Many undergraduates seem to think molecules like to hang around rather than moving on
Keith S. Taber
A representation of a small part of a layer of molecules in a solid substance – with one molecule highlighted by colour. If the solid were melted, and then refrozen, where would the highlighted molecule be?
If you are a science teacher: what would your students think?
In this article I offer my own version (actually two versions, see below) of a question I saw used in a published study (Smith & Villarreal, 2015a). As I no longer have any students, I cannot easily try this out, but perhaps a reader who is currently teaching science might be tempted to see what their pupils or students might think? (If you do, I would apreciate hearing about what you find!)
The two versions of the question can be downloaded from the links below.
The question could be given to individual learners, or as the basis of small group discussion, or perhaps just projected onto the screen for a 'show of hands' for each response option. (Exploring student thinking to detect misconceptions is known as diagnostic assessment.)
Alternative conceptions abound
I am very familiar with the extensive evidence which shows that is very common for learners, at all levels, and in any topic, to hold alternative conceptions ('misconceptions') at odds with canonical science and the target knowledge set out in the science curriculum. So, I am seldom surprised when I read about a study which reports finding learners demonstrating such conceptions.
Yet one study I read which reported learners commonly holding an alternative conception did surprise me. I would have not been surprised if the respondents had been secondary levels students, and a minority of them had demonstrated this particular conception, but I would not have expected how the study found a high incidence of the alternative conception among undergraduates studying chemistry.
The research asked about what happens when a solid is either dissolved, or melted, and then returns to the solid state. It used an instrument that presented a figure representing the particles in a small section of a solid, with one particle marked out, and asked the learners to draw the equivalent images after the solid had either dissolved and then been recrystallised, or melted and then been refrozen.
I an going to limit myself to the easier context (melt, then freeze – no solvent molecules involved). According to the researchers, the results suggested that a large proportion of the undergraduates indicated that the atom that had been marked out would be found in the same position in the solid at the end of the process: the exact proportion shifted in two versions of the study (65%, 50%) but a very rough gloss was that at least half of the learners located the marked particle back at its original point.
"These results indicated that a large proportion of the students viewed the [marked] molecule as being near to the same position after melting as it was before melting, and being in the position it was originally in after the liquid froze back to the solid."
Smith & Villarreal, 2015a: 277-278
Perhaps this should not have surprised me – I have been told by very bright A level students that on homolytic bond fusion each atom would always get its own electrons back, and this seems something of a parallel notion.
Now there was some questioning of the methodology and instrument used here (Langbeheim, 2015; see also Smith & Villarreal, 2015b) – as there often is in educational research – but it seemed a substantial proportion of learners thought the solid would reform with particles in their original positions, and this suggests a rather limited understanding of the level of molecular motion in the dissolved or molten state. I would not have been so surprised if this work had been carried out with, say, twelve year olds – but such a high level of misconception among undergraduates did surprise me as it reflects a failure to imagine the nature of the molecular world, and that surely makes learning high level (e.g., degree level) chemistry very difficult.
Now there are serious challenges in representing the nanoscale (thus the questioning of the representations used in the study) simply because molecules, ions, electron, atoms – are not the kinds of things we can draw realistically – they are fuzzy objects with no surfaces that somewhat blend into their neighbours. This raises a possible defence for students in such studies
'yes, your honour, I did show the particle as having returned to the same position, but as the focal figure had been drawn unrealistically as a set of circles I did not think authenticity was being asked for!'
It seems unlikely any learner really did think that – and the researchers did ask learners about their reasoning. The most common type of explanations were (Smith & Villarreal, 2015a: 278):
In the molten state: The molecule doesn't move far from its original position
After resolidification: The molecule ends up near where it was positioned in the liquid
Representing quanticles
Molecules, ions, atoms are 'quantum objects' which do not have the properties of familiar macroscopic objects. The nanoscopic particles in a lattice or liquid are not like the particles in table salt (grains) or sugar (granules) which each have a definite volume and surface, and which cannot be made to overlap their neighbours.
The following is my representation of a section of a layer of molecules in a solid substance. I have shown them round as that is simpler. Most molecules are not round (but 'molecules' of, say, neon or argon, are.) I have tried to show them as being fuzzy rather than as if ball-bearings with definite surfaces as the 'substance' of atoms, ions and molecules is largely electric fields and electron 'clouds' (a rather appropriate metaphor) rather than anything 'solid'. (And, of course, the word solid loses its meaning for a single molecule. We might, figuratively, suggest the atom is like a tiny liquid drop surrounded by an immense volume of gas – but it is probably best to avoid using such comparisons with learners becasue of the potential for them taking the terms literally.)
Should the molecules be touching in the solid? That is a problematic question as how do we decide whether things are touching when the things concerned do not have distinct surfaces but rather fade away to infinity? (If the gas giants Jupiter and Saturn were to ever come together, how would we decide at what point they had actually physically collided?)
Often in science teaching we cheat and show molecules touching in solids when teaching about the differences between condensed and gaseous states; but then hope students have forgotten this by the time we want to teach about thermal expansion of solids.
My diagram shows a layer of the regular crystal structure, so if you think my 'molecules' should touch then you can imagine that they would once the adjacent layers were drawn in.
The image I have used might suggest too much space between molecules…
…adding another layer might help give the appearance of close packing, but if a different colour is used this may suggest some physical difference…
yet making both layers the same colour makes the figure more dificult to interpret.
It is a problem of scale
The real issue for the novice learner here is one of scale. The scale of atoms is far beyond our ready grasp. My figure shows a much more extended section of material than that in the original study – but still, a tiny, tiny, tiny fraction of a solid we could readily see and manipulate. If the solid substance melted, then (e.g., around room temperature) we would expect molecular speeds of the order of hundreds of metres per second. In the gas phase that might be somewhat reflected in how far some molecules get (but diffusion is still much slowed by collisions), but in a condensed phase, so in a liquid, the molecules are not going to get very far at all before colliding with a 'neighbour' and being deflected off course.
The so-called 'random walk' of any molecule in a liquid will reflect mean speeds orders of magnitude less than the hundreds of metres per second instantaneous speed (as it is constantly being shifted to a new direction, and is just as likely to be sent back in the direction it originated).
But then, given the size of the sample represented, the distance from one end of the image to the other is of the order of maybe 0.000 000 001 metres. If a molecule with an instantaneous speed of hundreds of metres per second only has to travel of the order of perhaps 0.000 000 000 1m before colliding with the next molecule, it is going to have an awful lot of collisions each second – many billions. So, a molecule bumping around at say 300 m/s would not take very long to move 0.000 000 001 m (and so off the region of lattice shown in my figure) even with all those restrictive collisions!
Two versions of the diagnostic question for use in class
Even if the solid melts and is a liquid for only a few minutes (that is, a few hundred seconds), and even if we have placed the original solid in a tightly constricting container such that the liquid does not change overall shape, what are the chances of the molecule ending up in the same lattice position? Or even being in the frame when we represent such a small section of the lattice?
If we are only representing one layer of molecules, then what are the chances of the molecule even ending up in the same layer (it is likely to have moved 'up'/'down' just as much as laterally along the plane represented whilst in the liquid state).
Each of the options (in both versions of the question) are possible outcomes.
Given that the section of the latice shown is so limited, all the positions shown are pretty much local to the starting point, so I would argue the molecule could almost equally likely end up in any of the lattice positions in the figure (so: A, C and D are, in effect, equally likely – as would be any other lattice position you selected from the image).
What about Option B?
Option B reflects all the possibilities where the molecule ends up outside the small section of lattice layer illustrated, including all the options where it has moved to a different layer. There will be billions and billions of these options, including, at least, many thousands of options close enough for the molecule to have easily moved there in the number of 'random walk' steps feasible in the time scale.
So, the answer to the question of which option is most likely (in either version of the question) is easy – option B is by farmost likely.
But I wonder if most students who have been taught about particle models and states of matter would agree with me? If Smith and Villarreal's undergraduate sample is anything to go by, then I guess not.
Work cited:
Smith, K. C., & Villarreal, S. (2015a). Using animations in identifying general chemistry students' misconceptions and evaluating their knowledge transfer relating to particle position in physical changes [10.1039/C4RP00229F]. Chemistry Education Research and Practice, 16(2), 273-282. https://doi.org/10.1039/C4RP00229F
Langbeheim, E. (2015). Reinterpretation of students' ideas when reasoning about particle model illustrations. A Response to "Using Animations in Identifying General Chemistry Students' Misconceptions and Evaluating their Knowledge Transfer Relating to Particle Position in Physical Changes" [10.1039/C5RP00076A]. Chemistry Education Research and Practice, 16(3), 697-700. https://doi.org/10.1039/C5RP00076A
Smith, K. C., & Villarreal, S. (2015b). A Reply to "Reinterpretation of Students' Ideas when Reasoning about Particle Model Illustrations. A Response to 'Using Animations in Identifying General Chemistry Students' Misconceptions and Evaluating their Knowledge Transfer Relating to Particle Position in Physical Changes' by Smith & Villarreal (2015)" [10.1039/C5RP00095E]. Chemistry Education Research and Practice, 16, 701-703. https://doi.org/10.1039/C5RP00095E
Alternative conceptions underpin some, but not all, learning difficulties
Keith S. Taber
I recently wrote here about a paper published in a research journal which used a story about the romance between two electrons, Romeo and Juliet, as a context for asking learners to build models of the atom. (I thought the approach was creative, but I found it quite dificult to decode some aspects of the story in terms of the science).
But something else I noticed about that study (Aquilina et al., 2024) was that the authors listed a number of 'misconceptions' that their teaching approach was meant to address (see the Table reproduced above). These were:
Students, after studying planetary and Bohr's atomic models, cannot move beyond them easily.
Students rarely reflect on and/or understand the need for the development of new atomic models.
Students find it difficult to associate spectral lines with transitions between energy levels.
Students do not describe photon emission processes properly.
Students do not clearly understand the concept of an orbital.
Students find it difficult to understand atomic quantum-mechanical models.
But none of these actually seemed to be misconceptions.
To be clear, I think
all of these points are pertinent to the research; and they reflect
challenges to the teacher, and
learning difficulties experienced by many learners.
But they are not misconceptions.
What is a misconception?
There is a very large literature reporting student misconceptions, or alternative conceptions, in science subjects.1 A misconception, or alternative conception, is a conception that is judged to be inconsistent with the scientific account (or the version of the scientific account presented in the curriculum). The points listed in Aquilina and colleagues' table are not conceptions, so cannot be alternative conceptions – just as a postbox cannot be a red car, because it is not a car; and nor can Boyle's law be a refuted theory, because it is not a theory; and a mushroom cannot be a leafless plant, because it is fungi not plant.
So, what is a conception?
We might understand a conception to be one facet of a concept (Taber, 2019). Consider a student has some ideas about atoms. We might consider the learner's concept of the atom to be the collection of all those ideas about atoms. Imagine a learner thinks:
atoms are very small
an atom contains a nucleus
atoms contain electrons arranged in shells
there are many different types of atoms
gold atoms are gold coloured
everything is made of atoms 2
an exploding atom can destroy a city
If this was the full extent of their ideas about atoms, we might collectively see this list as comprising their atom concept. We could represent it by drawing a concept map showing how the learner sees 'atom' to be linked to other concepts such as 'nucleus', 'electron', etc.
But we might consider each one of these separate statements to be a conception.
Our conceptions vary across a number of dimensions (after Figure 2.3 in Taber, 2014)
There are complicatons:
A person may have (implicit / tacit) 'conceptions' that they could not easily put into words to express as statements. (A researcher might elicit what a learner is thinking and represent it as a sentence, but for the learner it may be more a vague intuition that they only put in words in response to the researcher's questions.)
A person may also show different levels of commitments to conceptions – perhaps our hypothetical learner is pretty certain that atoms are very small, but only has a hunch that gold atoms are gold coloured. Perhaps the learner was told by a friend that an atom bomb that is powerful enough to destroy a city is based on exploding a single atom at its centre – and our learner remembers this, but is actually very sceptical.
We usally say a learner has an alternative conception when they hold a conception which is inconsistent with (so alternative to) the scientific account. A great many such alternative conceptions have been elicited in research that explores people's thinking about science. Much of this work has been undertaken with science learners, but some simply with people in the general population (when alternative conceptions may be termed as 'folk science' or 'urban myths'). Here are just a few of the examples discussed elewhere on this site:
These are 'alternative' because they are contrary to the scientific account, and they are significant to science teachers because they are contrary to the target knowledge the teacher is expected to teach to students.
One reason to perhaps prefer the term 'alternative conception' to 'misconceptions' is that the latter term may seem to imply the outcome of misunderstanding teaching. Alternative conceptions certainly can be linked to misunderstanding teaching, but often this occurs because the learner already has an intuitive idea that is contrary to the science, and this leads to them misinterpreting teaching. But consider this example:
an atom of an element in the first period has a full shell with two eletrons, all other atoms would need to have eight electrons in the outer shell for it to be a full shell
This is an alternative conception that learners sometimes do hold, whereas eight electorns only counts as a full shell in period 2 (Li, Be, B, C, N, O, F, Ne) and not for any of the other elements. So, a chloride atom (electronic configuration 2.8.7) does not have a full outer shell when it joins with an electron to become a chloride ion (2.8.8).
But I have seen school textbooks aimed at secondary levels learners (c.14-16 year old students) that actually state quite clearly that all atoms, apart from H and He have a full outer shell with eight electrons. If a learner had read that in the textbook issued by the school, and so believes it to be so, then they have not misconceived what they read – they have accurately understood the intended meaning. But it is still an alternative conception ('misconception').
Learning blocks and misconceptions
So, something cannot be an alternative conception (misconception), unless it is both a conception, and counter to the scientific account. But there are other reasons a learner may struggle to understand the science in the curriculum.
A learner may lack specifc prerequisite background knowldge needed to make sense of a new idea; or the learner may not appreciate that cetain prior knowledge is meant to be applied in understanding the new material. Learners may indeed misinterpet teaching due to an existing alternative conception, but they may also sometimes make an unhelpful association with unrelated prior learning. (That is, they interpet teaching in terms of some prior learning that they think is related, but which from the scientific perspective is not relevant.) Sometimes that may relate to how scientific terms may be understood through the learner's language resources (such as assuming a 'neturalisation' reaction will always lead to a neutral product becasue that's exactly what a reasonable person might expect 'neutralisation' to mean!) or it may relate to not appreciating the limitations of a teacher's model, or to how an analogy or metaphor (e.g., electron shell) is intended to be figurative, not literal.
Learners may not always understand teaching as intended
So, alternative conceptions are indeed very relevant to the challenge of teaching science, but not all learning difficulties are due to alternative conceptions; and certainly not all learning dificulties should be labelled as 'misconceptions'.
Beyond misconceptions
So, what about Aquilina and colleagues' list of supposed 'misconceptions'?
Students, after studying planetary and Bohr's atomic models, cannot move beyond them easily.
Students rarely reflect on and/or understand the need for the development of new atomic models.
Students find it difficult to associate spectral lines with transitions between energy levels.
Students do not describe photon emission processes properly.
Students do not clearly understand the concept of an orbital.
Students find it difficult to understand atomic quantum-mechanical models.
There are a number of well-recognised issues here. Two in particular stand-out.
The unfamiliar abstract
For one thing the subject matter is unfamiliar and abstract. People can only understand teaching if they can link it to existing experience or prior learning. Teachers have to find ways 'to make the unfamiliar familiar'. (This is why Aquilina and colleagues devised a narrative based on a tragic love story that they expected the students to be familiar with.)
But learning about the abstract in terms of the familiar only moves a learner so far when the familiar is only a little like the target. Learners know about shells, so can imagine electrons in shells – but electron shells are not really like more familiar shells (such as those that protect snails and cockles or bird's eggs). Learners can imagine electrons spinning like spinning topics, but electron spin is not like that – the electron does not spin.
The behaviour of quanticles, quantum objects, is quite unlike the behaviour of familiar objects. An orbital is not really an object at all, but more a description of the solution of a mathematical equation – those diagrams showing the different atomic or molecular orbitals are a bit like the map of the London underground: schematic representations that are useful for some purposes, but not realistic images of the orbital/rail line.
Acquiring model nous (epistemologial sophistication)
The second issue relates to epistemological niavety, which comes from not appreciating the subtle nature of science. If we teach students that an atom is like THIS (say, electrons orbitting a central nucleus like planets orbiting the sun), why shoud we then be surprised that students think that is what an atom is like – and so then struggle to understand why we are now teaching them the atom is quite different from this? The defence that we did point out this was a model is only convincing if we are sure the students understood what a scientific model is.
We might describe thinking that electrons in atoms have definite trajectories as being a 'misconception' – but if we have taught such a model then the learner's real misconception is in thinking that such a model is meant to be a realistic representation. If we never taught them that the model was something other than a scale replica of an atom, then this is a 'pedagogic learning impediment'. That is, the student is only guilty of learning what they have been taught!
Perhaps more attention to this aspect of the nature of science throughout school science might avoid this problem. Imagine that from a young age learners had regularly been asked in their science lessons to:
devise different models and representations of various scientific phenomena
identify the strength and limitations of different models (both those produced by learners, and mulitpile representations presented by the teacher)
discuss why having several different (imperfect) models might sometimes be useful
be asked to choose between alternative models/representations for different specified purposes
In contexts where science has tended to be taught as though it offers a single, realistic account of phenomena, then we should not be surprised
that students do not see the need to move beyond the models they have been taught (they consider them as more like scale replicas than theoretical models)
nor indeed when they complain they have put a lot of effort into learning models they now feel they are being taught were wrong all along!
Learners' alternative conceptions are a major impediment to learning school and college science. However, learning of abstract ideas requires learners to make sense of teaching in terms of the interpetative resources they have available – and that is often challenging enough even when they have no existing alternative conceptions in a topic.
Aquilina, G.; Dello Iacono, U.; Gabelli, L.; Picariello, L.; Scettri, G.; Termini, G. "Romeo and Juliet: A Love out of the Shell": Using Storytelling to Address Students' Misconceptions and Promote Modeling Competencies in Science. Education Sciences, 2024, 14, 239. https://doi.org/10.3390/educsci14030239
Taber, K. S. (2014). Student Thinking and Learning in Science: Perspectives on the nature and development of learners' ideas. New York: Routledge.
Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Cambridge: Royal Society of Chemistry.
Notes:
1 There are a number of other related terms used in the literature, such as intuitive theories and preconceptions. Sometimes these different terms refect subtle distinctions (so preconceptions refers to alternative conceptions a learner has prior to being taught anything about a topic). But, in practice, there is no real consisitency in how various terms are used across different authors.
I try to reserve the term alternative conceptual framework for more large scale conceptual structures than discrete alternative conceptions. (But again, the terms are sometimes used interchangeably) So, for example, the 'octet' framework is a network of related conceptions built around the core alternative conception that chemical change is driven by atoms needing full electron sells or octets of electrons:
2 A teacher might want to ask students what they means by their words. If a student suggests they believe that everythings is made of atoms, or everything is made from atoms, then this may be a canonical understanding, or an alternative conception:
motto
is a short-hand way of suggesting
alternative conception
everythings is made of atoms
all material substances found under normal conditions can be shown to contain atomic cores surrounded by electrons
if we could examine all materials we would find they are comprised of lots of discrete atoms just stuck together
everything is made from atoms
we can envisage that any substance could be built up by chemiclly joining together a certain number of atoms of various elements – all molecules and other structures can be imagined as being built up from atoms
chemical reactions produce different substances by starting with lots of atoms of the relevant elements
An opinion piece in Education in Chemistry by Kristy Turner recently highlighted the potential bias that may lead to scholars being more likely to access, read and cite research from some parts of the world than others. This was actually an issue I was very aware of when a journal editor, as an international journal should aim to reflect research globally, but needs to apply common quality criteria.
This means that those working in contexts where there are no traditions of educational research, and limited resources to develop capacity, are at a disadvantage. I could think of one country where the journal received regular contributions, but which were almost always rejected (perhaps, always rejected?), as they simply did not amount to substantive accounts of research. These included well-intentioned, if sometimes quite convoluted, suggestions for mnemonic schemes to teach abstract conceptual subject matter, which offered absolutely no evidence that the proposed approach had ever been evaluated (if, indeed, ever applied). I was aware that any simple calculation of success rates in the journal would show that submissions from this particular national context had no chance of publication, and that few indeed ever got as far as referees 1. This might look like prejudice, even if it reflected application of the same quality criteria to all submissions. 2
On the other hand, the situation is slowly shifting. An excellent example is Turkey, which transformed from being a virtual non-participant in science education research publication to one of the most productive national sources of research published in the top journals, in just a couple of decades. I am aware of several other countries that are, if more slowly, supporting similar development in science education. So, the situation is complex: but Turner is absolutely right that we need to also be aware of a possible mind-set that assumes useful, quality research in science education will only be going on in a limited number of national contexts.
Being classified by the colour of my skin
But what really made me reflect on the piece was was not this important point, but that I was name-checked at the start of the article, along with a number of other educational research scholars, before Turner asked:
"What do these names have in common?
To start with they are all men and all White. More significantly, they all worked in the West (although some had collaborations further afield). This means that much of the education research we consume is produced from a Western perspective."
Turner, 2023
I am not sure I have ever seen myself called out in this public way as being "White", and I was not sure I was comfortable with being labelled in this way. For me, this was a mild discomfort – the kind that usefully leads one to reflect. By contrast, many people in this world experience being referred to by colour labels every day of their lives.
I readily identify as English, British and European, as simply a matter of fact: so, I suppose, 'Western' – guilty as charged. I have no qualms about being publicly labelled as a man. (Though I had no problem with being called 'Miss' by new secondary school students just moving up from primary schools where their class teacher had been 'Miss'. The pupils tended to be more embarrassed than me on these occasions – as was the tutee who once inadvertently called me 'Dad'. Yes, Tamsin, I still remember that.)
When I went to school, the world (at least as it was usually talked about) seemed simple in that regard. Humans came in two types – males and females. In my class in school there were boys and girls, and there was absolutely no ambiguity about this, and the difference was clearly marked: the boys wore shorts, the girls skirts or dresses. When I got to secondary school I studied metalwork and woodwork and technical drawing, whilst the girls studied their own subjects such as cookery. (Yes, I am that old.) Science dichotomised people into these classes of males and females (this was strictly known to be a simplification, but I do not recall any mention of other possibilities when I was a child), and there was a widely assumed perfect correlation with gender.
Of course, we now know this is utterly simplistic, and if such a regimented approach is imposed on people it is a burden that does not reflect the range of ways that people themselves experience their lives. It is now very common for people to attach their preferred pronouns to their web-pages and emails footers, and we appreciate that people have a right to self-identify in gender terms, and should not be assigned such an identify from the outside.
Original image by Krzysztof Niewolny from Pixabay
Should what is good for the goose also be good for the gander?
So, if we respect people's right to claim their own gender identity, what gives us the right to assign them to 'colour' categories? These categories were historically linked to what many scientists considered distinct varieties of human being – the different 'races'. That is, just as scientists might have recognised different varieties of a species, say different breeds of sheep, so there was considered to be a substantive and biologically justifiable basis for classifying people as members of different 'races'.
Those classifications were also not just seen as categorical, but often as ordinal – there were not only considered to be different races, but some of them were widely thought of (*) as more advanced, more civilised, perhaps even more evolved, than others; and it sometimes followed to many people that members of some races were of more inherent worth than others. (* At least, this was a common stance among people who self-identified as White!)
As is well known, this attitude led to many terrible events, and such bizarre notions as long-inhabited lands being 'discovered' by newcomers who therefore felt entitled to take possession of them: perhaps because they did not consider the inhabitants worthy of land and resource ownership; or perhaps because often the indigenous population took an attitude to the land and biota that it was not open to their ownership, but rather was sacred and deserving of being seen as in a form of relationship, rather than just being a source for exploitation. (That is, in many senses, the supposed 'more primitive' people had a more sophisticated and ecologically viable Worldview than those making the comparisons and seeing themselves as 'more civilised'.) That was one historical form of the 'Western perspective' that Tuner rightly warns about. 3
Science progresses: but not everyone keeps up
Science has moved on. We now know that, from a scientific perspective, there is only one human race. We all descend from early human ancestors that lived in Africa – so, for example, all of us in Britain are, if not ourselves migrants, ultimately the descendants of African migrants.
There are no strong categorical differences that allow us to form clear-cut classes of people (such as we can nearly dichotomise sex, even if we now realise that does not correlate to gender in a simple, direct way). Certainly, there are differences in populations that have long lived in different parts of the world: some groups are more likely to be lactose intolerant; more likely to suffer from, or be resistant to, specific diseases, and so forth. But these are statistical differences, not absolute ones.
An analogy for categorising people into 'races' based on physical characteristics (original image by Mote Oo Education from Pixabay)
To divide people into racial groups on that kind of basis makes as much sense as dichotomising adult people into males and females purely on height (i.e., the tallest 50% are male, by definition) simply because there is a statistical correlation between biological sex and adult height. Throughout human history, there has been social and genetic interchange between populations, and that is now more so than ever. We all have a mix of genes from a diverse range of ancestors – indeed most of us have few percent of genes that are considered Neanderthal. 4 So being 'White' is not simply a matter of genetics: any notion of a pure European genome is simply fantasy, akin to the deluded Nazi fantasies of Aryan blood lines. 5
Race is not a biological classification. Race is a socialsystem of categorising people, not a scientific system. There are different races in the world only in a similar sense to how there are different styles of art or architecture in the world, or different modes of fashion (or styles of music, or genres of literature): because people have constructed such a system and imbued certain perceived differences with significance. But, there are not races in the world 'naturally' in the sense that there are different elements or different minerals out there for scientists to find. 6
The idea of several distinct human races can be seen as a historical scientific concept that was once given serious credence (just like phlogiston, or the luminiferous æther), but today should be seen as an alternative conception – a bit of folk-science that is actually a misconception.
So, if I am seen as White, this is because I have certain physical characteristics that others perceive as being 'White' (i.e., physiognomy). Presumably skin colour is a primary factor, although I certainly do not have white skin (I have never seen anyone who actually looks white or black, and suspect this choice of labels is in part a reflection of the historical associations of these colours 7). I am basically a pink colour, although at certain times of year I go somewhat orange. I am not being flippant here – I am obviously of pale skin tone as would be associated with someone of European descent. But, again, we know that skin tone does not simply divide into a few clear categories: there is a whole spectrum out there, and most of us do not have entirely even pigmentation over all parts of the body, and/or are subject to some variation depending on environmental factors (and in England the average potential exposure to the Sun's rays in June is VERY different to in December!)
Now, I am not suggesting there might not be times when pointing out the colour of someone's skin might be useful – it might be very relevant in giving a description of a missing child or a mugger. But, Turner was not calling me White to help you recognise me, but to label me as someone associated with a 'Western' perspective. This of course is not a perfect correlation either. (I suspect that Rishi Sunak and Barack Obama would be widely considered to have Western perspectives).
'I hate the White man'
The musician Roy Harper wrote a song called 'I hate the white man' which appeared on his 1970 album 'Flat Baroque and Berserk'. He sings it live with real venom. When I first heard this song, it seemed strange to me, as here was a white man [sic, my label] singing how he hated the White man. It was heartfelt, but it seemed ironic. It did not occur to me that I was just assuming Roy was White because he looked white to me. (He is 'obviously' white, just as I, apparently, obviously am – that is, his skin tone is pinkish.) I never entertained another possibility: the notion that he should have the right not to identify with the people who's crimes he was singing about; that is, not to identify as a White man.
So, should I be able to opt out of being put in an unscientific, racial category? Can I decline being White, and simply be a global citizen, a member of the human race, and so deserving the same level of respect and the same human rights as any other?
A dilemma
Of course it is not that easy. It is all very well someone like me refusing to self-identify with a racial label: there is still much discrimination and even targeted violence in many part of the world against people on racial grounds, and that would not be stopped by any personal self-identification of the victims. It is the perceptions of the abusers that matter in such situations, not how those on the receiving end see themselves. The Nazi's decided for themselves who was Jewish and so who deserved to be, say, removed from academic posts, or even incarcerated and exterminated, without regard to, for example, the victim's professed religion or record of Christian Church attendance.
Moreover, even if there are no strong genetic grounds to classify humans into a small number of 'races', the science of epigenetics is starting to reveal the cross-generational effects of extreme life-experiences (Meloni, 2019) such as slavery. The descendants of oppressed and impoverished people will continue to suffer relative to others for several generations. There may be no moral basis for asking children to pay for the 'sins of the fathers', but children of heavily sinned-against parents will still be at a disadvantage in life. That is not all about 'race': it might be about class, or the effects of war, but often racial identity (something with real effects, even if no scientific justification) can certainly be a factor.
If we do not identify with ethnic groups, then this makes monitoring of bias and discrimination difficult. How does an organisation know it is being equitable in relation to ethnic diversity, if no one chooses to self-identify with the traditionally majority, and/or privileged, groupings?
I think there is a genuine conundrum here. I look forward to the day when no rational person would see physiognomy as a useful basis for unscientifically classifying human beings, and, even if I am unlikely to live that long, hope we continue to move in that direction. But I understand why minority and oppressed groups find solidarity in such identification, and I appreciate the need for monitoring progress towards a fairer and more equitable society. So, Kristy, I fully understand why you call me 'White', even if I feel a little uneasy being labelled in that way.
Work cited:
Meloni, M. (2019). Impressionable Biologies: From the archaeology of plasticity to the sociology of epigenetics. Routledge.
Szöllösi-Janze, M. (2001). National Socialism and the sciences: reflections, conclusions and historical perspectives. In M. Szöllösi-Janze (Ed.), Science in the Third Reich (pp. 1-34). Berg.
1 Submissions to a research journal normally undergo editorial screening, so that (unpaid, expert) referees are not asked to spend time evaluating material in peer review that is out of scope for the journal or clearly inadequate (e.g., an empirical study lacking a methodology section).
2 I did highlight this issue at the journals' editorial board. The journal itself could do little about solving the problem, but the wider community might find ways to support development of research capacity in contexts where science educators aspire to be publishing work in international research journals.
3 Without in any sense wishing to undermine the terrible consequences that followed from widely held perceptions of racial differences, this can be seen as part of the wider commonplace phenomenon of categorising humans into various groupings in ways that are then used to justify treating some people as less worthy of respect and rights as others – for example the torture and judicial murder of Catholics/Protestants by Protestants/Catholics in parts of Europe when, sometimes, different members of the same nuclear family were classified into different groups.
4 It is sometimes said that on average a person has about 2% of Neanderthal DNA. Given that all the biota on earth is considered to ultimately have a common descent it is of course not surprising that human beings share some genes with, say, chimpanzees, and for that matter, bananas. However, it is not considered humans have chimpanzee ancestors (or banana ancestors, of course) but rather the two species evolved from a common ancestor population.
The particular interest in Neanderthal genes (and genes from Denisovans) is that it is considered that extant human populations carry genes acquired from Neanderthals when the two different populations co-existed, not from some precursor species they both evolved from. Whilst this is still an area of active research, the findings are widely interpreted to suggests that humans sometimes interbred with Neanderthals.
5 The Nazis thought that the German Volk descended from a distinct, discrete race, the Aryans – and set up scientific research projects to explore and develop the idea. Some of the ideas involved seem incredible:
"…Himmler rejected the Darwinist theory of evolution for the Aryans, presenting instead phantasies, according to which their earthy existence was derived from living shoots conserved in the ice of outer space…"
Szöllösi-Janze, 2001
6 Failure to appreciate this leads to confused questions such as whether discrimination against Jews should be considered racism. From a scientific perspective there are no races, so ipso facto the Jews are not a race. However, this is besides the point: if Jewish people are discriminated against, abused, attacked etc., either because of their religion, or because they are perceived as being members of an identifiable social ('ethnic') group, then this is clearly wrong and to be condemned, regardless of the label used.
If a legal system puts a particular weight on criminal offences that are motivated by racism (so, for example, punishments for those convicted have a premium), then what counts as a race for those purposes needs to be defined within that (social, i.e., legal) system, as natural science can have no role in determining social groupings that have no scientific basis.
7 This was lampooned in 'Star Trek: Enterprise', where Andorian Thy'lek Shran adopts the nickname 'pink skin' for Enterprise's Captain Archer.
From the Paramount Network Television series Star Trek: Enterprise
I often enjoy reading popular accounts of science topics, but sometimes one comes across statements that are vague or dubious or confusing – or simply wrong. Some of this reflects a basic challenge that authors of popular science share with science teachers and other science communicators: scientific ideas are often complex, subtle and abstract. Doing them justice requires detailed text and technical terminology. Understanding them often depends upon already having a good grasp of underpinning concepts. That is fine in a formal report for other scientists, but is not of any value to a non-specialist audience.
So, the author has to simplify, and perhaps round off some of the irregular detail; and to find ways to engage readers by using language and examples that will make sense to them. That is, finding ways to 'make the unfamiliar familiar'.
I am sure that often the passages in popular science books that I as a scientist1 get grumpy about are well motivated, and, whilst strictly inaccurate, reflect a compromise between getting the science perfect and making it accessible and engaging for the wider readership. Sometimes, however, one does get the impression that the author has not fully grasped the science they are writing about.
"Lucy Jane Santos is the Executive Secretary of the British Society for the History of Science…"
Public engagement with radium
I very much enjoyed reading a book, 'Half lives', by the historian of science Lucy Jane Santos, about how in the decades after its discovery by Pierre and Marie Curie, radium was the subject of wide public interest and engagement. One of the intriguing observations about this newly discovered element was that it appeared to glow in the dark. We now know that actually the glow comes from nitrogen in the air, as radium is radioactive and emissions by radium 'excite' (into a higher energy state) nitrogen molecules, which then emit visible light as they return ('relax') to their 'ground' state. This production of light without heating (a phenomenon generally called luminescence), when it is due to exposure to radioactivity, is known as radioluminescence.
Today, many people are very wary of radioactivity – with good reason of course – but Santos describes how at one time radium was used (or at least claimed as an ingredient) in all kinds of patent medicines and spa treatments and cosmetics (and even golf balls). This was a fascinating (and sometimes shocking) story.
What substance(s) can you find in quinine?
I did find a few things to quibble over – although across a whole book it was, only, a few. However, one statement that immediately stood out as dodgy science was the claim that quinine contained phospor:
"Quinine contains phosphor, a substance that luminesces when exposed to certain wavelengths of light…"
Santos, 2020
This may seem an unremarkable statement to a lay person, but to a scientist this is nonsensical. Quinine is a chemical compound (of carbon, hydrogen, nitrogen and oxygen), that is – a single substance. A single substance cannot contain another substance – any more than say, a single year can contain other years. An impure sample of a substance will contain other substances (it is in effect a mixture of substances), but quinine itself is, by definition, just quinine.
Molecular structure of the chemical compound quinine (C20H24N2O2) – a pure sample of quinine would contain only (a great many copies of) this molecule.
Note – no phosphorus, and no rare earth metal atoms.
The term 'phosphor' refers to a luminescent material – one that will glow after it has been exposed to radiation (often this will be ultraviolet) or otherwise excited. The term is usually applied to solid materials, such as those used to produce an image in television and monitor screens.
The term derives by reference to the element phosphorus which is a luminescent substance that was accordingly itself given a name meaning 'light-bearing'. The term phosphorescent was used to describe substances that continue to glow for a time after irradiation with electromagnet radiation ceases. But it is now known that phosphorus itself is not phosphorescent, but rather its glow is due to chemiluminescence – there is a chemical reaction between the element and oxygen in the air which leads to light being emitted.
The widely used term phosphor, then, reflects an outdated, historical, description of a property of phosphorus; and does not mean that phosphors contain, or are compounds of, phosphorus. There is clearly some scope for confusion of terms here. 2
term
meaning
luminescence
the emission of light by a cold object (in contrast to incandescence)
– chemiluminescence
a form of luminescence due to a chemical reaction
– – bioluminescence
a form of chemiluminescence that occurs in living organisms
– electroluminescence
a form of luminescence produced by passing electrical current through some materials
– photoluminescence
a form of luminescence due to irradiation by electromagnetic radiation, such as ultraviolet
– – fluorescence
a type of photoluminescence that only occurs whilst the object is being excited (e.g., by exposure to ultraviolet)
– – phosphorescence
a type of photoluminescence that continues for some time after the object has been being excited (e.g., by exposure to ultraviolet)
– radioluminescence
a form of luminescence due to a material being exposed to ionising radiation (e.g., 𝛂 radiation)
– sonoluminescence
a form of luminescence due to a material being exposed to sound
phosphor
a material that exhibits luminescence
phosphorus
a chemical element that exhibits chemiluminescence (when exposed to air)
There is a range of terms relating to luminescence. Here are some of those terms.
Some central ideas about luminescence (represented on a concept map)
A traditional medicine
Quinine, a substance extracted from the bark of several species of Cinchona, has long been used for medicinal purposes (e.g., by the Quechua people of the Americas 3), as it is a mild antipyretic and analgesic. It is an example of a class of compounds produced by plants known as an alkaloids. Plant alkaloids are bitter, and it is thought their presence deters animals from eating the plant. We might say that Quechua pain medication is a bitter pill to swallow.
Modern science has often adopted and developed technologies that had long been part of the 'traditional ecological knowledge' of indigenous groups – such as making extracts from Cinchona bark to use as medicines.
Sadly, the original discovers and owners of such technologies have not always been properly recognised when such technologies have been acquired, transferred elsewhere, and reported. 3
(Image by GOKALP ISCAN from Pixabay)
Quinine is an ingredient of tonic water (and bitter lemon drink) added because of its bitter taste.
(Why deliberately make a drink bitter? Quinine has anti-malarial properties which made it a useful substance to add to drinks in parts of the world where malaria is endemic. People liked the effect!)
Quinine glows when exposed to ultraviolet light. It is luminescent. To be more specific, quinine is photoluminescent. (This is responsible for the notion that someone offered a gin and tonic at a disco should test it under the 'blacklights' to make sure they have not been given pure gin to drink. Although, I am slightly sceptical about whether the kind of people that drink 'G&T's go to the kind of dances that have ultraviolet lighting.)
"I do apologise, I think I might have just splashed a tiny droplet of my tonic water on you"
(Image by Victoria_Watercolor from Pixabay)
It is reasonable to describe quinine as a phosphor in the wider sense of the term – but it does not contain another phosphor substance, any more than, say, iron contains a metallic substance or sulphur contains a yellow substance or sucrose contains a sweet substance or copper a conducting substance. So, a more accurate formulation would have been
"Quinine [is a] phosphor, a substance that luminesces when exposed to certain wavelengths of light…"
or, perhaps better still, simply
"Quinine [is] a substance that luminesces when exposed to certain wavelengths of light…"
Ask the oracle
I was intrigued at why Lucy Jane Santos might have been confused about this, until I did a quick internet search. Then I found a range of sites that claimed that quinine contains phosphors – indeed, often, rare earths are specified.
The rare earths (another unfortunate historic choice of name, as it transpired that they are neither especially rare nor 'earths', i.e., oxides) are a group of metallic elements. They are not as well known as, say, iron, copper, zinc, aluminium or gold, but they have with a wide range of useful applications.
Scandium, the first of the 'rare earth' metals. Probably not what you want in your tonic water.
If something is repeated enough, does it become true?
Clearly there are not rare earths in quinine. So, the following quotes (from sites accessed on 7th March 2023) proffer misinformation.
"If you want to get a bit more scientific about it…. quinine contains rare earth compounds called phosphors. These are the substances which glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own colour, in this case glowing blue light."
This claim is odd, as the previous paragraph explained more canonically: "why does quinine absorb UV light (the invisible component of sunlight that produces sun tans and sunburns!)? It is due to the structure of the quinine molecule, which enables it to take in energy in the form of invisible UV light and immediately radiate some of that same energy in the form of visible blue light." Other compounds cannot be inside a molecule – so this more canonical explanation is not consistent with quinine containing other "substances" which were "rare earth compounds."
"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light."
The following extract appeared under the subheading "Why is quinine fluorescence?" That reflects a category error as quinine is a substance and fluorescence is a process (and fluorescent the property) – so, presumably this should have read why is quinine fluorescent?
Why Quinine Glows
Quinine contains rare earth compounds called phosphors. … Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light.
Tonic water glows and [sic] will fluoresce under UV rays because of quinine in it. Quinine is one of the most important alkaloids found in the cinchona bark, among many others. It has some rare earth compounds known as phosphors that glow when they hit certain wavelengths of the UV light. Phosphors in the quinine absorb the UV light and then reflect it or emit it again in the form of glowing blue light.
Perhaps the most bizarre example was a site, 'emaze' which offered to show me "How to create magic mud…in 17 easy steps"
Step 1 was
"wash your potatoes!!!!"
However, perhaps due to exclamation fatigue(!), this went in a different, if now familiar, direction with step 2:
"Quinine contains rare earth compounds called phosphors. These substances glow when they are hit with particular wavelengths of the EM spectrum, including UV light. Phosphors absorb UV light and then emit it in their own color [sic, colour]. Thus, the black light's UV radiation is absorbed by the phosphors in the quinine, and then emitted again in the form of glowing blue light"
https://app.emaze.com/@AORQCIII#/16
This text was then repeated as each of steps 3-14. (Sadly steps 15-17 seemed to have been missed or lost. Or, perhaps not so sadly if they were just further repeats.) The first screen suggests this presentation was "done by Dr. Meena & Maha" but if Dr. Meena & Maha really exist (if you do, I am sorry, the internet makes me very sceptical) and 'done this', it is not clear if they got bored with their task very quickly, or whether the server managed to corrupt a much more coherent presentation when it was uploaded to the site.
This 'emaze' presentation seems to want to emphasise how quinine contains rare earth compounds…
According to Google, the site 'Course Hero' suggested
"Phosphors, which are found in quinine, are rare earth compounds. These chemicals glow when they are struck with particular wavelengths of the EM spectrum, …"
but unfortunately (or perhaps fortunately given that snippet), the rest of the text seemed to be behind a pay-wall. This did not offer a strong incitement to pay for material on the site.
Toys coated with phosphorus?
Another website I came across was for a shop which claimed to be selling glow-in-the-dark objects that were made with phosoporus that needed to be illuminated to initiate a glow: a claim which seems not only scientifically incorrect (as mentioned above, phosphorus is not photoluminescent – it glows when in contact with air as it oxidises), and so unlikely; but, otherwise, dangerous and, surely, illegal.
During my search, I came across a website (grammarist.com) offering to explain the difference between the words phosphorous and phosphorus. It did not discuss rare earths, but informed readers that
"Phosphate: Noun that means an electrically charged particle. Phosphorus: Also a noun that means a mineral found in phosphate." …We've already established that phosphorus is the simple mineral found in the particle phosphate, but phosphor is something else altogether."
So, that's 'no', 'no', 'no', and…I think at least one more 'no'.
Phosphorus is a reactive element, and is not found in nature as a mineral. To a scientist, a mineral is a material found in nature – as a component of rocks. Unfortunately, in discussing diet, the term minerals is often associated with elements, such as, for example, phosphorus, iodine, potassium and iron that are necessary for good health. However, one would not eat the element iron, but rather some compound of it. (Foods naturally contain iron compounds). And trying to eat phosphorus, iodine or potassium (rather than compounds of them) would be very hazardous.
So, whilst a nutritional supplement might well contain some minerals in the composition, strictly they are there as compounds that will provide a source of biologically important elements, and they will be metabolised into other compounds of those elements. (Iron from iron compounds will, for example, be used in synthesising the haem incorporated into red blood cells.) Unfortunately, learners commonly have alternative conceptions ('misconceptions') about the difference between mixtures and compounds and assume a compound maintains the properties of its 'constituent' elements (Taber, 1996).
The grammarist.com entry helpfully warned us that phosphate was "not to be confused with phosphoric acid, a chemical compound found in detergents and fertilizers". I suspect it is only found in detergents and fertilisers when something has gone wrong with the production process (notwithstanding diluted phosphoric acid has been used directly as a fertiliser) 4. It is a corrosive and irritant substance that can cause bronchitis – although tiny amounts are added to some colas. [n.b., cocaine also once featured in some cola, but that is no longer allowed.]
An ion is an electrically charged particle
The phosphate ion is one example of a type of ion.
Phosphates (such as calcium phosphate) are substances that contain phosphate ions.
So, phosphates contain electrically charged particles (phosphate ions), but that does not make phosphate an electrically charged particle, just as
blue does not mean a large marine mammal
bank does not mean a day of celebration where people do not need to go to work
vice does not mean a senior executive officer
motor does not mean a two wheeled vehicle
compact does not mean a flat circular object
final does not mean a simple musical instrument played with the breath
free does not mean a meal taken around noon or soon after, and
meal does not mean a token that provides entry or service
Grammarist invited feedback: I sent it some, so hopefully by the time you read this, the entry will have been changed.
It was on the internet: it must be true
The internet is an immense and powerful tool giving access to the vast resources of the World Wide Web. Unfortunately, the downside of a shared, democratic, free to access, reservoir of human knowledge is that there is no quality control. There is a lot of really good material on the web: but there is also a lot of nonsense on the web.
One example I have referred to before is the statement:
"energy is conserved in chemical reactions so can therefore be neither created nor destroyed"
This has the form of a logical structure
X so therefore Y
which is equivalent to
Y because X:
"energy can be neither created nor destroyed because it is conserved in chemical reactions"
This is just nonsense. There is no logical reason why the conservation of energy in chemical reactions implies a general principle of energy conservation.
We can deduce the specific from the general (days have 24 hours, so Sunday has 24 hours) but not the general from the specific (January has 31 days, so months have 31 days).
Perhaps this is easily missed by people who already know that energy is always conserved.
A parallel structure might be:
"association football teams always consist of eleven players so therefore sports teams always consist of eleven players"
"sports teams always consist of eleven players because association football teams always consist of eleven players"
This is 'obviously' wrong because we know that rugby teams and netball teams and volleyball teams and water polo teams (for example) do not consist of eleven players.
But what about quinine containing rare earth compounds? A notion that is structurally similar to claiming that
France contains South American countries, or
'Great Expectations' contains Jane Austin novels, or
February contains Autumn months, or
Cauliflower contains citrus fruits, or
Beethoven's 5th Symphony contains Haydn concerti
(in other words, something obviously silly to someone who has a basic understanding of the domain – chemistry or geography or literature or the calender or botany/horticulture or music – because it suggest one basic unit contains other units of similar status).
How does this error appear so often? Quite likely, a lot of website now are populated with material collected and collated by machines from other websites. If so, it only takes one human being (or government department) to publish something incorrect, and in time it is likely to start appearing in various places on the web.
There is currently a lot of talk of how artificial intelligence (AI) is getting better at writing essays, and answering questions, and even drafting lectures for busy academics. AI seemingly has great potential where it is provided with high quality feedback. Perhaps, but where the AI is based on finding patterns in publicly available texts, and has no real ability to check sense, then I wonder if the www is only going to become more and more polluted with misinformation and nonsense.
I do not know where Lucy Jane Santos got the idea that there are other substances in the single substance quinine (akin to having other countries in France), but if she did a web-search and relied on what she read, then I am in no position to be critical. I use the web to find things out and check things all the time. I am likely to spot gross errors in fields where I already have a strong background…but outside of that? I do seek to evaluate the likely authority of sources – but that does not mean I could not be taken in by a site which looked professional and authoritative.
The web started with imperfect people (because we all are) posting all kinds of material – with all kinds of motivations. I expect most of it was well-meaning, and usually represented something the poster actually believed; and indeed much of it was valid. However, a 'bot' can search, copy, and paste far quicker than a person, and if the internet is increasingly authored by programs that are indiscriminately copying bits and pieces from elsewhere to collage new copy to attract readers to advertising, then one cannot help wonder if the proportion of web-pages that cannot be trusted will be incrementally coming to dominate the whole network.
I (a fallible, but natural intelligence) hope not, but I am not very optimistic.
Work cited:
Santos, Lucy Jane (2020) Half lives. The unlikely story of radium. Icon.
1 Although my own research has been in science education and not one of the natural sciences, I am pleased that the learned societies (e.g. the Institute of Physics, the Royal Society of Chemistry, etc.) and the UK's Science Council, recognise the work of science educators as professional contributions to science.
2 One internet site suggests:
Luminescence is caused by various things like electric current, chemical reactions, nuclear radiation, electromagnetic radiation, etc. But phosphorescence takes place after a sample is irradiated with light.
• Phosphorescence remains for sometime even after the lighting source is removed. But luminescence is not so.
The second paragraph is nonsensical since phosphorescence is a type of luminescence. (It should be, "…fluorescence" that does not.) The first paragraph seems reasonable except that the 'but' seems misplaced. However 'in the light of' the second sentence (which sees phosphorescence and luminescence as contrary) it seems that the (contrasting) 'but' was intended, and whoever wrote this did not realise that light is a form of electromagnetic radiation.
Another, more technical, site suggests,
Luminescence is the emission of light by a substance as a result of a chemical reaction (chemiluminescence) or an enzymatic reaction (bioluminescence).
chemiluminescence (due to a chemical reaction) versus
bioluminescence (due to an enzymatic reaction).
However, the keen-eyed will have spotted that "an enzymatic reaction" is simply a chemical reaction catalysed by an enzyme. So, bioluminescence is a subtype of chemiluminescence, not something distinct.
3 Some sources claim that the medicinal properties of cinchona bark were discovered by Jesuit missionaries that travelled to South America as part of European imperial expansion there.
Nataly Allasi Canales of the Natural History Museum of Denmark, University of Copenhagen is reported as explaining that actually,
"Quinine was already known to the Quechua, the Cañari and the Chimú indigenous peoples that inhabited modern-day Peru, Bolivia and Ecuador before the arrival of the Spanish…They were the ones that introduced the bark to Spanish Jesuits."
Learning about the history of indigenous technologies can be complicated because:
often they are transmitted by an oral and practice culture (rather than written accounts);
traditional practices may be disrupted (or even suppressed) by colonisation by external invaders; and
European colonisers, naturalists and other travellers, often did not think their indigenous informants 'counted', and rather considered (or at least treated) what they were shown as their own discoveries.
4 This again seems to reflect the common alternative conception that confuses mixtures and compounds (Taber, 1996): phosphoric acid is used in reactions to produce fertilizers and detergents, but having reacted is no longer present. It is a starting material, but not an ingredient of the final product.
Just as we do not eat iron and phosphorus, we do not use washing powders that contain phosphoric acid, even if they have been prepared with it. (Increasingly, phosphates are being replaced in detergents because of their polluting effects on surface water such as rivers and lakes.)
5 This gives the impression to me that the Department of Education sees schooling as little more than a game where students perform and are tested on learning whatever is presented to them, rather than being about learning what is worth knowing. There is surely no value in learning a logically flawed claim. Any student who understands the ideas will appreciate this statement is incorrect, but perhaps the English Government prefers testing for recall of rote learning rather than looking for critical engagement?
This page contains a number of scientifically incorrect statements, but I am most concerned about your misleading characterisation of phosphorus as a 'safe' material.
Scientific errors
Your site claims that
"phosphorus…has the ability to absorb and store surrounding light"
"the ability to absorb and store surrounding light…works similar to the natural process of photosynthesis"
"Phosphorus glow absorbs and stores surrounding light. When it is dark, the stored light is slowly released in the form of a glow"
"Glow in the Dark products contain phosphorus…it needs to be exposed to light before it can work"
"Radium glow produces light on its own through a chemical process."
All of these claims are mistaken.
1. Luminescent materials do not store light. Light cannot be stored, it is a form of electromagnetic radiation. (In LASERS light is contained within a cavity by reflecting it back and forth by mirrors, but phosphorus is not able to do anything like this.) When the radiation is absorbed by a photoluminescent material the radiation ceases to exist. Because the molecules of the absorbing material are excited into a higher energy state, new electromagnetic radiation (light) may later be emitted – but it is not light that has been stored. (The energy transferred to the luminescent material by the radiation may be considered as stored: but not the light).
2. The process of photosynthesis does not involve "the ability to absorb and store surrounding light" – absorb, yes, but the light is not stored – it ceases to exist once absorbed.
3. Materials which absorb energy from radiation, and then release it slowly ('glow') are called phosphorescent. This does not (only) occur 'when it is dark', but from immediately after irradiation. (The process occurs regardless of whether it is dark enough to observe.)
4. Phosphorus is not itself a phosphorescent material. The glow seen around white phosphorus is due to a chemical reaction with oxygen in the air. Not only does this not store any light, but, also, it does not need light to initiate.
5. Radium does NOT produce light through a chemical process. Radium is radioactive. It undergoes radioactive decay (due to a change in the atomic nucleus). This is NOT considered a chemical process.
Now I turn to what I consider a more serous problem with your site.
Potentially dangerous misinformation
The more serious matter concerns your claim that to be selling products containing 'non toxic' phosphorus:
"Glow in the Dark products contain phosphorus (a non toxic substance) which has the ability to absorb and store surrounding light…"
"Phosphorus is non toxic and safe for general use."
"Phosphorus is a natural mineral found in the human body. Phosphorus Glow in the dark products is perfectly safe for everyday use"
"Many get confused and associate all green glow products to be radioactive. This is not true. Phosphorus glow is non toxic and non radioactive."
You may wonder why I think this matters enough to contact you.
It is very misleading to suggest to people reading the site (which could include children who might well be interested in glow-in-the-dark toys) that phosphorus is harmless, and this is completely wrong.
Phosphorus is not found as a natural mineral, as it is much too reactive to be found native (that is, as phosphorus) on earth – although many minerals are compounds of phosphorus (and thus do NOT share its chemical properties), and so sources of the element for use in agriculture etc. The human body does contain compounds of phosphorus, notably in the bones, but again there is no phosphorus (the substance phosphorus) in the human body – if you introduced some it would very quickly react. Sources of phosphorus are important in the diet, but it would be very unwise to try to eat phosphorus itself.
Phosphorus can be obtained in different forms (this is called allotropy where the same element can have different molecular structures – like graphite and diamond both being pure forms – allotropes -of carbon). Some allotropes of phosphorus are not especially dangerous. However, the form which glows is white (or yellow) phosphorus, and this is a very hazardous material.
So, handling phosphorus is dangerous and needs special precautions. (If you really did use phosphorus in your products, I imagine you would know that?) Here is some information from authoritative websites
"Ingestion of elemental white or yellow phosphorus typically causes severe vomiting and diarrhea [diarrhoea], which are both described as "smoking," "luminescent," and having a garlic-like odor. Other signs and symptoms of severe poisoning might include dysrhythmias, coma, hypotension, and death. Contact with skin might cause severe burns within minutes to hours…"
"White phosphorus is extremely toxic to humans, while other forms of phosphorus are much less toxic. Acute (short-term) oral exposure to high levels of white phosphorus in humans is characterised by three stages: the first stage consists of gastrointestinal effects; the second stage is symptom-free and lasts about two days; the third stage consists of a rapid decline in condition with gastrointestinal effects, plus severe effects on the kidneys, liver, cardiovascular system, and central nervous system (CNS). Inhalation exposure has resulted in respiratory tract irritation and coughing in humans. Chronic (long-term) exposure to white phosphorus in humans results in necrosis of the jaw, termed "phossy jaw."
Please feel free to check on this information for yourself.
However, I recommend you change the information on your website. In particular, please stop suggesting that phosphorus is a safe, non-toxic material, when the form of phosphorus which glows is highly toxic. I trust that now this has been brought to your attention, you will appreciate that it would be highly irresponsible for you to continue to advertise your products using misleading information about a hazardous substance.
Particle intuitions may not match scientific models
Keith S. Taber
Sophia was a participant in the Understanding Science Project. I first talked to her when she was in Y7, soon after she began her secondary school course.
One of the first topics she studied in her science was 'solids, liquids and gases', where she had learnt,
that solids are really hard and they stay together more, and then liquids are close together but they move around, and gases are really free and they just go anywhere
She had studied a little about the topic in her last year of primary school (Y6), but now she was being told
about the particles…the things that make – the actual thing, make them a solid, and make them a gas and make them a liquid
Particle theory, or basic kinetic theory, is one of the most fundamental theories of modern science. In particular, much of what is taught in school chemistry is explained in terms of theories involving how the observed macroscopic properties emerge from the characteristics and interactions of conjectured sub-microscopic particles that themselves often have quite unfamiliar properties. This makes the subject very abstract, challenging, and tricky to teach (Taber, 2013a).
Particle theory is often introduced in terms of the states of matter. Strictly there are more than three states of matter (plasma and Bose-Einstein condensates are important in some areas of science) but the familiar ones, and the most important in everyday phenomena, are solid, liquid and gas.
The scientific account is, in simple terms, that
different substances are made up of different types of particle
the different states of matter of a single substance have the same particles arranged differently
These are very powerful ideas, even if there are many complications. For example,
the terms solid, liquid and gas only strictly apply to pure samples of a single substance, not mixtures (so not, for example, to bronze, or honey, or, milk, or ketchup, or even {if one is being very pedantic} air or sea water. And cats (please note, BBC) are completely inadmissible. )
common salt is an example of a pure substance, that none-the-less is considered to be made up of more than one type of particle
This reflects a common type of challenge in teaching science – the full scientific account is complex and nuanced, and not suitable for presenting in an introductory account; so we need to teach a simplified version that introduced the key ideas, and then only once this is mastered by learners are they ready to develop a more sophisticated understanding.
Yet, there is a danger that students will learn the simplified models as truths supported by the authority of science – and then later have difficulty shifting their thinking on. This is not only counter-productive, but can be frustrating and de-motivating for learners who find hard-earned knowledge is not as sound as they assumed.
One response to this is to teach science form very early in a way that is explicit about how science builds models of the natural world: models that are often simplifications which are useful but need to be refined and developed to become powerful enough to expand the range of contexts and examples where they can be applied. That is, students should learn they are being taught models that are often partial or imperfect, but that is just a reflection of how science works, developing more sophisticated understanding over time (Taber, 2017).
Sophia confirmed that the iron clamp stand near where she was sitting would have particles in it, as would a lump of ice.
Are they the same particles in the ice as the iron?
Yeah, because they are a solid, but they can change.
Ah, how can they change?
Cause if, erm, they melted they would be a liquid so they would have different particles in.
Right, so the iron is a solid,
Uh hm.
So that's got one type of particle?
Yeah.
And ice is also a solid?
Yeah.
So that has the same sort of particles?
Yeah, but they can change.
The ones in the ice?
Mm,
To a learner just meeting particle theory for the first time, it may seem just as feasible that the same type of particle is found in one state as in one substance.
In the scientific model, we explain that different substances contain different types of particles, whereas different states of the same substance contain different arrangements of the same particles: but this may not be intuitively obvious to learners.1 It seemed Sophia was thinking that the same particles would be in different liquids, but a change of state led to different particles. This may seem a more forced model to a teacher, but then the teacher is already very familiar with the scientific account, and also has an understanding of the nature of those particles (molecules, ions, atoms – with internal structure and charges that interact with each other within and between the particles) – which are just vague, recently imagined, entities to the novice.
Sophia seemed to misunderstood or misremembered the model she had been taught, but to a novice learner these 'particles' have no more immediate referent than an elf or an ogre and would be considerably more tenuous than a will-o'-the-wisp.
Sophia seemed to have an alternative conception, that all solids have one type of particle, and all liquids another. If I had stopped probing at that point I might have considered this to be her thinking on the matter. However, when one spends time talking to students it soon becomes clear that often they have ideas that are not fully formed, or that may be hybrids of different models under consideration, and that often as they talk they can talk themselves into a position.
So, if I melted the ice – that changes the particles in the solid?
Well they are still the same particles but they are just changing the way they act…
Oh.
How do they change?
A particle in a liquid [sic, solid] is all crammed together and don't move around, but in a liquid they can move around a little but they are still close and, can, you can pour a liquid, where you can't a solid, because they can move in.
Okay, so if I have got my ice, that's a solid, and there are particles in the ice, and they behave in a certain way, and if the ice melts, the particles behave differently?
Yeah.
Do you know why they behave differently in the liquid?
No. {giggles} So, they can, erm
• • • • • • • • • • • • [A pause of approximately 12 s]
They've more room cause it's all spread out more1, whereas it would be in a clump
The literature on learners conceptions often suggests that students have this or that conception, or (when survey questions are used) that this percentage thinks this, and that percentage thinks that (Taber, 2013b). That this is likely to be a simplification seems obvious is we consider what thinking is – whatever thought may be, is it a dynamic process, something that moves along. Our thinking is, in part, resourced by accessing what we have represented in memory, but it is not something fixed – rather something that shifts, and that often becomes more sophisticated and nuanced as we explore a focus in greater depth.
I think Sophia did seem to have an intuition that there were different types of particles in different states of matter, and that therefore a change of state meant the particles themselves changed in some way. As I probed her, she seemed to shift to a more canonical account where change of state involved a change in the arrangement or organisation of particles rather than their identity.
This may have simply been her gradually bringing to mind what she had been taught – remembering what the teacher had said. It is also possible that the logic of the phenomenon of a solid becoming a liquid impressed on her that they must be the same particles. I suspect there was a little of both.
When interviewing students for research we inevitably change their thinking and understanding to some extent (hopefully, mostly in a beneficial way!) (If only teachers had time to engage each of their students in this way about each new topic they might both better understand their students' thinking, and help reinforce what has been taught.)
Did Sophia 'have a misconception'? 1 What did she 'really think'? That, surely, is to oversimplify.
She presented with an alternative conception, that under gentle questioning she seemed to talk /think herself out of. The extent to which her shift in position reflected further recall (so, correcting her response) or 'thinking through' (so, developing her understanding) cannot be known. Likely there was a little of both. What memory research does suggest is that being asked to engage in and think about this material will have modified and reinforced her memories of the material for the future.
Johnson, P. M. (2012). Introducing Particle Theory. In K. S. Taber (Ed.), Teaching Secondary Chemistry (Second ed., pp. 49-73). Association for Science Education/John Murray.
1 Actually, the particles in a liquid are not substantially spread further apart than in a solid. (Indeed, when ice melts the water molecules move closer together on average.) Understanding melting requires an appreciation of the attractions between particles, and how heating provides more energy for the particles. This idea of increased separation on melting is therefore something of an alternative conception, if one that is sometimes encouraged by the diagrams in school textbooks.
Teaching an introductory particle theory based on the arrangement of particles in different states, without reference to the attractions between particles is problematic as it offers no rational basis for why condensed states exists, and why energy is needed to disrupt them – something highlighted in the work of Philip Johnson (2012).
It may be difficult to know what counts as an alternative conception in some topics – and sometimes research does not make it any clearer
Keith S. Taber
If a reader actually thought the researchers themselves held these alternative conceptions then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others
I recently published an article here where I talked in some detail about some aspects of a study (Tarhan, Ayyıldız, Ogunc & Sesen, 2013) published in the journal Research in Science and Technological Education. Despite having a somewhat dodgy title 1, this is a well respected journal published by a serious publisher (Routledge/Taylor & Francis). I read the paper because I was interested in the pedagogy being discussed (jigsaw learning), but what promoted me to then write about it was the experimental design: setting up a comparison between a well-tested active learning approach and lecture-based teaching. A teacher experienced in active learning techniques taught a control group of twelve year old pupils through a 'traditional' teaching approach (giving the children notes, setting them questions…) as a comparison condition for a teaching approach based on engaging group-work.
The topic being studied by the sixth grade, elementary school, students was physical and chemical changes.
I did not discuss the outcomes of the study in that post as my focus there was on the study as possibly being an example of rhetorical research (i.e., a demonstration set up to produce a particular outcome, rather than an open-ended experiment to genuinely test a hypothesis), and I was concerned that the control conditions involved deliberately providing sub-optimal, indeed sub-standard, teaching to the learners assigned to the comparison condition.
The researchers actually tested the outcome of their experiment in two ways (as well as asking students in the experimental condition about their perceptions of the lessons), a post-test taken by all students, and "ten-minute semi-structured individual interviews" with a sample of students from each condition.
Analysis of the post-test allowed the researchers to identify the presence of students' alternative conceptions ('misconceptions'2) related to chemical and physical change, and the identified conceptions are reported in the study. Interviewees were purposively selected,
"Ten-minute semi-structured individual interviews were carried out with seven students from the experimental group and 10 students from the control group to identify students' understanding of physical and chemical changes by acquiring more information about students' unclear responses to [the post-test]. Students were selected from those who gave incorrect, partially correct and no answers to the items in the test. During the interviews, researchers asked the students to explain the reasons for their answers to the items."
Tarhan et al., 2013, p.188
I was interested to read about the alternative conceptions they had found for several reasons:
I have done research into student thinking, and have written a lot about alternative conceptions, so the general topic interests me;
More specifically, it is interesting to compare what researchers find in different educational contexts, as this gives some insight into the origins and developments of such conceptions;
In this post I am going to question whether the author's claims in their research report about some of the alternative conceptions they reported finding are convincing. First, however, I should explain the second point here.
Cultural variations in alternative conceptions
Some alternative conceptions seem fairly universal, being identified in populations all around the world. These may primarily be responses to common experiences of the natural world. An obvious example relates to Newton's first law (the law of inertia): we learn from very early experience, before we even have language to talk about our experiences, that objects that we push, throw, kick, toss, pull… soon come to a stop. They do not move off in a straight line and continue indefinitely at a constant speed.
Of course, that experience is not actually contrary to Newton's first law (as various forces are acting on the objects concerned), but it presents a consistent pattern (objects initially move off, but soon slow and stop) that becomes part of out intuitions about the world and so makes learning the scientific law seem counter-intuitive, and so more difficult to accept and apply when taught in school.
By contrast, no one has ever tested Newton's first law directly by seeing what happens under the ideal conditions under which it would apply (see 'Poincaré, inertia, and a common misconception').
Other alternative conceptions may be less universal: some may be, partially at least, due to an aspect of local cultural context (e.g. folk knowledge, local traditions), the language of instruction, the curriculum or teaching scheme, or even a particular teacher's personal way of presenting material.
So, to the extent that there are some experiences that are universal for all humans, due to commonalities in the environment (e.g., to date at least, all members of the species have been born into an environment with a virtually constant gravitational field and a nitrogen-rich atmosphere of about 1 atmosphere pressure {i.e., c.105 Pa} and about 21% oxygen content), there is a tendency for people everywhere (on earth) to develop the same alternative conceptions.
And, conversely, to the extent that people in different institutional, social, and cultural contexts have contrasting experiences, we would expect some variations in the levels of incidence of some alternative conceptions across populations.
"Some common ideas elicited from children are spread, at least in part, through informal learning in everyday "life-world" contexts. Through such processes youngsters are inducted into the beliefs of their culture. Ideas that are common in a culture will not usually contradict everyday experience, but clearly beliefs may develop and be disseminated without matching formal scientific knowledge. …
Where life-world beliefs are relevant to school science – perhaps contradicting scientific principles, perhaps apparently offering an explanation of some science taught in school; perhaps appearing to provide familiar examples of taught principles – then it is quite possible, indeed likely, that such prior beliefs will interfere with the learning of school science. …
Different common beliefs will be found among different cultural groups, and therefore it is likely that the same scientific concepts will be interpreted differently among different cultural groups as they will be interpreted through different existing conceptual frameworks."
As a trivial example, in England the National Curriculum for primary age children in England erroneously describes some materials that are mixtures as being substances. These errors have persisted for some years as the government department does not think they are important enough to make the effort to correct the error. Assuming many primary school teachers (who are usually not science specialists, though some are of course) trust the flawed information in the official curriculum, we might expect more secondary school students in England, than in other comparable populations, to later demonstrate alternative conceptions in relation to the critical concept of a chemical substance.
"This suggests that studies from different contexts (e.g., different countries, different cultures, different languages of instruction, and different curriculum organisations) should be encouraged for what they can tell us about the relative importance of educational variables in encouraging, avoiding, overcoming, or redirecting various types of ideas students are known to develop."
Language of instruction may sometimes be important. Words that supposedly are translated from one language to another may actually have different nuances and associations. (In English, it is clearly an alternative conception to think the chemical elements still exist in a compound, but the meaning of the French élément chemie seems to include the 'essence' of an element that does continue into compound.)
Research in different educational contexts can in principle help unravel some of this: in principle as it does need the various researchers to detail aspects of the teaching contexts and cultural contexts from which they report as well as the student's ideas (Taber, 2012a).
Chemical and physical change
Teaching about chemical and physical change is a traditional topic in school science and chemistry courses. It is one of those dichotomies that is understandably introduced in simple terms, and so, offers a simplification that may need to be 'unlearnt' later:
[a change is] chemical change or physical change
[an element is] metal or non-metal
[a chemical bond is] ionic bonding or covalent bonding
There are some common distinctions often made to support this discrimination into two types of change:
However, a little thought suggests that such criteria are not especially useful in supporting the school student making observations, and indeed some of these criteria simply do not stand up to close examination. 2
"the distinction between chemical and physical changes is a rather messy one, with no clear criteria to help students understand the difference"
So, I was especially interested to know what Tarhan and colleagues had found.
Methodological 'small print'
In reading any study, a consideration of the findings has to be tempered by an understanding of how the data were collected and analysed. Writing-up research reports for journals can be especially challenging as referees and editors may well criticise missing details they feel should be reported, yet often journals impose word-limits on articles.
Currently (2023) this particular journal tells potential authors that "A typical paper for this journal should be between 7000 and 8000 words" which is a little more generous than some other journals. However, Tarhan and colleagues do not fully report all aspects of their study. This may in part be because they need quite a lot of space to describe the experimental teaching scheme (six different jigsaw learning activities).
Whatever the reason:
the authors do not provide a copy of the post-test which elicited the responses that were the basis of the identified alternative conceptions; and
nor do they explain how the analysis to identify conceptions was undertaken – to show how student responses were classified;
similarly, there are no quotations from the interview dialogue to illustrate how the researchers interpreted student comments .
Data analysis is the process of researchers interpreting data so they become evidence for their findings, and generally research journals expect the process to be detailed – but here the reader is simply told,
"Students' understanding of physical and chemical changes was identified according to the post-test and the individual interviews after the process."
Although the term 'misconception' is used 32 times in the paper (not counting instances in the reference list), the term is not explained in the text, presumably because it is assumed that all those working in science education know (and agree) what it means. This is not at all unusual. I once wrote about another study
"[The] qualities of misconceptions are largely assumed by the author and are implicit in what is written…It could be argued that research reports of this type suggest the reported studies may themselves be under-theorised, as rather well-defined technical procedures are used to investigate foci that are themselves only vaguely characterised, and so the technical procedures are themselves largely operationalised without explicit rationale."
Unfortunately, in Tarhan and colleagues' study there are less well-defied technical procedures in relation to how data was analysed to identify 'misconceptions', so leaving the reader with limited grounds for confidence that what are reported are worthy of being described as student conceptions – and are not just errors or guesses made on the test. Our thinking is private, and never available directly to others, and, so, can only be interpreted from the presentations we make to representour conceptions in a public (shared) space. Sometimes we mis-speak, or we mis-write (so that then our words do not accurately represent our thoughts). Sometimes our intended meanings may be misinterpreted (Taber, 2013).
Perhaps the researchers felt that this process of identifying conceptions from students' texts and utterances was unproblematic – perhaps the assignments seemed so obvious to the researchers that they did not need to exemplify and justify their analytical method. This is unfortunate. There might also be another factor here.
Lost and found in translation?
The study was carried out in Turkey. The paper is in English, and this includes the reported alternative conceptions. The study was carried out "in a public elementary school" (not an international school, for example). Although English is often taught as a foreign language in Turkish schools, the language of instruction, not unreasonably, is Turkish.
So, it seems either
the data was collected in (what, for the children, would have been) 'L2' – a second language, or
a study carried out (questions asked; answers given) in Turkish has been reported in English, translating where necessary from one language to another.
This issue is not discussed at all in the paper – there is no mention of either the Turkish or English language, nor of anything being translated.
Yet the authors are not oblivious to the significance of language issues in learning. They report how one variant of Jigsaw teaching had "been designed specifically to increase interaction among students of differing language proficiencies in bilingual classrooms" (p.186) and how the research literature reports that sometimes children's ideas reflect "the incorrect use of terms in everyday language" (p.198). However, they did not feel it was necessary to report either that
data had been collected from elementary school children in a second language, or
data had been translated for the purposes of reporting in an English language journal
It seems reasonable to assume they would have appreciated the importance of mentioning option 1, and so it seems much more likely (although readers of the study should not have to guess) the reporting in English involved translation. Yet translation is never a simple algorithmic process, but rather always a matter of interpretation (another stage in analysis), so it would be better if authors always acknowledged this – and offered some basis for readers to consider the translations made were of high quality (Taber, 2018).
It is a general principle that the research community should adopt, surely, that whenever material reported in a research paper has been translated from another language (a) this is reported and (b) evidence of the accuracy and reliability of the translation is offered (Taber, 2018).
I make this point here, as some of the alternative conceptions reported by the authors are a little mystifying, and this may(?) be because their wording has been 'degraded' (and obscured) by imperfect translation.
An alternative conception of combustion?
For example, here are two of the learning objectives from one of the learning activities:
"The students were expected to be able to:
…comment on whether the wood has similar intensive properties before and after combustion
…indicate the combustion reactions in examples of several physical and chemical changes"
Tarhan et al., 2013, p.193
The wording of the first of these examples seems to imply that when wood is burnt, the product is still…wood. That is nonsense, but possibly this is simply a mistranslation of something that made perfect sense in Turkish. (The problem is that a reader can only speculate on whether this is the case, and research reports should be precise and explicit.)
The second learning objective quoted here implies that some combustion reactions are physical changes (or, at least, combustion reactions are components of some physical changes).
Combustion reactions are a class of chemical reactions. 'Chemical reaction' is synonymous with 'chemical change'. So, there are (if you will excuse the double negative) no examples of combustion reactions that are not chemical reactions and which would be said to occur in physical changes. So, this is mystifying, as it is not at all clear what the children were actually being taught unless one assumes the researchers themselves have very serious misconceptions about the chemistry they are teaching.
If a reader actually thought that the researchers themselves held these alternative conceptions
the product of combustion of wood is still wood
some combustion reactions are (or occur as part of) physical changes
then one could have little confidence in their ability to distinguish between the scientific and alternative conceptions of others. (A reader might also ask how come the journal referees and editor did not ask for corrections here before publication – I certainly wondered about this).
There are other statements the authors make in describing the teaching which are not entirely clear (e.g., "give the order of the changes in matter during combustion reactions", p.194), and this suggests a degree of scepticism is needed in not simply accepting the reported alternative conceptions at face value. This does not negate their interest, but does undermine the paper's authority somewhat.
One of the misconceptions reported in the study is that some students thought that "there is a flame in all combustion reaction". This led me to reflect on whether I could think of any combustion reactions that did not involve a flame – and I must confess none readily came to mind. Perhaps I also have this alternative conception – but it seems a harsh judgement on elementary school learners unless they had actually been taught about combustion reactions without flames (if, indeed, there are such things).
The study reported that some 12 year olds held the 'misconception' that "there is a flame in all combustion reaction[s]".
[Image by Susanne Jutzeler, Schweiz, from Pixabay]
Failing to control variables?
Another objective was for students to "comprehend that temperature has an effect on chemical reaction rate by considering the decay of fruit at room temperature, and the change in color [colour] from green to yellow of fallen leaves in autumn" (p.193). As presented, this is somewhat obscure.
Presumably it is not meant to be a comparison between:
the rate of decay of fruit at room temperature
and
the rate of change in colour of fallen leaves in autumn
Explaining that temperature has an effect on chemical reaction rate?
Clearly, even if the change of colour of leaves takes place at a different temperature to room temperature, one cannot compare between totally different processes at different temperatures and draw any conclusions about how "temperature has an effect on chemical reaction rate" . (Presumably, 'control of variables' is taught in the Turkish science curriculum.)
So, one assumes these are two different examples…
But that does not help matters too much. The "decay of fruit at room temperature" (nor, indeed, any other process studied at a single temperature) cannot offer any indication of how "temperature has an effect on chemical reaction rate". The change of colours in leaves of deciduous trees (that usually begins before they fall) is triggered by environmental conditions such as change in day length and temperature. This is part of a very complex system involving a range of pigments, whilst water content of the leaf decreases (once the supply of water through the tree's vascular system is cut off), and it is not clear how much detail these twelve year olds were taught…but it is certainly not a simple matter of a reaction changing rate according to temperature.
Evaluating conceptions
Tarhan and colleagues report their identified alternative conceptions ('misconceptions') under a series of headings. These are reported in their table 4 (p.195). A reader certainly finds some of the entries in this table easy to interpret: they clearly seem to reflect ideas contrary to the canonical science one would expect to be reflected in the curriculum and teaching. Other statements are less obviously evidence of alternative conceptions as they do not immediately seem necessarily at odds with scientific accounts (e.g., associating combustion reactions with flames).
Other reported misconceptions are harder to evaluate. School science is in effect a set of models and representations of scientific accounts that often simplify the actual current state of scientific knowledge. Unless we know exactly what has been taught it is not entirely clear if students' ideas are credit-worthy or erroneous in the specific context of their curriculum.
Moreover, as the paper does not report the data and its analysis, but simply the outcome of the analysis, readers do not know on what basis judgements have been made to assign learners as having one of the listed misconceptions.
Changes of state are chemical changes
A few students from the lecture-based teaching condition were identified as 'having' the misconception that 'changes of state are chemical changes'. This seems a pretty serious error at the end of a teaching sequence on chemical and physical changes.
However, this raises a common issue in terms of reports of alternative conceptions – what exactly does it mean to say that a student has a conception that 'changes of state are chemical changes'? A conception is a feature of someone's thinking – but that encompasses a vast range of potential possibilities from a fleeting notion that is soon forgotten ('I wonder if s orbitals are so-called because they are spherical?') to an on-going commitment to an extensive framework of ideas that a life is lived by (Buddhism, Roman Catholicism, Liberalism, Hedonism, Marxism…).
A person's conceptions can vary along a range of characteristics (Figure from Taber, 2014)
The statement that 'Changes of state are chemical changes' is unlikely to be the basis of anyone's personal creed. It could simply be a confusion of terms. Perhaps a student had a decent understanding of the essential distinction between chemical and physical changes but got the terms mixed up (or was thinking that 'changes of state' meant 'chemical reaction'). That is certainty a serious error that needs correcting, but in terms of understanding of the science, would seem to be less worrying than a deeper conceptual problem.
In their commentary, the authors note of these children:
"They thought that if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".
Tarhan et al., 2013, p.197
It is not clear if this was an explanation the learners gave for thinking "changes of state are chemical changes", or whether "changes of state are chemical changes" was the researchers' gloss on children commenting that "if ice was heated up water formed, and if water was heated steam formed, so new matter was formed and chemical changes occurred".
That a range of students are said to have precisely the same train of thought leads a reader (or, at least, certainly one with experience of undertaking research of this kind) to ask if these are open-ended responses produced by the children, or the selection by the children of one of a number of options offered by the researchers (as pointed out above, the data analysis is not discussed in detail in the paper). That makes a difference in how much weight we might give to the prevalence of the response (putting a tick by the most likely looking option requires less commitment to, and appreciation of, an idea than setting it out yourself in your own personally composed text), illustrating why it is important that research journals should require researchers to give full accounts of their instrumentation and analysis.
Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change
Thirteen of the children (all in the lecture-based teaching condition) were considered to have the conception "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change". This is clearly a much more specific conception (than 'changes of state are chemical changes') which can be analysed into three components:
a change of state is a chemical change, AND
we know this because such changes involve a change in identity, AND
we know that because a change of state leads to a change in density
Terhan and colleagues claim this conception was "first determined in this study" (p.195).
The specificity is intriguing here – if so many students explicitly and individually built this argument for themselves then this is an especially interesting finding. Unfortunately, the paper does not give enough detail of the methodology for a reader to know if this was the case. Again, if students were just agreeing with an argument offered as an option on the assessment instrument then it is of note, but less significant (as in such cases students might agree with the statement simply because one component resonated – or they may even be guessing rather than leaving an item unanswered). Again this does not completely negate the finding, but it leaves its status very unclear.
Taken together these first two claimed results seem inconsistent – as at least 13 students seem to think "Changes of state are chemical changes". That is, all those who thought that "Because density of matter changes during changes of state, its identity also changes, and so it is a chemical change" would seem to have thought that "Changes of state are chemical changes" (see the Venn diagram below). Yet, we are also told that only five students held the less specific and seemingly subsuming conception "changes of state are chemical changes".
If 13 students think that changes of state are chemical changes because a change of density implies a change of identity; what does it mean that only 5 students think that changes of state are chemical changes?
This looks like an error, but perhaps is just a lack of sufficient detail to make the findings clear. Alternatively, perhaps this indicates some failure in translating material accurately into English.
The changes in the pure matters are physical changes
Six children in the lecture-based teaching condition and one in the jigsaw learning condition were reported as holding the conception that "The changes in the pure matters are physical changes". The authors do not explain what they mean here by "pure matters" (sic, presumably 'matter'?). The only place this term is used in the paper is in relation to this conception (p.195, p.197).
The only other reference to 'pure' was in one of the learning objectives for the teaching:
explain the changes of state of water depending on temperature and pressure; give various examples for other pure substances (p.191)
If "pure matter" means a pure sample of a substance, then changes in pure substances are all physical – by definition a chemical changes leads to a different substance/different substances. That would explain why this conception was "first determined [as a misconception] in this study", p.195, as it is not actually a misconception)". So, it does not seem clear precisely why the researchers feel these children have got something wrong here. Again, perhaps this is a failure of translation rather than a failure in the original study?
Changes in shape?
Tarhan and colleagues report two conceptions under the subheading of 'changes in shape'. They seem to be thinking here more of grain size than shape as such. (Another translation issue?) One reported misconception is that if cube sugar is granulated, sugar particles become small [smaller?].
Is it really a misconception to think that "If cube sugar is granulated, sugar particles become small"?
(Image by Bruno /Germany from Pixabay)
Tarhan and colleagues reported that two children in the experimental condition, and 13 in the control condition thought that "If cube sugar is granulated, sugar particles become small". Sugar cubes are made of granules of sugar weakly joined together – they can easily be crumbled into the separate grains. The grains are clearly smaller than the cubes. So, what is important here is what is meant/understood* by the children by the term 'particles'.
(* If this phrasing was produced by the children, then we want to know what they meant by it. If, however, the children were agreeing with a phrase presented to them by researchers, then we wish to know how they understood it.)
If this means quanticle level particles, molecules, then it is clearly an alternative conception – each grain contain vast numbers of molecules, and the molecules are unchanged by the breaking up the cubes. If, however, particles here refers to the cube and grains**, then it is a fair reflection of what happens: one quite large particle of sugar is broken up into many much smaller particles. The ambiguity of the (English) word 'particles' in such contexts is well recognised.
(** That is, if the children used the word 'particles' – did they mean the cubes/grains as particles of sugar? If however the phrasing was produced by the researchers and presented to the children, and if the researchers meant 'particles' to mean 'molecules'; did the children appreciate that intention, or did they understand'particles' to refer to the cubes and grains?)
However, as no detail is given on the actual data collected (e.g., is this the children's own words; was this based on an open response?), and how it was analysed (and, as I suspect this all occurred in Turkish) the reader has no way to check on this interpretation of the data.
What kind of change is dissolving?
Tarhan and colleagues report a number of 'misconceptions' under the heading of 'molecular solubility'. Two of these are:
"The solvation processes are always chemical changes"
"The solvation processes are always physical changes"
This reflects a problem of teaching about physical and chemical changes. Dissolving is normally seen as a physical change: there is no new chemical substance formed and dissolving is usually fairly readily reversed. However, as bonds are broken and formed it also has some resemblance to chemical change.2
In dissolving common salt in water, strong ionic bonds are disrupted and the ions are strongly solvated. Yet the usual convention is still to consider this a physical change – the original substance, the salt, can be readily recovered by evaporation of the solvent. A solution is considered a kind of mixture. In any case, as Tarhan and colleagues refer to 'molecular' solubility (strictly solubility refers to substances, not molecules, but still) they were, presumably, only dealing with examples of the dissolving of substances with discrete molecules.
Taking together these two conceptions, it seems that Tarhan and colleagues think that dissolving is sometimes a physical change, and sometimes a chemical change. Presumably they have some criterion or criteria to distinguish those examples of dissolving they consider physical changes from those they consider chemical changes. A reader can only speculate how a learner observing some solute dissolve in a solvent is expected to distinguish these cases. The researchers do not explain what was taught to the students, so it is difficult to appreciate quite what the students supposedly got wrong here.
Sugar is invisible in the water, because new matter is formed
The idea that learners think that new matter is formed on dissolving would indeed be an alternative conception. The canonical view is that new matter is only formed in very high energy processes – such as in the big bang. In both chemical and physical processes studied in the school laboratory there may be transformations of matter, but no new matter.
This seems a rather extreme 'misconception' for the learners to hold. However, a reader might wonder if the students actually suggested that a new substance was formed, and this has been mistranslated. (The Turkish word 'madde' seems to mean either matter or substance.) If these students thought that a new type of substance was formed then this would be an alternative conception (and it would be interesting to know why this led to sugar being invisible – unless they were simply arguing that different appearance implied different substance).
While sugar is dissolving in the water, water damages the structure of sugar and sugar splits off
Whether this is a genuine alternative conception or just imprecise use of language is not clear. It seems reasonable to suggest that while sugar is dissolving in the water, the process breaks up the structure of solid sugar and sugar molecules split off – so some more detail would be useful here. Again, if there has been translation from Turkish this may have lost some of the nuance of the original phrasing through translation into English.
The phrasing reflects an alternative conception that in chemical reactions one reactant is an active agent (here the water doing the damaging) and the other the patient, that is passive and acted upon (here the sugar being damaged) – rather than seeing the reaction as an interaction between two species (Taber & García Franco, 2010) – but there is no suggestion in their paper that this is the issue Tarhan and colleagues are highlighting here.
When sugar dissolves in water, it reacts with water and disappears from sight
If the children thought that dissolving was a chemical reaction then this is an alternative conception – the sugar does indeed disappear from sight, but there has been no reaction.
Again, we might ask if this was actually a misunderstanding (misconception), or imprecise use of language. The sugar does 'react' with the water in the everyday sense of 'reaction'. But this is not a chemical reaction, so this terminology should be avoided in this context.
Even in science, 'reaction' means something different in chemistry and physics: in the sense of Newtonian physics, during dissolving, when a water molecule attracts a sugar molecule {'action')'} there will be an equal and oppositely directed reaction as the sugar molecule attracts the water molecule. This is Newton's third law, which applies to quanticles as much as to planets. If a water molecule and a sugar molecule collide, the force applied by the sugar molecule on the water molecule is equal to the force applied by the water molecule on the sugar molecule.
a misunderstanding of dissolving (a genuine alternative conception);
a misuse of the chemical term 'reaction'; or
a use of the everyday term 'reaction' in a context where this should be avoided as it can be misunderstood
These are somewhat different problems for a teacher to address.
Molecules split off in physical changes and atoms split off in chemical changes
Ten of the children are said to have demonstrated the 'misconception' that molecules split off in physical changes and atoms split off in chemical changes. The authors claim that this misconception has not been reported in previous studies. But is this really a misconception? It may be a simplistic, and imprecise, statement – but I think when I was teaching youngsters of this age I would have been happy to find they have this notion – which at least seems to reflect an ability to imagine and visualise processes at the molecular level.
In dissolving or melting/boiling of simple molecular substances, molecules do indeed 'split off' in a sense, and in at least some chemical changes we can posit mechanisms that, in simple terms at least, involve atoms 'splitting off' from molecules.
So, again, this is another example of how this study is tantalising, without being very informative. The reader is not clear in what sense this is viewed as wrong, or how the conception was detected. (Again, for ten different students to specifically think that 'molecules split off in physical changes and atoms split off in chemical changes' makes one wonder if they volunteered this, or have simply agreed with the statement when having it presented to them).
The researchers do not detail their data collection and analysis instruments and protocols in sufficient detail for a readers to appreciate what they mean by their results. In particular, what it means to have a misconception – e.g., to give a definitive statement in an interview, or just to select some response on a test as the answer that looked most promising at the time. Clearly we give much more weight to a notion that a learner presents in their own words as an explanation for some phenomenon, than the selection of one option from a menu of statements presented to them that comes with no indication of their confidence in the selection made.
Of particular concern: either the children were asked questions in a second language that they may not have been sufficiently fluent in to fully understand questions or compose clear responses; or none of the misconceptions reported are presented in their original form and they have all been translated by someone (unspecified) of uncertain ability as a translator. (A suitably qualified translator would need to have high competence in both languages and a strong familiarity with the subject matter being translated.)
In the circumstances, Tarhan and colleagues' reported misconceptions are little more than intriguing. In science, the outcome of a study is only informative in the context of understanding exactly how the data were obtained, and how they have been processed. Without that, readers are asked to take a researcher's conclusions on faith, rather than be persuaded of them by a logical chain of argument.
p.s. For anyone who did not know, but wondered: s orbitals are not so-called because they are spherical: the designation derives from a label ('sharp') that was applied to some lines in atomic spectra.
1 To my reading, the publication title 'Research in Science and Technological Education' seems to suggest the journal has two distinct and somewhat disconnected foci, that is:
Research in ( Science ) and ( Technological Education )
And it would be better (that is, most consistently) titled as
Research in Science and Technology Education
{Research in ( Science and Technology ) Education}
or
Research in Scientific and Technological Education
{Research in ( Scientific and Technological ) Education}
but, hey, I know I am pedantic.
2 The table (Table 1.2 in the source) was followed by the following text:
"The first criterion listed is the most fundamental and is generally clear cut as long as the substances present before and after the change are known. If a new substance has been produced, it will almost certainly have different melting and boiling temperatures than the original substance.
The other [criteria] are much more dubious. Some chemical changes involve a great deal of energy being released, such as the example of burning magnesium in air, or even require a considerable energy input, such as the example of the electrolysis of water. However, other reactions may not obviously involve large energy transfers, for example when the enthalpy and entropy changes more or less cancel each other out…. The rusting of iron is a chemical reaction, but usually occurs so slowly that it is not apparent whether the process involves much energy transfer ….
Generally speaking, physical changes are more readily reversible than chemical changes. However, again this is not a very definitive criterion. The idea that chemical reactions tend to either 'go' or not is a useful approximation, but there are many examples of reactions that can be readily reversed…. In principle, all reactions involve equilibria of forward and reverse reactions, and can be reversed by changing the conditions sufficiently. When hydrogen and oxygen are exploded, it takes a pedant to claim that there is also a process of water molecules being converted into oxygen and hydrogen molecules as the reaction proceeds, which means the reaction will continue for ever. Technically such a claim may be true, but for all practical purposes the explosion reflects a reaction that very quickly goes to completion.
One technique that can be used to separate iodine from sand is to warm the mixture gently in an evaporating basin, over which is placed an upturned beaker or funnel. The iodine will sublime – turn to vapour – before recondensing on the cold glass, separated from the sand. The same technique may be used if ammonium chloride is mixed with the sand. In both cases the separation is achieved because sand (which has a high melting temperature) is mixed with another substance in the solid state that is readily changed into a vapour by warming, and then readily recovered as a solid sample when the vapour is in contact with a colder surface. There are then reversible changes involved in both cases:
solid iodine ➝ iodine vapour
ammonium chloride ➝ ammonia + hydrogen chloride
In the first case, the process involves only changes of state: evaporation and condensation – collectively called sublimation. However the second case involves one substance (a salt) changing to two other substances. To a student seeing these changes demonstrated, there would be little basis to infer one is (usually considered as) a chemical change, but not the other. …
The final criterion in Table 1.2 concerns whether bonds are broken and made during a change, and this can only be meaningful for students once they have learnt about particle models of the submicroscopic structure of matter… In a chemical change, there will be the breaking of bonds that hold together the reactants and the formation of new bonds in the products. However, we have to be careful here what we mean by 'bond' …
When ice melts and water boils, 'intermolecular' forces between molecules are disrupted and this includes the breaking of hydrogen 'bonds'. However, when people talk about bond breaking in the context of chemical and physical changes, they tend to mean strong chemical bonds such as covalent, ionic and metallic bonds…
Yet even this is not clear cut. When metals evaporate or are boiled, metallic bonds are broken, although the vapour is not normally considered a different substance. When elements such as carbon and phosphorus undergo phase changes relating to allotropy, there is breaking, and forming, of bonds, which might suggest these changes are chemical and that the different forms of the same elements should be considered different substances. …
A particularly tricky case occurs when we dissolve materials to form solutions, especially materials with ionic bonding…. Dissolving tends to involve small energy changes, and to be readily reversible, and is generally considered a physical change. However, to dissolve an ionic compound such as sodium chloride (table salt), the strong ionic bonds between the sodium and chloride ions have to be overcome (and new bonds must form between the ions and solvent molecules). This would seem to suggest that dissolving can be a chemical change according to the criterion of bond breaking and formation (Table 1.2)."
An ancient iron column: Did "a very thin layer of phosphorus formed, between the rust and the fresh metal and basically stop… it from rustingany more"
What do you need to build a skyscraper?
I was listening to a podcast from the Royal Institution (where Humphrey Davy and Michael Faraday were based). I must confess I had downloaded the 'Recipe for a Skyscraper' episode some time ago but it had been passed over for other titles.
My mistake. In this talk "structural engineer Roma Agrawal delves into the history of the materials that enable immense construction and the developments that have made our structures what they are today. All while noting the accomplishments of key visionary engineers of the past". This proved to be an engaging and fascinating talk.
A 'mega badass engineer'
On her website, Roma Agrawal , "a structural engineer, author and broadcaster, with a physics degree" describes herself as a "mega badass engineer". She is not above being a little mischievous.
The crumbly ages
For example, she has her own take on what historians used to call the 'dark ages', 1
"So, oddly enough, once the Roman empire fell, the use of concrete basically ended for nearly a thousand years, so that we call it the dark ages, or the crumbly ages as I like to call it, because they went back to using slightly older [construction materials], you know, mud and brick and things like that."
Roma Agrawal talking at the Royal Institution
But while the Romans may have championed the use of concrete, the Indians were outperforming them in the production of high quality iron: "The Romans actually used to import Indian steel at the time and they never knew how to make it because that secret was closely guarded…"
Iron is too reactive to be found 'native' but has to be produced by roasting its ores (that contain compounds of iron) with materials that will reduce the iron compounds to iron, and produce, as a by-product, slag – a complex mixtures of substances. The iron produced will contain some slag mixed into the metal unless this is carefully removed. 2
The Delhi column
As an example of the Indian expertise, Roma Agrawal referred to an old iron column near Delhi which "had not rusted" despite having been erected 1500 years ago.3 The column had originally been a stand for a statue of Garuda, the divine winged creature/demigod who acted as the vehicle for Vishnu. Garuda seems to have flown, but the iron column remains.
The (not quite 4) 'rustless wonder' (Srinivasan & Ranganathan, 2013): the Qtub Iron Pillar
Lord Vishnu on his mount Garuda (wood carving). It is thought the iron pillar near Delhi once supported a statue of Garuda.
(Image by waradet from Pixabay)
Iron is the main constituent of alloys known as steels, and by mixing other elements (principally, but not only, carbon) with iron it is possible to create steels with various properties, including corrosion resistance. 2 But iron itself readily rusts. The rust formed when iron corrodes is permeable and crumbly, exposing the unreacted metal beneath, which in turn forms rust that again fails to protect the iron beneath it. So, over time, a piece of iron can simply 'rust away' as the reacted material will simply fall off, or be eroded by weather.
Yet this iron column, erected around the time of the final collapse of the Roman Empire, seems to have survived throughout 'the crumbly ages' and through to the present day. Although, it is not that it never started rusting 4, but rather,
"it did initially rust, but then because of the climate in Delhi, the phosphorus, a very thin layer of phosphorus formed, between the rust and the fresh metal and basically stopped it from rusting any more…"
Roma Agrawal talking at the Royal Institution
Corrosion (as with tarnishing) is a generic term. Corrosion leads to structural damage to metal objects (whereas tarnishing is a surface effect).
Rusting is specific to iron as it refers to the material produced when iron corrodes – i.e., rust.
Unreactive phosphorus?: An alternative conception
Roma Agrawal's claim seems incredible to a chemist or science teacher because phsophorus is a very reactive element, and a very reactive element does not seem a good choice of material to protect iron from reacting! Even if the phosphorus did not itself react with the iron and so corrode it, it would soon react with air. In the laboratory, some forms of phosphorus can burst into flames spontaneously, suggesting it is very unlikely to remain intact very long exposed to the elements in India. Certainly not many centuries.
Sacrificial elements
Now, sometimes a more valuable metal is protected by connecting it physically to a more reactive but less valuable metal which preferentially corrodes. As the metals are in electrical contact, the one that loses electrons and releases cations more readily reacts first. The metal allowed to corrode is called a 'sacrificial' metal. For example, bars of sacrificial metal may be dangled from piers or oil rigs to protect the structural metal. The sacrificial metal will slowly 'dissolve' away into the sea 5 – but not that slowly that it would not need replacing for over a millennium. In any case, phosphorus is a non-metal, where the sacrificial element of the pair needs to be the more electropositive. So, there is no helpful explanation there.
Alumina – when tarnishing prevents corrosion
Aluminium is a more reactive metal than iron, yet does not readily undergo substantive corrosion. This is because the surface of an aluminium object readily reacts with oxygen from the air to form a layer of aluminium oxide (alumina). This then protects the aluminium because the alumina formed is a fairly inert substance (unlike the highly reactive phosphorus), and it forms an impermeable layer (preventing oxygen from the air reaching the metal beneath).
Any layer that were to form on iron protect it from rusting also needs to be impermeable and relatively inert. Unlike reactive phosphorus.
Phosphorus would not protect iron
Phosphorus is a fire hazard that burns to produce toxic fumes. In the laboratory, the direct reaction of iron and phosphorus usually requires heating to initiate reaction. Without active heating, the rate of reaction would be too low for a useful laboratory process. However, a very low rate of reaction would not prevent reaction over the centuries since the iron column was erected.
Even if phosphorus was able to form a layer that coated over the iron, using it as a means to prevent corrosion would be like fireproofing a wooden building by coating it with petroleum jelly (e.g., Vaseline). [A correspondent to the British Dental Journal (Brewer, 2017) warned of "the death of a bedbound patient who smoked following application of E45 cream…a paraffin-based product, the residue of which can act as an accelerant when ignited". Smoking kills. And even more rapidly if you smother yourself in flammable oil products prior to lighting up.]
So, it seems we have a mystery.
Or, Roma Agrawal simply got it wrong.
Or, perhaps, more likely, when Roma Agrawal refers to a 'layer of phosphorus' she is using the term loosely, and is actually referring to something else. That is, the protective layer may contain one or more phosphorus compounds, but not phosphorus – just as a layer of the unreactive aluminium compound alumina stops corrosion, although aluminium itself is reactive. Is this distinction just being pedantic? Not to a science educator.
An elementary misconception
The claim that a layer of phosphorus could protect iron from corrosion is therefore not credible to the scientifically literate, but might seem perfectly reasonable to a person with limited science background. One of the great challenges of learning chemistry is making sense of the set of ideas that:
the compound of an element is a completely different substance to the element itself
the properties of compounds are often quite different (sometimes contrastingly so) to those of the elements the compound was formed from
although the compound does not behave like the elements, and does not 'contain' the elements in any straightforward way, there is a sense in which something of the elements persists in (and so the element may be recovered from) the compound.
So, sodium is a reactive metal that burns in air, and chlorine is a green, toxic, choking gas; and both should be avoided unless taking very careful precautions; yet they react, very energetically, to give the relatively unreactive compound sodium chloride – which people readily use in cooking, and to season their food, and to dissolve in water to gargle with, or to soak tired feet. Chlorine would destroy the lining of your throat. Yet sodium chloride solution (despite its chlorine 'constituent') will help ease a sore throat! Still, the sodium chloride has the potential to be 'separated' into the elements with their dangerous properties intact.
Although the distinction between elements and compounds is a lot easier to understand once students learn about molecules and atoms (at least, if avoiding the alternative conception that compounds comprise of molecules and elements comprise of atoms!) this topic is fraught with complications and hang-overs from historical ideas about atoms (Taber, 2003).
If not a layer of phosphorus?
The chemist or science teacher hearing about a protective 'layer of phosphorus' preventing rusting will immediately thinks this is not viable…but a compound of phosphorus might well have the necessary properties. Indeed, generally, the more reactive the elements, the more stable the compounds they form when reacting.
It seems that the layer that formed on the iron column contains the phosphorus compoundiron hydrogen phosphate hydrate (FePO4·H3PO4·4H2O),
"Several theories have been postulated regarding corrosion resistance of the Delhi iron pillar. Some of those refer to the inherent nature of the construction material, such as the selection of pure iron, presence of slag particles and slag coatings, surface finishing using mechanical operation, phosphate film formation, or the Delhi's climate…
Earlier studies have delineated the formation of crystalline iron hydrogen phosphate hydrate (FePO4·H3PO4·4H2O), 𝛼-, 𝛾-, 𝛿-FeOOH and magnetite in the case of Delhi iron pillar"
Yet this critical, and somewhat counter-intuitive, distinction between elements qua elements and elements as in some sense 'components' (or 'ingredients') of compounds needs to be acquired. Novices have to learn this. A common alternative conception is to assume that the properties of elements are carried over into their compounds.
So, if students hear that
phosphorus is essential in our diet, and that
phosphorus is important for healthy bones and teeth,
they can draw the obvious and reasonable conclusion – that phosphorus must be a pretty innocuous substance as it is part of our bodies and we eat it quite safely in our food. Actually, we need compounds of phosphorus in our food to allow our metabolisms to build and repair tissues that contain phosphorus compounds – and anyone misguided enough to try to eat any actual (elemental) phosphorus risks a nasty burn.
In conclusion, as a science graduate, Roma Agrawal presumably appreciates the key distinction between (i) elements as substances and (ii) elements as chemically combined components of other substances, and, as a structural engineer knowledgeable about different material properties, is using 'layer of phosphorus' as a shorthand for a layer of material that includes one or more phosphorus compounds.
That is fine as long as those hearing her talk appreciate that. Another scientist would likely automatically hear 'phosphorus layer' as meaning 'phosphorus compound containing layer'. A science teacher, however, might suspect that the reference to how "a very thin layer of phosphorus formed, between the rust and the fresh metal and basically stopped it from rusting" is likely to be misunderstood, and indeed to mislead, some listening to the podcast.
Minding your Ps…
One of the sources referred to reported how:
"P is found present in slag whereas the presence of P in iron was not detected within the limit of the analytical techniques used in this study. On the basis of this result, we speculate application of lime and other basic compounds during the iron making process which would have led to the transfer P to slag."
P is the symbol for phosphorus, the element. However, someone with a sufficient scientific background appreciates from the context that references to
P found in slag
P in iron
transfer [of] P to slag
cannot refer to P as phosphorus the element, but rather some compound or compounds of phosphorus. As a reactive element, phosphorus is not found native and so would not be present (as an element) in the raw materials and, in any case, could certainly not survive (as an element) the high temperature conditions of the processes of iron smelting. Therefore the relevant 'context' for reinterpreting 'P' as not standing for the element itself would be any set of circumstances other than the special conditions where phosphorus can be safely stored without risk of reaction.
This is the prerequisite background knowledge that prevents an audience member misinterpreting what must be meant by a "thin layer of phosphorus [sic]" protecting an exposed iron column – as it cannot possibly refer to a thin layer of [actual, elemental] phosphorus.
Sources cited
Anantharaman, T. R. (1997). The iron pillar at Delhi. In S. Ranganathan (Ed.), Iron and Steel Heritage of India (pp. 1-28). Indian Institute of Metals and Tata Steel.
Brewer, E. Patient safety: Paraffin-based products. British Dental Journal223, 620 (2017). https://doi.org/10.1038/sj.bdj.2017.936
Dwivedi, D., Mata, J. P., Salvemini, F., Rowles, M. R., Becker, T., & Lepková, K. (2021). Uncovering the superior corrosion resistance of iron made via ancient Indian iron-making practice. Scientific Reports, 11(1), 4221. doi:10.1038/s41598-021-81918-w
Falk, S. (2020). The Light Ages. A Medieval journey of discovery. Allen Lane.
Srinivasan, S., & Ranganathan, S. (2013). Minerals and Metals Heritage of India. Bangalore: National Institute of Advanced Studies.
1 A simplistic view was that advancing civilisation underwent something of a relapse during the middle ages, until the gains of the classical age (the Greeks, the Romans) were rediscovered in the Enlightenment. Thus, the term 'dark ages' applied to the 'middle ages'.
There were no dark ages: as a matter of fact, they are all dark
with apologies to Pink Floyd
That is clearly a great simplification, and ignores many medieval achievements, as well as being a rather Eurocentric view. Some historians have been seeking to redress this impression: for example, Seb Falk (2020) has renamed this period 'the light ages'.
2 To suggest that steel deliberately contains impurities added to iron could give the impression that iron artefacts are made of purer materials than steel ones. This is misleading. Basic iron smelting produces iron that is impure (sometimes known as 'pig iron') and which can contain quite high levels of impurities. Pig iron typically has a high level of carbon – more than is usually used in steels.
Wrought iron is produced by physical working of pig iron which expels much of the slag content, giving purer iron. Wrought iron has long been widely used in structures, but still does not have a high level of purity.
Alloys are mixtures of different metals, or of metallic elements with other elements. 'Metal' here is ambiguous as it can refer to
an electropositive element (the usual meaning in chemistry) or
a material with certain properties (the usual meaning in engineering) – i.e., malleable, ductile, high electrical and thermal conductivities, lustre, sonorous.
Steels are metals in the 'materials' sense, but 'chemically' are mixtures of the metallic element iron with other elements.
As the properties of steels are sensitive to the levels of other elements, making steel requires using high quality iron that has been treated to remove most of the impurities. This is similar to doping a semiconductor such as silicon to produce electronic components. Very pure silicon is needed as a starting point, so that just the right amount of a specific dopant can be added.
The Indian iron manufacture of Roman times tended to produce iron with a significant phosphorus content.
3 The column was made of wrought iron,
"The forging of wrought iron seems to have reached its zenith in India in the first millennium AD. The earliest large forging is the famous iron pillar with a height of over 7 m and weight of about 6 tons at New Delhi ascribed to Chandragupta Vikramaditya 400- 450 CE… the absence of corrosion is linked to the composition, the high purity of the wrought iron and the phosphorus content and the distribution of slag."
Srinivasan & Ranganathan, 2013
4 The lack of rusting may have been exaggerated,
"The first impression in 1961 was that the portion of the Pillar below the earth was "superficially rusted". However, on detailed examination, the buried portion of the Pillar was found covered with thick crusts of rust and, in fact, copious rust scales could be collected, ranging in thickness from a few millimeters (mm) to no less than 15 mm in some portions. Further, the bulbous base of the Pillar was found riddled with numerous cavities and hollows caused by deep corrosion and mineralization of the iron.
Anantharaman, 1997
Even so, the survival of an iron column exposed to weathering for this length of time is still worthy of note.
5 I thought I should put 'dissolve' into 'scare quotes' here. Corrosion is a chemical change, whereas dissolving refers to what is generally considered a physical change. As the sacrificial metal reacts, it releases cations into solution in the sea, in much the same was as, say, dissolving salt releases sodium ions when common salt is added to water. The metal reacts and enters solution – dissolves, if you are comfortable with that word in this context.
"After a lecture on cosmology and the structure of the solar system, James [William James] was accosted by a little old lady.
'Your theory that the sun is the centre of the solar system, and the earth is a ball which rotates around it has a very convincing ring to it, Mr. James, but it's wrong. I've got a better theory,' said the little old lady.
'And what is that, madam?' inquired James politely.
'That we live on a crust of earth which is on the back of a giant turtle.'
Not wishing to demolish this absurd little theory by bringing to bear the masses of scientific evidence he had at his command, James decided to gently dissuade his opponent by making her see some of the inadequacies of her position.
'If your theory is correct, madam,' he asked, 'what does this turtle stand on?'
'You're a very clever man, Mr. James, and that's a very good question,' replied the little old lady, 'but I have an answer to it. And it's this: The first turtle stands on the back of a second, far larger, turtle, who stands directly under him.'
'But what does this second turtle stand on?' persisted James patiently.
To this, the little old lady crowed triumphantly,
'It's no use, Mr. James – it's turtles all the way down.'
Ross, 1967, iv
"The Hindoos [sic] held the earth to be hemispherical, and to be supported like a boat turned upside down upon the heads of four elephants, which stood on the back of an immense tortoise. It is usually said that the tortoise rested on nothing, but the Hindoos maintained that it floated on the surface of the universal ocean. The learned Hindoos, however, say that these animals were merely symbolical, the four elephants meaning the four directions of the compass, and the tortoise meaning eternity." (The Popular Science Monthly, March, 1877; image via Wikipedia)
It's metaphors all the way down
A well-known paper in the journal 'Cognitive Science' is entitled 'The metaphorical structure of the human conceptual system' (Lakoff & Johnson, 1980). What the authors meant by this was that metaphor, or perhaps better analogy, was at the basis of much of our thinking, and so our language.
This links to the so-called 'constructivist' perspective on development and learning, and is of great significance in both the historical development of science and in science teaching and learning. Consider some of the concepts met in a science course (electron, evolution, magnetic flux, hysteresis, oxidation state, isomerism…the list is enormous) in comparison to the kind of teaching about the world that parents engage in with young children:
That is a dog
That is a tree
That is round
This is hot
This is aunty
etc.
Pointing out the names of objects is not a perfect technique – just as scientific theories are always underdetermined by the available data (it is always possible to devise another scheme that fits the data, even if such a scheme may have to be forced and convoluted), so the 'this' that is being pointed out as a treecould refer to the corpse of trees, or the nearest branch, or a leaf, or this particular species of plant, or even be the proper name of this tree, etc. 1
Pointing requires the other person to successfully identify what is being pointed at (Images by Joe {background} and OpenClipart-Vectors {figures} from Pixabay)
But, still, the 'this' in such a case is usually more salient than the 'this' when we teach:
This is an electron
This is reduction
This is periodicity
This is electronegativity
This is a food web
This is a ᴨ-bond
This is a neurotransmitter
etc.
Most often in science teaching we are not holding up a physical object or passing it around, but offering a 'this' which is at best a model (e.g., of a generalised plant cell or a human torso) or a complex linguistic structure (a definition in terms of other abstract concepts) or an abstract representation ('this', pointing to a slope of an a graph, is acceleration; 'this', pointing to an image with an arrangement of a few letters and lines, is a transition state…).
So, how do we bridge between the likes of dogs and trees on one hand and electrons and the strong nuclear force on the other (so to speak!)? The answer is we build using analogy and we talk about those constructions using a great deal of metaphor.2 That is, we compare directly, or indirectly, with what we can experience. This refers to relationships as well as objects. We can experience being on top of, beneath, inside, outside, next to, in front of, behind, near to, a long way from (a building, say – although hopefully not beneath in that case), and we assign metaphorical relationships in a similar way to refer to abstract scenarios. (A chloroplast may be found in a cell, but is sodium found in (or on) the periodic table? Yes, metaphorically. And potassium is found beneath it!)
In a wall, the bricks on the top layer are supported by the bricks in the layer beneath – but those are in turn supported by those beneath them.
In building, we have to start at the foundations, and build up level by level. The highest levels are indirectly supported by the foundations.
(Image by OpenClipart-Vectors from Pixabay)
In science, we initially form formal concepts based on direct experience of the world (including experience mediated by our interventions, i.e., experiments), and then we build more abstract concepts from those foundational concepts, and then we build even more abstract concepts by combining the abstract ones. In the early stages we refine 'common sense' or 'life-world' categories into formal concepts so we can more 'tightly' (and operationally, through standard procedures) define what count as referents for scientific terms (Taber, 2013). So, the everyday phenomenon of burning might be reconceptualised as combustion: a class of chemical reactions with oxygen.
This is not just substituting a technical term, but also a more rigid and theoretical (abstract) conceptualisation. So, in the 'life-world' we might admit the effects of too much sunshine or contact with a strong acid within the class of 'burning' by analogy with the effect of fire (it hurts and damages the skin); but the scientific categorisation is less concerned with direct perception, and more with explanation and mechanism. So, iron burning in chlorine (in the absence of any oxygen) is considered combustion, but an acid 'burn' is not.
This is what science has done over centuries, and is also what happens in science education. So, one important tool for the teacher is concept analysis, where we check which prerequisite concepts need to be part of a student's prior learning before we introduce some new concept that is built upon then (e.g., do not try to teach mass spectroscopy before teaching about atomic structure, and do not teach about atomic structure before introducing the notion of elements; do not try to teach about the photoelectric effect to someone who does not know a little about the structure of metals and the nature of electromagnetic radiation.)
This building up of abstract concepts, one on another, is reflected in the density of metaphor we find in our language. (That is a metaphorical 'building', metaphorically placed one upon another, with a metaphorical 'density' which is metaphorically 'inside' the language and which metaphorically 'reflects' the (metaphorical) building process! You can 'see' (a metaphor for understand) just how extensive (oops, another metaphorical reference to physical space) this is. Hopefully, the (metaphorical) 'point' is (metaphorically) 'made', and so I am going to stop now, before this gets silly. 3
A case study of using language in science communication: the death of stars
Rather, I am going to discuss some examples of the language used in a single science programme, a BBC radio programme/podcast in the long-running series 'In Our Time' that took as its theme 'The Death of Stars'. The programme was hosted by Melvyn Bragg, and The Lord Bragg's guests were Professors Carolin Crawford (University of Cambridge), the Astronomer Royal Martin Rees (University of Cambridge) and Mark Sullivan (University of Southampton). This was an really good listen (recommended to anyone with an interest in astronomy), so I have certainly not picked it out to be critical, but rather to analyse the nature of some of the language used from the perspective of how that language communicates technical ideas.
An episode of 'In Our Time' on 'The Death of Stars' "The image above is of the supernova remnant Cassiopeia A, approximately 10,000 light years away, from a once massive star that died in a supernova explosion that was first seen from Earth in 1690"
A science teacher may be familiar with stars being born, living, and dying – but how might a young learner, new to astronomical ideas, make sense of what was meant?
Now there is already a point of interest in the episode title. Are stars really the kind of entities that can die? Does this mean they are living beings prior to death?
There are a good many references in the talk of these three astronomers in the episode that suggests that, in astronomy at least, stars do indeed live and die. That is, this does not seem to be consciously used as a metaphor – even if the terminology may have initially been introduced that way a long time ago. The programme offered so much material on this theme, that I have separated it out for a post of its own:
"So, in the language of astronomy, stars are born, start young, live; sometimes living alone but sometimes not, sometimes have complicated lives; have lifetimes, reach the end of their lives, and die, so, becoming dead, eventually long dead; and indeed there are generations of stars with life-cycles."
In this post I am going to consider some of the other language used.
Making the unfamiliar familiar
Language is used in science communication to the public, as it is in teaching, to introduce abstract technical ideas in ways that a listener new to the subject can make reasonable sense of. The constructivist perspective on learning tells us that meaning is not automatically communicated from speaker (or author or teacher) to listener (or reader or student). Rather, a text (spoken or written, or even in some other form – a diagram, a graph, a dance!) has to be interpreted, and this relies on the interpretive resources available to the learner. 4 The learner has to relate the communication to something familiar, and the speaker can help by using ways to make the new idea seem like something already familiar.
This is why it it is so common in communicating science to simplify, to use analogies and similes, to gesture, to use anthropomorphism and other narrative devices. There was a good deal of this in the programme, and I expect I have missed some examples. I have divided my examples into
simplifications: where some details are omitted so not to overburden the listener;
anthropomorphism: where narratives are offered such that non human entities are treated as if sentient actors, with goals, that behave deliberately;
analogies where an explicit comparison is made to map a familiar concept onto the target concept being introduced; 5
similes and metaphors: that present the technical material as being similar to something familiar and everyday.
Simplification
Simplification means ignoring some of the details, and offering a gloss on things. The details may be important, but in order to get across some key idea it is introduced as a simplification. Progress in understanding would involve subsequently filling in some details to develop a more nuanced understanding later.
In teaching there are dangers in simplification, as if the simplified idea is readily latched onto (e.g., there are two types of chemical bonds: ionic and covalent) it may be difficult later to shift learners on in their thinking. This may mean that there is a subtle balance to be judged between
giving learners enough time to become comfortable with the novel idea as introduced in a simplified form,
and
seeking to develop it out into a more sophisticated account before it become dogma.
In a one-shot input, such as a public lecture or appearance in the media, the best a scientist may be able to do is to present an account which is simple enough to understand, but which offers a sense of the science.
Simplification: all elements/atoms are formed in stars
When introducing the 'In Our Time' episode, Lord Bragg suggested that
"…every element in our bodies, every planet, was made in one of those stars, either as they burned, or as they exploded".
Clearly Melvyn cannot be an expert on the very wide range of topics featured on 'In our time' but relies on briefing notes provided by his guests. Later, in the programme he asks Professor Rees (what would clearly be considered a leading question in a research context!) "Is the sun recycled from previous dead stars?"
"Yes it is because we believe that all pristine material in the universe was mainly just hydrogen and helium, and all the atoms we are made of were not there soon after the big bang. They were all made in stars which lived and died before our solar system formed. And this leads to the problem of trying to understand more massive stars which have more complicated lives and give rise to supernovae…
The cloud from which our solar system formed was already contaminated by the debris, from earlier generations of massive stars which had lived and died more than say five billion years ago so we're literally the ashes of those long dead stars or if you are less romantic we're the nuclear waste from the fuel that kept those old stars shining."
Prof. Martin Rees
There is a potential for confusion here.
"…all the atoms we are made of were not there soon after the big bang. They were all made in stars which lived and died before our solar system formed…"
seems to be meant to convey something like
not all the atoms we are made of were there soon after the big bang. [Some were, but the rest/others] were all made in stars which lived and died before our solar system formed…
A different interpretation (i.e., that all atoms/elements are formed in stars) might well be taken, given Lord Bragg's introductory comments.
Professor Rees referred to how "…the idea that the elements, the atoms we are made of, were all synthesised in stars…" first entered scientific discourse in 1946, due to Fred Hoyle, and to
"this remarkable discovery that we are literally made of the ashes of long dead stars"
Prof. Martin Rees
Before the first star formation, the only elements present in the universe were hydrogen and helium (and some lithium) and the others have been produced in subsequent high energy nuclear processes. Nuclear fusion releases energy when heavier nuclei are formed from fusing together lighter ones, up to iron (element 56).
Forming even heavier elements requires an input of energy from another source. It was once considered that exploding stars, supernovae, gave rise to the conditions for this, but recently other mechanisms have been considered: and Prof. Sullivan described one of these:"we think these combining neutron stars are the main sites where heavy elements like strontium or plutonium, perhaps even gold or silver, these kinds of elements are made in the universe in these neutron stars combining with each other".
A human body includes many different elements, though most of these in relatively small amounts. Well represented are oxygen, carbon, calcium, and nitrogen. These elements exist because of the processes that occur in stars. However, hydrogen is also found in 'organic' substances such as the carbohydrates, proteins, and fats found in the human body. Typically the molecules of these substances contain more hydrogen atoms than atoms of carbon or any other element.
substance
formula
glucose (sugar)
C6H12O6
leucine (amino aid)
C6H13NO2
leukotriene B4 (inflammatory mediator)
C20H32O4
thymine (nucleobase)
C5H6N2O2
adreneline (hormone)
C9H13NO3
insulin (hormone)
C257H383N65O77S6
cholesterol (lipid)
C27H46O
cobalamin (vitamin B12)
C63H88CoN14O14P
formulae of some compounds found in human bodies
The body is also said to be about 60% water, and water has a triatomic molecule: two hydrogen atoms to one of oxygen (H2O). That is, surely MOST of "the atoms we are made of" are hydrogen, which were present in the universe before any stars were 'born'.
So, it seems here we have a simplification ("every element in our bodies…was made in one of those stars, either as they burned, or as they exploded"; "atoms we are made of … were all made in stars") which is contradicted later in the programme. (In teaching, it is likely the teacher would feel the need to draw the learner's attention to how the more detailed information was actually developing an earlier simplification, and not leave a learner to work this out for themselves.)
Simplification: mass is changed into energy
Explaining nuclear fusion, Prof. Crawford suggested that
"Nuclear fusion is when you combine nuclei of elements to form heavier elements, and when you do this there is a loss of mass, which is converted to energy which provides the thermal pressure and that is what counteracts the gravity and stalls the gravitational collapse."
Prof. Carolin Crawford
This seems to reflect a common alternative conception ('misconception') that, in nuclear processes, mass is converted to energy. This is often linked to Albert Einstein's famous equation E = mc2.
Actually, as discussed before here, this is contrary to the scientific account. The equation presents an equivalence between mass and energy, but does not suggest they can be inter-converted. In nuclear fusion, the masses of the new nuclei are very slightly less than the masses of the nuclei which react to form them (the difference is known as the mass defect), but this is because this omits some details of the full description of the process. If the complete process is considered then there is no loss of mass, just a reconfiguration of where the mass can be located.
Although the 4He formed has slightly less mass than four 1H; the positrons, neutrinos and gamma rays produced all have associated (energy and) mass, so that overall there is conservation of mass.
This is a bit like cooking some rice, and finding that when the rice is cooked the contents of the saucepan had slightly less weight than when we started – as some of the water we began with has evaporated and is no longer registering on our balance. In a similar way, if we consider everything that is produced in the nuclear process, then the mass overall is conserved.
As E = mc2 can be understood to tell us that mass follows the energy (or vice versa) we should expect mass changes (albeit very, very small ones) whenever work is done: when we climb the stairs, or make a cup of tea, or run down a mobile 'phone 'battery' (usually a cell?) – but mass is always conserved when we consider everything involved in any process (such as how the 'phone very, very slightly warms -and so very marginally increases the mass of – the environment).
Despite the scientific principles of conservation of energy and conservation of mass always applying when we make sure we consider everything involved in a process, I have mentioned on this site another example of an astrophysicist suggesting mass can be converted into energy: "an electron and the positron, and you put them together, they would annihilate…they would annihilate into energy" (on a different episode of 'In Our Time': come on Melvyn…we always conserve mass).
Perhaps this is an alternative conception shared by some professional scientists, but I wonder if it sometimes seems preferably to tell the "mass into energy" narrative because it is simpler than having to explain the full details of a process – which is inevitably a more complex story and so will be more difficult for a novice to take in. After all, the "mass into energy" story is likely to seem to fit with a listener's interpretive resources, as E=mc2is such a famous equation that it can be assumed that it will be familiar to most listeners, even if only a minority will have a deep appreciation of how the equivalence works.
Anthropomorphic narratives
In science learning, anthropomorphism is (to borrow a much used metaphor) a double edged sword that can cut both ways. Teachers often find that using narratives that present inanimate entities which are foci of science lessons as if they are sentient beings with social lives and motivations engages learners and triggers mental images that a student can readily remember. So, students may recall learning about what happens at a junction in a circuit in terms of a story about an electron that had to make a decision about which way to go – perhaps she took one branch while her friend tried another? They recall that covalent bonds are the 'sharing' of electrons between atoms, and indeed that atoms want, perhaps even need, to fill their electron shells, and if they manage this they will be happy.
The danger here is that for many students such narratives are not simply useful ways to get them thinking about the science concepts (weak anthropomorphism) but seem quite sufficient as the basis of explanations (strong anthropomorphism) – and so it may become difficult to shift them towards more canonical accounts. They will then write in tests that chemical reactions occur because the atoms want full shells, or that only one electron can be removed from a sodium atom because it then has a full shell. (That is, a force applied to an electron in an electric field is seen as irrelevant compared with the atom's desires. These are genuine examples reflecting what students have said.)
However, there is no doubt that framing scientific accounts within narratives which have elements of human experience as social agent does seem to help make these ideas engaging and accessible. Some such anthropomorphism is explicit, such as when gas molecules (are said to) like to move further apart, and some is more subtle by applying terms which would normally be used in relation to human experiences (not being bothered; chomping; escaping…).
What gravity did next
Consider this statement:
"All stars have the problem of supporting themselves against gravitational collapse, whether that is a star like our sun which is burning hydrogen into helium, and thus providing lots of thermal pressure to stop collapse, or whether it is a white dwarf star, but it does not have any hydrogen to burn, because it is an old dead star, fading away, so it has another method to stop itself collapsing and that is called degeneracy pressure. So, although a white dwarf is very dense, gravity is still trying to pull that white dwarf to be even denser and even denser."
Prof. Mark Sullivan
There is an explicit anthropomorphism here: from the scientific perspective gravity is nottrying to pull the white dwarf to be even denser. Gravity does not try to do anything. Gravity is not a conscious agent with goals that it 'tries' to achieve.
However, there is also a more subtle narrative thread at work – that a star has the problem of supporting itself, and it seems that when its first approach to solving this problem fails, it has a fallback method "to stop itself collapsing". But the star is just a complex system where various forces act and so processes occur. A star is not the kind of entity that can have a problem or enact strategies to achieve goals. Yet, this kind of language seems to naturally communicate abstract ideas though embedding them within an accessible narrative.
Star as moral agents
In the same way, a star is not the type of entity which can carry out immoral acts, but
"A star like our sun will never grow in mass, because it lives by itself in space. But most stars in the universe don't live by themselves, they live in what are called binary systems where you have two stars orbiting each other, rather than just the single star that we have as the sun. They are probably born with different masses, and so they evolve at different speeds and one will become a white dwarf. Now the physics is a bit complicated, but what can happen, is that that white dwarf can steal material from its companion star."
Prof. Mark Sullivan
The meaning here seems very clear, but again there are elements of using an anthropomorphic narrative. For one star to steal material from another star, that material would have to first belong to that other star, and its binary 'partner' would have to deliberately misappropriate that material knowing it belongs to its 'neighbour' (indeed, "companion").
Such a narrative breaks down on analysis. If we were to accept that the matter initially belongs to the first star (leaving aside for the moment what kind of entities can be considered to own property) then given that the material in a star got to be there through mutual gravitational attraction, the only obvious basis for ownership is that that matter has become gravitationally bound as part of that star.
If we have no other justification than that (as in the common aphorism, possession is nine points of the law), then when the material is transferred to another star because its gravitational field gives rise to a net force causing the matter to become gravitationally bound to a different star, then we should simply consider ownership to have changed. There is no theft in a context where ownership simply depends on pulling with the greater force. Despite this, we readily accept an analogy from our more familiar human social context and understand that (in a metaphorical sense) one star has stolen from another!
Actually, theft can only be carried out by moral agents – those who have capacity to intend to deprive others of their property
"A person [sic] is guilty of theft if he dishonestly appropriates property belonging to another with the intention of permanently depriving the other of it; and "thief" and "steal" shall be construed accordingly"
U.K. Theft Act 1968
Generally, these days (though this was not always so), even non-human animals are seldom considered capable of being responsible for such crimes. Admittedly, the news agency Reuters reported that as recently as 2008 "A Macedonian court convicted a bear of theft and damage for stealing honey from a beekeeper", but this seems to have been less a judgement on the ability of the bear (convicted it its absence) to engage in ethical deliberation, and more a pragmatic move that allowed the bee-keeper to be awarded criminal damages for his losses.
But, according to astronomers, stars are not only involved in the petty larceny of illicitly acquiring gas, but observations of exoplanets suggests some stars may even commit more daring, large-scale, heists,
"fairly small rocky planets two or three times the mass of the earth, in quite tight orbits around their star and you can speculate that they were once giant planets like Jupiter that have had the outer gassy layers blasted off and you are left with the rocky core, or maybe those planets were stolen from another star that got too close"
Prof. Carolin Crawford
A ménage à trois?
And there were other suggestions of anthropomorphism. It is not only stars that "don't live by themselves" in this universe,
"Nickel-56 [56Ni] is what's called an iron peak element, so it lives with iron and cobalt on the periodic table…"
Prof. Mark Sullivan
And, it is not only gravity which seems to have preferences:
"And like Mark has described with electrons not wanting to be squeezed, you have neutron degeneracy pressure. Neutrons don't like to be compressed, at some point they resist it."
Prof. Carolin Crawford
Neither electrons nor neutrons actually have any preferences: but this is an anthropomorphic metaphor that efficiently communicates a sense of the natural phenomena. 'Resist' originally had an active sense as in taking a stand, but today would not necessarily be understood that way. Wanting and liking (or not wanting and not liking), however, strictly only refer to entities that can have desires and preferences.
Navigating photons
Professor Rees explained why some imploding stars are not seen as very bright stars that fade over years, but rather observed through extremely intense bursts of high energy radiation that fade quickly,
"The energy in the form of ordinary photons, ordinary light, that's arisen in the centre of a supernova, diffuses out and takes weeks to escape, okay, but if the star is spinning, then it will be an oblate spheroid, it will have a minor axis along the spin axis, and so the easy way out is for the radiation not to diffuse through but to find the shortest escape route, which is along the spin axis, and I mention this because gamma ray bursts are … when a supernova occurs but because the original star was sort of flattened there is an easy escape route and all the energy escapes in jets along the spin axis and so instead of it diffusing out over a period of weeks, as it does in a supernova, it comes out in a few seconds."
Prof. Martin Rees
Again, the language used is suggestive. Radiation is not just emitted by the star, but 'escapes' (surely a metaphor?). The phrasing "an easy way out" implies something not being difficult. Inanimate entities like photons do not actually (literally) find anything difficult or easy. Moreover, the radiation might "find the shortest escape route": language that does not reflect a playing out of physical forces but an active search – only a being able to seek can find. Yet, again, the language supports an engaging narrative, 'softening' the rather technical story by subtly reflecting a human quest.
Professor Rees also referred to how,
"when those big stars face a crisis they blow off their outer layers"
Prof. Martin Rees
again using phrasing which seems to present the stars as deliberate actors – they actively "blow off" material when they "face a crisis". A crisis is (or at least was originally) a point where a decision needs to be made. A star does not reach the critical point where it reluctantly decides it needs to shed some material – but rather is subject to changing net forces as the rate of heat generation from nuclear processes starts to decrease.
A sense of anthropomorphic narrative also attaches to Professor Crawford's explanation of how more massive stars process material faster,
"…more massive stars … actually have shorter lifetimes …they have to chomp through their fuel supply so furiously that they exhaust it more rapidly
Prof. Carolin Crawford
'Chomping', a term for vigorous eating (biting, chewing, munching), is here a metaphor, as a star does not eat – as pointed out in the companion piece, nutrition is a characteristics feature of living things, but does not map across to stars even if they are described as being born, living, dying and so forth. To be furious is a human emotional response: stars may process their remaining hydrogen quickly, but there is no fury involved. Again, though, the narrative, perhaps inviting associated mental imagery, communicates a sense of the science.
Laid-back gas
Another example of anthropomorphism was
"…if you have a gas cloud that's been sitting out in space for billions of years and has not bothered to contract because it's been too hot or it's too sparse…"
Prof. Carolin Crawford
This is an interesting example, as Prof. Crawford explicitly explains here that the gas cloud has not contracted because of the low density of material (so weak gravitational forces acting on the particles) and/or the high temperature (so the gas comprises of energetic, so fast moving, particles), so the suggestion that the material cannot be bothered (implication: that the 'cloud' operates as a single entity, and is sentient if perhaps a little lazy) does not stand in place of a scientific explanation, but rather simply seems to be intended to 'soften' (so to speak) the technical nature of the language used.
Analogy
An analogy goes beyond a simile or metaphor because there is some kind of structural mapping to make it explicit in what way or ways the analogue is considered to be like the target concept. 5 (Such as when explaining mass defect in relation to the material lost from the saucepan when cooking rice!)
A potential teaching analogy to avoid alternative conceptions about mass defect in nuclear processes
So, Prof. Rees suggests that scientists can test their theories about star 'life cycles' by observation, even though an individual star only moves through the process over billions of years, and uses an analogy to a more familiar everyday context:
"We can test our theories, not only because we understand the physics, but because we can look at lots of stars. It is rather like if you had never seen a tree before, and you wandered around in a forest for a day, you can infer the life cycles of trees, you'd see saplings and big trees, etcetera. And so even though our lifetime is minuscule compared to the lifetime of a stable star, we can infer the population and life cycles of stars observationally and the theory does corroborate that fairly well."
Prof. Martin Rees
This would seem to make the basis of a good teaching analogy that could be discussed with students and would likely link well with their own experiences.
The other explicit analogy introduced by Prof. Rees is one well-known to physics teachers (sometimes in an ice-skater variant),
"If a contracting cloud has even a tiny little bit of spin, if it is rotating a bit, then as it contracts, then just like the ballerina who pulls in her arms and spins faster, then the contracting cloud will start to spin faster…"
Prof. Martin Rees
Stellar similes
I take the difference between a simile and a metaphor as the presence of an explicit marker (such as '…as…',…like…') to tell the listener/reader that a comparison is being made – so 'the genome is the blueprint for the body' would be a metaphor, where 'the genome is like a blueprint for the body' would be a simile.
As if a black hole cuts itself off
So, when Professor Rees describes how a massive black hole forms, he uses simile (i.e., "…as if were…"),
"So, if a neutron star gets above that mass, then it will compress even further, and will become a black hole – it will go on contracting until it, as it were, cuts itself off from the rest of the universe, leaving a gravitational imprint frozen in the space that's left. It becomes a black hole that things can fall into but not come out."
Prof. Martin Rees
There is an element of anthropomorphic narrative (see above) again here, if we consider the choice of active, rather than passive, phrasing
…as it were, cuts itself off from the rest of the universe, compared with
…as it were, becomes cut off from the rest of the universe
This is presented as something the neutron star itself does ("it will compress…become a black hole – it will go on contracting until it, as it were, cuts itself off…") rather than a process occurring in/to the matter of which it is comprised.
As if galaxies drop over the horizon
Prof. Rees uses another simile, when talking of how the expansion of space means that in time most galaxies will disappear from view,
"All the more distant universe which astronomers like Mark [Sullivan] study, galaxies far away, they will all have expanded their distance from us and in effect disappeared over a sort of horizon and so we just wouldn't see them at all. They'd be too faint, rather like …an inside-out black hole as it were, but in this case they moved so far away that we can't see them any more …"
Prof. Martin Rees
The term horizon, originally referring to the extent of what is in sight as we look across the curved Earth, has become widely used in astronomical contexts where objects cease to be in sight (i.e., the event horizon of a black hole beyond which any light being emitted by an object will not be able to leave {'escape!'} the black hole because of the intense gravitation field), but here Prof. Rees clearly marks out for listeners ("…in effect…a sort of…") that he is making a comparison with the familiar notion of a horizon that we experience here on Earth.
There is another simile here, the reference to the expansion of space leading to an effect "rather like…an inside-out black hole as it were" – but perhaps that comparison would be less useful to a listener new to the topic as it uses a scientific idea rather than an everyday phenomenon as the analogue.
Through a glass onion darkly?
Another simile used by Professor Rees was a references to a "sort of onion skin structure". Now 'onion skin' sometimes refers to the hard, dry, outer material (the 'tunic') usually discarded when preparing the onion for a dish. To a science teacher, however, this is more likely to mean the thin layer of epithelial tissue that can be peeled from the scales inside the bulb. These scales, which are potentially the bases of leaves that can grow if the bulb is planted, are layered in the bulb.
The skin is useful in science lessons as it is a single layer of cells, that is suitable for students to dissect from the onion, and mount for microscopic examination – allowing them to observe the individual cells. There is something at least superficially analogous to this in stars. Observations of the Sun show that convection processes gives rise to structures referred to as convection 'cells'.
Convection 'cells' at the Sun's surface (Source: NASA)Onion skin magnified showing individual epithelial cells (Source: Wikimedia commons)
Yet, when Professor Rees' simile is heard in context, it seems that this is not the focus of the comparison:
"…all the nuclear processes which would occur at different stages in the heavy stars…which have this sort of onion skin structure with the hotter inner layers"
Prof. Martin Rees
Very large stars that have processed much of their hydrogen into helium can be considered to have a layered structure where under different conditions a whole sequence of processes are occurring leading to the formation of successively heavier and heavier elements, and ultimately to a build-up of iron near the centre.
The onion model of the structure of a large star (original image by Taken from Pixabay)
When I heard the reference to the onion, this immediately suggested the layered nature of the onion bulb being like the structure of a star that was carrying out the sequence of processes where the products of one fusion reaction become the raw material for the next. Presumably, my familiarity with the layered model of a star led me to automatically make an association with onions which disregarded the reference to the skin. That is, I had existing 'interpretive resources' to understand why the onion reference was relevant, even though the explicit mention of the skin might make the comparison obscure to someone new to the science.
Metaphors – all the way back up?
Some metaphors can easily be spotted (if someone suggests mitochondria are the power stations of the cell, or a lion is King of the jungle), but if our conceptual systems, and our language, are built by layers of metaphor upon metaphor then actually most metaphors are dead metaphors.
That is, an original metaphor is a creative attempt to make a comparison with something familiar, but once the metaphor is widely taken up, and in time becomes common usage and so a part of standard language, it ceases to act as a metaphor and becomes a literal meaning.
This presumably is what has happened with the adoption of the idea that stars are born, live out their lives, and then die: originally it was a poetic use of language, but now among astronomers it reflects an expanded standard use of terms that were once more restricted (born, live, lifetime, die etc.).
"…Stars dived in blinding skies / Stars die / Blinding skies…" Stars die, but only due to artistic license (Artwork from 'Star's die' by Porcupine Tree, photographer: Chris Kissadjekian)
If you see a standard candle…
When Professor Sullivan refers to a "standard candle", this is now a widely used astronomical notion (in relation to how we estimate distances to distant stars and galaxies that are much too far away to triangulate from parallax as the earth changes its position in the solar system) – but at one time this was used as a figure of speech.
Some figures of speech are created in the moment, but never widely copied and adopted. The astronomical community adopted the 'standard candle' such that it is now an accepted term, even though most young people meeting astronomical ideas for the first time probably have very little direct experience of candles. What might once have seemed a blatantly obvious allusion may now need explaining to the novice.
When Sir Arthur Eddington (famous for collecting observations during an eclipse consistent with predictions from relativity theory about the gravitational 'bending' of starlight) gave a public lecture in 1932, he seems to have assumed that his audience would understand the analogy between an astronomer's 'standard candles' (Cepheid variables) and standard candles they might themselves use!
"If you see a standard candle anywhere and note how bright it appears to you, you can calculate how far off it is; in the same way an astronomer observes his [or her] 'standard candle' in the midst of a nebula, notes its apparent brightness or magnitude, and deduces the distance of the nebula"
Eddington, 1933/1987, pp.7-8
This ongoing development in language means that it may not always be entirely clear which terms are still engaged with as if metaphors and which have now become understood as literal. That is, in considering whether some phrase is a metaphor we can ask two questions:
did the author/speaker intend this as a comparison, or do they consider the term has direct literal meaning?
does the reader/listener understand the term to have a literal meaning, or is it experienced as some novel kind of comparison with another context which has to be related back to the focus?
In the latter case we might also think it is important to distinguish between cases where the audience member can decode the intention of the comparison 'automatically' as part of normal language processing – and cases where they would have to consciously deliberate on the meaning. (In the latter case, the interpretation is likely to disrupt the flow of reading, and when listening could perhaps even require the listener to disengage from the communication such that subsequent speech is missed.)
(Metaphorical?) hosts
So, when Prof. Crawford suggests that
"The supernovae, particularly, are of fundamental importance for the host galaxy…"
Prof. Carolin Crawford
her use of the term 'host' is surely metaphorical (at least for a listener– this term is widely used in the literature of academic astronomy 6). A host offers hospitality for a guest. That does not seem to obviously reflect the relationship between a supernova and the galaxy it is found in and is part of. It is not a guest: rather, in Prof. Sullivan's terms we might suggest that star has 'lived its entire life' in that galaxy – it is its galactic 'home'. Despite this comparison not standing up to much formal analysis, I suspect the metaphor can be automatically processed by anyone with strong familiarity with the concept of a host. Precise alignment may not be a strong criterion for effective metaphors.
Another meaning of host refers to a sacrificial victim (as in the host in the Christian Eucharist) which seems unlikely to be the derivation here, but perhaps fits rather well with Prof. Crawford's point. A supernova too close to earth could potentially destroy the biosphere – an unlikely but not impossible event.
(Metaphorical?) bubbles
Professor Crawford described some of the changes during a supernova,
"You have got your iron core, it collapses down under gravity in less than a second, that kind of leaves the outer layers of the star a little behind, they crash down, bounce on the surface of the core, and then there's a shockwave, that propels all this stellar debris, out into space. So, this is part of the supernova explosion we have been talking about, and it carves out a bubble within the interstellar medium."
Prof. Carolin Crawford
There are a number of places here where everyday terms are applied in an unfamiliar context such as 'core', 'bouncing', 'layers' and 'debris'. But the idea of carving a bubble certainly seems metaphorical, if only because a familiar bubble would have a physical surface, where surely, here, there is no strict interface between discrete regions of gases. But, again, the term offers an accessible image to communicate the process. (And anyone looking at the NASA image above of convection cells in the Sun might well feel that these can be perceived as if bubbles.)
(Metaphorical?) pepper
Similarly, the idea of heavy elements from exploding suns being added to the original hydrogen and helium in the interstellar medium as like adding pepper also offers a strong image,
"…this is the idea of enrichment, you start off with much more primordial hydrogen and helium gas that gets steadily peppered with all these heavy elements…"
Prof. Carolin Crawford
Perhaps 'peppered' is now a dead metaphor, as it is widely used in various contexts unrelated to flavouring food.
(Metaphorical?) imprints
When Professor Rees referred to a neutron star that has become a black hole leaving a "gravitational imprint frozen in the space that's left" this makes good sense as the black hole will not be visible, but its gravitational field will have effects well beyond its event horizon. Yet, one cannot actually make an imprint in space, one needs a suitable material substrate (snow, plater, mud…) to imprint into; and nor has anything been 'frozen' in a literal sense. Indeed, the gravitational field will change as the black hole acquires more material through gravitational capture (and in the very long term loses mass though evaporates Hawking radiation – which is said to cause the black hole to 'evaporate'). So, this is a kind of double metaphor.
(Metaphorical?) blasts and blows
I report above both the idea that rocky planet close to large stars might have derived from 'giant' planets "that have had the outer gassy layers blasted off" and how "big stars…blow off their outer layers". Can stars really blow, or is this based on a metaphor. Blasts usually imply explosions, sudden events, so perhaps these are metaphorical blasts? And it is not just larger stars that engage in blowing off,
"[The sun] will blow off its outer layers and become a red giant, expanding so it will engulf the inner planets, but then the core will settle down to what's called a white dwarf, this is a dead, dense star, about a million times denser than normal stuff…."
Prof. Martin Rees
Metaphors galore!
Perhaps those last examples are not especially convincing – but this reflects a point I made earlier. Language changes over time: it is (metaphorically-speaking) fluid. If language started from giving names to things we can directly point at, then anything we cannot directly point at needs to be labelled in terms of existing words. Most of the terms we use were metaphors at some point, but became literal as the language norms changed.
But society is not a completely homogeneous language community. The requirements of professional discourse in astronomy (or any other specialised field of human activity) drive language modifications in particular regards ahead of general language use. It is not just people in Britain and the United States who are divided by a common language – we all are to some extent. What has become literal meaning for for one person (perhaps a science teacher) may well only be a metaphor to another (a student, say).
After all, when I look up what it is to blow off, I find that the most common contemporary meaning relates to a failure to meet a social obligation or arrangement – I am pretty sure (from the context) that that is not what Professor Rees was suggesting ("…when those big stars face a crisis they [let down] their outer layers".) Once we start looking at texts closely, they seem to be 'loaded' with figures of speech. A planet is not materially constrained in space, yet we understand why an orbit might be considered 'tight'.
In the proceeding quote, the core of a star seems to need no explanation although it presumably derives by analogy with the core of an apple or similar fruit, which itself seems to derive metaphorically form an original meaning of the heart. Again, what is meant by engulf is clear enough although originally it referred to the context of water and the meaning has been metaphorically (or analogously) extended.
The terms red giant and white dwarf clearly derive from metaphor. (Sure, a red giant isgigantic, but then, on any normal scale of human experience, so is a white dwarf.) These terms might mystify someone meeting them for the first time so not already aware they are used to refer to classes of star. This might suggest the value of a completely objective language for discussing science where all terms are tightly (hm, too metaphorical…closely? rigidly? well-) defined, but that would be a project reminiscent of the logical positivist programme in early twentieth century that ultimately proved non-viable. We can only define words with more words, and there are limits to the precision possible with a usable, 'living', language.
Take the "discovery that we are literally made of the ashes of long dead stars". Perhaps, but the term ashes normally refers to the remains of burnt organic material, especially wood, so perhaps we are not literally, but only metaphorically made of the ashes of long dead stars. Just as when when Professor Sullivan noted,
"the white dwarf is made of carbon, it's made of oxygen, and the temperature and the pressure in the centre of that white dwarf star can become so extreme, that carbon detonation can occur in the centre of the white dwarf, and that is a runaway thermonuclear reaction – that carbon burns in astronomer speak into more massive elements…"
Prof. Mark Sullivan
Are we stardust, ashes or just waste?
Burning is usually seen in scientific terms as another word for combustion. So, the nuclear fusion, 'burning' "in astronomer speak" of its nuclear 'fuel' in a star represents an extension of the original meaning by analogy with combustion. 9 Material that is deliberately used to maintain a fire is fuel. A furnace is an artefact deliberately built to maintain a high temperature – the nuclear furnace in a star is not an artefact but a naturally occurring system (gravity holds the material in place), but is metaphorically a furnace. A runaway is a fugitive who has absconded – so to describe a thermonuclear reaction (which is not going anywhere in spatial terms) as 'runaway' adopts what was a metaphor. (Astronomers also use the term 'runaway' to label a class of star that seem to be moving especially fast compared with the interstellar medium – a somewhat more direct borrowing of the usual meaning of 'runaway'.)
To consider us to be made from 'nuclear waste' relies on seeing the star-as-nuclear-furnace as analogous to a nuclear pile in a power station. In nuclear power stations we deliberately process fissile material to allow us to generate electrical power: and material is produced as a by-product of this process (that is, it is a direct product of the natural nuclear processes, but a by-product of our purposeful scheme to generate electricity). To consider something waste means making a value judgement.
If the purpose of a star is to shine (a teleological claim) and the fusion of hydrogen is the means to achieve that end, then the material produced in that process which is no longer suitable as 'fuel' can be considered 'waste'. If the universe does not have any purpose(s) for stars then there is no more basis for seeing this material as waste than there is for seeing stars themselves as the waste products of a process that causes diffuse matter to come together into local clumps. That is, this is an anthropocentric perspective that values stars as of more value than either the primordial matter from which they formed, or the 'dead' matter they will evolve into when they no longer shine 'for us'. Nature may not have such favourites! If it has a purpose, then stars seem to only be intermediate steps towards its ultimate end.
What does support the turtle? Surely, it's metaphors all the way down. (Source: Pintrest)
Sources cited:
Eddington, A. (1933/1987). The Expanding Universe. Cambridge: Cambridge University Press.
Lakoff, G., & Johnson, M. (1980). The metaphorical structure of the human conceptual system. Cognitive Science, 4(2), 195-208.
Ulmer, M., Grace, V., Hudson, H., & Schwartz, D. (1972). Upper Limits to the X-Ray Luminosities of Five Supernovae. The Astrophysical Journal, 173, 205.
Notes:
1 It may seem fanciful that we give a specific individual tree a proper name but should a child inherently appreciate that we commonly name individual hamsters (say, or ships, or roads), but not individual trees? 'Major Oak'is a particular named Oak tree in Sherwood Forest, so the idea is not ridiculous. (It is very large, but apparently the name derives from it being described by an author with the army rank of major. Of course, this term for a soldier leading others derives metaphorically from a Latin word meaning bigger, so…)
2 "So how do we bridge between dogs and trees on one hand and electrons and the strong nuclear force on the other (so to speak!)? The answer is we build using analogy and we talk about those constructions using a great deal of metaphor."
We understand what is meant by bridge here in relation to an actual bridge that physically links two places – such as locations on opposite sides of a river or railway line.
There is no actual building up of materials, but we understand how we can 'build' in the abstract by analogy.
These things are not actually at hand, but we make a metaphorical comparison in terms of distinguishing items held in 'opposite' hands. We understand what is meant by a great deal of something abstract by analogy with a great deal of something we can directly experience, e.g., sand, water, etcetera.
Justice personified, on the one hand weighing up the evidence and on the other imposing sanctions
(Image by Sang Hyun Cho from Pixabay)
We construct scientific concepts and models and theories by analogy with how we construct material buildings – we put down foundations then build up brick by brick so that the top of the structure is only very indirectly supported by the ground.
(Image by joffi from Pixabay)
3 A point is a hypothetical, infinitesimally small, location in space, which is not something a person could actually make. The 'point' of an argument is metaphorically like the point of a pencil or spear which is metaphorically an approximation to an actual point. Of course, we (adult members of the English language community) all know what is meant by the point of an argument – but people new to a language (such as young children) have to find this out, without someone holding up the point of an argument for them to learn to recognise.
4 In part, this means linguistic resources. Each individual person has a unique vocabulary, and even though sharing most words with others, often has somewhat unique ranges of application of those words. But it also refers to personal experiences that can be drawn upon (e.g., having cared for an ill relative, having owned a pet, having undertaken part-time work in a hospital pharmacy, having been taken to work by a parent…) and the cultural referents that are commonly discussed in discourse (cultural icons like the Mona Lisa or Beethoven's fifth symphony; familiarity with some popular television show or film; appreciating that Romeo and Juliet were tragic lovers, or that Gandhi is widely considered a moral role model, and so forth.)
"Penny, I'm a physicist. I have a working knowledge of the entire universe and everything it contains."
"Who's Radiohead?"
"I have a working knowledge of the important things in the universe."
Still from 'The Big Bang Theory' (Chuck Lorre Productions / Warner Bros. Television)
The interpretive resources are whatever mental resources are available to help make sense of communication.
5 I am using the term concept in an 'inclusive' sense (Taber, 2019), in that whenever a person can offer a discrimination about whether something is an example of some category, then they hold a concept (vague or detailed; simple or complex; canonical or alternative).
That is, if someone can (beyond straight guesswork) try to answer one of the questions "what is X? ", "is this an example of X?" or "can you suggests an example of X?", then they have a relevant concept – where X could be…
6 The earliest reference to 'host galaxies' I found in a quick search of the scientific literature was from 1972 in a paper which used the term 'host galaxy' 8 times, including,
"We estimated the distances [of observed supernovae]…by four different methods:
(1) Estimating the absolute luminosity of the host galaxy.
(2) Estimating the absolute luminosity of the supernova.
(3) Using the measured redshift of the host galaxy and assuming the Hubble constant H = 75 km (s Mpc)-1 …
(4) Identifying the host galaxy with a cluster of galaxies for which the distance from Earth had already been estimated.
Ulmer, Grace, Hudson & Schwartz, 1972, p.209
The term 'host galaxy' was not introduced or defined in the paper, suggesting that either it was already in common use as a scientific term (and so a dead metaphor within the astronomical community) in 1972 or Ulmer and colleagues assumed it was obvious enough not to need explanation.
7 It should be pointed out that 'In Our Time' is not presented as succession of mini-lectures, or as a tightly scripted programme, but as a conversation between Melvyn as his guests. Of course, there is some level of preparation by those involved, but in adopting a conversational style, avoiding the sense of prepared statements, it is inevitable that a guest's language will sometimes lack the precision of a drafted and much revised account.
8 A supernova may appear as a new star in the sky if it is so far away that the star was not previously detectable, or as a known star quick;y becoming very much brighter.
9 One should be careful in making such equivalences, as in that although we may equate burning with combustion, burning is an everyday ('life world') phenomenon, and combustion is a scientific concept: often our scientific concepts are more precisely defined than the related everyday terms. (Which is why melting has a broader meaning in everyday life {the sugar melts in the hot tea; the stranger melted away into the mist} than it does in science.) But although we might say, as suggested earlier in the text, we have been burned by exposure to the sun's ultraviolet rays, or by contact with a caustic substance, in those contexts we are unlikely to consider our skin as 'fuel' for the process.
"From one of the known ingredients of steam being a highly inflammable body, and the other that essential part of the air which supports combustion, it was imagined that [steam] would have the effect of increasing the fire …"
Producing iron requires high temperatures: adding H2O does not help (Image by zephylwer0 from Pixabay)
The challenge of chemical combination
School science teachers are likely aware of how chemistry poses some significant leaning challenges for learners. One of these is the nature of chemical compounds. That is, compounds of chemical elements.
It may seem obvious to learners that when we 'mix' two components with different properties we should get a mixture with a combination of the component properties. So far, so good. But of course, in chemical reactions we do not just mix different substances, but rather they chemically react. So, sodium will react with chlorine, which can be understood in terms of processes occurring at the nanoscopic scale where molecules of a gas interact with the metallic lattice of sodium cations and delocalised electrons.
Sodium and chlorine behaving badly
Although we can model this process, we cannot observe it directly, or even the starting structures at that scale. Understandably, students often struggle to relate the macroscopic and molecular:
As Sodium is a reactive meterial [sic] and chlorine is a acid. When Sodium is placed in Chlorine, Sodium react badly making a flame and maybe a noise. I think why this reaction happen is because as Sodium reactive metal meaning that it atomic configuration is unstable make the metal danger And as Chlorine is a dangerous acid. When sodium is placed in Chlorine, the sodium start dissolving in the acid due to all the particle rushing around quickly pushing together with Chlorine atom. Producing Sodium chloride.
Student setting out on Advanced level chemistry, quoted in Taber, 1996
So, for example, if we do burn sodium in chlorine we end up with sodium chloride which is a new substance that has its own properties – properties which are not simply some mixture of, or intermediate between, the properties of the substances we start with (the reactants).
Indeed, sodium is a dangerous material to handle: it will react vigorously with water (in a person's sweat for example!) and burns violently in air. Chlorine is so nasty that it has been used as a weapon of war (and since banned as an 'unacceptable' weapon, even in war). In the 'great' war ('great' only because of its scale) the way men died in agony from breathing chlorine was much reported, as well as the effects on those who survived the gas – being blinded for example.
"In all my dreams before my helpless sight,
He plunges at me, guttering, choking, drowning."
Wilfred Owen, Dulce et Decorum Est1
Sweet and honourable? 1 (Image by Bruce Mewett from Pixabay)
Sodium chloride certainly has its associated hazards – if eaten in excess it is a risk factor for high blood pressure for example – but is certainly not dangerous in anything like the same sense. Many people put sodium chloride on their chips (often along with ethanoic acid solution). No one would want sodium on their food, or to eat in a canteen with a chlorine atmosphere!
When is something both present and not present?
Why this is especially challenging is that the chemistry teacher tells the students that although, at one level, the new substance does not contain its precursors – there is no sodium (substance) or chlorine (substance) in the substance sodium chloride – yet it is a compound of these elements and in some some sense the elements remain 'in' the compound.
Learning chemistry requires understanding how disciplinary concepts explained in terms of submicroscopic level models (After Figure 5, Taber, 2013)
This links to that key theoretical framework in chemistry where we can explain macroscopic (bench scale) phenomena in terms of models of matter at the submicroscopic (indeed nanoscopic or even subnanoscopic) scale. The sense in which sodium chloride 'contains' sodium and chlorine is that it is comprised of a lattice of sodium ions and chloride ions – species which include the specific types of nuclei (those of charge +11 and +17 respectively) that define those elements.
So, when we ask whether the elements are in some sense 'in' the compound we have to think in terms of these abstract models at a tiny scale – there is no sodium substance or chlorine substance present, but there is something that is inherently identified with these two elements. In a sense, but a very abstract sense, the elements are still present. Or, perhaps, better, something intrinsic to those elements is still present.
"We are working here with two complementary meanings for the idea of element, one at the (macroscopic) level of phenomena we can demonstrate to students (substances, and their reactions); the other deriving from a theoretical model in terms of conjectured submicroscopic entities ('quanticles'…).
However, there is also a sense in which an element is considered to be present, in a virtual or potential sense, within its compounds. This use is more common among French-speaking chemists, and in the English-speaking world we normally consider it quite inappropriate to suggest that sodium is somehow present in sodium chloride, or hydrogen in water. Yet, of course, chemical formulae (NaCl, H2O, etc) tell us that the compounds somehow 'contain' the elements."
This is easy to understand for someone very familiar with molecular level models – but is understandably difficult for novice learners. Thus we can reasonably understand why there are common alternative conceptions along the lines of students thinking that, for example, a compound of a dangerous element (say chlorine) must also be dangerous. Yet we 'mix' and react a soft, reactive, metal and a choking green gas – and get hard white crystals that safely dissolve in water to give a solution we can use in cooking, or to soak our feet, or to gargle with.
An historical precedent
Because science teachers and chemists are so used to thinking in models at the molecular level, we can forget just how unfamiliar this perspective is to the novice, and so the challenge of acquiring the scientific ways of thinking that have become 'second nature' through extensive application.
I was therefore fascinated to see an example of this same alternative conception, assuming a compound will show the properties of its constituent elements, reported by the scientist Sir John Herschel (astronomer, chemist, mathematician, philosopher…), not in a school science context, but rather an industrial context.
"The smelting of iron requires the application of the most violent heat that can be raised, and is commonly performed in tall furnaces, urged by great iron bellows driven by steam-engines. Instead of employing this power to force air into the furnace through the intervention of bellows, it was, on one occasion, attempted to employ the steam itself in, apparently, a much less circuitous manner; viz. by directing the current of steam in a violent blast, from the boiler at once into the fire. From one of the known ingredients of steam being a highly inflammable body, and the other that essential part of the air which supports combustion, it was imagined that this would have the effect of increasing the fire to tenfold fury, whereas it simply blew it out; a result which a slight consideration of the laws of chemical combination, and the state in which the ingredient elements exist in steam, would have enabled any one to predict without a trial."
Herschel, J. F. W. (1830/1851/2017), §37 2
So, here, instead of dropping marks on a test, this misunderstanding of the chemistry leads to a well-intentioned industrialist trying to generate heat in a blast furnace by adding water to the fire. But this does remind us just how counter-intuitive some of the things taught in science are. It might also be a useful anecdote to share with students to help them appreciate that that their errors are by no means unusual, or necessarily a reflection on their ability.
Perhaps this might even be a useful teaching example that could be built up into a historical anecdote which students might readily recall and that will help them remember that compounds have new properties that may be quite different from their constituent elements. So, while a mixture of the flammable gas hydrogen and oxygen can be explosive, a combination (that is, a chemical combination – a compound), of hydrogen and oxygen will not 'feed' a fire but dampen it down. Just as well, really, as otherwise emergency fire and rescue services would need to find an alternative to the widely available, inexpensive, recyclable, non-toxic, agent they widely use in fighting fires.
Compounds and mixtures are not interchangeable (Image by David Mark from Pixabay)
Work cited:
Herschel, J. F. W. (1830/1851/2017). Preliminary Discourse on the Study of Natural Philosophy. Project Gutenberg EBook.
1 Wilfred Owen was famous for his war poetry written about the horrors of the trench fighting in the 'first world war'. Owen was killed a week before the war ended. 'Dulce Et Decorum Est' referred to a Latin phrase or motto (dulce et decorum est pro patria mori) that Owen labelled as 'the old lie', that it was sweet and honourable to die in the service of one's country.
2 For some reason, "…it was imagined that this would have the effect of increasing the fire to tenfold fury, whereas it simply blew it out…" puts me in mind of
"the mighty ships tore across the empty wastes of space and finally dived screaming on to…Earth – where due to a terrible miscalculation of scale the entire battle fleet was accidentally swallowed by a small dog."
Douglas Adams, The Hitchhiker's Guide to the Galaxy
The BBC radio programme 'In Our Time' today tackled the electron. As part of the exploration there was the introduction of the positron, and the notion of matter-antimatter annihilation. These are quite brave topics to introduce in a programme with a diverse general audience (last week Melvyn Bragg and his guests discussed Plato's Atlantis and next week the programme theme is the Knights Templar).
Prof. Victoria Martin of the School of Physics and Astronomy at the University of Edinburgh explained:
If we take a pair of matter and antimatter, so, since we are talking about the electron today, if we take an electron and the positron, and you put them together, they would annihilate.
And they would annihilate not into nothingness, because they both had mass, so they both had energy from E=mc2 that tells us if you have mass you have energy. So, they would annihilate into energy, but it would not just be any kind of energy: the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light. And it will have a very specific amount of energy. Its energy will be equal to the sum of the energy of electron and the positron that they had initially when they collided together.
Prof. Victoria Martin on 'In Our Time'
"An electron and the positron, and you put them together, they would annihilate…they would annihilate into energy" – but this could be misleading.
Now, I am sure that is somewhat different from how Prof. Martin would treat this topic with university physics students – of course, science in the media has to be pitched at the largely non-specialist audience.
It struck me that this presentation had the potential to reinforce a common alternative conception ('misconception') that mass is converted into energy in certain processes. Although I am aware now that this is an alternative conception, I seem to recall that is pretty much what I had once understood from things I had read and heard.
It was only when I came to prepare to teach the topic that I realised that I had a misunderstanding. That, I think, is quite common for teachers – when we have to prepare a topic well enough to explain it to others, we may spot flaws in our own understanding (Taber, 2009)
So, for example, I had thought that in nuclear processes, such as in a fission reactor or fusion in stars, the mass defect (the apparent loss of mass as the resulting nuclear fragments have less mass than those present before the process) was due to that amount of massbeing converted to energy. This is sometimes said to explain why nuclear explosions are so much more violent than chemical explosions, as (given E=mc2): a tiny amount of mass can be changed into a great deal of energy.
Prof. Martin's explanation seemed to support this way of thinking: "they would annihilate into energy".
An alternative conception of particle annihilation: This scheme seems to be implied by Prof. Martin's comments
What is conserved?
It is sometimes suggested that, classically, mass and energy were considered to be separately conserved in processes, but since Einstein's theories of relativity have been adopted, now it is considered that mass can be considered as if a form of energy such that what is conserved is a kind of hybrid conglomerate. That is, energy is still considered conserved, but only when we account for mass that may have been inter-converted with energy. (Please note, this is not quite right – see below.)
So, according to this (mis)conception: in the case of an electron-positron annihilation, the mass of the two particles is converted to an equivalent energy – the mass of the electron and the mass of the positron disappear from the universe and an equivalent quantity of energy is created. Although energy is created, energy is still conserved if we allow for the mass that was converted into this new energy. Each time an electron and positron annihilate, their masses of about 2 ✕ 10-30 kg disappear from the universe and in its place something like 2 ✕ 10-13 J appears instead – but that's okay as we can consider 2 ✕ 10-30 kg as a potential form of energy worth 2 ✕ 10-13 J.
However, this is contrary to what Einstein (1917/2004) actually suggested.
Einstein did not suggest that matter could be changed to energy
Equivalence, not interconversion
What Einstein actually suggested was not that mass could be considered as if another kind/form of energy (alongside kinetic energy and gravitational potential, etc.) that needed to be taken into account in considering energy conservation, but rather that inertial mass can be considered as an (independent) measure of energy.
That is, we think energy is always conserved. And we think thatmass is always conserved. And in a sense they are two measures of the same thing. We might see these two statements as having redundancy:
In a isolated system we will always have the same total quantity of energy before and after any process.
In a isolated system we will always have the same total quantity of mass before and after any process.
As mass is always associated with energy, and so vice versa, either of these statements implies the other. 1
Two conceptions of the shift from a Newtonian to a relativistic view of the conservation of energy (move the slider to change the image)
No interconversion?
So, mass cannot be changed into energy, nor vice versa. The sense in which we can 'interconvert' is that we can always calculate the energy equivalence of a certain mass (E=mc2) or mass equivalence of some quantity of energy (m=E/c2).
So, the 'interconversion' is more like a change of units than a change of entity.
Although we might think of kinetic energy being converted to potential energy reflects a natural process (something changes), we know that changing joules to electron-volts is merely use of a different unit (nothing changes).
If we think of a simple pendulum under ideal conditions 2 it could oscillate for ever, with the total energy unchanged, but with the kinetic energy being converted to potential energy – which is then converted back to kinetic energy – and so on, ad infinitum. The total energy would be fixed although the amount of kinetic energy and the amount of potential energy would be constantly changing. We could calculate the energy in joules or some other unit such as eV or ergs (or calories or kWh or…). We could convert from one unit to another, but this would not change anything about the physical system. (So, this is less like converting pounds to dollars, and more like converting an amount reported in pounds {e.g., £24.83} into an amount reported in pence {e.g., 2483p}.)
Using this analogy, the electron and positron being converted to a photon is somewhat like kinetic energy changing to potential energy in a swinging pendulum (something changes), but it is not the case that mass is changed into energy. Rather we can do our calculations in terms of energy or mass and will get (effectively, given E=mc2) the same answer (just as we can add up a shopping list in pounds or pence, and get the same outcome given the conversion factor, 1.00£ = 100p).
So, where does the mass go?
If mass is conserved, then where does the mass defect – the amount by which the sum of masses of daughter particles is less than the mass of the parent particle(s) – in nuclear processes go? And, more pertinent to the present example, what happens to the mass of the electron and positron when they mutually annihilate?
To understand this, it might help to bear in mind that in principle these process are like any other natural processes – such as the swinging pendulum, or a weight being lifted with pulley, or methane being combusted in a Bunsen burner, or heating water in a kettle, or photosynthesis, or a braking cycle coming to a halt with the aid of friction.
In any natural process (we currently believe)
the total mass of the universe is unchanged…
but mass may be reconfigured
the total energy of the universe is unchanged…
but energy may be reconfigured; and
as mass and energy are associated, any reconfigurations of mass and energy are directly correlated.
So, in any change that involves energy transfers, there is an associated mass transfer (albeit usually one too small to notice or easily measure). We can, for example, calculate the (tiny) increase in mass due to water being heated in a kettle – and know just as the energy involved in heating the water came from somewhere else, there is an equivalent (tiny) decrease of mass somewhere else in the wider system (perhaps due to falling of water powering a hydroelectric power station). If we are boiling water to make a cup of tea, we may well be talking about a change in mass of the order of only 0.000 000 001 g according to my calculations for another posting.
The annihilation of the electron and positron is no different: there may be reconfigurations in the arrangement of mass and energy in the universe, but mass (and so energy) is conserved.
So, the question is, if the electron and positron, both massive particles (in the physics sense, that they have some mass) are annihilated, then where does their mass go if it is conserved? The answer is reflected in Prof. Martin's statement that "the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light". The mass is carried away by the photon.
The mass of a massless particle?
This may seem odd to those who have learnt that, unlike the electron and positron, the photon is massless. Strictly the photon has no rest mass, whereas the electron and positron do have rest mass – that is, they have inertial mass even when judged by an observer at rest in relation to them.
So, the photon only has 'no mass' when it is observed to be stationary – which nicely brings us back to Einstein who noted that electromagnetic radiation such as light could never appear to be at rest compared to the observer, as its very nature as a progressive electromagnetic wave would cease if one could travel alongside it at the same velocity. This led Einstein to conclude that the speed of light in any given medium was invariant (always the same for any observer), leading to his theory of special relativity.
So, a photon (despite having no 'rest' mass) not only carries energy, but also the associated mass.
Although we might think in terms of two particles being converted to a certain amount of energy as Prof. Martin suggests, this is slightly distorted thinking: the particles are converted to a different particle which now 'has' the mass from both, and so will also 'have' the energy associated with that amount of mass.
Mass is conserved during the electron-positron annihilation
A slight complication is that the electron and position are in relative motion when they annihilate, so there is some kinetic energy involved as well as the energy associated with their rest masses. But this does not change the logic of the general scheme. Just as there is an energy associated with the particles' rest masses, there is a mass component associated with their kinetic energy.
The total mass-energy equivalence before the annihilation has to include both the particle rest masses and their kinetic energy. The mass-energy equivalence afterwards (being conserved in any process) also reflects this. The energy of the photon (and the frequency of the radiation) reflects both the particle masses and their kinetic energies at the moment of the annihilation. The mass (being perfectly correlated with energy) carried away by the photon also reflects both the particle masses and their kinetic energies.
How could 'In Our Time' have improved the presentation?
It is easy to be critical of people doing their best to simplify complex topics. Any teacher knows that well-planned explanations can fail to get across key ideas as one is always reliant on what the audience already understands and thinks. Learners interpret what they hear and read in terms of their current 'interpretive resources' and habits of thinking.
A physicist or physics student hearing the episode would likely interpret Prof. Martin's statement within a canonical conceptual framework. However, someone holding the 'misconception' that mass is converted to energy in nuclear processes would likely interpret "they would annihilate into energy" as fitting, and reinforcing, that alternative conception.
I think a key issue here is a slippage that apparently refers to energy being formed in the annihilation, rather than radiation: (i.e., Prof. Martin could have said "they would annihilate into [radiation]"). When the positron and electron 'become' a photon, matter is changed to radiation – but it is not changed to energy, as matter has mass, and (as mass and energy have an equivalence) the energy is already there in the system.
Energy is reconfigured, but is not formed, in the annihilation process.
So, this whole essay is simply suggesting that a change of one word – from energy to radiation – could potentially avoid the formation of, or the reinforcing of, the alternative conception that mass is changed into energy in processes studied in particle physics. As experienced science teachers will know, sometimes such small shifts can make a good deal of difference to how we are interpreted and, so, what comes to be understood.
1 In what is often called a closed system there is no mass entering or leaving the system. However, energy can transfer to, or from, the system from its surroundings. Classically it might be assumed that the mass of a closed system is constant as the amount of matter is fixed, but Einstein realised that if there is a net energy influx to, or outflow from, the system, than some mass would also be transferred – even though no matter enters or leaves.
2 Perhaps in a uniform gravitational field, not subject to to any frictional forces, with an inextensible string supporting the bob, and in thermal equilibrium with its environment.
we are made of particles that have existed since the moment the universe began…those atoms travelled 14 billion years through time and space
The Big Bang Theory (but not quite the big bang theory).
What is the Big Bang Theory?
The big bang theory is a theory about the origin and evolution of the universe. Being a theory, it is conjectural, but it is the theory that is largely taken by scientists as our current best available account.
According to big bang theory, the entire universe started in a singularity, a state of infinite density and temperature, in which time space were created as well as matter. As the universe expanded it cooled to its present state – some, about, 13.8 billion years later.
Our current best understanding of the Cosmos is that the entire Universe was formed in a 'big bang' (Image by Gerd Altmann from Pixabay)
The term 'big bang' was originally intended as a kind of mockery – a sarcastic description of the notion – but the term was adopted by scientists, and has indeed become widely used in general culture.
Which brings me to 'The Big Bang Theory', which is said to have been the longest ever running sitcom ('situation comedy') – having been in production for longer than even 'Friends'.
The Big Bang Theory: Not science fiction, but fictional science? (Five of these characters have PhDs in science: one 'only' has a master's degree in engineering.)
A situation comedy is set around a situation. The situation was that two Cal Tech physicists are sharing an apartment. Leonard (basically a nice guy, but not very successful with women) is flatmate to Sheldon, a synaesthete, and kind of savant (a device on which to lever much of the humour) – a genius with an encyclopaedic knowledge of most areas of science but a deficient 'theory of mind' such that he lacks
insight into others, and so also
empathy, and
the ability to tell when people are using humour or being sarcastic to him.
If most physicists were like Sheldon we could understand why the big bang theory is still called the big bang theory even though the term was intended to be facetious. The show writers claim that Sheldon was not deliberately written to be on the autistic spectrum, but he tends to take statements literally: when it is suggested that he is crazy, he responds that he knows he is not as his mother had him tested as a child.
Sheldon (at right, partially in shot) has been widely recognised by viewers as showing signs of high-functioning Autism or Aspergers syndrome. (Still from The Big Bang Theory)
These guys hang out with Raj (Rajesh), an astrophysicist and Cambridge graduate so shy he is unable to speak to women, or indeed in their presence (presumably not a problem inherited from his father who is is a successful gynaecologist in India), and an engineer, Howard, who to my viewing is just an obnoxious creep with no obvious redeeming qualities. (But then I've not seen the full run.) When Howard becomes a NASA astronaut, he is bullied by the other astronauts, and whilst bullying is never acceptable, it is difficult to be too judgemental in his case.
This group are scientists, and they are 'nerds'. They watch science fiction and superhero movies, buy comic books and action figures, play competitive board games and acquire all the latests technical gadgets. And, apart from Sheldon (who has a strong belief in following a principled rigorous regime of personal hygiene that makes close contact with other humans seem repulsive) they try, and largely fail, to attract women.
In case this does not seem sufficiently stereotypical, the situation is complete when a young woman moves into in the flat opposite Leonard and Sheldon: Penny is the 'hot' new neighbour, who comes across as a 'dumb blonde' (she wants to be an actress – she is actually a waitress whilst she works at that), something of a hedonist, and not having the slightest knowledge of, or interest in, science. Penny's plan in life is to become a movie star, and her back-up plan is to become a television star.
If Sheldon and his friends tend to rather fetishise science and see it as inherently superior to other ways of engaging in the world, then Penny seems to reflect the other side of 'the two cultures' of C. P. Snow's famous lecture/essay that described an arts-science divide in mid-twentieth century British public life. That is, not only an acknowledged ignorance of scientific matters, but an ignorance that is almost worn as a badge of honour. Penny, of course, actually has a good deal of knowledge about many areas of culture that our 'heroes' are ignorant of.
Initially, Penny is the only lead female character in the show. This creates considerable ambiguity in how we are expected to see the show's representations of scientists during the early series. Is the viewer meant to be sharing their world where women are objects of recreation and sport and a distraction from the important business of the scientific quest? Or, is the audience being asked to laugh at these supposedly highly intelligent men who actually have such limited horizons?
Sheldon: I am a physicist. I have a working knowledge of the entire universe and everything it contains.
Penny. Who's Radiohead?
[pause]
Sheldon: I have a working knowledge of important things in the universe.
Penny has no interest in science
So, the premise is: can the nerdy, asthmatic, short-sighted, physicist win over the pretty, fun-loving, girl-next-door who is clearly seen to be 'out of his league'.
Spoiler alert
Do not read on if you wish to watch the show and find out for yourself. 😉
A marriage made in the heavens?
I recently saw an episode in series n (where n is a large positive integer) where Leonard and Penny decided to go to Las Vagas and get married. Leonard said he had written his own marriage vows – and it was these that struck me as problematic. My complaint was nothing to do with love and commitment, but just about physics.
Cal Tech physicist Leonard Hofstadter (played by Johnny Galecki) wrote his own vows for marriage to Penny (Kaley Cuoco) in 'The Big Bang Theory'
A non-physical love?
I made a note of Leonard's line:
"Penny, we are made of particles that have existed since the moment the universe began. I like to think those atoms travelled 14 billion years through time and space to create us so that we could be together and make each other whole."
Leonard declares his love
Sweet. But wrong.
Perhaps Leonard had been confused by the series theme music, the 'History of Everything', by the band Barenaked Ladies. The song begins well enough:
"Our whole universe was in a hot dense state
Then nearly fourteen billion years ago, expansion started…"
Lyrics to History of Everything (The Big Bang Theory Theme)
but in the second verse we are told
"As every galaxy was formed in less time than it takes to sing this song.
A fraction of a second and the elements were made."
Lyrics to History of Everything (The Big Bang Theory Theme)
which seems to reflect a couple of serious alternative conceptions.
So, the theme song seems to suggest that once the big bang had occurred, "nearly fourteen billion years ago", the elements were formed in a matter of seconds, and the galaxies in a matter of minutes. Leonard goes further, and suggests the atoms that he and Penny are comprised of have existed since "the moment the universe began". This is all contrary to the best understanding of physicists.
Surely Leonard, who defended his PhD thesis on particle physics, would know more about the canonical theories about the formation of those particles? (If not, he could ask Raj who once applied for a position in stellar evolution.)
The "hot dense state" was so hot that no particles could have condensed out. Certainly, some particles began to appear very soon after the big bang, but for much of the early 'history of everything' the only atoms that could exist were of the elements hydrogen, helium and lithium – as only the nuclei of these atoms were formed in the early universe.
The formation of heavier elements – carbon, oxygen, silicon and all the rest – occurred in stars – stars that did not exist until considerable cooling from the hot dense state had occurred. (See for example, 'A hundred percent conclusive science. Estimation and certainty in Maisie's galaxy'.) Most of the matter comprising Leonard, Penny, and the rest of us, does not reflect the few elements formed in the immediate aftermath of the big bang, but heavier elements that were formed billions of years later in stars that went supernovae and ejected material into space. 1 As has often been noted, we are formed from stardust.
"…So don't forget the human trial, The cry of love, the spark of life, dance thru the fire
Stardust we are Close to divine Stardust we are See how we shine"
From the lyrics to 'Stardust we are' (The Flower Kings – written by Roine Stolt and Tomas Bodin)
Does it matter – it is only pretend
Of course The Big Bang Theory (unlike the big bang theory) is not conjecture, but fiction. So, does it matter if it gets the science wrong? The Big Bang Theory is not meant to be science fiction, but a fiction that uses science to anchor it into a situation that will allow viewers to suspend disbelief.
Leonard is a believable character, but Sheldon is an extreme outlier. Howard and Raj are caricatures, exaggerations, as indeed are Amy (neurobiologist) and Bernadette (microbiologist) the other core characters introduced later.
But the series creators and writers seem to have made a real effort at most points in the show to make the science background authentic. Dialogue, whiteboard contents, projects, laboratory settings and the like seem to have been constructed with great care so that the scientifically literate viewer is comfortable with the context of the show. This authentic professional context offers the credible framework within which the sometimes incredible events of the characters' lives and relationships do not seem immediately ridiculous.
In that context, Leonard getting something so wrong seems incongruent.
Then again, he is in love, so perhaps his vows are meant to tell the scientifically literate viewer that there is a greater truth than even science – that in matters of the heart, poetic truth trumps even physics?
A Marillion song tells us:
A wise man once wrote That love is only An ancient instinct For reproduction Natural selection A wise man once said That everything could be explained And it's all in the brain
But as the same song asks: "where is the wisdom in that?"
Source cited:
Snow, C. P. (1959/1998). The Rede Lecture, 1959: The two cultures. In The Two Cultures (pp. 1-51). Cambridge University Press.
Note:
1 I was tempted to write 'most of the atoms'. Certainly most of the mass of a person is made up of atoms 2 that were formed a long time after the big bang. However, in terms of numbers of atoms, there are more of the (lightest) hydrogen atoms than of any other element: we are about 70% water, and water comprises molecules of H2O. So, that is getting close to half the atoms in us before we consider all the hydrogen in the fats and proteins and so forth.
2 That, of course, assumes the particles we are made of are atoms. Actually, we are comprised chemically of molecules and ions and relatively very, very few free atoms (those that are there are accidentally there in the sense they are not functional). No discrete atoms exist within molecules. So, to talk of the hydrogen atoms in us is to abstract the atoms from molecules and ions.
Leonard confuses matters (and matter) by referring initially to particles (which could be nucleons, quarks?) but then equating these to atoms – even though atoms are unlikely to float around for nearly 14 billion years without interacting with radiation and other matter to get ionised, form molecules, that may then dissociate, etc.
For many people reading this, I am making a pedantic point. When we talk of the atoms in a person's body, we do not actually mean atomsper se, but component parts of molecules of compounds of the element indicated by the atomreferred to*. A water molecule does not contain two hydrogen atoms and an oxygen atom, but it does contain two hydrogen atomic nuclei, and the core of an oxygen atom (its nucleus, and inner electron 'shell') within an 'envelope' of electrons.
* So, it is easier to use the shorthand: 'two atoms of hydrogen and one of oxygen'.
The reason it is sometimes important to be pedantic is that learners often think of a molecule as just a number of atoms stuck together and not as a new unitary entity composed of the same set of collective components but in a new configuration that gives it different properties. (For example, learners sometimes think the electrons in a covalent bond are still 'owned' by different atoms.) There is an associated common alternative conception here: the assumption of initial atomicity, where students tend to think of chemical processes as being interactions between atoms, even though reacting substances are very, very rarely atomic in nature.
