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.
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
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.
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
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 BBC radio programme 'In Our Time' today tackled the electron. As part of the exploration there was the introduction of the positron, and the notion of matter-antimatter annihilation. These are quite brave topics to introduce in a programme with a diverse general audience (last week Melvyn Bragg and his guests discussed Plato's Atlantis and next week the programme theme is the Knights Templar).
Prof. Victoria Martin of the School of Physics and Astronomy at the University of Edinburgh explained:
If we take a pair of matter and antimatter, so, since we are talking about the electron today, if we take an electron and the positron, and you put them together, they would annihilate.
And they would annihilate not into nothingness, because they both had mass, so they both had energy from E=mc2 that tells us if you have mass you have energy. So, they would annihilate into energy, but it would not just be any kind of energy: the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light. And it will have a very specific amount of energy. Its energy will be equal to the sum of the energy of electron and the positron that they had initially when they collided together.
Prof. Victoria Martin on 'In Our Time'
"An electron and the positron, and you put them together, they would annihilate…they would annihilate into energy" – but this could be misleading.
Now, I am sure that is somewhat different from how Prof. Martin would treat this topic with university physics students – of course, science in the media has to be pitched at the largely non-specialist audience.
It struck me that this presentation had the potential to reinforce a common alternative conception ('misconception') that mass is converted into energy in certain processes. Although I am aware now that this is an alternative conception, I seem to recall that is pretty much what I had once understood from things I had read and heard.
It was only when I came to prepare to teach the topic that I realised that I had a misunderstanding. That, I think, is quite common for teachers – when we have to prepare a topic well enough to explain it to others, we may spot flaws in our own understanding (Taber, 2009)
So, for example, I had thought that in nuclear processes, such as in a fission reactor or fusion in stars, the mass defect (the apparent loss of mass as the resulting nuclear fragments have less mass than those present before the process) was due to that amount of massbeing converted to energy. This is sometimes said to explain why nuclear explosions are so much more violent than chemical explosions, as (given E=mc2): a tiny amount of mass can be changed into a great deal of energy.
Prof. Martin's explanation seemed to support this way of thinking: "they would annihilate into energy".
An alternative conception of particle annihilation: This scheme seems to be implied by Prof. Martin's comments
What is conserved?
It is sometimes suggested that, classically, mass and energy were considered to be separately conserved in processes, but since Einstein's theories of relativity have been adopted, now it is considered that mass can be considered as if a form of energy such that what is conserved is a kind of hybrid conglomerate. That is, energy is still considered conserved, but only when we account for mass that may have been inter-converted with energy. (Please note, this is not quite right – see below.)
So, according to this (mis)conception: in the case of an electron-positron annihilation, the mass of the two particles is converted to an equivalent energy – the mass of the electron and the mass of the positron disappear from the universe and an equivalent quantity of energy is created. Although energy is created, energy is still conserved if we allow for the mass that was converted into this new energy. Each time an electron and positron annihilate, their masses of about 2 ✕ 10-30 kg disappear from the universe and in its place something like 2 ✕ 10-13 J appears instead – but that's okay as we can consider 2 ✕ 10-30 kg as a potential form of energy worth 2 ✕ 10-13 J.
However, this is contrary to what Einstein (1917/2004) actually suggested.
Einstein did not suggest that matter could be changed to energy
Equivalence, not interconversion
What Einstein actually suggested was not that mass could be considered as if another kind/form of energy (alongside kinetic energy and gravitational potential, etc.) that needed to be taken into account in considering energy conservation, but rather that inertial mass can be considered as an (independent) measure of energy.
That is, we think energy is always conserved. And we think thatmass is always conserved. And in a sense they are two measures of the same thing. We might see these two statements as having redundancy:
In a isolated system we will always have the same total quantity of energy before and after any process.
In a isolated system we will always have the same total quantity of mass before and after any process.
As mass is always associated with energy, and so vice versa, either of these statements implies the other. 1
Two conceptions of the shift from a Newtonian to a relativistic view of the conservation of energy (move the slider to change the image)
No interconversion?
So, mass cannot be changed into energy, nor vice versa. The sense in which we can 'interconvert' is that we can always calculate the energy equivalence of a certain mass (E=mc2) or mass equivalence of some quantity of energy (m=E/c2).
So, the 'interconversion' is more like a change of units than a change of entity.
Although we might think of kinetic energy being converted to potential energy reflects a natural process (something changes), we know that changing joules to electron-volts is merely use of a different unit (nothing changes).
If we think of a simple pendulum under ideal conditions 2 it could oscillate for ever, with the total energy unchanged, but with the kinetic energy being converted to potential energy – which is then converted back to kinetic energy – and so on, ad infinitum. The total energy would be fixed although the amount of kinetic energy and the amount of potential energy would be constantly changing. We could calculate the energy in joules or some other unit such as eV or ergs (or calories or kWh or…). We could convert from one unit to another, but this would not change anything about the physical system. (So, this is less like converting pounds to dollars, and more like converting an amount reported in pounds {e.g., £24.83} into an amount reported in pence {e.g., 2483p}.)
Using this analogy, the electron and positron being converted to a photon is somewhat like kinetic energy changing to potential energy in a swinging pendulum (something changes), but it is not the case that mass is changed into energy. Rather we can do our calculations in terms of energy or mass and will get (effectively, given E=mc2) the same answer (just as we can add up a shopping list in pounds or pence, and get the same outcome given the conversion factor, 1.00£ = 100p).
So, where does the mass go?
If mass is conserved, then where does the mass defect – the amount by which the sum of masses of daughter particles is less than the mass of the parent particle(s) – in nuclear processes go? And, more pertinent to the present example, what happens to the mass of the electron and positron when they mutually annihilate?
To understand this, it might help to bear in mind that in principle these process are like any other natural processes – such as the swinging pendulum, or a weight being lifted with pulley, or methane being combusted in a Bunsen burner, or heating water in a kettle, or photosynthesis, or a braking cycle coming to a halt with the aid of friction.
In any natural process (we currently believe)
the total mass of the universe is unchanged…
but mass may be reconfigured
the total energy of the universe is unchanged…
but energy may be reconfigured; and
as mass and energy are associated, any reconfigurations of mass and energy are directly correlated.
So, in any change that involves energy transfers, there is an associated mass transfer (albeit usually one too small to notice or easily measure). We can, for example, calculate the (tiny) increase in mass due to water being heated in a kettle – and know just as the energy involved in heating the water came from somewhere else, there is an equivalent (tiny) decrease of mass somewhere else in the wider system (perhaps due to falling of water powering a hydroelectric power station). If we are boiling water to make a cup of tea, we may well be talking about a change in mass of the order of only 0.000 000 001 g according to my calculations for another posting.
The annihilation of the electron and positron is no different: there may be reconfigurations in the arrangement of mass and energy in the universe, but mass (and so energy) is conserved.
So, the question is, if the electron and positron, both massive particles (in the physics sense, that they have some mass) are annihilated, then where does their mass go if it is conserved? The answer is reflected in Prof. Martin's statement that "the particular kind of energy you get when you annihilate an electron and a positron is a photon, a particle of light". The mass is carried away by the photon.
The mass of a massless particle?
This may seem odd to those who have learnt that, unlike the electron and positron, the photon is massless. Strictly the photon has no rest mass, whereas the electron and positron do have rest mass – that is, they have inertial mass even when judged by an observer at rest in relation to them.
So, the photon only has 'no mass' when it is observed to be stationary – which nicely brings us back to Einstein who noted that electromagnetic radiation such as light could never appear to be at rest compared to the observer, as its very nature as a progressive electromagnetic wave would cease if one could travel alongside it at the same velocity. This led Einstein to conclude that the speed of light in any given medium was invariant (always the same for any observer), leading to his theory of special relativity.
So, a photon (despite having no 'rest' mass) not only carries energy, but also the associated mass.
Although we might think in terms of two particles being converted to a certain amount of energy as Prof. Martin suggests, this is slightly distorted thinking: the particles are converted to a different particle which now 'has' the mass from both, and so will also 'have' the energy associated with that amount of mass.
Mass is conserved during the electron-positron annihilation
A slight complication is that the electron and position are in relative motion when they annihilate, so there is some kinetic energy involved as well as the energy associated with their rest masses. But this does not change the logic of the general scheme. Just as there is an energy associated with the particles' rest masses, there is a mass component associated with their kinetic energy.
The total mass-energy equivalence before the annihilation has to include both the particle rest masses and their kinetic energy. The mass-energy equivalence afterwards (being conserved in any process) also reflects this. The energy of the photon (and the frequency of the radiation) reflects both the particle masses and their kinetic energies at the moment of the annihilation. The mass (being perfectly correlated with energy) carried away by the photon also reflects both the particle masses and their kinetic energies.
How could 'In Our Time' have improved the presentation?
It is easy to be critical of people doing their best to simplify complex topics. Any teacher knows that well-planned explanations can fail to get across key ideas as one is always reliant on what the audience already understands and thinks. Learners interpret what they hear and read in terms of their current 'interpretive resources' and habits of thinking.
A physicist or physics student hearing the episode would likely interpret Prof. Martin's statement within a canonical conceptual framework. However, someone holding the 'misconception' that mass is converted to energy in nuclear processes would likely interpret "they would annihilate into energy" as fitting, and reinforcing, that alternative conception.
I think a key issue here is a slippage that apparently refers to energy being formed in the annihilation, rather than radiation: (i.e., Prof. Martin could have said "they would annihilate into [radiation]"). When the positron and electron 'become' a photon, matter is changed to radiation – but it is not changed to energy, as matter has mass, and (as mass and energy have an equivalence) the energy is already there in the system.
Energy is reconfigured, but is not formed, in the annihilation process.
So, this whole essay is simply suggesting that a change of one word – from energy to radiation – could potentially avoid the formation of, or the reinforcing of, the alternative conception that mass is changed into energy in processes studied in particle physics. As experienced science teachers will know, sometimes such small shifts can make a good deal of difference to how we are interpreted and, so, what comes to be understood.
1 In what is often called a closed system there is no mass entering or leaving the system. However, energy can transfer to, or from, the system from its surroundings. Classically it might be assumed that the mass of a closed system is constant as the amount of matter is fixed, but Einstein realised that if there is a net energy influx to, or outflow from, the system, than some mass would also be transferred – even though no matter enters or leaves.
2 Perhaps in a uniform gravitational field, not subject to to any frictional forces, with an inextensible string supporting the bob, and in thermal equilibrium with its environment.
Fossil pottery? (Images by by Laurent Arroues {background}) and OpenClipart-Vectors from Pixabay)
I was intrigued by some dialogue that was part of one of (physicist) Jim Al-Khalili's interviews for the BBC's 'The Life Scientific' series, where Prof. Al-Khalili "talks to leading scientists about their work, finding out what inspires and motivates them and asking what their discoveries might do for mankind".
The Life Scientific – interviews with scientists about their lives and work
This week he was talking to Dr Judith Bunbury of St. Edmund's College and the Department of Earth Sciences at Cambridge ('Judith Bunbury on the shifting River Nile in the time of the Pharaohs'). It was a fascinating interview, and in particular discussed work showing how the Nile River has repeatedly changed its course over thousands of years. The Nile is considered the longest river in Africa (and possibly the world – the other contender being the Amazon).
Over time the river shifts is position as it unevenly lay down sediment and erodes the river banks – (Image by Makalu from Pixabay)
The exchange that especially piqued my interest followed an account of the diverse material recovered in studies that sample the sediments formed by the river. As sediments are laid down over time, a core (collected by an auger) can be understood to have formed on a time-line – with the oldest material at the bottom of the sample.
Within the sediment, researchers find fragments of animal bone, human teeth, pottery, mineral shards from the working of jewels…
"Are you sure the Nile flows this far?" Using an auger to collect a core (of ice in this case) (Image by David Mark from Pixabay)
Dr Bunbury was taking about how changing fashions allowed the pottery fragments to be useful in dating material – or as the episode webpage glossed this: "pottery fragments which can be reliably time-stamped to the fashion-conscious consumers in the reign of individual Pharaohs".
This is my transcription of the exchange:
[JAK]: …a bit like fossil hunting [JB]: well, I mean, we're just treating pottery as a kind of fossil a kind of fossil, yeah, > no, absolutely > < and it is a fossil < yes, well quite, I can see the similarities.
Prof. Jim Al-Khalili interviewing Dr Judith Bunbury
Now Prof. Jim has a very gentle, conversational, interview style, as befits a programme with extended interviews with scientists talking about their lives (unlike, say, a journalist faced with a politician where a more adversarial style might be needed), so this exchange probably comes as close to a disagreement or challenge as 'The Life Scientific' gets. Taking a slight liberty, I might represent this as:
Al-Khalili: your work is like fossil hunting, the pottery fragments are similar to fossils
Bunbury: no, they ARE fossils
So, here we have an ontological question: are the pottery fragments recovered in archaeological digs (actually) fossils or not?
Bunbury wants to class the finds as fossils.
Al-Khalili thinks that in this context 'a kind of fossil' and 'like fossil hunting' are similes ("I can see the similarities") – the finds are somewhat like fossils, but are not fossils per se.
The term fossil is commonly used in metaphorical ways. For example, for a person to be described as a fossil is to be characterised as a kind of anachronism that has not kept up with social changes.
The term also seems to have been adopted in some areas of science as a kind of adjective. One place it is used is in relation to evidence of dampened ocean turbulence,
"The term 'fossil turbulence' refers to remnants of turbulence in fluid which is no longer turbulent."
Gibson, 1980, p.221
If that seems like a contradiction, it is explained that
"Small scale fluctuations of temperature, salinity, and vorticity in the ocean occur in isolated patches apparently caused by bursts of active turbulence. After the turbulence has been dampened by stable stratification the fluctuations persist as fossil turbulence."
Gibson, 1980, p.221
So, 'fossil turbulence' is not actually turbulence, but more the afterglow of the turbulence: a bit like the aftermath of a lively party which leaves its traces: the the chaotic pattern of abandoned debris provides signs there has been a party although there is clearly no longer a party going on.
"The true nature of fossil groups in the Universe still puzzles the astronomical community. These peculiar systems are one of the most intriguing places in the Universe where giant elliptical galaxies are hosted [sic]."
('Hosted' here also seems metaphorical – who or what could be acting as a host to an elliptical galaxy?)
The term 'fossil group' was introduced for "for an apparently isolated elliptical galaxy surrounded by an X-ray halo, with an X-ray luminosity typical of a group of galaxies" (Zarattini, Biviano, Aguerri, Girardi & D'Onghia, 2012): so, something that looks like a single galaxy, but in other respsects resembles a whole group of galaxies?
Close examination might reveal other galaxies present, yet the 'fossil' group is "distinguished by a large gap between the brightest galaxy and the fainter members" (Dariush, Khosroshahi, Ponman, Pearce, Raychaudhury & Hartley, 2007). Of course, there is normally a 'large gap' between any two galaxies (space contains a lot of, well, space), but presumably this is another metaphor – there is a 'gap' between the magnitude of the luminosity of the brightest galaxy, and the magnitudes of the luminosities of the others.
One way in which language changes over time is through the (metaphorical) death of metaphors. Terms that are initially introduced as metaphors sometimes get generally adopted and over time become accepted terminology.
Many words in current use today were originally coined in this way, and often people are quite unaware of their origins. References to the hands of a clock or watch will these days be taken as simply a technical term (or perhaps for those who only familiar with digital clocks, a complete mystery?) In time, this may happen to 'fossil turbulence' or 'fossil galaxy groups'.
What counts as a fossil?
But it seems reasonable to suggest that, currently at least, these are still metaphors, implying that in some sense the ocean fluctuations or the galactic groups are somewhat like fossils. But these are not actual fossils, just as tin-pot dictators are not actually fabricated from tin.
So, what are actual fossils. The 'classic' fossil takes the form of an ancient, often extinct, living organism, or a part thereof, but composed of rock which has over time replaced the original organic material. In this sense, Prof. Al-Khalili seems correct in suggesting bits of pottery are only akin to fossils, and not actually fossils. But is that how the experts use the term?
Fossils are the preserved remains of plants and animals whose bodies were buried in sediments, such as sand and mud, under ancient seas, lakes and rivers. Fossils also include any preserved trace of life that is typically more than 10 000 years old.
Now, pottery is not the preserved remains of plants or animals or other living organisms, but the site goes on to explain,
Preserved evidence of the body parts of ancient animals, plants and other life forms are called 'body fossils'. 'Trace fossils' are the evidence left by organisms in sediment, such as footprints, burrows and plant roots.
So, footprints, burrows, [evidence of] plant roots 2…or shards of pottery…can be trace fossils? After all, unearthed pottery is indirect evidence of living human creatures having been present in the environment, and, as the BGS also points out "the word fossil is derived from the Latin fossilis meaning 'unearthed'."
However, if the term originally simply meant something unearthed, then although the bits of pot would count as fossils – based on that argument so would potatoes growing in farmers' fields. So, clearly the English word 'fossil' has a more specific meaning in common use than its Latin ancestor.
But going by the BGS definition, Dr Bunbury's unearthed samples of pottery are certainly evidence of organisms left in sediment, so might be considered fossils. These fossils are not the remains of dead organisms, but neither is 'fossil' here simply a metaphor (not even a dead metaphor).
Work cited:
Dariush, A, Khosroshahi, H. G., Ponman, T. J., Pearce, F., Raychaudhury, S. & Hartley, W. (2007), The mass assembly of fossil groups of galaxies in the Millennium simulation, Monthly Notices of the Royal Astronomical Society, Volume 382, Issue 1, 21 November 2007, Pages 433-442, https://doi.org/10.1111/j.1365-2966.2007.12385.x
Gibson, Carl H. (1980) Fossil Temperature, Salinity, and Vorticity Turbulence in the Ocean. In Jacques C.J. Nihoul (Ed.) Marine Turbulence, Elsevier, pp. 221-257.
Romero, I. C., Nuñez Otaño, N. B., Gibson, M. E., Spears, T. M., Fairchild, C. J., Tarlton, L., . . . O'Keefe, J. M. K. (2021). First Record of Fungal Diversity in the Tropical and Warm-Temperate Middle Miocene Climate Optimum Forests of Eurasia [Original Research]. Frontiers in Forests and Global Change, 4. https://doi.org/10.3389/ffgc.2021.768405
Zarattini, S., Biviano, A., Aguerri, J. A. L., Girardi, M. & D'Onghia, E. (2012) Fossil group origins – XI. The dependence of galaxy orbits on the magnitude gap, Astronomy & Astrophysics, 655 (2021) A103, DOI: https://doi.org/10.1051/0004-6361/202038722.
Notes:
1 "Fossils are the preserved remains of plants and animals whose bodies …". But this suggests that fungi do not form fossils. The same site points out that "We tend to think of fungi, such as mushrooms and toadstools, as being plants — but they are not. They neither grow from embryos nor photosynthesise and are put in a separate kingdom" (https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/plants-2/) – yet does not seem to mention any examples of fungi that have been fossilised (so the comment could be read to be meant to suggest that fossil fungi are found as well as fossil plants; but could equally well be read to mean that as fungi are not plants they do not fossilise).
The second quote here is more inclusive: "Preserved evidence of the body parts of ancient animals, plants and other life forms…" The site does also specify that "Remains can include microscopically small fossils, such as single-celled foraminifera…" (https://www.bgs.ac.uk/discovering-geology/fossils-and-geological-time/fossils/).
So, just to be clear, fossil fungi have been found.
2 If the roots were themselves fossilised then these would surely be body fossils as roots are parts of plant. Presumably this is meant to refer to the channels in soil when the roots grow through the soil.
we are made of particles that have existed since the moment the universe began…those atoms travelled 14 billion years through time and space
The Big Bang Theory (but not quite the big bang theory).
What is the Big Bang Theory?
The big bang theory is a theory about the origin and evolution of the universe. Being a theory, it is conjectural, but it is the theory that is largely taken by scientists as our current best available account.
According to big bang theory, the entire universe started in a singularity, a state of infinite density and temperature, in which time space were created as well as matter. As the universe expanded it cooled to its present state – some, about, 13.8 billion years later.
Our current best understanding of the Cosmos is that the entire Universe was formed in a 'big bang' (Image by Gerd Altmann from Pixabay)
The term 'big bang' was originally intended as a kind of mockery – a sarcastic description of the notion – but the term was adopted by scientists, and has indeed become widely used in general culture.
Which brings me to 'The Big Bang Theory', which is said to have been the longest ever running sitcom ('situation comedy') – having been in production for longer than even 'Friends'.
The Big Bang Theory: Not science fiction, but fictional science? (Five of these characters have PhDs in science: one 'only' has a master's degree in engineering.)
A situation comedy is set around a situation. The situation was that two Cal Tech physicists are sharing an apartment. Leonard (basically a nice guy, but not very successful with women) is flatmate to Sheldon, a synaesthete, and kind of savant (a device on which to lever much of the humour) – a genius with an encyclopaedic knowledge of most areas of science but a deficient 'theory of mind' such that he lacks
insight into others, and so also
empathy, and
the ability to tell when people are using humour or being sarcastic to him.
If most physicists were like Sheldon we could understand why the big bang theory is still called the big bang theory even though the term was intended to be facetious. The show writers claim that Sheldon was not deliberately written to be on the autistic spectrum, but he tends to take statements literally: when it is suggested that he is crazy, he responds that he knows he is not as his mother had him tested as a child.
Sheldon (at right, partially in shot) has been widely recognised by viewers as showing signs of high-functioning Autism or Aspergers syndrome. (Still from The Big Bang Theory)
These guys hang out with Raj (Rajesh), an astrophysicist and Cambridge graduate so shy he is unable to speak to women, or indeed in their presence (presumably not a problem inherited from his father who is is a successful gynaecologist in India), and an engineer, Howard, who to my viewing is just an obnoxious creep with no obvious redeeming qualities. (But then I've not seen the full run.) When Howard becomes a NASA astronaut, he is bullied by the other astronauts, and whilst bullying is never acceptable, it is difficult to be too judgemental in his case.
This group are scientists, and they are 'nerds'. They watch science fiction and superhero movies, buy comic books and action figures, play competitive board games and acquire all the latests technical gadgets. And, apart from Sheldon (who has a strong belief in following a principled rigorous regime of personal hygiene that makes close contact with other humans seem repulsive) they try, and largely fail, to attract women.
In case this does not seem sufficiently stereotypical, the situation is complete when a young woman moves into in the flat opposite Leonard and Sheldon: Penny is the 'hot' new neighbour, who comes across as a 'dumb blonde' (she wants to be an actress – she is actually a waitress whilst she works at that), something of a hedonist, and not having the slightest knowledge of, or interest in, science. Penny's plan in life is to become a movie star, and her back-up plan is to become a television star.
If Sheldon and his friends tend to rather fetishise science and see it as inherently superior to other ways of engaging in the world, then Penny seems to reflect the other side of 'the two cultures' of C. P. Snow's famous lecture/essay that described an arts-science divide in mid-twentieth century British public life. That is, not only an acknowledged ignorance of scientific matters, but an ignorance that is almost worn as a badge of honour. Penny, of course, actually has a good deal of knowledge about many areas of culture that our 'heroes' are ignorant of.
Initially, Penny is the only lead female character in the show. This creates considerable ambiguity in how we are expected to see the show's representations of scientists during the early series. Is the viewer meant to be sharing their world where women are objects of recreation and sport and a distraction from the important business of the scientific quest? Or, is the audience being asked to laugh at these supposedly highly intelligent men who actually have such limited horizons?
Sheldon: I am a physicist. I have a working knowledge of the entire universe and everything it contains.
Penny. Who's Radiohead?
[pause]
Sheldon: I have a working knowledge of important things in the universe.
Penny has no interest in science
So, the premise is: can the nerdy, asthmatic, short-sighted, physicist win over the pretty, fun-loving, girl-next-door who is clearly seen to be 'out of his league'.
Spoiler alert
Do not read on if you wish to watch the show and find out for yourself. 😉
A marriage made in the heavens?
I recently saw an episode in series n (where n is a large positive integer) where Leonard and Penny decided to go to Las Vagas and get married. Leonard said he had written his own marriage vows – and it was these that struck me as problematic. My complaint was nothing to do with love and commitment, but just about physics.
Cal Tech physicist Leonard Hofstadter (played by Johnny Galecki) wrote his own vows for marriage to Penny (Kaley Cuoco) in 'The Big Bang Theory'
A non-physical love?
I made a note of Leonard's line:
"Penny, we are made of particles that have existed since the moment the universe began. I like to think those atoms travelled 14 billion years through time and space to create us so that we could be together and make each other whole."
Leonard declares his love
Sweet. But wrong.
Perhaps Leonard had been confused by the series theme music, the 'History of Everything', by the band Barenaked Ladies. The song begins well enough:
"Our whole universe was in a hot dense state
Then nearly fourteen billion years ago, expansion started…"
Lyrics to History of Everything (The Big Bang Theory Theme)
but in the second verse we are told
"As every galaxy was formed in less time than it takes to sing this song.
A fraction of a second and the elements were made."
Lyrics to History of Everything (The Big Bang Theory Theme)
which seems to reflect a couple of serious alternative conceptions.
So, the theme song seems to suggest that once the big bang had occurred, "nearly fourteen billion years ago", the elements were formed in a matter of seconds, and the galaxies in a matter of minutes. Leonard goes further, and suggests the atoms that he and Penny are comprised of have existed since "the moment the universe began". This is all contrary to the best understanding of physicists.
Surely Leonard, who defended his PhD thesis on particle physics, would know more about the canonical theories about the formation of those particles? (If not, he could ask Raj who once applied for a position in stellar evolution.)
The "hot dense state" was so hot that no particles could have condensed out. Certainly, some particles began to appear very soon after the big bang, but for much of the early 'history of everything' the only atoms that could exist were of the elements hydrogen, helium and lithium – as only the nuclei of these atoms were formed in the early universe.
The formation of heavier elements – carbon, oxygen, silicon and all the rest – occurred in stars – stars that did not exist until considerable cooling from the hot dense state had occurred. (See for example, 'A hundred percent conclusive science. Estimation and certainty in Maisie's galaxy'.) Most of the matter comprising Leonard, Penny, and the rest of us, does not reflect the few elements formed in the immediate aftermath of the big bang, but heavier elements that were formed billions of years later in stars that went supernovae and ejected material into space. 1 As has often been noted, we are formed from stardust.
"…So don't forget the human trial, The cry of love, the spark of life, dance thru the fire
Stardust we are Close to divine Stardust we are See how we shine"
From the lyrics to 'Stardust we are' (The Flower Kings – written by Roine Stolt and Tomas Bodin)
Does it matter – it is only pretend
Of course The Big Bang Theory (unlike the big bang theory) is not conjecture, but fiction. So, does it matter if it gets the science wrong? The Big Bang Theory is not meant to be science fiction, but a fiction that uses science to anchor it into a situation that will allow viewers to suspend disbelief.
Leonard is a believable character, but Sheldon is an extreme outlier. Howard and Raj are caricatures, exaggerations, as indeed are Amy (neurobiologist) and Bernadette (microbiologist) the other core characters introduced later.
But the series creators and writers seem to have made a real effort at most points in the show to make the science background authentic. Dialogue, whiteboard contents, projects, laboratory settings and the like seem to have been constructed with great care so that the scientifically literate viewer is comfortable with the context of the show. This authentic professional context offers the credible framework within which the sometimes incredible events of the characters' lives and relationships do not seem immediately ridiculous.
In that context, Leonard getting something so wrong seems incongruent.
Then again, he is in love, so perhaps his vows are meant to tell the scientifically literate viewer that there is a greater truth than even science – that in matters of the heart, poetic truth trumps even physics?
A Marillion song tells us:
A wise man once wrote That love is only An ancient instinct For reproduction Natural selection A wise man once said That everything could be explained And it's all in the brain
But as the same song asks: "where is the wisdom in that?"
Source cited:
Snow, C. P. (1959/1998). The Rede Lecture, 1959: The two cultures. In The Two Cultures (pp. 1-51). Cambridge University Press.
Note:
1 I was tempted to write 'most of the atoms'. Certainly most of the mass of a person is made up of atoms 2 that were formed a long time after the big bang. However, in terms of numbers of atoms, there are more of the (lightest) hydrogen atoms than of any other element: we are about 70% water, and water comprises molecules of H2O. So, that is getting close to half the atoms in us before we consider all the hydrogen in the fats and proteins and so forth.
2 That, of course, assumes the particles we are made of are atoms. Actually, we are comprised chemically of molecules and ions and relatively very, very few free atoms (those that are there are accidentally there in the sense they are not functional). No discrete atoms exist within molecules. So, to talk of the hydrogen atoms in us is to abstract the atoms from molecules and ions.
Leonard confuses matters (and matter) by referring initially to particles (which could be nucleons, quarks?) but then equating these to atoms – even though atoms are unlikely to float around for nearly 14 billion years without interacting with radiation and other matter to get ionised, form molecules, that may then dissociate, etc.
For many people reading this, I am making a pedantic point. When we talk of the atoms in a person's body, we do not actually mean atomsper se, but component parts of molecules of compounds of the element indicated by the atomreferred to*. A water molecule does not contain two hydrogen atoms and an oxygen atom, but it does contain two hydrogen atomic nuclei, and the core of an oxygen atom (its nucleus, and inner electron 'shell') within an 'envelope' of electrons.
* So, it is easier to use the shorthand: 'two atoms of hydrogen and one of oxygen'.
The reason it is sometimes important to be pedantic is that learners often think of a molecule as just a number of atoms stuck together and not as a new unitary entity composed of the same set of collective components but in a new configuration that gives it different properties. (For example, learners sometimes think the electrons in a covalent bond are still 'owned' by different atoms.) There is an associated common alternative conception here: the assumption of initial atomicity, where students tend to think of chemical processes as being interactions between atoms, even though reacting substances are very, very rarely atomic in nature.
NASA's James Webb Space Telescope is now operational, and offering new images of 'deep space'. This has led to claims of finding images of objects from further away in the Universe, and so from further back in time, than previously seen. This should support a lot of new scientific work and will surely lead to some very interesting findings. Indeed, it seems to have had an almost immediate impact.
Maisie's galaxy
One of these new images is of an object known as:
CEERSJ141946.35-525632.8
or less officially (but more memorably) as
Masie's galaxy.
A red smudge on one of the new images has been provisionally identified as evidence of a galaxy as it was less than 300Â 000Â 000 years after the conjectured 'big bang' event understood as the origin of the universe. The galaxy is so far away that its light has taken since then to reach us.
Three hundred million years seems a very long time in everyday terms, but it a small fraction of the current age of the universe, believed to be around fourteen billion years. 1
300 000 000 years
≪ 14 000 000 000 years
The age estimate is based on the colour of the object, reflecting its 'redshift':
"Scientists with the CEERS Collaboration have identified an object–dubbed Maisie's galaxy in honor of project head Steven Finkelstein's daughter–that may be one of the earliest galaxies ever observed. If its estimated redshift of 14 is confirmed with future observations, that would mean we're seeing it as it was just 290 million years after the Big Bang."
This finding is important in understanding the evolution of the universe – for example, observing the earliest galaxies puts a limit on how long the universe existed before star formation started. (Although the episode was called 'The first galaxies at the universe's dawn' Masie's galaxy is thought to contain heavier elements that were produced in even earlier stars.)
Uncertainty in science (and certainty in reporting science)
So, the claim is provisional. It is an estimate awaiting confirmation.
Strictly, science is concerned with provisional knowledge claims. This is not simply because scientists can make mistakes. All measurements are subject to limits in precision (measurement 'errors'). More fundamentally, all measurements depend on a theory of the instrumentation used, and theoretical knowledge is always open to being revisited on the basis of new ways of understanding.
We may not expect the theory behind the metre rule to change any time soon (although even there, our understanding shifted somewhat with Einstein's theories) but many scientific observations depend on highly complex apparatus, both for data collection and analysis. Despite this, science is often represented in the media, both by commentators and sometimes scientists themselves, as if it produced absolute certainty.
"We can look deep into out past by taking these deep images, and we can find the sort of faintest red smudges and that tells us that they are extremely far away, and from exactly how red they are we can estimate that distance."
So, the figure of 290 000 000 years after the big bang is an estimate. Fair enough, but what 'caught my ear', so to speak, was the contrast between the acknowledged uncertainty of the current estimate, and the claimed possibility of moving from this to absolute knowledge,
"If this distance we have measured for Masie's galaxy, of a red shift of 14, holds true, and I can't stress enough that we need spectroscopic confirmation to precisely measure that distance. [*] Where you take a telescope, could be James Webb, could be a different telescope, you observe it [the galaxy] and you split the light into its component colours, and you can actually precisely measure – measure the red shift, measure the distance – a hundred percent conclusively."
Associate Professor Steve Finke [* To my ear, there might well be an edit at this point – the quote is based on what was broadcast which might omit or re-sequence parts of the interview.]
Spectroscopic analysis allows us to compare the pattern of redshifted spectral lines due to the presence of elements absorbing or emitting radiation, with the position of those lines as they are found without any shift. Each element has its own pattern of lines – providing a metaphorical fingerprint. A redshift (or blueshift) moves these lines to different parts of the spectrum, but does not change their collective profile as all the lines are moved to the same extent.
Spectral lines can be used like fingerprints to identify substances. (Image by No-longer-here from Pixabay)
Some of these lines are fine, allowing precise measurements of wavenumber/frequency, and there are enough of them to be able to make very confident assignments of the 'fingerprints', and use this to estimate the shift. We might extend our analogy to a fingerprint on a rubber balloon which had been stretched since a fingerprint was made. In absolute terms, the print would no longer (or 'no wider' for that matter) fit the finger that made it, but the distortion is systematic allowing a match to be made – and the degree of stretching to be calculated.
If a pattern is distorted in a systematic way, we may still be able to match it to an undistorted version (Original images by Clker-Free-Vector-Images (balloon), OpenClipart-Vectors (print) and Alexander (notepad) from Pixabay)
Yet, even though this is a method that is considered well-understood, reliable, and potentially very accurate and precise 2, I am not sure you can "precisely measure, measure the redshift, measure the distance. A hundred percent conclusively". Science, at least as I understand it, always has to maintain some small level of humility.
Scientists may be able to confirm and hone the estimate of 290Â 000Â 000 years after the big bang for the age of Maisie's galaxy. Over time, further observations, new measurements, refinement in technique, or even theory, may lead to successive improvements in that age measurement and both greater accuracy and greater precision.2 But any claim of a conclusive measurement to a precision of 100% has a finality that sounds like something other than science to me.
Notes
1 Oddly, most webages I've seen that cite values for the age of the universe do not make it explicit whether these are American (109) or English (1012) billions! It seems to be assumed that, as with sulfur [i.e., sulphur], and perhaps soon aluminum and fosforus, we are all using American conventions.
2 Precision and accuracy are different. Consider an ammeter.
An ammeter (Image by Gerd Altmann from Pixabay)
Due to the method of reading a needle position against a scale there is a limit to precision (perhaps assumed to the nearest calibration, so to ±0.5 calibrations). This measurement error of ±0.5 units is, in effect, a limit in detail or resolution, but not an 'error' in the everyday sense of getting something wrong. However, if the meter had been miscalibrated, or over time has shifted from calibration, so the needle is misaligned (so perhaps the meter reads +0.15 A when it is not connected into a circuit) then that is inaccuracy. There is always some level of imprecision (some limit on how precise we can be), even when we have an accurate reading.
In science, a measurement normally offers a best estimate of a true value, with an error range acknowledging how far the real value might be from that best estimate. See the example below: Measurement B claims the most precision, but is actually inaccurate. Measurement A is the most accurate (but least precise).
If we imagine that a galaxy was being seen as it was
275 000 000 years after the big bang
and three measurements of its age were given as:
A: 280 000 000 ± 30 000 000 years after the big bang
(i.e., 250 000 000 – 310 000 000)
B: 290 000 000 ± 10 000 000 years after the big bang
(i.e., 280 000 000 – 300 000 000)
C: 260 000 000 ± 20 000 000 years after the big bang
(i.e., 240 000 000 – 280 000 000)
then measurement B is more precise (it narrows down the possible range the most) but is inaccurate (as the actual age falls outside the range of this measurement). Of course, unlike in such a hypothetical example, in a real case we would not know the actual age to allow us to decide which of the measurements is more accurate.
How can we count the number of stars in the galaxy?
On the BBC radio programme 'More or Less' it was mooted that there might be one hundred billion (100 000 000 000) stars in our own Milky Way Galaxy (and that this might be a considerable underestimate).
Programme presenter Tim Harford was tackling a question sent in by a young listener (who is very almost four years of age) about whether there are more bees in the world than stars in the galaxy? (Spoiler alert: Prof. Catherine Heymans confessed to knowing less about bees than stars.)
Hatford asked how the 100 billion stars figure was arrived at:
"have we counted them, or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"
The last suggestion here is of course the basis for many surveys. As long as there is good reason to think a sample is representative of the wider population it is drawn from we can collect data from the sample and make inferences about the population at large.
So, if we counted all the detectable stars in a typical 1% of the sky and then multiplied the count by 100 we would get an approximation to the total number of detectable stars in the whole sky. That would be a reasonable method to find approximately how many stars there are in the galaxy, as long as we thought all the detected stars were in our galaxy and that all the stars in our galaxy were detectable.
Prof. Heymans replied
"So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out 1% of all the stars in our Milky Way galaxy, creating a three dimensional map. So, that's looking at 1 billion of the stars, and then to get an idea of how many others are there we look at how bright all the stars are, and we use our sort of models of how different types of stars live [sic] in our Milky Way galaxy to give us that estimate of how many stars are there."
Prof. Catherine Heymans interviewed on 'More or Less'
A tautology?
This seemed to beg a question: how can we know we are mapping 1% of stars, before we know how many stars there are?
This has the appearance of a tautology – a circular argument.
If we assume there are one hundred billion, then we need to
count one billion, and then
multiply by 100 to give…
one hundred billion.
Clearly that did not seem right. I am fairly sure that was not what Prof. Haymans meant. As this was a radio programme, the interview was presumably edited to fit within the limited time allocated for this item, so a listener can never be sure that a question and (apparently immediately direct) response that makes the edit fully reflects the original conversation.
Counting the bright ones
According to the website of the Gaia mission, "Gaia will achieve its goals by repeatedly measuring the positions of all objects down to magnitude 20 (about 400 000 times fainter than can be seen with the naked eye)." Hartman's suggestion that "you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?" seems very reasonable, until you realise that even with a powerful telescope sent outside of the earth's atmosphere, many of the stars in the galaxy may simply not be detectable. So, what we see cannot be considered to be fully representative of what is out there.
It is not then that the scientists have deliberately sampled 1%, but rather they are investigating EVERY star with an apparent brightness above a certain critical cut off. Whether a star makes the cut, depends on such factors as how bright it is (in absolute terms – which we might imagine we would measure from a standard distance 1) and how close it is, as well as whether the line of sight involves the starlight passing through interstellar dust that absorbs some (or all) of the radiation.
Of course, these are all strictly, largely, unknowns. Astrophysics relies a good on boot-strapping, where our best, but still developing, understanding of one feature is used to build models of other features. In such circumstances, observational tests of predictions from theory are often as much testing the underlying foundations upon which a model used to generate a prediction is built as that specific focal model itself. Knowledge moves on incrementally as adjustments are made to different aspects of interacting models.
Observations are theory-dependent
So, this is, in a sense, a circular process, but it is a virtuous circle rather than just a tautology as there are opportunities for correcting and improving the theoretical framework.
In a sense, what I have described here is true of science more generally, and so when an experiment fails to produce a result predicted by a new theory, it is generally possible to seek to 'save' the theory by suggesting the problem was (if not a human error) not in the actual theory being tested, but in some other part of the more extended theoretical network – such as the theory underpinning the apparatus used to collect data or the the theory behind the analysis used to treat data.
In most mature fields, however, these more foundational features are generally considered to be sound and unlikely to need modifying – so, a scientist who explains that their experiment did not produce the expected answer because electron microscopes or mass spectrometers or Fourier transform analyses do not work they way everyone has for decades thought they did would need to offer a very persuasive case.
However, compared to many other fields, astrophysics has much less direct access to the phenomena it studies (which are often vast in terms of absolute size, distance and duration), and largely relies on observing without being able to manipulate the phenomena, so understandably faces special challenges.
Why we need a theoretical model to finish the count
Researchers can use our best current theories to build a picture of how what we see relates to what is 'out there' given our best interpretations of existing observations. This is why the modelling that Prof. Heymans refers to is so important. Our current best theories tell us that the absolute brightness of stars (which is a key factor in deciding whether they will be detected in a sky survey) depends on their mass, and the stage of their 'evolution'.2
So, completing the count needs a model which allows data for detectable stars to be extrapolated, bearing in mind our best current understanding about the variations in frequencies of different kinds (age, size) of star, how stellar 'densities' vary in different regions of a spiral galaxy like ours, the distribution of dust clouds, and so forth.
…keep in mind we are off-centre, and then allow for the thinning out near the edges, remember there might be a supermassive black hole blocking our view through the centre, take into account dust, acknowledge dwarf stars tend to be missed, take into account that the most massive stars will have long ceased shining, then take away the number you first thought of, and add a bit for luck… (Image by WikiImages from Pixabay)
I have taken the liberty of offering an edited exchange
Hartford: "have we counted [the hundred billion stars], or got a computer to count them, or is it more a case of, well, you take a photograph of a section of sky and you sort of say well the rest is probably a bit like that?"
Heymans "So, we have the European Space Agency Gaia mission up at the moment, it was launched in 2013, and that's currently mapping out…all the stars in our Milky Way galaxy [that are at least magnitude 20 in brightness], creating a three dimensional map. So, that's looking at 1 billion of the [brightest] stars [as seen from our solar system], and then to get an idea of how many others are there we look at how bright all the stars are, and we use our models of how different types of stars [change over time 2] in our Milky Way galaxy to give us that estimate of how many stars are there."
No more tautology. But some very clever and challenging science.
2 Stars are not alive, but it is common to talk about their 'life-cycles' and 'births' and 'deaths' as stars can change considerably (in brightness, colour, size) as the nuclear reactions at their core change over time once the hydrogen has all been reacted in fusion reactions.
Photosynthesis illuminating a plant? (Image by OpenClipart-Vectors from Pixabay)
Analogies, metaphors and similes are used in communication to help make the unfamiliar familiar by suggesting that some novel idea or phenomena being introduced is in some ways like something the reader/listener is already familiar with. Analogies, metaphors and similes are commonly used in science teaching, and also in science writing and journalism.
An analogy maps out similarities in structure between two phenomena or concepts. This example, from a radio programme, compared the COVID pandemic with photosynthesis.
"So, what we were particularly aiming to do, was to understand the collision between a range of different political economic factors of a pre-2020 world, and how they were sort of reassembled and deployed to cope with something which was without question unprecedented.
We used this metaphor of photosynthesis because if you think about photosynthesis in relation to plants, the sun both lights things up but at the same time it feeds them and helps them to grow, and I think one of the things the pandemic has done for social scientists is to serve both as a kind of illumination of things that previously maybe critical political economists and heterodox scholars were pointing to but now became very visible to the mainstream media and to mainstream politics. But at the same time it also accentuated and deepened some of those tendencies such as our reliance on various digital platforms, certain gender dynamics of work in the household, these sort of things that became acute and undeniable and potentially politicised over the course of 20230, 2021."
Prof. Will Davies, talking on 'Thinking Allowed' 1
Will Davies, Professor in Political Economy at Goldsmiths, University of London was talking to sociologist Prof. Laurie Taylor who presents the BBC programme 'Thinking Aloud' as part of an episode called 'Covid and change'
A scientific idea used as analogue
Prof. Davies refers to using "this metaphor of photosynthesis". However he goes on to suggest how the two things he is comparing are structurally similar – the pandemic has shone a light on social issues at the same time as providing the conditions for them to become more extreme, akin to how light both illuminates plants and changes them. A metaphor is an implicit comparison where the reader/listener is left to interpret the comparison, but a metaphor or simile that is explicitly developed to explain the comparison can become an analogy.
Often science concepts are introduced by analogy to more familiar everyday ideas, objects or events. Here, however, a scientific concept, photosynthesis is used as the analogue – the source used to explain something novel. Prof. Davies assumes listeners will be familiar enough with this science concept for it to helpful in introducing his research.
Mischaracterising photosynthesis?
A science teacher might not like the notion that the sun feeds plants – indeed if a student suggested this in a science class it would likely be judged as an alternative conception. In photosynthesis, carbon dioxide (from the atmosphere) and water (usually absorbed from the soil) provide the starting materials, and the glucose that is produced (along with oxygen) enables other processes – such as growth which relies on other substances also being absorbed from the soil. (So-called 'plant foods', which would be better characterised as plant nutritional supplements, contain sources of elements such as nitrogen, phosphorus and potassium). Light is necessary for photosynthesis, but the sunlight is not best considered 'food'.
One might also argue that Prof. Davies has misidentified the source for his analogy, and perhaps he should rather have suggested sunlight as the source metaphor for his comparison as sunlight both illuminates plants and enables them to grow. Photosynthesis takes place inside chloroplasts within a plant's tissues, and does not illuminate the plant. However, Prof. Davies' expertise is in political economy, not natural science, and it was good to see a social scientist looking to use a scientific idea to explain his research.
Faster-than-light electrons race from a sitting start and are baked to give off light brighter than millions of suns that can be used to image tiny massage balls: A case of science communication
Keith S. Taber
(The pedantic science teacher)
Ockham's razor
Ockham's razor (also known as Occam's razor) is a principle that is sometimes applied as a heuristic in science, suggesting that explanations should not be unnecessarily complicated. Faced with a straightforward explanation, and an alternative convoluted explanation, then all other things being equal we should prefer the former – not simply accept it, but to treat is as the preferred hypothesis to test out first.
Ockham's Razor is also an ABC radio show offering "a soap box for all things scientific, with short talks about research, industry and policy from people with something thoughtful to say about science". The show used to offer recorded essays (akin to the format of BBC's A Point of View), but now tends to record short live talks.
I've just listened to an episode called The 'science donut' – in fact I listened several time as I thought it was fascinating – as in a few minutes there was much to attend to.
I approached the episode as someone with an interest in science, of course, but also as an educator with an ear to the ways in which we communicate science in teaching. Teachers do not simply present sequences of information about science, but engage pedagogy (i.e., strategies and techniques to support learning). Other science communicators (whether journalists, or scientists themselves directly addressing the public) use many of the same techniques. Teaching conceptual material (such as science principles, theories, models…) can be seen as making the unfamiliar familiar, and the constructivist perspective on how learning occurs suggests this is supported by showing the learner how that which is currently still unfamiliar, is in some way like something familiar, something they already have some knowledge/experience of.
Science communicators may not be trained as teachers, so may sometimes be using these techniques in a less considered or even less deliberate manner. That is, people use analogy, metaphor, simile, and so forth, as a normal part of everyday talk to such an extent that these tropes may be generated automatically, in effect, implicitly. When we are regularly talking about an area of expertise we almost do not have to think through what we are going to say. 1
Science communicators also often have much less information about their audience than teachers: a radio programme/podcast, for example, can be accessed by people of a wide range of background knowledge and levels of formal qualifications.
One thing teachers often learn to do very early in their careers is to slow down the rate of introducing new information, and focus instead on a limited number of key points they most want to get across. Sometimes science in the media is very dense in the frequency of information presented or the background knowledge being drawn upon. (See, for example, 'Genes on steroids? The high density of science communication'.)
A beamline scientist
Dr Emily Finch, who gave this particular radio talk, is a beamline scientist at the Australian Synchrotron. Her talk began by recalling how her family visited the Synchrotron facility on an open day, and how she later went on to work there.
She then gave an outline of the functioning of the synchrotron and some examples of its applications. Along the way there were analogies, metaphors, anthropomorphism, and dubiously fast electrons.
The creation of the god particle
To introduce the work of the particle accelerator, Dr Finch reminded her audience of the research to detect the Higgs boson.
"Do you remember about 10 years ago scientists were trying to make the Higgs boson particle? I see some nods. They sometimes call it the God particle and they had a theory it existed, but they had not been able to prove it yet. So, they decided to smash together two beams of protons to try to make it using the CERN large hadron collider in Switzerland…You might remember that they did make a Higgs boson particle".
This is a very brief summary of a major research project that involved hundreds of scientists and engineers from a great many countries working over years. But this abbreviation is understandable as this was not Dr Finch's focus, but rather an attempt to link her actual focus, the Australian Synchrotron, to something most people will already know something about.
However, aspects of this summary account may have potential to encourage the development of, or reinforce an existing, common alternative conception shared by many learners. This is regarding the status of theories.
In science, theories are 'consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world', yet students often understand theories to be nothing more than just ideas, hunches, guesses – conjectures at best (Taber, Billingsley, Riga & Newdick, 2015). In a very naive take on the nature of science, a scientist comes up with an idea ('theory') which is tested, and is either 'proved' or rejected.
This simplistic take is wrong in two regards – something does not become an established scientific theory until it is supported by a good deal of evidence; and scientific ideas are not simply proved or disproved by testing, but rather become better supported or less credible in the light of the interpretation of data. Strictly scientific ideas are never finally proved to become certain knowledge, but rather remain as theories. 2
In everyday discourse, people will say 'I have a theory' to mean no more that 'I have a suggestion'.
A pedantic scientist or science teacher might be temped to respond:
"no you don't, not yet,"
This is sometimes not the impression given by media accounts – presumably because headlines such as 'research leads to scientist becoming slightly more confident in theory' do not have the same impact as 'cure found', 'discovery made, or 'theory proved'.
The message that could be taken away here is that scientists had the idea that Higgs boson existed, but they had not been able to prove it till they were able to make one. But the CERN scientists did not have a Higgs boson to show the press, only the data from highly engineered detectors, analysed through highly complex modelling. Yet that analysis suggested they had recorded signals that closely matched what they expected to see when a short lived Higgs decayed allowing them to conclude that it was very likely one had been formed in the experiment. The theory motivating their experiment was strongly supported – but not 'proved' in an absolute sense.
The doughnut
Dr Finch explained that
"we do have one of these particle accelerators here in Australia, and it's called the Australian Synchrotron, or as it is affectionately known the science donut
…our synchrotron is a little different from the large hadron collider in a couple of main ways. So, first, we just have the one beam instead of two. And second, our beam is made of electrons instead of protons. You remember electrons, right, they are those tiny little negatively charged particles and they sit in the shells around the atom, the centre of the atom."
Dr Emily Finch talking on Ockham's Razor
One expects that members of the audience would be able to respond to this description and (due to previous exposure to such representations) picture images of atoms with electrons in shells. 'Shells' is of course a kind of metaphor here, even if one which with continual use has become a so-called 'dead metaphor'. Metaphor is a common technique used by teachers and other communicators to help make the unfamiliar familiar. In some simplistic models of atomic structure, electrons are considered to be arranged in shells (the K shell, the L shell, etc.), and a simple notation for electronic configuration based on these shells is still often used (e.g., Na as 2.8.1).
However, this common way of talking about shells has the potential to mislead learners. Students can, and sometimes do, develop the alternative conception that atoms have actual physical shells of some kind, into which the electrons are located. The shells scientists refer to are abstractions, but may be misinterpreted as material entities, as actual shells. The use of anthropomorphic language, that is that the electrons "sit in the shells", whilst helping to make the abstract ideas familiar and so perhaps comfortable, can reinforce this. After all, it is difficult to sit in empty space without support.
The subatomic grand prix?
Dr Finch offers her audience an analogy for the synchrotron: the electrons "are zipping around. I like to think of it kind of like a racetrack." Analogy is another common technique used by teachers and other communicators to help make the unfamiliar familiar.
Dr Finch refers to the popularity of the Australian Formula 1 (F1) Grand Prix that takes place in Melbourne, and points out
"Now what these race enthusiasts don't know is that just a bit further out of the city we have a race track that is operating six days a week that is arguably far more impressive.
That's right, it is the science donut. The difference is that instead of having F1s doing about 300 km an hour, we have electrons zipping around at the speed of light. That's about 300 thousand km per second.
Dr Emily Finch talking on Ockham's Razor
There is an interesting slippage – perhaps a deliberate rhetoric flourish – from the synchrotron being "kind of like a racetrack" (a simile) to being "a race track" (a metaphor). Although racing electrons lacks a key attraction of an F1 race (different drivers of various nationalities driving different cars built by competing teams presented in different livery – whereas who cares which of myriad indistinguishable electrons would win a race?) that does not undermine the impact of the mental imagery encouraged by this analogy.
This can be understood as an analogy rather than just a simile or metaphor as Dr Finch maps out the comparison:
target concept
analogue
a synchotron
a racetrack
operates six days a week
[Many in the audience would have known that the Melbourne Grand Prix takes place on a 'street circuit' that is only set up for racing one weekend each year.]
racing electrons
racing 'F1s' (i.e., Grand Prix cars)
at the speed of light
at about 300 km an hour
An analogy between the Australian Synchrotron and the Melbourne Grand Prix circuit
So, here is an attempt to show how science has something just like the popular race track, but perhaps even more impressive – generating speeds orders of magnitude greater than even Lewis Hamilton could drive.
They seem to like their F1 comparisons at the Australian Synchrotron. I found another ABC programme ('The Science Show') where Nobel Laureate "Brian Schmidt explains, the synchrotron is not being used to its best capability",
"the analogy here is that we invested in a $200 million Ferrari and decided that we wouldn't take it out of first gear and do anything other than drive it around the block. So it seems a little bit of a waste"
Brian Schmidt (Professor of Astronomy, and Vice Chancellor, at Australian National University)
A Ferrari being taken for a spin around the block in Melbourne (Image by Lee Chandler from Pixabay )
How fast?
But did Dr Finch suggest there that the electrons were travelling at the speed of light? Surely not? Was that a slip of the tongue?
"So, we bake our electrons fresh in-house using an electron gun. So, this works like an old cathode ray tube that we used to have in old TVs. So, we have this bit of tungsten metal and we heat it up and when it gets red hot it shoots out electrons into a vacuum. We then speed up the electrons, and once they leave the electron gun they are already travelling at about half the speed of light. We then speed them up even more, and after twelve metres, they are already going at the speed of light….
And it is at this speed that we shoot them off into a big ring called the booster ring, where we boost their energy. Once their energy is high enough we shoot them out again into another outer ring called the storage ring."
Dr Emily Finch talking on Ockham's Razor
So, no, the claim is that the electrons are accelerated to the speed of light within twelve metres, and then have their energy boosted even more.
But this is contrary to current physics. According to the currently accepted theories, and specifically the special theory of relativity, only entities which have zero rest mass, such as photons, can move at the speed of light.
Electrons have a tiny mass by everyday standards (about 0.000 000 000 000 000 000 000 000 001 g), but they are still 'massive' particles (i.e., particles with mass) and it would take infinite energy to accelerate a single tiny electron to the speed of light. So, given our current best understanding, this claim cannot be right.
I looked to see what was reported on the website of the synchrotron itself.
The electron beam travels just under the speed of light – about 299,792 kilometres a second.
Strictly the electrons do not travel at the speed of light but very nearly the speed of light.
The speed of light in a vacuum is believed to be 299 792 458 ms-1 (to the nearest metre per second), but often in science we are working to limited precision, so this may be rounded to 2.998 ms-1 for many purposes. Indeed, sometimes 3 x 108 ms-1 is good enough for so-called 'back of the envelope' calculations. So, in a sense, Dr Finch was making a similar approximation.
But this is one approximation that a science teacher might want to avoid, as electrons travelling at the speed of light may be approximately correct, but is also thought to be physically impossible. That is, although the difference in magnitude between
(i) the maximum electron speeds achieved in the synchrotron, and
(ii) the speed of light,
might be a tiny proportional difference – conceptually the distinction is massive in terms of modern physics. (I imagine Dr Finch is aware of all this, but perhaps her background in geology does not make this seem as important as it might appear to a physics teacher.)
Dr Finch does not explicitly say that the electrons ever go faster than the speed of light (unlike the defence lawyer in a murder trial who claimed nervous impulses travel faster than the speed of light) but I wonder how typical school age learners would interpret "they are already going at the speed of light….And it is at this speed that we shoot them off into a big ring called the booster ring, where we boost their energy". I assume that refers to maintaining their high speeds to compensate for energy transfers from the beam: but only because I think Dr Finch cannot mean accelerating them beyond the speed of light. 3
The big doughnut
After the reference to how "we bake our electrons fresh in-house", Dr Finch explains
And so it is these two rings, these inner and outer rings, that give the synchrotron its nick name, the science donut. Just like two rings of delicious baked electron goodness…
So, just to give you an idea of scale here, this outer ring, the storage ring, is about forty one metres across, so it's a big donut."
So, there is something of an extended metaphor here. The doughnut is so-called because of its shape, but this doughnut (a bakery product) is used to 'bake' electrons.
If audience members were to actively reflect on and seek to analyse this metaphor then they might notice an incongruity, perhaps a mixed metaphor, as the synchrotron seems to shift from being that which is baked (a doughnut) to that doing the baking (baking the electrons). Perhaps the electrons are the dough, but, if so, they need to go into the oven.
But, of course, humans implicitly process language in real time, and poetic language tends to be understood intuitively without needing reflection. So, a trope such as this may 'work' to get across the flavour (sorry) of an idea, even if under close analysis (by our pedantic science teacher again) the metaphor appears only half-baked.
Perverting the electrons
Dr Finch continued
"Now the electrons like to travel in straight lines, so to get them to go round the rings we have to bend them using magnets. So, we defect the electrons around the corners [sic] using electromagnetic fields from the magnets, and once we do this the electrons give off a light, called synchrotron light…
Dr Emily Finch talking on Ockham's Razor
Now electrons are not sentient and do not have preferences in the way that someone might prefer to go on a family trip to the local synchrotron rather than a Formula 1 race. Electrons do not like to go in straight lines. They fit with Newton's first law – the law of inertia. An electron that is moving ('travelling') will move ('travel') in a straight line unless there is net force to pervert it. 4
If we describe this as electrons 'liking' to travel in straight lines it would be just as true to say electrons 'like' to travel at a constant speed. Language that assigns human feelings and motives and thoughts to inanimate objects is described as anthropomorphic. Anthropomorphism is a common way of making the unfamiliar familiar, and it is often used in relation to molecules, electrons, atoms and so forth. Sadly, when learners pick up this kind of language, they do not always appreciate that it is just meant metaphorically!
"This synchrotron light is brighter than a million suns, and we capture it using special equipment that comes off that storage ring.
And this equipment will focus and tune and shape that beam of synchrotron light so we can shoot it at samples like a LASER."
Dr Emily Finch talking on Ockham's Razor
Whether the radiation is 'captured' is a moot point, as it no longer exists once it has been detected. But what caught my attention here was the claim that the synchrotron radiation was brighter than a million suns. Not because I necessarily thought this bold claim was 'wrong', but rather I did not understand what it meant.
The statement seems sensible at first hearing, and clearly it means qualitatively that the radiation is very intense. But what did the quantitative comparison actually mean? I turned again to the synchrotron webpage. I did not find an answer there, but on the site of a UK accelerator I found
"These fast-moving electrons produce very bright light, called synchrotron light. This very intense light, predominantly in the X-ray region, is millions of times brighter than light produced from conventional sources and 10 billion times brighter than the sun."
Sunlight spreads out and its intensity drops according to an inverse square law. Move twice as far away from a sun, and the radiation intensity drops to a quarter of what it was when you were closer. Move to ten times as far away from the sun than before, and the intensity is 1% of what it was up close.
The synchrotron 'light' is being shaped into a beam "like a LASER". A LASER produces a highly collimated beam – that is, the light does not (significantly) spread out. This is why football hooligans choose LASER pointers rather than conventional torches to intimidate players from a safe distance in the crowd.
Comparing light with like
This is why I do not understand how the comparison works, as the brightness of a sun depends how close you are too it – a point previously discussed here in relation to NASA's Parker solar probe (NASA puts its hand in the oven). If I look out at the night sky on a clear moonlight night then surely I am exposed to light from more "than a million suns" but most of them are so far away I cannot even make them out. Indeed there are faint 'nebulae' I can hardly perceive that are actually galaxies shining with the brightness of billions of suns. 5 If that is the comparison, then I am not especially impressed by something being "brighter than a million suns".
How bright is the sun? it depends which planet you are observing from. (Images by AD_Images and Gerd Altmann from Pixabay)
We are told not to look directly at the sun as it can damage our eyes. But a hypothetical resident of Neptune or Uranus could presumably safely stare at the sun (just as we can safely stare at much brighter stars than our sun because they are so far away). So we need to ask :"brighter than a million suns", as observed from how far away?
How bright is the sun? That depends on viewing conditions (Image by UteHeineSch from Pixabay)
Even if referring to our Sun as seen from the earth, the brightness varies according to its apparent altitude in the sky. So, "brighter than a million suns" needs to be specified further – as perhaps "more than a million times brighter than the sun as seen at midday from the equator on a cloudless day"? Of course, again, only the pedantic science teacher is thinking about this: everyone knows well enough what being brighter than a million suns implies. It is pretty intense radiation.
Applying the technology
Dr Finch went on to discuss a couple of applications of the synchrotron. One related to identifying pigments in art masterpieces. The other was quite timely in that it related to investigating the infectious agent in COVID.
"Now by now you have probably seen an image of the COVID virus – it looks like a ball with some spikes on it. Actually it kind of looks like those massage balls that your physio makes you buy when you turn thirty and need to to ease all your physical ailments that you suddenly have."
Dr Emily Finch talking on Ockham's Razor
Coronavirus particles and massage balls…or is it… (Images by Ulrike Leone and Daniel Roberts from Pixabay)
Again there is an attempt to make the unfamiliar familiar. These microscopic virus particles are a bit like something familiar from everyday life. Such comparisons are useful where the everyday object is already familiar.
By now I've seen plenty of images of the coronavirus responsible for COVID, although I do not have a physiotherapist (perhaps this is a cultural difference – Australians being so sporty?) So, I found myself using this comparison in reverse – imagining that the "massage balls that your physio makes you buy" must be like larger versions of coronavirus particles. Having looked up what these massage balls (a.k.a. hedgehog balls it seems) look like, I can appreciate the similarity. Whether the manufacturers of massage balls will appreciate their products being compared to enormous coronavirus particles is, perhaps, another matter.
Work cited:
Taber, K. S., Billingsley, B., Riga, F., & Newdick, H. (2015). English secondary students' thinking about the status of scientific theories: consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world – or just 'an idea someone has'. The Curriculum Journal, 1-34. doi: 10.1080/09585176.2015.1043926
Notes:
1 At least, depending how we understand 'thinking'. Clearly there are cognitive processes at work even when we continue a conversation 'on auto pilot' (to employ a metaphor) whilst consciously focusing on something else. Only a tiny amount of our cognitive processing (thinking?) occurs within conscousness where we reflect and deliberate (i.e., explicit thinking?) We might label the rest as 'implicit thinking', but this processing varies greatly in its closeness to deliberation – and some aspects (for example, word recognition when listening to speech; identifying the face of someone we see) might seem to not deserve the label 'thinking'?
2 Of course the evidence for some ideas becomes so overwhelming that in principle we treat some theories as certain knowledge, but in principle they remain provisional knowledge. And the history of science tells us that sometimes even the most well-established ideas (e.g., Newtonian physics as an absolutely precise description of dynamics; mass and energy as distinct and discrete) may need revision in time.
3 Since I began drafting this article, the webpage for the podcast has been updated with a correction: "in this talk Dr Finch says electrons in the synchrotron are accelerated to the speed of light. They actually go just under that speed – 99.99998% of it to be exact."
4 Perversion in the sense of the distortion of an original course
5 The term nebulae is today reserved for clouds of dust and gas seen in the night sky in different parts of our galaxy. Nebulae are less distinct than stars. Many of what were originally identified as nebulae are now considered to be other galaxies immense distances away from our own.
One of the recurring themes in this blog is the way science is communicated in teaching and through media, and in particular the role of language choices, in effective communication.
I was listening to a podcast of the BBC Science in Action programme episode 'Radioactive Red Forest'. The item that especially attracted my attention (no, not the one about teaching fish to do sums) was summarised on the website as:
"Understanding the human genome has reached a new milestone, with a new analysis that digs deep into areas previously dismissed as 'junk DNA' but which may actually play a key role in diseases such as cancer and a range of developmental conditions. Karen Miga from the University of California, Santa Cruz is one of the leaders of the collaboration behind the new findings."
Website description of an item on 'Science in Action'
They've really sequenced the human genome this time
The introductory part of this item is transcribed below.
Being 'once a science teacher, always a science teacher' (in mentality, at least), I reflected on how this dialogue is communicating important ideas to listeners. Before I comment in any detail, you may (and this is entirely optional, of course) wish to read through and consider:
What does a listener (reader) need to know to understand the intended meanings in this text?
What 'tactics', such as the use of figures of speech, do the speakers use to support the communication process?
Roland Pease (Presenter): "Good news! They sequenced, fully sequenced, the human genome.
'Hang on a minute' you cry, you told us that in 2000, and 2003, and didn't I hear something similar in 2013?' Well, yes, yes, and yes, but no.
A single chromosome stretched out like a thread of DNA could be 6 or 8 cm long. Crammed with three hundred million [300 000 000] genetic letters. But to fit one inside a human cell, alongside forty five [45] others for the complete set, they each have to be wound up into extremely tight balls. And some of the resulting knots it turns out are pretty hard to untangle in the lab. and the genetic patterns there are often hard to decode as well. Which is what collaboration co-leader Karen Miga had to explain to me, when I also said 'hang on a minute'."
Karen Miga: "The celebrated release of the finished genome back in 2003 was really focused on the portions that we could at the time map and assemble. But there were big persistent gaps. Roughly about two hundred million [200 000 000] bases long that were missing. It was roughly eight percent [8%] of the genome was missing."
"And these were sort of hard to get at bits of genome, I mean are they like trying to find a coin in the bottom of your pocket that you can't quite pull out?"
"These regions are quite special, we think about tandem repeats or pieces of sequences that are found in a head-to-tail orientation in the genome, these are corners of our genome where this is just on steroids, where we see a tremendous amount of tandem repeats sometimes extending for ten million [10 000 000] bases. They are just hard to sequence, and they are hard to put together correctly and that was – that was the wall that the original human genome project faced."
Introduction to the item on the sequencing of what was known as 'junk DNA' in the (a) human genome
I have sketched out a kind of 'concept map' of this short extract of dialogue:
A mapping of the explicit connections in the extract of dialogue (ignoring connections and synonyms that a knowledgeable listener would have available for making sense of the talk)
In educational settings, teachers' presentations are informed by background information about the students' current levels of knowledge. In particular, teachers need to be aware of the 'prerequisite knowledge' necessary for understanding their presentations. If you want to be understood, then it is important your listeners have available the ideas you will be relying on in your account.
A scientist speaking to the public, or a journalist with a public audience, will be disadvantaged in two ways compared to the situation of a teacher. The teacher usually knows about the class, and the class is usually not as diverse as a public audience. There might be a considerable diversity of knowledge and understanding among the members of, say, the 13-14 year old learners in one school class, or the first year undergraduates on a university course – but how much more variety is found in the readership of a popular science magazine or the audience of a television documentary or radio broadcast.
Here are some key concepts referenced in the brief extract above:
bases
cells
chromosome
DNA
sequencing
tandem repeats
the human genome
To follow the narrative, one needs to appreciate relationships among these concepts (perhaps at least that chromosomes are found in cells; and comprised of DNA, the structure of which includes a number of different components called bases, the ordering of which can be sequenced to characterise the particular 'version' of DNA that comprises a genome. 1 ) Not all of these ideas are made absolutely explicit in the extract.
The notion of tandem repeats requires somewhat more in-depth knowledge, and so perhaps the alternative offered – tandem repeats or pieces of sequences that are found in a head to tail orientation in the genome – is intended to introduce this concept for those who are not familiar with the topic in this depth.
The complete set?
The reference to "A single chromosome stretched out…could be 6 or 8 cm long…to fit one inside a human cell, alongside forty five others for the complete set…" seems to assume that the listener will already know, or will readily appreciate, that in humans the genetic material is organised into 46 chromosomes (i.e., 23 pairs).
Arguably, someone who did not know this might infer it from the presentation itself. Perhaps they would. The core of the story was about how previous versions of 'the' [see note 1] human genome were not complete, and how new research offered a more complete version. The more background a listener had regarding the various concepts used in the item, the easier it would be to follow the story. The more unfamiliar ideas that have to be coordinated, the greater the load on working memory, and the more likely the point of the item would be missed.2
Getting in a tangle
A very common feature of human language is its figurative content. Much of our thinking is based on metaphor, and our language tends to be full [sic 3] of comparisons as metaphors, similes, analogies and so forth.
So, we can imagine 'a single chromosome' (something that is abstract and outside of most people's direct experience) as being like something more familiar: 'like a thread'. We can visualise, and perhaps have experience of, threads being 'wound up into extremely tight balls'. Whether DNA strands in chromosomes are 'wound up into extremely tight balls' or are just somewhat similar to thread wound up into extremely tight balls is perhaps a moot point: but this is an effective image.
And it leads to the idea of knots that might be pretty hard to untangle. We have experience of knots in thread (or laces, etc.) that are difficult to untangle, and it is suggested that in sequencing the genome such 'knots' need to be untangled in the laboratory. The listener may well be visualising the job of untangling the knotted thread of DNA – and quite possibly imaging this is a realistic representation rather than a kind of visual analogy.
Indeed, the reference to "some of the resulting knots it turns out are pretty hard to untangle in the lab. and the genetic patterns there are often hard to decode as well" might seem to suggest that this is not an analogy, but two stages of a laboratory process – where the DNA has to be physically untangled by the scientists before it can be sequenced, but that even then there is some additional challenge in reading the parts of the 'thread' that have been 'knotted'.
Reading the code
In the midst of this account of the knotted nature of the chromosome, there is a complementary metaphor. The single chromosome is "crammed with three hundred million genetic letters". The 'letters' relate to the code which is 'written' into the DNA and which need to be decoded. An informed listener would know that the 'letters' are the bases (often indeed represented by the letters A, C, G and T), but again it seems to be assumed this does not need to be 'spelt out'. [Sorry.]
But, of course, the genetic code is not really a code at all. At least, not in the original meaning of a means of keeping a message secret. The order of bases in the chromosome can be understood as 'coding' for the amino acid sequences in different proteins but strictly the 'code' is, or at least was originally, another metaphor. 4
Hitting the wall
The new research had progressed beyond the earlier attempts to sequence the human genome because that project had 'faced a wall' – a metaphorical wall, of course. This was the difficulty of sequencing regions of the genome that, the listener is told, were quite special.
The presenter suggests that the difficulty of sequencing these special regions of "hard to get at bits of genome" was akin to" trying to find a coin in the bottom of your pocket that you can't quite pull out". This is presumably assumed to be a common experienced shared by, or at least readily visualised by, the audience allowing them to better appreciate just how "hard to get at" these regions of the genome are.
We might pause to reflect on whether a genome can actually have regions. The term region seems to have originally been applied to a geographical place, such as part of a state. So, the idea that a genome has regions was presumably first used metaphorically, but this seems such a 'natural' transfer, that the 'mapping' seems self-evident. If it was a live metaphor, it is a dead one now.
Similarly, the mapping of the sequences of fragments of chromosomes onto the 'map' of the genome seems such a natural use of the term may no longer seem to qualify as a metaphor.
Repeats on steroids
These special regions are those referred to above as having tandem repeats – so parts of a chromosome where particular base sequences repeat (sometimes a great many times). This is described as "pieces of sequences that are found in a head to tail orientation" – applying an analogy with an organism which is understood to have a body plan that has distinct anterior and posterior 'ends'.
Not only does the genome contain such repeats, but in some places there are a 'tremendous' number of these repeats occurring head to tail. These places are referred to as 'corners' of the genome (a metaphor that might seem to fit better with the place in a pocket where a coin might to be hard to dislodge – or perhaps associated with that wall), than with a structure said to be like a knotted, wound-up, ball of thread.
It is suggested that in these regions, the repeats of the same short base sequences can be so extensive that they continue for billions of bases. This is expressed through the simile that the tandem repeating "is just on steroids" – again an allusion to what is assumed to be a familiar everyday phenomenon, that is, something familiar enough to people listening to help then appreciate the technical account.
Many people in the audience will have experience of being on steroids as steroids are prescribed for a wide variety of inflammatory conditions – both acute (due to accidents or infections) and chronic (e.g., asthma). Yet these are corticosteroids and 'dampen down' (metaphorically, of course) inflammation. The reference here is to anabolic steroid use, or rather abuse, by some people attempting to quickly build up muscle mass. Although anabolic steroids do have clinical use, abusers may take doses orders of magnitude higher than those prescribed for medical conditions.
I suspect that whereas many people have personal experience or experience of close family being on corticosteroids, whereas anabolic steroid use is rarer, and is usually undertaken covertly – so the metaphor here lies on cultural knowledge of the idea of people abusing anabolic steroids leading to extreme physical and mood changes.
Making a good impression
That is not to suggest this metaphor does not work. Rather I would suggest that most listeners would have appreciated the intended message implied by 'on steroids', and moreover the speaker was likely able to call upon the metaphor implicitly – that is without stopping to think about how the metaphor might be understood.
Metaphors of this kind can be very effective in giving an audience a strong impression of the scientific ideas being presented. It is worth noting, though, that what is communicated is to some extent just that, an impression, and this kind of impressionist communication contrasts with the kind of technically precise language that would be expected in a formal scientific communication.
Language on steroids
Just considering this short extract from this one item, there seems to be a great deal going on in the communication of the science. A range of related concepts are drawn upon as (assumed) background and a narrative offered for why the earlier versions of the human genome were incomplete, and how new studies are producing more complete sequences.
Along the way, communication is aided by various means to help 'make the unfamiliar familiar' by using both established metaphors as well as new comparisons. Some originally figurative language (mapping, coding, regions) is now so widely used it has been adopted as literally referring to the genome. Some common non-specific metaphors are used (hitting a wall, hard to access corners), and some specific images (threads, knots and tangles, balls, head-tails) are drawn upon, and some perhaps bespoke comparisons are introduced (the coin in the pocket, being on steroids).
In this short exchange there is a real mixture of technical language with imagery, analogy, and metaphor that potentially both makes the narrative more listener-friendly and helps bridge between the science and the familiar everyday – at last when these figures of speech are interpreted as intended. This particular extract seems especially 'dense' in the range of ideas being orchestrated into the narrative – language on steroids, perhaps – but I suspect similar combinations of formal concepts and everyday comparisons could be found in many other cases of public communication of science.
An alternative concept map of the extract, suggesting how someone with some modest level of background in the topic might understand the text (filling in some implicit concepts and connections). How a text is 'read' always depends upon the interpretive resources the listener/reader brings to the text.
At least the core message was clear: Scientists have now fully sequenced the human genome.
Although, I noticed when I sought out the scientific publication that "the total number of bases covered by potential issues in the T2T-CHM13 assembly [the new research] is just 0.3% of the total assembly length compared with 8% for GRCh38 [The human genome project version]" (Nurk et al., 2022) , which, if being churlish, might be considered not entirely 'fully' sequenced. Moreover "CHM13 lacks a Y chromosome", which – although it is also true of half of the human population – might also suggest there is still a little more work to be done.
Work cited:
Nurk, S., Koren, S., Rhie, A., Rautiainen, M., Bzikadze, A. V., Mikheenko, A., . . . Phillippy, A. M.* (2022). The complete sequence of a human genome. Science, 376(6588), 44-53. doi:doi:10.1126/science.abj6987
Notes
1 We often talk of DNA as a substance, and a molecule of DNA as 'the' DNA molecule. It might be more accurate to consider DNA as a class of (many) similar substances each of which contains its own kind of DNA molecule. Similarly, there is not a really 'a' human genome – but a good many of them.
2 Working memory is the brain component where people consciously access and mentipulate information, and it has a very limited capacity. However, material that has been previously learnt and well consolidated becomes 'chunked' so can be accessed as 'chunks'. Where concepts have been integrated into coherent frameworks, the whole framework is accessed from memory as if a single unit of information.
3 Strictly only a container can be full – so, this is a metaphor. Language is never full -as we can always be more verbose! Of course, it is such a familiar metaphor that it seems to have a literal meaning. It has become what is referred to as a 'dead' metaphor. And that is, itself, a metaphor, of course.
4 Language changes over time. If we accept that much of human cognition is based on constructing new ways of thinking and talking by analogy with what is already familiar (so the song is on the 'top' of the charts and it is a 'long' time to Christmas, and a 'hard' rain is going to fall…) then language will grow by the adoption of metaphors that in time cease to be seen as metaphors, and indeed may change in their usage such that the original reference (e.g., as with electrical 'charge') may become obscure.
In education, teachers may read originally metaphorical terms in terms of teir new scientific meanings, whereas learners may understand the terms (electron 'spin', 'sharing' of electrons, …) in terms of the metaphorical/analogical source.
*This is an example of 'big science'. The full author list is:
Sergey Nurk, Sergey Koren, Arang Rhie, Mikko Rautiainen, Andrey V. Bzikadze, Alla Mikheenko, Mitchell R. Vollger, Nicolas Altemose, Lev Uralsky, Ariel Gershman, Sergey Aganezov, Savannah J. Hoyt, Mark Diekhans, Glennis A. Logsdon,p Michael Alonge, Stylianos E. Antonarakis, Matthew Borchers, Gerard G. Bouffard, Shelise Y. Brooks, Gina V. Caldas, Nae-Chyun Chen, Haoyu Cheng, Chen-Shan Chin, William Chow, Leonardo G. de Lima, Philip C. Dishuck, Richard Durbin, Tatiana Dvorkina, Ian T. Fiddes, Giulio Formenti, Robert S. Fulton, Arkarachai Fungtammasan, Erik Garrison, Patrick G. S. Grady, Tina A. Graves-Lindsay, Ira M. Hall, Nancy F. Hansen, Gabrielle A. Hartley, Marina Haukness, Kerstin Howe, Michael W. Hunkapiller, Chirag Jain, Miten Jain, Erich D. Jarvis, Peter Kerpedjiev, Melanie Kirsche, Mikhail Kolmogorov, Jonas Korlach, Milinn Kremitzki, Heng Li, Valerie V. Maduro, Tobias Marschall, Ann M. McCartney, Jennifer McDaniel, Danny E. Miller, James C. Mullikin, Eugene W. Myers, Nathan D. Olson, Benedict Paten, Paul Peluso, Pavel A. Pevzner, David Porubsky, Tamara Potapova, Evgeny I. Rogaev, Jeffrey A. Rosenfeld, Steven L. Salzberg, Valerie A. Schneider, Fritz J. Sedlazeck, Kishwar Shafin, Colin J. Shew, Alaina Shumate, Ying Sims, Arian F. A. Smit, Daniela C. Soto, Ivan Sović, Jessica M. Storer, Aaron Streets, Beth A. Sullivan, Françoise Thibaud-Nissen, James Torrance, Justin Wagner, Brian P. Walenz, Aaron Wenger, Jonathan M. D. Wood, Chunlin Xiao, Stephanie M. Yan, Alice C. Young, Samantha Zarate, Urvashi Surti, Rajiv C. McCoy, Megan Y. Dennis, Ivan A. Alexandrov, Jennifer L. Gerton, Rachel J. O'Neill, Winston Timp, Justin M. Zook, Michael C. Schatz, Evan E. Eichler, Karen H. Miga, Adam M. Phillippy
Some spider monkeys like a little something extra with "all this fruit"
Keith S. Taber
(Photograph by by Manfred Richter from Pixabay)
"oh heck, what am I going to do, I'm faced with all this fruit with no protein and I've got to be a spider monkey"
Primatologist Adrian Barnett getting inside the mind of a monkey
I was listening to an item on the BBC World Service 'Science in Action' programme/podcast (an episode called 'Climate techno-fix would worsen global malaria burden').
This included an item with the title:
Primatologist Adrian Barnett has discovered that spider monkeys in one part of the Brazilian Amazon seek out fruit, full of live maggots to eat. Why?
The argument was that the main diet of monkeys is usually fruit which is mostly very low in protein and fat. However, often monkeys include figs in their diet which are an exception, being relatively rich in protein and fats.
The spider monkeys in one part of the Amazon, however, seem to 'seek out' fruit that was infested with maggots – these monkeys appear to actively choose the infected fruits. These are the fruits a human would probably try to avoid: certainly if there were non-infested alternatives. Only a proportion of fruit on the trees are so infested, yet the monkeys consume a higher proportion of infested fruit and so seem to have a bias towards selecting fruit with maggots. At least that was what primatologist Dr Adrian Barnett's analysis found when he analysed the remains of half-eaten fruit that reached the forest floor.
The explanation suggested is that this particular area of forest has very few fig trees, therefore it seems these monkeys do not have ready access to figs, and it seems they instead get a balanced diet by preferentially picking fruit containing insect larvae.
Who taught the monkeys about their diet?
A scientific explanation of this might suggest natural selection was operating.
Even if monkeys had initially tended to avoid the infested fruit, if this then led to a deficient diet (making monkeys more prone to disease, or accidents, and less fertile) then any monkeys who supplemented the fruit content of their diet by not being so picky and eating some infested fruit (whether because of a variation in their taste preferences, or simply a variation in how careful they were to avoid spoilt fruit) would have a fitness advantage and so, on average, leave more offspring.
To the extent their eating habits reflected genetic make-up (even if this was less significant for variations in individual behaviour than contingent environmental factors) this would over time shift the typical behaviours in the population. Being willing to eat, or perhaps even enjoying, maggotty fruit was likely to be a factor in being fertile and fecund, so eventually eating infested fruit becomes the norm – at least as long as the population remains in a habitat that does not have other ready sources of essential dietary components. Proving this is what happened would be very difficult after the fact. But an account along these lines is consistent with our understanding of how behaviour tends to change.
An important aspect of natural selection is that it is an automatic process. It does not require any deliberation or even conscious awareness on behalf of the members of the population being subject to selection. Changes do not occur in response to any preference or purpose – but just reflect the extent to which different variants of a population match their environment.
This is just as well, as even though monkeys are primates, and so relatively intelligent animals, it seems reasonable to assume they do not have a formal concept of diet (rather, they just eat), and they are not aware of the essential need for fat and protein in the diet; nor of the dietary composition of fruit. Natural selection works because where there is variation, and differences in relative fitness, the fittest will tend to leave more offspring (as by fittest we simply mean those most able to leave offspring!)
Now he's thinking…
I was therefore a little surprised when the scientist being interviewed, Adrian Barnett, explained the behaviour:
"So, suddenly the monkey's full of, you know, squeaking the monkey equivalent of 'oh heck, what am I going to do, erm, I'm faced with all this fruit with no protein and I've got to be a spider monkey'."
Adrian Barnett speaking on Science in Action
At first hearing this sounds like anthropomorphism, where non-humans are assigned human feelings and cognitions.
Anthropomorphic language refers to non-human entities as if they have human experiences, perceptions, and motivations. Both non-living things and non-human organisms may be subjects of anthropomorphism. Anthropomorphism may be used deliberately as a kind of metaphorical language that will help the audience appreciate what is being described because of its similarly to some familiar human experience. In science teaching, and in public communication of science, anthropomorphic language may often be used in this way, giving technical accounts the flavour of a persuasive narrative that people will readily engage with. Anthropomorphism may therefore be useful in 'making the unfamiliar familiar', but sometimes the metaphorical nature of the language may not be recognised, and the listener/reader may think that the anthropomorphic description is meant to be taken at face value. This 'strong anthropomorphism' may be a source of alternative conceptions ('misconceptions') of science.
Why 'at first hearingthis seems like an example of anthropomorphism'? Well, Dr Barnett does not say the monkey actually has these thoughts but rather squeaks the monkey equivalent of these words. This leaves me wondering how we are to understand what the monkey equivalent actually is. I somehow suspect that whatever thoughts the monkey has they probably do not include any direct equivalents of either being a spider monkey or protein.
I am happy to accept the monkey has a concept somewhat akin to our fruit, as clearly the monkey is able to discriminate particular regularities in its environment that are associated with the behaviour of picking items from trees and eating them – regularities that we would class as fruit. It is interesting to speculate on what would be included in a monkey's concept map of fruit, were one able to induce a monkey to provide the data that might enable us to produce such a diagram. Perhaps there might be monkey equivalents of such human concepts as red and crunchy and mushy…but I would not be expecting any equivalents of our concepts of dietary components or nutritional value.
So, although I am not a primatologist, I wonder if the squeaking Dr Barnett heard when he was collecting for analysis the partially eaten fruit dropped by the spider monkeys was actually limited to the monkey equivalent of either "yummy, more fruit" or perhaps "oh, fruit again".
Can we be certain about something that happened half a million years ago?
Keith S. Taber
What was going on in Java when Homo erectus lived there? (Image by Kanenori from Pixabay )
About half a million years ago a hominid, of the Homo erectus species, living in Java took a shell and deliberately engraved a mark on it. Now, I was not there when this happened, so my testimony is second hand, but I can be confident about this as I was told by a scientist that she was sure that this definitely happened.
"…we knew for sure that it must have been made by Homo erectus"
But how can we be so sure about something alleged to have occurred so long ago?
"A long time ago [if not] in a galaxy far, far away…." the skull of a specimen of Homo erectus (Image by Mohamed Noor from Pixabay ) [Was this an inspiration for the Star Wars stormtrooper helmet?]
I doubt Fifi would be convinced.1 Fifi was a Y12 student (c.16 years old) interviewed as part of the LASAR project who had reservations about palaeontology as it did not provide certain scientific knowledge,
"I like fossils though, I think they're interesting but I don't think I'd really like [working as a palaeontologist]…I don't think you could ever really know unless you were there… There'll always be an element of uncertainty because no matter how much evidence you supply there will always be, like, doubt because of the fact that you were never there…there'll always be uncertainty."
Learners can have alternative conceptions of the nature of science, just as much as they often do for forces or chemical bonding or plant nutrition. They often think that scientific knowledge has been 'proved', and so is certain (e.g., Taber, Billingsley, Riga & Newdick, 2015). An area like palaeontology where direct observation is not possible may therefore seem to fall short of offering genuine scientific knowledge.
The uncertain nature of scientific knowledge
One key feature of the nature of science is that it seeks to produce general or theoretical knowledge of the natural world. That is, science is not just concerned with providing factual reports about specific events but with developing general accounts that can explain and apply to broad categories of objects and events. Such general and theoretical knowledge is clearly more useful than a catalogue of specific facts – which can never tell us about the next occasion or what might happen in hypothetical situations.
However, a cost of seeking such applicable and useful knowledge is that it can never be certain. It relies on our ways of classifying objects and events, the evidence we have collected so far, our ability to spot the most important patterns -and the deductions this might support. So, scientific knowledge is always provisional in the sense that it is open to revision in response to new data, or new ways of thinking about existing data as evidence.
Yet often reports of science in the media give the impression that science has made absolute discoveries. Some years ago I wrote about the tendency in science documentaries for the narrative to be driven by links that claimed "...this could only mean…" when we know that in science the available data always underdetermines theory (Taber, 2007). Or, to put it another way, we could always think up other ways of explaining the data. Sometimes these alternatives might seem convoluted and unlikely, but if we can suggest a possible (even when unconvincing) alternative, then the available data can never "only mean" any one particular proposed interpretation.
"One of the most exciting episodes of palaeoanthropology was the find of the first transitional form, the Pithecanthropus erectus, by the Dutchman Eugène Dubois in Java during 1891-1892. …Besides the human remains, Dubois made a large collection of vertebrate fossils, mostly of mammals, now united in the so-called Dubois Collection."
de Vos, 2004
The Java man species, Pithecanthropus erectus (an upright ape/mokey-man), was later renamed as Homo erectus, the upright man.
On an edition of BBC Radio 4's 'In Our Time' taking 'Homo erectus' as its theme, Prof. Joordens explained how some fossil shells collected by Dubois as part of the context of the hominid fossils had remained in storage for over a century ("The shells had been, well, shelved…"!), before a graduate student set out to photograph them all for a thesis project. This led to the discovery that one of the shells appeared to have been engraved.
This could only mean one thing…
This is what Prof. Joordens told the host, Melvyn Bragg,
"One shell that had a very strange marking that we could not understand how it ended up there…
It was geometric, like a W, and this is of course something that animals don't produce. We had to conclude that it must have been made by Homo erectus. And it must have been a very deliberate marking because of, we did experimental research trying to replicate it, and then we actually found it was quite hard to do. Because, especially fresh shells, they have a kind of organic exterior, and it's hard to push some sharp objects through and make those lines, so that was when we knew for sure that it must have been made by Homo erectus."
We may consider this claim to be composed of a number of components, such as:
There is a shell with some 'very strange' markings
The shell was collected in Java in the nineteenth century
The shell had the markings when first collected
The markings were not caused by some natural phenomenon
The markings were deliberate not accidental
The markings were made by a specimen of Homo erectus
A sceptic might ask such questions as
How can we be sure this shell was part of the original collection? Could it have been substituted by mistake or deliberately?
How do we know the marks were not made more recently? perhaps by someone in the field in Java, or during transit form Java to the Netherlands, or by someone inspecting the collection?
Given that even unusual markings will occur by chance occasionally, how can we be certain these markings were deliberate? Does the mark really look like a 'W 'or might that be an over-interpretation. 2
And so forth.
It is worth bearing in mind that no one noticed these markings in the field, or when the collection was taken back to the Netherlands – indeed Prof. Joordens noted she had carried the shell around in her backpack (could that have been with an open penknife?) unaware of the markings
Of course, Prof. Joordens may have convincing responses to many of these questions – but a popular radio show is not the place to detail all the argument and evidence. Indeed, I found a report in the top journal Nature ('Homo erectus at Trinil on Java used shells for tool production and engraving') by Prof. Joordens and her team 3, claiming,
"One of the Pseudodon shells, specimen DUB1006-fL, displays a geometric pattern of grooves on the central part of the left valve [*]. The pattern consists, from posterior to anterior, of a zigzag line with three sharp turns producing an 'M' shape, a set of more superficial parallel lines, and a zigzag with two turns producing a mirrored 'N' shape. Our study of the morphology of the zigzags, internal morphology of the grooves, and differential roughness of the surrounding shell area demonstrates that the grooves were deliberately engraved and pre-date shell burial and weathering"
It may seem most likely that the markings were made by a Homo erectus, as no other explanation so far considered fits all the data, but theory is always under-determined – one can never be certain another scenario might be found which also fits the known facts.
Strictly, Prof. Joordens' contradicts herself. She claims the marks are "something that animals don't produce" and then claims an animal is responsible. She presumably meant that no non-hominid animal makes such marks. Even if we accept that (and, as they say, absence of evidence is not evidence of absence 4), can we be absolutely certain some other hominid might not have been present in Java at the time, marking the odd shell? As the 'In Our Time' episode discussed, Homo erectus often co-existed with other hominids.
Probably not, but … can we confidently say absolutely, definitely, not?
As Fifi might say: "I don't think you could ever really know unless you were there".
My point is not that I think Prof. Joordens is wrong (she is an expert, so I think she is likely correct), but just that her group cannot be absolutely certain. When Prof. Joordens says she knows for sure I assume (because she is a scientist, and I am a scientist) that this means something like "based on all the evidence currently available, our best, and only convincing, interpretation is…" Unfortunately lay people often do not have the background to insert such provisos themselves, and so often hear such claims literally – science has proved its case, so we know for sure. Where listeners already think scientific knowledge is certain, this misconception gets reinforced.
Meanwhile, Prof. Joordens continues her study of hominids in Java in the Studying Homo erectus Lifestyle and Location project (yes, the acronym is SHeLL).
Joordens, J., d'Errico, F., Wesselingh, F. et al. Homo erectus at Trinil on Java used shells for tool production and engraving. Nature 518, 228-231 (2015). https://doi.org/10.1038/nature13962
Taber, K. S., Billingsley, B., Riga, F., & Newdick, H. (2015). English secondary students' thinking about the status of scientific theories: consistent, comprehensive, coherent and extensively evidenced explanations of aspects of the natural world – or just 'an idea someone has'. The Curriculum Journal, 1-34. doi: 10.1080/09585176.2015.1043926
Notes
1 As is usual practice in such research, Fifi is an assumed name. Fifi gave permission for data she contributed to the research to be used in publications on the assumption it would be associated with a pseudonym. (See: 'Using pseudonyms in reporting research'.)
2 No one is suggesting that the hominid deliberately marked the shell with a letter of the Roman alphabet, just that s/he deliberately made a mark that represented a definite and deliberate pattern. Yet human beings tend to spot patterns in random data. Could it just be some marks that seem to fit into a single pattern?
4 At one time there was no evidence of 'noble' gases reacting. At one time there was no evidence of ozone depletion. At one time there was no evidence of superconductivity. At one time there was no evidence that the blood circulates around the body. At one time there was no evidence of any other planet having moons. At one time there was no evidence of protons being composed of even more fundamental particles. At one time there was no evidence of black holes. At one time there was no evidence that smoking tobacco was harmful. At one time there was no evidence of … [fill in your choice scientific discovery!]
Scientific literacy and desk accessories in science fiction
Keith S. Taber
Is the principle of conservation of mass that is taught in school science falsified all the time?
I am not really a serious sci-fi buff, but I liked Star Trek (perhaps in part because it was the first television programme I got to see in colour 1) and I did enjoy Blakes7 when it was broadcast by the BBC (from 1978-1981).
Logo of the BBC television series 'Blakes7' with (a) home desk equipment or (b) manual control lever for the most advanced spaceship in the galaxy (Image by Francis Ray from Pixabay).
Blakes7 was made with the same kind of low budget production values of Dr Who of the time. Given that space scenes in early episodes involved what seemed to be a flat image of a spacecraft moving across a star field with no sense of depth or perspective (for later series someone had built a model), and in one early episode the crew were clearly given angle-poise lamps to control the craft, it was certainly not a case of 'no expense spared'. So, it was never quite clear if the BBC budget had also fallen short of a possessive apostrophe in the show title credits or Blakes7 was to be read in some other way.
After all, it was not made explicit who was part of Blake's 7 if that was what the title meant, and no one referred to "Blake's 7" in the script (perhaps reflecting how the doctor in Dr Who was not actually called Dr Who?).
The Blakes7 team on the flight desk of the Liberator – which was the most advanced spaceship in the galaxy (and was, for plot purposes, conveniently found drifting in space without a crew) – at least until they forgot to clean the hull once too often and it corroded away while they were on an away mission.
Blake's group was formed from a kind of prison break and so Blake was something of a 'rough-hero' – but not as much as his sometime unofficial lieutenant, sometime friend, sometime apparent rival, Avon, who seemed to be ruled by self-interest (at least until the script regularly required some act of selfless heroism from him). 'Rough-heroes' are fictional characters presented in the hero role but who have some traits that the audience are likely to find morally questionable if not repugnant.
As well as Blake (a rebel condemned as a traitor, having 'recovered' from brainwashing-supported rehabilitation to rebel again) and Avon (a hacker convicted of a massive computer fraud intended to make himself extremely rich) the rest of the original team were a smuggler, a murderer and a petty thief, to which was added a terrorist (or freedom fighter if you prefer) picked up on an early mission. That aside, they seemed an entirely reasonable and decent bunch, and they set out to rid the galaxy of 'The Federation's tyrannical oppression. At least, that was Blake's aspiration even if most of his companions seemed to see this as a stop-gap activity till they had decided on something with more of a long-term future.
At the end of one season, where the fight with the Federation was temporarily put aside to deal with an intergalactic incursion, Blake went AWOL (well, intergalactic wars can be very disruptive) and was assumed dead/injured/lost/captured/?… for much of the remaining run without affecting the nature of the stories too much.
Among its positive aspects for its time were strong (if not exactly model) roles for women. The main villain, Servalan, was a woman – Supreme Commander of the Federation security forces (and later Federation president).
As the ruthless Supreme Commander of the Federation security forces, Servalan got to wear whatever she liked (a Kid Creole, or Mel and Kim, look comes to mind here) and could insist her staff wore hats that would not upstage hers
In Blake's original team (i.e., 7?), his pilot is a woman. (Reflecting other SciFi series, the spacecraft used by Blakes7 require n crew members to operate effectively, where n is an integer that varies between 0 and 6 depending on the specific plot requirements of an episode.) In a later series, after Avon has taken over the role of 'ipso facto leader-among-equals', the group recruits a female advanced weapons designer/technologist and a female sharpshooter.
The Blakes7 team later in the run. (Presumably they are checking the monitor and having a quick recount.) Was Soolin (played by Glynis Barber, far right) styled as a subtle reference to the 'Seven Samurai'?
When I saw Blakes7 was getting a rerun recently I re-watched the series I had not seen since it was first aired. Despite very silly special effects, dodgy story-lines, and morally questionable choices (the series would make a great focus for a philosophy class) the interactions between the main characters made it an enjoyable watch.
But, it is not science
Of course, the problem with science fiction is that it is fiction, not science. Star Trek may have prided itself on seeking to at least make the science sound feasible, but that is something of an outlier in the genre.
Egrorian and his young assistant Pinder (unfortunately prematurely aged somewhat by a laboratory mishap) show Avon and Vila around their lab.
This is clear, for example, in an episode called 'Orbit' where Avon discuses the tachyon funnel, an 'ultimate weapon', with Egrorian, a renegade scientist. Tachyons are hypothetical particles that travel faster than the speed of light. The theory of special relatively suggests the speed of light is the theoretical maximum speed anything can have, but some other theories suggest tachyons may exist in some circumstances. As always in science, theories that are widely accepted as our current best understanding of some aspect of nature (e.g., relativity) are still open to modification or replacement if new evidence is found that suggests this is indicated.
In the Blakes7 universe, there seemed to be a surprisingly high frequency of genius scientists/engineers who had successfully absconded from the tyrannical and paranoid Federation with sufficient resources to build private research facilities on various obscure deserted planets. Although these bases are secret and hidden away, and the scientists concerned have normally been missing for years or even decades, it usually transpires that the Blakes7 crew and the Federation manage to locate any particular renegade scientist during the same episode.
This is part of the exchange between this particular flawed genius scientist and our flawed and reluctant 'rough hero', Kerr Avon:
Egrorian: You've heard of Hoffal's radiation?
Avon: No.
Ah… Hoffal had a unique mind. Over a century ago he predicted most of the properties that would be found in neutron material.
Neutron material?
Material from a neutron star. That is a… a giant sun which has collapsed and become so tightly compressed that its electrons and protons combine, making neutrons.
I don't need a lecture in astrophysics. [But presumably the scriptwriter felt the audience would need to be told this.]
When neutrons are subjected to intense magnetic force, they form Hoffal's radiation. Poor Pinder [Egrorian's lab. assistant] was subjected for less than a millionth of a second. He aged 50 years in as many seconds. …
So neutrons are part of the tachyon funnel.
Um, eight of them … form the core of the accelerator.
Now, for anyone with any kind of science background such dialogue stretches credibility. Chadwick discovered the neutron in everyday matter in 1932, so the neutron's properties could be explored without having to obtain samples from a neutron star – which would certainly be challenging. When bound in nuclei, neutrons (which are electrically neutral, thus the name, and so not usually affected by magnetic fields) are stable.
Thinking at the scale of a neutron
However, any suspension of disbelief (which fiction demands, of course) was stretched past breaking point at the end of this exchange. Not only were the generally inert neutrons the basis of a weapon that could destroy whole worlds – but the core of the accelerator was formed of, not a neutron star, nor a tonne of 'neutron matter', but eight neutrons (i.e., one for each member of Blake's 7 with just a few left over?)
That is, the intensely destructive beam of radiation that could destroy a planet from a distant solar system was generated by subjecting to a magnetic field: a core equivalent to (the arguably less interesting) half of a single oxygen atomic nucleus.
Warning – keep this away from strong magnetic fields if you value your planet! (Image by Gerd Altmann from Pixabay )
Now free neutrons (that is, outside of an atomic nuclei – or neutron star) are unstable, and decay on a timescale of around a quarter of an hour (that is, the half-life is of this order – following the exponential decay familiar with other kinds of radioactivity), to give a proton, an electron and a neutrino. The energy 'released' in this process is significant on the scale of a subatomic particle: 782 343 eV or nearly eight hundred thousand eV.
Eight hundred thousand seems a very large number, but the unit here is electron volt, a unit used for processes at this submicroscopic scale. (An eV is the amount of work that is done when one single electron is moved though a potential difference of 1v – this is about 1.6 x10-19 J). In the more familiar units of joules, this is about 1.25 x 10-13 J. That is,
0.000 000 000 000 125 J
To boil enough water at room temperature to make a single cup of tea would require about 67 200 J. 2 So, if the energy from decaying neutrons were used to boil the water, it would require the decay of about
538 000 000 000 000 000 neutrons.3
That is just to make one cup of tea, so imagine how many more neutrons would have to decay to provide the means to destroy a planet. Certainly, one would imagine,
more than 8.
E=mc2
Now since Einstein (special relativity, again), mass and energy have been considered to have an equivalence. It is commonly thought that mass can be converted to energy and the equation E=mc2 tells you how much of one would be converted to the other: how many J per kg or kg per J. (Spoiler alert – this is not quite right.)
In that way of thinking, the energy released by a free neutron when it decays is due to a tiny part of the neutrino's mass being converted to energy.
The neutron's mass defect
The mass (or so called 'rest mass') of a neutrino is about 1.67 x 10-27 kg. In the usual mode of decay the neutrino gives rise to a proton (which is nearly, but not quite, as heavy as a neutron), an electron (which is much lighter), and a neutrino (which is considered to have zero rest mass.)
Before decay
Rest mass / 10-31 kg
After decay
Rest mass / 10-31 kg
neutron
16 749.3
proton
16 726.2
electron
9.1
neutrino
–
total
16 749.3
16 735.3
[rest] mass defect in neutrino decay
So, it seems like some mass has disappeared. (And this is the mass sometimes said to have been converted into the released energy.) This might lead us to ask the question of whether Hoffal's discovery was a way to completely annihilate neutrons, so that instead of a tiny proportion of their mass being converted to energy as in neutron decay – all of it was.
Mass as latent energy?
However, when considered from the perspective of special relativity, it is not that mass is being converted to energy in processes such as neutron decay, but rather that mass and energy are considered as being different aspects of something more unified -'mass-energy' if you like. Energy in a sense carries mass, and mass in a sense is a manifestation of energy. The table above may mislead because it only refers to 'rest mass' and that does not tell us all we need to know.
When the neutron decays, the products move apart, so have kinetic energy. According to the principle of mass-energy equivalence there is always a mass equivalence of any energy. So, in relativity, a moving object has more mass than when it is at rest. That is, the 'mass defect' table shows what the mass would be if we compared a motionless neutron with motionless products, not the actual products.
The theory of special relativity boldly asserts that mass and energy are not the independent quantities they were once thought to be. Rather, they are two measures of a single quantity. Since that single quantity does not have its own name, it is called mass-energy, and the relationship between its two measures is known as mass-energy equivalence. We may regard c2 as a conversion factor that enables us to calculate one measurement from the other. Every mass has an energy-equivalent and every energy has a mass-equivalent. If a body emits energy to its surroundings it also emits a quantity of mass equivalent to that energy. The surroundings acquire both the energy and mass in the process.
Treptow, 2005, p.1636
So, rather than thinking mass has been converted to energy, it may be more appropriate to think that the mass of a neutron has a certain (latent) energy associated with it, and that, after decay, most of this energy is divided between products (according to their rest masses), but a small proportion has been converted to kinetic energy (which can be considered to have a mass equivalence).
So, whenever any process involves some kind of energy change, there is an associated change in the equivalent masses. Every time you boil the kettle, or go up in an elevator, there is a tiny increase of mass involved – the hot water is heavier than when it was cold; you are heavier than when you were at a lower level. When you lie down or burn some natural gas, there is a tiny reduction in mass (you weigh less lying down; the products of the chemical reaction weigh less than the reactants).
How much heavier is hot water?
Only in nuclear processes does the energy change involved become large enough for any change in mass to be considered significant. In other processes, the changes are so small, they are insignificant. The water we boiled earlier to make a cup of tea required 67 200J of energy, and at the end of the process the water would not just be hotter, but also heavier by about
0.000 000 000 000 747 kg
0r about 0.000 000 000 75 g. That is easy to calculate 4, but not so easy to notice.
Is mass conserved in chemical reactions?
On this basis, we might suggest that the principle of conservation of mass that is taught in school science is falsified all the time – or at least needs to be understood differently from how it is usually presented.
Type of reaction
Mass change
endothermic
mass of products > mass of reactants
exothermic
mass of products < mass of reactants
If we just consider the masses of the substances then mass is not conserved in chemical change
Yet, the discrepancies really are tiny – so tiny that in school examinations candidates are expected to pretend there is no difference. But, strictly, when (as an example) copper carbonate is heated in a crucible and decomposes to give copper oxide and carbon dioxide there is a mass decrease even if you could capture all the CO2. But it would not be measurable with our usual laboratory equipment – so, as far as chemistry is concerned, mass is conserved. 'To all intense and purposes' (even if not absolutely true) mass is always conserved in chemical reactions.
Mass is conserved overall
But actually, according to current scientific thinking, mass is always conserved (not just very nearly conserved), as long as we make sure we consider all relevant factors. The energy that allowed us to boil the kettle or be lifted in an elevator must have been provided from some source (which has lost mass by the same extent). In an exothermic chemical reaction there is an extremely slight difference of mass between the reactants and products, but the surroundings have been warmed and so have got (ever so slightly) heavier.
Type of reaction
Mass change
endothermic
energy (and equivalent mass) from the surroundings
exothermic
energy (and equivalent mass) to the surroundings
If we just consider the masses of the substances then mass does not seem to be conserved in chemical change
As Einstein himself expressed it,
"The inertial mass of a system of bodies can even be regarded as a measure of its energy. The law of the conservation of the mass of a system becomes identical with the law of the conservation of energy, and is only valid provided that the system neither takes up nor sends out energy."
Einstein, 1917/2015, p.59
Annihilate the neutrons!
So, if we read about how in particle accelerators, particles are accelerated to immense speeds, and collided, and so converted to pure energy we should be suspicious. The particles may well have been destroyed – but something else has now acquired the mass (and not just the rest mass of the annihilated particles, but also the mass associated with their high kinetic energy).
So, we cannot convert all of the mass of a neutron into energy – only reconfigure and redistribute its mass-energy. But we can still ask: what if all the mass of the neutron were to be converted into some kind of radiation that carried away all of its mass as high energy rays (perhaps Hoffal's radiation?)
Perhaps the genius scientist Hoffal, with his "unique mind", had found a way to do this (hm, with a magnetic field?) Even if that does not seem very feasible, it does give us a theoretical limit to the energy that could be produced by a process that converted a neutron into radiation.6 Each neutron has a rest mass of about
1.67 x 10-27 kg
now the conversion factor is c2 (where c is the speed of light, which is near enough 3 x 108 ms-1, so c2 =(3×108ms-1)2 , i.e., about 1017m2s-2), so that mass is equivalent to about 1.50 x 10-10 J 5 or,
0.000 000 000 150 J
Now that is a lot more energy than the 1.25 x 10-13 J released in the decay of a neutron,
0.000 000 000 150 000 J
>
0.000 000 000 000 125 J
and now we could in theory boil the water to make our cup of tea with many fewer neutrons. Indeed, we could do this by annihilating 'only' about 7
448 000 000 000 000 neutrons
This is a lot less neutrons than before, i.e.,
448 000 000 000 000 neutrons
< 538 000 000 000 000 000 neutrons
but it seems fair to say that it remains the case that the number of neutrons needed (now 'only' about 448 million million) is still a good deal more than 8.
448 000 000 000 000 neutrons
> 8 neutrons
So, if over 400 million million neutrons would need to be completely annihilated to make a single cup of tea, how much damage can 8 neutrons do to a distant planet?
A common learning difficulty
In any reasonable scenario we might imagine 8 neutrons would not be significant. This is worth emphasising as it reflates to a common learning difficulty. Quanticles such as atoms, atomic nuclei, neutrons and the like are tiny. Not tiny like specs of dust or grains of salt, but tiny on a scale where specs of dust and grains of salt themselves seem gigantic. The scales involved in considering electronic charge (i.e., 10-19C) or neutron mass (10-27 kg) can reasonably said to be unimaginatively small – no one can readily visualise the shift in scale going from the familiar scale of objects we normally think of as 'small', to the scale of individual molecules or subatomic particles.
Students therefore commonly form alternative conceptions of these types of entities (atoms, electrons, etc.) being too small to see, but yet not being so far beyond reach. And it is not just learners who struggle here. I have even heard someone on a national news programme put forward as an 'expert' make a very similar suggestion to Egrorian, in this case that a "couple of molecules" could be a serious threat to public health after the use of chemical nerve agent. This is a preposterous suggestion to a chemist, but was, I am sure, made in good faith by the international chemical weapons expert.
It is this type of conceptual difficulty which allows scriptwriters to refer to 8 neutrons as being of some significance without expecting the audience to simply laugh at the suggestion (even if some of us do).
It also explains how science fiction writers get away with such plot devices given that many in their audiences will readily accept that a few especially malicious molecules or naughty neutrons is a genuine threat to life.8 But that still does not justify using angle-poise lamps as futuristic spacecraft joysticks.
Jenna pilots the most advanced spacecraft in the galaxy
Works cited:
Einstein, A. (1917/2015). Relativity. The special and the general theory. (100th Anniversary ed.). Princeton: Princeton Univerity Press.
Treptow, R. S. (2005). E = mc2 for the Chemist: When Is Mass Conserved? Journal of Chemical Education, 82(11), 1636. doi:10.1021/ed082p1636
Notes:
1 To explain: For younger readers, television was first broadcast in monochrome (black and white – in effect shades of grey). My family first got a television after I started primary school – the justification for this luxury was that the teachers sometimes suggested programmes we might watch.
Colour television did not arrive in the UK till 1967, and initially it was only used for selected broadcasts. The first colour sets were too expensive for many families, so most people initially stayed with monochrome. This led to the infamous 'helpful' statement offered by the commentator of the weekly half-hour snooker coverage: "And for those of you who are watching in black and white, the pink [ball] is next to the green". (While this is well known as a famous example of misspeaking, a commentator's blooper, those of a more suspicious mind might bear in mind the BBC chose snooker for broadcast in part because it might encourage more people to watch in colour.)
Snooker – not ideal viewing on 'black and white' television (Image by MasterTux from Pixabay )
My father had a part-time weekend job supervising washing machine rental collections (I kid you not, many people only rented such appliances in those days), to supplement income from his full time job, and this meant on Monday evenings after his day job he had to visit his part-time boss and report and they would go throughout the paperwork to ensure things tallied. I would go with him, and was allowed to watch television whilst they did this – it coincided with Star Trek, and the boss had a colour set!
2 Assuming water had to be heated from 20ËšC to 100ËšC, and the cup took 200 ml (200 cm3) of tea then the calculation is 4.2 x 80 x 200
4.2 J g-1K-1 is the approximate specific heat capacity of water.
Changing these parameters (perhaps you have a small tea cup and I use a mug?) will change the precise value.
3 That is the energy needed divided by the energy released by each neutron: 67200 J ÷ 1.25 x 10-13 J/neutron = 537 600 000 000 000 000 neutrons
4 E=mc2
so m = E/c2 = 67 200 ÷ (3.00 x 108)2 = 7.47 x 10-13
5 E=mc2 = 1.67 x 10-27 x (3.00 x 108)2 = 1.50 x 10-10
6 Well, we could imagine that somehow Hoffal had devised a process where the neutrons somehow redirect energy provided to initially generate the magnetic field, and perhaps the weapon was actually an enormous field generator producing a massive magnetic field that the funnel somehow converted into a beam (of tachyons?) that could pass across vast amounts of space without being absorbed by space dust, remaining highly collimated, and intense enough to destroy a world.
So, perhaps the neutrons are analogous to the core of a laser.
I somehow think it would still need more than 8 of them.
7 That is the energy needed divided by the energy released by each neutron: 67200 J ÷ 1.50 x 10-10 J/neutron = 4.48 x 1014 neutrons
8 Of course molecules are not actually malicious and neutrons cannot be naughty as they are inanimate entities. I am not anthropomorphising, just alliterating.
