conservation of energy - Science-Education-Research

A Christmas miracle – magic physics powers new heater designs

Keith S. Taber

Looking to check out some music videos on YouTube, and being presented with irrelevant advertisements, I was amazed to learn of a revolutionary new type of electrical heater that can potentially offer consumers vast savings on their electricity bill. Revolutionary, as the inventor, a disgraced London student, seems to have rewritten the laws of physics.

He made a special device that creates a perpetual heating loop,

Revolutionary design: "a perpetual heating loop" (a coil of wire that can be left connected to a power supply?)

Warning. The copyright in the images included here does not belong to me. I think much the video looks like it uses stock footage, but if not, and IF the company behind this product believes they can genuinely support their claims as reported here, they may get in touch to explain why I am misguided.

I generally look to respect copyright in other's work, but I believe it is in the public interest to call out attempts to scam people through misrepresenting science in material in the public domain.

The revolutionary new design of heater is a small plug-in device which can heat up a room very quickly, and moreover it is so efficient that it does not waste energy – like those other more traditional types of heaters some people might still be using.

This technological advance:

can heat a home in 90 seconds
can save a householder thousands of pounds a year
"can warm any space at 90% less cost than conventional heating methods"
avoids any waste: "by reusing the heat it produces, so none of it is wasted"
on testing, it warmed university classrooms "from 10˚C to 21˚C in only 2 minutes"
uses "89% less energy" than regular heating systems

Wow. If not too good to be true, that would certainly help with the climate crisis by reducing electricity demands.

What is the new technology?

The video advertising this new type of heater offer some clues to its design. It begins by illustrating the "trick" which can "heat your home in 90 seconds" and "save thousands of pounds" off the Winter heating bill:

So, it seems you need to get some tea lights, and place them under a large inverted ceramic flower pot? I am pretty sure that's not going to do the 'trick'. Perhaps this was meant as some kind of metaphor…?

Reinstate Jason!

The video explains how 'Jason' "a clever student from UK, London University" creates the new type of heater because the University heating system was not functioning properly. He designed the new heater to support his classmates who were having to work in rooms at 10˚C.

When Jason refused to earn a fortune from his invention by selling the rights, the University responded within three days by expelling him. ¹

His professor even predicted tat Jason was destined to make history.

Jason's professor thought his idea was revolutionary (but he may not be that up to date in his subject knowledge – most of the scientific community adopted metric units decades ago ²)

Apparently Jason achieved this scientific breakthrough by 'reverse-engineering' a standard heater. Presumably the available text books did not explain the physics of heaters (in essence, you connect (i) a piece of conducting material that can withstand heating and that has suitable resistance, to (ii) a power supply); so he had take apart heaters to find out how they worked.

he cleverly figured out how to reverse engineer basic air heater.

Here he seems to be drawing up the specifications for his new design, helped by a sophisticated paper model.

just destroyed the billion pounds heating industry by innovating a device

The video shows how Jason studied circuit components called 'resistors' and found out how to read those little coloured lines on them (as children do in UK schools).

So what was revolutionary about the physics?

Of course, the manufacturers do not want to give away too many commercial secrets (even if Jason had nobler instincts), but the video does offer some clues.

Induction heating

One technique shown in the film is described as "a special device that creates a perpetual heating loop".

The special device illustrated seems to be a coil of thick copper wire, able to pass a large alternating current, which is heating a metal rod 'by induction'.

This works because the coil produces a large constantly changing magnetic field, which induces a changing e.m.f. in the rod. Now this technique only produces heating in an electrical conductor as the magnetic field cannot transfer energy to an insulator, such as air (which is not substantially influenced by the magnetic field). It seems Jason's genius must have been to somehow produce heating of ordinary air by this method. That would be the kind of breakthrough reflecting new physics deserving of a Nobel prize!

The dual Thomson effects

My ageing hearing told me that Jason's revolutionary design used the Joule-Thomson effect. This surprised me a little, as to my mind this technique would produce cooling, not heating. This effect can be experienced in everyday effects – such as in the material propelled from an aerosol can which often feels cold, or when noting the cold air passing out of the valve of a tyre being quickly deflated.

Energy is always conserved in all processes. The conservation of energy is one of the most fundamental principles in science, and is generally believed to be universal in its application. (Thus my annoyance at how the English National Curriculum includes a logically flawed reference to it.) When a compressed gas (such as in the tyre) is allowed to expand through a small opening it does work pushing back the surrounding air, and the temperature drops by a corresponding amount. ³

So, I was mystified at how an effect that usually produced cooling here gives the opposite effect. But then I spotted (from the kindly provided subtitles) that I (or else, the person making the subtitles?) had misheard. It seems Jason was using a different effect: 'dual Thomson' physics.

Jason made it work better, using a dual Thomson physics

I have to confess to not being familiar with 'dual Thomson' physics. Indeed I only found a handful of references on the www through an internet search, and these referred to specialised instruments designed to detect ion velocities in high energy physics research.

I am not sure what that has to do with plug-in wall heaters, and I am pretty sure that that was not what was illustrated in the accompanying footage.

Testing the new design

A powerful device?

According to the video being pushed at viewers by YouTube, Jason "took this amazing gadget to the University and the outcomes were fantastic" where "classrooms went from 10˚C to 21˚C in only 2 minutes".

Before and after – the small device heated a classroom 11˚C in 12o seconds. Hm. (Move the slider to see the images)

classrooms went from 10˚C to 21˚C in only 2 minutes. — Before and after – the small device heated a classroom 11˚C in 12o seconds. Hm. (Move the slider to see the images)

Now that would be pretty impressive, as any lecturer who has arrived in a cold teaching room and then dragged in the electric heater from their office would know (I write from experience).

We are not told the size of the room used in this supposed trial but a lecture room would be something of the order of a thousand cubic metres. If we assume that the heater transfers all of its energy to the air in the room (and that in the short time it is used, none of this heat is lost to outside, or warms up anything else in the room – like the furnishings or the walls or ceilings – or the people who were feeling too cold) then we can calculate the energy needed, and so the power of the heater. My-back-of-the-envelope calculation suggests this would be about 100 kW. ⁴

this innovation swiftly warms rooms using minimal electricity, efficiently

Now I am not going to claim that a hundred kilowatts heater cannot be made, but I am prepared to suggest that no technology available today could safely get near, anywhere near, this power rating with this scale of device.

Larger heaters designed for industrial use are available rated for a few kilowatts, but a 100 kW plug-in heater for domestic use seems fantasy. (Especially as "You can move it around without worrying about burning yourself" according to the website.)

Am I wrong? TechTrends, the website selling the devices (sorry, independently assessing, 😉, 😉, the devices and telling us where to buy them), does not seem to offer any details on this testing, so I assume it was not carried out by competent investigators and reported in a peer reviewed journal. If indeed, given the non-viability of the claim, it really took place. Anyone reading this form TechTrends – if I am wrong please enlighten us? (Comments welcome below.)

Greater efficiency?

We are asked to accept this magical outcome because the device is so energy efficient (that in itself I believe – I expect an electric heater to be very efficient), compared with standard technology. The video claims that the new heater "used 89% less energy" than "regular heating systems". That is clearly nothing other than an outright lie!

What's even more impressive is that it used 89% less energy — Feel the difference – almost 90% apparently (Move the slider to see the images)

compared to regular heating systems. — Feel the difference – almost 90% apparently (Move the slider to see the images)

Many machines are inefficient in the sense that the energy input does not match the desired work output as some energy is 'lost' or perhaps better 'diverted'. Now energy is always conserved, so this means that, say, 100 Joules of energy are 'taken' from some supply to power some activity, but perhaps only 6oJ does what we intend (so in this case, 60% efficiency) and the other 40J has some other effect.

A key idea in thermodynamics is that engines have an inherent limit to efficiency. A car engine exhausting into the atmosphere well above absolute zero (at around 300K rather than 0K) will necessarily only direct a fraction of the energy sourced into the desired locomotion. Achieving higher temperatures in the engine (a technical challenge) can improve what is possible; but only releasing exhaust gases at 0K would make 100% efficiency even theoretically possible. So, is it feasible that normal electrical heaters would be so inefficient?

Filament lamps are only inefficient in the Summer

…or…

Why would anyone manufacture a light bulb completely encased in a solid metal shade?

The notion that a standard electric heater might be no more than 11% efficient might not sound too unlikely to some people watching these commercials as they wait for their music videos (or cats juggling, or whatever their taste may be). One reason filament lamps have been phased out is because they were notoriously inefficient – indeed, 11% efficiency is the kind of figure that was sometimes quoted. A 100 W filament lamp might only be generating visible light at around 11W, which seems quite a waste (especially as the utility company will be billing for all 100W).

I have always considered such lamps to be inefficient in the Summer, but that this is less of an issue in the Winter. That's because that other 89W will be heating up the room – unhelpful or even problematic in Summer, but perhaps acceptable in Winter when we are deliberately heating the rooms anyway. Does it matter if a little more of your heating comes from the light bulbs and a little less from the 'heaters'.

Indeed, when I was a child, before the days when most people had central heating, we used to have a device that was basically a light bulb inside a big metal shield. When turned on, it emitted no light. The bulb did, of course, but not the device. These were used on Winter evenings as bed warmers to avoid getting into a very cold bed. The lamp may have given out 11% light, but it all ultimately got absorbed into the metal and contributed to the heat transfer from filament to bed warmer and so onto the bedding. ⁵

Generally, energy inefficiencies in machines involve energy released as heat that goes to make molecules move about a bit faster on average rather than going where intended to do useful jobs. We might think of heat (or strictly, the dispersed thermal energy of matter, that heat leads to) as the lowest quality form of energy, that all other forms of energy are ultimately, eventually, degraded into.

This unintended 'heat leakage' may be an issue in lamps and motors and televisions and many other devices – but clearly not in heaters.

The same old hot air…

The video suggests one feature of the revolutionary new design is that instead of only heating cold air, the promoted device is able to recycle warm air to minimise waste. What could this mean?

HeatFlow's heating ability surpasses those of any standard system,

recycling warm air to minimize energy waste,

Now if you take an electric heater out into the garden on a cold day when there is a breeze, then it is quite likely that the air that passes through the heater will be blown away quite quickly, and so the heater is always heating air from the same ambient starting point. That would be a bit of a waste. (Hint: do not use an electric heater to keep you warm in the garden – put on warm clothes or move around instead).

Inside a well insulated room, the air that is passing through the heater will soon already have been warmed, so the heater can achieve a higher room temperature for the same power input (compared with when it is operating in your garden, that is). I do not think any reasonable reading of 'standard system' for home heating would not "recycle warm air" rather that continuously heating only cold air, so to my reading this is simply a clear lie.

Some made up numbers from the website 'reviewing' (actually, promoting) the device

90% less cost to the householder?

I therefore consider the claim that the new design of heater "can warm any space at 90% less cost than conventional heating methods" is also a simple lie. Your standard home plug-in heater might not be as well designed, and may have some flaws, but it will not be converting 89 0r 90% of the energy supply into something other than heat. Inefficient machines produce heat instead of other (generally more useful) forms of output.

that can warm any space at 90% less cost tan conventional heating methods.

No, it cannot.

Not unless we've had some basic physics completely wrong for a long time and no one had noticed.

As has been often pointed pointed out, any claim that begins "in fact…" should be treated suspiciously. There is no logical difference between writing

"these claims are inconsistent with the laws of physics", and
"in fact, these claims are inconsistent with the laws of physics"

'In fact' tends to be used rhetorically when what is being said might of itself not seem a very convincing 'fact', and could otherwise be surprising, as in,

"in fact, Albert Einstein never actually found physics interesting"

In fact, it has been proven to be 97% more cost effective

In fact, this is another lie.

The video directs readers to what seems at first sight to be a consumer website praising the new heaters, although they've dropped the story about poor, mistreated Jason,

"This simple but rather genius concept was developed in 2019 by a group of electrical engineers from the EVI (Electric Vehicle Industry)."

There seem to be at least two versions directing to the same basic copy promoting 'EcoWell' and 'HeatFlow' on different webpages. Some customers (such as a 'Daniel Walker') seem to have even sought out both designs, presumably to match their decor in different rooms?

The web-pages do not repeat the more obviously fraudulent claims, but rather seem to suggest the heater is going to save money by pointing out how much heat produced by a domestic heating system is leaving the home. This is important, but it is worth n0oting that (assuming that a house can never have perfect thermal insulation) then when the home has reached a constant temperature (and the external temperature is not changing), the amount of heat being lost to the environment matches that produced by the heaters. That is, 100% of the energy being used for heating is being transferred to the outside. It is important to try to slow that rate, but all heating systems, "leak energy, warming up basements and underground lines", not just those that are "outdated and inefficient" as the TechTrends website implies.

It still claims that "99.8% efficiency ensures all your electricity gets turned into heat, saving you thousands" (where any heater will be highly efficient at producing heat – the issue is how it is distributed), but acknowledges.

"One HeatFlow heater can heat up a room up to 12 square meters. Depending on your needs, you might want to purchase several heaters for continuous warmth in all rooms or keep one to bring with you where you need it the most."

"One EcoWell heater can heat up a room up to 12 square meters. Depending on your needs…"

(The EcoWell design looks very similar to an alternative available from a well-established and reputable manufacturer selling their product on Amazon at £20 when I checked today. Whereas TrechTrends tells readers that with the half price discount "At the moment of writing this review, you can get EcoWell[*] for just £49.99!" [* or HeatFlow if you prefer the tiny coal fireplace look]

So, if you stop heating the house, and just have one single plug-in device that you move around to the room that you are going to be occupying, it will save money on your energy bills. But that will not work if you like frequently moving between rooms in your house, or have a family that like some privacy. (Of course, you can save even more money on your bills by wearing a good many layers of clothing and not using any heaters. )

Still, the website shows there have been many favourable customers' comments, which I rather spoiled yesterday with my own cynical offering:

But that was yesterday, and checking back today I was un-amazed to find my comment wiped. In any case, there is an acknowledgement showing the site is an advert, and the photos are of 'models' not real purchasers:

But it is presented in faint text on a black background seemingly designed to make sure it is not easily noticed ⁶ .

There is of course a special price if you buy now within 24 hours…

As there was yesterday.

Does it matter?

So these advertisements contain some very misleading 'bad science' (or, perhaps – as the claims are inconsistent with well-studied science – magical claims). Misinformation like this is is common in the post-truth age – but here it is masquerading as engineering and physics.

Anyone who has been to school and benefited from science education should not be taken in by the sillier claims about this new design of heater. They may be very useful, compact, convenient, and perhaps even powerful-for-their-size heaters. But the more extreme claims being made are lies, contrary to basic physics.

They cannot heat a classroom in 2 minutes. They are not 97% more cost effective. They will not save people thousands of pounds if used to replace other plug-in heaters. They do not use induction (or tea lights) to heat the air or dual Thomson physics. And although they recycle hot air, so does every other type of room heater. They may well be over 99% efficient, but that's because heat is the lowest grade of energy and so increasing machine efficiency is about avoiding 'high grade' energy being reduced to heat. The claim here is like claiming your teenager is better than the standard model because it can turn an organised bedroom into arbitrarily organised chaos – as if that was a rare quality, given that most teenagers are only ever able to mess up part of a room.

The video is in breach of UK law and YouTube should have done due diligence before accepting advertising money for such deliberately dishonest films. I feel somewhat offended that YouTube would think that an educated person would fall for this – but presumably plenty do. If people are listening to/watching this nonsense and not spotting a problem, then science education has not done a very good job. This kind of scam relies on low levels of scientific literacy.

But, I suspect these companies are getting plenty of sales from their dishonest advertising as in October 2022 I wrote to the Advertising Standards Authority (ASA) to complain about very similar adverts:

"Brand/product: AlphaHeater or Elite Heat

Your complaint: After watching a football match on you tube there was a misleading video, which directed viewers to a misleading website. The video claimed that a revolutionary new heater using jet engine technology would heat a room "using 90% less energy" (screen shot below). This is nonsense (I am a Chartered Physicist, Fellow of the Institute of Physics: heat is the lowest quality form of heat, so (unlike say the working of a motor) a heater cannot be produced so much more more efficiently.). The website was pretending to be an independent review (HeatReviewGuide) of the heater but had dummy links and was only advertising that product (see below). …
Acknowledgement of complaint: October 2022

seems familiar?

The ASA replied

"Thank you for contacting the Advertising Standards Authority (ASA) about ads online for this heating device and for your patience while your complaint was considered.

We acknowledge your concern about this ad and so we have put an alert out to have it taken down through our ASA Scam Ad Alert System. We will share the details of this ad with our network of key industry partners, including all the major social media platforms and ad networks operating in the UK, so that the content is taken down and to help stop similar ads appearing in future."
Outcome of compliant: November 2022

I guess criminals behind these scams respond to this regulation of advertisements by changing the name or other minor details of their products, and then just carrying on. Time for another message to the ASA?

Merry Christmas everyone.

Notes

¹ Even if we believe that Universities still readily expel fee-paying 'customers' for the most vile of offences, and even if we think that refusing to become a billionaire amounts to grounds for such an expulsion (why?) – the idea that a university could act in three days on a student disciplinary matter and follow due process does not ring true. (I know from personal experience there are plenty of people in universities who are prepared to ignore principles of natural justice, but luckily the institutions themselves have careful and balanced procedures to protect members from false and malicious claims). Jason could always have got his University's Enterprise department to help him arrange the commercialisation of the design, and then signed over any personal interests to generate income for a charitable trust.

² I am assuming that psi means pounds per square inch. The scientific units are pascals (that is newtons per square metre) which were already been taught in school when I was a pupil half a century ago.

³Temperature is NOT the same as heat, of course, but a certain temperature change in a sample of a substance involves the transfer of a related amount of energy that for a characterised material can be calculated (heat = product of mass by specific heat capacity by temperature change; 𝚫H = mc𝛉).

⁴I used:

The density of air is about 1200 grammes per cubic metre
the specific heat capacity of air is about 1 Jg^-1K^-1
power = energy transferred / time [= 120s]

⁵ We usually think of light and heat as discrete. But heating is energy transferred due to a difference in temperature: so when radiation is emitted by a hot body and absorbed by a colder one it counts as heat, even if it is light. So heat is not necessary light, but light often counts as heat. As they say, there's often 'more heat than light'.

⁶ Just in case you are finding the text difficult to make out, it reads:

"THIS IS AN ADVERTISEMENT AND NOT AN ACTUAL NEWS ARTICLE, BLOG, OR CONSUMER PROTECTION UPDATE

ADVERTISING DISCLOSURE: THIS WEBSITE AND THE PRODUCTS & SERVICES REFERRED TO ON THE SITE ARE ADVERTISING MARKETPLACES. THIS WEBSITE IS AN ADVERTISEMENT AND NOT A NEWS PUBLICATION. ANY PHOTOGRAPHS OF PERSONS USED ON THIS SITE ARE MODELS. THE OWNER OF THIS SITE AND OF THE PRODUCTS AND SERVICES REFERRED TO ON THIS SITE ONLY PROVIDES A SERVICE WHERE CONSUMERS CAN OBTAIN AND COMPARE."

A molecular Newton's cradle?

A chain reaction with no return

Keith S. Taber

Have chemist's created an atomic scale Newton's cradle?

(Image by Michelle from Pixabay)

Mimicking a Newton's cradle

I was interested to read in an issue of Chemistry World that

"Scientists in Canada have succeeded in setting off a chain of reactions in which fluorine atoms are passed between molecules tethered to a copper surface. The sequence can be repeated in alternating directions, mimicking the to-and-fro motions of a Newton's cradle."
Blow, 2022

The Chemistry World report explained that

"The team of researchers…affixed fluorocarbons to a [copper] surface by chemisorption, constructing chains of CF₃ molecules terminated by a CF₂molecule – up to four molecules in total….

The researchers applied an electron impulse to the foremost CF₃ molecule, causing it to spit out a fluorine atom along the chain. The second CF₃ absorbed this atom, but finding itself unstable, ejected its leading fluorine towards the third molecule. This in turn passed on a fluorine of its own, which was taken up by the taken up by the CF₂ molecule in fourth position."
Blow, 2022

There is some interesting language here – a molecule "spits out" (a metaphor?) an atom, and another "finds itself" (a hint of anthropomorphism?) unstable.

Molecular billiards?
Can a line of molecules 'tethered' onto a metal surface behave like a Newton's cradle?

Generating reverse swing

The figure below was drawn to represent the work as described, showing that "another electron impulse could be used to set… off…a reverse swing".

A representation of the scheme described in *Chemistry World*. The different colours used for the fluorine 'atoms' ¹ are purely schematic to give a clear indication of the changes – the colours have no physical significance as all the fluorine atoms are equivalent. ² The molecules are shown here as if atoms were simply stuck to each other in molecules (rather than having become one larger multi-nuclear structure) for the same reason. ¹ In science we select from different possible models and representations for particular purposes.³

That reference to "another electron impulse" being needed is significant,

"What was more, each CF₃ had been flipped in the process, so the Newton's cradle as a whole was a mirror image of how it had begun, giving the potential for a reverse swing. Unlike a desk Newton's cradle, it did not swing back on its own accord, but another electron impulse could be used to set it off."
Blow, 2022

"***…the Newton's cradle as a whole was a mirror image of how it had begun***"

Mirroring a Newton's cradle

Chemistry World is the monthly magazine of the Royal Society of Chemistry (a learned society and professional body for chemists, primarily active in the UK and Eire) sent to all its members. So, Chemistry World is part of the so-called secondary literature that reports, summarises, and comments on the research reports published in the journals that are considered to comprise the primary academic literature. The primary literature is written by the researchers involved in the individual studies reported. Secondary literature is often written by specialist journalists or textbook authors.

The original report of the work (Leung, Timm & Polanyi, 2021) was published in the research journal Chemical Communications. That paper describes how:

"Hot [sic] F-atoms travelling along the line in six successive 'to-and-fro' cycles paralleled the rocking of a macroscopic Newton's cradle."
Leung, Timm & Polanyi, 2021, p.12647

A simple representation of a Newton's cradle (that is, "*a macroscopic Newton's cradle*")

These authors explain that

"…energised F can move to- and-fro. This occurs in six successive linear excursions, under the influence of electron-induced molecular dissociation at alternate ends of the line…. The result is a rocking motion of atomic F which mirrors, at the molecular scale, the classic to-and-fro rocking of a macroscopic Newton's cradle. Whereas a classic Newton's cradle is excited only once, the molecular analogue [⁴] here is subjected to opposing impulses at successive 'rocks' of the cradle.

The observed multiple knock-on of F-atoms travelling to-and-fro along a 1D row of adsorbates [molecules bound to a substrate] is shown…to be comparable with the synchronous motion of a Newton's cradle."
Leung, Timm & Polanyi, 2021, p.12647-50

Making molecules rock?

'Rocking' refers to a particular kind of motion. In a macroscopic context, there are familiar example of rocking as when a baby is cradled in the arms and gently 'rocked' back and forth.

A rocking chair is designed to enable a rocking motion where the person in the chair moves back and forth through space.

The molecular system described by Leung and colleagues is described as "mirror[ing], at the molecular scale…to-and-fro rocking"

[Image by OpenClipart-Vectors from Pixabay]

The researchers are suggesting that, in some sense, the changes in their molecular scale system are equivalent to "the synchronous motion of a Newton's cradle".

Titles and texts in scientific writing

One feature of interest here is a difference between the way work is described in the article titles and the main texts.

	Chemistry society professional journal	Academic research journal
Title	*"…molecular Newton's cradle"*	*"…an atomic-scale Newton's cradle"*
Text	The effect was "mimicking … a Newton's cradle."	The effect "paralleled… mirrors… [is] comparable with" Newton's cradle

Bold titles: nuanced details

Titles need to capture the reader's attention (and in science today the amount of published material is vastly more than only one person could read) so there is a tendency to be bold. Both these articles have titles suggesting that they are reporting a nanoscopic Newton's cradle. The reader enticed to explore further then discovers that there are caveats. What is being claimed is not a Newton's cradle at minuscule scale but something which though not actually a Newton's cradle, does have some similarity to (mimics, parallels, mirrors) one.

This is important as "the molecular analogue" is only analogous in some respects.

The analogy

There is an analogy, but the analogy can only be drawn so far. In the analogy, the suspended balls of the Newton's cradle are seen as analogous to the 'chemisorbed' molecules lined up on the surface of a copper base.

Analogies are used in teaching and in science communication to help 'make the unfamiliar familiar', to show someone that something they do not (yet) know about is actually, in some sense at least, a bit like something they are already familiar with. In an analogy, there is a mapping between some aspect(s) of the structure of the target ideas and the structure of the familiar phenomenon or idea being offered as an analogue. Such teaching analogies can be useful to the extent that someone is indeed highly familiar with the 'analogue' (and more so than with the target knowledge being communicated); that there is a helpful mapping across between the analogue and the target; and that comparison is clearly explained (making clear which features of the analogue are relevant, and how).

Analogies only map some features from analogue to target. If there was a perfect transfer from one system to the other, then this would not be an analogy at all, but an identity! So, in a sense there are no perfect analogies as that would be an oxymoron. Understanding an analogy as intended therefore means appreciating which features of the analogue do map across to the target, and which do not. Therefore in using analogies in teaching (or communicating science) it is important to be explicit about which features of the analogue map across (the 'positive' analogy) and which do not, including features which it would be misleading to seek to map across – the so called 'negative analogy.' For example, when students think of an atom as a tiny solar system, they may assume that atom, like the solar system, is held together by gravitational force (Taber, 2013).

It probably seems obvious to most science teachers that, if comparing the atom with a solar system, the role that gravity has in binding the solar system maps across to the electrical attraction between a positive nucleus and negative electrons; but when a sample of 14-18 year-olds were asked about atoms and solar systems, a greater number of them suggested the force binding the atom was gravitational than suggested it was electrical (Taber, 2013)!

Perhaps the most significant 'negative analogy' in the research discussed here was pointed out in both the research paper and the subsequent Chemistry World report, and relates to the lack of inherent oscillation in the molecular level system. The nanoscopic system is like a Newton's cradle that only has one swing, so the owner has to reset it each half cycle.

"Unlike a desk Newton's cradle, it did not swing back on its own accord, but another electron impulse could be used to set it off."
"Whereas a classic Newton's cradle is excited only once, the molecular analogue here is subjected to opposing impulses at successive 'rocks' of the cradle"

That is quite a major difference when using the Newton's cradle for an analogy.

Image by Peggy und Marco Lachmann-Anke from Pixabay

Who wants a Newton's cradle as an executive toy if it needs to be manually reset after each swing?

The positive and negative analogies

We can consider that the Newton's cradle is a little like a simple pendulum that swings back and forth, with the complication that instead of a single bob swinging back and forth, the two terminal spheres share the motion between them due to the momentum acquired by one terminal sphere being transferred thorough the intermediate spheres to the other terminal sphere.

In understanding the analogy it is useful to separately consider these two features of a Newton's cradle

a) the transfer of momentum through the sequence
b) moving a mass through a gravitational field

If we then think of the Newton's cradle as a 'pendulum with complications' it seems that the molecular system described by Leung and colleagues fails to share a critical feature of a pendulum.

A chain reaction – the positive analogy

The two systems map well in so far as that they comprise a series of similar units (spheres, molecules) that are carefully aligned, and constrained from moving out of alignment, and that there is a mechanism that allows a kind of chain reaction.

In the molecular scenario, the excitation of a terminal molecule causes a fluorine atom to become unbound from the molecule and to carry enough momentum to collide with and excite a second molecule, binding to it, whilst causing the release of one of the molecule's original fluorine atoms which is similarly ejected with sufficient momentum to collide with the next molecule…

This 'chain reaction' ⁵ is somewhat similar to how, in a Newton's cradle, the momentum of a swinging sphere is transferred to the next, and then to the next, and then the next, until finally all the momentum is transferred to the terminal sphere. (This is an idealised cradle, in any real cradle the transfer will not be 100% perfect.) This happens because the spheres are made from materials which collide 'elastically'.⁶

The positive analogy: The notion of an atomic level Newton's cradle makes use of a similarity between two systems (at very different scales) where features of one system map onto analogous features of the other.

The negative analogy

Given that positive mapping, a key difference here is the way the components of the system (suspended spheres or chemisorbed molecules) are 'tethered'.

Chemisorbed molecules

The molecules are attached to the copper surface by chemical bonding, which is essentially an electromagnetic interaction. A sufficient input of energy could certainly break these bonds, but the the impulse being applied parallel to the metal surface is not sufficient to release the molecules from the substrate. It is enough to eject a fluorine atom from a molecule where carbon is already bound to the surface and three other fluorines atoms (carbon is tetravalent, but it is is bonded to the copper as well as the fluorines) – but the final molecule is an adsorbed CF₂ molecule, which 'captures' the fluorine and becomes an absorbed CF₃ molecule.

Now, energy is always conserved in all interactions, and momentum is also always conserved. If the kinetic energy of the 'captured' fluorine atom does not lead to bond breaking it must end up somewhere else. The momentum from the 'captured' atom must also be transferred somewhere.

Here, it may be useful to think of chemical bonds as having a similarity to springs – in the limited sense that they can be set vibrating. If we imagine a large structure made up of spheres connected by springs, we can see that if we apply a force to one of the spheres, and the force is not enough to break the spring, the sphere will start to oscillate, and move any spheres connected to it (which will move spheres attached to them…). We can imagine the energy from the initial impulse, and transferred through the chain of molecules, is dissipated though the copper lattice, and adds to its internal energy. ⁷

The fluorocarbon molecules are bound to the surface by chemical bonding. If the energy of impact is insufficient to cause bond breaking, it will be dissipated.

Working against gravity

In a simple pendulum, work is done on a raised sphere by the gravitational field, which accelerates the bob when it is released, so that it is moving at maximum speed when it reaches the lowest point. So, as it is moving, it has momentum, and its inertia means it continues to swing past the equilibrium position which is the 'attractor' for the system. In a Newton's cradle the swinging sphere cannot continue when it collides with the next sphere, but as its momentum is transferred through the train of spheres the other terminal sphere swings off, vicariously continuing the motion.

In an ideal pendulum with no energy losses the bob rises to its original altitude (but on the other side of the support) by which time it has no momentum left (as gravitational force has acted downwards on it to reduce its momentum) – but gravitational potential energy has again built up in the system to its original level. So, the bob falls under gravity again, but, being constrained by the wire, does not fall vertically, rather it swings back along the same arc.

It again passes the equilibrium position and returns to the point where it started, and the process is repeated. In an ideal pendulum this periodic oscillation would continue for ever. In a real pendulum there are energy losses, but even so, a suitable bob can swing back an forth for some time, as the amplitude slowly reduces and the bob will eventually stop at the attractor, when the bob is vertical.

In a (real) Newton's cradle, one ball is raised, so increasing the gravitational potential energy of the system (which is the configuration of the cradle, with its spheres, plus the earth). When it is released, gravity acts to cause the ball to fall. It cannot fall vertically as it is tethered by a steel (or similar) wire which is barely extendible, so the net force acting causes the ball to swing though an arc, colliding with the next ball.

The Newton's cradle design allows the balls to change their 'height' in relation to a vertical gravitational field direction – in effect storing energy in a higher gravitational field configuration that can do work to continue the oscillation. The molecular analogue⁴ does not include an equivalent mechanism that can lead to simultaneous oscillation.
(Image by 3D Animation Production Company from Pixabay)

Two types of force interactions

The steel spheres, however, are actually subject to two different kinds of force. They are, like the molecules, also tethered by the electromagnetic force (they are attached to steel wires which are effectively of fixed length due to the bonding in the metal ⁸), but, in addition, subject to the gravitational field of the earth. ⁹ The gravitational field is relevant because a sphere is supported by a wire that is fixed to a rigid support (the cradle) at one end, but free to swing at the end attached to the sphere.

The Newton's cradle operates in what is in effect a uniform gravitational field (neither the radial nature or variation with altitude of the earth's field are relevant on the scale of the cradle) – and the field direction is parallel to the plane in which the balls hang. So, the gravitational potential of the system changes as a sphere swings higher in the field.

In a Newton's cradle, a tethered sphere's kinetic energy allows it to rise in a gravitational field, before swinging back gaining speed (and regaining kinetic energy)

The design of the system is such that a horizontal impulse on a sphere leads to it swinging upwards – and gravity then acts to accelerate it towards a new collision. ¹⁰ This collision, indirectly, gives a horizontal impulse to the sphere at the other end of the 'train' where again the nature of the support means the sphere swings upward – being constrained by both the wire maintaining its distance from the point of suspension at the rigid support of the frame, and its weight acting downwards.

The negative analogy concerns the means of constraining the system components

The two systems then both have a horizontal impulse being transferred successively along a 'train' of units. Leung and colleagues' achievement of this at the molecular scale is impressive.

However, the means of 'tethering' in the two systems is different in two significant ways. The spheres in the Newton's cradle are suspended from a rigid frame by inextensible wires that are free to swing. Moreover, the cradle is positioned in a field with a field direction perpendicular to the direction of the impulse. This combination allows horizontal motion to be converted to vertical motion reversibly.

The molecular system comprises molecules bound to a metal substrate. The chemisorbtion is less like attaching the molecules with long wires that are free to swing, and more like attaching them with short, stiff springs. Moreover, at the scale of the system, the substrate is less like a rigid frame, and more like a highly sprung mattress. So, even though kinetic energy from the 'captured' fluorine atom can be transferred to the bond, this can then be dissipated thorough the lattice.

The negative analogy: the two systems fail to map across in a critical way such that in a Newton's cradle one initial impulse can lead to an extended oscillation, but in the molecular system the initiating energy is dissipated rather than stored to reverse the chemical chain reaction.

The molecular system does not enable the terminal molecule to do work in some form that can be recovered to reverse the initial process. By contrast, a key feature of a Newton's cradle is that the spheres are constrained ('tethered') in a way that allows them to move against the gravitational field – they cannot move further away from, nor nearer to, their point of support, yet they can swing up and down and change their distance from the earth. Mimicking that kind of set-up in a molecular level system would indeed be an impressive piece of nano-engineering!

Work cited:

Blow, M. (2022). Molecular Newton's cradle challenges theory of transition states. Chemistry World, 19(1), 38.
Leung, L., Timm, M. J., & Polanyi, J. C. (2021). Reversible 1D chain-reaction gives rise to an atomic-scale Newton's cradle. Chemical Communications, 57(94), 12647-12650. doi:10.1039/D1CC05378G
Taber, K. S. (2013). Upper Secondary Students' Understanding of the Basic Physical Interactions in Analogous Atomic and Solar Systems. Research in Science Education, 43(4), 1377-1406. doi:10.1007/s11165-012-9312-3 (The author's manuscript version may be downloaded here.)

Notes

¹ Strictly they are no distinct atoms once several atoms have been bound together into a molecule, but chemists tend to talk in a shorthand as if the atoms still existed in the molecules.

² Whilst I expect this is obvious to people who might choose to read this posting, I think it is worth always being explicit about such matters as students may develop alternative conception at odds with scientific accounts.

In the present case, I would be wary of a learner thinking along the lines "of course the atom will go back to its own molecule"

Students will commonly transfer the concepts of 'ownership' and 'belonging' from human social affairs to the molecular level models used in science. Students often give inappropriate status to the history of molecular processes (as if species like electrons recall and care about their pasts). One example was a student who suggested to me that in homolytic bond breaking each atom would get its own electron back – meaning the electrons in the covalent bond would return to their 'own' atoms.

I have also been told that in double decomposition (precipitation) reactions the 'extra' electron in an anion would go back to its own cation in the reagents, before the precipitation process can occur (that is, precipitation was not due to the mutual attraction between ions known to be present in the reaction mixture: they first had to become neutral atoms that could then from an ionic bond by electron transfer!) In ionic bonding it is common for learners to think that an ionic bond can only be formed between ions that have been formed by a (usually fictitious) electron transfer event.

Read about common alternative conceptions of ionic bonding

Read about a classroom resource to diagnose common alternative conceptions (misconceptions) of ionic bonding

Read about a classroom resource to support learning about the reaction mechanism in precipitation reactions

³ I have here represented the same molecules both as atoms linked by bonds (where I am focusing on the transfer of fluorine atoms) and in other diagrams as unitary spheres (where I am focusing on the transfer of energy/momentum). All models and representations used for atoms and molecules are limited and only able to reflect some features of what is being described.

⁴ A note on terminology. An analogy is used to make the unfamiliar familiar by offering a comparison with something assumed to already be familiar to an audience, in this case the molecular system is the intended target, and the (that is, a generic) Newton's cradle is the analogue. However, analogy – as a mapping between systems – is symmetrical so each system can be considered the analogue of the other.

⁵ In some way's Leung's system is more like a free radical reaction than a Newton's cradle. A free radical is an atom (or molecule) with an unpaired electron – such as an unbound fluorine atom!

In a free radical reaction a free radical binds to a molecule and in doing so causes another atom to be ejected from the molecule – as a free radical. That free radical can bind to another molecule, again causing it to generate a new free radical. In principle this process can continue indefinitely, although the free radical could also collide with another free radical instead of a molecule, which terminates the chain reaction.

⁶ The balls need to be (near enough) perfectly elastic for this to work so the total amount of kinetic energy remains constant. Momentum (mv) is always conserved in any collision between balls (or other objects).

If there were two balls, then the first (swinging) sphere would be brought to a stop by the second (stationary) sphere, to which its momentum would be transferred. So, the first ball would stop swinging, but the second would swing in its place. The only way mv and mv² (and so kinetic energy) can be both conserved in collisions between balls of the same mass is if the combination of velocities does not change. That is, mathematically, the only solutions are where neither of the two balls' velocities change, or where they are swapped to the other permutation (here, the velocity of the moving ball becomes zero, but the stationary ball moves off with the velocity that the ball that hit it had approached it with).

The first solution would require the swinging steel ball to pass straight through the stationary steel ball without disturbing it. Presumably, quantum mechanics would suggest that ('tunnelling') option has a non-zero (but tiny, tiny – I mean really tiny) probability. To date, in all known observations of Newton's cradles no one has reported seeing the swinging ball tunnel though the stationary ball. If you are hoping to observe that, then, as they say, please do not hold your breath!

With more balls momentum is transferred through the series: only the final ball is free to move off.

⁷ We can imagine that in an ideal system of a lattice of perfectly rigid spheres attached to perfect springs (i.e., with no hysteresis) and isolated from any other material (n.b., in Leung et al 's apparatus the copper would not have been isolated from other materials), the whole lattice might continue to oscillate indefinitely. In reality the orderliness will decay and the energy will have in effect warmed the metal.

⁸ Strictly, the wires will be longest when the spheres are directly beneath the points of support, as the weight of a sphere slightly extends the wire from its equilibrium length, and it will get slightly shorter the further the sphere swings away from the vertical position. In the vertical position, all the weight is balanced by a tension in the wire. As the ball swings away from the vertical position, the tension in the wire decreases (as only the component of weight acting along the wire needs to be balanced) and an increasing component of the weight acts to decelerate it. But the change in extension of the wire is not significant and is not noticeable to someone watching a Newton's cradle.

When the wire support is not vertical a component of the weight of the sphere acts to change the motion of the sphere

⁹ Molecules are also subject to gravity, but in condensed matter the effect is negligible compared with the very much stronger electromagnetic forces acting.

¹⁰ We might say that gravity decelerates the sphere as is swings upwards and then accelerates as it swings back down. This is true because that description includes a change of reference direction. A scientist might prefer to say that gravity applies a (virtually) constant downward acceleration during the swing. This point is worth making in teaching as a very common alternative conception is to see gravity only really taking effect at the top of the swing.

Cells are buzzing cities that are balloons with harpoons

What can either wander door to door, or rush to respond; and when it arrives might touch, sniff, nip, rear up, stroke, seal, or kill?

Keith S. Taber

a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts

BBC Radio 4's 'Start the week' programme is not a science programme, but tends to invite in guests (often authors of some kind) each week according to some common theme. This week there was a science theme and the episode was titled 'Building the Body, Opening the Heart', and was fascinating. It also offers something of a case study in how science gets communicated in the media.

**Building the Body, Opening the Heart**

The guests all had life-science backgrounds:

Siddhartha Mukherjee is a physician (M.D. from Harvard) and biologist (Stanford, and Oxford {D.Phil.}) – a medical oncologist at Columbia University
Sian Harding is Professor of Cardiac Pharmacology at the National Heart and Lung Institute, Imperial College London, and Director of the Imperial Cardiac Regenerative Medicine Centre
Paul McAuley is best known as a science fiction author (his blog is called 'Earth and other unlikely worlds', but has a background in botany.

Their host was geneticist and broadcaster Adam Rutherford.

Communicating science through the media

As a science educator I listen to science programmes both to enhance and update my own science knowledge and understanding, but also to hear how experts present scientific ideas when communicating to a general audience. Although neither science popularisation nor the work of scientists in communicating to the public is entirely the same as formal teaching (for example,

there is no curriculum with specified target knowledge; and
the audiences
- are not well-defined,
- are usually much more diverse than found in classrooms, and
- are free to leave at any point they lose interest or get a better offer),

they are, like teachers, seeking to inform and explain science.

Science communicators, whether professional journalists or scientists popularising their work, face similar challenges to science teachers in getting across often complex and abstract ideas; and, like them, need to make the unfamiliar familiar. Science teachers are taught about how they need to connect new material with the learners' prior knowledge and experiences if it is to make sense to the students. But successful broadcasters and popularisers also know they need to do this, using such tactics as simplification, modelling, metaphor and simile, analogy, teleology, anthropomorphism and narrative.

Perhaps one of the the biggest differences between science teaching and science communication in the media is the ultimate criterion of success. For science teachers this is (sadly) usually, primarily at least, whether students have understood the material, and will later recall it, sufficiently to demonstrate target knowledge in exams. The teacher may prefer to focus on whether students enjoy science, or develop good attitudes to science, or will consider working in science: but, even so, they are usually held to account for students' performance levels in high-stakes tests.

Science journalists and popularisers do not need to worry about that. Rather, they have to be sufficiently engaging for the audience to feel they are learning something of interest and understanding it. Of course, teachers certainly need to be engaging as well, but they cannot compromise what is taught, and how it is understood, in order to entertain.

With that in mind, I was fascinated at the range of ways the panel of guests communicated the science in this radio show. Much of the programme had a focus on cells – and these were described in a variety of ways.

Talking about cells

Dr Rutherford introduced cells as

"the basic building blocks of life on earth"; and observed that he had
"spent much of my life staring down microscopes at these funny, sort of mundane, unremarkable, gloopy balloons"; before suggesting that cells were
"actually really these incredible cities buzzing with activity".

Dr. Mukherjee noted that

"they're fantastical living machines" [where a cell is the] "smallest unit of life…and these units were built, as it were, part upon part like you would build a Lego kit"

Listeners were told how Robert Hooke named 'cells' after observing cork under the microscope because the material looked like a series of small rooms (like the cells where monks slept in monasteries). Hooke (1665) reported,

"I took a good clear piece of Cork, and with a Pen-knife sharpen'd as keen as a Razor, I cut a piece of it off, and…cut off from the former smooth surface an exceeding thin piece of it, and…I could exceeding plainly perceive it to be all perforated and porous, much like a Honey-comb, but that the pores of it were not regular; yet it was not unlike a Honey-comb in these particulars

…these pores, or cells, were not very deep, but consisted of a great many little Boxes, separated out of one continued long pore, by certain Diaphragms, as is visible by the Figure B, which represents a sight of those pores split the long-ways.
Robert Hooke

Hooke's drawing of the 'pores' or 'cells' in cork

Components of cells

Dr. Mukherjee described how

"In my book I sort of board the cell as though it's a spacecraft, you will see that it's in fact organised into rooms and there are byways and channels and of course all of these organelles which allow it to work."

We were told that "the cell has its own skeleton", and that the organelles included the mitochondria and nuclei ,

"[mitochondria] are the energy producing organelles, they make energy in most cells, our cells for instance, in human cells. In human cells there's a nucleus, which stores DNA, which is where all the genetic information is stored."

A cell that secretes antibodies which are like harpoons or missiles that it sends out to kill a pathogen?

(Images by by envandrare and OpenClipart-Vectors from Pixabay)

Immune cells

Rutherford moved the conversation onto the immune system, prompting 'Sid' that "There's a lovely phrase you use to describe T cells, which is door to door wanderers that can detect even the whiff of an invader". Dr. Mukherjee distinguished between the cells of the innate immune system,

"Those are usually the first responder cells. In humans they would be macrophages, and neutrophils and monocytes among them. These cells usually rush to the site of an injury, or an infection, and they try to kill the pathogen, or seal up the pathogen…"

and the cells of the adaptive system, such as B cells and T cells,

"The B cell is a cell that eventually becomes a plasma cell which secretes antibodies. Antibodies, they are like harpoons or missiles which the cell sends out to kill a pathogen…

[A T cell] goes around sniffing other cells, basically touching them and trying to find out whether they have been altered in some way, particularly if they are carrying inside them a virus or any other kind of pathogen, and if it finds this pathogen or a virus in your body, it is going to go and kill that virus or pathogen"

A cell that goes around sniffing other cells, touching them? ¹
(Images by allinonemovie and OpenClipart-Vectors from Pixabay)

Cells of the heart

Another topic was the work of Professor Harding on the heart. She informed listeners that heart cells did not get replaced very quickly, so that typically when a person dies half of their heart cells had been there since birth! (That was something I had not realised. It is believed that this is related to how heart cells need to pulse in synchrony so that the whole organ functions as an effective pumping device – making long lasting cells that seldom need replacing more important than in many other tissues.)

At least, this relates to the cardiomyocytes – the cells that pulse when the heart beats (a pulse that can now be observed in single cells in vitro). Professor Harding described how in the heart tissue there are also other 'supporting' cells, such as "resident macrophages" (immune cells) as well as other cells moving around the cardiomyocytes. She describe her observations of the cells in Petri dishes,

"When you look at them in the dish it's incredible to see them interact. I've got a… video [of] cardiomyocytes in a dish. The cardiomyocytes pretty much just stay there and beat and don't do anything very much, and I had this on time lapse, and you could see cells moving around them. And so, in one case, the cell (I think it was a fibroblast, it looked like a fibroblast), it came and it palpated at the cardiomyocyte, and it nipped off bits of it, it sampled bits of the cardiomyocyte, and it just stroked it all the way round, and then it was, it seemed to like it a lot.

[In] another dish I had the same sort of cardiomyocyte, a very similar cell came in, it went up to the cardiomyocyte, it touched it, and as soon as it touched it, I can only describe it as it reared up and it had, little blobs appeared all over its surface, and it rushed off, literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off, so what had it found, why did one like it and the other one didn't?"

Making the unfamiliar, familiar

The snippets from the broadcast that I have reported above demonstrate a wide range of ways that the unfamiliar is made familiar by describing it in terms that a listener can relate to through their existing prior knowledge and experience. In these various examples the listener is left to carry across from the analogue features of the familiar (the city, the Lego bricks, human interactions, etc.) those that parallel features of the target concept – the cell. So, for example, the listener is assumed to appreciate that cells, unlike Lego bricks, are not built up through rigid, raised lumps that fit precisely in depressions on the next brick/cell. ²

Analogies with the familiar

Hooke's original label of the cell was based on a kind of analogy – an attempt to compare what we has seeing with something familiar: "pores, or cells…a great many little Boxes". He used the familiar simile of the honeycomb (something directly familiar to many more people in the seventeenth century when food was not subject to large-scale industrialised processing and packaging).

Other analogies, metaphors and similes abound. Cells are visually like "gloopy balloons", but functionally are "building blocks" (strictly a metaphor, albeit one that is used so often it has become treated as though a literal description) which can be conceptualised as being put together "like you would build a Lego kit" (a simile) although they are neither fixed, discrete blocks of a single material, nor organised by some external builder. They can be considered conceptually as the"smallest unit of life"(though philosophers argue about such descriptions and what counts as an individual in living systems).

The machine description ("fantastical living machines") reflects one metaphor very common in early modern science and cells as "incredible cities" is also a metaphor. Whether cells are literally machines is a matter of how we extend or limit our definition of machines: cells are certainly not actually cities, however, and calling them such is a way of drawing attention to the level of activity within each (often, apparently from observation, quite static) cell. B cells secrete antibodies, which the listener is old are like (a simile) harpoons or missiles – weapons.

Skeletons of the dead

Whether "the cell has its own skeleton" is a literal or metaphorical statement is arguable. It surely would have originally been a metaphoric description – there are structures in the cell which can be considered analogous to the skeleton of an organism. If such a metaphor is used widely enough, in time the term's scope expands to include its new use – and it becomes (what is called, metaphorically) a 'dead metaphor'.

Telling stories about cells

A narrative is used to help a listener imagine the cell at the scale of "a spacecraft". This is "organised into rooms and there are byways and channels" offering an analogy for the complex internal structure of a cell. Most people have never actually boarded a spacecraft, but they are ubiquitous in television and movie fiction, so a listener can certainly imagine what this might be like.

Endoplastic reticulum? (Still from **Star Trek: The Motion Picture**, Paramount Pictures, 1979)

Oversimplification?

The discussion of organelles illustrates how simplifications have to be made when introducing complex material. This always brings with it dangers of oversimplification that may impede further learning, or even encourage the development of alternative conceptions. So, the nucleus does not, strictly, 'store' "all the genetic information" in a cell (mitochondria carry their own genes for example).

More seriously, perhaps, mitochondria do not "make energy". 'More seriously' as the principle of conservation of energy is one of the most basic tenets of modern science and is considered a very strong candidate for a universal law. Children are often taught in school that energy cannot be created or destroyed. Science communication which is contrary to this basic curriculum science could confuse learners – or indeed members of the public seeking to understand debates about energy policy and sustainability.

Anthropomorphising cells

Cells are not only compared to inanimate entities like balloons, building bricks, cities and spaceships. They are also described in ways that make them seem like sentient agents – agents that have experiences, and conscious intentions, just as people do. So, some immune cells are metaphorical 'first responders' and just as emergency services workers they "rush to the site" of an incident. To rush is not just to move quickly, buy to deliberately do so. (By contrast, Paul McAuley refers to "innocent" amoeboid cells that collectively form into the plasmodium of a slime mould spending most of their lives"bumbling around by themselves" before they "get together". ) The immune cells act deliberately – they "try" to kill. Other immune cells "send out" metaphorical 'missiles' "to kill a pathogen". Again this language suggests deliberate action (i.e., to send out) and purpose.

That is, what is described is not just some evolved process, but something teleological: there is a purpose to sending out antibodies – it is a deliberate act with an aim in mind. This type of language is very common in biology – even referring to the 'function' of the heart or kidney or a reflex arc could be considered as misinterpreting the outcome of evolutionary developments. (The heart pumps blood through the vascular system, but referring to a function could suggest some sense of deliberate design.)

Not all cells are equal

I wonder how many readers noticed the reference above to 'supporting' cells in the heart. Professor Harding had said

"When you look inside the [heart] tissue there are many other cells [than cardiomyocytes] that are in there, supporting it, there are resident macrophages, I think we still don't know really what they are doing in there"

Why should some heart cells be seen as more important and others less so? Presumably because 'the function' of a heart is to beat, to pump, so clearly the cells that pulse are the stars, and the other cells that may be necessary but are not obviously pulsing just a supporting cast. (So, cardiomyocytes are considered heart cells, but macrophages in the same tissue are only cells that are found in the heart, "residents" – to use an analogy of my own, like migrants that have not been offered citizenship!)³

That is, there is a danger here that this way of thinking could bias research foci leading researchers to ignore something that may ultimately prove important. This is not fanciful, as it has happened before, in the case of the brain:

"Glial cells, consisting of microglia, astrocytes, and oligodendrocyte lineage cells as their major components, constitute a large fraction of the mammalian brain. Originally considered as purely non-functional glue for neurons, decades of research have highlighted the importance as well as further functions of glial cells."
Jäkel and Dimou, 2017

The lives of cells

Narrative is used again in relation to the immune cells: an infection is presented as a kind of emergency event which is addressed by special (human like) workers who protect the body by repelling or neutralising invaders. "Sniffing" is surely an anthropomorphic metaphor, as cells do not actually sniff (they may detect diffusing substances, but do not actively inhale them). Even "touching" is surely an anthropomorphism. When we say two objects are 'touching' we mean they are in contact, as we touch things by contact. But touching is sensing, not simply adjacency.

If that seems to be stretching my argument too far, to refer to immune cells "trying to find out…" is to use language suggesting an epistemic agent that can not only behave deliberately, but which is able to acquire knowledge. A cell can only "find" an infectious agent if it is (i.e., deliberately) looking for something. These metaphors are very effective in building up a narrative for the listener. Such a narrative adopts familiar 'schemata', recognisable patterns – the listener is aware of emergency workers speeding to the scene of an incident and trying to put out a fire or seeking to diagnose a medical issue. By fitting new information into a pattern that is familiar to the audience, technical and abstract ideas are not only made easier to understand, but more likely to be recalled later.

Again, an anthropomorphic narrative is used to describe interactions between heart cells. So, a fibroblast that "palpates at" a cardiomyocyte seems to be displaying deliberate behaviour: if "nipping" might be heard as some kind of automatic action – "sampling" and "stroking" surely seem to be deliberate behaviour. A cell that "came in, it went up [to another]" seems to be acting deliberately. "Rearing up" certainly brings to mind a sentient being, like a dog or a horse. Did the cell actually 'rear up'? It clearly gave that impression to Professor Harding – that was the best way, indeed the "only" way, she had to communicate what she saw.

Again we have cells "rushing" around. Or do we? The cell that had reared up, "rushed off". Actually, it appeared to "rush" when the highly magnified footage was played at 720 times the speed of the actual events. Despite acknowledging this extreme acceleration of the activity, the impression was so strong that Professor Harding felt justified in claiming the cell "literally rushed off, although it was time lapse so it was two minutes over 24 hours, so, it literally rushed off…". Whatever it did, that looked like rushing with the distortion of time-lapse viewing, it certainly did not literally rush anywhere.

But the narrative helps motivate a very interesting question, which is why the two superficially similar cells 'behaved' ('reacted', 'responded' – it is actually difficult to find completely neutral language) so differently when in contact with a cardiomyocyte. In more anthropomorphic terms: what had these cells "found, why did one like it and the other one didn't?"

Literally speaking?

Metaphorical language is ubiquitous as we have to build all our abstract ideas (and science has plenty of those) in terms of what we can experience and make sense of. This is an iterative process. We start with what is immediately available in experience, extend metaphorically to form new concepts, and in time, once those have "settled in" and "taken root" and "firmed up" (so to speak!) they can then be themselves borrowed as the foundation for new concepts. This is true both in how the individual learns (according to constructivism) and how humanity has developed culture and extended language.

So, should science communicators (whether scientists themselves, journalists or teachers) try to limit themselves to literal language?

Even if this were possible, it would put aside some of our strongest tools for 'making the unfamiliar familiar' (to broadcast audiences, to the public, to learners in formal education). However these devices also bring risks that the initial presentations (with their simplifications and metaphors and analogies and anthropomorphic narratives…) not only engage listeners but can also come to be understood as the scientific account. That is is not an imagined risk is shown by the vast numbers of learners who think atoms want to fill their shells with octets of electrons, and so act accordingly – and think this because they believe it is what they have been taught.

Does it matter if listeners think the simplification, the analogy, the metaphor, the humanising story,… is the scientific account? Perhaps usually not in the case of the audience listening to a radio show or watching a documentary out of interest.

In education it does matter, as often learners are often expected to progress beyond these introductory accounts in their thinking, and teachers' models and metaphors and stories are only meant as a starting point in building up a formal understanding. The teacher has to first establish some kind of anchor point in the students' existing understandings and experiences, but then mould this towards the target knowledge set out in the curriculum (which is often a simplified account of canonical knowledge) before the metaphor or image or story becomes firmed-up in the learners' minds as 'the' scientific account.

'Building the Body, Opening the Heart' was a good listen, and a very informative and entertaining episode that covered a lot of ideas. It certainly included some good comparisons that science teachers might borrow. But I think in a formal educational context a science teacher would need to be more circumspect in throwing some of these metaphors out there, without then doing some work to transition from them to more technical, literal, and canonical accounts.

Read about science analogies

Read about science metaphors

Read about science similes

Read about anthropomorphism

Read about teleology

Work cited:

Hooke, R. (1665). Micrographia.
Jäkel S and Dimou L (2017) Glial Cells and Their Function in the Adult Brain: A Journey through the History of Their Ablation. Frontiers in Cellullar Neuroscience, 11:24. doi: 10.3389/fncel.2017.00024
Taber, K. S. (2013). Upper Secondary Students' Understanding of the Basic Physical Interactions in Analogous Atomic and Solar Systems. Research in Science Education, 43(4), 1377-1406. doi:10.1007/s11165-012-9312-3

Notes:

¹ The right hand image portrays a mine, a weapon that is used at sea to damage and destroy (surface or submarine) boats. The mine is also triggered by contact ('touch').

² That is, in an analogy there are positive and negative aspects: there are ways in which the analogue IS like the target, and ways in which the analogue is NOT like the target. Using an analogy in communication relies on the right features being mapped from the familiar analogue to the unfamiliar target being introduced. In teaching it is important to be explicit about this, or inappropriate transfers may be made: e.g., the atom is a tiny solar system so it is held together by gravity (Taber, 2013).

³ It may be a pure coincidence in relation to the choice of term 'resident' here, but in medicine 'residents' have not yet fully qualified as specialist physicians or surgeons, and so are on placement and/or under supervision, rather than having permanent status in a hospital faculty.

The missing mass of the electron

Annihilating mass in communicating science

Keith S. Taber

An episode of 'In Our Time' about the electron

The BBC radio programme 'In Our Time' today tackled the electron. As part of the exploration there was the introduction of the positron, and the notion of matter-antimatter annihilation. These are quite brave topics to introduce in a programme with a diverse general audience (last week Melvyn Bragg and his guests discussed Plato's Atlantis and next week the programme theme is the Knights Templar).

Prof. Victoria Martin of the School of Physics and Astronomy at the University of Edinburgh explained:

If we take a pair of matter and antimatter, so, since we are talking about the electron today, if we take an electron and the positron, and you put them together, they would annihilate.
And they would annihilate not into nothingness, because they both had mass, so they both had energy from E=mc² that tells us if you have mass you have energy. So, they would annihilate into energy, but it would not just be any kind of energy: the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light. And it will have a very specific amount of energy. Its energy will be equal to the sum of the energy of electron and the positron that they had initially when they collided together.
Prof. Victoria Martin on 'In Our Time'

"*An electron and the positron, and you put them together, they would annihilate…they would annihilate into energy*" – but this could be misleading.

Now, I am sure that is somewhat different from how Prof. Martin would treat this topic with university physics students – of course, science in the media has to be pitched at the largely non-specialist audience.

Read about science in the media

It struck me that this presentation had the potential to reinforce a common alternative conception ('misconception') that mass is converted into energy in certain processes. Although I am aware now that this is an alternative conception, I seem to recall that is pretty much what I had once understood from things I had read and heard.

It was only when I came to prepare to teach the topic that I realised that I had a misunderstanding. That, I think, is quite common for teachers – when we have to prepare a topic well enough to explain it to others, we may spot flaws in our own understanding (Taber, 2009)

So, for example, I had thought that in nuclear processes, such as in a fission reactor or fusion in stars, the mass defect (the apparent loss of mass as the resulting nuclear fragments have less mass than those present before the process) was due to that amount of mass being converted to energy. This is sometimes said to explain why nuclear explosions are so much more violent than chemical explosions, as (given E=mc²): a tiny amount of mass can be changed into a great deal of energy.

Prof. Martin's explanation seemed to support this way of thinking: "they would annihilate into energy".

An alternative conception of particle annihilation: This scheme seems to be implied by Prof. Martin's comments

What is conserved?

It is sometimes suggested that, classically, mass and energy were considered to be separately conserved in processes, but since Einstein's theories of relativity have been adopted, now it is considered that mass can be considered as if a form of energy such that what is conserved is a kind of hybrid conglomerate. That is, energy is still considered conserved, but only when we account for mass that may have been inter-converted with energy. (Please note, this is not quite right – see below.)

So, according to this (mis)conception: in the case of an electron-positron annihilation, the mass of the two particles is converted to an equivalent energy – the mass of the electron and the mass of the positron disappear from the universe and an equivalent quantity of energy is created. Although energy is created, energy is still conserved if we allow for the mass that was converted into this new energy. Each time an electron and positron annihilate, their masses of about 2 ✕ 10^-30 kg disappear from the universe and in its place something like 2 ✕ 10^-13 J appears instead – but that's okay as we can consider 2 ✕ 10^-30 kg as a potential form of energy worth 2 ✕ 10^-13 J.

However, this is contrary to what Einstein (1917/2004) actually suggested.

Einstein did not suggest that matter could be changed to energy

Equivalence, not interconversion

What Einstein actually suggested was not that mass could be considered as if another kind/form of energy (alongside kinetic energy and gravitational potential, etc.) that needed to be taken into account in considering energy conservation, but rather that inertial mass can be considered as an (independent) measure of energy.

That is, we think energy is always conserved. And we think that mass is always conserved. And in a sense they are two measures of the same thing. We might see these two statements as having redundancy:

In a isolated system we will always have the same total quantity of energy before and after any process.
In a isolated system we will always have the same total quantity of mass before and after any process.

As mass is always associated with energy, and so vice versa, either of these statements implies the other. ¹

Two conceptions of the shift from a Newtonian to a relativistic view of the conservation of energy (move the slider to change the image)

No interconversion?

So, mass cannot be changed into energy, nor vice versa. The sense in which we can 'interconvert' is that we can always calculate the energy equivalence of a certain mass (E=mc²) or mass equivalence of some quantity of energy (m=E/c²).

So, the 'interconversion' is more like a change of units than a change of entity.

Although we might think of kinetic energy being converted to potential energy reflects a natural process (something changes), we know that changing joules to electron-volts is merely use of a different unit (nothing changes).

If we think of a simple pendulum under ideal conditions ² it could oscillate for ever, with the total energy unchanged, but with the kinetic energy being converted to potential energy – which is then converted back to kinetic energy – and so on, ad infinitum. The total energy would be fixed although the amount of kinetic energy and the amount of potential energy would be constantly changing. We could calculate the energy in joules or some other unit such as eV or ergs (or calories or kWh or…). We could convert from one unit to another, but this would not change anything about the physical system. (So, this is less like converting pounds to dollars, and more like converting an amount reported in pounds {e.g., £24.83} into an amount reported in pence {e.g., 2483p}.)

Using this analogy, the electron and positron being converted to a photon is somewhat like kinetic energy changing to potential energy in a swinging pendulum (something changes), but it is not the case that mass is changed into energy. Rather we can do our calculations in terms of energy or mass and will get (effectively, given E=mc²) the same answer (just as we can add up a shopping list in pounds or pence, and get the same outcome given the conversion factor, 1.00£ = 100p).

So, where does the mass go?

If mass is conserved, then where does the mass defect – the amount by which the sum of masses of daughter particles is less than the mass of the parent particle(s) – in nuclear processes go? And, more pertinent to the present example, what happens to the mass of the electron and positron when they mutually annihilate?

To understand this, it might help to bear in mind that in principle these process are like any other natural processes – such as the swinging pendulum, or a weight being lifted with pulley, or methane being combusted in a Bunsen burner, or heating water in a kettle, or photosynthesis, or a braking cycle coming to a halt with the aid of friction.

In any natural process (we currently believe)

the total mass of the universe is unchanged…
- but mass may be reconfigured
the total energy of the universe is unchanged…
- but energy may be reconfigured; and
as mass and energy are associated, any reconfigurations of mass and energy are directly correlated.

So, in any change that involves energy transfers, there is an associated mass transfer (albeit usually one too small to notice or easily measure). We can, for example, calculate the (tiny) increase in mass due to water being heated in a kettle – and know just as the energy involved in heating the water came from somewhere else, there is an equivalent (tiny) decrease of mass somewhere else in the wider system (perhaps due to falling of water powering a hydroelectric power station). If we are boiling water to make a cup of tea, we may well be talking about a change in mass of the order of only 0.000 000 001 g according to my calculations for another posting.

Read 'How much damage can eight neutrons do? Scientific literacy and desk accessories in science fiction.'

The annihilation of the electron and positron is no different: there may be reconfigurations in the arrangement of mass and energy in the universe, but mass (and so energy) is conserved.

So, the question is, if the electron and positron, both massive particles (in the physics sense, that they have some mass) are annihilated, then where does their mass go if it is conserved? The answer is reflected in Prof. Martin's statement that "the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light". The mass is carried away by the photon.

The mass of a massless particle?

This may seem odd to those who have learnt that, unlike the electron and positron, the photon is massless. Strictly the photon has no rest mass, whereas the electron and positron do have rest mass – that is, they have inertial mass even when judged by an observer at rest in relation to them.

So, the photon only has 'no mass' when it is observed to be stationary – which nicely brings us back to Einstein who noted that electromagnetic radiation such as light could never appear to be at rest compared to the observer, as its very nature as a progressive electromagnetic wave would cease if one could travel alongside it at the same velocity. This led Einstein to conclude that the speed of light in any given medium was invariant (always the same for any observer), leading to his theory of special relativity.

So, a photon (despite having no 'rest' mass) not only carries energy, but also the associated mass.

Although we might think in terms of two particles being converted to a certain amount of energy as Prof. Martin suggests, this is slightly distorted thinking: the particles are converted to a different particle which now 'has' the mass from both, and so will also 'have' the energy associated with that amount of mass.

Mass is conserved during the electron-positron annihilation

A slight complication is that the electron and position are in relative motion when they annihilate, so there is some kinetic energy involved as well as the energy associated with their rest masses. But this does not change the logic of the general scheme. Just as there is an energy associated with the particles' rest masses, there is a mass component associated with their kinetic energy.

The total mass-energy equivalence before the annihilation has to include both the particle rest masses and their kinetic energy. The mass-energy equivalence afterwards (being conserved in any process) also reflects this. The energy of the photon (and the frequency of the radiation) reflects both the particle masses and their kinetic energies at the moment of the annihilation. The mass (being perfectly correlated with energy) carried away by the photon also reflects both the particle masses and their kinetic energies.

How could 'In Our Time' have improved the presentation?

It is easy to be critical of people doing their best to simplify complex topics. Any teacher knows that well-planned explanations can fail to get across key ideas as one is always reliant on what the audience already understands and thinks. Learners interpret what they hear and read in terms of their current 'interpretive resources' and habits of thinking.

Read about constructivism

A physicist or physics student hearing the episode would likely interpret Prof. Martin's statement within a canonical conceptual framework. However, someone holding the 'misconception' that mass is converted to energy in nuclear processes would likely interpret "they would annihilate into energy" as fitting, and reinforcing, that alternative conception.

I think a key issue here is a slippage that apparently refers to energy being formed in the annihilation, rather than radiation: (i.e., Prof. Martin could have said "they would annihilate into [radiation]"). When the positron and electron 'become' a photon, matter is changed to radiation – but it is not changed to energy, as matter has mass, and (as mass and energy have an equivalence) the energy is already there in the system.

Energy is reconfigured, but is not formed, in the annihilation process.

So, this whole essay is simply suggesting that a change of one word – from energy to radiation – could potentially avoid the formation of, or the reinforcing of, the alternative conception that mass is changed into energy in processes studied in particle physics. As experienced science teachers will know, sometimes such small shifts can make a good deal of difference to how we are interpreted and, so, what comes to be understood.

Addenda:

Reply from Prof. Victoria Martin on twitter (@MamaPhysikerin), September 30:

"E² = p²c² + m²c⁴ is a better way to relate energy, mass and momentum. Works for both massive and massless states."
@MamaPhysikerin

Work cited:

Einstein, A. (1917/2004). Relativity. The special and the general theory. (R. W. Lawson, Trans.). The Folio Society.
Taber, K. S. (2009). Learning from experience and teaching by example: reflecting upon personal learning experience to inform teaching practice. Journal of Cambridge Studies, 4(1), 82-91.

Notes

¹ In what is often called a closed system there is no mass entering or leaving the system. However, energy can transfer to, or from, the system from its surroundings. Classically it might be assumed that the mass of a closed system is constant as the amount of matter is fixed, but Einstein realised that if there is a net energy influx to, or outflow from, the system, than some mass would also be transferred – even though no matter enters or leaves.

² Perhaps in a uniform gravitational field, not subject to to any frictional forces, with an inextensible string supporting the bob, and in thermal equilibrium with its environment.

The earth's one long-term objective

Scientist reveals what the earth has been trying to do

Keith S. Taber

Seismology – the study of the earth letting off steam? (Image by ELG21 from Pixabay)

"the earth has one objective, it has had one objective for four and half billion years, and that's…"

In our time

'In Our Time' is an often fascinating radio programme (and podcast) where Melvyn Bragg gets three scholars from a field to explain some topic to a general audience.

Imagine young Melvyn interrupting a physics teacher's careful exposition of why pV = ¹/₃nmc² by asking how the gas molecules came to be moving in the first place.

The programme covers various aspects of culture.

I am not sure if the reason that I sometimes find the science episodes seem a little less erudite than those in the the other categories is:

a) Melvyn is more of an arts person, so operates at a different level in different topics;
b) I am more of a science person, so more likely to be impressed by learning new things in non-science topics; and to spot simplifications, over-generalisations, and so forth, in science topics.
c) A focus in recent years on the importance of the public understanding of science and science communication means that scientists may (often, not always) be better prepared and skilled at pitching difficult topics for a general audience.
d) Topics from subjects like history and literature are easier to talk about to a general audience than many science topics which are often highly conceptual and technical.

Anyway, today I did learn something from the episode on seismology ("Melvyn Bragg and guests discuss how the study of earthquakes helps reveal Earth's secrets [sic]"). I was told what the earth had been up to for the last four and half billion years…

Seismology: Where does this energy come from?

Quite early in the discussion Melvyn (sorry, The Lord Bragg CH – but he is so familiar from his broadcasts over the years that he seems like an old friend) interjected when Dr James Hammond (Reader in Geophysics at Birkbeck, University of London) was talking about forces involved in plate tectonics to ask "Where does this energy come from?". To this, Dr Hammond replied,

"The whole thing that drives the whole caboose?
It comes from plate tectonics. So, essentially the earth has one objective, it has had one objective for four and half billion years, and that's to cool down. We're [on] a big lump of rock floating in space, and it's got all this primordial energy, so we are going right back here, there's all this primordial energy from the the material coming together, and it's trying to cool down."
Dr James Hammond talking on 'In Our Time' ¹

My immediate response, was that this was teleology – seeing purpose in nature. But actually, this might be better described as anthropomorphism. This explanation presents the earth as being the kind of agent that has an objective, and which can act in the world to work towards goals. That is, like a human:

The earth has an objective.
The earth tries to achieve its objective.

Read about teleology

Read about anthropomorphism

A flawed scientific account?

Of course, in scientific terms, the earth has no such objective, and it is not trying to do anything as it is inanimate. Basic thermodynamics suggests that an object (e.g., the earth) that is hotter than its surroundings will cool down as it will radiate heat faster than it absorbs it. ² (Of course, the sun is hotter than the earth – but that's a rather minority component of the earth's surroundings, even if in some ways a very significant one.) Hot objects tend to cool down, unless they have an active mechanism to maintain their temperature above their ambient backgrounds (such as 'warm-blooded' creatures). ³

So, in scientific terms, this explanation might be seen as flawed – indeed as reflecting an alternative conception of similar kind as when students explain evolutionary adaptations in terms of organisms trying to meet some need (e.g., The brain thinks: grow more fur), or explain chemical processes in terms of atoms seeking to meet a need by filling their electron shells (e.g., Chlorine atoms share electrons to fill in their shells).

Does Dr Hammond really believe this account?

Does Dr Hammond really think the earth has an objective that it actively seeks to meet? I very much doubt it. This was clearly rhetorical language adopting tropes seen as appropriate to meet the needs of the context (a general audience, a radio programme with no visuals to support explanations). In particular, he was in full flow when he was suddenly interrupted by Melvin, a bit like the annoying child who interrupts the teacher's carefully prepared presentation by asking 'but why's that?' about something it had been assumed all present would take for granted.

Imagine the biology teacher trying to discuss cellular metabolism when young Melvin asks 'but where did the sugar come from?'; or the chemistry teacher discussing the mechanism of a substitution reaction when young Melvin asks why we are assuming tetrahedral geometry around the carbon centre of interest; or young Melvyn interrupting a physics teacher's careful exposition of why pV = ¹/₃nmc² by asking how the gas molecules came to be moving in the first place.

Of course, part of Melvin's job in chairing the programme IS to act as the child who does not understand something being taken for granted and not explained, so vicariously supporting the listener without specialist background in that week's topic.

Effective communication versus accurate communication?

Science teachers and communicators have to sometimes use ploys to 'make the unfamiliar familiar'. One common ploy is to employ an anthropomorphic narrative as people readily relate to the human experience of having goals and acting to meet needs and desires. Locating difficult ideas within such a 'story' framework is known to often make such ideas more accessible. Does this gain balance the potential to mislead people into thinking they have been given a scientific account? In general, such ploys are perhaps best used only as introductions to a difficult topic, introductions which are then quickly followed up by more technical accounts that better match the scientific narrative (Taber & Watts, 2000).

Clearly, that is more feasible when the teacher or communicator has the opportunity for a more extensive engagement with an audience, so that understanding can be built up and developed over time. I imagine Dr Hammond was briefed that he had just a few minutes to get across his specific points in this phase of the programme, only to then find he was interrupted and asked to address additional background material.

As a scientist, the notion of the earth spending billions of years trying to cool down grates as it reflects pre-scientific thinking about nature and acts as a pseudo-explanation (something which has the form of an explanation, but little substance).

Read about pseudo-explanations

As cooling is a very familiar everyday phenomena, I wondered if a basic response that would avoid anthropomorphism might have served, e.g.,

When the earth formed, it was very much hotter than today, and, as it was hotter than its surroundings, it has been slowly cooling ever since by radiating energy into space. Material inside the earth may be hot enough to be liquid, or – where solid – be plastic enough to be deformed. The surface is now much cooler than it was, but inside the earth it is still very hot, and radioactive processes continue to heat materials inside the earth. We can understand seismic events as driven by the ways heat is being transferred from deep inside the earth.

However, just because I am a scientist, I am also less well-placed to know how effective this might have been for listeners without a strong science background – who may well have warmed [sic] to the earth striving to cool.

Dr Hammond had to react instantly (like a school teacher often has to) and make a quick call based on his best understanding of the likely audience. That is one of the difference between teaching (or being interviewed by Melvin) and simply giving a prepared lecture.

Work cited:

Taber, K. S. and Watts, M. (1996) The secret life of the chemical bond: students' anthropomorphic and animistic references to bonding, International Journal of Science Education, 18 (5), pp.557-568.

Note

¹ Speech often naturally has repetitions, and markers of emphasis, and hesitations that seem perfectly natural when heard, but which do not match written language conventions. I have slightly tidied what I transcribed from:

"The whole thing that drives the whole caboose? It comes from plate tectonics, right. So, essentially the earth, right, has one objective, it has had one objective for four and half billion years, and that's to cool down. Right, we're a big lump of rock floating in space, and it's got all this primordial energy, so we are going right back here, there's all this primordial energy from, from the the material coming together,⁴ and it's trying to cool down."

² In simple terms, the hotter an object is, the greater the rate at which it radiates.

The hotter the environment is, the more intense the radiation incident on the object and the more energy it will absorb.

Ultimately, in an undisturbed, closed system everything will reach thermal equilibrium (the same temperature). Our object still radiates energy, but at the same rate as it absorbs it from the environment so there is no net heat flow.

³ Historically, the earth's cooling was an issue of some scientific controversy, after Lord Kelvin (William Thomson) calculated that if the earth was cooling at the rate his models suggested for a body of its mass, then this was cooling much too rapid for the kind of timescales that were thought to be needed for life to have evolved on earth.

⁴ This is referring to the idea that the earth was formed by the coming together of material (e.g., space debris from a supernova) by its mutual gravitational attraction. Before this happens the material can be considered to be in a state of high gravitational potential energy. As the material is accelerated together it acquires kinetic energy (as the potential energy reduces), and then when the material collides inelastically it forms a large mass of material with high internal energy (relating to the kinetic and potential energy of the molecules and ions at the submicroscopic level) reflected in a high temperature.

Climate change – either it is certain OR it is science

Is there a place for absolute certainty in science communication?

Keith S. Taber

I just got around to listening to the podcast of the 10th October episode of Science in Action. This was an episode entitled 'Youngest rock samples from the moon' which led with a story about rock samples collected on the moon and brought to earth by a Chinese mission (Chang'e-5). However, what caused me to, metaphorically at least, prick up my ears was a reference to "absolute certainty".

BBC Science in Action episode, 10th October, 2021

Now the tag line for Science in Action is "The BBC brings you all the week's science news". I think that phrase reveals something important about science journalism – it may be about science, but it is journalism, not science.

That is not meant as some kind of insult. But science in the media is not intended as science communication between scientists (they have journals and conferences and so forth), but science communicated to the public – which means it has to be represented in a form suitable for a general, non-specialist audience.

Read about s cience in public discourse and the media

Scientific and journalistic language games

For, surely, "all the week's science news" cannot be covered in one half-hour broadcast/podcast. ¹

My point is that "The BBC brings you all the week's science news" is not intended to be understood and treated as a scientific claim, but as something rathere different. As Wittgenstein (1953/2009) famously pointed out, language has to be understood in specific contexts, and there are different 'language games'. So, in the genre of the scientific report there are particular standards and norms that apply to the claims made. Occasionally these norms are deliberately broken – perhaps a claim is made that is supported by fabricated evidence, or for which there is no supporting evidence – but this would be judged as malpractice, academic misconduct or at least incompetence. It is not within the rules of that game

However, the BBC's claim is part of a different 'language game' – no one is going to be accused of professional misconduct because, objectively, Science in Action does not brings a listener all the week's science news. The statement is not intended to be understood as an objective knowledge claim, but more a kind of motto or slogan; it is not to be considered 'false' because it not objectively correct. Rather, it is to be understood in a fuzzy, vague, impressionistic way.

To ask whether "The BBC brings you all the week's science news" through Science in Action is a true or false claim would be a kind of category error. The same kind of category error that occurs if we ask whether or not a scientist believes in the ideal gas law, the periodic table or models of climate change.

Who invented gravity?

This then raises the question of how we understand what professional academic scientists say on a science news programme that is part of the broadcast media in conversation with professional journalists. Are they, as scientists, engaged in 'science speak', or are they as guests on a news show engaged in 'media speak'?

What provoked this thought with was comments by Dr Fredi Otto who appeared on the programme "to discuss the 2021 Nobel Prizes for Science". In particular, I was struck by two specific comments. The second was:

"…you can't believe in climate change or not, that would just be, you believe in gravity, or not…"
Dr Friederike Otto speaking on Science in Action

Which I took to mean that gravity is so much part of our everyday experience that it is taken-for-granted, and it would be bizarre to have a debate on whether it exists. There are phenomena we all experience all the time that we explain in terms of gravity, and although there may be scope for debate about gravity's nature or its mode of action or even its universality, there is little sense in denying gravity. ²

Newton's notion of gravity predominated for a couple of centuries, but when Einstein proposed a completely different understanding, this did not in any sense undermine the common ('life-world' ²) experience labelled as gravity – what happens when we trip over, or drop something, or the tiring experience of climbing too many steps. And, of course, the common misconception that Newton somehow 'discovered' gravity is completely ahistorical as people had been dropping things and tripping over and noticing that fruit falls from trees for a very long time before Newton posited that the moon was in freefall around the earth in a way analogous to a falling apple!

Believing in gravity

Even if, in scientific terms, believing in a Newtonian conceptualisation of gravity as a force acting at a distance would be to believe something that was no longer considered the best scientific account (in a sense the 'force' of gravity becomes a kind of epiphenomenon in a relativistic account of gravity); in everyday day terms, believing in the phenomenon of gravity (as a way of describing a common pattern in experience of being in the world) is just plain common sense.

Dr Otto seemed to be suggesting that just as gravity is a phenomenon that we all take for granted (regardless of how it is operationalised or explained scientifically), so should climate change be. That might be something of a stretch as the phenomena we associate with gravity (e.g., dense objects falling when dropped, ending up on the floor when we fall) are more uniform than those associated with climate change – which is of course why one tends to come across more climate change deniers than gravity deniers. To the best of my knowledge, not even Donald Trump has claimed there is no gravity.

But the first comment that gave me pause for thought was:

"…we now can attribute, with absolute certainty, the increase in global mean temperature to the increase in greenhouse gases because our burning of fossil fuels…"
Dr Friederike Otto speaking on Science in Action

Dr Fredi Otto has a profile page at the *The Environmental Change Unit*,
*University of Oxford*

Absolute certainty?

That did not seem to me like a scientific statement – more like the kind of commitment associated with belief in a religious doctrine. Science produces conjectural, theoretical knowledge, but not absolute knowledge?

Surely, absolute certainty is limited to deductive logic, where proofs are possible (as in mathematics, where conclusions can be shown to inevitably follow from statements taken as axioms – as long as one accepts the axioms, then the conclusions must follow). Science deals with evidence, but not proof, and is always open to being revisited in the light of new evidence or new ways of thinking about things.

Read about the nature of scientific knowledge

Science is not about belief

For example, at one time many scientists would have said that the presence of an ether ³ was beyond question (as for example waves of light travelled from the sun to earth, and waves motion requires a medium). Its scientific characterisation -e.g., the precise nature of the ether, its motion relative to the earth – were open to investigation, but its existence seemed pretty secure.

It seemed inconceivable to many that the ether might not exist. We might say it was beyond reasonable doubt. ⁴ But now the ether has gone the way of caloric and phlogiston and N-rays and cold fusion and the four humours… It may have once been beyond reasonable doubt to some (given the state of the evidence and the available theoretical perspectives), but it can never have been 'absolutely certain'.

To suggest something is certain may open us to look foolish later: as when Wittgenstein himself suggested that we could be certain that "our whole system of physics forbids us to believe" that people could go to the moon.

Science is the best!

Science is the most reliable and trustworthy approach to understanding the natural world, but a large part of that strength comes from it never completely closing a case for good – from never suggesting to have provided absolute certainty. Science can be self-correcting because no scientific idea is 'beyond question'. That is not to say that we abandon, say, conversation of energy at the suggestion of the first eccentric thinker with designs for a perpetual motion machine – but in principle even the principle of conservation of energy should not be considered as absolutely certain. That would be religious faith, not scientific judgement.

So, we should not believe. It should not be considered absolutely certain that "the increase in global mean temperature [is due to] the increase in greenhouse gases because [of] our burning of fossil fuels", as that suggests we should believe it as a doctrine or dogma, rather than believe that the case is strong enough to make acting accordingly sensible. That is, if science is always provisional, technically open to review, then we can never wait for absolute certainty before we act, especially when something seems beyond reasonable doubt.

You should not believe scientific ideas

The point is that certainty and belief are not really the right concepts in science, and we should avoid them in teaching science:

"In brief, the argument to be made is that science education should aim for understanding of scientific ideas, but not for belief in those ideas. To be clear, the argument is not just that science education should not intend to bring about belief in scientific ideas, but rather that good science teaching discourages belief in the scientific ideas being taught."
Taber, 2017: 82

To be clear – to say that we do not want learners to believe in scientific ideas is NOT to say we want them to disbelieve them! Rather, belief/disbelief should be orthogonal to the focus on understanding ideas and their evidence base.

I suggested above that to ask whether "The BBC brings you all the week's science news" through Science in Action is a true or false claim would be a kind of category error. I would suggest it is a category error in the same sense as asking whether or not people should believe in the ideal gas law, the periodic table, or models of climate change.

"If science is not about belief, then having learners come out of science lessons believing in evolution, or for that matter believing that magnetic field lines are more concentrated near the poles of a magnet, or believing that energy is always conserved, or believing that acidic solutions contain solvated hydrogen ions,^[5] misses the point. Science education should help students understand scientific ideas, and appreciate why these ideas are found useful, and something of their status (for example when they have a limited range of application). Once students can understand the scientific ideas then they become available as possible ways of thinking about the world, and perhaps as notions under current consideration as useful (but not final) accounts of how the world is."
Taber, 2017: 90

But how do scientists cross the borders from science to science communication?

Of course many scientists who have studied the topic are very convinced that climate change is occurring and that anthropogenic inputs into the atmosphere are a major or the major cause. In an everyday sense, they believe this (and as they have persuaded me, so do I). But in a strictly logical sense they cannot be absolutely certain. And they can never be absolutely certain. And therefore we need to act now, and not wait for certainty.

I do not know if Dr Otto would refer to 'absolute certainty' in a scientific context such as a research paper of a conference presentation. But a radio programme for a general audience – all ages, all levels of technical background, all degrees of sophistication in appreciating the nature of science – is not a professional scientific context, so perhaps a different language game applies. Perhaps scientists have to translate their message into a different kind of discourse to get their ideas across to the wider public?

The double bind

My reaction to Dr Otto's comments derived from a concern with public understanding of the nature of science. Too often learners think scientific models and theories are meant to be realistic absolute descriptions of nature. Too often they think science readily refutes false ideas and proves the true ones. Scientists talking in public about belief and absolute certainty can reinforce these misconceptions.

On the other hand, there is probably nothing more important that science can achieve today than persuade people to act to limit climate change before we might bring about shifts that are (for humanity if not for the planet) devastating. If most people think that science is about producing absolute certain knowledge, then any suggestion that there is uncertainty over whether human activity is causing climate change is likely to offer the deniers grist, and encourage a dangerous 'well let's wait till we know for sure' posture. Even when it is too late and the damage has been done, if there are any scientists left alive, they still will not know absolutely certainly what caused the changes.

"…Lord, here comes the flood
We'll say goodbye to flesh and blood
If again the seas are silent
In any still alive
It'll be those who gave their island to survive…"

(Peter Gabriel performing on the Kate Bush TV special, 1979: BBC Birmingham)

So, perhaps climate scientists are in a double bind – they can represent the nature of science authentically, and have their scientific claims misunderstood; or they can do what they can to get across the critical significance of their science, but in doing so reinforce misconceptions of the nature of scientific knowledge.

Coda

I started drafting this yesterday: Thursday. By coincidence, this morning, I heard an excellent example of how a heavyweight broadcast journalist tried to downplay a scientific claim because it was couched as not being absolutely certain!

Works cited:

Wittgenstein, L. (1953/2009). Philosophical Investigations (G. E. M. Anscombe, P. M. S. Hacker, & J. Schulte, Trans. P. M. S. Hacker & J. Schulte Eds. Revised fourth ed.). Chichester, West Sussex: Wiley-Blackwell.
Schutz, A., & Luckmann, T. (1973). The Structures of the Life-World (R. M. Zaner & H. T. Engelhardt, Trans.). Evanston, Illinois: Northwest University Press.
Taber, K. S. (2013). Classroom-based Research and Evidence-based Practice: An introduction (2nd ed.). London: Sage.
Taber, K. S. (2017). Knowledge, beliefs and pedagogy: how the nature of science should inform the aims of science education (and not just when teaching evolution). Cultural Studies of Science Education, 12(1), 81-91.
Taber, K. S. (2019). The Nature of the Chemical Concept: Constructing chemical knowledge in teaching and learning. Cambridge: Royal Society of Chemistry.

Notes

¹ An alternative almost tautological interpretation might be that the BBC decides what is 'science news', and it is what is included in Science in Action, might fit some critics complaints that the BBC can be a very arrogant and self-important organisation – if only because there are stories not covered in Science in Action that do get covered in the BBC's other programmes such as BBC Inside Science.

² This might be seen as equivalent to saying that the life-world claim that gravity (as is commonly understood and experienced) exists is taken-for-granted Schutz & Luckmann, 1973). A scientific claim would be different as gravity would need to be operationally defined in terms that were considered objective, rather that just assuming that everyone in the same language community shares a meaning for 'gravity'.

³ The 'luminiferous' aether or ether. The ether was the name given to the fifth element in the classical system where sublunary matter was composed of four elements (earth, water, air, fire) and the perfect heavens from a fifth.

(Film director Luc Besson's sci-fi/fantasy movie 'The Fifth Element' {1997, Gaumont Film Company} borrows from this idea very loosely: Milla Jovovich was cast in the title role as a perfect being who is brought to earth to be reunited with the other four elements in order to save the world.)

⁴ Arguably the difference between forming an opinion on which to base everyday action (everyday as in whether to wear a rain coat, or to have marmalade on breakfast toast, not as in whether to close down the global fossil fuel industry), and proposing formal research conclusions can be compared to the difference between civil legal proceedings (decided on the balance of probabilities – what seems most likely given the available evidence) and criminal proceedings – where a conviction is supposed to depend upon guilt being judged beyond reasonable doubt given the available evidence (Taber, 2013).

Read about writing-up research

⁵ Whether acids do contain hydrated hydrogen ions may seem something that can reasonably be determined, at least beyond reasonable doubt, by empirical investigation. But actually not, as what counts as an acid has changed over time as chemists have redefined the concept according to what seemed most useful. (Taber, 2019, Chapter 6: Conceptualising acids: Reimagining a class of substances).

Balding black holes – a shaggy dog story

Resurrecting an analogy from a dead metaphor?

Keith S. Taber

Now there's a look in your eyes, like black holes in the sky…(Image by Garik Barseghyan from Pixabay)

I was intrigued by an analogy in a tweet

Like a shaggy dog in springtime, some black holes have to shed their "hair."

The link led me to an item at a webpage at 'Science News' entitled 'Black holes born with magnetic fields quickly shed them' written by Emily Conover. This, in turn, referred to an article in Physical Review Letters.

Now Physical Review Letters is a high status, peer-reviewed, journal.

(Read about peer review)

As part of the primary scientific literature, it publishes articles written by specialist scientists in a technical language intended to be understood by other specialists. Dense scientific terminology is not used to deliberately exclude general readers (as sometimes suggested), but is necessary for scientists to make a convincing case for new knowledge claims that seem persuasive to other specialists. This requires being precise, using unambiguous technical language."The thingamajig kind of, er, attaches to the erm, floppy bit, sort of" would not do the job.

(Read about research writing)

Science News however is news media – it publishes journalism (indeed, 'since 1921' the site reports – although that's the publication and not its website of course.) While science journalism is not essential to the internal processes of science (which rely on researchers engaging with each other's work though scholarly critique and dialogue) it is very important for the public's engagement with science, and for the accountability of researchers to the wider community.

Science journalists have a job similar to science teachers – to communicate abstract ideas in a way that makes sense to their audience. So, they need to interpret research and explain it in ways that non-specialists can understand.

The news article told me

"Like a shaggy dog in springtime, some black holes have to shed…
Unlike dogs with their varied fur coats, isolated black holes are mostly identical. They are characterized by only their mass, spin and electric charge. According to a rule known as the no-hair theorem, any other distinguishing characteristics, or "hair," are quickly cast off. That includes magnetic fields."

Conover, 2013

Here there is clearly the use of an analogy – as a black hole is not the kind of thing that has actual hair. This would seem to be an example of a journalist creating an analogy (just as a science teacher would) to help 'make the unfamiliar familiar' to her readers:

just as

dogs with lots of hair need to shed some ready for the warmer weather (a reference to a familiar everyday situation)

so, too, do

black holes (no so familiar to most people) need to lose their hair…

(Read about making the unfamiliar familiar)

But hair?

Surely a better analogy would be along the lines that just as dogs with lots of hair need to shed some ready for the warmer weather, so to do black holes need to lose their magnetic fields…

An analogy is used to show a novel conceptual structure (here, relating to magnetic fields around black holes) maps onto a more familiar, or more readily appreciated, one (here, that a shaggy dog will shed some of its fur). A teaching analogy may not reflect a deep parallel between two systems, as its function may be just to *introduce* an abstract principle.

(Read about science analogies)

Why talk of black holes having 'hair'?

Conover did not invent the 'hair' reference for her ScienceNews piece – rather she built her analogy on a term used by the scientists themselves. Indeed, the title of the cited research journal article was "Magnetic Hair and Reconnection in Black Hole Magnetospheres", and it was a study exploring the consequences of the "no-hair theorem" – as the authors explained in their abstract:

"The no-hair theorem of general relativity states that isolated black holes are characterized [completely described] by three parameters: mass, spin, and charge."

Bransgrove, Ripperda & Philippov, 2021

However, some black holes "are born with magnetic fields" or may "acquire magnetic flux later in life", in which case the fields will vary between black holes (giving an additional parameter for distinguishing them). The theory suggests that these black holes should somehow lose any such field: that is, "The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity" (Bransgrove, Ripperda & Philippov, 2021: 1). There would have to be a mechanism by which this occurs (as energy will be conserved, even when dealing with black holes).

So, the study was designed to explore whether such black holes would indeed lose their 'hair'. Despite the use of this accessible comparison (magnetic flux as 'hair'), the text of the paper is pretty heavy going for someone not familiar with that area of science:

"stationary, asymptotically flat BH spacetimes…multipole component l of a magnetic field…self-regulated plasma…electron-positron discharges…nonzero stress-energy tensor…instability…plasmoids…reconnection layer…relativistic velocities…highly magnetized collisionless plasma…Lundquist number regime…Kerr-schild coordinates…dimensionless BH spin…ergosphere volume…spatial hypersurfaces…[…and so it continues]"

(Bransgrove, Ripperda & Philippov, 2021: 1).

"***Come on Harry, you know full well that 'the characteristic minimum plasma density required to support the rotating magnetosphere is the Goldreich-Julian number density'*** *[Bransgrove, Ripperda & Philippov, 2021: 2]****, so hand me that hyperspanner***."
Image from Star Trek: Voyager (Paramount Pictures)

Spoiler alert

I do not think I will spoil anything by revealing that Bransgrove and colleague conclude from their work that "the no-hair theorem holds": that there is a 'balding process' – the magnetic field decays ("all components of the stress-energy tensor decay exponentially in time"). If any one reading this is wondering how they did this work, given that most laboratory stores do not keep black holes in stock to issue to researchers on request, it is worth noting the study was based on a computer simulation.

That may seem to be rather underwhelming as the researchers are just reporting what happens in a computer model, but a lot of cutting-edge science is done that way. Moreover, their simulations produced predictions of how the collapsing magnetic fields of real black holes might actually be detected in terms of the kinds of radiation that should be produced.

As the news item explained matters:

Magnetic reconnection in balding black holes could spew X-rays that astronomers could detect. So scientists may one day glimpse a black hole losing its hair.

Conover, 2013

So, we have hairy black holes that go through a balding process when they lose their hair – which can be tested in principle because they will be spewing radiation.

Balding is to hair, as…

Here we have an example of an analogy for a scientific concept. Analogies compare one phenomenon or concept to another which is considered to have some structural similarity (as in the figure above). When used in teaching and science communication such analogies offer one way to make the unfamiliar familiar, by showing how the unfamiliar system maps in some sense onto a more familiar one.

hair = magnetic field

balding = shedding the magnetic field

Black holes are expected to be, or at least to become, 'hairless' – so without having magnetic fields detectable from outside the event horizon (the 'surface' connecting points beyond which everything, even light, is unable to 'escape' the gravitational field and leave the black hole). If black holes are formed with, or acquire, such magnetic fields, then there is expected to be a 'balding' process. This study explored how this might work in certain types of (simulated) black holes – as magnetic field lines (that initially cross the event horizon) break apart and reconnect. (Note that in this description the magnetic field lines – imaginary lines invented by Michael Faraday as a mental tool to think about and visualise magnetic fields – are treated as though they are real objects!)

Some such comparisons are deliberately intended to help scientists explain their ideas to the public – but scientists also use such tactics to communicate to each other (sometimes in frivolous or humorous ways) and in these cases such expressions may do useful work as short-hand expressions.

So, in this context hair denotes anything that can be detected and measured from outside a black hole apart form its mass, spin, and charge (see, it is much easier to say 'hair')- such as magnetic flux density if there is a magnetic field emerging from the black hole.

A dead metaphor?

In the research paper, Bransgrove, Ripperda and Philippov do not use the 'hair' comparison as an analogy to explain ideas about black holes. Rather they take the already well-established no-hair theorem as given background to their study ("The original no-hair conjecture states that…"), and simply explain their work in relation to it ("The fate of the magnetic flux (hair) on the event horizon should be in accordance with the no-hair theorem of general relativity.")

Whereas an analogy uses an explicit comparison (this is like that because…), a comparison that is not explained is best seen as a metaphor. A metaphor has 'hidden meaning'. Unlike in an analogy, the meaning is only implied.

"The no-hair theorem of general relativity states that isolated black holes are characterized by three parameters: mass, spin, and charge";
"The original no-hair conjecture states that all stationary, asymptotically flat BH [black hole] spacetimes should be completely described by the mass, angular momentum, and electric charge"

(Read adbout science metaphors)

Bransgrove and colleagues do not need to explain why they use the term 'hair' in their research report as in their community it has become an accepted expression where researchers already know what it is intended to mean. We might consider it a dead metaphor, an expression which was originally used to imply meaning through some kind of comparison, but which through habitual use has taken on literal meaning.

Science has lots of these dead metaphors – terms like electrical charge and electron spin have with repeated use over time earned their meanings without now needing recourse to their origins as metaphors. This can cause confusion as, for example, a learner may develop alternative conceptions about electron spin if they do not appreciate its origin as a metaphor, and assumes an electron spins in the same sense as as spinning top or the earth in space. Then there is an associative learning impediment as the learner assumes an electron is spinning on its axis because of the learner's (perfectly reasonable) associations for the word 'spin'.

The journalist or 'science writer' (such as Emily Conover), however, is writing for a non-specialist readership, so does need to explain the 'hair' reference. So, I would characterise the same use of the terms hair/no-hair and balding as comprising a science analogy in the news item, but a dead metaphor in the context of the research paper. The meaning of language, after all, is in the mind of the reader.

Work cited:

Bransgrove, A., Ripperda, B., & Philippov, A. (2021). Magnetic Hair and Reconnection in Black Hole Magnetospheres. Physical Review Letters, 127(5), 055101. doi:10.1103/PhysRevLett.127.055101 https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.127.055101
Conover, E. (2013, August 3rd 2021). Black holes born with magnetic fields quickly shed them. ScienceNews. https://www.sciencenews.org/article/black-hole-magnetic-field-hair-computer-simulations-physics

Scientific errors in the English National Curriculum

Keith S. Taber

I am writing this open letter to the Institute of Physics and the Royal Society of Chemistry to request that as Learned Societies with some influence with government (perhaps limited, but certainly vastly more than an academic) the Societies might ask the Department for Education to correct two basic errors of science in the National Curriculum for England which is set out as the basis for teaching school age learerns and for developing public examinations specifications and papers.

The two errors relate to (a) the misuse of scientific terminology (the word substance) and (b) a failure of logic (in a reference to conservation of energy). As you will no doubt be aware, the original published version of this iteration of the programmes of study for science in the English National Curriculum included some basic errors (incorrect physics formulae) that received wide publicity and which were quickly amended. Despite some other issues also getting early attention, these other problems have never been addressed. One more complex issue that I strongly feel deserves addressing, but which would would require considerable redrafting, is the confused and incoherent treatment of the nature of chemical reactions across the secondary phase (Key Stages 3 and 4). I have raised these issues at various times, and have published a scholarly analysis of these problems .Whilst I obviously did not expect an article in an academic journal to directly impact policy, I thought this could be a 'springboard' to then approach government. I have contacted the relevant ministers (the Rt Hon Gavin Williamson CBE MP, Secretary of State for Education and the Rt Hon Nick Gibb MP, Minister of State for School Standards), and in response to instructions to refer this issue to the Department for Education website, I did so. My comments have been noted, but I was informed

"there are no current plans to review the curriculum".

Whilst I accept that any detailed re-working of the curriculum is not imminent, I do think the Department could still instigate minor corrections to errors which are published on the government's website, and then consequently repeated by the examination authorities, the examination boards and even individual school websites. Correcting these (surely, embarrassing) errors would require very little effort. The first error I refer to is the incorrect use of the term 'substance'. In science, the term substance has a fairly specific meaning. Although, as with many science concepts, there may be some discussion over precise definitions and demarcations, there is general agreement at the level at which the term would be used in introductory science at school level. In the primary stages of the English National Curriculum for Science we read that Y5 learners should be

"taught to…explain that some changes result in the formation of new materials [sic], and that this kind of change is not usually reversible, including changes associated with burning and the action of acid on bicarbonate of soda".

A better term here would be 'substances', not 'materials' (although this is more a mater of the wording being imprecise than incorrect). However in relation to Y4 learners there is a reference to

"exploring the effect of temperature on substances [sic] such as chocolate, butter, cream"

none of which are substances as the word is used in science.This is a misuse of the term 'substance'. So whereas in secondary school, learners are taught to distinguish the meanings of 'material' and the more specific 'substance', it seems these terms are being used interchangeably in the National Curriculum specification itself. The other issue relates to the statement (in the Key Stage 4 specification) that

"energy is conserved in chemical reactions so can therefore be neither created nor destroyed".

To my reading this suggests a blatant error of logic, which I can only assume does not reflect scientific ignorance by the person drafting the document – but more likely is a typographic error that has never been corrected. Conservation of energy is a general (universal) principle, and its more specific application to chemical reactions as one class of changes is then subsumed under that principle. I have long assumed that what had been intended (but mistyped) was either "energy is conserved in chemical reactions BECAUSE it can be neither created nor destroyed" or "energy CAN be neither created nor destroyed SO THEREFORE is conserved in chemical reactions" – that is, the logic has been completely reversed in the curriculum document. I have recently realised that there is a third possibility: that this statement is not meant as an explanation (of energy conservation in reactions under a more general principle) but as a definition, along the lines "energy is conserved in chemical reactions WHICH MEANS THAT IT CAN be neither created nor destroyed". Whatever was meant, the current wording implies a logical non sequitur, and should, surely, be corrected. I would hope you might agree that these kinds of errors should not be included in what teachers are asked to teach, students to learn, and examining boards to assess; and that when a suitable opportunity arrises you might make appropriate representations regarding the desirability of corrections being made. Your sincerely, Dr Keith S.Taber Emeritus Professor of Science Education (I have had constructive replies from both the RSC and IoP)

How plants get their food to grow and make energy

Respiration produces energy, but photosynthesis produces glucose which produces energy

Keith S. Taber

Mandy was a participant in the Understanding Science Project. When I spoke to her in Y10 (i.e. when she was c.14 year old) she told me that photosynthesis was one of the topics she was studying in science. So I asked her about photosynthesis:

So, photosynthesis. If I knew nothing at all about photosynthesis, how would you explain that to me?
It's how plants get their food to grow and – stuff, and make energy
So how do they make their energy, then?
Well, they make glucose, which has energy in it.
How does the energy get in the glucose?
Erm, I don't know.
It's just there is it?
Yeah, it's just stored energy

I was particularly interested to see if Mandy understood about the role of photosynthesis in plant nutrition and energy metabolism.

Why do you think it is called photosynthesis, because that's a kind of complicated name?
Isn't photo, something to do with light, and they use light to – get the energy.
So how do they do that then?
In the plant they've got chlorophyll which absorbs the light, hm, that sort of thing.
What does it do once it absorbs the light?
Erm.
Does that mean it shines brightly?
No, I , erm – I don't know

Mandy explained that the chlorophyll was in the cells, especially in the plant's leaves. But I was not very clear on whether she had a good understanding of photosynthesis in terms of energy.

Do you make your food?
Not the way plants do.
…
So where does the energy come from in your food then?
It's stored energy.
How did it get in to the food? How was it stored there?
Erm.
[c. 2s pause]
I don't know.

At this point it seemed Mandy was not connecting the energy 'in' food either directly or indirectly with photosynthesis.

Okay. What kind of thing do you like to eat?
Erm, pasta.
Do you think there is any energy value in pasta? Any energy stored in the pasta?
Has lots of carbohydrates, which is energy.
…
So do you think there is energy within the carbohydrate then?
Yeah.
Stored energy.
Yeah.
So how do you think that got there, who stored it?
(laughs) I don't know.

Again, the impression was that Mandy was not linking the energy value of food with photosynthesis. The reference to carbohydrates being energy seemed (given the wider context of the interview) to be imprecise use of language, rather than a genuine alternative conception.

So do you go to like the Co-op and buy a packet of pasta. Or mum does I expect?
Yeah.
Yeah. So do you think, sort of, the Co-op are sort of putting energy in the other end, before they send it down to the shop?
No, it comes from 'cause pasta's made from like flour, and that comes from wheat, and then that uses photosynthesis.

Now it seemed that it was quite clear to Mandy that photosynthesis was responsible for the energy stored in the pasta. It was not clear why she had not suggested this before, but it seemed she could make the connection between the food people eat and photosynthesis. Perhaps (it seems quite likely) she had previously been aware of this and it initially did not 'come to mind', and then at some point during this sequences of questions there was a 'bringing to mind' of the link. Alternatively, it may have been a new insight reached when challenged to respond to the interview questions.

So you don't need to photosynthesise to get energy?
No.
No, how do you get your energy then?
We respire.
Is that different then?
Yeah.
So what's respire then, what do you do when you respire?
We use oxygen to, and glucose to release energy.
Do plants respire?
Yes.
So when do you respire, when you are going to go for a run or something, is that when you respire, when you need the energy?
No, you are respiring all the time.

Mandy suggested that plants mainly respire at night because they are photosynthesising during the day. (Read 'Plants mainly respire at night'.)

So is there any relationship do you think between photosynthesis and respiration?
Erm respiration uses oxygen – and glucose and it produces er carbon dioxide and water, whereas photosynthesis uses carbon dioxide and water, and produces oxygen and glucose.
So it's quite a, quite a strong relationship then?
Yeah.
Yeah, and did you say that energy was involved in that somewhere?
Yeah, in respiration, they produce energy.
What about in photosynthesis, does that produce energy?
That produces glucose, which produces the energy.
I see, so there is no energy involved in the photosynthesis equation, but there is in the glucose?
Yeah.

Respiration does not 'produce' energy of course, but if it had the question about whether photosynthesis also produced energy might have been expected to elicit a response about photosynthesis 'using' energy or something similar, to give the kind of symmetry that would be consistent with conservation of energy (a process and its reverse can not both 'produce' energy). 'Produce' energy might have meant 'release' energy in which case it might be expected the reverse process should 'capture' or 'store' it.

Mandy appreciated the relationship between photosynthetic and respiration in terms of substances, but had an asymmetric notion of how energy was involved.

Mandy appeared to be having difficult appreciating the symmetrical arrangement between photosynthesis and respiration because she was not clear how energy was transformed in photosynthesis and respiration. Although she seemed to have the components of the scientific narrative, she did not seem to fully appreciate how the absorption of light was in effect 'capturing' energy that could be 'stored' in glucose till needed. At this stage in her learning she seemed to have grasped quite a lot of the relevant ideas, but not quite integrated them all coherently.

Energy cannot be made or destroyed (except in biology)

Keith S. Taber

Energy can be made, but only in biology: Amy had learnt that respiration was converting glucose and oxygen into energy – but had learnt in physics that energy cannot be made

Amy was a participant in the Understanding Science Project. Amy was a Y10 (14-15 year old) student who had separate lessons in biology, chemistry and physics. When I spoke to her (see here), she had told me that respiration was "converting glucose into energy and either carbon dioxide and lactic acid, or just carbon dioxide". When I spoke to her again, some weeks later, Amy repeated that respiration was "converting oxygen and glucose into energy and carbon dioxide…it produces energy" ; that trees "need to produce energy and when they photosynthesise they produce like energy"and that food is "broken down and converted into energy".

Later in the same interview I asked her about her physics lessons, where she had been told that "there's like different types of energy" and that it "cannot be made or destroyed, only converted". Amy did not seen to have recognised any conflict between how she understood the role of energy in biology, and what she was taught in physics.

However, on further questioning, she seemed able to recast her biology knowledge to fit what she had been taught in physics:

So in physics, they tell you (that) you cannot make or destroy energy.
Yeah.
And in biology, they tell you that you can make energy from oxygen and glucose?
(No response – Pause of c.2 seconds)
But only in biology, not in physics?
Oh, erm, I suppose the energy, erm well in respiration, erm the energy must be converted from stored energy in food.

So in an interview context, once the linkage was explicitly pointed out, Amy seemed to recognise that the principle learnt in physics should be applied in biology. However, she did not spontaneously make this link, without which the nature of respiration was misunderstood (in terms of energy being created from matter). This would appear to be an example of a fragmentation learning impediment, as although Amy had learnt about the conservation of energy she did not immediately how this related to what she had studied in biology, about respiration.

Converting glucose and oxygen into energy

Keith S. Taber

Amy was a participant in the Understanding Science Project. Amy was a Y10 (14-15 year old) student who had separate lessons in biology, chemistry and physics. When I spoke to her, she told me that in biology she was studying respiration which she suggested was "converting glucose and oxygen into energy…through anaerobic respiration and aerobic respiration". This involved "converting glucose into energy, glucose and oxygen into energy and either carbon dioxide and lactic acid, or just carbon dioxide. Something like that".

In physics lessons she had been studying the topic of electricity, and she recognised that energy was an idea which appeared in both topics:

The work in physics on electricity and the work in biology on respiration, is there any connection there?
Well, in respiration energy is produced, and in physics energy is stored in a battery or a power supply and that then travels round – the circuit.

When I spoke to her again, some weeks later, Amy repeated that respiration was "converting oxygen and glucose into energy and carbon dioxide". She told me that this was important "because it produces energy which like in humans your body needs, well in anything, your body needs and to grow and move and things like that". She also told me that trees were "living and they need to produce energy and when they photosynthesise they produce like energy anyway" but that she obtained energy "through food which is then broken down and converted into energy".

It is a basic principle in science, that energy cannot be created or destroyed. (Since Einstein, is has become clear that strictly matter can be considered as if a form of energy, and interconversion can take place, for example in nuclear processes, but this effect is negligible in normal chemical systems.) What Amy took away from her biology classes, though, was that energy could be produced in respiration and photosynthesis, and that indeed glucose and energy were converted into energy in respiration (i.e., an alternative conception). Amy did not seem to be applying the principle of energy conservation here – although it transpired (see here) that she had recently studied this in her physics lessons.