Neu(t)ronii lui Chadwick

[sandokhan]

Cea mai exceptionala expunere care ne arata faptul ca J. Chadwick (rosicrucian, membru London Royal Society), nu a descoperit absolut nimic in 1932, nici un fel de neutroni sau alte particule.

http://luloxbooks.co.uk/findings1.htm (excerpts)

Blackett calls Chadwick’s most famous paper ‘a model of clear physical thinking’. Chadwick’s biographer writes that ‘even a non-scientist, with no knowledge of the fascinating story leading up to the discovery, could read this and recognize the incisiveness of the argument, constructed with all the drama of an end-game by a grand master in chess.’ Yet its title is strangely unpromising:

Possible Existence of a Neutron

Why announce the existence of something if that existence is only possible? Why a neutron? Why not ‘the neutron’? The thing had, after all, been named more than ten years before. Chadwick perhaps opts for caution precisely because the particle is so eagerly anticipated by Cavendish physicists, the subject of their speculation for a decade. He is wary of sounding a false alarm. Especially at Cambridge, Irène Curie and Frédéric Joliot were thought foolish for having in effect discovered the neutron without realizing it, and this may be another reason for Chadwick’s hesitancy now. If Chadwick is later shown to be wrong, then he has lost nothing, on the face of it at least. If he is right, then his cautious title merely consolidates his reputation as a careful experimenter; and, inadvertently or not, it becomes a jibe at the French.

Chadwick described the discovery at a meeting of one of the Cavendish’s physics clubs in the same month as the paper was submitted, and the notes record the title ‘Neutron?’ here too. Of course, Chadwick is not as tentative as he pretends. Immediately upon the paper’s publication, he wrote to Niels Bohr: ‘I have put this forward rather cautiously, but I think the evidence is really rather strong.’ It was. Possible quickly became certain. Chadwick’s more detailed account of the discovery, written with Norman Feather, and published later in 1932 in the Proceedings of the Royal Society is titled ‘The existence of a neutron’. The following year ‘The Neutron’ suffices.

This all-important first paper begins with two apparently simple statements of fact, each attributed to a different group of scientists, and presented in a straightforward, story-telling manner:

It has been shown by Bothe and others that beryllium when bombarded by α-particles of polonium emits a radiation of great penetrating power, which has an absorption coefficient in lead of about 0.3 (cm)[-1].

It is in a sense an unremarkable opening, the classic overture of anonymous science, It has been shown that ..., after the doubly cautious title, another gesture of self-deprecation.

Yet it is a breathless and dramatic first sentence too, settling quickly into galloping iambics, shown by Bothe and others, then stumbling abruptly amid the shell-fire of plosive b’s and p’s whose percussion breaks this rhythm and directly evokes the subatomic artillery which is Chadwick’s chosen weapon in this research.

There is a literary air, too, about a radiation of great penetrating power. This willfully qualitative description is immediately quantified by an absorption coefficient which confirms to those in a position to know just how great this power is. Chadwick could have described the radiation in this technical way straight off; his introductory phrase, almost flowery in comparison, shows he is reaching for a larger audience with his news.

Recently Mme. Curie-Joliot and M. Joliot found, when measuring the ionisation produced by this beryllium radiation in a vessel with a thin window, that the ionisation increased when matter containing hydrogen was placed in front of the window.

Taking these two statements reporting the work of other scientists together, we see that they are being listed in order that we might question what they have found. The first statement, remarking the radiation of great penetrating power, suggests that Bothe has observed something anomalous. The second statement that the ionisation increased hints that what the Joliots have observed is more than an anomaly, that it is counter-intuitive. There is the further implied question: what are these scientists are doing to investigate further? And the implied answer: not much. Chadwick, of course, will not answer on their behalf, but will shortly pre-empt their absent efforts with his own dramatic announcement.

Enough on the length of a dash. This sentence naming the French scientists is in any case hardly a comfortable one, with its long subordinate clause and its repetition of the ionisation. Its awkwardness perhaps communicates Chadwick’s belief in the inadequacy of the Joliot-Curies’ experiment and conclusions. Chadwick gives us the essential details of their apparatus nonetheless, emphasizing the thin window that allows passage of the beryllium radiation onto the matter containing hydrogen which is in fact paraffin wax. By doing this, he spares himself the chore of having later to describe his quite similar apparatus where it would clog the dramatic narrative of his own discovery.

The effect appeared to be due to the ejection of protons with velocities up to a maximum of nearly 3 x 10[9] cm. per sec.

But appeared to whom? This is not Chadwick’s experiment. The British author is simultaneously reporting the French findings and casting doubt upon them. The Joliot-Curies had reported the month before their belief that the cause of the ionization was protons, or ‘hydrogen rays’—‘rayons H’. Knowing their velocity is essential to the calculation of their energy and the energy of the beryllium radiation. Chadwick goes to some trouble to give us a picture of the range and limit of this velocity, up to a maximum of nearly … This is crucial to his rationalization of the French results.

They suggested that the transference of energy to the proton was by a process similar to the Compton effect, and estimated that the beryllium radiation had a quantum energy of 50 x 10[6] electron volts.

Having sown seeds of doubt, Chadwick subtly advises us with this continued reporting of their work that he believes the French scientists are indeed mistaken: They suggested, but I think otherwise. This is, in the telling of it at least, before Chadwick has done any experiment or obtained any data to give him grounds for an alternative belief. These, he wants us to know, are simply his thought processes on reading the French paper. For a fresh paragraph, here he puts down the paper and turns to the laboratory bench.

I have made some experiments using the valve counter to examine the properties of this radiation excited in beryllium.

The first-person pronoun now carries emphatic weight because it has been teasingly withheld in the previous two sentences of criticism and in the paper so far. The pontifical atmosphere thickens with Chadwick’s somewhat archaic reference to experiments made rather than ‘performed’ or ‘done’ and with the choice of the definite article for the valve counter, as if for a proper name. This could suggest either familiarity or novelty. It is the latter that is meant, and so Chadwick goes on to describe the basic arrangement of the apparatus that the Cavendish has developed in order to automate the counting of scintillations.

The sentence concludes with a somewhat redundant emphasis on the beryllium being used in these experiments. Chadwick is making it crystal clear that the radiation he is working with is the same as the Joliot-Curies’ because the beryllium source is the same.

The valve counter consists of a small ionisation chamber connected to an amplifier, and the sudden production of ions by the entry of a particle, such as a proton or a-particle, is recorded by the deflexion of an oscillograph.

Chadwick elides his description of the static apparatus with its modus operandi, which serves to underline its simplicity of operation. By careful design of the valve amplifier, the Cavendish scientists were able to make the deflection of the oscillograph directly proportional to the amount of ionization. The suggestion that their counting method is more transparent than others is a reminder of past battles won as well as an invitation for us to place greater trust in the results to come.

The sentence is the first point where Chadwick introduces Rutherfordian ideology. It is constructed in such a way as to indicate that a proton is a particle, and furthermore that it would be almost unnatural to think of one in any other way. This is all done by means of an off-hand such as …. Protons are not ‘rayons H’ at the Cavendish.

These experiments have shown that the radiation ejects particles from hydrogen, helium, lithium, beryllium, carbon, air, and argon.

Chadwick here uses the rhetorical device of accumulation to draw a contrast with his description of the Joliot-Curies’ experiment. Set against this exhaustive list, their one result, obtained from ‘matter containing hydrogen’, looks meagre and, worse, inconclusive. Chadwick and his mentor, Rutherford, have employed accumulation before in reporting series of experiments in which samples of various elements are bombarded with various particles. It is part of their celebrated experimental method to go to such lengths. That they report doing so here in such a way (they could have covered the ground in a single phrase such as ‘… from many light elements’) heaps ignominy on the Paris group. It shows them revelling in the sheer power of experiment. ‘We could do experiments and eject radiation from anything!’ is the implication. Why, even air works. It’s not worth the bother of separating its constituents (nitrogen and oxygen, the next elements in sequence after carbon). Reading the sentence aloud, we hear that putting air in place of ‘nitrogen, oxygen’ helps the rhythm. The list accelerates to a triumphant conclusion. Although constrained to be given in the order in which they occur in the periodic table, the first four elements in the list happen to be in dactyls, with the emphasis on the first of three syllables in each case. They dictate the tempo. The extra half-syllable in beryllium is the cue for the final iambic sprint: carbon, air, and argon. There is a note of contempt in all this, but mainly there’s just glee.

The particles ejected from hydrogen behave, as regards range and ionising power, like protons with speeds up to about 3.2 x 10[9] cm. per sec. The particles from the other elements have a large ionising power, and appear to be in each case recoil atoms of the elements.

Chadwick first mollifies the Joliot-Curies, agreeing with them that the hydrogen ejecta are protons, although he doesn’t miss the opportunity to state once again that protons are particles, not rays. He does this in a devious way by presuming that what emerges from the hydrogen are particles to start with, particles which are then observed to behave … like protons. Because the particles behave … like protons, protons, it is to be assumed, are particles. Curiously, he does not equate them absolutely. Since the hydrogen nucleus is well known to comprise a single proton, Chadwick is needlessly hedging his bets here by using behave … like instead of ‘are’. This caution spills over from the following sentence where it is more needed (The particles … appear to be …).

Chadwick is in broad quantitative agreement with the French scientists, too, although he gives his particles’ speed to two significant figures compared to the one significant figure in the cited French value. This throwaway implication that his experimental accuracy is greater by ten-fold than the French, ironically enhanced by the prefacing about …, gives the phrase the character of meiosis. Chadwick tempers numerical accuracy by introducing what appears to be a verbal imprecision. He speaks of his protons’ speeds, whereas he used the word velocities in reference to the French work. Velocity is speed measured in a given direction. Since direction is not important here, speed is in fact a sufficiently precise term for the purposes of describing both sets of experiments. Saying that the French were measuring velocities is to accuse them of being over-particular and pedantic. The Anglo-Saxon word trumps its Latinate equivalent. We see an English empiricist at play.

It is a deadly game. Chadwick is softening the Joliot-Curies up for the killer blow, which comes in the next few sentences. By suggesting that the particles from his array of elements are recoil atoms of those elements, he is preparing to strip away the central plank of their argument, which is their calculation of the radiation energies by analogy with the Compton effect. Of course, when Chadwick writes that The particles from the other elements ... appear to be in each case recoil atoms of the elements he means almost the opposite. It is in the nature of an apparatus such as this that elements do not appear. They do not reveal their identity. They leave only tracks.

In order to demonstrate the Joliot-Curies’ folly, Chadwick now humours them and goes along with their procedure, but taking advantage of his own data from the experiments with the catalogue of elements.

If we ascribe the ejection of the proton to a Compton recoil from a quantum of 52 x 10[6] electron volts, then the nitrogen recoil atom arising by a similar process should have an energy not greater than about 400,000 volts, should produce not more than about 10,000 ions, and have a range in air at N.T.P. of about 1.3 mm.

Actually is a rare word in a scientific paper. Its use is a measure of Chadwick’s incredulity at what the French scientists have missed as well as a sign of his growing confidence. Safely through the distasteful business of describing the French science, Chadwick can relax. His English begins to flow. Like sometimes in the next sentence, Actually is more conversational than the obvious alternative ‘In fact’.

Chadwick poured forth theoretical figures in the first, long sentence of the paragraph. Here, by contrast, the quantities he has measured are themselves carefully measured out in separate sentences. He regards calculation from theory as trivial, and the figures that come from it as next to worthless, compared with experiment and the real values that it generates. The parcelled presentation of these data is a reminder of the sheer difficulty of the experiment. The full meaning of opening Actually becomes clear: this is not merely English throat-clearing; the word is used in its literal sense.

These results, and others I have obtained in the course of the work, are very difficult to explain on the assumption that the radiation from beryllium is a quantum radiation, if energy and momentum are to be conserved in the collisions.

The now cocky Chadwick employs ironic understatement. The results are not just very difficult, but quite impossible, to explain on the quantum radiation assumption. This assumption of course is the one made by the Joliot-Curies. We are led to believe that an easier explanation will be shortly forthcoming.

[sandokhan]

(continuare)

There is a hint in Chadwick’s wording that a quantum radiation is some special kind of radiation. In fact, it was well established by 1932 that all radiation exists as quanta called photons. It would be excessive to claim that Cambridge was ideologically opposed to quantum interpretations of physical phenomena at this time. Chadwick’s obvious distaste stems from his and Rutherford’s conviction that, for many problems, it was simply not necessary to invoke quantum theory. The traditionalism pays off so far as the actual discovery of the neutron is concerned, but it quickly limits their deeper understanding of it.

The French had earlier foundered by making the much the same error in reverse. Their January 1932 paper, which came so close to identifying the neutron, found the discrepancy between the radiation energies they had just measured and those they had predicted the previous month was ‘not sufficient reason to reject this hypothesis [based on the Compton effect analogy] given the considerable errors possible in evaluating the quantum energies of the highly penetrating radiations from their absorption coefficients.’ They had, in other words, thrown away the possibility of finding an old-fashioned billiard-ball particle in order to hold to the new quantum logic. Frisch later noted that theoreticians in the Curie lab got short shrift if they showed signs of preferring particles to rays as the solution to a problem.

British antagonism towards the French is nothing exceptional, of course. In his memoir, Feather praises Bothe and Becker’s ‘commendably cautious’ research of 1930. Curie’s work, however (he singles her out, although he is referring mainly to a paper co-authored with Joliot), was ‘uncritical’ and contained one remark that was ‘entirely gratuitous’. The comparative warmth towards German science and the chill towards the French echoes the geopolitical dynamics in Europe at the beginning of the 1930s when Britain and France were immersed in battles over trade tariffs and policy disagreements concerning war reparations from Germany. The attitudes also chime with the general sense of the different ways physics was done. Physicists on the northern side of the continent of Europe displayed ‘idealistic tendencies’ at this time, according to Laurie Brown and Lillian Hoddesdon’s The Birth of Particle Physics. ‘The members of this tradition did not propose new particles …; in general they believed that if there were to be a breakdown of physics theory, the cause would not be the wrong choice of building blocks but rather wrong theories. ... However, proposing new particles turned out to be the correct approach to solving the problems at hand.

‘New particles were more often proposed in the 1930s by the members of another tradition, which seems to contrast with the more abstract northern European one: an “island tradition,” more concrete, more oriented toward model building, and having a closer relationship between theory and experiment. In England, for example, this tradition was exemplified by the work of Maxwell, J.J. Thomson, and Rutherford.’

These traits reach deep into the psyche of nations. The neutron story shows English empiricists and materialists at odds above all with France where ‘[t]he investigation of phenomena was treated as a conceptual rather than an empirical proceeding,’ reliant upon ‘the intuition of essences’. The Joliot-Curies’ Paris was the hothouse for Jean-Paul Sartre’s Being and Nothingness (the title could be a direct reference to rays and particles) and Maurice Merleau-Ponty’s Phenomenology of Perception, both published a decade later, the latter calling empiricists into question for treating data obtained by the senses as objects. Cambridge was in fealty to Bertrand Russell, who, while apparently taking on board the implications of quantum mechanics to a greater extent than some of the physicists, still felt that perception ‘must be in some degree an effect of the object perceived, and it must more or less resemble the object if it is to be a source of knowledge of the object.’

Chadwick at this point in his argument takes hostage the laws of conservation of energy and momentum. These are two of the sacred cows of physics. The stakes are high indeed. He will inform us of their fate in a few sentences’ time. Meanwhile, negotiations continue.

The difficulties disappear, however, if it be assumed that the radiation consists of particles of mass 1 and charge 0, or neutrons.

This is the coup de grâce. As in a magic trick, The difficulties disappear if it is neutrons that are responsible for the mischief, not some foreign radiation; and, as in any good magic trick, it is all made to look easy. Chadwick’s sentence is impersonal yet dramatic. His prized grammatical rectitude helps to build an atmosphere of theatre; if it be assumed ..., rather than ‘if it is assumed’ or ‘if one assumes’, underscores the drama of the disappearing act, a rhetorical flourish that adds an element of music hall pomposity. The assumption, Chadwick’s this time, although expressed here largely for these rhetorical reasons, was very much part of Chadwick’s thinking. As he later wrote, ‘I started with an open mind, though naturally my thoughts were on the neutron.’

There is an ideological claim to supremacy wrapped up in this magician’s handkerchief: the trick only works if the radiation consists of particles, in other words if the rayists will surrender to the particlists. This is an ultimatum from the British, whose first thought is of material objects, of particles like billiard balls, to the French, who believe in evanescent ‘rayons’. These are relatively early days in wave-particle duality, and some confusion and inconsistency of terminology is to be expected. The shock is that the scientific split opens along the English Channel.

The almost parenthetical final clause, or neutrons, slips in Chadwick’s claim to one of the major discoveries in twentieth century physics. The alternative wording, ‘... if it be assumed that the radiation consists of neutrons’, would be too precipitate; it could seem triumphalist (it shrieks for an exclamation mark). Another possibility would be an additional sentence, something like: ‘These properties conform to those predicted for the neutron’, or simply: ‘These are neutrons’. But the former sounds stilted, while the latter is too bold for Chadwick at this moment.

His experimental measurements set to one side for the moment, Chadwick continues to carry us along through his hypothetical nuclear landscape in a state of suspended disbelief. His rationalization depends on easy arithmetic which implicitly mocks the quantum sophistry of the rival group:

The capture of the a-particle by the Be9 nucleus may be supposed to result in the formation of a C12 nucleus and the emission of the neutron. From the energy relations of this process the velocity of the neutron emitted in the forward direction may well be about 3 x 10[9] cm. per sec. The collisions of this neutron with the atoms through which it passes give rise to the recoil atoms, and the observed energies of the recoil atoms are in fair agreement with this view.



An alpha particle with four nucleons collides with the beryllium nucleus with nine. There emerges a carbon nucleus with twelve nucleons; one unit remains—the neutron. What could be simpler? The familiar further references to the neutron and this neutron are reminders that the particle’s existence has been long awaited at the Cavendish. Glossing over the more complex calculations of energies and velocities (From the energy relations … the velocity … may well be …), Chadwick quickly engineers a resolution of the scenario he has sketched with the data he has obtained; they are in fair agreement.

Moreover, I have observed that the protons ejected from hydrogen by the radiation emitted in the opposite direction to that of the exciting α-particles appear to have a much smaller range than those ejected by the forward radiation. This again receives a simple explanation on the neutron hypothesis.

Chadwick reasserts the first person in order to continue relating his experimental observations. Moreover signals a coming superabundance of evidence for the new hypothesis. If rays rather than particles were the consequence of the collision, these would radiate with equal intensity in all directions. If particles emerge, then the rules of the billiards table apply, and their speed and direction are determined by the speed and direction of the impinging particles. That the latter is the case is strongly suggested by Chadwick’s observation of the very different ranges of the protons ejected in the forward and backward directions. The simple explanation, which Chadwick does not stop to give, is based on the law of conservation of momentum. The reference in the last sentence to the neutron hypothesis is a reminder that some uncertainty remains in what is being proposed. Observing events in an ionization chamber is one thing; accounting for them another.


Chadwick now paints the picture from the rayist point of view:

If it be supposed that the radiation consists of quanta, then the capture of the a-particle by the Be9 nucleus will form a C13 nucleus. The mass defect of C13 is known with sufficient accuracy to show that the energy of the quantum emitted in this process cannot be greater than about 14 x 10[6] volts. It is difficult to make such a quantum responsible for the effects observed.

It is curious the language in which Chadwick wraps his brief discussion of quantum mechanical phenomena. His scrupulous use of the subjunctive (If it be supposed …) here seems to imply that quanta might not exist at all; if they do, then perhaps they can still be envisaged as particles, actual things that radiation consists of. But Chadwick can work with the new-fangled physics when he has to. His calculation (based on the mass defect, the difference between the rest-mass energies of the particles before and after collision, which is emitted or released as radiation energy) concerning the carbon nucleus that would be the consequence of an alpha-beryllium cluster shows that the quantum of energy produced would be rather feeble, much less than that estimated by the Joliot-Curies using the Compton effect. Chadwick repeats his earlier understatement: It is difficult to make such a quantum responsible ...; again, in Chadwick’s view, it is more than difficult; it is impossible to make it so. There is a further clue to this effect: the use of make in place of the expected ‘hold’ suggests an ill fit and a forcing effort as in that required to make a piece of a jigsaw puzzle occupy the wrong space.

It is to be expected that many of the effects of a neutron in passing through matter should resemble those of a quantum of high energy, and it is not easy to reach the final decision between the two hypotheses.

In what at first appears to be a late conciliatory move toward the French scientists, Chadwick concedes in effect that some of his measurements are not incompatible with a quantum interpretation. But he spoils it for them by the reminder of the presence of a neutron, which is to him pre-existent. (A more impartial statement could easily have been constructed around a phrase such as ‘the effects observed’.) The final phrase stalls for dramatic effect and, while making a further gesture toward his rivals’ efforts (… it is not easy …), at last asserts Chadwick’s power to make the final decision.

All pussyfooting is abandoned for the devastating final sentence of the paper. Chadwick now takes the sacred cows he has captured earlier, thrusts them before us, and places Occam’s razor at their throats:

Up to the present, all the evidence is in favour of the neutron, while the quantum hypothesis can only be upheld if the conservation of energy and momentum be relinquished at some point.

Which is it to be? Will you believe—for belief is what is being demanded—in the neutron? Or are you prepared to overturn the laws of physics? Even Chadwick seems shocked at the choice he offers. He relents at the last, and the paper coasts to a close with a postponement of judgement: … at some point.

In these concluding sentences, Chadwick adopts the rhetorical tactic he used in his doctoral thesis, setting more or less known facts in opposition in order to ‘choose’ the least improbable: ‘We must conclude either that the _ particle is not made up of four H nuclei and two electrons, or that the law of force is not the inverse square in the immediate neighbourhood of an electric charge. It is simpler to choose the latter alternative ...’, he wrote then. On that occasion, Chadwick chose badly. The alpha particle, it was immediately realized from this new discovery, comprises two protons and two neutrons. This time, he is right. He feels it, and in order to bring the reader along with him the stark choice he offers this time is an easier one to make. Philip Dee, another Cavendish physicist, later wrote: ‘I think the manner of the discovery, involving the straightforward application of the laws of conservation of momentum and energy, so similar to much of his own earlier work, appealed to him above all other considerations, although he also felt strongly the need for a neutron as a universal nuclear constituent.’ The discovery was the fulfillment of Rutherford’s dream; the reporting of it was Chadwick’s homage to his mentor.

[sandokhan]

Deci J. Chadwick nu a descoperit de fapt nici un fel de particula numita neutron...aceeasi argumentare vicleana (Up to the present, all the evidence is in favour of the neutron, while the quantum hypothesis can only be upheld if the conservation of energy and momentum be relinquished at some point - Chadwick) a fost utilizata si de W. Pauli atunci cand a crezut ca a descoperit o noua particula, neutrinul:

The neutrino must exist, Pauli reasoned, because otherwise the atomic process known as beta decay would violate the physical laws of conservation of energy and conservation of angular momentum.

The neutrino, which is a subatomic particle, is described by Hoffmann as 'fluctuating uncertainly between existence and non-existence.' That is to say, in the language of dialectics, 'it is and is not.' How can such a phenomenon be reconciled with the law of identity, which categorically asserts that a thing either is or is not? Faced with such dilemmas, which reappear at every step in the world of subatomic particles described by quantum mechanics, there is frequently a tendency to resort to formulations such as the idea that the neutrino is a particle with neither mass nor charge. The initial opinion, still held by many scientists, was that the neutrino had no mass, and since electric charge cannot exist without mass, the inescapable conclusion was that the neutrino had neither.

Neutrinos are extremely small particles, and therefore difficult to detect. The existence of the neutrino was first postulated to explain a discrepancy in the amount of energy present in particles emitted from the nucleus. A certain amount of energy appeared to be lost, which could not be accounted for. Since the law of the conservation of energy states that energy can neither be created nor destroyed, this phenomenon required another explanation. Although it seems that the idealist physicist Niels Bohr was quite prepared to throw the law of conservation of energy overboard in 1930, this proved to be slightly premature! The discrepancy was explained by the discovery of a previously unknown particle—the neutrino.

THE ELUSIVE NEUTRINO: In my opinion the neutrino concept is the work of a relativistic accountant who tries to balance his books by making a fictitious entry. He does not recognize the existence of the aether and so, when accounting for something where an energy transaction involves an energy transfer to or from the aether, he incorporates an entry under the heading 'neutrinos'.

The neutrino was first postulated in 1930 when it was found that, from the standpoint of relativity theory, beta decay (the decay of a neutron into a proton and an electron) seemed to violate the conservation of energy. Wolfgang Pauli saved the day by inventing the neutrino, a particle that would be emitted along with every electron and carry away energy and momentum (the emitted particle is nowadays said to be an antineutrino). W.A. Scott Murray described this as ‘an implausible ad hoc suggestion designed to make the experimental facts agree with the theory and not far removed from a confidence trick’. Aspden calls the neutrino ‘a figment of the imagination invented in order to make the books balance’ and says that it simply denotes ‘the capacity of the aether to absorb energy and momentum’. Several other scientists have also questioned whether neutrinos really exist.