. And so what we see where the star was and where it exploded was argon and sulphur, and we know that these needed an awful lot of energy, to create these, and I mean a lot, of energy. And the only thing that can be doings this, we compared to many different kinds of scenarios, is a neutron star."
"So this is basically an extraordinarily hot nuclear ember, that's sort of sitting in the middle."
"Yes, right in the middle and you can see this, cause Supernova 1987A is about 20 light years across, in total, and we can isolate the core where the explosion was from the rest of the debris in this nearby galaxy, which I think is fantastic."
"Do you know how hot the surface of this star is and is it just sort of the intense heat, X-ray heat I imagine, that's coming off, that's causing all this radiation that you're seeing."
"I hope you are ready for a very big number."
"Go on."
"The neutron star is over a million degrees Celsius."
"And so, that's just radiating heat, is it, from, I mean this is like the ultimate toaster?"
"Yes, so what eventually will happen over the lifetime of the universe is this neutron star will start to cool down, gradually and gradually and fade away. But that'll be many, many billions of years from now.
What we currently have now is one of the hottest things you can imagine, in a very small location, heating up all its surroundings. I would not want to be anywhere nearby there."
Roland Pease interviewingDr. Olivia Jones (Edinburgh University)
Appendix B: "possibly the brightest object in our universe"
"Now 1987A was, briefly, very bright. Southern hemisphere astronomy enthusiasts could easily spot it in the Large Magellanic Cloud just outside [sic] the Milky Way galaxy. But it was nothing like as bright as JO529-4351 [J0529-4351], try memorising that, its a quasar twelve or so billion light years away that has been declared the brightest object in the universe and the hungriest. At first sight, it's an anonymous, unremarkable spot of light of trillions on [sic] an astronomical photo. But, if you are an astronomer who knows how to interpret the light, as Samual Lai does, you will find this is a monstrous black hole gobbling up anything within reach. Close to the edge of all that we can see."
"So this quasar is a record breaking ultra-luminous object, in fact it is the most luminous object that we know of in the universe. Its light has travelled twelve billion years to reach us, so it's incredibly far object, but it's so intrinsically luminous that it appears bright in the sky."
"And as I understand it, you identified this as being a very distant and bright object pretty recently though you have gone back through the catalogues and its was this insignificant speck for quite a long time."
"Yes, indeed. In fact we were working on a survey of bright quasars, so we looked at about 80% of the sky using large data sets from space satellites. Throughout our large data sets, this one was mis-characterised as a star, I mean it just looks like one fairly insignificant point, just like all the other ones, right, and so we never picked it up as quasar before. Nowadays we are in the era of extremely astronomical, pardon the pun, data sets where in order to really filter thorough them we have these classification algorithms that we use. So, we have the computer, look at the data set, and try to learn what we are looking at, and pick out between stars and quasars."
"Now, is it also interesting, they were discovered about sixty years ago, the first quasars. These are basically supermassive black holes in the middle of a galaxy that's just swallowing up all the stars and rubbish just around it, and that's the bit that for you is quite interesting in this instance?"
"Yes, exactly, and the quasar owes its luminosity to the rate at which it is feeding from this accretion disc, this material that's swirling around, like a storm, with the black hole being the eye of the storm."
"I mean, I think of it as being a bit like the muck at the bottom of your sink going down into the blender at the bottom, it's just getting chopped up, heated up, shredded, and, I mean what sort of temperatures are you talking about? What, You know, what kind of energy are you talking about being produced in this system?"
"Yes ,so the temperatures in the accretion disc easily go up to tens of thousands of degrees, but talking about brightness, the other way that we like to measure this is in terms of the luminosity of the Sun, which gives you are sense of scale. So, this quasar is about five hundred trillion times brighter than the Sun, or equivalent to about five hundred trillion suns."
"And it's been doing this sort of constantly, or for really for a long time, I mean it's just sat there, gobbling up everything around it?"
"Yeah, I mean the mass of the quasar is about 17 billion solar masses, so in order to reach that mass it has to have been feeding for a very, very long time. We work it out to be about one solar mass per day, so that's an entire Sun worth of mass every single day. Or if you like to translate that to more human terms, if you take the Earth and everybody that's on it, and you add up all of that mass together, it will eat about four of those earths, every single second."
"I suppose what I find gob-smacking about this is (a) the forces, the gravitational forces presumably involved in sweeping up that amount of material, but (b) it must be an incredibly busy place – it can't be doing this in some kind of galactic desert."
"Yes, indeed, I mean these quasars, these super-massive black holes are parts of their galaxies, right, they're always in the nuclear regions of their host galaxies, and in some way the galaxies are funnelling their material into their supermassive black hole."
"But this one must be presumably a particularly, I don't know, nutritious galaxy, I guess. It is so far away, you can't make out those kinds of details."
"We can however make out that some of that material moving around, inside the storm, round the black hole, their dynamics are such that their velocities reach up to tens of thousands of kilometres per second."
"Why are you looking for then? Is it because you just want to break records – I'm sure it's not. Or is it, that you can see these things a long way away? Is it, it tells you about the history of galaxies?"
"I mean we can learn a lot about the universe's evolution by looking at the light from the quasars. And in fact, the quasar light it tells you a lot about not just the environment that the quasar resides in, but also in anything the quasar light passes through. So, you can think of this, lights from the quasar, as a very distant beacon that illuminates information about everything and anything in between us and the quasar."
"I mean the thing that I find striking is, if I've read the numbers right, this thing is so far away that the universe was about a billion years old. I mean I suppose what I'm wondering is how did a black hole becomes so massive so early in the universe?"
"Ah see, I love this question because you are reaching to the frontier of our current understanding, this is science going as we speak. We are running into an issue now that some of these black holes are so massive that there's not enough time in the universe, at the time that we observe them to be at, in order for them to have grown to such masses as they are seen to be. We have various hypotheses for how these things have formed, but at the moment we observe it in its current state, and we have to work backwards and look into the even older universe to try to figure out how these guys came to be."
Roland Pease interviewingDr. Samuel Lai (Australian National University)
Notes
1 Having been a science teacher, I find myself listening to, or reading, science items in the media at two levels
I am interested in the science itself (of course)
I am also intrigued by how the science is presented for the audience
So, I find myself paying attention to simplifications, and metaphors, and other features of the way the science is communicated.
Teachers will be familiar with this. Curriculum selects some parts of science and omits other parts (and there is always a debate to be had about wither the right choices are made about what to include, and what to omit). However, it is rare for the selected science itself to be presented in 'raw' form in education. The primary science literature is written by specialists for other specialists, and to a large extent by researchers for other researchers in the same field – and is generally totally unsuitable for a general audience.
Curriculum science is therefore an especially designed representation of the science intended to be accessible to learners at a particular stage in their education. Acids for twelve years olds or natural selection for fifteen year olds cannot be as complex, nuanced and subtle as the current state of the topic as presented in the primary literature. (And not just because of the level f presentation suitable for learners, but also because in any live field, the work at the cutting edge will by definition be inconsistent across studies as this is just where the experts are still trying to make the best sense of the available evidence.)
The teacher then designs presentations and sequences of learning activities to engage particular classes of learners, for often teaching models and analogies and the like are needed as stepping stones, or temporary supports, even to master the simplified curriculum models set out as target knowledge. Class teaching is challenging as every learner arrives with a unique nexus of background knowledge, alternative conceptions, relevant experiences, interests, vocabulary, and so forth. Every class is a mixed ability class – to some extent. The teacher has to differentiate within a basic class plan to try and support everyone.
I often think about this when I listen to or read science journalism or popular science books. At least the teacher usually knows that all the students are roughly the same age, and have followed more-or-less the same curriculum up to that point. Science communicators working with the public know very little about their audience. Presumably they are interested enough in the topic or science more generally to be engaging with the work: but likely of a very diverse age, educational level, background knowledge: the keen ten year old to the post-doctoral researcher; the retired engineer to the autistic child with an intense fascination in every detail of dinosaurs…
I often find myself questioning some of the simplifications and comparisons used on science reports in the media – but I do not underestimate the challenge of reporting on the latest findings in some specialist area of science in an 'academically honest' way (to borrow a term from Jerome Bruner) in a three minute radio slot or 500 words in a magazine. So, in that spirit, I was fascinated by the way in which the latest research into Supernova 1987A and J0529-4351 was communicated, at least as much as the science itself.
2 That is, the flux of material emitted by our Sun, for example, is quite significant in human terms, but is minute compared to its total mass. Our sun has cooled considerably in the past few billions of years, but that's long time for it to change! (The Earth's atmosphere has also changed over the same time scale, which has compensated.)
3 Some very basic physics (Isaac Newton's law of cooling) tells us that objects radiate energy at a rate according to their temperature. Stars are (very large and) very hot so radiate energy at a high rate. An object will also be absorbing radiation – but the 'bath' of radiation it experiences depends on the temperature of its surroundings. A hot cup of coffee will cool as it is radiating faster than it is absorbing energy, because it is hotter than its surroundings. Eventually it will be as cool as the surroundings and will reach a dynamic equilibrium where it radiates and absorbs at the same rate. (Take the cooled cup of coffee into the sauna and it will actually get warmer. But do check health and safety rules first to see if this is allowed.)
The reference to how
"what eventually will happen over the lifetime of the universe is this neutron star will start to cool down, gradually and gradually and fade away. But that'll be many, many billions of years from now"
should be understood to mean that the cooling process STARTED as soon as there was no internal source of heating (form nuclear reactions or gravitational collapse) to maintain the high temperature; although the process will CONTINUE over a long period.
4 That weak attempt at humour is a variant on the story of the museum visitors who asked the attendant how old some ancient artefacts were. Surprised at the precision of the reply of "20 012 " years, they asked how the artefacts could be dated so precisely. "Well", the attended explained, "I was told they were twenty thousand years old when I started, and I've worked here for twelve years."
Many physics teachers will not find this funny at all, as it is not at all unusual for parallel mistakes to be made by students. (And not just students: a popular science book suggested that material in meteors can be heated in the atmosphere to temperatures of up to – a rather precise – 36 032 degrees! (See 'conceptions of precision').
5 The Holy Grail being the cup that Jesus is supposed to have used at the last supper to share wine with his disciples before he was arrested and crucified. Legend suggests it was also used to collect some of his blood after his execution – and that it was later brought to England (of all places) by Joseph of Arimathea, and taken to Glastonbury. The Knights of King Arthur's Round Table quested to find the Grail. It was seen as a kind of ultimate Holy Relic.
6 Greek and Roman cultures associated the planets (which for them included the Sun and Moon) with specific Gods. Many constellations were said to be living beings that have been placed in the heavens after time on earth. Personification of these bodies by referring to them in gendered ways ('he', 'she') still sometimes occurs.
In his cosmogony, Plato had the stars given a kind of soul. Whereas Aristlotle's notion of soul can be understood as being something that emerges from the complexity of organisation (in organisms), Plato did imply something more supernatural.
A new study reports a creative approach to modelling the atom motivated by a love story
Keith S. Taber
Perhaps it would be better not to introduce an orbital model until we feel learners are ready to appreciate the quantum jump from concentric orbits to fuzzy, overlapping, infinitely-extended patterns of electronic probability, and the associated complex patterns of energy levels they generate.
"Grade: B-. Comment: Your model of the heteronuclear molecule of Romeo-Juliet was creative and aesthetically pleasing, but it was inconsistent because you used rope to stand for the covalent bond when you are representing electrons with apples." (Image by Николай Оберемченко from Pixabay)
The science curriculum contains a good deal of abstract material that is both challenging, and – sadly – not always found intrinsically interesting, to many learners. The teacher has to find what can 'make the unfamiliar familiar', something I have written quite a lot about on this site.
One such abstract topic is the structure of 'the' atom1 – an area where learners will likely come across multiple models and diverse representations, and where what is being modelled and represented (as a quanticle – a quantum object) simply cannot be adequately represented concretely. Given that, it is hardly surprising that often even keen and capable learners show alternative conceptions in this topic (Taber, 2002 [Download paper]).
I was therefore intrigued by a recent research paper that described an approach to progressing learners' ideas about atomic structure by asking them to engage with a story. Narrative is a recognised way of helping make the unfamiliar familiar, and here a story was referenced that is familiar to many people: that of Shakespeare's 'star-crossed lovers': Romeo and Juliet.
So, in the storyline, electrons were named after characters from the tragic tale. It is common to relate abstract chemical ideas to social relations (chemistry uses such metaphors as 'sharing electrons', 'nucleus loving' species, reagent species that 'attack' other molecules, and substances that 'compete') – but this does risk the anthropomorphism (that is, treating non-human entities as if they have human qualities) actually confusing learners.
That is, molecules and ions, and nuclei and electrons are not like people, and do not think or have desires, and so they do not act from motivations such as love or hate or jealousy…
Perhaps this seems SO OBVIOUS that only the weakest student could possibly get confused and think otherwise?
But I know from my own research (e.g., Taber & Watts, 1996 [download paper]) that actually even studious, intelligent learners can come to habitually use anthropomorphic language without noticing that they are explaining chemistry in terms that would only make sense if atoms and molecules and ions and electrons did have preferences, and could think for themselves, and did actaccordingly!
Atoms can not care about anything – so they do not care about how many electrons they have, and they never deliberately do anything in order to obtain full shells or octets (as they cannot act under their own volition, of course). But many generally successful, hard-working, intelligent, learners in chemistry classes all over the world seem to think otherwise (Taber, 1998 [Download paper]).
Likewise, electrons do not care if they are in an atom or not, or whether they are spin-paired or not (and if so, which other, indistinguishable, electron they are paired with), or which energy level of a system they populate.
The authors of the recent paper (which is open access, so freely available for anyone who wishes to download/read it) claim that students found the story-related activity engaging (which certainly seems likely) and that it helped address some misconceptions about atomic structure. They note that:
"Students do not clearly understand the concept of an orbital" (Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024)
This is a topic that has long interested me so I took a look at the activity the researchers had devised. The learners were
"10th-grade classes, with the participants' average age being between 15 and 16, attending a technical computer science high school 1…[who] had already studied the atomic model in their chemistry classes during the first half of the year."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
I have taught a basic (planetary) model of atomic structure to students at this age, and also more advanced models to 16-19 year old learners (on A level courses), so I was keen to read about the activity. The authors did not include an explicit statement of the curriculum content which was being treated as target knowledge, although they did include a discussion of their rationale for the story, as well as comments on student work, from which some features could be deduced or inferred. (I would have found it useful to have read an explicit statement of just what the learners were expected to know – what the 'correct' model was meant to be – at the outset of the paper.)
I approached the paper thinking it was ambitious to teach an orbital model of the atom to students of this age. My reading of the story (reproduced below) reinforced that initial impression (I admit, I was challenged in places!) – although the authors certainly felt the students in their research coped well with the challenge.
Although I felt I struggled interpreting some features of the narrative,
A student with a specific learning disorder (SLD), mentioned, "The connection of a fairly complicated topic with such a simple story"
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
It is important to note that the teaching scheme adopted a dialogic approach, where class discussions were included at two points after the students had worked in groups on parts of the activity. The activity was also conceptualised as being part of an enquiry-based learning cycle. So, the material below should be read accordingly, as it does not reflect this wider classroom context.
The story is broken into four parts, each leading to a task for the learners (working in groups) to engage in.
Prologue
"Romeo is a bold and dynamic electron found in an atom with seven energy levels. He is at the 4s energy level, together with the faithful Mercutio, his companion on raids. Always upside down compared to him, but then there is no place for two equal electrons in their crew. The two are part of the Montague family, known for being particularly lively.
Juliet is an electron in 2s, she is more tied to her nucleus and in fact she is a Capulet, a rival family to that of the Montagues and decidedly more calm. Juliet is always accompanied by her nurse; they too are turned upside down with respect to each other.
There is a grand ball to which everyone is invited, and, to better organize their arrangement, there is a need to schematize their position."
[Instructions to learners: "Discuss with your classmates what should be the design of the atom where the two families «are» and build a model"]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Chapter 1 – part 1
"At one point during the dance, Romeo notices Juliet in her orbital, and, even if he occasionally gets close to her, he is unable to stay there permanently: quivering with love, he asks who knows her and what her tastes are in terms of radiations (electrons are well known to be romantics). He discovers that Juliet is obsessed with color harmony and that the color she prefers is purple "486 nm". To get noticed he wants to perform his famous photon–spectroscopic serenade and jump to emit a purple trail.
[Instructions to learners: "Discuss with your teammates to help Romeo understand how far he will have to jump and whether or not he would have gotten closer to Juliet in this way."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Chapter 1 – part 2
"The two are deeply in love and would like to spend the rest of their days together. But Juliet's family hinders them, crying scandal: a Montague cannot be so tied to the nucleus! What to do? The nurse offers Romeo the chance to take her place, but, for her, this would mean losing her place next to Juliet. Romeo and Juliet, very hesitant, then decide to move towards the orbitals occupied by the Montagues. But how to get up there?
While the couple is tormented by this problem, an enlightened friar, Lory, arrives to their rescue with two THz 457s, offering to give them a lift. Despite this help, Romeo and Juliet are unable to reach the Montague orbital, so they loudly invoke another friar, Enzo, asking for new help.
[Instructions to learners: Discuss with your teammates to understand how far they will jump thanks to the first photons and which photons Fra Enzo will have to carry for the two lovers to reach the Montague orbital."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Chapter 2 and epilogue
"Juliet's escape has thrown the entire atomic balance into crisis, forcing some Montagues to change levels in order to maintain overall stability. Then, when the couple comes to the Montagues, they cry out for revenge, and the couple is then forced to flee again.
The Montagues set out in search of Romeo and Juliet but fail because it is not possible to reconstruct the trajectory followed by the two lovers.
The story unfortunately ends in tragedy: the two do manage to free themselves from the influence of their families, but they still understand that they cannot be together. Now condemned to separation, the two lovers decide to draw up a schema of the place (the atom) where they met to remember it forever.
[Instructions to learners: "Discuss with your teammates why this trajectory cannot be reconstructed. End the story with a tragic ending, explaining the reasons for the separation sentence.
EPILOGUE Construct with your teammates a possible model of the scheme realized by Romeo and Juliet."]
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Interpreting the narrative
Reading the account I had a very mixed response. I am very keen on approaches that use the familiar everyday as ways into teaching complex, abstract ideas; but subject to two provisos:
these everyday analogies are interim supports ('scaffolds'), to be withdraw as soon as they are no longer needed;
teaching needs to focus on the 'negative analogy' (things that do not map across) as well as the 'positive analogy' (the aspects of the comparison that 'work').
The approach here seemed somewhat different. The learners had already been taught a model of the atom earlier in the year, and this activity was intended to be an opportunity to review this prior learning and apply it – and an opportunity for teachers to identify any alternative conceptions elicited by the activity.
Metaphorical meanings?
Romeo and Juliet are not the lovers in the stage play, but electrons. Therefore, in reading the story I identified scientific information (electron Romeo is in a 4s orbital in an atom) and material that seemed to be metaphorical (the electrons Romeo and Mercutio go on 'raids'). I therefore saw the task of reading the story as being in part a decoding of the metaphors that were used.
So, the idea of Romeo and Mercutio being relatively "upside down" was not to be taken literally (electrons do not have ups or downs) but to be a metaphor for spin +1/2 and spin –1/2, often referred to metaphorically as 'spin up' and 'spin down'. Going on raids was more tricky: in some chemical reactions electron pairs are considered to shift during bond formation (or bond breaking, but that would not refer to an atomic species), but 'raid' suggests a temporary excursion.
I could not understand in what sense Mercutio (the electron, not the fictional character) could be said to be faithful. Electrons respond to physical forces, not personal attachments. Perhaps, I was over-thinking this, and not all the narrative elements did map onto the atomic system? Perhaps that was meant to be part of the challenge for the learners?
A fundamental concern with this kind of comparison is that all electrons are inherently identical, and are only distinguished by the accidental features they acquire in a particular system.
A 2s electron is on average closer to the nucleus, and experiences a greater effective core charge (it is not shielded as much from the nucleus as a 4s electron is) – so the 'tie' (bond) to the nucleus can be understood as analogous to the attractive force operating between the electron and nucleus. 2
The reference to being more calm perhaps refers to how the 2s level is at a 'lower' energy so the 'particularly lively' 4s electrons can be more dynamic?
If Romeo and Mercutio, or even Romeo and Juliet, were swapped it could make absolutely no difference and no one could tell. By giving electrons personal identities they seem to be more like us and less like electrons. Electrons cannot be bold or calm. Romeo and Juliet behave differently because they are in different orbitals at different energy levels, not because they are different electrons. Could learners miss this critical point? If Juliet (or Romeo) moved to a different energy level then she (or he) would change 'personality' – but that would undermine the narrative.
I was not sure how the two families related to anything. Within an atom we could class some electrons alike because they are in the same 'shell' (have the same principal quantum number) – so perhaps the two families were in the n=2 and n=4 levels (the L and N shells being their metaphorical 'houses'). I also could not understand where the ball was meant to be held:
were the electrons to be moved to a new set of orbitals (requiring promotion)
were the electrons meant be moved to outside the atom (requiring ionisation), or
was the ball to take place with the electrons in their current orbitals (but for some reason behaving differently than when no dance was taking place?)
The attraction between Romeo and Juliet (the electrons, not the fictional lovers) was difficult to understand. Certainly, if we adopt a model of electrons moving about in different orbitals 3 then they could sometimes be nearer to each other as atomic orbitals interpenetrate – and if so they would influence each other more (due to their charge and spin) at these times: but this would primarily be a repulsion.
Interpenetrating fields of play. If two sports pitches were marked out overlapping on the same ground, then there would be places that were part of both fields of play.
(Consider a school with very limited space for sports pitches. Perhaps they mark up a soccer pitch and a field hockey pitch overlapping. If both soccer and hockey players train at the same time there will be places that are part of both pitches, and players from the two sports can come close together in those areas. {This is just an analogy. The two sports would need to schedule practice at different times to avoid accidents!})
It seemed to me that the learners were being asked to read the account at two levels – some features of the story were metaphors (such as when the lovers left the atom only to find they had separate indeterminate trajectories) when other features seemed to be simply plot devices to provde an engaging narrative. I thought that the students were being asked to work out which bits of the story they should take seriously as corresponding to part of an atomic model, and which just moved the narrative on. I though this might be challenging for the 14-15 year old learners (as I was struggling!)
Orbitals and transitions
Some features of the story seemed potentially likely to encourage alternative conceptions. Juliet's preference for light of wavelength 486 nm risks the association of a spectral line with an electron or an energy level, rather than with a transition.
The specific references to 486 nm and 457 THz radiation seemed to suggest that a quantative model was needed – where an atom would actually show spectral lines reflecting transitions associated with radiation of these specific characteristics.
The rationale
Unlike the students, I had access to some of the resource designers' thinking as the paper included a rationale for the storyline. This acknowledged that
The specific location of the grand ball remains implicit [?], as it is challenging to conceive of electrons dancing outside the metaphorical context of "moving swiftly". However, all the other character details are essential for initiating the story and allowing mathematical and physical problems and situations to emerge."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
This seemed to confirm that the learners were expected to build a quantitative model. This was reiterated later in the rationale
"Through calculations of energy transitions and the resulting orbital distances, students gain insight into the quadratic proportionality that underlies these phenomena [?], prompting a gradual reshaping of their personal notions regarding orbital distances."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
I was not sure what was mant by 'orbital distances', and return to this point below. I was also not sure how quadratic proportionality underlay energy transitions.
This was only one of the points in the paper where I got the impression that in the teaching model adopted, energy levels and orbitals were not only being associated, but at times almost seen as equivalent and interchangeable.
A diagnostic assessment opportunity
The rationale seemed to confirm that the activity was deliberately testing whether students associated spectral lines with energy levels rather than transitons between levels,
"To elucidate the intriguing connection between emission and electron transitions to different energy levels, we introduce a romantic-comedic twist, employing Juliet's passion for color harmony as a plot device. Juliet's preference for the color purple is strategically chosen to align with her energy level, prompting students to contemplate the intriguing relationship between spectroscopy lines and electron energy transitions."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
On the other hand, my suspicion that I had been reading too much into the narrative, and trying too hard to interpret plot twists was ratherundermined by being told,
"Take, for instance, Romeo's desire to gain Juliet's attention and their joint pursuit of a life away from their feuding families. This narrative intricately parallels the fundamental interplay of orbitals within the model, establishing a direct and compelling link between the characters' human drama and the pivotal role of orbitals in the model."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Indeed? I was struggling to map across some of the story, even when (unlike the students) I had access to the rationale:
"At the outset, the consequences of Romeo and Juliet's choices become apparent: the voids within the nucleus [?] are replenished with new electrons [?], ultimately disturbing the equilibrium of the two feuding families. This disruption leads them to share orbits [sic], not fueled by anger but by fate. The Montagues seek revenge, yet they grapple with the inability to reconstruct the electrons' orbitals due to the uncertainty principle."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
A lot of this went over my head.
The uncertainty principle would not interfere with characterising orbitals, only with being able to posit specific electron trajectories. The orbitals do not belong to electrons ("the electrons' orbitals") but are characteristic of an atomic system with its configuration of charges.
A hybrid model?
Perhaps, in part, my confusion was due to my not being clear about what the target knowledge was- exactly which kind of model was it hoped the students would produce?
"After studying the planetary and Bohr atomic models, students cannot easily move beyond them"
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
It seemed clear from the paper that the learners were expected to have moved beyond a model with planetary orbits, to a model with orbitals, and so from the idea of electrons moving on definite trajectories, to being found somewhere within the orbitals. 3
There was historically a range of models of the atom (even 'the Bohr model' was actaully a series of models), and long ago Rosaria Justi and John Gilbert (Justi & Gilbert, 2000) pointed out that often in teaching we end up presenting 'hybrid' models – that is, models which have features drawn from across several of the different scientific models. Did the curriculum these students followed set out such a hybrid model for students to learn? 4
An atom with seven energy levels?
At the start of the story, the students were told "Romeo is …found in an atom with seven energy levels". I am not sure any real atom could only have seven energy levels. My understanding is that any atom has in principle an infinite number of energy levels, but the the spacing of the levels gets successively smaller, so they converge on a limit (which makes ionisation feasible). Even the hydrogen atom has an infinite number of energy levels, but only one is populated with an electron.
So, I wondered if possibly this was meant to be read as "Romeo is …found in an atom with seven populated energy levels"?
A sensible starting point for a student is to assume the atom is initially in its ground state (as under normal circumstances they usually are). If the reference to seven energy levels means populated energy levels, and students are to assume the atom starts in the ground state then presumably learners are meant to assume the atom they need to model is one of the first transition series (i.e., elements with electronic configurations from 1s2 2s2 2p6 3s2 3p6 4s2 3d1 to 1s2 2s2 2p6 3s2 3p6 4s2 3d10: that is an atom from one of the elements scandium to zinc).
However, later there is a reference to electron Romeo wanting to "jump to emit a purple trail". But he needs to jump 'down' (to a lower energy level) both to get closer to Juliet and indeed to "emit a purple trail" (i.e., for Romeo to be promoted, light would need to be absorbed not emitted) – which is only possible if the atom is NOT initially in its ground state, so that there will be an orbital at a lower energy level not fully occupied. That potentially complicates the model to be built.
For one thing, if the atom is not in its ground state, then atoms of elements of lower atomic mass than scandium might be the target atom to be modelled? Indeed, any atom from the element nitrogen (in the highly excited configuration 1s1 2s1 2p1 3s1 3p1 4s1 3d1 ) on to zinc could theoretically have seven occupied energy levels. It did not help that there seemed to be no information on how many electrons were in this atom – four were specified, and we are told unspecified other 'family' members lived there, and two other characters were name-checked without it being explicit if they were also in the atom or just passing (from the local Abbey perhaps – would that be an atom of a noble gas?)
Interorbital distances?
As noted above, the authors refer to how they "delve into the concept of interatomic orbital distances", but this seems an oxymoron.
"From the analysis of the drawings, it emerges that the students' final drawings can be traced back to three different types of atom representation (R):
R1: orbits/orbitals represented at varying distances to convey the concept of energy levels more effectively;
R2: orbits/orbitals represented at correct distances according to the radius;
R3: attempt to depict the concept of orbitals and the correct distances between them."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
The authors refer to how in a figure assigned to category R3, "The distances between the spheres reflect the correct distances according to n2", but this does not strictly relate to an orbital model.
Orbitals do not have edges, so it is not possible to measure how far they are from anything. Strictly, every orbital reaches to infinity (even if the electron density soon gets so rare that it becomes effectively zero). The point is that this is a gradual falling-off and there is no sudden drop that we might think of as an edge.
Commonly orbitals are represented either with
probability contour lines, or
colour or shading showing differnt levels of electron density (i.e., the relative probabilities of an electron in the orbital being 'found' at different regions of the orbital), or
more simply with probability envelopes.
Those envelopes show where, say, 90% or 95% of the electron density is located – which means 10% or 5% of the electron density (that is inside the orbital) lies outside the envelope drawn. So, these lines are to soem degree arbitrary, conventional and do not correspond to anything physical ('real').
One could measure the distance between the centres of two different orbitals, but this would be a trivial issue when the orbitals are in the same atom. (That is, the atomic orbitals are all centred on the nucleus, so the centres have no distance between each other.)
This is different to a planetary type model where electrons are considered to be a certain distance from the nucleus, so the orbits have quantifiable radii. In moving to an orbital model we have to think of fuzzy overlapping volumes of space, and the notion of there being set distances between orbitals just does not work in this model.
Imagine being asked to report the distance between the soccer pitch and the hockey pitch.
And then imagine having that task when there are no marked out edges to the pitches.
The energy levels associated with the orbitals can be considered to have specific values, and so there are definite differences ('distances'?) between the levels in that sense – but these would be energy gaps: analogical 'distances' on an energy scale, not actual distances.
Despite their discussion about orbitals, [for the students' final drawings] all groups drew orbits, representing them as lines depicting the trajectories of electrons
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
But that is not so clear from the diagrams of the models and the students' own comments.
Student 1: "In a circle, we drew lines. But we know that electrons don't follow that precise path; they exist in orbitals, which are regions where electrons are more likely to be found. So, we don't know the precise radius because it's a region. Therefore, in my opinion, since the radius can always vary, you can't use the radius to depict the atomic model; it's more accurate to use energy levels."
…
Teacher: "Here you have drawn the distances increasingly closer. Why?"
Student 2: "Because it represented differences in energy levels."
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Some groups of students seem to have drawn concentric circles representing energy levels rather than orbits or shells or orbitals. Normally, energy level diagrams are not drawn like that, but this seems a perfectly reasonable form of representation providing it is explained.
Spherical orbitals
We also have to bear in mind that only s-orbitals have spherical symmetry. (A 'shell' of orbitals in an atom would be spherically symmetrical only if each orbital was singly or fully occupied. But it was not clear how many electrons were in this atom.)
The first seven energy levels in any atom or ion with more than one electron will be associated with p- and d-orbitals as well as s-orbitals. So, even if orbitals were represented with probability envelopes, and these were treated (incorrectly) as if the edges of the orbitals, then there would be no fixed 'distances' between the edges of any comparisons involving these non-spherical orbitals.
Not all orbitals have spherical geometry (Image by Smiley _p0p from Pixabay)
At this point it is interesting to examine the samples of student models represented in the paper. All of them are drawn with circles. The authors of the paper seemed satisfied with this aspect of the models.
Making sense of 486 nm and the 'THz 457s'
I pointed out above that my reading of the information given about the atom that it seemed the target atom could be from one of a wide range of elements. It seems I got this completely wrong,
We conclude this paper by highlighting a limitation of the story we have designed from a physical point of view. Our story does not fit the real atomic structure. Indeed, we chose to consider a hydrogen atom with multiple electrons because we thought it was easier for the students to manipulate. We are aware of the fact that this may represent a critical point of our story, but in the classes where we experienced the activity it has not created problems, since the students noticed this inconsistency and talked about it with the teacher.
Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024
Now, by definition, a model is never quite like what is modelled – or it ceases to be a model and becomes a perfect replica. But "a hydrogen atom with multiple electrons" is not an atom at all, but an ion. I am not clear why this is "easier to manipulate" than an atom of a different element, as in models of this kind the nucleus is in effect just a minute point charge – so its composition does not complicate the model in any significant way. If that nuclear charge is +7, say, rather than +1, it makes a difference, certainly (to energy levels), but that does not add any further complexity.
Perhaps the authors chose to retain a hydrogen nucleus because they wanted students to use data from hydrogen spectra? (But if so, this was a little naughty.)
The Balmer series
Again, it did not help that I did not know what the target knowledge set out in the curriculum was.4 But, knowing now that hydrogen was the target atom led me to suspect 486 nm and 457 THz radiation linked to lines in the hydrogen spectra – lines in the Balmer series associated with transitions between n=3 and n=2 (656 nm) and n=4 and n=2 (486 nm).
That was all very well, but those transitions referred to the hydogen atom and not to a hydrogen ion. The extra electrons repelling each other in the ion (assuming the ion could be considered stable, which is itself problematic) mean the energy levels (and so the energy gaps; and so the spectral lines) would all be different.
But, if we pretended the ion was stable, and if we pretended that the additional electrons did not change the energy levels (what is what I meant by being somewhat naughty), then the numbers made sense.
A sleight of hand?
Indeed, if we were to adopt the hydrogen atom as the model for our ion, then I sensed I understood why the orbitals were all drawn as circles. In the hydrogen atom, the energy levels are only associated with the principle quantum number. The 2p orbital is at just the same energy level as the 2s orbital. A transition from the N shell to the L shell has the same energy associated with, and so the same frequency of radiation, regardless of whether it involved 2s-4s or 2p-4s or 2s-4p or 2p-4p or 2s-4d or 2p-4d (or indeed 2s-4f or 2p-4f)5. That is a considerable simplification, that would make the task much easier for learners.
So, if we are modelling the hydrogen atomic energy levels, we only need to worry about the principle quantum number as there is one level for each value of n. The student diagrams reproduced in the paper suggested all the students understood the reference to an atom with seven energy levels to mean n (that is the principle quantum number related to 'shell') = 1-7.
But an energy level is not an orbital. The n=2 energy level in a hydrogen atom is associated with 4 orbitals, only one of which has spherical symmetry. The n=3 level is associated with 9 orbitals, only one of which has spherical symmetry.
Moreover, this assumption that all the orbtials in a shall are at the same energy level ('degenerate') only applies to a hydrogenic species (H, He+, Li2+, etc.) – that is, atom-like species with a single electron. The 'atom' (ion) with Romeo and Juliet and Mercutio and the nurse and the rest of the Capulets and Montagues (and possibly some clergy) would not have 2s and 2p orbitals that were degenerate. The presence of interacting electrons (repelling each other, that is, not lusting after each other and "quivering with love") would raze the degeneracy- so the 2s and 2p orbitals would actually be at different energy levels. And so also with 3s and 3p and 3d.
It is not the presence of a hydrogen nucleus which leads to degeneracy between the orbitals within each value of n (each shell), but a system of one nucleus and one electron. So if this 'atom' (ion) had seven energy levels, these would not equate to seven shells of electrons.
The model
So, it looks like the target model was an ion with a hydrogen nucleus, and 7 energy levels occupied by an unspecified number (>4) of electrons, which has the same energy structure and levels as a hydrogen atom, but where each energy level only contained an s orbital.
Models simplify, and in modelling we deliberately leave aside some complexity and nuance. However, we have to balance the gain in simplicity with the loss of authenticity.
A highly charged hydrogen ion could not exist (unless maintained by some very powerful external field)
Atoms have an infinite number of energy levels (but there is no harm in asking learners to ignore most of them for the time being when working on a task)
A hydrogen atom has orbitals of different types (s, p, d…) not all of which are of spherically symmetrical.
The electronic transitions in an ion would not be those found in the related atom, as energy levels of the system depend on the configuration of charges that are interacting. The ion would have many more potential transitions than a single-electron system (such as a hydrogen atom), and these would not have the same energies/frequencies/wavelengths as in the hydrogen atom.
Orbitals do not have edges, and they interpenetrate, so the concept of interatomic orbital distances does not correspond to anything 'realistic' in the orbital model of the atom.
So, the model seems to put aside a lot of the subtlety of the science. But then are these nuanced ideas suitable for treatment with most 15-16 year olds? I would have suspected not (which is why I started from a position of thinking this whole activity was somewhat ambitious), and that may well be why compromises were made in the teaching model adopted in this study.
But perhaps it would be better not to introduce an orbital model until we feel learners are ready to appreciate the quantum jump from concentric orbits to fuzzy, overlapping, infinitely-extended patterns of electronic probability, and the associated complex patterns of energy levels they generate. (But, again, the teaching model used may simply have been reflecting the target knowledge set out in the school curriculum in this particular national context? 4)
"Students do not clearly understand the concept of an orbital" (Aquilina, Dello Iacono, Gabelli, Picariello, Scettri & Termini, 2024)
Encouraging a new alternative conception?
To take one point. The 486 nm and 457 THz radiation is associated with transitions between n=3 and n=2 (656 nm) and n=4 and n=2 (486 nm) in the hydrogen atom, but NOT in the 'atom' populated with Montagues and Capulets.
Does this matter? After all, the point of the exercise is not to remember these specific values, but to be able to link radiation emitted or absorbed to electronic transitions – so, the particular values of 486 nm and 457 THz are irrelevant. True, but what students are potentially learning here is that the values of energy levels are not affected by the number of electrons repelling each other (here we have an ion with many electrons, but we can simply use the values for a hydrogen atom) – which is an alternative conception.
I also know that this is an alternative conception that learners are likely to readily develop. When students study ionisation energies, and make comparisons between different atoms, they often fail to allow for how the same designation of orbital does not imply an equivalence between differently populated electronic structures.
So, for example, a 2p orbital in an oxygen atom is not only not equivalent to a 2s orbital in the same atom: nor is it equivalent to a 2p orbital in a nitrogen atom. Nor, for that matter, is it entirely equivalent to a 2p orbital in the o2- anion.
This is not the most serious alternative conception that students can acquire, but given the complexity and challenge of this whole topic area, it might be wise to avoid risk misleading students when possible.
Or am I just being over-critical because I myself found the task too challenging? ☹️
To see through an orbital clearly?
This was an interesting project, and I hope the authors explore the idea further, and perhaps use their experiences with this implementation to further refine the activity. But I am not sure it is helpful in the long term to encourage learners to work with a model that is so constrained that it is likely to encourage new alternative conceptions.
But would that be the case? If the activity is part of a dialogic teaching sequence and the catalyst for engaging students in a discussion of these abstract ideas – a discussion that the teacher carefully steers towards the canonical account – then perhaps the outcome can be more productive. I guess we can only conjecture about this, until someone investigates the long-term effects of learning from the activity.
As usual, it is fair to say "more research is needed".
Aquilina, G.; Dello Iacono, U.; Gabelli, L.; Picariello, L.; Scettri, G.; Termini, G. "Romeo and Juliet: A Love out of the Shell": Using Storytelling to Address Students' Misconceptions and Promote Modeling Competencies in Science. Education Sciences, 2024, 14, 239. https://doi.org/10.3390/educsci14030239
Justi, R., & Gilbert, J. K. (2000). History and philosophy of science through models: some challenges in the case of 'the atom'. International Journal of Science Education, 22(9), 993-1009.
Taber, K. S. (2002) Conceptualizing quanta – illuminating the ground state of student understanding of atomic orbitals, Chemistry Education: Research and Practice in Europe, 3 (2), pp.145-158 [Download paper]
1 Of course there are many atoms, and indeed many kinds of atoms – so the use of the definite article ('the') is strictly inappropriate. But, this is common usage,
What seems potentially more problematic is the use of the definitive article when the referent is not a specific individual specimen. Chemistry teachers will say things like "the ammonia molecule is pyramidal" when no ammonia molecule is either specified directly or can be inferred to be the case in point from the context. This probably does not seem problematic for the simple reason that it does not matter which ammonia molecule is being referred to: they are all pyramidal. So, statements such as the ammonia molecular is pyramidal; the chlorine atom readily accepts an electron; the K shell is nearest the nucleus; and the iodide ion is a good leaving group; etcetera, will be true regardless.
These statements 'work' in a way that some apparently parallel statements from outside of chemistry would not: the house has a blue door, the man walks with a limp, the baby sneezed all night, the bicycle has squeaky brakes, etcetera. Some houses have blue doors – many do not…So, we should not say 'the house has a blue door' unless we have made it clear which house we are referring to. Yet, we do not need to say which particular water molecule is polar, as they all are (i.e., it may be considered an essential quality of a water molecule). So, the question here is why a teacher would say 'the ammonia molecule is pyramidal' when they are not actually referring to a particular specimen, and the point they are making is actually that (all) ammonia molecules are pyramidal.
Taber, 2019, p.128
And, even if we can refer to 'the carbon atom' when we mean any and all carbon atoms, to simply refer to 'the atom' seems a slight to the periodic table – surely we need to say which (kind of) atom we are modelling? That point certainly proved to be critical in the context of the modelling task discussed in this article!
2 The force is symmetrical – the same magnitude force acts on the nucleus and the electron, with each being pulled towards the other. Students commonly have alternative conceptions about this such as thinking the force only acts in one direction (from nucleus to electron) or that the force on the electron is greater.
3 In the planetary model of the atoms, electrons moved in orbits. In the orbital model we can think of electrons moving about the orbital, and the 'electron density' as a kind of average over time of where they have been. However, it may be more in keeping with the quantum model of the atom to suggest the electrons do not actually move around but rather have probabilities of being located at different points under conditions of observation. (According to a very common interpretation of quantum theory, the notion of an electron being somewhere specific only makes sense at the point of observation.) This is pretty difficult to appreciate (especially for most school-age learners), and I suspect most chemists are happy enough most of the time to think of the electrons moving around in their orbitals.
4 Five of the six authors, including the corresponding author, were based in Italy (the other author gave an affiliation based in Canada), so I assume the schools from which the work is reported is in Italy. The paper reports the task set and the student responses in English, so it is not clear if English was used as the language of instruction in the school (this seems unlikely unless this was an International School, but the paper does not report that material has been translated into English).
5 4f orbitals are not usually relevant to atomic structure till we consider cerium, element 58. But the familiar order of filling orbitals as we imagine we are building up atoms (1s < 2s < 2p< 3s < 3p < 4s < 3d < 4p… *) refers to species with more than one electron. For a hydrogen atom, a 4f orbtial is at the same energy level as the 4s orbital, as when occupied the atom's electron, neither would be sheilded at all from the nucleus by other electrons.
(* Ironically, the familiar descriptions of the discrete orbitals designated in this way are based on calculations for a hydrogen atom and do not strictly apply to multi-electron atoms. However the moodel generally works well, and is widely used.)
I would like to pose a simple quiz question. I think (?) the answer may be obvious to many science teachers, and advanced chemistry learners – but I wonder…
Consider the table below:
List 1
List 2
acid
alcohol
alkane
ether
metal
salt
protein
sugar
Two classes of chemical vocabulary?
The table contains some terms used in science, and especially in chemistry. But I have separated them into two lists, and I would suggest that there is a valid reason to class them into two separate categories in this way.
The ordering in the list is simply alphabetical – they are not intended to be paired (acid-alcohol, etc.): just in two categories.
This is not intended as a comprehensive classification – there are other examples (alkali, alkene, etc.) that could be added to the table.
The question is simple – what is the basis for this discrimination; what is different about the items in list 1, compared with those in list 2?
Too easy?
(As a bonus question: one of the entries, in one of the lists, might be considered to reflect the quality associated with the entries in that list in a more extreme form. Can you spot which item this is?)
I will post my reasoning in due course. But perhaps I will not need to (if you think you know the answer, please comment below).
The World Economic Forum has been compared to a chemical reaction between disparate molecules. (A group of Kenyans in traditional dress, Apple's co-founder Steve Jobbs, former UK minister Rachel Maclean, musician and activist will.i.am, and journalist Gillian Tett – includes images accessed from Pixabay)
Analogy is a key tool in the teacher's toolbox when 'making the unfamiliar familiar'. Science teachers are often charged with presenting ideas that are abstract and unfamiliar, and sometimes it can help if the teacher can point out how in some ways a seemingly obscure notion is just like something already familiar to the learner. An analogy goes beyond a simile (which simply suggests something is a bit like something else) by offering a sense of how the structure of the 'analogue' maps onto the structure of the 'target'.
Apologies are useful well beyond the classroom. They are used by science journalists reporting on scientific developments, and by authors writing popular science books; and by scientists themselves when explaining their work to the public. But analogies have a more inherent role in science practices: not only being both used in formal scientific accounts written to explain to and persuade other scientists about new ideas, but actually as a tool in scientific discovery as a source of hypotheses.
to explain something about working memory to a chemist – but could also be used
to explain fatty acid structureto a psychologist who already knew about working memory.
So, the use of a scientific idea as the source analogue for some other target idea suggests the user assumes the audience is also familiar with the science. Therefore I deduce that Gillian Tett, journalist at the Financial Times presumably is confident that listeners to BBC Radio 4 will be familiar with the concept of chemical reactions.
Tett was discussing her experience of the annual World Economic Forum meeting that has just been held in the snow of the Swiss skiing resort of Davos, and suggested that the mixing of various politicians and industry and media and lobbyists had the potential to lead to interesting outcomes – like some kind of chemistry experiment,
"I got jammed into a room with will.i.am, the rapper, who was talking about his views for A.I., and suddenly you've got these activists standing next to somebody from some of the big tech. companies, and a government minister, and a group from Kenya, all talking about whether A.I. could actually be a tool to reduce social inequality, rather than increase it. So, it is a bit like a chemistry experiment where you take all of these ambitious, self-selecting, hustling molecules from around the world, shove them into one test-tube, apply maximum pressure, and force them to collide with each other at close quarters with no sleep, and see what kind of compounds arise."
An experiment (by definition) has uncertain results, and Tett used the analogue of the chemistry experiment to imply that the diverse mixes of people collected together at Davos could lead to unexpected outcomes – just like mixing a diverse range of substances might. Tett saw the way such diverse groups become 'jammed' into rooms in arbitrary combinations as they make their ways around the meeting as akin to increasing the pressure of a reaction mixture of arbitrary reagents. This reflects something of the popular media notion of dangerous 'scientific experiments', as carried out by mad scientists in their basements. Real scientific experiments are carried out in carefully controlled conditions to test specific hypothesis. The outcome is uncertain, but the composition of the reaction mixture is carefully chosen with some specific product(s) in mind.
The figure below represents the mapping between the analogue (a rather undisciplined chemistry experiment) and the reaction conditions experienced by delegates in the melting pot of Davos.
the World Economic Forum at Davos is like a chemical experiment because…
Inspection of my figure suggests some indiscipline in the analogy. The reaction conditions are to "apply maximum pressure, and force [the molecules] to collide with each other at close quarters with no sleep". Now this phrasing seems to shift mid-sentence,
from the analogue (the chemical experiment:"apply maximum pressure, and force [the molecules] to collide with each other")
to the target (being jammed into a room at the conference: "at close quarters with no sleep").
One explanation might be that Gillian Tett is not very good at thinking though analogies. Another might be that, as she was being interviewed for the radio, she was composing the analogy off-the-cut without time to reflect and review and revise…
Either of those options could be correct, but I suspect this shift offered some ambiguity that was deliberately introduced rhetorically to increase the impact of the analogy on a listener. Tatt ('an anthropologist by training' and Provost of King's College, Cambridge) had described the molecules anthropomorphically: just as molecules do not sleep,
they cannot be 'ambitious', as this is a human characteristic;
they are not sentient agents, so cannot be 'self-selecting'; and
nor can they 'hustle' as they have no control over their movements.
But the journalists, politicians, activists and industrialists can be described in these terms, reinforcing the mapping between the molecules and the Davos delegates. So, I suspect that whilst this disrupted the strict mapping of the analogy, it reinforced the metaphorical way in which Tett wanted to convey the sense that the ways in which the Davos meeting offered 'experimental' mixing of the reacting groups had the potential to produce novel syntheses.
Richard Feynman was special. Any one who wins the Nobel prize has to be pretty special, but physics laureate Feynman was even more remarkable as he was an exceptionally high achieving research physicist also known for his…teaching. No one gets a Nobel for being a good teacher, and it is often considered in Academia that teaching (that is, if one tries to give teaching the time and energy required to do it well – as students deserve) distracts from research to such an extent that it is rare to excel in both.
Feynman had something a lot of scientists do not not: great charisma. (That is no insult to fellow scientists – most plumbers and greengrocers and bus drivers and accountants and hairdressers do not – that is what makes it notable). He might be considered the Albert Einstein of the second half of the twentieth century, and because of that timescale we are lucky to have quality recordings of him talking and teaching in a way that could not have happened with previous generations. (A great shame in many cases: if perhaps a blessing with some – Isaac Newton's lectures were apparently avoided by most of his own students.)
Like many people, I find Feynman bewitching – he had a sparkle about him – almost a permanent mischievous twinkle in the eye – and an ability to somehow express the excitement of science (of working out why things are as they are) whilst being able to talk in ways that could be understood by people that lacked his expertise. That is perhaps one trait of a great teacher – being able to talk at the level of the audience, despite personally understanding at a higher, more complex and subtle, level.
That is by way of preamble – as I want to consider an explanation Feynman once offered of surface tension.
Screenshot of Richard Feynman explaining why water forms into drops.
Why does it rain in drops?
The extract I am discussing is taken from a 1983 BBC series of short episodes in a series called 'Fun to Imagine'. Although, at the time of writing, the episodes are "not currently available" from the BBC site, there is a compilation on YouTube. One of the topics Feynman discusses is the origin of surface tension – although he only introduces the technical term after explaining the phenomenon that water forms into droplets,
"you see a little drop of water, a tiny drop And the atoms [sic, molecules] attract each other, they like to be next to each other They want as many partners as they can get Now the guys that are at the surface have only partners on one side here, in the air on the other side, so they're trying to get in And you can imagine…this teeming people, all moving very fast all trying to have as many partners as possible and the guys at the edge are very unhappy and nervous and they keep pounding in trying to get in, and that makes it a tight ball instead of a flat and that's what, you know, surface tension When you realise when you see how sometimes a water drop sits like this on a table then you start to imagine why it's like that because everybody is trying to get into the water"
Well, we might suggest Feynman makes a schoolchild error – water is not an atomic substance, but molecular. It does not contain discrete atoms, so he should be referring to the molecules attracting each other. But I do not think this is an error in the sense that Feynman was mistaken, simply that although the distinction is of great importance in chemistry, physicists sometimes use the term 'atom' generically to refer to the individual particles in a gas, for example. That might be unhelpful to a secondary school student studying for examinations, but if Feynman thought of his television audience for the recording as lay people, the general public, then perhaps the distinction between atoms (arguably a more familiar term in everyday discourse) and molecules would be considered an unhelpful detail? I am certainly prepared to give him that. I think it was the wrong choice, but not that Feynman was in error.
But what about the overall argument here. The 'atoms' want to have partners all around them 2 so they try to get inside the volume of the liquid. The overall effect of everyone, including these guys at the edge, trying to get inside the water is that it forms a sphere-like shape: "a tight ball instead of [something more] flat". Is that a convincing explanation – and is it a valid one?
What makes for a good explanation?
If anything is central to both science and science teaching, it is explanation.
"Explanation would seem to be central to the essence of science. A naïve view might claim that science discovers knowledge about the World, although it might be more accurate to suggest that science creates knowledge through the development of theories. The theories are used in turn to understand, predict and sometimes control the world, and in these activities, scientific explanations play the key role. We might consider theories and models to be the resources of science, but explanations to be the active processes through which theory is applied to contexts of interest…
An explanation is an answer to a 'why' question: but that in itself neither makes for a good explanation, nor for a scientific one. There is no simple answer to what does count as a good explanation, in science or elsewhere. Explanations have audiences, and to some extent, a good explanation is one that satisfied its audience – in other words it meets the explainee's purpose in seeking an explanation. Additionally, it has been known since at least Aristotle's time that we can talk of different kinds of causes, which suggests that many 'why questions' might have different types of acceptable responses, depending on the type of cause being sought."
That passage is taken from a chapter where I described some activities used with secondary school students to help teach them about the nature of scientific explanation. (Read about the classroom activities here.) In that context, working with learners who were about 14 years of age, students were told that a good scientific explanation would be logical, and would draw upon scientific theory,
"pupils were told that scientific explanations needed to take into account logic and theory, i.e., that the explanation needs to be rational, and the explanation needs to draw upon accepted scientific ideas. As the notion of 'theory' is itself known to be difficult for students, they were also told that scientific theories are ideas about the world which are well supported by evidence; are internally consistent; and which usually fit with other accepted theories."
In that regard, Feynman's explanation can be considered logical, even if it omits (i.e., he takes as assumed) an important step* that is needed to explain the (approximately) spherical shape of the water drop.
If water quanticles (let's leave aside whether they are atoms or molecules) want to have many partners 2, and so try to get inside the volume, then we can understand* that the water drop will tend to the smallest surface area possible, so as few quanticles end up at the surface (with the tenuous air, rather than congregating water partners, on one side) where they will be nervous, and as many quanticles as possible are in the interior of the drop where they will be happy.
* The missing step is to state that a spherical drop will have a smaller surface area than any other shape with the same volume and so fewest quanticles at the surface. Perhaps Feynman assumed everyone would know/see that. Probably there is no such thing as a totally complete explanation.
So, is this a good explanation?
Explanations can have different purposes. Scientific explanations allow us to make effective predictions (and so often to control situations – the application of science through technology). But, in everyday life, explanations have a more subjective purpose ("explanations have audiences, and to some extent, a good explanation is one that satisfied its audience").
If, as a result of hearing Feynman's explanation, the viewers of the BBC televison programme
felt they now understood why sphere-like drops of water form, and
considered they had made sense of some science, and so
appreciated the value of science in explaining everyday phenomena,
then perhaps the explanation achieved its purpose?
Was Feynman's explanation scientific?
Of course, if I am being my usual pedantic self, I could point out that although Feynman's explanation was logical, that does not make it scientific unless it also drew upon accepted scientific principles. It was logical because the explicandum (what was to be explained – here, the drop shape) followed from the premise (i.e., ifwater quanticles want to have many partners, and act accordingly, then…)
But, in science, quanticles are not understood as sentient actors, but as inanimate entities that are not (and cannot be) aware of their situation and cannot act deliberately to work towards personal goals. Therefore, no matter how convincing someone may have found this explanation, it does not qualify as a scientific explanation as it is not based on accepted scientific principles (…or at least, not directly).
An anthropomorphic explanation
Feynman's explanation uses anthropomorphism, which from a scientific perspective makes it a pseudo-explanation. A pseudo-explanation takes the form of an explanation in that it is presented as if an answer to a why question, but does meet the requirements for a formal explanation (e.g., it does "not logically fit the phenomenon to be explained into a wider conceptual scheme", Taber & Watts, 2000.)
There are various kinds of pseudo-explanations such as tautology (circular explanations that rely on the conclusions as premises) and simply offering a label for the explicandum (e.g., water absorbs a lot of heat for a small change in its temperature because it has a high heat capacity – this is a kind of disguised tautology, as a 'high heat capacity' is a way of characterising something that absorbs a lot of heat for a small change in its temperature).
Anthropomorphism explains by assuming that the entities involved can be considered to be like people, and, so, to be sentient, have feelings and opinions and preferences, and be able to plan and carry out actions that are intended to being about desired consequences.
It relies on an analogy that may not be appropriate:
if people were in a situation like this, they are likely to behave in a certain way
if we treat these entities as if they were people then we might expect them to behave as people would, therefore…
It is an open question to what extent we can assume animals (chimpanzees, dogs, birds, etc.) can be considered to share aspects of human-like experiences, emotions, thoughts, etcetera. Perhaps it is reasonable to suggest a dog can be sad or a chimp can be jealous. It may not be stretching credibility to suggest that members of some species of animals want to be in large groups, like to be in large groups, and perhaps may even get nervous when isolated? However, it stretches credibility when we are told that viruses are clever or that a bacterium can be happy.
And, there is a pretty strong scientific consensus that at the level of individual molecules there is no possibility of emotions, opinions, desires, thoughts, or deliberate actions. Atoms do not want to fill their electron shells, and genes cannot be selfish, except in a figurative sense.
So, in order to accept Feynman's explanation as valid, we would have to assume that the quanticles in water, water molecules,
like to be next to each other
want as many partners as they can get 2
can be unhappy and nervous
try to have as many partners as possible 2
try to get into the inside of the volume
So, to find this explanation convincing, we have to accept (contrary to science) that something like a water molecule is able to
have desires and preferences,
be aware of the extent to which is current situation matches its preferences, and,
deliberately act to bring about desired outcomes
[Feynman does not explicitly state that the quanticles know about their situation (point 2), but clearly this is implied as otherwise they would have no reason to be nervous and unhappy, nor to act to bring about change.]
These requirements are clearly not met. A being with a central nervous system as complex as a human can meet these requirements, but there is no conceivable mechanism by which molecules can be considered sentient, or to be deliberate agents in the world.
So, even if Feynman's explanation of surface tension satisfies viewers of the recording (i.e., is is subjectively an effective explanation) it fails as an objective, scientific, explanation. Feynman may indeed have been a 'genius' (Gleick, 1994), and a great physicist, but his explanation here is invalid and simply fails as good science.
Now a reader may suspect I have gone after a 'straw man' target here. Surely, Feynman was speaking figuratively, and not literally. Of course he was, but figurative language cannot support a logical explanation, except through an analogy we suspect to hold.
Consider the following hypothetical claim and two possible consequences if the claim was true
Claim
Consequence 1
Consequence 2
"I managed to get tickets for Toyah and Fripp's sold out concert in Bury St Edmunds, and these tickets are gold dust."
"I could sell these tickets at quite a mark up"
"I could put a sample of these tickets in a mass spectrometer and would find they had an atomic mass of 197."
If the claim was literally true, then consequence 2 would follow. But of course, it is meant as a figurative claim, where 'gold dust' is a metaphor for something of high value because it is rare. So, actually consequence 1 might follow, but not consequence 2.
In the same way, if water particles do not have likes, and do not try to do things, Fenyman's argument seems to fall apart…
A teaching model?
Now I would not presume to know better than Richard Feynman, and I am pretty sure (i.e., about as certain as I can be of anything) that Feynman would not have fallen into the mistake of thinking that atoms or molecules actually act like humans and want things, or try to do things. He surely knew this was not a scientific explanation, but he clearly thought this was a useful way of explaining (to his audience) why water forms into a drop.
Now, I suggested above that Feynman's narrative account of the origin of surface tension "is not based on accepted scientific principles (…or at least, not directly)". But near the outset of this account Feynman states that the water particles "attract each other":
"the [molecules] attract each other, they like to be next to each other"
Feynman was not only a researcher, but a teacher, and teachers use teaching models. I think this is what Feynman is doing here:
"[according to science] the [molecules] attract each other [and we can think of this as if] they like to be next to each other"
Affinity in the sense of human experience is used as a kind of analogyfor the affinity between water molecules (which leads to hydrogen bonding and dipole-dipole interactions). Once we model inter-molecular forces as being like attractions between people, we can extend the analogy in terms of how people feel when they do not get what they want, and how they respond by acting in ways that they hope will get them what they want.
Looked at this way, Feynman is doing something that good teachers often do when they judge a scientific model is too abstract, sophisticated, complex, subtle, for their audience; they simplify by substituting a teaching model which represents the scientific model in terms more familiar and accessible to the learners.
From this perspective, Feynman's explanation may not have been a valid scientific explanation, but we might ask if it was an effective intermediate explanation set out in terms of a teaching model. That is, perhaps Feynman's explanation may have satisfied viewers, and also potentially acted as a possible foundation for building up to a more technical, scientifically acceptable explanation.
Teachers and other science communicators often use anthropomorphism as a way of offering accounts of complex scientific topics that will appeal and make sense to learners of a public audience.
This can be effective to the extent that it engages learners, leaves the audience with a subjective sense of making sense of the science, and provides accounts that are often remembered later.
Of course that is not so helpful if the audience is studying a science course, and think they have learnt an account which will get them credit in formal examinations! I know from my own teaching career that learners often find anthropomorphic explanations readily come to mind, even when then they have been taught more technical accounts they are expected to apply when assessed.
In public science communication, then, anthropomorphic accounts may be valuable in offering people some sense of the science. But in formal education we need to be careful as even if anthropomorphism offers a useful way of getting learners familiar with some abstract topic (what might be called 'weak' anthropomorphism: Taber & Watts, 1996), we need to avoid them learning and committing to that metaphoric 'social' account thinking it is a valid scientific account ('strong' anthropomorphism).
Mapping Feynman's explanation
If we see Feynman as offering an analogy as a teaching model then we might seek to 'translate' his terms into more scientific concepts. He tells us that attraction is 'liking', and we can perhaps think of 'wanting' and being 'nervous' as indicating a higher (excited) energy state, 'pounding' as being subject to unbalanced forces, and 'trying to get in' as tending to evolving toward a lower energy configuration. At least, someone who already understood the scientific account could suggest such mappings. It seems unlikely any one who did not appreciate the science already could interpret it that way without a knowing and careful guide.
And like all anthropomorphic explanations, it 'suffers' from the very quality that it offers a narrative which is likely to be more easily understood, better related to, and more readily recalled, than the scientific account. This is why I have very mixed feelings about the use of anthropomorphism in formal science teaching, as even when it (a) does a great job of engaging learners and offering them some level of understanding, this may be at the cost of (b) offering an account which many students will find it hard to later let go of and progress beyond.
Screenshot of Richard Feynman explaining why water forms into drops.
As a good teacher, Feynman would know to pitch his teaching for particular audiences depending on their likely level of background knowledge. The explanation discussed here was not how Feynman taught about surface tension in his undergraduate classes at the California Institute of Technology (Feynman, Leighton & Sands, 1963). We can imagine that had he told students at Caltech that water formed into spherical drops because all the molecular guys are trying to get into the water, he might indeed had heard the retort: Surely you are joking, Prof. Feynman? 1
Work cited:
Feynman, R. P., Leighton, R. B., & Sands, M. (Eds.). (1963). The Feynman Lectures on Physics (3 Volumes). Addison-Wesley Publishing Company.
Gleick, J. (1994) Genius: Richard Feynman and Modern Physics. Abacus.
1 My subtitle is a reference to the book 'Surely you're Joking Mr Feynman: Adventures of a Curious Character' in which Feynman tells anecdotes from his life.
2 Water was perhaps a poor example to choose as there is extensive hydrogen bonding in liquid water,
"I suspect even some experienced chemists may underestimate the extent of hydrogen bonding in water. According to one source…, in liquid water at the freezing point, the typical water molecule is at any time bonded by three or four hydrogen bonds – compared with the four bonds in the solid ice structure."
Taber, 2020, p.98
So, in Feynman's analogy, a water molecules does not become happy (lower energy state) when it is surrounded by as many other water molecules as possible, but when it is aligned with 3 or 4 other molecules to hydrogen bond, if only transiently. Without the hydrogen bonding, the drop would still be approximately spherical, but it would be smaller and denser as the molecules could get even closer together, but it would evaporate away more readily.
Does the medieval notion of the human body as a microcosm of the wider Cosmos – in which is played out an eternal battle between good and evil – still influence our thinking?
Keith S. Taberwants to tell you a story
Are you sitting comfortably?
Good, then I will begin.
Once upon a time there was an evil microbe. The evil microbe wanted to harm a human being called Catherine, and found ways for his vast army of troops to enter Catherine's body and damage her tissues. Luckily, unbeknown to the evil microbe, Catherine was prepared to deal with invaders – she had a well-organised defence force staffed by a variety of large battalions, including some units of specialist troops equipped with the latest anti-microbe weapons. There were many skirmishes, and then a series of fierce battles in various strategic locations – and some of these battles raged for days and days, with heavy losses on both sides. No prisoners were taken alive. Many of Catherine's troops died, but knowing they had sacrificed themselves for the higher cause of her well-being. But, in the end, all of the evil microbe's remaining troops were repelled and the war was won by the plucky defenders. There was much rejoicing among the victorious army. The defence ministry made good records of the campaign to be referred to in case of any future invasions, and the surviving soldiers would long tell their stories of ferocious battles and the bravery of their fallen comrades in defeating the wicked intruders. Catherine recovered her health, and lived happily ever after.
There is a myth, indeed, perhaps even a fairy story, that is commonly told about microbial disease and immunity. Disease micro-organisms are 'invaders' and immune cells are 'defenders' and they engage in something akin to warfare. This is figurative language, but has become so commonly used in science discourse that we might be excused for forgetting this is just a stylistic feature of science communication – and so slip into habitually thinking in the terms that disease actually is a war between invading microbes and the patient's immune system.
Immunity is often presented through a narrative based around a fight between opposed sentient agents. (Images by Clker-Free-Vector-Images and OpenClipart-Vectors from Pixabay.)
Actually this is an analogy: the immune response to infection is in some waysanalogous to a war (but as with any analogy, only in some ways, not others). As long as we keep in mind this is an analogy, then it can be a useful trope for talking and thinking about infectious disease. But, if we lose sight of this and treat such descriptions as scientific accounts, then there is a danger: the myth undermines core biological principles, such that the analogy only works if we treat biological entities in ways that are contrary to a basic commitment of modern science.
In this article I am going to discuss a particular, extensive, use of the disease-as-war myth in a popular science book (Carver, 2017), and consider both the value, and risks, of adopting such a biological fairy-tale.
Your immune system comprises a vast army of brave and selfless soldiers seeking to protect you from intruders looking to do you harm: an immune response is a microcosm of the universal fight between good and evil?
A myth is a story that has broad cultural currency and offers meaning to a social group, usually involving supernatural entities (demons, superhuman heroes, figures with powerful magic), but which is not literally true.
Carver's account of the immune system
I recently read 'Immune: How your body defends and protects you' (henceforth, 'Immune') by Catherine Carver. Now this is clearly a book that falls in the genre 'popular science'. That is, it has been written for a general audience, and is not meant as a book for experts, or a textbook to support formal study. The publishers, Bloomsbury, appropriately describe Carver as a 'seasoned science communicator'. (Appropriately, as metaphorical dining features strongly in the book as well.)
Carver uses a lot of contractions ("aren't", "couldn't", "doesn't", "don't", "isn't", "it's", "there's", "they're", "we've", "what's", "who'd", "wouldn't", "you'd") to make her writing seem informal, and she seems to make a special effort to use metaphor and simile and to offer readers vivid scenes they can visualise. She offers memorable, and often humorous, images to readers. A few examples offer an impression of this:
"…the skin cells…migrate through the four layers of the epidermis, changing their appearance like tiny chameleons…"
"Parietal cells dotted around the surface of the stomach are equipped with proton pumps, which are like tiny merry-go-rounds for ions."
"a process called 'opsonisation' make consuming the bacterial more appealing to neutrophils, much like sprinkling tiny chocolate chips on a bacterial cookie."
"The Kupffer cells hang around like spiders on the walls of the blood vessels…"
In places I wondered if sometimes Carver pushed this too far, and the figurative comparisons might start to obscure the underlying core text…
"…the neutrophil…defines cool. It's the James Dean of the immune system; it lives fast, dies young and looks good in sunglasses."
Carver, 2017, p.7
"The magnificence of the placenta is that it's like the most efficient fast-food joint in the world combined with a communications platform that makes social media seem like a blind carrier pigeon, and a security system so sophisticated that James Bond would sell his own granny to the Russians just to get to play with it for five minutes."
Carver, 2017, p.113
When meeting phrases such as these I found myself thinking about the metaphors rather than what they represented. My over-literal (okay, pedantic) mind was struggling somewhat to make sense of a neutrophil in (albeit, metaphoric) sunglasses, and I was not really sure that James Bond would ever sell out to the Russians (treachery being one of the few major character faults he does not seem to be afflicted by) or be too bothered about playing with a security system (his key drives seem focused elsewhere)…
…but then this is a book about a very complex subject being presented for an audience that could not be assumed to have anything beyond the most general vague prior knowledge of the immune system. As any teacher knows, the learner's prior knowledge is critical in their making sense of teaching, and so offering a technically correct account in formal language would be pointless if the learner (or, here, reader) is not equipped to engage at that level.
'Immune' is a fascinating and entertaining read, and covers so much detailed ground that I suspect many people reading this book would would not have stuck with something drier that avoided a heavy use of figurative language. Even though I am (as a former school science teacher *) probably not in the core intended audience for the book, I still found it very informative – with much I had not come across before. Carver is a natural sciences graduate from Cambridge, and a medical doctor, so she is well placed to write about this topic.
Catherine Carver's account of the immune system is written to engage a popular readership and draws heavily on the disease-as-war analogy.
My intention here is not to offer a detailed review or critique of the book, but to explore its use of metaphors, and especially the common disease-as-war theme (Carver draws on this extensively as a main organising theme for the book, so it offers an excellent exemplar of this trope) – and discuss the role of the figurative language in science communication, and its potential for subtly misleading readers about some basic scientific notions.
The analogy
The central analogy of 'Immune' is clear in an early passage, where Carver tells us about the neutrophil,
"…this cell can capture bubonic plague in a web of its own DNA, spew out enzymes to digest anthrax and die in a kamikaze blaze of microbe-massacring glory. The neutrophil is a key soldier in an eternal war between our bodies and the legions of bacteria, viruses, fungi and parasites that surround us. From having sex to cleaning the kitchen sink, everything we do exposes us to millions of potential invaders. Yet we are safe. Most of the time these invaders' attempts are thwarted. This is because the human body is like an exceedingly well-fortified castle, defended by billions of soldiers. Some live for less than a day, others remember battles for years, but all are essential for protecting us. This is the hidden army that we all have inside of us…"
Carver, 2017, p.7
Phew – there is already a lot going on there. In terms of the war analogy:
We are in a perpetual war with (certain types) of microbes and other organisms
The enemy is legion (i.e., has vast armies)
These enemies will invade us
The body is like a well-protected fort
We have a vast army to defend us
There will be battles between forces from the two sides
Some of our soldiers carry out suicide (kamikaze) missions
Our defenders will massacre microbes
We (usually) win the battles – our defences keep us safe
Some of these specific examples can be considered as metaphors or similes in they own right when they stand alone, but collectively they fit under an all-encompassing analogy of disease-as-war.
But this is just an opening salvo, so to speak. Reading on, one finds many more references to the 'war' (see Boxes 1 and 2 below).
The 'combatants' and their features are described in such terms as army, arsenals, assassins, band of rebels, booby-traps, border guards, border patrol force, commanders, defenders, fighting force, grand high inquisitors, hardened survivor, invaders, lines of defence, muscled henchman, ninjas, soldiers, terminators, trigger-happy, warriors, and weapons.
Disease and immune processes and related events are described in terms such as alliance, armoury, assassination campaign, assault, assault courses, attack, battlefield, bashing, battles, boot camp, border control, calling upsoldiers, chemical warfare, cloaking device, craft bespoke weaponry, decimated, dirty bomb, disables docking stations, double-pronged attack, exploding, expose to a severe threat,fight back, fighting on fronts, friendly fire, go on the rampage, hand grenades, heat-seeking missiles, hold the fort, hostile welcome, instant assault , kamikaze, killer payload, massacring, patrolling forces, pulling a pin on a grenade, R & R [military slang for 'rest and recuperation'], reinforcing, security fence, self-destruct, shore updefences, slaughters/slaughtering, smoke signals, standing down, suicidal missions, Swiss army knife, taking on a vast army on its home turf, throwing dynamite, time bomb, toxic cloud, training camp, training ground, trip the self-destruct switch, Trojan horse, victories, war, and wipe out the invader.
Microbes and cells as agents
A feature of the analogue is that war is something undertaken by armies of soldiers, that are considered as having some level of agency. The solder is issued with orders, but carries them out by autonomous decision-making informed by training as well as by conscience (a soldier should refuse to obey an illegal order, such as to deliberately kill civilians or enemy combatants who have surrendered). Soldiers know why they are fighting, and usually buy into at least the immediate objectives of the current engagement (objectives which generally offer a more favourable outcome for them than for the enemy soldiers). A soldier, then, has objectives to be achieved working towards a shared overall aim; purposes that (are considered to) justify the actions taken; and indeed takes deliberate actions intended to bring out preferred outcomes. Sometimes soldiers may make choices they know increase risks to themselves if they consider this is justified for the higher 'good'. These are moral judgements and actions in the sense of being informed by ethical values.
An extensive range of terminology related to conflict is used to describe aspects of disease and the immune response to infection. (Image sources: iXimus [virus], OpenClipart-Vectors [cell], Tumisu [solders in 'Raising the Flag on Iwo Jima'-like poses], from Pixabay.)
Now, I would argue that none of this applies to either disease organisms nor components of a human immune system. Neither a bacterium nor an immune cell know they are in a war; neither have personal, individual or shared, objectives; and neither make deliberate choices about actions to take in the hope they will lead to particular outcomes. No cell knowingly puts itself at risk because it feels a sacrifice is justified for the benefit of its 'comrades' or the organism it is part of.
So, all of this might be considered part of what is called the 'negative analogy', that is, where the analogy breaks down because the target system (disease processes and immune responses) no longer maps onto the analogue (a war). Perhaps this should be very obvious to anyone reading about the immune system? At least, perhaps scientists might assume this would be very obvious to anyone reading about the immune system?
Now, if we are considering the comparison that an immune response is something like a nation's defence forces defending its borders against invaders, we could simply note that this is just a comparisonbut one where the armies of each side are like complex robotic automatons pre-programmed to carry out certain actions when detecting certain indicators: rather than being like actual soldiers who can think for themselves, and have strategic goals, and can rationally choose actions intended to bring about desired outcomes and avoid undesired ones. (A recent television advertising campaign video looking to recruit for the British Army made an explicit claim that the modern, high-tech, Army could not make do with robots, and needed real autonomous people on the battlefield.)
However, an account that relies too heavily on the analogy might be in danger of adopting language which is highly suggestive that these armies of microbes and immune cells are indeed like human soldiers. I think Carver's book offers a good deal of such language. Some of this language has already been cited.
Immune cells do not commit kamikaze
Consider a neutrophil that might die in a kamikaze blaze of microbe-massacring glory. Kamikaze refers to the actions of Japanese pilots who flew their planes into enemy warships because they believed that, although they would surely die and their planes be lost, this could ensure severe damage to a more valuable enemy resource – where the loss of their own lives was justified by allowing them to remain at the plane's controls until the collision to seek to do maximum damage. Whatever we think of war in general, or the Kamikazi tactics in particular, the use of this term alludes to complex, deliberate, human behaviour.
Immune cells do not carry out massacres
And the use of the term massacre is also loaded. It does not simply mean to kill, or even to kill extensively. For example, the Jallianwala Bagh massacre, or Amritsar massacre, is called a massacre because (British) soldiers with guns deliberately fired at, with intent to kill or seriously injure, a crowd of unarmed Indians who were in their own country, peacefully protesting about British imperial policies. The British commanders acted to ensure the protesters could not easily escape the location before ordering soldiers to fire, and shooting continued despite the crowd trying to flee and escape the gunfire. Less people died in the Peterloo Massacre (1819) but it is historically noteworthy because it represented British troops deliberately attacking British demonstrators seeking political reform, not in some far away 'corner of Empire', but in Manchester.
Amritsar occurred a little over a century ago (before modern, post-Nurenmberg, notions of the legality of military action and the responsibility of soldiers to not always follow orders blindly), but there are plenty of more recent examples where the term 'massacre' is used, such as the violent clearing of protesters in Tiananmen Square in 1989 and the Bogside 'Bloody Sunday' massacre in 1972 (referenced in the title of the U2 song, 'Sunday Bloody Sunday'). In these examples there is seen to be an unnecessary and excessive use of force against people who are not equipped to fight back, and who are not shown mercy when they wish to avoid or leave the confrontation.
'Monument in Memory of Chinese from Tiananmen in Wrocław, Poland' commemorating the massacre of 4th June 1989 when (at least) hundreds were killed in Beijing after sections of the People's Liberation Army were ordered to clear protesters from public places (Masur, Public domain, via Wikimedia Commons)
The term massacre loses its meaning without this sense of being an excessively immoral act – and surely can only apply to an action carried out by 'moral agents' – agents who deliberately act when they should be aware the action cannot be morally justified, and where they can reasonably see the likely outcomes. (Of course, it is more complicated that this, in particular as a soldier has orders as well as a conscience – but that only makes the automatic responses of immune cells towards pathogens even less deserving of being called a massacre.)
The term moral agent does not mean someone who necessarily behaves morally, but rather someone who is able to behave morally (or immorally) because they can make informed judgements about what is right and wrong – they can consider the likely consequence of their actions in terms of a system of values. An occupied building that collapses does harm to people, but cannot be held morally responsible for its 'behaviour' in the way a concentration camp guard or a sniper can be. A fox that takes a farmer's chickens has no conception of farming, or livestock, or ownership, or of the chickens as sentient beings that will experience the episode from a different perspective, but just acts instinctively to access food. Microbes and cells are like the building or the fox, not the guard or the sniper, in this respect.
Moreover, in the analogue, the massacred are also moral agents: human beings, with families, and aspirations for their futures, and the potential for making unique contributions to society… I am not convinced that bacteria or microbes are the kinds of entities that can be massacred.
Anthropomorphic references
Carver then writes about the immune system, or its various components, as well as various microbes and other pathogenic organisms, as though they are sentient, deliberative agents acting in the world with purposes. After all, wars are a purely human phenomenon.1 Wars involve people: people with human desires, motives, feelings, emotions, cunning, bravery (or not), aims and motivations.
Anthropomorphism is describing non-human entities as if they are people. Anthropomorphism is a common trope in science teaching (and science communication) but learners may come to adopt anthropomorphic explanations (e.g., the atom wants…) as if they are scientific accounts (Taber & Watts, 1996).
Bacteria, body cells and the like are not these kinds of entities, but can be described figuratively as though they are. Consider how,
"Some bacteria are wise to this and use iron depletion as an indicator that they are inside an animal. Other bacteria have developed their own powerful iron-binding molecules called 'siderophores' which are designed to snatch the iron from the jaws of lactoferrin. Perhaps an even smarter strategy is just to opt out of the iron wars altogether…
…tear lipocalin, whose neat structure includes a pocket for binding a multitude of molecules. This clever pocket allows tear lipocalin to bind the bacterial siderophores…neutralising the bacterium's ability to steal iron from us…"
Carver, 2017, pp.20-21
Of course, bacteria are only 'wise' metaphorically, and they only 'develop' and 'design' molecules metaphorically, and they only adopt 'smarter strategies' or can 'opt out' of activities metaphorically – and as long as the reader appreciates this is all figurative language it is unproblematic. But, when faced with multiple, and sometimes extended, passages seeming to imply wise and clever bacteria developing tools and strategies, could the reader lose sight of this (and, if so, does that matter?)
If bacteria are not really clever, nor are pockets (or 'pockets' – surely this is a metaphor, as actual pockets are designed features not evolved ones). Stealing is the deliberate taking of something one knows is owned by someone else. Bacteria may acquire iron from us, but (like the fox) they do not stealas they have no notion of ownership and property rights, nor indeed, I suggest, any awareness that those environments from which they acquire the iron are considered by them[our]selves as 'us'.
That is, there is an asymmetrical relationship here: humans may be aware of the bacteria we interact with (although this has been so only very recently in historical terms) but it would be stretching credibility to think the bacteria have any awareness – even assuming they have ANY awareness in the way we usually use the term – of us as discrete organisms. So, the sense in which they "use iron depletion as an indicator that they are inside an animal" cannot encompass a deliberate use of an indicator, nor any inference they are inside an animal. There is simply a purely automatic, evolved, process that responds to environmental cues.
I have referred in other articles posted here to examples of such anthropromorphic language in public discourse being presented apparently in the form of explanations: e.g.,
My focus here is Catherine Carver's book, but it is worth bearing in mind that even respectable scientific journals sometimes publish work describing viruses in such terms as 'smart', 'nasty', 'sneaky' – and, especially it seems, 'clever' (see 'So who's not a clever little virus then?'). So, Carver is by no means an outlier or maverick in using these devices.
'Immune' is embellished throughout with this kind of language – language that suggests that parasites, microbes, body cells, or sometimes even molecules:
act as agents that are aware of their roles and/or purposes;
do things deliberately to meet objectives;
have preferences and tastes.
The problem is, that although this is all metaphorical, as humans we readily interpret information in terms of our own experiences, so a scientific reading of a figurative text may requires us to consciously interrogate the metaphors and re-interpret the language. Historians of chemistry will be well aware of the challenge from trying to make sense of alchemical texts which were often deliberately obscured by describing substances and processes in metaphoric language (such as when the green lion covers the Sun). Science communicators who adopt extensive metaphors would do well to keep in mind that they can obscure as well as clarify.
For example, Carver writes:
"…the key to a game of hide and seek is elementary: pick the best hiding place. In the human body, the best places to hide are those where the seekers (the immune system) find it hard to travel. This makes the brain a very smart place for a parasite to hide."
Carver, 2017, p.132
'There is a strong narrative here ("the eternal game of hide and seek [parasites] play with us")- most of us are familiar with the childhood game of hide and seek, and we can readily imagine microbes or parasites hiding out from the immune cells seeking them. This makes sense, because of course, natural selection has led to an immune system that has components which are distributed through the body in such a way that they are likely to encounter any disease vectors present – as this increases fitness for the creature with such a system – and natural selection has also led to the selection of such vectors that tend to lodge in places less accessible to the immune cells – as this increase fitness of the organism that we2 consider a disease organism. Thus evolution has often been described, metaphorically, as an arms race.
But this is not really a game(which implies deliberate play – parasites can not know they are playing a game); and the disease vectors do not have any conception of hiding places, and so do not pick where to go accordingly, or using any other criterion; the immune cells are not knowingly seeking anything, and do not experience it being harder to get to some places than others (they are just less likely to end up in some places for purely naturalistic reasons).
So, a parasite that ends up in the brain certainly may be less accessible to the immune system, but is not deliberately hiding there – and so is no more 'smart' to end up there than boulders that congregate at the bottom of a mountainside because they think it is a good place to avoid being sent rolling by gravity (and perhaps having decided it would be too difficult to ascend to the top of the mountain).4
It is not difficult to de-construct a text in the way I have done above for the hide-and-seek comparison- if a reader thinks this is useful, and consequently continually pauses to do so. Yet, one of the strengths of a narrative is that it drives the reader forward through a compelling account, drawing on familiar schemata (e.g., hide and seek; dining; setting up home…) that the reader readily brings to mind to scaffold meaning-making.
Another familiar (to humans) schema is choosing from available options:
"…the neutrophil's killer skills come to the fore…It only has to ask one question: which super skills should be deployed for the problem at hand?"
Carver, 2017, p.27
So, it seems this type of immune cell has 'skills', and can pose itself (and answer) the question of which skills will be most useful in particular circumstances (perhaps just like a commando trained to deal with unexpected scenarios that may arise on a mission into enemy-held territory?) Again, of course, this is all figurative, but I wonder just how aware most readers are of this as they read.
Carver's account of Kupffer cells makes them seem sentient,
"The Kupffer cells hang around like spiders on the walls of the blood vessels waiting to catch any red blood cells which have passed their best before date (typically 120 days). Once caught, the red blood cell is consumed whole by the Klupffer cell, which sets about dismantling the haemoglobin inside its tasty morsel."
Carver, 2017, p.27
Kupffer cells surely do not 'hang around' or 'wait' in anything more than a metaphorical sense. If 'catching' old red blood cells is a harmless metaphor, describing them as tasty morsels suggests something about the Kupffer cells (they have appetites that discriminate tastes – more on that theme below) that makes them much more like people than cells.
Another striking passage suggests,
"Some signals are proactive, for example when cells periscope from their surface a receptor called ULBP (UL16-binding protein). Any NK cell that finds itselfshaking hands with a ULBP receptor knows it has found a stressed-out cell. The same is true if the NK cell extends its receptors to the cell only to find it omits parts of the secret-handshakeexpected from a normal cell. Normal, healthy cells display a range of receptors on their surface which tell the world 'I'm one of us, everything is good'. Touching these receptors placates NK cells, inhibiting their killer ways. Stressed, infected cells display fewer of these normal receptors on their surface and in the absence of their calming presence the trigger-happy NK cells attack."
Carver, 2017, p.27
That cells can 'attack' pathogens is surely now a dead metaphor and part of the accepted lexicon of the topic. But cells are clearly only figuratively telling the world everything is good – as 'telling' surely refers to a deliberate act. The hand-shaking, including the Masonic secret variety (n.b., a secret implies an epistemic agent capable of of knowing the secret), is clearly meant metaphorically – the cell does not 'know' what the handshake means, at least in the way we know things.
If the notion of a cell being stressed is also a dead metaphor (that is 'stressed' is effectively a technical term here {"the concept of stress has profitably been been exported from physics to psychology and sociology" Bunge, 2017/1998}), a stressed-out cell seems more human – perhaps so much so that we might be subtly persuaded that the cell can actually be placated and calmed? The point is not that some figurative language is used: rather, the onslaught (oops, it is contagious) of figurative language gives the reader little time to reflect on how to understand the constant barrage of metaphors…
"…it takes a bit of time for the B cells to craft a specific antibody in large quantities. However the newly minted anti-pollen antibodies are causing mischief even if we can't see evidence of it yet. They travel round the body and latch on to immune cells called masts anywhere they can find them. This process means the person is now 'sensitised' to the pollen and the primed mast cells lie in wait throughout the body…"
Carver, 2017, pp.183-184
…so, collectively the language can be insidious – cells can 'craft' antibodies (in effect, complex molecules) which can cause mischief, and find mast cells which lie in waitfor their prey.
Sometimes the metaphors seemed to stretch even figurative meaning. A dying cell will apparently 'set its affairs in order'. In humans terms, this usually relates to someone ensuring financial papers are up to date and sorted so that the executors will be able to readily manage the estate: but I was not entirely sure what this metaphor was intended to imply in the case of a cell.
Animistic language
Even a simple statement such as "First the neutrophil flattens itself"(p.28) whilst not implying a conscious process makes the neutrophil the active agent rather than a complex entity subject to internal mechanisms beyond its deliberate control. 3
So, why write
"Finally, the cell contracts itself tightly before exploding like a party popper that releases deadly NETs [neutrophil extracellular traps] instead of streamers."
Carver, 2017, p.27
rather than just "…the cell contracts tightly…"? I suspect because this offers a strong narrative (one of active moral agents engaged in an existential face-off) that is more compelling for readers.
Neutrophils are said to 'gush' and to 'race', but sometimes to be slowed down to a 'roll' when they can be brought to a stop ("stopping them in their tracks" if rolling beings have tracks?). But on other occasions they 'crawl'. Surely crawling is a rather specific means of locomotion normally associated with particular anatomy. Typically, babies crawl (but so might soldiers when under fire in a combat zone?)
There are many other examples of phrases that can be read as anthropomorphic, or at least animistic, and the overall effect is surely insidious on the naive reader. I do not mean 'naive' here to be condescending: I refer to any reader who is not so informed about the subject matter sufficiently to already understand disease and immunity as natural processes, that occur purely through physical and chemical causes and effects, and that have through evolution become part of the patterns of activity in organisms embedded in their ecological surroundings. A process such as infection or an immune response may look clever, and strategic, and carefully planned, but even when very complex, is automatic and takes place without any forethought, intentions, emotional charge or conscious awareness on the part of the microbes and body cells involved.
There are plenty of other examples in 'Immune' of phrasing that I think can easily be read as referring to agents that have some awareness of their roles/aims/preferences, and act accordingly. And by 'can easily be read', I suspect for many lay readers (i.e., the target readership) this means this will be their 'natural' (default) way of interpreting the text.
So (see Box 3 , below), microbes, cells, molecules and parasites variously are in relationships, boast, can beckon and be beckoned, can be crafty, can be egalitarian, can be guilty, can be ready to do things, can be spurred on, can be told things, can be treacherous, can be unaware (which implies, sometimes they are aware), can dance choreographed, can deserve blame, can find things appealing, can have plans, can mind their own business, can pay attention, can spot things, can take an interest, can wheedle (persuade), congregate, craft things, dare to do things, do things unwittingly, find things, get encouraged, go on quests, gush, have aims, have friends, have goals, have jobs, have roles, have skills, have strategies, have talents, have techniques, insinuate themselves, know things, like things, look at things, look out for things, play, outwit, race, seek things, smuggle things, toy with us, and try to do things.
Microbes moving in
One specific recurring anthropomorphic feature of Carver's descriptions of the various pathogens and the harmless microbes which are found on and in us, is related to finding somewhere to live – to setting up a home. Again, this is clearly metaphorical, a microbe may end up being located somewhere in the body, but has no notion, or feeling, of being at home. Yet the schema of home – finding a home, setting up home, being at home, feeling at home – is both familiar and, likely, emotionally charged, and so supports a narrative that fits with our life-experiences.
A squatter among pathogen society? Images by Peter H (photograph) and Clker-Free-Vector-Images (superimposed virus) from Pixabay
Viruses and bacteria are compared in terms of their travel habits (in relation to which, "The human hookworm…[has] got quite an unpleasant commute to work…"),
"…viruses are the squatters of pathogen society. Unlike bacteria, which tend to carry their own internal baggage for all their disease-making needs, viruses pack light. They hold only the genes they need to gain illegal entry to our cells and then instruct our cells' machinery to achieve the virus's aims. The cell provides a very happy home for the virus, and also gives it cover from the immune system."
Carver, 2017, p.35
These pathogens apparently form a society (where there is a distinction between what is and what is not legal 5) and individually have needs and aims. A virus not only lives in a home, but can be happy there. Again, such language does have a sensible meaning (if we stop to reflect on just what the metaphors can sensibly mean), but it is a metaphorical meaning and so should not be taken literally.
"…the human microbiota is the collective name for the 100 trillion micro-organisms that have made us their real estate. From the tip of your tongue to the skin you sit on, they have set up home in every intimate nook and cranny of our body…The prime real estate for these microbes, the Manhattan or Mayfair equivalent inside you and me, is the large intestine or colon. If you had a Lonely Planet or Rough Guide to your gut, the colon would have an entry something like this: 'The colon is a must-see multi-cultural melting-pot, where up to one thousand species of bacteria mingle and dine together every second of every day. In this truly 24/7 subterranean city, Enterococcirub shoulders with Clostridia; Bacteroides luxuriate in their oxygen-depleted surroundings and Bifidobacteria banquet on a sumptuous all-you-can-eat poo buffet. It's the microbe's place to see, and be seen'. ….[antibiotic's] potential to kill off vast swathes of the normal gut flora. This creates an open-plan living space for a hardy bacterium called Clostridium difficile. This so-called superbug (also known as C. diff) is able to survive the initial antibiotic onslaught and then rapidly multiplies in its newly vacated palace."
Carver, 2017, p.76-78
This metaphor is reflected in a number of contexts in Immune. So, the account includes (see Box 4, below) break ins, camps, communities, homes, lounging, palaces, penthouses, playgrounds, preferred places to live, real estate, residents, shops, squatters, suburban cul-de-sacs, and tenants .
What is for dinner?
The extracts presented above also demonstrate another recurring notion, that microbes and body cells experience 'eating' much like we do ('tasty morsel', 'dine together', 'banquet…buffet'). There are many other such illusions in 'Immune'.
We could explain human eating preferences and habits in purely mechanistic terms of chemistry, physics and biology – but most of us would think this would miss an important level of analysis (as if what people can tell us about what they think and feel about their favourite foods and their eating habits is irrelevant to their food consumption) and would be very reductive. Yet, when considering a single cell, such as a Kupffer cell, surely a mechanistic account in terms of chemistry, physics and biology is not reductionist, but exhaustive. Anything more is (as Einstein suggested about the aether) superfluous.
One favoured dining location is the skin:
"The Demodexdine on sebum (the waxy secretion we make to help waterproof our skin), as well as occasionally munching on our skin cells and even some unlucky commensal bacteria like Propionibacterium acnes…like many of us, P. acnes is a lipophile, which is to say it adores consuming fat. The sebum on our skin is like a layer of buttery, greasy goodness that has P. acnessmacking its lips. However, when P. acnes turns up to dine it has some seriously bad table manners, which can include dribbling chemicals all over our faces…[non-human] animal sebum lacks the triglyceride fats that P. acnes [2 ital] loves to picnic on." p.82
Carver, 2017, pp.81-82
It is hopefully redundant, by this point, for me to point out that Propionibacterium acnes does not adore anything – neither preferred foodstuffs nor picnics – but has simply evolved to have a nutritional 'regime' that matches its habitat. Whilst this extract immediately offers a multi-course menu of metaphors, it is supplemented by a series of other semantic snacks. So 'Immune' also includes references to buffet carts, chocolate chips, cookies, devouring, easy meals, gobbling up, making food appetising, making food tastier, munching, a penchant for parma ham and rare steak, soft-boiled eggs, tasty treats and yummy desserts.
Can you have too much of a metaphorical good thing?
I am glad I bought 'Immune'. I enjoyed reading it, and learnt from it. But perhaps a more pertinent question is whether I would recommend it to a non-scientist* interested in learning something about immunity and the immune system. Probably, yes, but with reservations.
Is this because I am some kind of scientific purist (as well as a self-acknowledged pedant)? I would argue not: if only because I am well aware that my own understanding of many scientific topics is shallow and rests upon over-simplifications, and in some cases depends upon descriptive accounts of what strictly need to be appreciated in formal mathematical terms. I do not occupy sufficiently high ground to mock the novice learner's need for images and figures of speech to make sense of unfamiliar scientific ideas. As a teacher (and author) I draw on figurative language to help make the unfamiliar become familiar and the abstract seem concrete. But, as I pointed out above, figurative language can sometimes help reveal (to help make the unfamiliar, familiar); but can also sometimes obscure, a scientific account.
I have here before made a distinction between the general public making sense of science communication in subjective and objective terms. Objective understanding might be considered acquiring a creditable account (that would get good marks in an examination, for example). But perhaps that is an unfair test of a popular science book: perhaps a subjective making-sense, where the reader's curiosity is satisfied – because 'yes, I see, that makes sense to me' – is more pertinent. Carver has not written 'Immune' as a text book, and if readers come away thinking they have a much better grasp of the immune system (and I suspect most 'naive' readers certainly would think that) then it is a successful popular science book.
My reservation here is that we know many learners find it difficult to appreciate that cornerstone of modern biology, natural selection (e.g., Taber, 2017), and instead understand the living world in much more teleological terms – that biological processes meet ends – occur to achieve aims – and do so through structures which have been designed with certain functions in mind.
So, microbes, parasites, cells, and antibodies, which are described as though they are sentient and deliberate actors – indeed moral agents seeking strategic goals, and often being influenced by their personal aesthetic tastes – may help immunity seem to make sense, but perhaps by reinforcing misunderstandings of key foundational principles of biology.
In this, Catherine Carver is just one representative of a widespread tendency to describe the living world in such figurative terms. Indeed, I might suggest that Carver's framing of the immune system as a defence force facing hostile invaders makes 'Immune' a main-stream, conventional, text in that it reflects language widely used in public science discourse, and sometimes even found in technical articles in the primary literature.
A myth is a story that has broad cultural currency and offers meaning to a social group, usually involving supernatural entities (demons, superhuman heroes, figures with powerful magic – perhaps microbial aesthetes and sentient cells?), but which is not literally true. e.g., Your immune system comprises a vast army of brave and selfless soldiers seeking to protect you from intruders looking to do you harm: an immune response is a microcosm of the universal fight between good and evil?
My question, then, is not whether Carver was ill-advised to write 'Immune' in the way she has, but whether it is time to more generally reconsider the widespread use of the mythical 'war' analogy in talking about immunity and disease.
Notes
1 Even if, for example, some interactions between groups of ants from different nests {e.g., see 'Ant colony raids a rival nest | Natural World – Empire of the Desert Ants – BBC'} look just as violent as anything from human history, their 'battles' are surely not planned as part of some deliberate ongoing campaign of hostilities.
2 The bacteria infecting us, if they could conceptualise the situation (which they cannot), would have no more reason to consider themselves a disease, than humans who 'infected' an orchard and consumed all the fruit would consider themselves a disease. Microbes are not evil for damaging us, they are just being microbes.
3 If my rock analogy seems silly, it is because we immediately realise that rocks are just not the kind of entities that behave deliberately in the world. The same is true of microbes and body cells -they are just not the kind of entities that behave deliberately in the world, and as long as this is recognised such metaphorical language is harmless. But I am not sure that is so immediately obvious to readers in these cases.
4 Such an issue can arise with descriptions about people as well. If I want to share a joke with a friend I may wink. If a fly comes close to my eye I may blink. Potentially these two actions may seem indistinguishable to an observer. However, the first is a voluntary action, but in the second case the 'I' that blinks is not me the conscious entity that ascribes itself self-hood, but an autonomous and involuntary subsystem! In a sense a person winks, but has blinking done to her.
5 If entry to our cells was 'illegal' in the sense of being contrary to natural laws/laws of nature, it would not occur.
* A note on being a scientist. Any research scientists reading this might scoff at my characterisation of the readers of popular science books as being non-scientists with the implied suggestion that I, by comparison, should count as a scientist. I have never undertaken research in the natural sciences, and, although I have published in research journals, my work in science education would be considered as social science – which in the Anglophile world does not usually count as being considered 'science' per se. However, in the UK, the Science Council recognises science educators as professional scientists. Learned societies such as the Royal Society of Chemistry and the Institute of Physics will admit teachers of these subjects as professional members, and even Fellows once their contributions are considered sufficient. This potentially allows registration as a Chartered Scientist. Of course, the science teacher does not engage in the frontiers of a scientific research field in the way a research scientist does, however the science teacher requires not only a much broader knowledge of science, but also a specialist professional expertise that enables the teacher to interrogate and process scientific knowledge into a form suitable for teaching. This acknowledges the highly specialised nature of teaching as an expert professional activity which goes far beyond the notion of teaching as a craft that can be readily picked up (as sometimes suggested by politicians).
Work cited
Bunge, M. (2017/1998). Philosophy of Science. Volume 1: From problem to theory. Routledge. (1967)
Carver, C. (2017). Immune. How your body defends and protects you. Bloomsbury Sigma.
"neutrophil is a key soldier" "the human body is like an exceedingly well-fortified castle, defended by billions of soldiers" "…the incredible arsenal that lives within us…" "the hidden army" "…our adaptive assassins, our T and B cells" "The innate system is the first line of defence…" skin: "…an exquisite barrier that keeps unwanted invaders out." "…your airways are exceedingly well booby-trapped passages lined with goblet cells, which secrete a fine later of mucus to trap dirt and bacteria." "Initially it was seen as a simple soldier with a basic skills set …Now we know it is a crafty assassin with a murderous array of killing techniques." "…ninja skill of neutrophils…", "ninja neutrophils" "macrophages are stationed at strategic sites…what an important outpost the liver is for the immune system" "NK cells [have] killer ways" "trigger-happy NK cells" "Ever neat assassins, NK cells" "vicious immune cells" compared to "a pack of really hungry Rottweilers" interleukins are "pro-inflammatory little fire-starters" "neutrophils, macrophages and other immune system soldiers" "T cells…activate their invader-destroying skills." "…a weapon with a name worthy of a Bond villain's invention: the Membrane Attack Complex" "miniature mercenaries" "a system whose raise d'etre is to destroy foreign invaders" "everything we do exposes us to millions of potential invaders." "…all invaders need an entry point…" "these tiny sneaks [e.g., E. coli]" "the dark-arts of pus-producing bacteria…" Neisseria meningitidis: "this particular invader" "foreign invaders" "an aggressive border patrol" 'Tregs are the prefects of the immune system…" "…the parasite larva has more in common with a time bomb…" "T cells…are the grand high inquisitors of the immune system, spotting and destroying infected cells and even cancer…these assassins" "imagining you have to make a Mr Potato Head army, and you know that the more variety in your vegetable warriors the better" "this process is about …making a mutant army." "they form a fighting force that rivals Marvel Comic's Fantasic Four" "each antibody molecule released as a single soldier" "The pancreas … acts as the commander-in-chief when its comes to controlling blood sugar levels." "our tiny but deadly defenders" "cells in the spleen with a specialised killer-skill" "wears a mask that conceals its killer features from its would-be assassins" "the microbiological mass murderers…the serial killers" "PA [protective antigen] is the muscled henchman" "the murderous cast of immune cells and messengers…this awe-inspiring army" "a microscopic army, capable of seeking out and destroying bacteria" "the terminators are targeted killers" "weaponised E. coli
Box 1: References to the immune system and its components as a defence force
"a kamikaze blaze of microbe-massacringglory" "an eternal war between our bodies and the legions of bacteria, viruses, fungi and parasites that surround us" "these invaders' attempts are thwarted" "battles" "all my innate defences would essentially hold the fort and in many instances this first line would be enough to wipe out the invader before the adaptive system gets a chance to craft bespoke weaponry." "the tears we shed [are] a form of chemical warfare." "…allowing the neutrophils to migrate through the blood vessel and into the battlefield of the tissue beyond" "the cell contracts itself tightly before exploding" "their friendly fire contributed to the death of the victim." "spewing microbe-dissolving chemicals into the surround tissue. This allows the neutrophil to damage many microbes at once, a bit like fishing by throwing dynamite into the water." "NK [natural killer] cells target the microbes that have made it inside our cells." "NK cells attack" "…the initial hole-poking assault…" "all part of the NK cell's plan to kill the cell." "…they trip the cell's self-destruct switch" "expose a cell to a severe, but not quite lethal threat…transform the cell into a hardened survivor" immune cells have an "ability to go on the rampage" "call up … immune system soldiers to mount a response" "leukaemia … has decimated a type of white blood cells called T cells" "it behaves like a Trojan horse [as in the siege of the City of Troy]" "telling our soldier cells to kick back and take some R & R" "the smoke signals of infection" "…like a showing of tiny hand grenades on the surrounding cells." "the donor cells would be vastly outnumbered and it would be like a band of rebels taking on a vast army on its home turf" "the recipient's own immune system is in a weakened state and unable to fight back" "…the antibodies …are therefore able to give a hostile welcome to alpha-gal-wearing malaria parasites." "…our gut bacteria effectively provide a training ground for the immune system – a boot camp led by billions of bacteria which teaches us to develop an arsenal of antibodies to tackle common foreign invader fingerprints…" "fighting on certain fronts" "edgy alliance" "shore up the intestinal defences by reinforcing the tight junctions which link the gut cells together" "our gut's security fence" "a self-cell that should be defended, not attacked" "this mouse-shaped Trojan horse" "the scanning eyes of the immune system" "a form of border control, policing" "…the bacteria-bashing brilliance…" "…the IgA effectively blocks and disables the invaders' docking stations…" "B cells and their multi-class antibody armoury have the ability to launch a tailored assassination campaign against almost anything" "the exquisitely tailored assassination of bacteria, viruses and anything else that dares enter the body" "One of the seminal victories in our war on bugs" "Some bacteria have a sugar-based cloaking device" "…tripped by the pollen attaching to the IgE-primed mast cells and, like pulling a pin on a grenade, causing them to unleash their allergy-inducing chemicals." "The almost instant assault of the immediate phase reaction occurs within minutes as the dirty bomb-like explosion of the mast cell fill the local area with a variety of rapidly acting chemicals." "..the battle against infectious diseases." "teaching the patrolling forces of the immune system to stand down if the cell they're interrogating is a healthy cell that belong to the body. It's a bit like a border patrol force wandering through the body and checking passports" "like a training camp for the newly created border guards". "ordering those that react incorrectly to self-destruct" "These bacteria have a sugar-based polysaccharide outer shell, which acts like a cloaking device" "the [oncolytic] viruses have a Swiss army knifeselection of killer techniques" "This approach slaughters these foot soldiers of our immune system…" "they [macrophages] have picked up a time bomb" "antibodies that act like heat-seeking missiles" "Kadcyla …has a double-pronged attack." "we are setting up easy antibiotic assault courses all over the place" "His suicidal minions were engineered to seek out a pneumonia-causing bacterium by the name of Pseudomonas aeruginosa and explode in its presence releasing a toxic cloud of a Pseudomonas-slaughtering chemical called pyocin." "it could secrete its killer payload" "stimulate the little terminators to produce and release their chemical warfare."
Box 2: References to disease and immune processes as war and violent activity
"The macrophage's … job as a first responder…" " osteoclasts and osteoblasts" are "Carver refers to "the bony equivalent of yin and yang…osteoblasts are the builders in this relationship" (said to be "toiling") …osteoclast, whose role is the constant gardener of our bones" "…a white blood cell called the regulatory T cell, or 'Treg' to its friends…" "…this biological barcode lets the T cell know that it's looking at a self-cell …" "…the ball of cells that makes up the new embryo finishes bumbling along the fallopian tube and finds a spot in the uterus to burrow into…" "By using this mouse-shaped Trojan horse the parasite gets itself delivered directly into the cat's gut, which is where Toxoplasma likes to get it on for the sexual reproduction stage of its lifecycle." "It's as if the trypanosome has a bag of hats that it can whip out and use to play dressing-up to outwit the immune system." "proteins… help smuggle the ApoL1 into the parasite" "Some parasites have a partner in crime…" "the chosen strategy of the roundworm Wuchereria bancrofti…uses a bacterium to help cloak itself from the immune system." "the work of a master of disguise…precisely what Wuchereria bancrofti is." "…its bacterial side-kick" "parasites that act as puppet masters for our white blood cells and direct our immune response down a losing strategy" "parasites with sartorial skills that craft themselves a human suit made from scavenged proteins" "parasites toy with us" "B cells have one last technique" "Chemical messengers beckon these B cells" "what AID [activation induced deaminase] seeks to mess with" "Each class [of antibody] has its own modus operandi for attacking microbes" "in terms of skills, IgG can activate the complement cascade" "…one of its [IgA] key killer skills is to block any wannabe invaders from making their way inside us." "the helper T cell and the cytotoxic T cell, which take different approaches to achieve the same aim: the exquisitely tailored assassination of bacteria, viruses and anything else that dares enter the body." "B cells, cytoxic T cells and macrophages in their quest to kill invaders" "T cells interact with their quarry" "add a frisson of encouragement to the T cell, spurring it on to activation." "the brutally egalitarian smallpox" "Polio is another virus that knows all about image problems." "the guilty allergen" "IgE and mast cells are to blame for this severe reaction [anaphylaxis]" "…The T regulatory cells identify and suppress immune cells with an unhealthy interest in normal cells." "the skills of a type of virus well versed in the dark arts of integrating into human DNA" "The spleen is a multi-talented organ" "to get rid of the crafty, cloaked bacteria" "Even once cells are able to grow despite the chemical melting pot they're stewing in telling them to cease and desist…" "It is believed that tumour cells bobbing about in the bloodstream try to evade the immune system by coating themselves in platelets…" "the cancer's ability to adorn itself" "They [oncolytic viruses] work by …drawing the attention of the immune system" "when the replicating virus is finally ready to pop its little incubator open" "…anthrax, which lurks in the alveoli awaiting its cellular carriage: our macrophages…" "The macrophages are doing what they ought … Completely unaware that they have picked up a time bomb…" "the microbial thwarting talents of interferons" "…your mAbs will do the legwork for you, incessantly scouring the body for their target destination like tiny, demented postal workers without a good union." "One of the tumour techniques is to give any enquiring T cells a 'these aren't the cells you're looking for' handshake that sends them on their way in a deactivated state, unaware they have let the cancer cells off the hook. Checkpoint inhibitor mAbs bind to the T cell and prevent the deactivating handshake from happening. This leaves the T cell alert and able to recognise and destroy the cancer cells." "A third neutrophil strategy…" "all part of the NK cell's plan to kill the cell." "…a majestic dance of immune cells and messengers, carefully choreographed…" "So my immune system's bag of tricks might not currently include a smallpox solution, but if I were to contract the disease my adaptive immune response would try its hardest to create one to kill the virus before it killed me." "Thus earwax can catch, kill and kick out the multitude of microbes that wheedle their way into out ears…" "Up to 200 million neutrophils gush out of our bone marrow and into the blood stream every day. They race around the blood on the look-out for evidence of infection." "a process called 'opsonisation' make consuming the bacterial more appealing to neutrophils" "the same siren call of inflammation and infection that beckoned the neutrophils." "…a set of varied and diverse circumstances can prompt multiple macrophages to congregate together and, like a massive Transformer, self-assemble into one magnificent giant cell boasting multiple nuclei." "The cell responds to the initial hole-poking assault by trying to repair itself…At the same time that it pulls in the perforin holes, the cell unwittingly pulls in a family of protein-eating granzymes…" "the gigantosome is more than just a pinched-off hole-riddled piece of membrane; its creation was all part of the NK cell's plan to kill the cell." caspases in cells "play an epic game of tag" Arachidonic acid: "Normally it just minds its own business" "The interferon molecule insinuates itself into the local area" "The chemokines …their ability to beckon a colourful array of cells to a particular location…they can call up neutrophils, macrophages and other immune system soldiers to mount a response to injury and infection…" "chemicals that can tell these cells where to go and what to do. These crafty chemicals…" "…the triad of goals of the complement system…" "It's the T cell's job to spot infected or abnormal cells." "Microbes aren't easy bedfellows" "…the 'lean' microbes won out over the 'obese' ones." "IgD is the most enigmatic of all the immunoglobins" "the parasite larva …treacherous"
Box 3: Examples of phrasing which might suggest that microbes, cells, etc., are sentient actors with human motivations
"Bifidobacterium infantis, a normal resident of the healthy infant gut" "trillions of microbes that make us their home" "…a much more diverse community of inner residents…" "Entamoeba … just happened to prefer to live in a multicultural colon." "…the mouth had the least stable community, like the microbial equivalent of transient squatters, while the vagina was the quiet suburban cul-de-sac of the map, with a fairly fixed mix of residents." "that's where they [Mycobacteria] set up home" "Neisseria meningitidis "sets up shop inside our cells…it breaks in…" "…Heliocobacter pylori (a.k.a H. pylori), a bacterium that makes its home in the sticky mucus that lines the stomach. While the mucus gives H. pylori some protection from the gastric acid, it also employed a bit of clever chemistry to make its home a touch more comfortable." Dracunculus medinensis will "seek out a mate, turning the abdominal wall into their sexual playground." "…plenty of creepy crawlies have been known to to call the human brain home, lounging among our delicate little grey cells…" the tapeworm Spirometra erinaceieuropaei : "…this particular tenant ensconced in their grey matter." "the worm…wriggled up through his body to reach its cranial penthouse where it could enjoy the luxury of a very special hiding spot." "There are flatworms, roundworms hookworms, whipworms, fleas and ticks, lice and amoeba. They're all queuing up to get a room at the palace of parasites" Clostridium tetani "can often set up camp in soil", "About 75 million people worldwide are thought to carry the dwarf tapeworm in their small intestine, where it lives a fairly innocuous life and causes its host few if any symptoms." "Though it may not seem like it, our nostrils are prime real estate and rival bacteria fight each other for resources, a fight which includes chemical warfare." "…we'll meet the creepy critters that like to call us home and the ways our immune system tries to show them the door."
Box 4: Microbes and cells described as the kind of entities which look for and set up homes.
"an all-you-can-eat oligosaccharide buffet for B. infantis [Bifidobacterium infantis]" "…complement's ability to make these bacteria seem tastier to our macrophages…" "Mycobacteria… actually want to be gobbled up by our macrophages…" "sprinkling C3b on the surface of bacteria makes them much more appetising to microbe-munching cells" macrophages 'devour' the remains of dead cells "…Salmonella, which likes a soft-boiled egg, and Toxoplasma gondii, which shares my penchant for parma ham and rare steak." Dracunculus medinensis "looks like an easy meal for a peckish water flea. Sadly for the water flea the parasite larva has more in common with a time bomb than a tasty snack ever should, and the treacherous morsel spends the next 14 days inside the flea…" "…flagging a microbe as munchable for macrophages…" "IgG …can mark targets as munchable. Thus any bacterium, virus or parasite coated in IgG finds itself the yummiest dessert on the buffet cart and every hungry macrophage rushes to get itself a tasty treat." "…from our brain to our bones, we are riddled with munching macrophages…" opsonisation: "much like sprinkling tiny chocolate chips on a bacterial cookie" "Demodex dine on sebum…as well as occasionally munching on our skin cells" "P. acnes is a lipophile, which is to say it adores consuming fat. The sebum on our skin is like a layer of buttery, greasy goodness that has P. acnes smacking its lips." "when "P. acnes turns up to dine it has some seriously bad table manners" " P. acnes loves to picnic."
Box 5: References to the culinary preferences and habits of entities such as microbes and immune cells
I have designed a simple concept cartoon. Concept cartoons are used in teaching, usually as an introductory activity to elicit students' ideas about a topic before proceeding to develop the scientific account. This can be seen as 'diagnostic assessment' or just part of good pedagogy when teaching topics where learners are likely to have alternative conceptions. (So, in science teaching, that means just about any topic!)
But I am retired and no longer teach classes, so why am I spending my time preparing teaching resources?
Well, I was writing about dialogic teaching, and so devised an outline lesson plan to illustrate what dialogic teaching might look like. The introductory activity was to be a concept cartoon, so I thought I should specify what it might contain – and so then I thought it would help a reader if I actually mocked up the cartoon so it would be clear what I was writing about. That led to:
A concept cartoon provides learners with several competing ideas to discuss (This can be downloaded below)
What happens, and why?
In my concept cartoon the focal question is what will happen when some NaCl is added to water – and why? This is a concept cartoon because there are several characters offering competing ideas to act as foci for learners to discuss and explore. Of course, it is possible to ask learners to engage with a cartoon individually, but they are intended to initiate dialogue between learners. So by talking together learners will each have an audience to ask them to clarify, and to challenge, their thinking and to ensure they try to explain their reasoning.
Of course, there is flexibility in how they can be used. A teacher could ask students to consider the cartoon individually, before moving to small group discussions or whole class discussion work. (It is also possible to move from individual work to pairing up, to forming groups from two pairs, to the teacher then collating ideas from different groups.) During this stage of activity the intention is to let student make their thinking explicit and to consider and compare different views.
Of course, this is a prelude to the teacher persuading everyone in the class of the right answer, and why it is the right answer. Concept cartoons are used where we know student thinking is likely to make that stage more than trivial. Where learners do already have well-entrenched conceptions at odds with the scientific models, we know simply telling them the target curriculum account is unlikely to lead to long-term shifts in their thinking.
And even if they do not, they will be more likely to appreciate, and later recall, the scientific account if the ground is prepared in this way by engaging students with the potential 'explanatory landscape' (thinking about what is to be explained, and what explanation might look like). If they become genuinely engaged with the question then the teacher's presentation of the science is given 'epistemic relevance'. (Inevitably the science curriculum consists of answers to the questions scientists have posed over many years: but in teaching it we may find we are presenting answers to many questions that simply have never occurred to the students. If we can get learners to first wonder about the questions, then that makes the answer more relevant for them – so more likely to be remembered later.)
Is there really likely to be a diversity of opinion?
This example may seem fairly straightforward to a science teacher. Clearly NaCl, sodium chloride (a.k.a. 'common salt' or 'table salt') is an ionic solid that will dissolve in water as the ions are solvated by the polar water molecules clustering around them. That should also be obvious to advanced students. (Should – but research evidence suggests not always.)
What about students who have just learned about ionic bonding and the NaCl crystal structure? What might they think?
Surely, we can dismiss the possibility that salt will not dissolve? Everyone knows it does. The sea is pretty salty, and people often add salt to the water when cooking. And as long as learners know that NaCl is 'salt' there should be no one supporting the option that it does not dissolve. After all, there is a very simple logical syllogism to be applied here:
common salt dissolves in water
common salt is NaCl
so NaCl dissolves in water
Except, of course, learners who know both that salt dissolves in water and that it is NaCl still have to bring both of those points to mind, and coordinate them – and if they are juggling other information at the same time they may have reached the 'working memory capacity' limit.
Moreover, we know that often learners tend to 'compartmentalise' their learning (well, we all do to some extent), so although they may engage with salt in the kitchen or dinner table, and learn about salt as NaCl in science lessons, they may not strongly link these two domains. And the rationale offered here by the student in red, that NaCl is strongly bonded, is a decent reason to expect the salt to be insoluble.
Now as I have just made this cartoon up, and do not have any classes to try it out on, I may be making a misjudgement and perhaps no learners would support this option. But I have a sneaking suspicion there might be a few who would!
The other two options are based on things I was told when a teacher. That the solid may dissolve as separate atoms is based on being told by an advanced student that in 'double decomposition' reactions the precipitate was produced when atoms in the solution paired up to transfer electrons. The student knew the solutions reacting (say of potassium iodide and lead nitrate) contained ions, but obviously (to my informant) the ions changed themselves back into atoms before forming new ionic bonds by new electron transfers.
I was quite shocked to have been told that, but perhaps should not have been as it involves two very common misconceptions:
(Moreover, another advanced student once told me that when bonds broke electrons had to go back to their 'own' atom as it would be odd for an atom to end up with someone else's electron! So, by this logic, of course anions have to return electrons to their rightful owners before ironically bonding elsewhere!)
So, I suspect a fair number of students new to learning about ionic bonding might well expect it to dissolve as atoms rather than ions.
As regards the other option, that the salt dissolves as molecules, I would actually be amazed if quite a few learners in most classes of, say, 13-14-year-olds, did not select this option. It is very common for students to think that, despite its symmetrical crystal structure (visible in the model in the cartoon), NaCl really comprises of NaCl units, molecule-like ions pairs – perhaps even seen as simply NaCl 'molecules'.
It becomes the teacher's job to persuade learners this is not so, for example, by considering how much energy is needed to melt NaCl , and the conductivity of the liquid and the aqueous solution. (In my imaginary lesson the next activity was a 'Predict-Observe-Explain' activity involving measuring the conductivity of a salt solution.)
A challenge to science teachers
Perhaps you think the students in your classes would not find this a challenging task, as you have taught them that NaCl is an ionic solid, held together by the attractions between cations and anions? All your students know NaCl dissolves, and that the dissolved species will (very nearly always) be single hydrated ions.
Perhaps you are right, and I am wrong.
Or perhaps you recognise that given that in the past so many students have demonstrated alternative conceptions of ionic bonding (Taber, 1994) that perhaps some of your own students may find this topic difficult.
As I no longer had classes to teach, I am uploading a copy of the cartoon that can be downloaded in case you want to present this to your classes and see how they get on. This is primary for students who have been introduced to ionic bonding and taught that salts such as NaCl form solids with regular arrangements of charged ions. If they have not yet studied salts dissolving then perhaps this would be a useful introductory ability for that learning that content?
If you have already taught them about salts dissolving, then obviously they should all get the right answer. (But does that mean they will? Is it worth five minutes of class-time to check?)
And if you work with more advanced students who are expected to have mastered ionic bonding some years ago, then we might hope no one in the class would hesitate in selecting the right answer. (But can you be sure? You could present this as something designed for younger students, and ask your students how they would tutor a younger bother or sister who was not sure what the right answer was.)
If you do decide to try this out with your students – I would really like to know how you get on. Perhaps you would even share your experience with other readers by leaving a comment below?
Analogies are thinking tools as well as communication tools.
Keith S. Taber
Analogy is very familiar to science teachers as a tool for communicating ideas (one way to help 'make the unfamiliar familiar'), but analogies have also been important to research scientists themselves. Analogy can be a useful thinking tool for scientists, as well as a means of getting across novel ideas.
Indeed we might suggests that analogies have roles that might be described as exploratory, autodidactic, and pedagogic:
I wonder if it is like this? A creative source of ideas generating hypothesis to test out;
Ah, I see, it is like this! A tool for making sense of something that seems unfamiliar to us;
You see, it is somewhat like this… A tool for helping others to make sense of some novel or unfamiliar notion.
On this site, I have given quite a lot of attention to the pedagogic, communicative role of analogies as used by teachers – and also by other communicators of science such as journalists, and indeed sometimes also scientists themselves when writing for their colleagues. As well as discussing some teaching analogies in detail in blog postings, I've also compiled some examples I have come across from my reading and other sources (such as radio items).
I was recently using an analogy myself to communicate an idea as part of a talk I had been asked to give. I set up an analogy to illustrate four categories in a model of 'bugs' that can occur in teaching-learning when students either do not understand, or misunderstand (misinterpret), teaching. I was trying to explain an educational model to science teachers, so used some science (that I assumed would be familiar to the audience) as the analogue.
An analogy involves a comparison between the structures of two systems where there is an explicit mapping to show similar structural features between the two systems – the analogue being used to explain and the target being explained. (If that sounds a bit obscure, there is an example presented in the table below).
Analogy as a thinking tool
I readily found 'mappings' for my four categories, so my analogy 'worked' (for me!) But, in working out the analogy, I realised that there was an additional option, a variation on one of the categories, that I had not fully appreciated. That is, by thinking about an analogy, I discovered a potential mapping back to my model that I had not expected, so the act of developing an analogy (meant to communicate the idea) actually deepened my own understanding of the model.
This is just the kind of thinking that analogy as an exploratory tool can offer (even if that was not how I was intending to use the analogy). This did not lead to a drastic rethinking of my model, but I thought it was interesting how working with the analogy could offer a slightly different insight into the original model.
Accommodating concepts
This puts me in mind of how concepts can both grow and then be modified by analogical thinking in science. For example, when (the substance that was to be named as) potassium was first discovered it had a combination of properties quite unlike any previously known substances. It seemed to share some – but not all – properties with the group of known substances referred to as metals, so it could be considered a metal by analogy with them. But for potassium (and then sodium) to be accepted as actual metals (not just partial analogies of metal) it was necessary to modify the set of properties considered essential to a substance that was classed as a metal (Taber, 2019).
(Of course, it seems 'obvious' to us now that potassium and sodium are metals – but that is with the benefit of hindsight, as the metal concept we learnt about in chemistry had long since been adapted to 'accommodate' the alkali metals.)
Types of learning blocks
The 'target' material in my talk was the typology of learning impediments which is meant to set out the types of 'bugs' that can occur in a 'teaching learning system'. That is, when
"there is a teacher who wishes to teach some curriculum material that has been prepared for the class; and a learner, who is present; willing, and in a fit state, to learn; who is paying attention in class; and where there is a good communication channel, which will normally mean that the learner and teacher can see and hear each other clearly… even when this system exists, we cannot be confident the learner will always understand what is being taught in the manner intended"
The teacher-learner system – a learner, motivated to study, able to see and hear the teacher, and paying attention to the teacher's clear explanation of a scientific idea: "even when this system exists, we cannot be confident the learner will always understand what is being taught in the manner intended"
The model has four main categories of system 'bugs', organised in two overarching classes:
A null learning impediment meant the student failed to associate teaching with prior learning – that the teaching did not lead to the learning bringing to mind something that helped them make sense of the teaching. This could be because the expected prior learning had never happened, called a deficiency learning impediment; or because the relevance of prior learning was not appreciated (i.e., not associated), a so-called fragmentation learning impediment.
The two main types of substantive learning impediments involve the learner making sense of teaching in a way that does not match that intended, either because the relevant prior learning includes alternative conceptions, and so the learning is distorted by being understood within a conceptual framework that does not match the science; or through the teaching being understood in the context of some other prior learning that seemed relevant to the learner, but which, from the teacher's perspective, was not pertinent. These are referred to in the model as grounded learning impediments and associative learning impediments, respectively.
A typology of learning impediments: things that go wrong even when the teacher explains the concepts clearly, and the learner wants to learn and is paying attention.
The analogy that came to mind was from biochemistry (perhaps because I had recently been thinking about the metaphors and analogies in a book on that subject?) As meaningful learning requires teaching to be related to (fit into, anchor in, make sense of in terms of) some prior learning available to the learner, I envisaged learning as being analogous to some small molecule that in metabolism became bound to a protein (an enzyme perhaps) which was only possible because there was a good fit between the molecular configurations of the protein (a component of the learners' existing conceptual structure) and the metabolite (the information provided in teaching).
An analogy for learning – a metabolite will only bind to a protein if there is a good 'fit' between the structures.
These signs were somewhat arbitrary symbols, except that they had an iconic feature – a complicated shape representing the molecular conformation that could indicate the presence or absence of a binding site capable of leading to complex formation.
Learning was modelled as the binding of the metabolite (information presented in teaching) with the protein (an existing feature of conceptual structure) into a new complex (new information from teaching assimilated into prior learning).
Learning was seen as analogous to the binding of a metabolite to a protein…
Each of my four main types of learning block seemed to have a parallel in scenarios where the metabolite would not become tightly bound to the protein in the molecular analogue.
Impediments to assimilating the metabolite
The learner can only relate new information to prior learning if they have indeed learnt that material. If the teacher assumes that students have already learnt some prerequisite material but the learner has not (perhaps a previous teacher ran out of time and missed the topic; or the learner was off-school ill at the time; or the learner attended a lesson on the material, but made no sense of it; or the student attended a lesson on the material which made sense at the time, but the material was never reinforced in later lessons, so was never consolidated into long-term memory…) then this will be as if the target protein is missing from the cytosol, so there is no target structure for the metabolite to bind to:
…and the binding could not occur if the protein was not present…
Then, even if a student has the expected prior learning, they will only interpret new information in terms of it if they realise its relevance. Teachers may assume it is obvious what prior leaning is being relied upon to make sense of new teaching, but sometimes this prior learning is not triggered as pertinent and so 'brought to mind' by the learner. (Or, to be fair to the teacher, they may have even deliberately reminded students of the relevant prior learning just before introducing the new material, but without the learner realising this was meant to be linked in any way!)
So, this is as if the two molecules are both present in a cell's cytosol, but they never come close enough to interact and bind:
…and binding could not occur if the metabolite molecule did not come into contact with the protein…
Now students often have alternative conceptions ('misconceptions') of science topics. So, even if they do know about the topic that the new teaching is expected to develop for them, if they have a different understanding of the topic, then – although they may interpret the new information in terms of their existing understanding of the topic – they will likely understand the new teaching in a distorted way so it fits with their alternative take on the topic.
I thought that, in my analogy, an alternative conception was like a protein that was 'mis-structured' (as may happen if there are genetic mutations). If a mutation only subtly changes the shape of the binding site on the protein it is possible that the complex may form, but with a different, more strained, conformation. So, the new complex structure will not match the usual canonical structure.
…and a mutation may change the conformation of the binding site so that the metabolite does not bind as effectively * …
It was at that point that I realised there was another possibility here. I will return to that in a moment.
So, this was like our metabolite colliding with a completely different protein, but one to which it could bind, before it reached our target protein. There is a fit, but within the 'wrong' overall structure – teaching is (subjectively) understood, but in a completely idiosyncratic and non-canonical way:
…intended binding may not occur if the metabolite first comes into contact with another molecule with which it can bind to form a different complex…
It was when I was drawing out my mutated protein, such that binding was strained to distort the complex (like a student interpreting teaching through an alternative understanding of the right topic, so the meaning of teaching gets distorted) that I realised a mutation could also lead to the protein lacking a viable binding site at all.
In this case the protein is present, but there was no way to bind the metabolite with it to form a complex. The learner has prior learning of the topic, but it is not possible to link the new information presented in teaching with it, as it would simply not fit with the learners' alternative understanding of the topic (as when for many years it was assumed by chemists that no noble gas compounds could be made because the inert gases had inherently stable electronic configurations which could not be disrupted by chemical processes).
So here the 'cause' of the lack of complex formation (a mutated protein / an alternative conceptual framework) could lead to two different outcomes – new information being distorted to fit in the alternative structure (like a protein with a slightly altered binding site) or new information not being linked with the prior topic learning at all (akin to a mutation meaning a protein had no viable binding site for forming a complex with the metabolite).
…* and I realised that a mutated protein may have no functioning binding site (rather than just a slightly distorted one) which leads to a different outcome.
So, consideration of my analogy brought home to me that the presence of an alternative conception may have different impacts depending on the extent of the differences between the students' thinking and the canonical scientific account.
Two types of 'mutated' prior learning?
What might these two possibilities, these different extents of mutated conceptions, mean in practice?
Consider a learner who is taught that 'plants do not need to be given food as they can manufacture their own food by photosynthesis'. If the learner has a notion of plants that includes fungi such as mushrooms and toadstools then the new information can 'bind' to the existing conceptual structure, but the learning will be 'strained' in the sense that the intended meaning is distorted (because the learner now thinks mushrooms and toadstool photosynthesise). This was the kind of example I had had in mind as a grounded learning impediment caused by a prior alternative conception.
By contrast, a deficiency learning impediment had reflected the absence of prerequisite learning needed to make sense of teaching (such as teaching that the bonds in methane are formed by the overlap of sp3 hybrid orbitals with the hydrogen 1s atomic orbitals to a student who had not previously been introduced to atomic orbitals).
However, the absence of prerequisite knowledge need not be due to having missed prior teaching, but could instead be having formed alternative conceptions so that the topic is represented in the learner's conceptual structure, but in a distorted ('mutated') version.
Consider the example of a teacher explaining properties of substances in terms of quanticle (nanoscopic particle) models. The teacher may explain that ionic salts tend to have high melting temperatures because the solids comprise of a lattice of strongly bonded ions which therefore takes a good deal of energy to disrupt.
A very common alternative conception of ionic bonding is based on the (false) idea that ionic bonds are formed by electron transfer from a metal atom to a non-metal atom. Often when a student acquires this alternative conception they understand the ionic solid to be composed of small units held together by ionic bonds (e.g., Na+-Cl–), but held to each other by weaker forces. For a student holding this alternative conceptual framework ionic bonds are not easily disrupted by heating an ionic solid, but the weaker forces between the bonded units will easily be disrupted so that melting will occur. The student assumes the small units (such as NaCl ion pairs) are like molecules (or actually are molecules) that continue to exist in the liquid phase when a solid like ice melts.
This learner had existing prior learning of the ionic bonding concept, but because this was not canonical, but involved alternative conceptions, the new information did not fit with the prior learning (it could not 'bind' with the 'mutated' conceptual structure) so the intended learning did not occur – a kind of deficiency learning impediment.
So, a deficiency learning impediment is due to a lack of existing conceptual learning that the new information can bind to – but this may be either because there is no prior learning on the topic, or because alternative conceptions of aspects of the topic mean the conceptual structure has the wrong 'conformation' to be perceived as relating to the new information presented in teaching.
It is just a model
The model of kinds of learning impediments is just that – a model of conceptual learning. It is one that I found helpful in my own work, especially when researching student thinking. I hope it may offer some insights to others, including teachers. Any value it has is in informing our thinking about learning and the teaching that can promote it. The analogy discussed above is just a(nother) kind of model of that model – a teaching analogy to introduce an abstract idea
Here, I wanted to just share how I found my own use of the analogy as a teaching aid helped develop my own thinking about the target domain of student learning. Analogies are just models, but like all models they can be useful thinking tools as long as we remember that they only somewhat resemble, and are not the same as, the targets they are compared with.
