Category: learner thinking

Poincaré, inertia, and a common misconception

A historical, and ongoing, alternative conception

Keith S. Taber

"…and eleventhly Madame Curie…" Henri Poincaré enjoying small talk at a physics conference (image source: 'Marie Curie and Poincaré talk at the 1911 Solvay Conference', Wikipedia)

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 But has any one ever experimented on bodies withdrawn from the action of every force?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, we the 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.

Read about common alternative conceptions related to Newton's first law

Read about common alternative conceptions related to Newton's second law

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 trajectory can 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:
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!

Quasi-experiment or crazy experiment?

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.

Read about the predict-observe-explain approach

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.

Read about constructivist pedagogy

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'.

Read about experimental research

Put very simply, the approach might be:

  • 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.

Read about populations of interest in research

Read about sampling a population

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."

Taber, 2019a, p.72

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)

See 'Testing for initial equivalence'

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 responsesIncorrect responses
School A (49 students)(0.27 ➾) 1336
School B (44 students)(0.41 ➾) 1826
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

Independent
variable		Teaching approach:
– predict-observe-explain (experimental)
– lectures (comparison condition)
Dependent
variable		Learning gains
Controlled
variable(s)		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.

Read about confounding variables in research

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.

Read about expectancy effects in research

So, we might revise the table above:

Independent
variable		Teaching approach:
– predict-observe-explain (experimental)
– lectures (comparison condition)
Dependent
variable		Learning gains
Potentially conflating
variables		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."

Julius Citron

The comparison condition

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."

Taber, 2019a, p.93

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."

Taber, 2019a, p.94

Validity of measurements

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 reportednot reported
pre-test:
comparison group		not reportednot 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 reportednot reported
post-test:
comparison group		not reportednot reported
post-test:
total		not reportednot 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:

Applying the 'Critical Reading of Empirical Studies Tool' to 'The effect of predict-observe-explain strategy on learners' misconceptions about dissolved salts'

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:
Note

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 publishing as long as the authors did an experiment.

Just two things

[Science] fiction reflecting life

Keith S. Taber

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.}

POEsing assessment questions…

…but not fattening the cow

Keith S. Taber

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).

Read about Predict-Observe-Explain

The article on the publisher website

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.

Read about constructivism

Read about constructivist pedagogy

Assessment: summative, formative and diagnostic

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)

A book that describes and discusses a good many alternative conceptions – but by no means all!

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.

Read about diagnostic assessment

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.

Read about the Predict-Observe-Explain technique

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).

Read about teaching about scientific explanations

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.

Read about dialogic teaching and learning

…and as a diagnostic activity

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

GroupPredictionReasons
❀correctcorrect
❁correctpartially correct
✯correctwrong
✿wrongcorrect
❂wrongpartially correct
✤wrongwrong
"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).

Read about paradigms in educational research

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.

Read about case study methodology

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

Plus ça change – balancing forces is hard work

Confusing steady states and equilibrium?

Keith S. Taber

"…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?)

Read 'Even Oxbridge professors have misconceptions'

'The Watch on the Heath'

by Prof. Keith Thomson

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:

  1. 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
  2. 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.

Read about personification in science

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).

Read about learning difficulties and Newton's third law

Thomson's 'Newtonian Physics'

In the previous posting I noted that Prof. Thomson had written

  • "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 Pixabay
Image by Clker-Free-Vector-Images from Pixabay
Original 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,

  1. salt is dissolving
  2. salt is precipitating
  3. gases from the air are dissolving in the solution
  4. gases are leaving the solution
  5. water is evaporating into the air
  6. 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 place to 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.

3 For a brief discussion regarding energy changes during processes of this kind, see 'How much damage can eight neutrons do?'

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).

Even Oxbridge professors have misconceptions

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.

Read about analogies in science

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?)

Read 'Intergenerational couplings in the family. A thought experiment about ancestry'

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.

Read about science and religion

Quantum quibbling

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 not show 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.

"Arc of a diver – effortlessly"

© Pelle Cass. This image is used with kind permission of the artist.

(This amazing artwork is by the photographer Pelle Cass. This is one of a series ('Crowded Fields') that can be viewed at https://pellecass.com/crowded-fields.)

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.

Read about alternative conceptions

Misunderstanding force and motion

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!

Read about learning difficulties and Newton's third law

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

Two conceptions of orbital motion (one canonical, the other a misconception commonly offered by students). From Taber, K. S., & Brock, R. (2018). A study to explore the potential of designing teaching activities to scaffold learning: understanding circular motion.

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.
  • Taber, K. S., & Brock, R. (2018). A study to explore the potential of designing teaching activities to scaffold learning: understanding circular motion. In M. Abend (Ed.), Effective Teaching and Learning: Perspectives, strategies and implementation (pp. 45-85). New York: Nova Science Publishers. [Read the author's manuscript version]
  • 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.

* Addendum: I have now read on, see: 'Plus ça change – balancing forces is hard work'

Counting both the bright and the very dim

What is 1% of a very large, unknown, number?

Keith S. Taber

1, skip 99; 2, skip 99; 3, skip 99; 4,… skip 99, 1 000 000 000!
(Image by FelixMittermeier from Pixabay)

How can we count the number of stars in the galaxy?

On the BBC radio programme 'More or Less' it was mooted that there might be one hundred billion (100 000 000 000) stars in our own Milky Way Galaxy (and that this might be a considerable underestimate).

The estimate was suggested by Prof. Catherine Heymans who is
the Astronomer Royal for Scotland and Professor of Astrophysics at the University of Edinburgh.

Programme presenter Tim Harford was tackling a question sent in by a young listener (who is very almost four years of age) about whether there are more bees in the world than stars in the galaxy? (Spoiler alert: Prof. Catherine Heymans confessed to knowing less about bees than stars.)

An episode of 'More or Less' asks: Are there more bees in the world or stars in the galaxy?

Hatford asked how the 100 billion stars figure was arrived at:

"have we counted them, or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"

The last suggestion here is of course the basis for many surveys. As long as there is good reason to think a sample is representative of the wider population it is drawn from we can collect data from the sample and make inferences about the population at large.

Read about sampling a population

So, if we counted all the detectable stars in a typical 1% of the sky and then multiplied the count by 100 we would get an approximation to the total number of detectable stars in the whole sky. That would be a reasonable method to find approximately how many stars there are in the galaxy, as long as we thought all the detected stars were in our galaxy and that all the stars in our galaxy were detectable.

Prof. Heymans replied

"So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out 1% of all the stars in our Milky Way galaxy, creating a three dimensional map. So, that's looking at 1 billion of the stars, and then to get an idea of how many others are there we look at how bright all the stars are, and we use our sort of models of how different types of stars live [sic] in our Milky Way galaxy to give us that estimate of how many stars are there."

Prof. Catherine Heymans interviewed on 'More or Less'

A tautology?

This seemed to beg a question: how can we know we are mapping 1% of stars, before we know how many stars there are?

This has the appearance of a tautology – a circular argument.

Read about tautology

To count the number of stars in the galaxy,
  • (i) count 1% of them, and then
  • (ii) multiply by 100.

So,

  • If we assume there are one hundred billion, then we need to
  • count one billion, and then
  • multiply by 100 to give…
  • one hundred billion.

Clearly that did not seem right. I am fairly sure that was not what Prof. Haymans meant. As this was a radio programme, the interview was presumably edited to fit within the limited time allocated for this item, so a listener can never be sure that a question and (apparently immediately direct) response that makes the edit fully reflects the original conversation.

Counting the bright ones

According to the website of the Gaia mission, "Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye)." Hartman's suggestion that "you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?" seems very reasonable, until you realise that even with a powerful telescope sent outside of the earth's atmosphere, many of the stars in the galaxy may simply not be detectable. So, what we see cannot be considered to be fully representative of what is out there.

It is not then that the scientists have deliberately sampled 1%, but rather they are investigating EVERY star with an apparent brightness above a certain critical cut off. Whether a star makes the cut, depends on such factors as how bright it is (in absolute terms – which we might imagine we would measure from a standard distance 1) and how close it is, as well as whether the line of sight involves the starlight passing through interstellar dust that absorbs some (or all) of the radiation.

Of course, these are all strictly, largely, unknowns. Astrophysics relies a good on boot-strapping, where our best, but still developing, understanding of one feature is used to build models of other features. In such circumstances, observational tests of predictions from theory are often as much testing the underlying foundations upon which a model used to generate a prediction is built as that specific focal model itself. Knowledge moves on incrementally as adjustments are made to different aspects of interacting models.

Observations are theory-dependent

So, this is, in a sense, a circular process, but it is a virtuous circle rather than just a tautology as there are opportunities for correcting and improving the theoretical framework.

In a sense, what I have described here is true of science more generally, and so when an experiment fails to produce a result predicted by a new theory, it is generally possible to seek to 'save' the theory by suggesting the problem was (if not a human error) not in the actual theory being tested, but in some other part of the more extended theoretical network – such as the theory underpinning the apparatus used to collect data or the the theory behind the analysis used to treat data.

In most mature fields, however, these more foundational features are generally considered to be sound and unlikely to need modifying – so, a scientist who explains that their experiment did not produce the expected answer because electron microscopes or mass spectrometers or Fourier transform analyses do not work they way everyone has for decades thought they did would need to offer a very persuasive case.

However, compared to many other fields, astrophysics has much less direct access to the phenomena it studies (which are often vast in terms of absolute size, distance and duration), and largely relies on observing without being able to manipulate the phenomena, so understandably faces special challenges.

Why we need a theoretical model to finish the count

Researchers can use our best current theories to build a picture of how what we see relates to what is 'out there' given our best interpretations of existing observations. This is why the modelling that Prof. Heymans refers to is so important. Our current best theories tell us that the absolute brightness of stars (which is a key factor in deciding whether they will be detected in a sky survey) depends on their mass, and the stage of their 'evolution'.2

So, completing the count needs a model which allows data for detectable stars to be extrapolated, bearing in mind our best current understanding about the variations in frequencies of different kinds (age, size) of star, how stellar 'densities' vary in different regions of a spiral galaxy like ours, the distribution of dust clouds, and so forth.

…keep in mind we are off-centre, and then allow for the thinning out near the edges, remember there might be a supermassive black hole blocking our view through the centre, take into account dust, acknowledge dwarf stars tend to be missed, take into account that the most massive stars will have long ceased shining, then take away the number you first thought of, and add a bit for luck… (Image by WikiImages from Pixabay)

I have taken the liberty of offering an edited exchange

Hartford: "have we counted [the hundred billion stars], or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"

Heymans "So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out…all the stars in our Milky Way galaxy [that are at least magnitude 20 in brightness], creating a three dimensional map. So, that's looking at 1 billion of the [brightest] stars [as seen from our solar system], and then to get an idea of how many others are there we look at how bright all the stars are, and we use our models of how different types of stars [change over time 2] in our Milky Way galaxy to give us that estimate of how many stars are there."

No more tautology. But some very clever and challenging science.

(And are there more bees in the world or stars in the galaxy? The programme is available at https://www.bbc.co.uk/sounds/play/m00187wq.)

Note:

1 This issue of what we mean by the brightness of a star also arose in a recent post: Baking fresh electrons for the science doughnut

2 Stars are not alive, but it is common to talk about their 'life-cycles' and 'births' and 'deaths' as stars can change considerably (in brightness, colour, size) as the nuclear reactions at their core change over time once the hydrogen has all been reacted in fusion reactions.

COVID is like photosynthesis because…

An analogy based on a science concept

Keith S. Taber

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.

Read about science analogies

Photosynthesis and the pandemic

Professor Will Davies of Goldsmiths, University of London suggested that:

"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
This image has an empty alt attribute; its file name is Screenshot-2022-06-12-at-21.47.47.png
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.

Read about science metaphors

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.

Baking fresh electrons for the science doughnut

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.

The 'Science Donut': a recent episode of Ockham's Razor

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'.

Read about scientific certainty in the media

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).

Read about science metaphors

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.

Read about science analogies

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 conceptanalogue
a synchotrona 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 electronsracing '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.

https://www.ansto.gov.au/research/facilities/australian-synchrotron/overview

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."

Dr Emily Finch talking on Ockham's Razor
A big doughnut? The Australian Synchrotron (Source Australia's Nuclear Science and Technology Organisation)

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!

Read about anthropomorphism

The brilliant light

Dr Finch tells her audience that

"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."

https://www.diamond.ac.uk/Home/About/FAQs/About-Synchrotrons.html#

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.

Bats are [almost certainly] not closely related to viruses

Disputing the indisputable

Keith S. Taber

Scientific knowledge is provisional

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!)

Read about the nature of scientific knowledge

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.

Read about scientific certainty in the media

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…"!

To be fair, I came to this paper having already decided that the journal concerned was a predatory journal because it seemed to falsify its Impact Factor, and I had already read a paper in the journal which I felt could not possibly have been subject to peer review by experts in the field. (Was that indisputable? Well, let us say I would find it incredible that expert peer reviewers would not have raised serious concerns about some very obvious errors and omissions in the published paper.)

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.

Read about research writing

So, I read on.

Well, to the end of the sentence.

"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.

Read 'Intergenerational couplings in the family. A thought experiment about ancestry'

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
  • Taber, K. S. (2007) Documentaries can only mean one thing, Physics Education, 42 (1), pp.6-7
Note:

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.

 

Genes on steroids?

The high density of science communication

Keith S. Taber

Original photograph by Sabine Mondestin, double helix representation by OpenClipart-Vectors, from Pixabay 

One of the recurring themes in this blog is the way science is communicated in teaching and through media, and in particular the role of language choices, in effective communication.

I was listening to a podcast of the BBC Science in Action programme episode 'Radioactive Red Forest'. The item that especially attracted my attention (no, not the one about teaching fish to do sums) was summarised on the website as:

"Understanding the human genome has reached a new milestone, with a new analysis that digs deep into areas previously dismissed as 'junk DNA' but which may actually play a key role in diseases such as cancer and a range of developmental conditions. Karen Miga from the University of California, Santa Cruz is one of the leaders of the collaboration behind the new findings."

Website description of an item on 'Science in Action'
BBC 'Science in Action' episode first broadcast 3rd April 2022

They've really sequenced the human genome this time

The introductory part of this item is transcribed below.

Being 'once a science teacher, always a science teacher' (in mentality, at least), I reflected on how this dialogue is communicating important ideas to listeners. Before I comment in any detail, you may (and this is entirely optional, of course) wish to read through and consider:

  • What does a listener (reader) need to know to understand the intended meanings in this text?
  • What 'tactics', such as the use of figures of speech, do the speakers use to support the communication process?

Roland Pease (Presenter): "Good news! They sequenced, fully sequenced, the human genome.

'Hang on a minute' you cry, you told us that in 2000, and 2003, and didn't I hear something similar in 2013?' Well, yes, yes, and yes, but no.

A single chromosome stretched out like a thread of DNA could be 6 or 8 cm long. Crammed with three hundred million [300 000 000] genetic letters. But to fit one inside a human cell, alongside forty five [45] others for the complete set, they each have to be wound up into extremely tight balls. And some of the resulting knots it turns out are pretty hard to untangle in the lab. and the genetic patterns there are often hard to decode as well. Which is what collaboration co-leader Karen Miga had to explain to me, when I also said 'hang on a minute'."

Karen Miga: "The celebrated release of the finished genome back in 2003 was really focused on the portions that we could at the time map and assemble. But there were big persistent gaps. Roughly about two hundred million [200 000 000] bases long that were missing. It was roughly eight percent [8%] of the genome was missing."

"And these were sort of hard to get at bits of genome, I mean are they like trying to find a coin in the bottom of your pocket that you can't quite pull out?"

"These regions are quite special, we think about tandem repeats or pieces of sequences that are found in a head-to-tail orientation in the genome, these are corners of our genome where this is just on steroids, where we see a tremendous amount of tandem repeats sometimes extending for ten million [10 000 000] bases. They are just hard to sequence, and they are hard to put together correctly and that was – that was the wall that the original human genome project faced."

Introduction to the item on the sequencing of what was known as 'junk DNA' in the (a) human genome

I have sketched out a kind of 'concept map' of this short extract of dialogue:

A mapping of the explicit connections in the extract of dialogue (ignoring connections and synonyms that a knowledgeable listener would have available for making sense of the talk)

Read about concept maps

Prerequisite knowledge

In educational settings, teachers' presentations are informed by background information about the students' current levels of knowledge. In particular, teachers need to be aware of the 'prerequisite knowledge' necessary for understanding their presentations. If you want to be understood, then it is important your listeners have available the ideas you will be relying on in your account.

A scientist speaking to the public, or a journalist with a public audience, will be disadvantaged in two ways compared to the situation of a teacher. The teacher usually knows about the class, and the class is usually not as diverse as a public audience. There might be a considerable diversity of knowledge and understanding among the members of, say, the 13-14 year old learners in one school class, or the first year undergraduates on a university course – but how much more variety is found in the readership of a popular science magazine or the audience of a television documentary or radio broadcast.

Here are some key concepts referenced in the brief extract above:

  • bases
  • cells
  • chromosome
  • DNA
  • sequencing
  • tandem repeats
  • the human genome

To follow the narrative, one needs to appreciate relationships among these concepts (perhaps at least that chromosomes are found in cells; and comprised of DNA, the structure of which includes a number of different components called bases, the ordering of which can be sequenced to characterise the particular 'version' of DNA that comprises a genome. 1 ) Not all of these ideas are made absolutely explicit in the extract.

The notion of tandem repeats requires somewhat more in-depth knowledge, and so perhaps the alternative offered – tandem repeats or pieces of sequences that are found in a head to tail orientation in the genome – is intended to introduce this concept for those who are not familiar with the topic in this depth.

The complete set?

The reference to "A single chromosome stretched out…could be 6 or 8 cm long…to fit one inside a human cell, alongside forty five others for the complete set…" seems to assume that the listener will already know, or will readily appreciate, that in humans the genetic material is organised into 46 chromosomes (i.e., 23 pairs).

Arguably, someone who did not know this might infer it from the presentation itself. Perhaps they would. The core of the story was about how previous versions of 'the' [see note 1] human genome were not complete, and how new research offered a more complete version. The more background a listener had regarding the various concepts used in the item, the easier it would be to follow the story. The more unfamiliar ideas that have to be coordinated, the greater the load on working memory, and the more likely the point of the item would be missed.2

Getting in a tangle

A very common feature of human language is its figurative content. Much of our thinking is based on metaphor, and our language tends to be full [sic 3] of comparisons as metaphors, similes, analogies and so forth.

Read about scientific metaphors

Read about scientific similes

So, we can imagine 'a single chromosome' (something that is abstract and outside of most people's direct experience) as being like something more familiar: 'like a thread'. We can visualise, and perhaps have experience of, threads being 'wound up into extremely tight balls'. Whether DNA strands in chromosomes are 'wound up into extremely tight balls' or are just somewhat similar to thread wound up into extremely tight balls is perhaps a moot point: but this is an effective image.

And it leads to the idea of knots that might be pretty hard to untangle. We have experience of knots in thread (or laces, etc.) that are difficult to untangle, and it is suggested that in sequencing the genome such 'knots' need to be untangled in the laboratory. The listener may well be visualising the job of untangling the knotted thread of DNA – and quite possibly imaging this is a realistic representation rather than a kind of visual analogy.

Indeed, the reference to "some of the resulting knots it turns out are pretty hard to untangle in the lab. and the genetic patterns there are often hard to decode as well" might seem to suggest that this is not an analogy, but two stages of a laboratory process – where the DNA has to be physically untangled by the scientists before it can be sequenced, but that even then there is some additional challenge in reading the parts of the 'thread' that have been 'knotted'.

Reading the code

In the midst of this account of the knotted nature of the chromosome, there is a complementary metaphor. The single chromosome is "crammed with three hundred million genetic letters". The 'letters' relate to the code which is 'written' into the DNA and which need to be decoded. An informed listener would know that the 'letters' are the bases (often indeed represented by the letters A, C, G and T), but again it seems to be assumed this does not need to be 'spelt out'. [Sorry.]

But, of course, the genetic code is not really a code at all. At least, not in the original meaning of a means of keeping a message secret. The order of bases in the chromosome can be understood as 'coding' for the amino acid sequences in different proteins but strictly the 'code' is, or at least was originally, another metaphor. 4

Hitting the wall

The new research had progressed beyond the earlier attempts to sequence the human genome because that project had 'faced a wall' – a metaphorical wall, of course. This was the difficulty of sequencing regions of the genome that, the listener is told, were quite special.

The presenter suggests that the difficulty of sequencing these special regions of "hard to get at bits of genome" was akin to" trying to find a coin in the bottom of your pocket that you can't quite pull out". This is presumably assumed to be a common experienced shared by, or at least readily visualised by, the audience allowing them to better appreciate just how "hard to get at" these regions of the genome are.

We might pause to reflect on whether a genome can actually have regions. The term region seems to have originally been applied to a geographical place, such as part of a state. So, the idea that a genome has regions was presumably first used metaphorically, but this seems such a 'natural' transfer, that the 'mapping' seems self-evident. If it was a live metaphor, it is a dead one now.

Similarly, the mapping of the sequences of fragments of chromosomes onto the 'map' of the genome seems such a natural use of the term may no longer seem to qualify as a metaphor.

Repeats on steroids

These special regions are those referred to above as having tandem repeats – so parts of a chromosome where particular base sequences repeat (sometimes a great many times). This is described as "pieces of sequences that are found in a head to tail orientation" – applying an analogy with an organism which is understood to have a body plan that has distinct anterior and posterior 'ends'.

Not only does the genome contain such repeats, but in some places there are a 'tremendous' number of these repeats occurring head to tail. These places are referred to as 'corners' of the genome (a metaphor that might seem to fit better with the place in a pocket where a coin might to be hard to dislodge – or perhaps associated with that wall), than with a structure said to be like a knotted, wound-up, ball of thread.

It is suggested that in these regions, the repeats of the same short base sequences can be so extensive that they continue for billions of bases. This is expressed through the simile that the tandem repeating "is just on steroids" – again an allusion to what is assumed to be a familiar everyday phenomenon, that is, something familiar enough to people listening to help then appreciate the technical account.

Many people in the audience will have experience of being on steroids as steroids are prescribed for a wide variety of inflammatory conditions – both acute (due to accidents or infections) and chronic (e.g., asthma). Yet these are corticosteroids and 'dampen down' (metaphorically, of course) inflammation. The reference here is to anabolic steroid use, or rather abuse, by some people attempting to quickly build up muscle mass. Although anabolic steroids do have clinical use, abusers may take doses orders of magnitude higher than those prescribed for medical conditions.

I suspect that whereas many people have personal experience or experience of close family being on corticosteroids, whereas anabolic steroid use is rarer, and is usually undertaken covertly – so the metaphor here lies on cultural knowledge of the idea of people abusing anabolic steroids leading to extreme physical and mood changes.

Making a good impression

That is not to suggest this metaphor does not work. Rather I would suggest that most listeners would have appreciated the intended message implied by 'on steroids', and moreover the speaker was likely able to call upon the metaphor implicitly – that is without stopping to think about how the metaphor might be understood.

Metaphors of this kind can be very effective in giving an audience a strong impression of the scientific ideas being presented. It is worth noting, though, that what is communicated is to some extent just that, an impression, and this kind of impressionist communication contrasts with the kind of technically precise language that would be expected in a formal scientific communication.

Language on steroids

Just considering this short extract from this one item, there seems to be a great deal going on in the communication of the science. A range of related concepts are drawn upon as (assumed) background and a narrative offered for why the earlier versions of the human genome were incomplete, and how new studies are producing more complete sequences.

Along the way, communication is aided by various means to help 'make the unfamiliar familiar' by using both established metaphors as well as new comparisons. Some originally figurative language (mapping, coding, regions) is now so widely used it has been adopted as literally referring to the genome. Some common non-specific metaphors are used (hitting a wall, hard to access corners), and some specific images (threads, knots and tangles, balls, head-tails) are drawn upon, and some perhaps bespoke comparisons are introduced (the coin in the pocket, being on steroids).

In this short exchange there is a real mixture of technical language with imagery, analogy, and metaphor that potentially both makes the narrative more listener-friendly and helps bridge between the science and the familiar everyday – at last when these figures of speech are interpreted as intended. This particular extract seems especially 'dense' in the range of ideas being orchestrated into the narrative – language on steroids, perhaps – but I suspect similar combinations of formal concepts and everyday comparisons could be found in many other cases of public communication of science.

An alternative concept map of the extract, suggesting how someone with some modest level of background in the topic might understand the text (filling in some implicit concepts and connections). How a text is 'read' always depends upon the interpretive resources the listener/reader brings to the text.

At least the core message was clear: Scientists have now fully sequenced the human genome.

Although, I noticed when I sought out the scientific publication that "the total number of bases covered by potential issues in the T2T-CHM13 assembly [the new research] is just 0.3% of the total assembly length compared with 8% for GRCh38 [The human genome project version]" (Nurk et al., 2022) , which, if being churlish, might be considered not entirely 'fully' sequenced. Moreover "CHM13 lacks a Y chromosome", which – although it is also true of half of the human population – might also suggest there is still a little more work to be done.

Work cited:
  • Nurk, S., Koren, S., Rhie, A., Rautiainen, M., Bzikadze, A. V., Mikheenko, A., . . . Phillippy, A. M.* (2022). The complete sequence of a human genome. Science, 376(6588), 44-53. doi:doi:10.1126/science.abj6987
Notes

1 We often talk of DNA as a substance, and a molecule of DNA as 'the' DNA molecule. It might be more accurate to consider DNA as a class of (many) similar substances each of which contains its own kind of DNA molecule. Similarly, there is not a really 'a' human genome – but a good many of them.

2 Working memory is the brain component where people consciously access and mentipulate information, and it has a very limited capacity. However, material that has been previously learnt and well consolidated becomes 'chunked' so can be accessed as 'chunks'. Where concepts have been integrated into coherent frameworks, the whole framework is accessed from memory as if a single unit of information.

Read about working memory

3 Strictly only a container can be full – so, this is a metaphor. Language is never full -as we can always be more verbose! Of course, it is such a familiar metaphor that it seems to have a literal meaning. It has become what is referred to as a 'dead' metaphor. And that is, itself, a metaphor, of course.

4 Language changes over time. If we accept that much of human cognition is based on constructing new ways of thinking and talking by analogy with what is already familiar (so the song is on the 'top' of the charts and it is a 'long' time to Christmas, and a 'hard' rain is going to fall…) then language will grow by the adoption of metaphors that in time cease to be seen as metaphors, and indeed may change in their usage such that the original reference (e.g., as with electrical 'charge') may become obscure.

In education, teachers may read originally metaphorical terms in terms of teir new scientific meanings, whereas learners may understand the terms (electron 'spin', 'sharing' of electrons, …) in terms of the metaphorical/analogical source.

*This is an example of 'big science'. The full author list is:

Sergey Nurk, Sergey Koren, Arang Rhie, Mikko Rautiainen, Andrey V. Bzikadze, Alla Mikheenko, Mitchell R. Vollger, Nicolas Altemose, Lev Uralsky, Ariel Gershman, Sergey Aganezov, Savannah J. Hoyt, Mark Diekhans, Glennis A. Logsdon,p Michael Alonge, Stylianos E. Antonarakis, Matthew Borchers, Gerard G. Bouffard, Shelise Y. Brooks, Gina V. Caldas, Nae-Chyun Chen, Haoyu Cheng, Chen-Shan Chin, William Chow, Leonardo G. de Lima, Philip C. Dishuck, Richard Durbin, Tatiana Dvorkina, Ian T. Fiddes, Giulio Formenti, Robert S. Fulton, Arkarachai Fungtammasan, Erik Garrison, Patrick G. S. Grady, Tina A. Graves-Lindsay, Ira M. Hall, Nancy F. Hansen, Gabrielle A. Hartley, Marina Haukness, Kerstin Howe, Michael W. Hunkapiller, Chirag Jain, Miten Jain, Erich D. Jarvis, Peter Kerpedjiev, Melanie Kirsche, Mikhail Kolmogorov, Jonas Korlach, Milinn Kremitzki, Heng Li, Valerie V. Maduro, Tobias Marschall, Ann M. McCartney, Jennifer McDaniel, Danny E. Miller, James C. Mullikin, Eugene W. Myers, Nathan D. Olson, Benedict Paten, Paul Peluso, Pavel A. Pevzner, David Porubsky, Tamara Potapova, Evgeny I. Rogaev, Jeffrey A. Rosenfeld, Steven L. Salzberg, Valerie A. Schneider, Fritz J. Sedlazeck, Kishwar Shafin, Colin J. Shew, Alaina Shumate, Ying Sims, Arian F. A. Smit, Daniela C. Soto, Ivan Sović, Jessica M. Storer, Aaron Streets, Beth A. Sullivan, Françoise Thibaud-Nissen, James Torrance, Justin Wagner, Brian P. Walenz, Aaron Wenger, Jonathan M. D. Wood, Chunlin Xiao, Stephanie M. Yan, Alice C. Young, Samantha Zarate, Urvashi Surti, Rajiv C. McCoy, Megan Y. Dennis, Ivan A. Alexandrov, Jennifer L. Gerton, Rachel J. O'Neill, Winston Timp, Justin M. Zook, Michael C. Schatz, Evan E. Eichler, Karen H. Miga, Adam M. Phillippy

Monkeys that do not give a fig about maggotty fruit?

Some spider monkeys like a little something extra with "all this fruit"

Keith S. Taber

(Photograph by by Manfred Richter from Pixabay)

"oh heck, what am I going to do, I'm faced with all this fruit with no protein and I've got to be a spider monkey"

Primatologist Adrian Barnett getting inside the mind of a monkey

I was listening to an item on the BBC World Service 'Science in Action' programme/podcast (an episode called 'Climate techno-fix would worsen global malaria burden').

This included an item with the title:

Primatologist Adrian Barnett has discovered that spider monkeys in one part of the Brazilian Amazon seek out fruit, full of live maggots to eat. Why?
BBC Science in Action episode included an item about spider monkey diets

The argument was that the main diet of monkeys is usually fruit which is mostly very low in protein and fat. However, often monkeys include figs in their diet which are an exception, being relatively rich in protein and fats.

The spider monkeys in one part of the Amazon, however, seem to 'seek out' fruit that was infested with maggots – these monkeys appear to actively choose the infected fruits. These are the fruits a human would probably try to avoid: certainly if there were non-infested alternatives. Only a proportion of fruit on the trees are so infested, yet the monkeys consume a higher proportion of infested fruit and so seem to have a bias towards selecting fruit with maggots. At least that was what primatologist Dr Adrian Barnett's analysis found when he analysed the remains of half-eaten fruit that reached the forest floor.

The explanation suggested is that this particular area of forest has very few fig trees, therefore it seems these monkeys do not have ready access to figs, and it seems they instead get a balanced diet by preferentially picking fruit containing insect larvae.

Who taught the monkeys about their diet?

A scientific explanation of this might suggest natural selection was operating.

Even if monkeys had initially tended to avoid the infested fruit, if this then led to a deficient diet (making monkeys more prone to disease, or accidents, and less fertile) then any monkeys who supplemented the fruit content of their diet by not being so picky and eating some infested fruit (whether because of a variation in their taste preferences, or simply a variation in how careful they were to avoid spoilt fruit) would have a fitness advantage and so, on average, leave more offspring.

To the extent their eating habits reflected genetic make-up (even if this was less significant for variations in individual behaviour than contingent environmental factors) this would over time shift the typical behaviours in the population. Being willing to eat, or perhaps even enjoying, maggotty fruit was likely to be a factor in being fertile and fecund, so eventually eating infested fruit becomes the norm – at least as long as the population remains in a habitat that does not have other ready sources of essential dietary components. Proving this is what happened would be very difficult after the fact. But an account along these lines is consistent with our understanding of how behaviour tends to change.

An important aspect of natural selection is that it is an automatic process. It does not require any deliberation or even conscious awareness on behalf of the members of the population being subject to selection. Changes do not occur in response to any preference or purpose – but just reflect the extent to which different variants of a population match their environment.

This is just as well, as even though monkeys are primates, and so relatively intelligent animals, it seems reasonable to assume they do not have a formal concept of diet (rather, they just eat), and they are not aware of the essential need for fat and protein in the diet; nor of the dietary composition of fruit. Natural selection works because where there is variation, and differences in relative fitness, the fittest will tend to leave more offspring (as by fittest we simply mean those most able to leave offspring!)

Now he's thinking…

I was therefore a little surprised when the scientist being interviewed, Adrian Barnett, explained the behaviour:

"So, suddenly the monkey's full of, you know, squeaking the monkey equivalent of 'oh heck, what am I going to do, erm, I'm faced with all this fruit with no protein and I've got to be a spider monkey'."

Adrian Barnett speaking on Science in Action

At first hearing this sounds like anthropomorphism, where non-humans are assigned human feelings and cognitions.

Anthropomorphic language refers to non-human entities as if they have human experiences, perceptions, and motivations. Both non-living things and non-human organisms may be subjects of anthropomorphism. Anthropomorphism may be used deliberately as a kind of metaphorical language that will help the audience appreciate what is being described because of its similarly to some familiar human experience. In science teaching, and in public communication of science, anthropomorphic language may often be used in this way, giving technical accounts the flavour of a persuasive narrative that people will readily engage with. Anthropomorphism may therefore be useful in 'making the unfamiliar familiar', but sometimes the metaphorical nature of the language may not be recognised, and the listener/reader may think that the anthropomorphic description is meant to be taken at face value. This 'strong anthropomorphism' may be a source of alternative conceptions ('misconceptions') of science.

Read about anthropomorphism

What goes through a monkey's mind?

Why 'at first hearing this seems like an example of anthropomorphism'? Well, Dr Barnett does not say the monkey actually has these thoughts but rather squeaks the monkey equivalent of these words. This leaves me wondering how we are to understand what the monkey equivalent actually is. I somehow suspect that whatever thoughts the monkey has they probably do not include any direct equivalents of either being a spider monkey or protein.

I am happy to accept the monkey has a concept somewhat akin to our fruit, as clearly the monkey is able to discriminate particular regularities in its environment that are associated with the behaviour of picking items from trees and eating them – regularities that we would class as fruit. It is interesting to speculate on what would be included in a monkey's concept map of fruit, were one able to induce a monkey to provide the data that might enable us to produce such a diagram. Perhaps there might be monkey equivalents of such human concepts as red and crunchy and mushy…but I would not be expecting any equivalents of our concepts of dietary components or nutritional value.

So, although I am not a primatologist, I wonder if the squeaking Dr Barnett heard when he was collecting for analysis the partially eaten fruit dropped by the spider monkeys was actually limited to the monkey equivalent of either "yummy, more fruit" or perhaps "oh, fruit again".