This referred to an article in a recent issue of the magazine (May 2022, and also available on line) which proposed the slightly more subtle question 'Is fire a solid, liquid, gas, plasma – or something else entirely?'
This was an interesting and fun article, and I wondered how other readers might have responded.
An invitation
No one had commented on the article on line, so I offered my own comment, reproduced below. Before reading this, I would strongly recommend visiting the web-page and reading the original article – and considering how you would respond. (Indeed, if you wish, you can offer your own response there as a comment on the article.)
Ian Farrell (2022) asks: "Is fire a solid, liquid, gas, plasma – or something else entirely?" I suggest this is something of a trick question. It is 'something else', even if not 'something else entirely'.
It is perhaps not 'something else entirely' because fire involves mixtures of substances, and those substances may be describable in terms of the states of matter.
However, it is 'something else', because the classification into different states of matter strictly applies to pure samples of substances. It does not strictly apply to many mixtures: for example, honey, is mostly ('solid') sugar dissolved in ('liquid') water, but is itself neither a solid nor a liquid. Ditto jams, ketchup and so forth. Glass is in practical everyday terms a solid, obviously, but, actually, it flows and very old windows are thicker near their bottom edges. (Because glass does not have a regular molecular level structure, it does not have a definite point at which it freezes/melts.) Many plastics and waxes are not actually single substances (polymers often contain molecules of various chain lengths), so, again, do not have sharp melting points that give a clear solid-liquid boundary.
Fire, however, is not just outside the classification scheme as it involves a mixture (or even because it involves variations in mixture composition and temperature at different points in the flame), but because it is not something material, but a process.
Therefore, asking if fire is a solid, liquid, gas, or plasma could be considered an 'ontological category error' as processes are not the type of entities that the classification can be validly applied to.
You may wish to object that fire is only possible because there is material present. Yes, that is true. But, consider these questions:
Is photosynthesis a solid, liquid, gas, plasma…?
Is distillation a solid, liquid, gas, plasma…?
is the Haber process a solid, liquid, gas, plasma…?
is chromatography a solid, liquid, gas, plasma…?
Is fermentation a solid, liquid, gas, plasma… ?
Is melting a solid, liquid, gas, plasma…?
In each case the question does not make sense, as – although each involves substances, and these may individually, at least at particular points in the process, be classified by state of matter- these are processes and not samples of material.
Farrell hints at this in offering readers the clue "once the fuel or oxygen is exhausted, fire ceases to exist. But that isn't the case for solids, liquids or gases". Indeed, no, because a sample of material is not a process, and a process is not a sample of material.
I am sure I am only making a point that many readers of Education in Chemistry spotted immediately, but, unfortunately, I suspect many lay people (including probably some primary teachers charged with teaching science) would not have spotted this.
That was my response at Education in Chemistry, but I was also aware that it related to a wider issue about the nature of students' alternative conceptions.
Prof. Michelene Chi, a researcher at Arizona State University, has argued that a common factor in a wide range of student alternative conceptions relates to how they intuitively classify phenomena on 'ontological trees'.
"Ontological categories refer to the basic categories of realities or the kinds of existent in the world, such as concrete objects, events, and abstractions."
Chi, 2005, pp.163-164
We can think of all the things in the world as being classifiable on a series of branching trees. This is a very common idea in biology, where humans would appear in the animal kingdom, but more specifically among the Chordates, and more specifically still in the Mammalia class, and even more specifically still as Primates. Of course the animals branch could also be considered part of a living things tree. However, some children may think that animals and humans are inherently different types of living things – that they would be on different branches.
Some student alternative conceptions can certainly be understood in terms of getting typologies wrong. One example is how electron spin is often understood. For familiar objects, spin is a contingent property (the bicycle wheel may, or may not, be spinning – it depends…). Students commonly assume this applies to quanticles such as electrons, whereas electron spin is intrinsic – you cannot stop an electron 'spinning', as you could a cycle wheel, as spin is an inherent property of electrons. Just as you cannot take the charge away from an electron, nor can you remove its spin.
Two ways of classifying some electron properties (after Figures 8 and 9 in Taber, 2008). The top figure shows the scientific model; the bottom is a representation of a common student alternative conception.
Chi (2009) suggested three overarching (or overbranching?) distinct ontologial trees being entities, processes and mental states. These are fundamentally different types of category. The entities 'tree' encompasses a widely diverse range of things: furniture, cats, cathedrals, grains of salt, Rodin sculptures, iPads, tectonic plates, fossil shark teeth, Blue Peter badges, guitar picks, tooth picks, pick axes, large hadron colliders, galaxies, mitochondria….
Despite this diversity, all these entities are materials things, not be confused with, for example, a belief that burning is the release of phlogiston (a mental state) or the decolonisation of the curriculum (a process).
Chi suggested that often learners look to classify phenomena in science as types of material object, when they are actually processes. So, for example, children may consider heat is a substance that moves about, rather than consider heating as a process which leads to temperature changes. 1 Similarly 'electricity' may be seen as stuff, especailly when the term is undifferentiated by younger learners (being a blanket term relating to any electrical phenomenon). Chemical bonds are often thought of as material links, rather than processes that bind structures together. So, rather than covalent bonding being seen as an interaction between entities, it is seen as an entity (often as a 'shared pair of electrons').
Of course, science teachers (or at least the vast majority) do not make these errors. But any who do think that fire should be classifiable as one of the states of matter are making a similar, if less blatant, error of confusing matter and process. Chi's research suggests this is something we can easily tend to do, so it is not shameful – and Ian Farrell has done a useful service by highlighting this issue, and asking teachers to think about the matter…or rather, not the 'matter', but the process.
Work cited:
Chi, M. T. H. (2005). Commonsense Conceptions of Emergent Processes: Why Some Misconceptions Are Robust. Journal of the Learning Sciences, 14(2), 161-199. https://doi.org/10.1207/s15327809jls1402_1
Chi, M. T. (2009). Three types of conceptual change: Belief revision, mental model transformation, and categorical shift. In International handbook of research on conceptual change (pp. 89-110). Routledge.
Farrell, I. (2022). The burning question. Is fire a solid, liquid, gas, plasma – or something elkse entirely? Education in Chemistry, 59(3), 11.
Getting that sinking feeling on reading published studies
Keith S. Taber
this is like finding that, after a period of watering plant A, it is taller than plant B – when you did not think to check how tall the two plants were before you started watering plant A
Research on prelabs
I was looking for studies which explored the effectiveness of 'prelabs', activities which students are given before entering the laboratory to make sure they are prepared for practical work, and can therefore use their time effectively in the lab. There is much research suggesting that students often learn little from science practical work, in part because of cognitive overload – that is, learners can be so occupied with dealing with the apparatus and materials they have little capacity left to think about the purpose and significance of the work. 1
Okay, so is THIS the pipette? (Image by PublicDomainPictures from Pixabay)
Approaching a practical work session having already spent time engaging with its purpose and associated theories/models, and already having become familiar with the processes to be followed, should mean students enter the laboratory much better prepared to use their time efficiently, and much better informed to reflect on the wider theoretical context of the work.
I found a Swedish paper (Winberg & Berg, 2007) reporting a pair of studies that tested this idea by using a simulation as a prelab activity for undergraduates about to engage with an acid-base titration. The researchers tested this innovation by comparisons between students who completed the prelab before the titration, and those who did not.
The work used two basic measures:
types (sophistication) of questions asked by students during the lab. session
elicitation of knowledge in interviews after the laboratory activity
The authors found some differences (between those who had completed the prelab and those that had not) in the sophistication of the questions students asked, and in the quality of the knowledge elicited. They used inferential statistics to suggest at least some of the differences found were statistically significant. From my reading of the paper, these claims were not justified.
A peer reviewed journal (no, really, this time)
This is a paper in a well respected journal (not one of the predatory journals I have often discussed on this site). The Journal of Research in Science Teaching is published by Wiley (a major respected publisher of academic material) and is the official journal of NARST (which used to stand for the National Association for Research in Science Teaching – where 'national' referred to the USA 2). This is a journal that does take peer review very seriously.
The paper is well-written and well-structured. Winberg and Berg set out a conceptual framework for the research that includes a discussion of previous relevant studies. They adopt a theoretical framework based on the Perry's model of intellectual development (Taber, 2020). There is considerable detail of how data was collected and analysed. This account is well-argued. (But, you, dear reader, can surely sense a 'but' coming.)
Experimental research into experimental work?
The authors do not seem to explicitly describe their research as an experiment as such (as opposed to adopting some other kind of research strategy such as survey or case study), but the word 'experiment' and variations of it appear in the paper.
For one thing, the authors refer to students' practical work as being experiments,
"Laboratory exercises, especially in higher education contexts, often involve training in several different manipulative skills as well as a high information flow, such as from manuals, instructors, output from the experimental equipment, and so forth. If students do not have prior experiences that help them to sort out significant information or reduce the cognitive effort required to understand what is happening in the experiment, they tend to rely on working strategies that help them simply to cope with the situation; for example, focusing only on issues that are of immediate importance to obtain data for later analysis and reflective thought…"
Winberg & Berg, 2007
Now, some student practical work is experimental, where a student is actively looking to see what happens when they manipulate some variable to test a hypothesis. This type of practical work is sometimes labelled enquiry (or inquiry in US spelling). But a lot of school and university laboratory work, however, is undertaken to learn techniques, or (probably more often) to support the learning of taught theory – where it is usually important the learners know what is meant to happen before they begin the laboratory activity.
Winberg and Berg refer to the 'laboratory exercise' as 'the experiment' as though any laboratory work counts as an experiment. In Winberg and Berg's research, students were asked about their "own [titration] experiment", despite the prelab material involving a simulation of the titration process, in advance of which "the theoretical concepts, ideas, and procedures addressed in the simulation exercise had been treated mainly quantitatively during the preceding 1-week instructional sequence". So, the laboratory titration exercise does not seem to be an experiment in the scientific sense of the term.
School children commonly describe all practical work in the lab as 'doing experiments'. It cannot help students learn what an experiment really is when the word 'experiment' has two quite distinct meanings in the science classroom:
experiment(technical) = an empirical test of a hypothesis involving the careful control of variables and observation of the effect on a specified (hypothetised as) dependent variable of changing the variable specified as the independent variable
experiment(casual) = absolutely any practical activity carried out with laboratory equipment
We might describe this second meaning as an alternative conception of 'experiment', a way of understanding that is inconsistent with the scientific meaning. (Just as there are common alternative conceptions of other 'nature of science' concepts such as 'theory').
I would imagine Winberg and Berg were well aware of what an experiment is, although their casual use of language might suggest a lack of rigour in thinking with the term. They refer to having "both control and experiment groups" in their studies, and refer to "the experimental chronology" of their research design. So, they certainly seem to think of their work as a kind of experiment.
Experimental design
In a true experiment, a sample is randomly drawn from a population of interest (say, first year undergraduate chemistry students; or, perhaps, first year undergraduate chemistry students attending Swedish Universities, or… 3) and assigned randomly to the conditions being compared. Providing a genuine form of random assignment is used, then inferential statistical tests can guide on whether any differences found between groups at the end of an experiment should be considered statistically significant. 4
"Statistics can only indicate how likely a measured result would occur by chance (as randomisation of units of analysis to different treatments can only make uneven group composition unlikely, not impossible)…Randomisation cannot ensure equivalence between groups (even if it makes any imbalance just as likely to advantage either condition)"
Inferential statistics can be used to test for statistical significance in experiments – as long as the 'units of analysis' (e.g., students) are randomly assigned to the experimental and control conditions. (Figure from Taber, 2019)
That is, if the are difference that the stats. tests suggests are very unlikely to happen by chance, then they are very unlikely to be due to an initial difference between the groups in the two conditions as long as the groups were the result of random assignment. But that is a very important proviso.
There are two aspects to this need for randomisation:
to be able to suggest any differences found reflect the effects of the intervention, then there should be random assignment to the two (or more) conditions
to be able to suggest the results reflect what would probably would be found in a wider population, the sample should be randomly selected from the population of interest 3
Studies in education seldom meet the requirements for being true experiments (Figure from Taber, 2019)
In education, it is not always possible to use random assignment, so true experiments are then not possible. However, so-called 'quasi-experiments' may be possible where differences between the outcomes in different conditions may be understood as informative, as long as there is good reason to believe that even without random assignment, the groups assigned to the different conditions are equivalent.
In this specific research, that would mean having good reason to believe that without the intervention (the prelab):
students in both groups would have asked overall equivalent (in terms of the analysis undertaken in this study) questions in the lab.;
students in both groups would have been judged as displaying overall equivalent subject knowledge.
Often in research where a true experiment is not possible some kind of pre-testing is used to make a case for equivalence between groups.
Two control groups that were out of control
In Winberg and Berg's research there were two studies where comparisons were made between 'experimental' and 'control' conditions
Study
Experimental
Control
Study 1
n=78: first-year students, following completion of their first chemistry course in 2001
n=97: students who had been interviewed by the researchers during the same course in the previous year
Study 2
n=21 (of 58 in cohort)
n=37 (of 58 in same cohort)
In the first study, a comparison was made between the cohort where the innovation was introduced and a cohort from the previous year. All other things being equal, it seems likely these two cohorts were fairly similar. But in education all thing are seldom equal, so there is no assurance they were similar enough to be considered equivalent.
In the second study
"Students were divided into treatment (n = 21) and control (n = 37) groups. Distribution of students between the treatment and control groups was not controlled by the researchers".
Winberg & Berg, 2007
So, some factor(s) external to the researchers divided the cohort into two groups – and the reader is told nothing about the basis for this, nor even if the two groups were assigned to the treatments randomly.5 The authors report that the cohort "comprised prospective molecular biologists (31%), biologists (51%), geologists (7%), and students who did not follow any specific program (11%)", and so it is possible the division into two uneven sized groups was based on timetabling constraints with students attending chemistry labs sessions according to their availability based on specialism. But that is just a guess. (It is usually better when the reader of a research report is not left to speculate about procedures and constraints.)
What is important for a reader to note is that in these studies:
the researchers were not able to assign learners to conditions randomly;
nor were the researchers able to offer any evidence of equivalence between groups (such as near identical pre-test scores);
so, the requirements for inferring significance from statistical tests were not met;
so, claims in the paper about finding statistically significant differences between conditions cannot therefore be justified given the research design;
and therefore the conclusions presented in the paper are strictly not valid.
If students are not randomly assigned to conditions, then any statistically unlikely difference found at the end of an experiment cannot be assumed to be likely to be due to intervention, rather than some systematic initial difference between the groups. (Figure adapted from Taber, 2019)
This is a shame, because this is in many ways an interesting paper, and much thought and care seems to have been taken about the collection and analysis of meaningful data. Yet, drawing conclusions from statistical tests comparing groups that might never have been similar in the first case is like finding that careful use of a vernier scale shows that after a period of watering plant A, plant A is taller than plant B – having been very careful to make sure plant A was watered regularly with carefully controlled volumes, while plant B was not watered at all – when you did not think to check how tall the two plants were before you started watering plant A.
In such a scenario we might be tempted to assume plant A has actually become taller because it had been watered; but that is just applying what we had conjectured should be the case, and we would be mistaking our expectations for experimental evidence.
Work cited:
Taber, K. S. (2013). Non-random thoughts about research. Chemistry Education Research and Practice, 14(4), 359-362. doi:10.1039/c3rp90009f
Winberg, T. M., & Berg, C. A. R. (2007). Students' cognitive focus during a chemistry laboratory exercise: Effects of a computer-simulated prelab. Journal of Research in Science Teaching, 44(8), 1108-1133. https://doi.org/https://doi.org/10.1002/tea.20217
Notes:
1 The part of the brain where we can consciously mentipulate ideas is called the working memory (WM). Research suggests that WM has a very limited capacity in the sense that people can only hold in mind a very small number of different things at once. (These 'things' however are somewhat subjective – a complex idea that is treated as a single 'thing' in the WM of an expert can overload a novice.) This limit to ~WM is considered to be one of the most substantial constraints on effective classroom learning. This is also, then, one of the key research findings informing the design of effective teaching.
2 The organisation has seemingly spotted that the USA is only one part of the world, and now describes itself as a global organisation for improving science education through research.
3 There is no reason why an experiment cannot be carried out on a very specific population, such as first year undergraduate chemistry students attending a specific Swedish University such a, say, Umea ̊ University. However, if researchers intend their study to have results generalisable beyond their specific research contexts (say, to first year undergraduate chemistry students attending any Swedish University) then it is important to have a representative sample of that population.
4 It might be assumed that scientists, and researchers know what is meant by random, and how to undertake random assignment. Sadly, the literature suggests that in practice the term 'randomly' is sometimes used in research reports to mean something like 'arbitrarily' (Taber, 2013), which fills short of being random.
5 Arguably, even if the two groups were assigned randomly, there is only one 'unit of analysis' in each condition, as they were assigned as groups. That is, for statistical purposes, the two groups have size n=1 and n=1, which would not allow statistical significance to be found: e.g, see 'Quasi-experiment or crazy experiment?'
One of the most fundamental ideas in physics, surely taught in every secondary school science curriculum around the world, is also the focus of one of the most common alternative conceptions documented in science education. Inertia. Much research in the latter part of the twentieth century has detailed how most people have great trouble with this very simple idea.
But that would likely not have surprised the nineteenth century French physicist (and mathematician and philosopher) Henri Poincaré in the least. Over a century ago he had this to say about the subject of Newton's first law, inertia,
"The principle of inertia. A body acted on by no force can only move uniformly in a straight line.
Is this a truth imposed a priori upon the mind? If it were so, how could the Greeks have failed to recognise it? How could they have believed that motion stops when the cause which gave birth to it ceases? Or again that every body if nothing prevents, will move in a circle, the noblest of motions?
If it is said that the velocity of a body can not change if there is no reason for it to change, could it not be maintained just as well that the position of this body can not change, or that the curvature of its trajectory can not change, if no external cause intervenes to modify them?
Is the principle of inertia, which is not an a priori truth, therefore an experimental fact? But has any one ever experimented on bodies withdrawn from the action of every force? and, if so, how was it known that these bodies were subjected to no force?"
Poincaré, 1902/1913/2015
There is quite a lot going on in that quote, so it is worth breaking it down.
The principle of inertia
"The principle of inertia. A body acted on by no force can only move uniformly in a straight line."
Poincaré, 1902/1913/2015
We might today choose to phrase this differently – at least in teaching. Perhaps along the lines that
a body remains at rest, or moving with uniform motion, unless it is acted upon by a net (overall) force
That's a pretty simple idea.
If you want something that is stationary to start moving, you need to apply a force to it. Otherwise it will remain stationary. And:
If you want something that is moving with constant velocity to slow down (decelerate), speed up (accelerate), or change direction, you need to apply a force to it. Otherwise it will carry on moving in the same direction at the same speed.
A simple idea, but one which most people struggle with!
It is worth noting that Poincaré's formulation seems simpler than the versions more commonly presented in school today. He does not make reference to a body at rest; and we might detect a potential ambiguity in what is meant by "can only move uniformly in a straight line".
Is the emphasis:
can only move uniformly in a straight line:
i.e., 〈 can only 〉 〈 move uniformly in a straight line 〉, or
can only move uniformly in a straight line:
i.e., 〈 can only move 〉 〈 uniformly in a straight line 〉
That is, must such a body "move uniformly in a straight line" or must such a body, if moving, "move uniformly in a straight line"? A body acted on by no force may be stationary.
Perhaps this is less ambiguous in the original French? But I suspect that, as a physicist, Poincairé did not, particularly, see the body at rest as being much of a special case.
To most people the distinction between something stationary and something moving is very salient (evolution has prepared us to notice movement). But to a physicist the more important distinction is between any body at constant velocity, and one accelerating* – and a body not moving has constant velocity (of 0 ms-1!)
*and for a physicist accelerating usually includes decelerating, as that is just acceleration with a negative vale, or indeed positive acceleration in a different direction. These 'simplifications' seem very neat – to the initiated (but perhaps not to novices!)
A historical scientific conception
Poincaré then asks:
Is this a truth imposed a priori upon the mind? If it were so, how could the Greeks have failed to recognise it? How could they have believed that motion stops when the cause which gave birth to it ceases?"
Poincaré, 1902/1913/2015
Poincairé asks a rhetorical question: "Is this a truth imposed a priori upon the mind?" Rhetorical, as he immediately suggests the answer. No, it cannot be.
Science is very much an empirical endeavour. The world is investigated by observation, indeed often observation of the effects of interventions (i.e., experiments).
In this way, it diverges from a rationalist approach to understanding the world based on reflection and reasoning that occurs without seeking empirical evidence.
An aside on simulations and perpetual change
Yet, even empirical science depends on some (a priori) metaphysical commitments that cannot themselves be demonstrated by scientific observation (e.g., Taber, 2013). As one example, the famous 'brain in a vat' scenario (that informed films such as The Matrix) asks how we could know that we really experience an external world rather than a very elaborate virtual reality fed directly into our central nervous system (assuming we have such a thing!) 1
Science only makes sense if we believe that the world we experience is an objective reality originating outside our own minds (Image by Gerd Altmann from Pixabay)
Despite this, scientists operate on the assumption this is a physical world (that we all experience), and one that has a certain degree of stability and consistency. 2 The natural scientist has to assume this is not a capricious universe if science (a search for the underlying order of the world) is to make sense!
It may seem this (that we live in is an objective physical world that has a certain degree of stability and consistency) is obviously the case, as our observations of the world find this stability. But not really: rather, we impose an assumption of an underlying stability, and interpret accordingly. The sun 'rises' every day. (We see stability.) But the amount of daylight changes each day. (We observe change, but assume, and look for, and posit, some underlying stability to explain this.)
Continental drift, new comets, evolution of new species and extinction of others, supernovae, the appearance of HIV and COVID, increasing IQ (disguised by periodically renormalising scoring), climate change, the expanding universe, plant growth, senile dementia, rotting fruit, printers running out of ink, lovers falling out of love, et cetera,…are all assumed to be (and subsequently found to be) explainable in terms of underlying stable and consistent features of the world!
But it would be possible to consider nothing stays the same, and seek to explain away any apparent examples of stability!
Parmenides thought change is impossible
Heraclitus though everything was in flux
An a priori?
So Poincaré was asking if the principle of is inertia was something that would appear to us as a given; is inertia something that seems a necessary and obvious feature of the world (which it probably does to most physicists – but that is after years of indoctrination into that perspective).
But, Poincaré was pointing out, we know that for centuries people did not think that objects not subject any force would continue to move with constant velocity.
There were (considered to be) certain natural motions, and these had a teleological aspect. So, heavy objects, that were considered mainly earth naturally fell down to their natural place on the ground. 3 Once there, mission accomplished (so to speak), they would stop moving. No further explanation was considered necessary.
Violent motions were (considered to be) different as they needed an active cause – such as a javelin moving through the air because someone had thrown it. Yet, clearly (it was believed), the athlete could only impart a finite motion to the javelin, which it would soon exhaust, so the javelin would (naturally) stop soon enough.
Today, such ideas are seen as alternative conceptions (misconceptions), but for hundreds of years these ideas were largely taken as self-evident and secure principles describing aspects of the world. The idea that the javelin might carry on moving for ever if it was 'left to its own devices' seemed absurd. (And to most people today who are not physicists or science teachers, it probably still does!)
An interesting question is if, and if so, to what extent, the people who become physicists and physics teachers start out with intuitions more aligned with the principles of physics than most of their classmates.
"Assuming that there is significant variation in the extent to which our intuitive physics matches what we are taught in school, I would expect that most physics teachers are among those to whom the subject seemed logical and made good sense when they were students. I have no evidence for this, but it just seems natural that these students would have enjoyed and continued with the subject.
If I am right about this intuition, then this may be another reason why physics is so hard for some of our students. Not only do they have to struggle with subject matter that seems counterintuitive, but the very people who are charged with helping them may be those who instinctively think most differently from the way in which they do."
Taber, 2004, p.124
Another historical scientific conception
And Poincaré went on:
"Or again that every body if nothing prevents, will move in a circle, the noblest of motions?"
Poincaré, 1902/1913/2015
It was also long thought that in the heavens bodies naturally moved spontaneously in circles – a circle being a perfect shape, and the heavens being a perfect place.
Orbital motion – once viewed to be natural (i.e., not requiring any further explanation) and circular in 'the heavens'. (Image by WikiImages from Pixabay: Body sizes and separations not to the same scale!)
It is common for people to feel that what seems natural does not need further explanation (Watts & Taber, 1996) – even though most of what we consider natural is likely just familiarity with common phenomena. We start noticing how the floor arrests the motion of falling objects very young in life, so by the time we have language to help reflect on this, we simply explain this as motion stopping because the floor was in the way! Similarly, reaction forces are not obvious when an object rests on another – a desk, a shelf, etc – as the object cannot fall 'because it is supported'.
Again, we (sic, wethe initiated) now think that without an acting centripetal force, an orbiting body would move off at a tangent – but that would have seemed pretty bizarre for much of European history.
The idea that bodies moved in circles (as the fixed stars seemed to do) was maintained despite extensive observational evidence collected over centuries that the planets appeared to do something quite different. Today Kepler's laws are taught in physics, including that the solar system's orbiting bodies move (almost) in ellipses. ('Almost', as they bodies perturb each other a little.)
But when Kepler tried to fit observations to theory by adopting Copernicus's 'heliocentric' model of the Earth and planets orbiting the Sun (Earth and other planets, we would say), he still struggled to make progress for a considerable time because of an unquestioned assumption that the planetary motions had to be circular, or some combination of multiple circles.
Learners' alternative conceptions
These historical ideas are of more than historical interest. Many people, research suggests most people, today share similar intuitions.
Objects will naturally come to a stop when they have used up their imparted motion without the need for any forces to act.
Something that falls to the floor does not need a force to act on it to stop it moving, as the ground is in its way.
Moons and planets continue in orbits because there is no overall force acting on them.
The vast majority of learners some to school science holding versions of such alternative conceptions.
The majority of learners also leave school holding versions of such alternative conceptions – even if some of them have mastered the ability to usually respond to physics test questions as if they accepted a different worldview.
The idea that objects soon stop moving once the applied force ceases to act may be contrary to physics, but it is not, of course, contrary to common experience – at least not contrary to common experience as most people perceive it.
Metaphysical principles
Poincaré recognised this.
"If it is said that the velocity of a body can not change if there is no reason for it to change [i.e. the principle of inertia],
could it not be maintained just as well that
the position of this body can not change, or
that the curvature of its trajectorycan not change,
if no external cause intervenes to modify them?"
Poincaré, 1902/1913/2015 (emphasis added)
After all, as Poincairé pointed out, there seems no reason, a priori, that is intuitively, to assume the world must work according to the principle of inertia (though some physicists and science teachers whom have been indoctrinated over many years may have come to think otherwise – of course after indoctrination is not a priori!), rather than assuming, say, that force must act for movement to occur and/or that force must act to change an orbit.
Science as an empirical enterprise
Science teachers might reply, that our initial intuitions are not the point, because myriad empirical tests have demonstrated the principle of inertia. But Poincairé suggested this was strictly not so,
"Is the principle of inertia, which is not an a priori truth, therefore an experimental fact? But has any one ever experimented on bodies withdrawn from the action of every force? and, if so, how was it known that these bodies were subjected to no force?"
Poincaré, 1902/1913/2015
For example, if we accept the ideas of universal gravitation, than anywhere in the universe a body will be subject to gravitational attractions (that is, forces). A body could only be completely free of this by being in a universe of its own with no other gravitating bodies. Then we might think we could test, in principle at least, whether the body "acted on by no force can only move uniformly in a straight line".
Well, apart from a couple of small difficulties. There would be no observers in this universe to see, as we have excluded all other massive bodies. And if this was the only body there, it would be the only frame of reference available – a frame of reference in which it was always stationary. It would always be at the centre of, and indeed would be the extent of, its universe.
Poincaré and pedagogic awareness
Poincaré was certainly not denying the principle of inertia so fundamental to mechanics. But he was showing that he appreciated that a simple principle which seems (comes to seem?) so basic and obvious to the inducted physics expert:
was hard won in the history of science
in not 'given' in intuition
is not the only possible basic principle on which a mechanics (in some other universe) could be based
is contrary to immediate experience (that is, to those who have not been indoctrinated to 'see' resistive forces sch as friction acting everywhere)
could never be entirely demonstrated in a pure form, but rather must be inferred from experimental tests of more complex situations where we will only deduce the principle of inertia if we assume a range of other principles (about the action of gravitational fields, air resistance, etc.)
Poincaré may have been seen as one of the great physicists of his time, but his own expertise certainly did not him appreciating the challenges facing the learner of physics, or indeed the teacher of physics.
Work cited:
Taber, K. S. (2004) Intuitive physics: but whose intuition are we talking about?, Physics Education, 39 (2), pp.123-124.
Watts, M. and Taber, K. S. (1996) An explanatory gestalt of essence: students' conceptions of the 'natural' in physical phenomena, International Journal of Science Education, 18 (8), pp.939-954.
Notes
1 With current human technology we cannot achieve this – even the best virtual worlds clearly do not yet come close to the real one! But that argument falls away if 'the real' world we experience is such a virtual reality created by very advanced technology, and what we think of as virtual worlds are low definition simulations being created within that! (After all, when people saw the first jumpy black-and-white movies, they then came out from the cinema into a colourful, smooth and high definition world.) If you have ever awaken from a dream, only to later realise you are still asleep, and had been dreaming of being asleep in the dream, then you may appreciate how such nesting of worlds could work.
Probably no one actually believes they are a brain in a vat, but how would we know. There is an argument that
1) the evolution of complex life is a very slow process that requires a complex ecosystem, but
2) once humans (or indeed non-humans) have the technology to create convincing virtual worlds this can be done very much more quickly, and with much less resource [i.e., than the evolution of the physical world which within which the programmers of the simulations themselves live]. So,
3) if we are living in a phase of the universe where such technology has been achieved, then we would expect there to be a great many more such virtual worlds than planets inhabited by life forms with the level of self-consciousness to think about whether they are in a simulation.4 So,
4) [if we are living in a phase of the universe where such technology has been achieved] we would be much more likely to be living in one of these worlds (a character in a very complex simulation) than an actual organic being. 5
2 That is, not a simulation where an adolescent programmer is going to suddenly increase gravity or add a new fundamental force just to make things more interesting.
3 Everything on earth was considered to be made up of different proportions of the four elements, which in terms of increasing rarity were earth, water, air and fire. The rocks of the earth were predominately the element earth – and objects that were mainly earth fell to their natural place. (Rarity in this context means the inverse of density, not scarcity.)
4 When I was a child (perhaps in part because I think I started Sunday School before I could start 'proper' school), I used to muse about God being able to create everything, and being omniscient – although I am pretty sure I did not use that term! It seemed to me (and, sensibly, I do not think I shared this at Sunday School) that if God knew everything and was infallible, then he did not need to actually create the world as a physical universe, but rather just think what would happen. For God, that would work just as well, as a perfect mind could imagine things exactly as they would be in exquisite detail and with absolute precision. So, I thought I might just be an aspect of the mind of God – so part of a simulation in effect. This was a comforting rather than worrying thought – surely there is no safer place to be than in the mind of God?
Sadly, I grew to be much less sure of God (the creation seems just as incredible – in the literal sense – either way), but still think that, for God, thinking it would be as good as (if not the same as) making it. I suspect some theologians would not entirely dismiss this.
If I am just a character in someone's simulation, I'd rather it was that of a supreme being than some alien adolescent likely to abandon my world at the first sign of romantic interest from a passing conspecific.
5 Unless we assume a dystopian Matrix like simulation, the technology has to be able to create characters (sub-routines?) with self-awareness – which goes some way beyond just a convincing simulation, as it also requires components complex enough to be convinced about their own existence, as well as the reality of the wider simulation!
Trustworthy research findings are conditional on getting a lot of things right
Keith S. Taber
A good many experimental educational research studies that compare treatments across two classes or two schools are subject to potentially conflating variables that invalidate study findings and make any consequent conclusions and recommendations untrustworthy.
I was looking for research into the effectiveness of P-O-E (predict-observe-explain) pedagogy, a teaching technique that is believed to help challenge learners' alternative conceptions and support conceptual change.
One of the papers I came across reported identifying, and then using P-O-E to respond to, students' alternative conceptions. The authors reported that
The pre-test revealed a number of misconceptions held by learners in both groups: learners believed that salts 'disappear' when dissolved in water (37% of the responses in the 80% from the pre-test) and that salt 'melts' when dissolved in water (27% of the responses in the 80% from the pre-test).
Kibirige, Osodo & Tlala, 2014, p.302
The references to "in the 80%" did not seem to be explained anywhere. Perhaps only 80% of students responded to the open-ended questions included as part of the assessment instrument (discussed below), so the authors gave the incidence as a proportion of those responding? Ideally, research reports are explicit about such matters avoiding the need for readers to speculate.
The authors concluded from their research that
"This study revealed that the use of POE strategy has a positive effect on learners' misconceptions about dissolved salts. As a result of this strategy, learners were able to overcome their initial misconceptions and improved on their performance….The implication of these results is that science educators, curriculum developers, and textbook writers should work together to include elements of POE in the curriculum as a model for conceptual change in teaching science in schools."
Kibirige, Osodo & Tlala, 2014, p.305
This seemed pretty positive. As P-O-E is an approach which is consistent with 'constructivist' thinking that recognises the importance of engaging with learners' existing thinking I am probably biased towards accepting such conclusions. I would expect techniques such as P-O-E, when applied carefully in suitable curriculum contexts, to be effective.
Yet I also have a background in teaching research methods and in acting as a journal editor and reviewer – so I am not going to trust the conclusion of a research study without having a look at the research design.
All research findings are subject to caveats and provisos: good practice in research writing is for the authors to discuss them – but often they are left unmentioned for readers to spot. (Read about drawing conclusions from studies)
Kibirige and colleagues describe their study as a quasi-experiment.
Experimental research into teaching approaches
If one wants to see if a teaching approach is effective, then it seems obvious that one needs to do an experiment. If we can experimentally compare different teaching approaches we can find out which are more effective.
An experiment allows us to make a fair comparison by 'control of variables'.
Identify a representative sample of an identified population
Randomly assign learners in the sample to either an experimental condition or a control condition
Set up two conditions that are alike in all relevant ways, apart from the independent variable of interest
After the treatments, apply a valid instrument to measure learning outcomes
Use inferential statistics to see if any difference in outcomes across the two conditions reaches statistical significance
If it does, conclude that
the effect is likely to due to the difference in treatments
and will apply, on average, to the population that has been sampled
Now, I expect anyone reading this who has worked in schools, and certainly anyone with experience in social research (such as research into teaching and learning), will immediately recognise that in practice it is very difficult to actually set up an experiment into teaching which fits this description.
Nearly always (if indeed not always!) experiments to test teaching approaches fall short of this ideal model to some extent. This does not mean such studies can not be useful – especially where there are many of them with compensatory strengths and weaknesses offering similar findings (Taber, 2019a)- but one needs to ask how closely published studies fit the ideal of a good experiment. Work in high quality journals is often expected to offer readers guidance on this, but readers should check for themselves to see if they find a study convincing.
So, how convincing do I find this study by Kibirige and colleagues?
The sample and the population
If one wishes a study to be informative about a population (say, chemistry teachers in the UK; or 11-12 year-olds in state schools in Western Australia; or pharmacy undergraduates in the EU; or whatever) then it is important to either include the full population in the study (which is usually only feasible when the population is a very limited one, such as graduate students in a single university department) or to ensure the sample is representative.
Kibirige and colleagues refer to their participants as a sample
"The sample consisted of 93 Grade 10 Physical Sciences learners from two neighbouring schools (coded as A and B) in a rural setting in Moutse West circuit in Limpopo Province, South Africa. The ages of the learners ranged from 16 to 20 years…The learners were purposively sampled."
Kibirige, Osodo & Tlala, 2014, p.302
Purposive sampling means selecting participants according to some specific criteria, rather than sampling a population randomly. It is not entirely clear precisely what the authors mean by this here – which characteristics they selected for. Also, there is no statement of the population being sampled – so the reader is left to guess what population the sample is a sample of. Perhaps "Grade 10 Physical Sciences" students – but, if so, universally, or in South Africa, or just within Limpopo Province, or indeed just the Moutse West circuit? Strictly the notion of a sample is meaningless without reference to the population being sampled.
A quasi-experiment
A key notion in experimental research is the unit of analysis
"An experiment may, for example, be comparing outcomes between different learners, different classes, different year groups, or different schools…It is important at the outset of an experimental study to clarify what the unit of analysis is, and this should be explicit in research reports so that readers are aware what is being compared."
In a true experiment the 'units of analysis' (which in different studies may be learners, teachers, classes, schools, exam. papers, lessons, textbook chapters, etc.) are randomly assigned to conditions. Random assignment allows inferential statistics to be used to directly compare measures made in the different conditions to determine whether outcomes are statistically significant. Random assignment is a way of making systematic differences between groups unlikely (and so allows the use of inferential statistics to draw meaningful conclusions).
Random assignment is sometimes possible in educational research, but often researchers are only able to work with existing groupings.
Kibirige, Osodo & Tlala describe their approach as using a quasi-experimental design as they could not assign learners to groups, but only compare between learners in two schools. This is important, as means that the 'units of analysis' are not the individual learners, but the groups: in this study one group of students in one school (n=1) is being compared with another group of students in a different school (n=1).
The authors do not make it clear whether they assigned the schools to the two teaching conditions randomly – or whether some other criterion was used. For example, if they chose school A to be the experimental school because they knew the chemistry teacher in the school was highly skilled, always looking to improve her teaching, and open to new approaches; whereas the chemistry teacher in school B had a reputation for wishing to avoid doing more than was needed to be judged competent – that would immediately invalidate the study.
Compensating for not using random assignment
When it is not possible to randomly assign learners to treatments, researchers can (a) use statistics that take into account measurements on each group made before, as well as after, the treatments (that is, a pre-test – post-test design); (b) offer evidence to persuade readers that the groups are equivalent before the experiment. Kibirige, Osodo and Tlala seek to use both of these steps.
Do the groups start as equivalent?
Kibirige, Osodo and Tlala present evidence from the pre-test to suggest that the learners in the two groups are starting at about the same level. In practice, pre-tests seldom lead to identical outcomes for different groups. It is therefore common to use inferential statistics to test for whether there is a statistically significant difference between pre-test scores in the groups. That could be reasonable, if there was an agreed criterion for deciding just how close scores should be to be seen as equivalent. In practice, many researchers only check that the differences do not reach statistical significance at the level of probability <0.05: that it they look to see if there are strong differences, and, if not, declare this is (or implicitly treat this as) equivalence!
This is clearly an inadequate measure of equivalence as it will only filter out cases where there is a difference so large it is found to be very unlikely to be a chance effect.
If we want to make sure groups start as 'equivalent', we cannot simply look to exclude the most blatant differences. (Original image by mcmurryjulie from Pixabay)
We can see this in the Kibirige and colleagues' study where the researchers list mean scores and standard deviations for each question on the pre-test. They report that:
"The results (Table 1) reveal that there was no significant difference between the pre-test achievement scores of the CG [control group] and EG [experimental group] for questions (Appendix 2). The p value for these questions was greater than 0.05."
Kibirige, Osodo & Tlala, 2014, p.302
Now this paper is published "licensed under Creative Commons Attribution 3.0 License" which means I am free to copy from it here.
According to the results table, several of the items (1.2, 1.4, 2.6) did lead to statistically significantly different response patterns in the two groups.
Most of these questions (1.1-1.4; 2.1-2.8; discussed below) are objective questions, so although no marking scheme was included in the paper, it seems they were marked as correct or incorrect.
So, let's take as an example question 2.5 where readers are told that there was no statistically significant difference in the responses of the two groups. The mean score in the control group was 0.41, and in the experimental group was 0.27. Now, the paper reports that:
"Forty nine (49) learners (31 males and 18 females) were from school A and acted as the experimental group (EG) whereas the control group (CG) consisted of 44 learners (18 males and 26 females) from school B."
Kibirige, Osodo & Tlala, 2014, p.302
So, according to my maths,
Correct responses
Incorrect responses
School A (49 students)
(0.27 ➾) 13
36
School B (44 students)
(0.41 ➾) 18
26
pre-test results for an item with no statistically significant difference between groups
"The achievement of the EG and CG from pre-test results were not significantly different which suggest that the two groups had similar understanding of concepts" (p.305). Pre-test results for an item with no statistically significant difference between groups (offered as evidence of 'similar' levels of initial understanding in the two groups)
While, technically, there may have been no statistically significant difference here, I think inspection is sufficient to suggest this does not mean the two groups were initially equivalent in terms of performance on this item.
Data that is normally distributed falls on a 'bell-shaped' curve
(Image by mcmurryjulie from Pixabay)
Inspection of this graphic also highlights something else. Student's t-test (used by the authors to produce the results in their table 1), is a parametric test. That means it can only be used when the data fit certain criteria. The data sample should be randomly selected (not true here) and normally distributed. A normal distribution means data is distributed in a bell-shaped Gaussian curve (as in the image in the blue circle above).If Kibirige, Osodo & Tlala were applying the t-test to data distributed as in my graphic above (a binary distribution where answers were either right or wrong) then the test was invalid.
So, to summarise, the authors suggest there "was no significant difference between the pre-test achievement scores of the CG and EG for questions", although sometimes there was (according to their table); and they used the wrong test to check for this; and in any case lack of statistical significance is not a sufficient test for equivalence.
I should note that the journal does claim to use peer review to evaluate submissions to see if they are ready for publication!
Comparing learning gains between the two groups
At one level equivalence might not be so important, as the authors used an ANCOVA (Analysis of Covariance) test which tests for difference at post-test taking into account the pre-test. Yet this test also has assumptions that need to be tested for and met, but here seem to have just been assumed.
However, to return to an even more substantive point I made earlier, as the learners were not randomly assigned to the two different conditions /treatments, what should be compared are the two school-based groups (i.e., the unit of analysis should be the school group) but that (i.e., a sample of 1 class, rather than 40+ learners, in each condition) would not facilitate using inferential statistics to make a comparison. So, although the authors conclude
"that the achievement of the EG [taking n=49] after treatment (mean 34. 07 ± 15. 12 SD) was higher than the CG [taking n =44] (mean 20. 87 ± 12. 31 SD). These means were significantly different"
Kibirige, Osodo & Tlala, 2014, p.303
the statistics are testing the outcomes as if 49 units independently experienced one teaching approach and 44 independently experienced another. Now, I do not claim to be a statistics expert, and I am aware that most researchers only have a limited appreciation of how and why stats. tests work. For most readers, then, a more convincing argument may be made by focussing on the control of variables.
Controlling variables in educational experiments
The ability to control variables is a key feature of laboratory science, and is critical to experimental tests. Control of variables, even identification of relevant variables, is much more challenging outside of a laboratory in social contexts – such as schools.
In the case of Kibirige, Osodo & Tlala's study, we can set out the overall experimental design as follows
Anything other than teaching approach which might make a difference to student learning
Variables in Kibirige, Osodo & Tlala's study
The researchers set up the two teaching conditions, measure learning gains, and need to make sure any other factors which might have an effect on learning outcomes, so called confounding variables, are controlled so the same in both conditions.
Of course, we cannot be sure what might act as a confounding variable, so in practice we may miss something which we do not recognise is having an effect. Here are some possibilities based on my own (now dimly recalled) experience of teaching in school.
The room may make a difference. Some rooms are
spacious,
airy,
well illuminated,
well equipped,
away from noisy distractions
arranged so everyone can see the front, and the teacher can easily move around the room
Some rooms have
comfortable seating,
a well positioned board,
good acoustics
…
Others, not so.
The timetable might make a difference. Anyone who has ever taught the same class of students at different times in the week might (will?) have noticed that a Tuesday morning lesson and a Friday afternoon lesson are not always equally productive.
Class size may make a difference (here 49 versus 44).
Could gender composition make a difference? Perhaps it was just me, but I seem to recall that classes of mainly female adolescents had a different nature than classes of mainly male adolescents. (And perhaps the way I experienced those classes would have been different if I had been a female teacher?) Kibirige, Osodo and Tlala report the sex of the students, but assuming that can be taken as a proxy for gender, the gender ratios were somewhat different in the two classes.
The gender make up of the classes was quite different: might that influence learning?
School differences
A potentially major conflating variable is school. In this study the researchers report that the schools were "neighbouring" and that
Having been drawn from the same geographical set up, the learners were of the same socio-cultural practices.
Kibirige, Osodo & Tlala, 2014, p.302
That clearly makes more sense than choosing two schools from different places with different demographics. But anyone who has worked in schools will know that two neighbouring schools serving much the same community can still be very different. Different ethos, different norms, and often different levels of outcome. Schools A and B may be very similar (but the reader has no way to know), but when comparing between groups in different schools it is clear that school could be a key factor in group outcome.
The teacher effect
Similar points can be made about teachers – they are all different! Does ANY teacher really believe that one can swap one teacher for another without making a difference? Kibirige, Osodo and Tlala do not tell readers anything about the teachers, but as students were taught in their own schools the default assumption must be that they were taught by their assigned class teachers.
Teachers vary in terms of
skill,
experience,
confidence,
enthusiasm,
subject knowledge,
empathy levels,
insight into their students,
rapport with classes,
beliefs about teaching and learning,
teaching style,
disciplinary approach
expectations of students
…
The same teacher may perform at different levels with different classes (preferring to work with different grade levels, or simply getting on/not getting on with particular classes). Teachers may have uneven performance across topics. Teachers differentially engage with and excel in different teaching approaches. (Even if the same teacher had taught both groups we could not assume they were equally skilful in both teaching conditions.)
Teacher variable is likely to be a major difference between groups.
Meta-effects
Another conflating factor is the very fact of the research itself. Students may welcome a different approach because it is novel and a change from the usual diet (or alternatively they may be nervous about things being done differently) – but such 'novelty' effects would disappear once the new way of doing things became established as normal. In which case, it would be an effect of the research itself and not of what is being researched.
Perhaps even more powerful are expectancy effects. If researchers expect an innovation to improve matters, then these expectations get communicated to those involved in the research and can themselves have an affect. Expectancy effects are so well demonstrated that in medical research double-blind protocols are used so that neither patients nor health professionals they directly engage with in the study know who is getting which treatment.
School effect Teacher effect Class size Gender composition of teaching groups Relative novelty of the two teaching approaches …
Variables in Kibirige, Osodo & Tlala's study
Now, of course, these problems are not unique to this particular study. The only way to respond to teacher and school effects of this kind is to do large scale studies, and randomly assign a large enough number of schools and teachers to the different conditions so that it becomes very unlikely there will be systematic differences between treatment groups.
A good many experimental educational research studies that compare treatments across two classes or two schools are subject to potentially conflating variables that invalidate study findings and make any consequent conclusions and recommendations untrustworthy (Taber, 2019a). Strangely, often this does not seem to preclude publication in research journals. 1
Advice on controls in scientific investigations:
I can probably do no better than to share some advice given to both researchers, and readers of research papers, in an immunology textbook from 1910:
"I cannot impress upon you strongly enough never to operate without the necessary controls. You will thus protect yourself against grave errors and faulty diagnoses, to which even the most competent investigator may be liable if he [or she] fails to carry out adequate controls. This applies above all when you perform independent scientific investigations or seek to assess them. Work done without the controls necessary to eliminate all possible errors, even unlikely ones, permits no scientific conclusions.
I have made it a rule, and would advise you to do the same, to look at the controls listed before you read any new scientific papers… If the controls are inadequate, the value of the work will be very poor, irrespective of its substance, because none of the data, although they may be correct, are necessarily so."
It seems clear that in this study there is no strict 'control' of variables, and the 'control' group is better considered just a comparison group. The authors tell us that:
"the control group (CG) taught using traditional methods…
the CG used the traditional lecture method"
Kibirige, Osodo & Tlala, 2014, pp.300, 302
This is not further explained, but if this really was teaching by 'lecturing' then that is not a suitable approach for teaching school age learners.
This raises two issues.
There is a lot of evidence that a range of active learning approaches (discussion work, laboratory work, various kinds of group work) engages and motivates students more than whole lessons spent listening to a teacher. Therefore any approach which basically involves a mixture of students doing things, discussing things, engaging with manipulatives and resources as well as listening to a teacher, tends to be superior to just being lectured. Good science teaching normally involves lessons sequenced into a series of connected episodes involving different types of student activity (Taber, 2019b). Teacher presentations of the target scientific account are very important, but tend to be effective when embedded in a dialogic approach that allows students to explore their own thinking and takes into account their starting points.
So, comparing P-O-E with lectures (if they really were lectures) may not tell researchers much about P-O-E specifically, as a teaching approach. A better test would compare P-O-E with some other approach known to be engaging.
"Many published studies argue that the innovation being tested has the potential to be more effective than current standard teaching practice, and seek to demonstrate this by comparing an innovative treatment with existing practice that is not seen as especially effective. This seems logical where the likely effectiveness of the innovation being tested is genuinely uncertain, and the 'standard' provision is the only available comparison. However, often these studies are carried out in contexts where the advantages of a range of innovative approaches have already been well demonstrated, in which case it would be more informative to test the innovation that is the focus of the study against some other approach already shown to be effective."
The second issue is more ethical than methodological. Sometimes in published studies (and I am not claiming I know this happened here, as the paper says so little about the comparison condition) researchers seem to deliberately set up a comparison condition they have good reason to expect is not effective: such as asking a teacher to lecture and not include practical work or discussion work or use of digital learning technologies and so forth. Potentially the researchers are asking the teacher of the 'control' group to teach less effectively than normally to bias the experiment towards their preferred outcome (Taber, 2019a).
This is not only a failure to do good science, but also an abuse of those learners being deliberately subjected to poor teaching. Perhaps in this study the class in School B was habitually taught by being lectured at, so the comparison condition was just what would have occurred in the absence of the research, but this is always a worry when studies report comparison conditions that seem to deliberately disadvantage students. (This paper does not seem to report anything about obtaining voluntary informed consent from participants, nor indeed about how access to the schools was negotiated. )
"In most educational research experiments of the type discussed in this article, potential harm is likely to be limited to subjecting students (and teachers) to conditions where teaching may be less effective, and perhaps demotivating…It can also potentially occur in control conditions if students are subjected to teaching inputs of low effectiveness when better alternatives were available. This may be judged only a modest level of harm, but – given that the whole purpose of experiments to test teaching innovations is to facilitate improvements in teaching effectiveness – this possibility should be taken seriously."
Even leaving aside all the concerns expressed above, the results of a study of this kind depends upon valid measurements. Assessment items must test what they claim to test, and their analysis should be subject to quality control (and preferably blind to which condition a script being analysed derives form). Kibirige, Osodo and Tlala append the test they used in the study (Appendix 2, pp.309-310), which is very helpful in allowing readers to judge at least its face validity. Unfortunately, they do not include a mark/analysis scheme to show what they considered responses worthy of credit.
"The [Achievement Test] consisted of three questions. Question one consisted of five statements which learners had to classify as either true or false. Question two consisted of nine [sic, actually eight] multiple questions which were used as a diagnostic tool in the design of the teaching and learning materials in addressing misconceptions based on prior knowledge. Question three had two open-ended questions to reveal learners' views on how salts dissolve in water (Appendix 1 [sic, 2])."
Kibirige, Osodo & Tlala, 2014, p.302
"Question one consisted of five statements which learners had to classify as either true or false."
Question 1 is fairly straightforward.
1.2: Strictly all salts do dissolve in water to some extent. I expect that students were taught that some salts are insoluble. Often in teaching we start with simple dichotomous models (metal-non metal; ionic-covalent; soluble-insoluble; reversible – irreversible) and then develop these to more continuous accounts that recognise difference of degree. It is possible here then that a student who had learnt that all salts are soluble to some extent might have been disadvantaged by giving the 'wrong' ('True') response…
…although[sic] , actually, there is perhaps no excuse for answering 'True' ('All salts can dissolve in water') here as a later question begins "3.2. Some salts does [sic] not dissolve in water. In your own view what happens when a salt do [sic] not dissolve in water".
Despite the test actually telling students the answer to this item, it seems only 55% of the experimental group, and 23% of the control group obtained the correct answer on the post test – precisely the same proportions as on the pre-test!
1.4: Seems to be 'False' as the ions exist in the salt and are not formed when it goes into solution. However, I am not sure if that nuance of wording is intended in the question.
Question 2 gets more interesting.
"Question two consisted of nine multiple questions" (seven shown here)
I immediately got stuck on question 2.2 which asked which formula (singular, not 'formula/formulae', note) represented a salt. Surely, they are all salts?
I had the same problem on 2.4 which seemed to offer three salts that could be formed by reacting acid with base. Were students allowed to give multiple responses? Did they have to give all the correct options to score?
Again, 2.5 offered three salts which could all be made by direct reaction of 'some substances'. (As a student I might have answered A assuming the teacher meant to ask about direct combination of the elements?)
At least in 2.6 there only seemed to be two correct responses to choose between.
Any student unsure of the correct answer in 2.7 might have taken guidance from the charges as shown in the equation given in question 2.8 (although indicated as 2.9).
How I wished they had provided the mark scheme.
The final question in this section asked students to select one of three diagrams to show what happens when a 'mixture' of H2O and NaCl in a closed container 'react'. (In chemistry, we do not usually consider salt dissolving as a reaction.)
Diagram B seemed to show ion pairs in solution (but why the different form of representation?) Option C did not look convincing as the chloride ions had altogether vanished from the scene and sodium seemed to have formed multiple bonds with oxygen and hydrogens.
So, by a process of elimination, the answer is surely A.
But components seem to be labelled Na and Cl (not as ions).
And the image does not seem to represent a solution as there is much too much space between the species present.
And in salt solution there are many water molecules between solvated ions – missing here.
And the figure seems to show two water molecules have broken up, not to give hydrogen and hydroxide ions, but lone oxygen (atoms, ions?)
And why is the chlorine shown to be so much larger in solution than it was in the salt? (If this is meant to be an atom, it should be smaller than the ion, not larger. The real mystery is why the chloride ions are shown so much smaller than smaller sodium ions before salvation occurs when chloride ions have about double the radii of sodium ions.)
So diagram A is incredible, but still not quite as crazy an option as B and C.
This is all despite
"For face validity, three Physical Sciences experts (two Physical Sciences educators and one researcher) examined the instruments with specific reference to Mpofu's (2006) criteria: suitability of the language used to the targeted group; structure and clarity of the questions; and checked if the content was relevant to what would be measured. For reliability, the instruments were piloted over a period of two weeks. Grade 10 learners of a school which was not part of the sample was used. Any questions that were not clear were changed to reduce ambiguity."
Kibirige, Osodo & Tlala, 2014, p.302
One wonders what the less clear, more ambiguous, versions of the test items were.
Reducing 'misconceptions'
The final question was (or, perhaps better, questions were) open-ended.
I assume (again, it would be good for authors of research reports to make such things explicit) these were the questions that led to claims about the identified alternative conceptions at pre-test.
"The pre-test revealed a number of misconceptions held by learners in both groups: learners believed that salts 'disappear' when dissolved in water (37% of the responses in the 80% from the pre-test) and that salt 'melts' when dissolved in water (27% of the responses in the 80% from the pre-test)."
Kibirige, Osodo & Tlala, 2014, p.302
As the first two (sets of) questions only admit objective scoring, it seems that this data can only have come from responses to Q3. This means that the authors cannot be sure how students are using terms. 'Melt' is often used in an everyday, metaphorical, sense of 'melting away'. This use of language should be addressed, but it may not be a conceptual error
As the first two (sets of) questions only admit objective scoring, it seems that this data can only have come from responses to Q3. This means that the authors cannot be sure how students are using terms. 'Melt' is often used in an everyday, metaphorical, sense of 'melting away'. This use of language should be addressed, but it may not (for at least some of these learners) be a conceptual error as much as poor use of terminology. .
To say that salts disappear when they dissolve does not seem to me a misconception: they do. To disappear means to no longer be visible, and that's a fair description of the phenomenon of salt dissolving. The authors may assume that if learners use the term 'disappear' they mean the salt is no longer present, but literally they are only claiming it is not directly visible.
Unfortunately, the authors tell us nothing about how they analysed the data collected form their test, so the reader has no basis for knowing how they interpreted student responded to arrive at their findings. The authors do tell us, however, that:
"the intervention had a positive effect on the understanding of concepts dealing with dissolving of salts. This improved achievement was due to the impact of POE strategy which reduced learners' misconceptions regarding dissolving of salts"
Kibirige, Osodo & Tlala, 2014, p.305
Yet, oddly, they offer no specific basis for this claim – no figures to show the level at which "learners believed that salts 'disappear' when dissolved in water …and that salt 'melts' when dissolved in water" in either group at the post-test.
'disappear' misconception
'melt' misconception
pre-test: experimental group
not reported
not reported
pre-test: comparison group
not reported
not reported
pre-test: total
(0.37 x 0.8 x 93 =) 24.5 (!?)
(0.27 x 0.8 x 93 =) 20
post-test: experimental group
not reported
not reported
post-test: comparison group
not reported
not reported
post-test: total
not reported
not reported
Data presented about the numbers of learners considered to hold specific misconceptions said to have been 'reduced' in the experimental condition
It seems journal referees and the editor did not feel some important information was missing here that should be added before publication.
In conclusion
Experiments require control of variables. Experiments require random assignment to conditions. Quasi-experiments, where random assignment is not possible, are inherently weaker studies than true experiments.
Control of variables in educational contexts is often almost impossible.
Studies that compare different teaching approaches using two different classes each taught by a different teacher (and perhaps not even in the same school) can never be considered fair comparisons able to offer generalisable conclusions about the relative merits of the approaches. Such 'experiments' have no value as research studies. 1
Such 'experiments' are like comparing the solubility of two salts by (a) dropping a solid lump of 10g of one salt into some cold water, and (b) stirring a finely powdered 35g sample of the other salt into hot propanol; and watching to see which seems to dissolve better.
Only large scale studies that encompass a wide range of different teachers/schools/classrooms in each condition are likely to produce results that are generalisable.
The use of inferential statistical tests is only worthwhile when the conditions for those statistical tests are met. Sometimes tests are said to be robust to modest deviations from such acquirements as normality. But applying tests to data that do not come close to fitting the conditions of the test is pointless.
Any research is only as trustworthy as the validity of its measurements. If one does not trust the measuring instrument or the analysis of measurement data then one cannot trust the findings and conclusions.
The results of a research study depend on an extended chain of argumentation, where any broken link invalidates the whole chain. (From 'Critical reading of research')
So, although the website for the Mediterranean Journal of Social Science claims "All articles submitted …undergo to a rigorous double blinded peer review process", I think the peer reviewers for this article were either very generous, very ignorant, or simply very lazy. That may seem harsh, but peer review is meant to help authors improve submissions till they are worthy of appearing in the literature, and here peer review has failed, and the authors (and readers of the journal) have been let down by the reviewers and the editor who ultimately decided this study was publishable in this form.
If I asked a graduate student (or indeed an undergraduate student) to evaluate this paper, I would expect to see a response something along these sorts of lines:
I still think P-O-E is a very valuable part of the science teacher's repertoire – but this paper can not contribute anything to support to that view.
Work cited:
Kibirige, I., Osodo, J., & Tlala, K. M. (2014). The effect of predict-observe-explain strategy on learners' misconceptions about dissolved salts. Mediterranean Journal of Social Sciences, 5(4), 300-310.
1 A lot of these invalid experiments get submitted to research journals, scrutinised by editors and journal referees, and then get published without any acknowledgement of how they fall short of meeting the conditions for a valid experiment. (See, for example, examples discussed in Taber 2019a.) It is as if the mystique of experiment is so great that even studies with invalid conclusions are considered worth publishingas long as the authors did an experiment.
I imagine the physicist Henri Poincaré was entirely serious when he suggested,
"the principle of relative motion, which forces itself upon us for two reasons:
first, the commonest experience confirms it, and
second, the contrary hypothesis is singularly repugnant to the mind."
Henri Poincaré (mathematician, physicist, philosopher)
Perhaps Poincaré was reflecting how two opposing schools of philosophical thought had disagreed on wherever the primary source of human knowledge was experience (the empiricists) or pure reasoning (the rationalists), but elsewhere in the same text Poincairé (1902/1913/2015) dismisses the idea that the laws of physics can be obtained by simple reflection on human intuitions. Such intuitions can lead us astray.
If he is being consistent then, surely "the contrary hypothesis is [only] singularly repugnant to the mind" because "the commonest experience confirms…the principle of relative motion". That is, suggestions that are clearly contrary to our common experience – such as, perhaps, the earth is moving? – are readily rejected as being nonsensical and ridiculous.
If that is so, then Poincaré was not really offering two independent lines of argument as his second reason was dependent upon his first.
This put me in mind of some comments of Kryten, a character in the sci-fi series 'Red Drawf',
{responding to a crew suggestion "Why don't we drop the defensive shields?"}
"A superlative suggestion, sir, with just two minor flaws.
One, we don't have any defensive shields, and
two, we don't have any defensive shields.
Now I realise that, technically speaking, that's only one flaw but I thought it was such a big one it was worth mentioning twice."
Kryten (mechanoid assigned to the mining spaceship Red Dwarf)
or alternatively,
{responding to the crew suggestion "I got it! We laser our way through [the 53 doors from here to the science deck]!"}
Ah, an excellent plan, sir, with only two minor drawbacks.
One, we don't have a power source for the lasers; and
two, we don't have any lasers.
Kryten
French physicist Poincaré'Red Dwarf' character, Kryten
The principle of relative motion
What Poincairé meant by 'the principle of relative motion' was that
"The motion of any system must obey the same laws, whether it be referred to fixed axes, or to moveable axes carried along in a rectilinear and uniform motion."
the principle of relative motion
In other words, imagine a train passing a station at 10 ms-1, in which a naughty physics student throws a pencil eraser of mass m with a force of F at another passenger sitting in front on him; while a model physics student observes this from the stationary station [sic] platform.
The student on the train would consider the eraser to be at rest before being thrown, and can explore its motion by taking u=0 ms-1 and applying some laws summarised by
F=ma,
v=u+at,
v2=u2+2as,
s=ut +1/2at2…
From the frame or reference of someone in the the station it is the train that moves, (Image by StockSnap from Pixabay) but……From the frame of reference of the train (or tram), it seems to be the rest of the world that is moving past (Image by Pasi Mämmelä from Pixabay)
The student on the platform would observe the eraser to initially be moving at 10 ms-1, but could calculate what would happen using the same set of equations, but taking u=10 ms-1
Any values of v calculated would be consistent across the two frames (when allowing for the 10 ms-1 discrepancy) and other values calculated (s, t) would be the same.
This reflects the relativity principle of Galileo which suggests that there is no absolute way of determining whether a body is moving at constant velocity or stationary: rather what appears to be the case depends on one's frame of reference.
We might think that obviously it is the platform which is really stationary, as our intuition is that the earth under our feet is stationary ground. Surely we could tell if the ground moves?
We can directly feel acceleration, and we can sometimes feel the resistance to motion (the air on our face if we cycle, even at a constant velocity), but the idea that we can directly tell whether or not we are moving is an alternative conception.
For centuries the idea of a moving earth was largely considered ridiculous as experience clearly indicated otherwise. But if someone was kidnapped whilst asleep (please note, this would be illegal and is not being encouraged) and awoke in a carriage that had been set up to look like a hotel bedroom, on a train moving with constant velocity, they would not feel they were in motion. Indeed anyone who as travelled on a train at night when nothing is visible outside the carriage might well have experienced the impression that the train is stationary whilst it moves at a steady rate.
Science has shown us that there are good reasons to think that the earth is spinning, and orbiting the sun, as part of the solar system which moves through the galaxy, so who is to say what is really stationary? We cannot tell (and the question may be meaningless).
Who is to say what is moving – we can only make relative judgements? (Image by Drajt from Pixabay)
Source cited:
Poincaré, H. (1902/1913/2015). Science and Hypothesis (G. B. Halstead, Trans.). In The Foundations of Science. Cambridge University Press. {I give three dates because Poincaré published his book in French in 1902, and it was later published in an English translation in 1913, but I have a 2015 edition.}
A well-known Palestinian proverb reminds us that we do not fatten the cow simply by repeatedly weighing it. But, sadly, teachers and others working in education commonly get so fixated on assessment that it seems to become an end in itself.
Images by Clker-Free-Vector-Images from PixabayOpenClipart-Vectors and Deedster from Pixabay
A research study using P-O-E
I was reading a report of a study that adopted the predict-observe-explain, P-O-E, technique as a means to elicit "high school students' conceptions about acids and bases" (Kala, Yaman & Ayas, 2013, p.555). As the name suggests, P-O-E asks learners to make a prediction before observing some phenomenon, and then to explain their observations (something that can be specially valuable when the predictions are based on strongly held intuitions which are contrary to what actually happens).
Kala and colleagues begin the introduction to their paper by stating that
"In any teaching or learning approach enlightened by constructivism, it is important to infer the students' ideas of what is already known"
Kala, Yaman & Ayas, 2013, p.555
Constructivism?
Constructivism is a perspective on learning that is informed by research into how people learn and a great many studies into student thinking and learning in science. A key point is how a learner's current knowledge and understanding influences how they make sense of teaching and what they go on to learn. Research shows it is very common for students to have 'alternative conceptions' of science topics, and often these conceptions either survive teaching or distort how it is understood.
The key point is that teachers who teach the science without regard to student thinking will often find that students retain their alternative ways of thinking, so constructivist teaching is teaching that takes into account and responds to the ideas about science topics that students bring to class.
If teachers are to take into account, engage with, and try to reshape, learners ideas about science topics, then they need to know what those ideas are. Now there is a vast literature reporting alternative conceptions in a wide range of science topics, spread across thousands or research reports – but no teacher could possibly find time to study them all. There are books which discuss many examples and highlight some of the most common alternative conceptions (including one of my own, Taber, 2014)
However, in any class studying some particular topic there will nearly always be a spread of different alternative conceptions across the students – including some so idiosyncratic that they have never been reported in any literature. So, although reading about common misconceptions is certainly useful to prime teachers for what to look out for, teachers need to undertake diagnostic assessment to find out about the thinking of their own particular students.
There are many resources available to support teachers in diagnostic assessment, and some activities (such as using concept cartoons) that are especially useful at revealing student thinking.
Diagnostic assessment, assessment to inform teaching, is carried out at the start of a topic, before the teaching, to allow teachers to judge the learners' starting points and any alternative conceptions ('misconceptions') they may have. It can therefore be considered aligned to formative assessment ('assessment for learning') which is carried out as part of the learning process, rather than summative assessment (assessment of leaning) which is used after studying to check, score, grade and certify learning.
P-O-E as a learning activity…
P-O-E can best support learning in topics where it is known learners tend to have strongly held, but unhelpful, intuitions. The predict stage elicits students' expectations – which, when contrary to the scientific account, can be confounded by the observe step. The 'cognitive conflict' generated by seeing something unexpected (made more salient by having been asked to make a formal prediction) is thought to help students concentrate on that actual phenomena, and to provide 'epistemic relevance' (Taber, 2015).
Epistemic relevance refers to the idea that students are learning about things they are actually curious about, whereas for many students following a conventional science course must be experienced as being presented with the answers to a seemingly never-ending series questions that had never occurred to them in the first place.
Students are asked to provide an explanation for what they have observed which requires deeper engagement than just recording an observation. Developing explanations is a core scientific practice (and one which is needed before another core scientific practice – testing explanations – is possible).
To be most effective, P-O-E is carried out in small groups, as this encourages the sharing, challenging and justifying of ideas: the kind of dialogic activity thought to be powerful in supporting learners in developing their thinking, as well as practicing their skills in scientific argumentation. As part of dialogic teaching such an open-forum for learners' ideas is not an end in itself, but a preparatory stage for the teacher to marshal the different contributions and develop a convincing argument for how the best account of the phenomenon is the scientific account reflected in the curriculum.
Constructivist teaching is informed by learners' ideas, and therefore relies on their elicitation, but that elicitation is never the end in itself but is a precursor to a customised presentation of the canonical account.
Group work also has another function – if the activity is intended to support diagnostic assessment, then the teacher can move around the room listening in to the various discussions and so collecting valuable information on what students think and understand. When assessment is intended to inform teaching it does not need to be about students completing tests and teachers marking them – a key principle of formative assessment is that it occurs as a natural part of the teaching process. It can be based on productive learning activities, and does not need marks or grades – indeed as the point is to help students move on in their thinking, any kind of formal grading whilst learning is in progress would be inappropriate as well as a misuse of teacher time.
Probing students' understandings about acid-base chemistry
The constructivist model of learning applies to us all: students, teachers, professors, researchers. Given what I have written above about P-O-E, about diagnostic assessment, and dialogic approaches to learning, I approached Kala and colleagues' paper with expectations about how they would have carried out their project.
These authors do report that they were able to diagnose aspects of student thinking about acids and bases, and found some learning difficulties and alternative conceptions,
"it was observed that eight of the 27 students had the idea that the "pH of strong acids is the lowest every time," while two of the 27 students had the idea that "strong acids have a high pH." Furthermore, four of the 27 students wrote the idea that the "substance is strong to the extent to which it is burning," while one of the 27 students mentioned the idea that "different acids which have equal concentration have equal pH."
Kala, Yaman & Ayas, 2013, pp.562-3
The key feature seems to be that, as reported in previous research, students conflate acid concentration and acid strength (when it is possible to have a high concentration solution of a weak acid or a very dilute solution of a strong acid).
Yet some aspects of this study seemed out of alignment with the use of P-O-E.
The best research style?
One feature was the adoption of a positivistic approach to the analysis,
Although there has been no reported analyzing procedure for the POE, in this study, a different [sic] analyzing approach was offered taking into account students' level of understanding… Data gathered from the written responses to the POE tasks were analyzed and divided into six groups. In this context, while students' prediction were divided into two categories as being correct or wrong, reasons for predictions were divided into three categories as being correct, partially correct, or wrong.
Kala, Yaman & Ayas, 2013, pp.560
Group
Prediction
Reasons
❀
correct
correct
❁
correct
partially correct
✯
correct
wrong
✿
wrong
correct
❂
wrong
partially correct
✤
wrong
wrong
"the written responses to the POE tasks were analyzed and divided into six groups"
There is nothing inherently wrong with doing this, but it aligns the research with an approach that seems at odds with the thinking behind constructivist studies that are intended to interpret a learner's thinking in its own terms, rather than simply compare it with some standard. (I have explored this issue in some detail in a comparison of two research studies into students' conceptions of forces – see Taber, 2013, pp.58-66.)
In terms of research methodology we might say it seem to be conceptualised within the 'wrong' paradigm for this kind of work. It seems positivist (assuming data can be unambiguously fitted into clear categories), nomothetic (tied to 'norms' and canonical answers) and confirmatory (testing thinking as matching model responses or not), rather than interpretivist (seeking to understand student thinking in its own terms rather than just classifying it as right or wrong), idiographic (acknowledging that every learner's thinking is to some extent unique to them) and discovery (exploring nuances and sophistication, rather than simply deciding if something is acceptable or not).
The approach used seemed more suitable for investigating something in the science laboratory, than the complex, interactive, contextualised, and ongoing life of classroom teaching. Kala and colleagues describe their methodology as case study,
"The present study used a case study because it enables the giving of permission to make a searching investigation of an event, a fact, a situation, and an individual or a group…"
Kala, Yaman & Ayas, 2013, pp.558
A case study?
Case study is a naturalistc methodology (rather than involving an intervention, such as an experiment), and is idiographic, reflecting the value of studying the individual case. The case is one from among many instances of its kind (one lesson, one school, one examination paper, etc.), and is considered as a somewhat self contained entity yet one that is embedded in a context in which it is to some extent entangled (for example, what happens in a particular lesson is inevitably somewhat influenced by
the earlier sequence of lessons that teacher taught that class {the history of that teacher with that class},
the lessons the teacher and student came from immediately before this focal lesson,
the school in which it takes place,
the curriculum set out to be followed…)
Although a lesson can be understood as a bounded case (taking place in a particular room over a particular period of time involving a specified group of people) it cannot be isolated from the embedding context.
Case study – study of one instance from among many
As case study is idiographic, and does not attempt to offer direct generalisation to other situations beyond that case, a case study should be reported with 'thick description' so a reader has a good mental image of the case (and can think about what makes it special – and so what makes it similar to, or different from, other instances the reader may be interested in). But that is lacking in Kala and colleagues' study, as they only tell readers,
"The sample in the present study consisted of 27 high school students who were enrolled in the science and mathematics track in an Anatolian high school in Trabzon, Turkey. The selected sample first studied the acid and base subject in the middle school (grades 6 – 8) in the eighth year. Later, the acid and base topic was studied in high school. The present study was implemented, based on the sample that completed the normal instruction on the acid and base topic."
Kala, Yaman & Ayas, 2013, pp.558-559
The reference to a sample can be understood as something of a 'reveal' of their natural sympathies – 'sample' is the language of positivist studies that assume a suitably chosen sample reflects a wider population of interest. In case study, a single case is selected and described rather than a population sampled. A reader is left to rather guess what population being sampled here, and indeed precisely what the 'case' is.
Clearly, Kala and colleagues elicited some useful information that could inform teaching, but I sensed that their approach would not have made optimal use of a learning activity (P-O-E) that can give insight into the richness, and, sometimes, subtlety of different students' ideas.
Individual work
Even more surprising was the researchers' choice to ask students to work individually without group discussion.
"The treatment was carried out individually with the sample by using worksheets."
Kala, Yaman & Ayas, 2013, p.559
This is a choice which would surely have compromised the potential of the teaching approach to allow learners to explore, and reveal, their thinking?
I wondered why the researchers had made this choice. As they were undertaking research, perhaps they thought it was a better way to collect data that they could readily analyse – but that seems to be choosing limited data that can be easily characterised over the richer data that engagement in dialogue would surely reveal?
Assessment habits
All became clear near the end of the study when, in the final paragraph, the reader is told,
"In the present study, the data collection instruments were used as an assessment method because the study was done at the end of the instruction/ [sic] on the acid and base topics."
Kala, Yaman & Ayas, 2013, p.571
So, it appears that the P-O-E activity, which is an effective way of generating the kind of rich but complex data that helps a teacher hone their teaching for a particular group, was being adopted, instead, as means of a summative assessment. This is presumably why the analysis focused on the degree of match to the canonical science, rather than engaging in interpreting the different ways of thinking in the class. Again presumably, this is why the highly valuable group aspect of the approach was dropped in favour of individual working – summative assessment needs to not only grade against norms, but do this on the basis of each individual's unaided work.
An activity which offers great potential for formative assessment (as it is a learning activity as well as a way of exploring student thinking); and that offers an authentic reflection of scientific practice (where ideas are presented, challenged, justified, and developed in response to criticism); and that is generally enjoyed by students because it is interactive and the predictions are 'low stakes' making for a fun learning session, was here re-purposed to be a means of assessing individual students once their study of a topic was completed.
Kala and colleagues certainly did identify some learning difficulties and alternative conceptions this way, and this allowed them to evaluate student learning. But I cannot help thinking an opportunity was lost here to explore how P-O-E can be used in a formative assessment mode to inform teaching:
diagnostic assessment as formative assessment can inform more effective teaching
diagnostic assessment as summative assessment only shows where teaching has failed
Yes, I agree that "in any teaching or learning approach enlightened by constructivism, it is important to infer the students' ideas of what is already known", but the point of that is to inform the teaching and so support student learning. What were Kala and colleagues going to do with their inferences about students ideas when they used the technique as "an assessment method … at the end of the instruction".
As the Palestinian adage goes, you do not fatten up the cow by weighing it, just as you do not facilitate learning simply by testing students. To mix my farmyard allusions, this seems to be a study of closing the barn door after the horse has already bolted.
Work cited
Kala, N., Yaman, F., & Ayas, A. (2013). The effectiveness of predict-observe-explain technique in probing students' understanding about acid-base chemistry: a case for the concepts of pH, pOH, and strength. International Journal of Science and Mathematics Education, 11(3), 555-574. https://doi.org/10.1007/s10763-012-9354-z
"…I am older than I once was And younger than I'll be But that's not unusual No, it isn't strange After changes upon changes We are more or less the same After changes we are more or less the same…"
From the lyrics of 'The Boxer' (Simon and Garfunkel song) by Paul Simon
In a recent post I discussed the treatment of Newtonian forces in a book (Thomson, 2005) about the history of natural theology (a movement which sought to study the natural world as kind of religious observance – seeking to glorify God by the study of His works) and its relationship to the development of evolutionary theory.
The book was written by a prestigious scientist, who had held Professorships at both Yale in the US and at Oxford. Yet the book contained some erroneous physics – 'howlers' of the kind that are sometimes called 'schoolboy errors' (as presumably most schoolgirls would be careful not to make them?)
My point is not to imply that this is a poor read – the book has much to commend it, and I certainly thought it was worth my time. I found it an informative read, and I have no reason to assume that the author's scholarship in examining the historical sources was was not of the highest level – even if his understanding of some school physics seemed questionable. I think this highlights two features of science:
Science is so vast that research scientists setting out to write 'popular' science books for a general readership risk venturing into areas outside their specialist knowledge – areas where they may lack expertise 1
Some common alternative conceptions ('misconceptions') are so insidious that we confidently feel we understand the science we have been taught whilst continuing to operate with intuitions at odds with the science.
Out of specialism
In relation to the first point, I previously highlighted a reference to "Einstein's relativity theory" being part of quantum physics, and later in the book I found another example of a non-physicist confusing two ideas that may seem similar to the non-specialist but which to a physicist should not be confused:
"In the 1930s, Arthur Holmes worked out the geology of the mechanism [underpinning plate tectonics] and the fact that the earth's inner heat (like that of the sun) comes from atomic fission." p.190
Thomson, 2005: 190
The earth contains a good deal of radioactive material which, through atomic fission, heats up the earth from within. This activity has contributed to the, initially hot, earth cooling much more slowly than had once been assumed – most notably according to modelling undertaken by Thomson's namesake, Lord Kelvin.2 Kelvin did not know about nuclear fission.
But the sun is heated by a completely different kind of nuclear reaction: fusion. The immense amount of energy 'released' during this process enables stars to burn for billions of years without running out of hydrogen fuel.3
Lord Kelvin did not know about that either, leading to him suggesting
"…on the whole most probable that the sun has not illuminated the earth for 100,000,000 years, and almost certain that he has not done so for 500,000,000 years"
Thomson, 1862
Kelvin suggested this was 'almost' but not 'absolutely' certain – a good scientist should always keep an open mind to the possibility of having missed something (take note, BBC's Nick Robinson).
We now think the sun has been 'illuminating' for about 4 600 000 000 years, almost ten times as long as Kelvin's upper limit. It may seem strange that a serious scientist should refer to the sun as 'he', but this kind of personification was once common in scientific writings.
The first atomic weapons were based on fission processes of the kind used in nuclear power stations.
Hydrogen bombs are much more devastating still, making use of fusion as occurs deep in the sun.
(Image by Gerd Altmann from Pixabay)
A non-scientist may feel this conflation of fission and fusion is a minor technical detail. But it is a very significant practical distinction.
For one thing the atomic bombs that were used to devastate Hiroshima and Nagasaki were fission devices. The next generation of atomic weapons, the 'hydrogen bombs' were very much more powerful – to the extent that they used a fission device as a kind of detonator to set off the main bomb! It is these weapons, fusion weapons, which mimic the processes at the centre of stars such as the sun.
…The rusty wire that holds the cork that keeps the anger in Gives way and suddenly it's day again The sun is in the east Even though the day is done Two suns in the sunset, hmph Could be the human race is run…
From the lyrics of 'Two suns in the sunset' (Pink Floyd song) by Roger Waters
In terms of peaceful technologies, fission-based nuclear power stations, whilst not using fossil fuels, have been a major concern because of the highly radioactive waste which will remain a high health risk for many thousands of years, and because of the dangers of radiation leaks – very real risks as shown by the Three Mile Island (USA) and Windscale (England) accidents, and much more seriously at Fukushima (Japan) and, most infamously, Chernobyl (then USSR, now Ukraine). There are also serious health and human rights issues dogging the mining of uranium ore, which is, of course, a declining resource.
For decades scientists have been trying to develop, as an alternative, nuclear fusion based power generation which would be a source of much cleaner and sustainable power supplies. This has proved very challenging because the conditions under which fusion takes place are so much more extreme. Critically, no material can hold the plasma at the extreme temperatures, so it has to be magnetically suspended well away from the containment vessel 'walls'.
The tenacious nature of some misconceptions
My second point, the insidious nature of some common alternative conceptions, is a challenge for science teachers as simply giving clear, accurate presentations with good examples may not be enough to bring about change in well-established and perhaps intuitive ways of thinking, even when students study hard and think they have learnt what has been taught.
I suggested this was reflected in Prof. Thomson's text (Keith, that is, not Sir William) in his use of references to Newton's ideas about force and motion. Prof. Thomson was not as a biologist therefore seeking to avoid referring to physics, but rather actively engaging with Newton's notions of inertia and the action of forces to make his points. Yet, also, seemingly misusing Newtonian mechanics because of a flawed understanding. Likely, as with many students, Prof. Thomson's intuitive physics was so strong that although he had studied Newton's laws, and can state them, when he came to apply them his own 'common-sense' conceptions of force and motion insidiously prevailed.
The point is not that Prof. Thomson has got the physics wrong (as research suggests most people do!) but that he was confident enough in his understanding to highlight Newtonian physics in his writing and, in effect, seek to teach his readers about it.
Newton's laws
What are commonly known as 'Newton' three laws of motion' can be glossed simply as:
N1: When no force is acting, an object does not change its motion: if stationary, it remains stationary; if moving, it carries on moving at the same speed in the same direction.
Indeed, this is also true if forces are acting, but they cancel because they are balanced, i.e.,
N1': When no net (overall, resultant) force is acting, an object does not change its motion: if stationary, it remains stationary; if moving, it carries on moving at the same speed in the same direction.
N2: When a net force is acting on a body it changes its motion in a way determined by the magnitude and direction of the force. (The change in velocity takes place in the direction of the force, and at a rate depending on the magnitude of the force).
So, if the force acts along the direction of motion, then the speed will change but not direction; but if the force acts in any other direction it will lead to a change in direction.
Strictly, the law relates to the 'rate of change of momentum' but assuming the mass of the body is fixed, we can think in terms of changes of velocity. 4
N3: Forces are interactions between two bodies/objects (that attract or repel each other): the same size force acts on both. (This is sometimes unfortunately phrased as 'every action having an equal and opposite reaction') 5.
These (perhaps) seem relatively simple, but there are complications in applying them. Very simply, the first law,when applied to moving bodies does not seem to fit our experience (moving bodies often seem to come to a stop by themselves – due to forces that we do not always notice).
The second law relates an applied force to a process of change, but it is very easy to instead think of the applied force directly leading to an outcome. That is people often equate the change in direction with the final direction. The change occurs in the direction of the force: that does not mean the final direction is the direction of the force.
The third law is commonly misapplied by assuming that if 'forces come in pairs' these will be balanced and cancel out. But they cannot cancel out because they are acting on the two bodies. (If your friend hits you in the eye after one too many pedantic complaints about her science writing you cannot avoid a black eye simply by hitting her back just as hard!)
A N3 force 'pair' does not balance out!
Often objects are in equilibrium because the forces acting on them are balanced. But they are never in equilibrium just because a force on them is also acting on another body! An apple hangs from a tree because the branch pulls it up the same amount as its weight pulls it down: these are two separate forces, each of which is also acting on the other body involved (the branch, and the earth, respectively).
"Any trajectory other than a straight line must be the result of multiple forces acting together."
"the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun…
"a Newtonian balance of forces… rocks: gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again"
The first two statements are simply wrong according to conventional physics. Curved paths are often the result of a single force acting. The earth and moon orbit because they are both the subject of unbalanced forces.
Those two statements are contrary to N1 and N2.
The third statement seemed to suggest that a balance of forces was somehow considered to bring about changes. The suggestion appeared to be that a cycle of changes might be due to a balance of forces. But I acknowledged that "this reference to Hutton's ideas seems to preview a more detailed treatment of the new geology in a later chapter in the book (that I have not yet reached), so perhaps as I read on I will find a clearer explanation of what is meant by these changes being based on a theory of balance of forces".
Now I have finished the book, I wanted to address this.
A sort of balance
Prof. Thomson discusses developing ideas in geology about how the surface of the earth came to have its observed form. Today we are familiar with modern ideas about the structure of the earth, and continental drift, and most people have seen this represented in various ways.
Image by Venita Oberholster from PixabayImage by Clker-Free-Vector-Images from PixabayOriginal images by by Michel Müller from Pixabay
However, it was once widely assumed that the earth's surface was fairly static , but had been shaped by violent events in the distant past – a view sometimes called 'catastrophism'. One much referenced catastrophe was the flood associated with the biblical character Noah (of Ark fame) that was sometimes considered to have been world-wide deluge. (Those who considered this were aware that this required a source of water beyond normal rainfall – such as perhaps vast reservoirs of water escaping from underground).
The idea that the earth was continually changing, and that forces that acted continuously over vast periods of time could slowly (much too slowly for us to notice) lead to the formation of, for example, mountain ranges seemed less feasible.
Yet we now understand how the tectonic plates float on a more fluid layer of material and how these plates slowly collide or separate with the formation of new crust where they move apart. Vast forces are at work and change is constant, but there are cyclic processes such that ultimately nothing much changes.
Well, nothing much changes on a broad perspective. Locally of course, changes may be substantial: land may become submerged, or islands appear from the sea; mountains or great valleys may appear – albeit very, very slowly. But crust that is subsumed in one place will be balanced by crust formed elsewhere. And – just as walking from one side of a small boat to another will lead to one side rising out of the water, whilst the opposite side sinks deeper into the water – as land is raised in one place it will sink elsewhere.
This is the kind of model that scientists started to develop, and which Prof. Thomson discusses.
"[Dr John Woodward (1665-1728) produced] "an ingenious theory, parts of it quite modern, parts simply seventeenth century sophistry within a Newtonian metaphor. Woodward's earth, post deluge, is stable, but not in fact unchanging. This is possible because it is in a sort of balance – a dynamic balance between opposing forces."
Thomson, 2005: 156
Plus ça change, plus c'est la même chose
James Hutton (1726 – 1797) was one of the champions of this 'uniformitarianism',
"Hutton's earth is in a constant state of flux due to processes acting over millions of years as mountains are eroded by rain and frost. In turn, the steady raising up of mountains, balances their steady reduction through erosion.
…for Hutton the evidence of the rocks demonstrated a cyclic history powered by Newtonian steady-state dynamics: the more it changed, the more it stayed the same." p.181
Thomson, 2005: 181
The more it changed, the more it stayed the same: plus ça change, plus c'est la même chose. This, of course, is an idiom that has found resonance with many commentators on the social, as well as the physical, world,
"…A change, it had to come We knew it all along We were liberated from the fold, that's all And the world looks just the same And history ain't changed 'Cause the banners, they all flown in the last war … There's nothing in the street Looks any different to me And the slogans are effaced, by-the-bye And the parting on the left Is now parting on the right And the beards have all grown longer overnight…"
From the lyrics of 'Won't get fooled again' (The Who song), by Pete Townsend
Steady states
So, there are vast forces acting, but the net effect is a planet which stays substantially the same over long periods of time. Which might be considered analogous to a body which is subject to very large forces, but in such a configuration that they cancel.
Where Prof. Thomson is in danger of misleading his reader is in confusing a static equilibrium and a macroscopic overall steady state that is the result of many compensating disturbances. This is an important difference when we consider energy and not just the forces acting.
A steady state can be maintained by nothing happening, or by several things happening which effectively compensate.
If we consider a very heavy mass sitting on a very study table, then the mass has a large weight, but does not fall because the table exerts a balancing upward reaction force. Although large forces are acting, nothing happens. In physics terms, no work is done. 6
Now consider a sealed cylinder, perfectly insulted and shielded from its surroundings, containing some water, air and too much salt to fully dissolve. It would reach a stead state where the
the mass of undissolved salt is constant
the height of the solution in the tube is constant
On a macroscopic level, nothing then happens – it is all pretty boring (especially as if the cylinder was perfectly insulated we would not be able to monitor it anyway!)
Actually, all the time,
salt is dissolving
salt is precipitating
gases from the air are dissolving in the solution
gases are leaving the solution
water is evaporating into the air
water vapour is condensing
But the rates of 1 and 2 are the same; the rates of 3 and 4 are the same; and the rates of 5 and 6 are the same. In terms of molecules and ions, there is a lot of activity – but in overall terms, nothing changes: we have a steady state, due to the dynamic equilibria between dissolving and precipitating; between dissolving and degassing; and between evaporation and condensation.
This activity is possible because of the inherent energy of the particles. In the various interactions between these particles a molecule is slowed here, an ion is released from electrical bonds – and so. But no energy transfer takes placeto or from the system, it is only constantly redistributed among the ensemble of particles. No work is done.
Cycling is hard work
But macroscopic stable states maintained by cyclic processes are not like that. A key difference is that in the geological cycles there are significant frictional effects. In our sealed cylinder, the processes will continue indefinitely as the energy of the system is constant. In the geological systems, change is only maintained because there is source of power – the sun drives the water cycle, radioactive decay in effect drives the rock cycle.
Work is done in forming new crust under the sea between two plates. More work is done pushing one plate beneath another at a plate boundary. It does not matter if the compensating changes were produced by identical magnitude forces pushing in opposite directions – these are not balanced forces in the sense of cancelling out (they act on different masses of material) – if they had been, nothing would have happened.
You cannot move tectonic plates around without doing a great deal of work – just as you cannot cycle effortlessly by using a circular track that brings you back to where you started, even though when cycling in one direction the ground was pushing you one way, and on the way back the ground was pushing you in the opposite direction! (Your tyres pushed on the track, and as Newton's third law suggests, it pushed back on the tyres in the opposite direction – but those equal forces did not cancel as they were acting on different things: or you would not have moved.)
Perhaps Prof. Thomson understands this, but his language is certainly likely to mislead readers:
"Hooke realised that there was a balance of forces: while the geological strata were being formed and mountains were raised up, at the same time the land was constantly being eroded…"
Thomson, 2005: 179
No, there was not a balance of forces.
It could be that Prof. Thomson's use of the phrase 'balance of forces' is only intended as a metaphor or an analogy. 7 However, he also repeats errors he had made earlier in the book
"the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun"
"any trajectory other than a straight line must be the result of multiple forces acting together"
which suggests a genuine confusion about how forces act.
One of these mistakes is that planetary orbits (which require a net {unbalanced} force), are due to 'opposing forces',
"…Paley's tortured dancing on the heads of all these metaphysical pins is pre-shadowing of modern ecological thinking and a metaphysical extension of Hooke and Newton's explanation of planetary orbits in terms of opposing forces, or Woodward's theory of matter, or Hutton's geology – it is the living world as a dynamic system of force and counterforce, of checks and balances." p.242
Thomson, 2005: 242 (my emphasis)
The other was that a single force cannot lead to a curved path,
"…the philosophical concept of reduction, namely that any complex system can be reduced to the operation of simple causes. Thus the parabolic trajectory of a projectile is the product of two straight-line forces acting on each other [sic];…" p.264
Thomson, 2005: 264 (my emphasis)
Forces are interactions between bodies, they are abstractions and do not act on each other. The parabolic path is due to a single constant force acting on a body that is already moving (but not in the direction of the applied force). It can be seen as the result of the combination of a force (acting according to N2) and the body's existing inertia (i.e., N1). Prof. Thomson seems to be thinking of the motion itself as corresponding to a force, where Newton suggested that it is only a change of motion that corresponds to a force.
However, whilst Prof. Thomson is wrong, he is in good company – as one of the most common alternative conceptions reported is assuming that a moving body must be subject to a force. Which, as I pointed out last time, is not so daft as in everyday experience cars and boats and planes only keep on moving as long as their propulsion systems function (to balance resistive forces); and footballs and cricket balls and javelins that do not have a source of motive power (to overcome resistive forces) soon fall to earth. So, these are understandable and, in one sense, very forgiveable slips. It is just unfortunate they appear in an otherwise informative book about science.
Sources cited:
Thomson, K. (2005). The Watch on the Heath: Science and religion before Darwin. HarperCollins.
Thomson, W. (1862). On the Age of the Sun's Heat. Macmillan's Magazine, 5, 388-393.
Thorn, C. E., & Welford, M. R. (1994). The Equilibrium Concept in Geomorphology. Annals of the Association of American Geographers, 84(4), 666-696. http://www.jstor.org/stable/2564149
Notes
1 Although there are plenty of 'academic' books in many fields of scholarship (usually highly focused so the author is writing about their specialist work), the natural sciences tend to be communicated and debated in research journals. Most books written by scientists tend to be for a more general audience – and publishers expect popular science books to appeal to a wide readership, so these books are likely to have a much broader scope than academic monographs.
2 When he was ennobled, William Thomson chose to be called Baron Kelvin – after his local river, the river Kelvin. So the SI unit of temperature is named, indirectly, after a Scottish River.
Kelvin's reputation was such that when he modelled the cooling earth and suggested the planet was less that a 100 000 000 years old, this caused considerable concerns given that geologists were suggesting that much longer had been needed for it to have reached its present state.
4 The rate of change of momentum is proportional to the magnitude of the applied force and takes place in the direction of the applied force.
As momentum is mv, and as mass is usually assumed fixed (if the motion is well below light speeds) 'the rate of change of momentum' is the mass times the rate of change of the velocity – or ma. (F=ma.)
The key point about direction is that it is not that the body moves in the direction of the force, but the change of momentum (so change of velocity) is in the direction or the force.
As the body's momentum is a vector, and the change in momentum is a vector, the new momentum is the vector sum of these two vectors: new momentum = old momentum + change in momentum.
The object's new direction after being deflected by a force is in the direction of the new momentum
5 When there is force between two bodies (let's call them A, B) the force acting on body B is the same size as the force acting on body A, but is anti-parallel in direction.
The force between the earth and the sun acts on both (not shown to scale)
6 This is an ideal case.
A real table would not be perfectly rigid. A real table would initially distort ever so slightly with the area under the mass being ever so slightly compressed, and the weight dropping to an ever so slightly lower level. The very slight lowering of the weight does a tiny amount of work compressing the table surface.
Then, nothing more happens, and no more work is done.
7 Thorn and Welford (1994) have referred to "the fuzzy and frequently erroneous use of the term…equilibrium in geomorphology" (p.861), and how an 1876 introduction of the "concept of dynamic equilibrium resembles the balance-of-forces equilibrium that appears in dynamics, but by analogy rather than formal derivation" (p.862).
Being a science professor is no assurance of understanding Newton's mechanics
Keith S. Taber
…this author had just written that all matter is in uniform motion unless acted upon by an external force but did not seem to appreciate that any matter acted upon by an external force will not be in uniform motion
I started a new book today. 'The Watch on the Heath. Science and Religion before Darwin' had been on my pile of books to read for a while (as one can acquire interesting titles faster than find time to actually read them).
'The Watch on the Heath'
by Prof. Keith Thomson
The title is a reference to the analogy adopted at the start of William Paley's classic book on natural theology. Paley (1802) argued that if one was out walking across a heath and a foot struck an object on the ground, one would make very different assumptions if the object transpired to be a stone or a pocket watch. The stone would pass without much thought – there was no great mystery about how it came to be on the heath. But a pocket watch is an intricate mechanism composed of a multitude of especially shaped and arranged pieces fashioned from different materials. A reasonable person could not think it was an arbitrary and accidentally collated object – rather it clearly had a purpose, and so had a creator – a watchmaker.
Paley developed a detailed argument based on the analogy that organisms are like intricate mechanisms that offer obvious evidence of having been designed (Images by Thomas Wolter and Gerd Altmann from Pixabay)
Paley used this as an analogy for the complexity of the living world. Analogies are often used by teachers and science communicators as a means of making the unfamiliar familiar – a way of suggesting something that is being introduced is actually like something the audience already knows about and feels comfortable with.
Paley was doing something a little different – his readers would already know about both watches and living things, and he was developing the analogy to make an argument about the nature of living things as being designed. (Living things would be familiar, but Paley wanted to invite his reader to think about them in a way they might find unfamiliar.) According to this argument, organisms were so complex that, by analogy with a watch, it followed they also were created for a purpose, and by a creator.
Even today, Paley's book is an impressive read. It is 'one long argument' (as Darwin said of his 'Origin of Species') that collates a massive amount of evidence about the seeming design of human anatomy and the living world. Paley was not a scientist in the modern sense, and he was not even a naturalist who collected natural history specimens. He was a priest and philosopher / theologian who clearly thought that publishing his argument was important enough to require him to engage in such extensive scholarship that in places the volume gives the impression of being a medical textbook.
Paley's work was influential and widely read, but when Darwin (1859) presented his own long argument for evolution by natural selection there began to be a coherent alternative explanation for all that intricate complexity. By the mid-twentieth century a neo-Darwinian synthesis (incorporating work initiated by Mendel, developments in statistics, and the advent of molecular biology) made it possible to offer a feasible account that did not need a watch-maker who carefully made his or her creatures directly from a pre-designed pattern. Richard Dawkins perverted Paley's analogy in calling one of his books 'The Blind Watchmaker' reflecting the idea that evolution is little more than the operation of 'blind' chance.
Arguably, Darwin's work did nothing to undermine the possibility of a great cosmic architect and master craft-person having designed the intricacies of the biota – but only showed the subtlety required of such a creator by giving insight into the natural mechanisms set up to slowly bring about the productions. (The real challenge of Darwin's work was that it overturned the idea that there was any absolute distinction between humans and the rest of life on earth – if humans are uniquely in the image of God then how does that work in relation to the gradual transition from pre-human ancestors to the first humans?)
Arguably Darwin said nothing to undermine the omnipotence of God, only the arrogance of one branch of the bush of life (i.e., ours) to want to remake that God in their image. Anyway, there are of course today a range of positions taken on all this, but this was the context for my reading some questionable statements about Newtonian mechanics.
My reading went well till I got to p.27. Then I was perturbed. It started with a couple of quibbles. The first was a reference to
"…the modern world of quantum physics, where Einstein's relativity and Heisenberg's uncertainty reign."
Thomson, 2005: 27
"Er, no" I thought. Relativity and quantum theory are not only quite distinct theories, but, famously, the challenge of finding a way to make these two areas of physics, relativity theory and quantum mechanics, consistent is seen as a major challenge. The theories of relativity seem to work really well on the large scale and quantum theory works really well on the smallest scales, but they do not seem to fit together. "Einstein's relativity" is not (yet, at least) found within the "world of quantum physics".
Still, this was perhaps just a rhetorical flourish.
The Newtonian principle of inertia
But later in the same paragraph I read about how,
"Newton…showed that all matter is in uniform motion (constant velocity, including a velocity of zero) unless acted upon by an external force…Newton showed that an object will remain still or continue to move at a constant speed in the same direction unless some external force changes things."
Thomson, 2005: 27
This is known as Newton's first law of motion (or the principle of inertia). Now, being pedantic, I thought that surely Newton did notshow this.
It is fair to say, I suggest, that Newton suggested this, proposed it, mooted it; perhaps claimed it was the case; perhaps showed it was part of a self-consistent description – but I am not sure he demonstrated it was so.
Misunderstanding Newton's first law
This is perhaps being picky and, of itself, hardly worth posting about, but this provides important background for what I read a little later (indeed, still in the same paragraph):
"Single forces always act in straight lines, not circles. Any trajectory other than a straight line must be the result of multiple forces acting together."
Thomson, 2005: 27
No!
The first part of this is fair enough – a force acts between two bodies (say the earth and the sun) and is considered to act along a 'line of action' (such as the line between the centres of mass of the earth and the sun). In the Newtonian world-view, the gravitational force between the earth and sun acts on both bodies along that line of action. 1
However, the second sentence ("any trajectory other than a straight line must be the result of multiple forces acting together") is completely wrong.
These two sentences are juxtaposed as though there is a logical link: "Single forces always act in straight lines, not circles. [So therefore] any trajectory other than a straight line must be the result of multiple forces acting together." This only follows if we assume that an object must always be moving in the direction of a force acting on it. But Newton's second law tells us that acceleration (and so the change in velocity) occurs in the direction of the force.
This is confusing the sense of a change with its outcome – a bit like thinking that a 10 m rise in sea level will lead to the sea being 10 m deep, or that if someone 'puts on 20 kilos' they will weigh 200 N. A 'swing to Labour' in an election does not assure Labour of a victory unless the parties were initially on par.
The error here is like assuming that any debit from a bank account must send it overdrawn: taking £10 from a bank account means there will be £10 less in the account, but not necessary that the balance becomes -£10!
Changing direction is effortless (if there is an external force acting)
Whenever a single force acts on a moving object where the line of action does not coincide with the object's direction of travel then the object will change direction. (That is, a single force will only not lead to a change of direction in the very special case where the force aligns with or directly against to the direction of travel.) So, electrons in a cathode ray tube can be shown to follow a curved path when a (single) magnetic force is applied, and an arrow shot from a castle battlement horizontally will curve down to the grounds because of the (single) effect of gravitational force. (There are frictional forces acting as well, but they only modify the precise shape of that curve which would still be found if the castle was on a planet with no atmosphere – as long as the archer could hold her breath long enough to get the arrow away.)
The lyrics of a popular song declare "arc of a diver – effortlessly". 2 But diving into a pool is only effortless (once you have pushed off) because the diver is pulled into an arc by their gravitational attraction with the earth – so even if you dive at an angle above the horizontal, a single force is enough to change your direction and bring you down.
So, there is a mistake in the science here. Either the author has simply made a slip (which can happen to anyone) or he is operating with an alternative conception inconsistent with Newton's laws. The same can presumably be said about any editor or copy editor who checked the manuscript for the publisher.
That might not be so unlikely – as force and motion might be considered the prototype case of a science topic where there are common alternative conceptions. I have seen estimates of 80%+ of people having alternative conceptions inconsistent with basic Newtonian physics. After all, in everyday life, you give something a pull or a push, and it usually moves a bit, but then always come to a stop. In our ordinary experience stones, footballs, cricket balls, javelins, paper planes, darts – or anything else we might push or pull – fail to move in a straight line at a constant speed for the rest of eternity.
That does not mean Newton was wrong, but his ideas were revolutionary because he was able to abstract to situations where the usual resistive forces that are not immediately obvious (friction, air resistance, viscosity) might be absent. That is, ideal scenarios that probably never actually occur. (Thus my questioning above whether Newton really 'showed' rather than postulated these principles.)
So, it is not surprising an author might hold a common alternative conception ('misconception') that is widely shared: but the author had written that
all matter is in uniform motion unless acted upon by an external force
yet did not seem to appreciate the corollary that
any matter acted upon by an external force will not be in uniform motion
So, it seems someone can happily quote Newton's laws of motion but still find them so counter-intuitive that they do not apply them in their thinking. Again, this reflects research which has shown that graduates who have studied physics and done well in the examinations can still show alternative conceptions when asked questions outside the formal classroom setting. It is as if they learn the formalism for the exams, but never really believe it (as, after all, real life constantly shows us otherwise).
So, this is all understandable, but it seems unfortunate in a science book that is seeking to explain the science to readers. At this point I decided to remind myself who had written the book.
We all have alternative conceptions
Keith Thomson is a retired academic, an Emeritus Fellow at Kellog College Oxford, having had an impressive career including having been a Professor of Biology at Yale University and later Director of the Oxford University Museum and Professor of Natural History. So, here we have a highly successful academic scientist (not just a lecturer in some obscure university somewhere – a professor at both Yale and Oxford), albeit with expertise in the life sciences, who seems to misunderstand the basic laws of physics that Newton postulated back in 1687.
Prof. Thomson seems to have flaws in his knowledge in this area, yet is confident enough of his own understanding to expose his thinking in writing a science book. This, again, is what we often find in science teaching – students who hold alternative conceptions may think they understand what they have been taught even though their thinking is not consistent with the scientific accounts. (This is probably true of all of us to some degree. I am sure there must be areas of science where I am confident in my understanding, but where that confidence is misplaced. I likely have misconceptions in topics areas where Prof. Thomson has great expertise.)
A balance of forces?
This could have been just a careless slip (of the kind which once made often looks just right when we reread our work multiple times – I know this can happen). But, over the page, I read:
"…in addition to the technical importance of Newton's mathematics, the concept of 'a balance of forces' keeping the moon circling the earth and the earth in orbit around the sun, quickly became a valuable metaphor…"
Thomson, 2005: 27
Again – No!
If there is 'balance of forces' then the forces effectively cancel, and there is no net force. So, as "all matter is in uniform motion (constant velocity, including a velocity of zero) unless acted upon by an external force", a body subject to a balance of forces continues in "uniform motion (constant velocity…)" – that is, it continues in a straight line at a constant speed. It does not circle (or move in an ellipse). 3
Again, this seems to be an area where people commonly misunderstand Newton's principles, and operate with alternative conceptions. Learners often think that Newton's third law (sometimes phrased in terms of 'equal and opposite forces') implies there will always be balanced forces!
The reason the moon orbits the earth, and the reason the earth orbits the sun, in the Newtonian world-view is because in each case the orbiting body is subject to a single force which is NOT balanced by any countering force. As the object is "acted upon by an external force" (which is not balanced by any other force) it does not move "in uniform motion" but constantly changes direction – along its curved orbit. According to Newton's law of motion, one thing we can always know about a body with changing motion (such as one orbiting another body) is that the forces on it are not balanced.
But once circular motion was assumed as being the 'natural' state of affairs for heavenly bodies, and I know from my own teaching experience that students who understand Newtonian principle in the context of linear motion can still struggle to apply this to circular motion. 4
I even developed a scaffolding tool to help students make this transition, by helping them work through an example in very simple steps, but which on testing had modest effect – that is, it seemed to considerably help some students apply Newton's laws to orbital motion, but could not bridge that transition for others (Taber & Brock, 2018). I concluded even more basic step-wise support must be needed by many learners. Circular motion being linked to a net (unbalanced) centripetal force seems to be very counter-intuitive to many people.
To balance or not to balance
The suggestion that a balance of forces leads to change occurs again a little later in the book, in reference to James Hutton's geology,
"…Hutton supported his new ideas both with solid empirical evidence and an underlying theory based on a Newtonian balance of forces. He saw a pattern in the history of the rocks: gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again."
Thomson, 2005: 39
A balance of forces would not lead to rocks being "gradually worn down by erosion, washed into the seas, accumulating as sediments, raised up as new dry land, only to be eroded again". Indeed if all the relevant forces were balanced there would be no erosion, washing, sedimentation, or raising.
Erosion, washing, sedimentation, raising up ALL require an imbalance of forces, that is, a net force to bring about a change. 5
Reading on…
This is not going to stop me persevering with reading the book*, but one can begin to lose confidence in a text in situations such as these. If you know the author is wrong on some points that you already know about, how can you be confident of their accounts of other topics that you are hoping to learn about?
Still, Prof. Thomson seems to be wrong about something that the majority of people tend to get wrong, often even after having studied the topic – so, perhaps this says more about the hold of common intuitive conceptions of motion than the quality of Prof. Thomson's scholarship. Just like many physics learners – he has learnt Newton's laws, but just does not seem to find them credible.
Sources cited:
Darwin, C. (1859). The Origin of Species by Means of Natural Selection, or the preservation of favoured races in the struggle for life. John Murray.
Dawkins, R. (1988). The Blind Watchmaker. Penguin Books.
Paley, W. (1802/2006). Natural Theology: Or Evidence of the Existence and Attributes of the Deity, Collected from the Appearances of Nature(M. D. Eddy & D. Knight, Eds.). Oxford University Press.
Rosen, E. (1965/1995) Copernicus on the phases and the light of the planets, in Rosen, E. (1995). Copernicus and his successors (E. Hilfstein, Ed.). The Hambledon Press.
Thomson, K. (2005). The Watch on the Heath: Science and religion before Darwin. HarperCollins.
Watts, M. and Taber, K. S. (1996) An explanatory gestalt of essence: students' conceptions of the 'natural' in physical phenomena, International Journal of Science Education, 18 (8), pp.939-954.
Notes
1 Though not in the world-view offered by general relativity where the mass of the sun distorts space-time enough for the earth to orbit.
2 The title track from Steve Winwood's 1980 solo album 'Arc of a Diver'
3 We have known since Kepler that the planets orbit the sun following ellipses (to a first order of approximation*), not perfect circles – but this does not change the fundamental point here: moving in an ellipse involves continuous changes of velocity. (* i.e., ignoring the perturbations due to the {much smaller} forces between the orbiting bodies.**)
[Added, 20220711]: these perturbations are very small compared with the main sun-planet interactions, but they can still be significant in other ways:
"…the single most spectacular achievement in the long history of computational astronomy, namely, the discovery of the planet Neptune through the perturbations which it produced in the motion of Uranus."
Rosen, 1965/1995, p.81
4 What is judged as 'natural' is often considered by people as not needing any further explanation (Watts and Taber, 1996).
5 This reference to Hutton's ideas seems to preview a more detailed treatment of the new geology in a later chapter in the book (that I have not yet reached), so perhaps as I read on I will find a clearer explanation of what is meant by these changes being based on a theory of balance of forces.* Still, the impression given in the extract quoted is that, as with orbits, a balance of forces brings about change.
Photosynthesis illuminating a plant? (Image by OpenClipart-Vectors from Pixabay)
Analogies, metaphors and similes are used in communication to help make the unfamiliar familiar by suggesting that some novel idea or phenomena being introduced is in some ways like something the reader/listener is already familiar with. Analogies, metaphors and similes are commonly used in science teaching, and also in science writing and journalism.
An analogy maps out similarities in structure between two phenomena or concepts. This example, from a radio programme, compared the COVID pandemic with photosynthesis.
"So, what we were particularly aiming to do, was to understand the collision between a range of different political economic factors of a pre-2020 world, and how they were sort of reassembled and deployed to cope with something which was without question unprecedented.
We used this metaphor of photosynthesis because if you think about photosynthesis in relation to plants, the sun both lights things up but at the same time it feeds them and helps them to grow, and I think one of the things the pandemic has done for social scientists is to serve both as a kind of illumination of things that previously maybe critical political economists and heterodox scholars were pointing to but now became very visible to the mainstream media and to mainstream politics. But at the same time it also accentuated and deepened some of those tendencies such as our reliance on various digital platforms, certain gender dynamics of work in the household, these sort of things that became acute and undeniable and potentially politicised over the course of 20230, 2021."
Prof. Will Davies, talking on 'Thinking Allowed' 1
Will Davies, Professor in Political Economy at Goldsmiths, University of London was talking to sociologist Prof. Laurie Taylor who presents the BBC programme 'Thinking Aloud' as part of an episode called 'Covid and change'
A scientific idea used as analogue
Prof. Davies refers to using "this metaphor of photosynthesis". However he goes on to suggest how the two things he is comparing are structurally similar – the pandemic has shone a light on social issues at the same time as providing the conditions for them to become more extreme, akin to how light both illuminates plants and changes them. A metaphor is an implicit comparison where the reader/listener is left to interpret the comparison, but a metaphor or simile that is explicitly developed to explain the comparison can become an analogy.
Often science concepts are introduced by analogy to more familiar everyday ideas, objects or events. Here, however, a scientific concept, photosynthesis is used as the analogue – the source used to explain something novel. Prof. Davies assumes listeners will be familiar enough with this science concept for it to helpful in introducing his research.
Mischaracterising photosynthesis?
A science teacher might not like the notion that the sun feeds plants – indeed if a student suggested this in a science class it would likely be judged as an alternative conception. In photosynthesis, carbon dioxide (from the atmosphere) and water (usually absorbed from the soil) provide the starting materials, and the glucose that is produced (along with oxygen) enables other processes – such as growth which relies on other substances also being absorbed from the soil. (So-called 'plant foods', which would be better characterised as plant nutritional supplements, contain sources of elements such as nitrogen, phosphorus and potassium). Light is necessary for photosynthesis, but the sunlight is not best considered 'food'.
One might also argue that Prof. Davies has misidentified the source for his analogy, and perhaps he should rather have suggested sunlight as the source metaphor for his comparison as sunlight both illuminates plants and enables them to grow. Photosynthesis takes place inside chloroplasts within a plant's tissues, and does not illuminate the plant. However, Prof. Davies' expertise is in political economy, not natural science, and it was good to see a social scientist looking to use a scientific idea to explain his research.
Faster-than-light electrons race from a sitting start and are baked to give off light brighter than millions of suns that can be used to image tiny massage balls: A case of science communication
Keith S. Taber
(The pedantic science teacher)
Ockham's razor
Ockham's razor (also known as Occam's razor) is a principle that is sometimes applied as a heuristic in science, suggesting that explanations should not be unnecessarily complicated. Faced with a straightforward explanation, and an alternative convoluted explanation, then all other things being equal we should prefer the former – not simply accept it, but to treat is as the preferred hypothesis to test out first.
Ockham's Razor is also an ABC radio show offering "a soap box for all things scientific, with short talks about research, industry and policy from people with something thoughtful to say about science". The show used to offer recorded essays (akin to the format of BBC's A Point of View), but now tends to record short live talks.
I've just listened to an episode called The 'science donut' – in fact I listened several time as I thought it was fascinating – as in a few minutes there was much to attend to.
I approached the episode as someone with an interest in science, of course, but also as an educator with an ear to the ways in which we communicate science in teaching. Teachers do not simply present sequences of information about science, but engage pedagogy (i.e., strategies and techniques to support learning). Other science communicators (whether journalists, or scientists themselves directly addressing the public) use many of the same techniques. Teaching conceptual material (such as science principles, theories, models…) can be seen as making the unfamiliar familiar, and the constructivist perspective on how learning occurs suggests this is supported by showing the learner how that which is currently still unfamiliar, is in some way like something familiar, something they already have some knowledge/experience of.
Science communicators may not be trained as teachers, so may sometimes be using these techniques in a less considered or even less deliberate manner. That is, people use analogy, metaphor, simile, and so forth, as a normal part of everyday talk to such an extent that these tropes may be generated automatically, in effect, implicitly. When we are regularly talking about an area of expertise we almost do not have to think through what we are going to say. 1
Science communicators also often have much less information about their audience than teachers: a radio programme/podcast, for example, can be accessed by people of a wide range of background knowledge and levels of formal qualifications.
One thing teachers often learn to do very early in their careers is to slow down the rate of introducing new information, and focus instead on a limited number of key points they most want to get across. Sometimes science in the media is very dense in the frequency of information presented or the background knowledge being drawn upon. (See, for example, 'Genes on steroids? The high density of science communication'.)
A beamline scientist
Dr Emily Finch, who gave this particular radio talk, is a beamline scientist at the Australian Synchrotron. Her talk began by recalling how her family visited the Synchrotron facility on an open day, and how she later went on to work there.
She then gave an outline of the functioning of the synchrotron and some examples of its applications. Along the way there were analogies, metaphors, anthropomorphism, and dubiously fast electrons.
The creation of the god particle
To introduce the work of the particle accelerator, Dr Finch reminded her audience of the research to detect the Higgs boson.
"Do you remember about 10 years ago scientists were trying to make the Higgs boson particle? I see some nods. They sometimes call it the God particle and they had a theory it existed, but they had not been able to prove it yet. So, they decided to smash together two beams of protons to try to make it using the CERN large hadron collider in Switzerland…You might remember that they did make a Higgs boson particle".
This is a very brief summary of a major research project that involved hundreds of scientists and engineers from a great many countries working over years. But this abbreviation is understandable as this was not Dr Finch's focus, but rather an attempt to link her actual focus, the Australian Synchrotron, to something most people will already know something about.
However, aspects of this summary account may have potential to encourage the development of, or reinforce an existing, common alternative conception shared by many learners. This is regarding the status of theories.
In science, theories are 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world', yet students often understand theories to be nothing more than just ideas, hunches, guesses – conjectures at best (Taber, Billingsley, Riga & Newdick, 2015). In a very naive take on the nature of science, a scientist comes up with an idea ('theory') which is tested, and is either 'proved' or rejected.
This simplistic take is wrong in two regards – something does not become an established scientific theory until it is supported by a good deal of evidence; and scientific ideas are not simply proved or disproved by testing, but rather become better supported or less credible in the light of the interpretation of data. Strictly scientific ideas are never finally proved to become certain knowledge, but rather remain as theories. 2
In everyday discourse, people will say 'I have a theory' to mean no more that 'I have a suggestion'.
A pedantic scientist or science teacher might be temped to respond:
"no you don't, not yet,"
This is sometimes not the impression given by media accounts – presumably because headlines such as 'research leads to scientist becoming slightly more confident in theory' do not have the same impact as 'cure found', 'discovery made, or 'theory proved'.
The message that could be taken away here is that scientists had the idea that Higgs boson existed, but they had not been able to prove it till they were able to make one. But the CERN scientists did not have a Higgs boson to show the press, only the data from highly engineered detectors, analysed through highly complex modelling. Yet that analysis suggested they had recorded signals that closely matched what they expected to see when a short lived Higgs decayed allowing them to conclude that it was very likely one had been formed in the experiment. The theory motivating their experiment was strongly supported – but not 'proved' in an absolute sense.
The doughnut
Dr Finch explained that
"we do have one of these particle accelerators here in Australia, and it's called the Australian Synchrotron, or as it is affectionately known the science donut
…our synchrotron is a little different from the large hadron collider in a couple of main ways. So, first, we just have the one beam instead of two. And second, our beam is made of electrons instead of protons. You remember electrons, right, they are those tiny little negatively charged particles and they sit in the shells around the atom, the centre of the atom."
Dr Emily Finch talking on Ockham's Razor
One expects that members of the audience would be able to respond to this description and (due to previous exposure to such representations) picture images of atoms with electrons in shells. 'Shells' is of course a kind of metaphor here, even if one which with continual use has become a so-called 'dead metaphor'. Metaphor is a common technique used by teachers and other communicators to help make the unfamiliar familiar. In some simplistic models of atomic structure, electrons are considered to be arranged in shells (the K shell, the L shell, etc.), and a simple notation for electronic configuration based on these shells is still often used (e.g., Na as 2.8.1).
However, this common way of talking about shells has the potential to mislead learners. Students can, and sometimes do, develop the alternative conception that atoms have actual physical shells of some kind, into which the electrons are located. The shells scientists refer to are abstractions, but may be misinterpreted as material entities, as actual shells. The use of anthropomorphic language, that is that the electrons "sit in the shells", whilst helping to make the abstract ideas familiar and so perhaps comfortable, can reinforce this. After all, it is difficult to sit in empty space without support.
The subatomic grand prix?
Dr Finch offers her audience an analogy for the synchrotron: the electrons "are zipping around. I like to think of it kind of like a racetrack." Analogy is another common technique used by teachers and other communicators to help make the unfamiliar familiar.
Dr Finch refers to the popularity of the Australian Formula 1 (F1) Grand Prix that takes place in Melbourne, and points out
"Now what these race enthusiasts don't know is that just a bit further out of the city we have a race track that is operating six days a week that is arguably far more impressive.
That's right, it is the science donut. The difference is that instead of having F1s doing about 300 km an hour, we have electrons zipping around at the speed of light. That's about 300 thousand km per second.
Dr Emily Finch talking on Ockham's Razor
There is an interesting slippage – perhaps a deliberate rhetoric flourish – from the synchrotron being "kind of like a racetrack" (a simile) to being "a race track" (a metaphor). Although racing electrons lacks a key attraction of an F1 race (different drivers of various nationalities driving different cars built by competing teams presented in different livery – whereas who cares which of myriad indistinguishable electrons would win a race?) that does not undermine the impact of the mental imagery encouraged by this analogy.
This can be understood as an analogy rather than just a simile or metaphor as Dr Finch maps out the comparison:
target concept
analogue
a synchotron
a racetrack
operates six days a week
[Many in the audience would have known that the Melbourne Grand Prix takes place on a 'street circuit' that is only set up for racing one weekend each year.]
racing electrons
racing 'F1s' (i.e., Grand Prix cars)
at the speed of light
at about 300 km an hour
An analogy between the Australian Synchrotron and the Melbourne Grand Prix circuit
So, here is an attempt to show how science has something just like the popular race track, but perhaps even more impressive – generating speeds orders of magnitude greater than even Lewis Hamilton could drive.
They seem to like their F1 comparisons at the Australian Synchrotron. I found another ABC programme ('The Science Show') where Nobel Laureate "Brian Schmidt explains, the synchrotron is not being used to its best capability",
"the analogy here is that we invested in a $200 million Ferrari and decided that we wouldn't take it out of first gear and do anything other than drive it around the block. So it seems a little bit of a waste"
Brian Schmidt (Professor of Astronomy, and Vice Chancellor, at Australian National University)
A Ferrari being taken for a spin around the block in Melbourne (Image by Lee Chandler from Pixabay )
How fast?
But did Dr Finch suggest there that the electrons were travelling at the speed of light? Surely not? Was that a slip of the tongue?
"So, we bake our electrons fresh in-house using an electron gun. So, this works like an old cathode ray tube that we used to have in old TVs. So, we have this bit of tungsten metal and we heat it up and when it gets red hot it shoots out electrons into a vacuum. We then speed up the electrons, and once they leave the electron gun they are already travelling at about half the speed of light. We then speed them up even more, and after twelve metres, they are already going at the speed of light….
And it is at this speed that we shoot them off into a big ring called the booster ring, where we boost their energy. Once their energy is high enough we shoot them out again into another outer ring called the storage ring."
Dr Emily Finch talking on Ockham's Razor
So, no, the claim is that the electrons are accelerated to the speed of light within twelve metres, and then have their energy boosted even more.
But this is contrary to current physics. According to the currently accepted theories, and specifically the special theory of relativity, only entities which have zero rest mass, such as photons, can move at the speed of light.
Electrons have a tiny mass by everyday standards (about 0.000 000 000 000 000 000 000 000 001 g), but they are still 'massive' particles (i.e., particles with mass) and it would take infinite energy to accelerate a single tiny electron to the speed of light. So, given our current best understanding, this claim cannot be right.
I looked to see what was reported on the website of the synchrotron itself.
The electron beam travels just under the speed of light – about 299,792 kilometres a second.
Strictly the electrons do not travel at the speed of light but very nearly the speed of light.
The speed of light in a vacuum is believed to be 299 792 458 ms-1 (to the nearest metre per second), but often in science we are working to limited precision, so this may be rounded to 2.998 ms-1 for many purposes. Indeed, sometimes 3 x 108 ms-1 is good enough for so-called 'back of the envelope' calculations. So, in a sense, Dr Finch was making a similar approximation.
But this is one approximation that a science teacher might want to avoid, as electrons travelling at the speed of light may be approximately correct, but is also thought to be physically impossible. That is, although the difference in magnitude between
(i) the maximum electron speeds achieved in the synchrotron, and
(ii) the speed of light,
might be a tiny proportional difference – conceptually the distinction is massive in terms of modern physics. (I imagine Dr Finch is aware of all this, but perhaps her background in geology does not make this seem as important as it might appear to a physics teacher.)
Dr Finch does not explicitly say that the electrons ever go faster than the speed of light (unlike the defence lawyer in a murder trial who claimed nervous impulses travel faster than the speed of light) but I wonder how typical school age learners would interpret "they are already going at the speed of light….And it is at this speed that we shoot them off into a big ring called the booster ring, where we boost their energy". I assume that refers to maintaining their high speeds to compensate for energy transfers from the beam: but only because I think Dr Finch cannot mean accelerating them beyond the speed of light. 3
The big doughnut
After the reference to how "we bake our electrons fresh in-house", Dr Finch explains
And so it is these two rings, these inner and outer rings, that give the synchrotron its nick name, the science donut. Just like two rings of delicious baked electron goodness…
So, just to give you an idea of scale here, this outer ring, the storage ring, is about forty one metres across, so it's a big donut."
So, there is something of an extended metaphor here. The doughnut is so-called because of its shape, but this doughnut (a bakery product) is used to 'bake' electrons.
If audience members were to actively reflect on and seek to analyse this metaphor then they might notice an incongruity, perhaps a mixed metaphor, as the synchrotron seems to shift from being that which is baked (a doughnut) to that doing the baking (baking the electrons). Perhaps the electrons are the dough, but, if so, they need to go into the oven.
But, of course, humans implicitly process language in real time, and poetic language tends to be understood intuitively without needing reflection. So, a trope such as this may 'work' to get across the flavour (sorry) of an idea, even if under close analysis (by our pedantic science teacher again) the metaphor appears only half-baked.
Perverting the electrons
Dr Finch continued
"Now the electrons like to travel in straight lines, so to get them to go round the rings we have to bend them using magnets. So, we defect the electrons around the corners [sic] using electromagnetic fields from the magnets, and once we do this the electrons give off a light, called synchrotron light…
Dr Emily Finch talking on Ockham's Razor
Now electrons are not sentient and do not have preferences in the way that someone might prefer to go on a family trip to the local synchrotron rather than a Formula 1 race. Electrons do not like to go in straight lines. They fit with Newton's first law – the law of inertia. An electron that is moving ('travelling') will move ('travel') in a straight line unless there is net force to pervert it. 4
If we describe this as electrons 'liking' to travel in straight lines it would be just as true to say electrons 'like' to travel at a constant speed. Language that assigns human feelings and motives and thoughts to inanimate objects is described as anthropomorphic. Anthropomorphism is a common way of making the unfamiliar familiar, and it is often used in relation to molecules, electrons, atoms and so forth. Sadly, when learners pick up this kind of language, they do not always appreciate that it is just meant metaphorically!
"This synchrotron light is brighter than a million suns, and we capture it using special equipment that comes off that storage ring.
And this equipment will focus and tune and shape that beam of synchrotron light so we can shoot it at samples like a LASER."
Dr Emily Finch talking on Ockham's Razor
Whether the radiation is 'captured' is a moot point, as it no longer exists once it has been detected. But what caught my attention here was the claim that the synchrotron radiation was brighter than a million suns. Not because I necessarily thought this bold claim was 'wrong', but rather I did not understand what it meant.
The statement seems sensible at first hearing, and clearly it means qualitatively that the radiation is very intense. But what did the quantitative comparison actually mean? I turned again to the synchrotron webpage. I did not find an answer there, but on the site of a UK accelerator I found
"These fast-moving electrons produce very bright light, called synchrotron light. This very intense light, predominantly in the X-ray region, is millions of times brighter than light produced from conventional sources and 10 billion times brighter than the sun."
Sunlight spreads out and its intensity drops according to an inverse square law. Move twice as far away from a sun, and the radiation intensity drops to a quarter of what it was when you were closer. Move to ten times as far away from the sun than before, and the intensity is 1% of what it was up close.
The synchrotron 'light' is being shaped into a beam "like a LASER". A LASER produces a highly collimated beam – that is, the light does not (significantly) spread out. This is why football hooligans choose LASER pointers rather than conventional torches to intimidate players from a safe distance in the crowd.
Comparing light with like
This is why I do not understand how the comparison works, as the brightness of a sun depends how close you are too it – a point previously discussed here in relation to NASA's Parker solar probe (NASA puts its hand in the oven). If I look out at the night sky on a clear moonlight night then surely I am exposed to light from more "than a million suns" but most of them are so far away I cannot even make them out. Indeed there are faint 'nebulae' I can hardly perceive that are actually galaxies shining with the brightness of billions of suns. 5 If that is the comparison, then I am not especially impressed by something being "brighter than a million suns".
How bright is the sun? it depends which planet you are observing from. (Images by AD_Images and Gerd Altmann from Pixabay)
We are told not to look directly at the sun as it can damage our eyes. But a hypothetical resident of Neptune or Uranus could presumably safely stare at the sun (just as we can safely stare at much brighter stars than our sun because they are so far away). So we need to ask :"brighter than a million suns", as observed from how far away?
How bright is the sun? That depends on viewing conditions (Image by UteHeineSch from Pixabay)
Even if referring to our Sun as seen from the earth, the brightness varies according to its apparent altitude in the sky. So, "brighter than a million suns" needs to be specified further – as perhaps "more than a million times brighter than the sun as seen at midday from the equator on a cloudless day"? Of course, again, only the pedantic science teacher is thinking about this: everyone knows well enough what being brighter than a million suns implies. It is pretty intense radiation.
Applying the technology
Dr Finch went on to discuss a couple of applications of the synchrotron. One related to identifying pigments in art masterpieces. The other was quite timely in that it related to investigating the infectious agent in COVID.
"Now by now you have probably seen an image of the COVID virus – it looks like a ball with some spikes on it. Actually it kind of looks like those massage balls that your physio makes you buy when you turn thirty and need to to ease all your physical ailments that you suddenly have."
Dr Emily Finch talking on Ockham's Razor
Coronavirus particles and massage balls…or is it… (Images by Ulrike Leone and Daniel Roberts from Pixabay)
Again there is an attempt to make the unfamiliar familiar. These microscopic virus particles are a bit like something familiar from everyday life. Such comparisons are useful where the everyday object is already familiar.
By now I've seen plenty of images of the coronavirus responsible for COVID, although I do not have a physiotherapist (perhaps this is a cultural difference – Australians being so sporty?) So, I found myself using this comparison in reverse – imagining that the "massage balls that your physio makes you buy" must be like larger versions of coronavirus particles. Having looked up what these massage balls (a.k.a. hedgehog balls it seems) look like, I can appreciate the similarity. Whether the manufacturers of massage balls will appreciate their products being compared to enormous coronavirus particles is, perhaps, another matter.
Work cited:
Taber, K. S., Billingsley, B., Riga, F., & Newdick, H. (2015). English secondary students' thinking about the status of scientific theories: consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world – or just 'an idea someone has'. The Curriculum Journal, 1-34. doi: 10.1080/09585176.2015.1043926
Notes:
1 At least, depending how we understand 'thinking'. Clearly there are cognitive processes at work even when we continue a conversation 'on auto pilot' (to employ a metaphor) whilst consciously focusing on something else. Only a tiny amount of our cognitive processing (thinking?) occurs within conscousness where we reflect and deliberate (i.e., explicit thinking?) We might label the rest as 'implicit thinking', but this processing varies greatly in its closeness to deliberation – and some aspects (for example, word recognition when listening to speech; identifying the face of someone we see) might seem to not deserve the label 'thinking'?
2 Of course the evidence for some ideas becomes so overwhelming that in principle we treat some theories as certain knowledge, but in principle they remain provisional knowledge. And the history of science tells us that sometimes even the most well-established ideas (e.g., Newtonian physics as an absolutely precise description of dynamics; mass and energy as distinct and discrete) may need revision in time.
3 Since I began drafting this article, the webpage for the podcast has been updated with a correction: "in this talk Dr Finch says electrons in the synchrotron are accelerated to the speed of light. They actually go just under that speed – 99.99998% of it to be exact."
4 Perversion in the sense of the distortion of an original course
5 The term nebulae is today reserved for clouds of dust and gas seen in the night sky in different parts of our galaxy. Nebulae are less distinct than stars. Many of what were originally identified as nebulae are now considered to be other galaxies immense distances away from our own.
One of the supposed features of scientific knowledge is that it is always, strictly speaking, provisional. Science seeks generalisable, theoretical knowledge – and no matter how strong the case for some general claim may seem, a scientist is supposed to be open-minded, and always willing to consider that their opinion might be changed by new evidence or a new way of looking at things.
Perhaps the strongest illustration of this is Newtonian physics that seemed to work so well for so many decades that for many it seemed unquestionable. Yet we now know that it is not a precise account that always fits nature. (And by 'we know' I mean we know in the sense of having scientific knowledge – we think this, and have very strong grounds to think this, but reserve the right to change our minds in the light of new information!)
When science is presented in the media, this provisional nature of scientific knowledge – with its inbuilt caveat of uncertainty – is often ignored. News reports, and sometimes scientists when being interviewed by journalists, often imply that we now know…for certain… Science documentaries are commonly stitched together with the trope 'and this can only mean' (Taber, 2007) when any scientist worth their salt could offer (even if seemingly less feasible) alternative scenarios that fit the data.
One might understand this as people charged with communicating science to a general audience seeking to make things as simple and straightforward as possible. However it does reinforce the alternative conception that in science theories are tested allowing them to be straightforwardly dismissed or proved for all time. What is less easy to understand is why scientists seeking to publish work in academic journals to be read by other scientists would claim to know anything for certain – as that is surely likely to seem arrogant and unscientific to editors, reviewers, and those who might read their published work
Science that is indisputable
So, one of two things that immediately made me lack confidence in a published paper about the origin of SARS-CoV-2, the infectious agent considered responsible for the COVID pandemic (Sehgal, 2021), was that the first word was 'Undisputedly'. Assuming the author was not going to follow up with Descartes' famous 'Cogito' ("Undisputedly… I think, therefore I am"), this seemed to be a clear example of something I always advised my own research students to avoid in their writing – a hostage to fortune.
A bold first sentence for this article in a supposedly peer-reviewed research journal
The good scientist learns to use phrases like "this seems to suggest…" rather than "I have therefore proved beyond all possible doubt…"!
Prestigious research journals are selective in what they publish – and reject most submissions, or at least require major revisions based on reviewer evaluations. Predatory journals seek to maximise their income from charging authors for publication; and so do not have the concern for quality that traditionally characterised academic publishing. If some of the published output I have seen is a guide, some of these journals would publish virtually anything submitted regardless of quality.
Genetic relatedness of bats and viruses
Now it would be very unfair to dismiss a scientific article based purely on the first word of the abstract. Even if 'undisputedly' is a word that does not sit easily in scientific discourse, I have to acknowledge that writing a scientific paper is in part a rhetorical activity, and authors may sometimes struggle to balance the need to adopt scientific values (such as always being open to the possibility of another interpretation) with the construction of a convincing argument.
"Undisputedly, the horseshoe bats are the nearest known genetic relatives of the Sars-CoV-2 virus."
Sehgal, 2021, p.29 341
Always start a piece of writing with a strong statement
Closest genetic relatives?
Okay, I was done.
I am not a biologist, and so perhaps I am just very ignorant on the topic, but this seemed an incredible claim. Our current understanding of the earth biota is that there has (probably) been descent from a common ancestor of all living things on the planet today. So, just as I am related, even if often only very distantly, to every other cospecific specimen of Homo sapiens on the planet, I am also related by descent from common ancestors (even more distantly) to every chimpanzee, indeed every primate, every mammal, every chordate; indeed every animal; plus all the plants, fungi, protists and monera.
But clearly I share a common ancestor with all humans in the 'brotherhood of man' more recently than all other primates, and that more recently than all other mammals. And when we get to the non-animal kingdoms we are not even kissing cousins.
And viruses – with their RNA based genetics? These are often not even considered to be living entities in their own right.
There is certainly a theory that there was an 'RNA world', a time when some kind of primitive life based on RNA genes existed from which DNA and lifeforms with DNA genomes later evolved, so one can stretch the argument to say I am related to viruses – that if one went back far enough, both viruses and humans (or viruses and horseshoe bats, more to the point of the claim in this article) around today could be considered to be derived from a common ancestor, and that this is reflected in patterns that can be found in their genomes today.
The nearest genetic relative to SARS-CoV-2 virus?
The genome of a virus is not going to be especially similar to the genome of a mammal. The SARS-CoV-2 virus is a single stranded RNA virus which will be much more genetically similar to other such viruses that to organisms with double stranded DNA. It is famously a coronavirus – so surely it is most likely to be strongly related to other coronaviruses? It is called 'SARS-CoV-2' because of its similarity to the virus that causes SARS (severe acute respiratory syndrome): SARS-CoV. These seems strong clues.
And the nearest genetic relative to horseshoe bats are…
And bats are mammals. The nearest relatives to any specific horseshoe bat are other bats of that species. And if we focus at the species level, and ask what other species would comprise the nearest genetic relatives to a species of horseshoe bats? I am not an expert, but I would have guessed other species of horseshoe bat (there are over a hundred such species). Beyond that family – well I imagine other species of bat. Looking on the web, it seems that Old World leaf-nosed bats (and not viruses) have been mooted from genetic studies (Amador, Moyers Arévalo, Almeida, Catalano & Giannini, 2018) as the nearest genetic relatives of the horsehoe bats.
Annotated copy of Figure 7 from Amador et al., 2018
So, although I am not an expert, and I am prepared to be corrected by someone who is, I am pretty sure the nearest relative that is not a bat would be another mammal – not a bird, not a fish, certainly not a mollusc or insect. Mushrooms and ferns are right out of contention. And, no, not a virus. 1
Judge me on what I mean to say – not what I say
Perhaps I am being picky here. A little reflection suggests that surely Sehgal (in stating that "the horseshoe bats are the nearest known genetic relatives of the Sars-CoV-2 virus") did not actually mean to imply that "the horseshoe bats are the nearest known genetic relatives of the Sars-CoV-2 virus", but rather perhaps something along the lines that an RNA virus known to infect horseshoe bats was the nearest known genetic relative of the Sars-CoV-2 virus.
Perhaps I should have read "the horseshoe bats are the nearest known genetic relatives of the Sars-CoV-2 virus" as "the horseshoe bats are hosts to the nearest known genetic relatives of the Sars-CoV-2 virus"? If I had read on, I would have found reference to a "bat virus RaTG13 having a genome resembling the extent of 98.7% to that of the Sars-CoV-2 virus" (p.29 341).
Yet if a research paper, that has supposedly been subject to rigorous peer review, manages to both misrepresent the nature of science AND make an obviously factually incorrect claim in its very first sentence, then I think I can be forgiven for suspecting it may not be the most trustworthy source of information.
Work cited
Amador, L. I., Moyers Arévalo, R. L., Almeida, F. C., Catalano, S. A., & Giannini, N. P. (2018). Bat Systematics in the Light of Unconstrained Analyses of a Comprehensive Molecular Supermatrix. Journal of Mammalian Evolution, 25(1), 37-70. https://doi.org/10.1007/s10914-016-9363-8
Sehgal, M.L. (2021) Origin of SARS-CoV-2: Two Schools of Thought, Biomedical Journal of Scientific & Technical Research, July, 2020, Volume 37, 2, pp 29341-29356
1 It is perfectly possible logically for organism Y (say a horseshoe bat) to be the closest genetic relative of organism X (say a coronavirus) without organism X being the closest genetic relative of organism Y. (By analogy, someone's closest living genetic relative could be a grandchild whose closest genetic relative is their own child or their parent that was not a child of that grandparent.) However, the point here is that bat is not even quite closely related to the virus.
Can we be certain about something that happened half a million years ago?
Keith S. Taber
What was going on in Java when Homo erectus lived there? (Image by Kanenori from Pixabay )
About half a million years ago a hominid, of the Homo erectus species, living in Java took a shell and deliberately engraved a mark on it. Now, I was not there when this happened, so my testimony is second hand, but I can be confident about this as I was told by a scientist that she was sure that this definitely happened.
"…we knew for sure that it must have been made by Homo erectus"
But how can we be so sure about something alleged to have occurred so long ago?
"A long time ago [if not] in a galaxy far, far away…." the skull of a specimen of Homo erectus (Image by Mohamed Noor from Pixabay ) [Was this an inspiration for the Star Wars stormtrooper helmet?]
I doubt Fifi would be convinced.1 Fifi was a Y12 student (c.16 years old) interviewed as part of the LASAR project who had reservations about palaeontology as it did not provide certain scientific knowledge,
"I like fossils though, I think they're interesting but I don't think I'd really like [working as a palaeontologist]…I don't think you could ever really know unless you were there… There'll always be an element of uncertainty because no matter how much evidence you supply there will always be, like, doubt because of the fact that you were never there…there'll always be uncertainty."
Learners can have alternative conceptions of the nature of science, just as much as they often do for forces or chemical bonding or plant nutrition. They often think that scientific knowledge has been 'proved', and so is certain (e.g., Taber, Billingsley, Riga & Newdick, 2015). An area like palaeontology where direct observation is not possible may therefore seem to fall short of offering genuine scientific knowledge.
The uncertain nature of scientific knowledge
One key feature of the nature of science is that it seeks to produce general or theoretical knowledge of the natural world. That is, science is not just concerned with providing factual reports about specific events but with developing general accounts that can explain and apply to broad categories of objects and events. Such general and theoretical knowledge is clearly more useful than a catalogue of specific facts – which can never tell us about the next occasion or what might happen in hypothetical situations.
However, a cost of seeking such applicable and useful knowledge is that it can never be certain. It relies on our ways of classifying objects and events, the evidence we have collected so far, our ability to spot the most important patterns -and the deductions this might support. So, scientific knowledge is always provisional in the sense that it is open to revision in response to new data, or new ways of thinking about existing data as evidence.
Yet often reports of science in the media give the impression that science has made absolute discoveries. Some years ago I wrote about the tendency in science documentaries for the narrative to be driven by links that claimed "...this could only mean…" when we know that in science the available data always underdetermines theory (Taber, 2007). Or, to put it another way, we could always think up other ways of explaining the data. Sometimes these alternatives might seem convoluted and unlikely, but if we can suggest a possible (even when unconvincing) alternative, then the available data can never "only mean" any one particular proposed interpretation.
The scientist concerned was J.C.A (José) Joordens who is Professor in Hominin Paleoecology and Evolution, at Maastricht University. Prof. Joordens holds the Naturalis Dubois Chair in Hominin Paleoecology and Evolution. The reference to Dubois relates to the naturist responsible for finding a so-called 'missing link' in the chain of descent to modern humans,
"One of the most exciting episodes of palaeoanthropology was the find of the first transitional form, the Pithecanthropus erectus, by the Dutchman Eugène Dubois in Java during 1891-1892. …Besides the human remains, Dubois made a large collection of vertebrate fossils, mostly of mammals, now united in the so-called Dubois Collection."
de Vos, 2004
The Java man species, Pithecanthropus erectus (an upright ape/mokey-man), was later renamed as Homo erectus, the upright man.
On an edition of BBC Radio 4's 'In Our Time' taking 'Homo erectus' as its theme, Prof. Joordens explained how some fossil shells collected by Dubois as part of the context of the hominid fossils had remained in storage for over a century ("The shells had been, well, shelved…"!), before a graduate student set out to photograph them all for a thesis project. This led to the discovery that one of the shells appeared to have been engraved.
This could only mean one thing…
This is what Prof. Joordens told the host, Melvyn Bragg,
"One shell that had a very strange marking that we could not understand how it ended up there…
It was geometric, like a W, and this is of course something that animals don't produce. We had to conclude that it must have been made by Homo erectus. And it must have been a very deliberate marking because of, we did experimental research trying to replicate it, and then we actually found it was quite hard to do. Because, especially fresh shells, they have a kind of organic exterior, and it's hard to push some sharp objects through and make those lines, so that was when we knew for sure that it must have been made by Homo erectus."
Prof. José Joordens talking on 'In Our Time'
We may consider this claim to be composed of a number of components, such as:
There is a shell with some 'very strange' markings
The shell was collected in Java in the nineteenth century
The shell had the markings when first collected
The markings were not caused by some natural phenomenon
The markings were deliberate not accidental
The markings were made by a specimen of Homo erectus
A sceptic might ask such questions as
How can we be sure this shell was part of the original collection? Could it have been substituted by mistake or deliberately?
How do we know the marks were not made more recently? perhaps by someone in the field in Java, or during transit form Java to the Netherlands, or by someone inspecting the collection?
Given that even unusual markings will occur by chance occasionally, how can we be certain these markings were deliberate? Does the mark really look like a 'W 'or might that be an over-interpretation. 2
And so forth.
It is worth bearing in mind that no one noticed these markings in the field, or when the collection was taken back to the Netherlands – indeed Prof. Joordens noted she had carried the shell around in her backpack (could that have been with an open penknife?) unaware of the markings
Of course, Prof. Joordens may have convincing responses to many of these questions – but a popular radio show is not the place to detail all the argument and evidence. Indeed, I found a report in the top journal Nature ('Homo erectus at Trinil on Java used shells for tool production and engraving') by Prof. Joordens and her team 3, claiming,
"One of the Pseudodon shells, specimen DUB1006-fL, displays a geometric pattern of grooves on the central part of the left valve [*]. The pattern consists, from posterior to anterior, of a zigzag line with three sharp turns producing an 'M' shape, a set of more superficial parallel lines, and a zigzag with two turns producing a mirrored 'N' shape. Our study of the morphology of the zigzags, internal morphology of the grooves, and differential roughness of the surrounding shell area demonstrates that the grooves were deliberately engraved and pre-date shell burial and weathering"
It may seem most likely that the markings were made by a Homo erectus, as no other explanation so far considered fits all the data, but theory is always under-determined – one can never be certain another scenario might be found which also fits the known facts.
Strictly, Prof. Joordens' contradicts herself. She claims the marks are "something that animals don't produce" and then claims an animal is responsible. She presumably meant that no non-hominid animal makes such marks. Even if we accept that (and, as they say, absence of evidence is not evidence of absence 4), can we be absolutely certain some other hominid might not have been present in Java at the time, marking the odd shell? As the 'In Our Time' episode discussed, Homo erectus often co-existed with other hominids.
Probably not, but … can we confidently say absolutely, definitely, not?
As Fifi might say: "I don't think you could ever really know unless you were there".
My point is not that I think Prof. Joordens is wrong (she is an expert, so I think she is likely correct), but just that her group cannot be absolutely certain. When Prof. Joordens says she knows for sure I assume (because she is a scientist, and I am a scientist) that this means something like "based on all the evidence currently available, our best, and only convincing, interpretation is…" Unfortunately lay people often do not have the background to insert such provisos themselves, and so often hear such claims literally – science has proved its case, so we know for sure. Where listeners already think scientific knowledge is certain, this misconception gets reinforced.
Meanwhile, Prof. Joordens continues her study of hominids in Java in the Studying Homo erectus Lifestyle and Location project (yes, the acronym is SHeLL).
Joordens, J., d'Errico, F., Wesselingh, F. et al. Homo erectus at Trinil on Java used shells for tool production and engraving. Nature 518, 228-231 (2015). https://doi.org/10.1038/nature13962
Taber, K. S., Billingsley, B., Riga, F., & Newdick, H. (2015). English secondary students' thinking about the status of scientific theories: consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world – or just 'an idea someone has'. The Curriculum Journal, 1-34. doi: 10.1080/09585176.2015.1043926
Notes
1 As is usual practice in such research, Fifi is an assumed name. Fifi gave permission for data she contributed to the research to be used in publications on the assumption it would be associated with a pseudonym. (See: 'Using pseudonyms in reporting research'.)
2 No one is suggesting that the hominid deliberately marked the shell with a letter of the Roman alphabet, just that s/he deliberately made a mark that represented a definite and deliberate pattern. Yet human beings tend to spot patterns in random data. Could it just be some marks that seem to fit into a single pattern?
3 Josephine C. A. Joordens, Francesco d'Errico, Frank P. Wesselingh, Stephen Munro, John de Vos, Jakob Wallinga, Christina Ankjærgaard, Tony Reimann, Jan R. Wijbrans, Klaudia F. Kuiper, Herman J. Mücher, Hélène Coqueugniot, Vincent Prié, Ineke Joosten, Bertil van Os, Anne S. Schulp, Michel Panuel, Victoria van der Haas, Wim Lustenhouwer, John J. G. Reijmer & Wil Roebroeks.
4 At one time there was no evidence of 'noble' gases reacting. At one time there was no evidence of ozone depletion. At one time there was no evidence of superconductivity. At one time there was no evidence that the blood circulates around the body. At one time there was no evidence of any other planet having moons. At one time there was no evidence of protons being composed of even more fundamental particles. At one time there was no evidence of black holes. At one time there was no evidence that smoking tobacco was harmful. At one time there was no evidence of … [fill in your choice scientific discovery!]
