Lab Lib

M.F. Perutz

  • Rutherford: Simple Genius by David Wilson
    Hodder, 639 pp, £14.95, February 1984, ISBN 0 340 23805 4

Rutherford was one of my early heroes, and Wilson’s biography of this great and lovable man has enlivened and enlarged, rather than debunked, my youthful image. Rutherford was the man who created the atomic age: a farmer’s boy from New Zealand whose brilliance and Herculean energy brought him the Presidency of the Royal Society, a peerage, and honours from all over the world. Wilson goes a long way to tracing the mental paths and the passionate curiosity that led Rutherford to his great discoveries. He paints a picture of a towering, boisterous, stunningly able, outgoing, cheerful, irascible, good-natured, generous and compassionate man who delights above all in the pursuit of experimental physics and feels sorry ‘for the poor chaps who haven’t got labs to work in’.

Supported by that legacy of Prince Albert’s far-sighted interest in science, an 1851 Exhibition Scholarship, Rutherford arrived in Cambridge in September 1895, only a few months before Röntgen’s discovery of X-rays and Becquerel’s of radioactivity ushered in a revolution in physics. He found college men ‘very capable, especially in conversation. It’s a pity so many of them fossilise.’ He soon realised that only by scientific success could he make himself socially acceptable and financially viable. ‘If one gets a man like J.J.’ – J.J. Thomson, then Cavendish Professor of Physics – ‘to back one up,’ he wrote to his fiancée in New Zealand, ‘one is pretty safe to get any position.’ Little did he know Cambridge! Three years later, when his scholarship expired, he applied for the chair in physics at McGill University in Montreal, hoping ‘that this may make J.J. act in respect of getting me something to do in Cambridge. I will probably go in for a fellowship this year ...’ In fact nothing materialised, and most of Rutherford’s great discoveries were made at Montreal and later Manchester. He returned to Cambridge in 1920 as J.J. Thomson’s successor to the Cavendish chair, but only after protracted negotiations, because the University authorities considered the honour of a Cambridge professorship worth a substantial drop in salary. According to Rutherford, ‘the chief trouble is the literary fraternity which is of late becoming more and more persistent in principle against the greater share for scientific purposes.’ Plus ça change ...

I first saw Rutherford in the autumn of 1937, at a seminar given by his friend Niels Bohr, the great Danish theoretician. Bohr proposed a liquid-drop model of the atomic nucleus which appeared to sweep away one of the problems which Rutherford had been trying to solve since his arrival at Cambridge. If the nucleus was merely a fluid drop composed of protons and neutrons, then it had no fixed structure, and many of Rutherford’s experiments designed to solve that structure had been pointless. Young scientists will be relieved to learn from this book that even Rutherford did some ‘damn silly’ experiments at times. At the seminar I was overawed by the giants of physics and sat on one of the back benches, but another graduate student, Fred (now Sir Frederick) Dainton, overheard Rutherford saying to Bohr after the lecture: ‘If mass disappears, energy will appear.’ Here and in several other places Wilson demolishes the myth that Rutherford failed to foresee the possibility that nuclear physics might have practical applications. He died in 1937, a year before one of his former German pupils discovered uranium fission. He therefore did not live to witness the terrifying implications of the atomic age and maintained his buoyant faith in the value of physics to the end.

‘This country is judged,’ he said in a speech in 1921, ‘not by the size of its exports or its fleet, but by its contribution to knowledge.’ He failed to foresee that shrinking exports would also throttle the funds needed for the pursuit of knowledge. I was surprised to learn that in 1915 it was accepted wisdom that the French invented, while the Germans and British turned their inventions to profit: many of my contemporaries in the Cavendish had to go to America in order to find someone interested in turning their inventions to profit. I wonder what killed the British spirit of enterprise.

Rutherford died before I had had any chance of attending his lectures. After his death, spare reprints of his scientific papers were laid out in the attic of the lab, and research students were allowed to help themselves. I still have those reprints and look to them as models of the way science should be done. The experimental results are reported lucidly and concisely with a minimum of jargon and mathematics; every conceivable objection is excluded by experiment rather than by argument, leaving no possible loopholes in the conclusions. From those papers and from the atmosphere around the place I became imbued with Rutherford’s values, which Wilson characterises as loyalty to your laboratory, extreme devotion to hard experimental work and strong aversion to speculation beyond what is justified by the experimental results. When Crick and Watson lounged around, arguing about problems for which there existed as yet no firm experimental data instead of getting down to the bench and doing experiments, I thought they were wasting their time. However, like Leonardo, they sometimes achieved most when they seemed to be working least, and their apparent idleness led them to solve the greatest of all biological problems, the structure of DNA. There is more than one way of doing good science.

Did Rutherford make his discoveries by the hypothetico-deductive method postulated by modern philosophers of science? Like Napoleon, who did not win his battles by any fixed strategy, Rutherford did not follow any one method. A favourite one, stressed by Wilson, consisted in pursuing any anomalous or unexpected effect, but any intelligent scientist does that. Rutherford’s strength lay in always being on the look-out for such effects and being extremely observant in spotting them. The most spectacular of those unexpected effects was obtained in 1909 by two of Rutherford’s collaborators, Geiger and Marsden, when they watched the scattering of alpha particles by a gold foil (alpha particles are helium nuclei shot out by their radium source). Most of the particles passed straight through the gold, but about one in 8000 was reflected backwards: in Rutherford’s words, ‘as though you had fired a 15-inch shell at a piece of tissue paper and it had bounced back at you.’ This observation provided the first clue to the structure of the atom. It showed that it is a solar system in which nearly all the weight is concentrated in a tiny positively-charged sun, the nucleus; this nucleus is surrounded by almost weightless negatively-charged planets, the electrons. An alpha particle is itself a tiny atomic nucleus, and a gold foil therefore looks to it like empty space in which the heavy gold nuclei are distributed so thinly that the chance of hitting one is quite small, but if the much lighter alpha particle does hit one of them, it is bounced back hard by its positive charge.

Geiger and Marsden’s experiment had been designed to tell them something about alpha particles rather than about the gold foil, and Rutherford had had no working hypothesis of the atom before their totally unexpected result. I once held this up to Sir Karl Popper as an argument against the hypothetico-deductive method, which postulates that scientists advance by first formulating hypotheses and then designing experiments to test them, rather than by the inductive method which consists in deriving theories from observations. Popper retorted that neither Geiger nor Marsden had been able to derive the structure of the atom from their observations: therefore it was not implicit in them, but was the brainchild of Rutherford’s powerful physical insight. I have now learned that even to Rutherford the truth did not dawn in a flash: it took him eighteen months to work it out, which shows that he needed more than the bare observations. On another occasion in Cambridge many years later, two of Rutherford’s collaborators, Oliphant and Cockroft, obtained a result which neither they nor Rutherford could at first understand. It kept Rutherford awake. He turned it over and over in his mind until at 3 a.m. he suddenly knew the answer. Excitedly he telephoned Oliphant to wake him up and tell him what it was. Here again Rutherford’s imagination solved the riddle: they had discovered a light isotope of helium, helium 3, which has since found an important use in work at temperatures near the absolute zero.

Wilson’s most vivid descriptions of Rutherford’s way of working are drawn from one of the very few among his collaborators who are still alive, the Russian physicist Peter Kapitza:

Many admire Rutherford’s intuition which told him how to set up the experiment and what to look for ... Intuition is usually defined as an instinctive process of the mind, something inexplicable which subconsciously leads to the correct solution. This may be partly true, but is strongly exaggerated. The ordinary reader is simply unaware of the colossal amount of work done by scientists... Anyone who has closely observed Rutherford can testify to the enormous amount of work he did. He worked incessantly, always in search of something new. He reported or published only those works which had a positive result; these, however, constituted barely a few per cent of the whole mass of work he did; the rest remained unpublished, and unknown even to his students.

Wilson mentions that Rutherford’s failures sometimes drove him to black despair.

His 1909 model of the atom failed to explain why the electrons do not fall into the nucleus to neutralise its charge. Niels Bohr took up this problem. He combined Rutherford’s model with Planck’s quantum theory by postulating that, for reasons not then understood, the electrons keep in fixed orbits, and he demonstrated the validity of his theory by calculating correctly, for the first time, the wavelengths of the spectral lines given by the simplest atom, hydrogen. Rutherford’s happy collaboration with Bohr contrasts strangely with his disdain for theoreticians. ‘Even the best mathematicians have a tendency to treat physics as purely a matter of equations,’ he said in 1907. ‘I think this is shown by the poverty of the theoretical communications on the problems that face the experimenter today.’ Coming two years after the publication of Einstein’s epoch-making papers on the photoelectric effect and relativity, this is an oddly blinkered outburst. The French theoretician de Broglie reciprocated by condemning Rutherford’s ‘concrete, simplistic modelling of the nucleus’ and pointed out that ‘the fundamental laws of atomic behaviour can only be expressed in abstract terms.’ Physicists today would agree with that, but Wilson shows that Rutherford won, as always, because it was he and not the theoreticians who first predicted the existence of the neutron.

Wilson’s book also shows strange contrasts between Rutherford’s often narrow-minded and provincial utterances and his far-sighted, generous and internationalist actions. When Eddington verified the deflection of light by gravity predicted by Einstein’s theory of relativity, Rutherford grumbled that this result might ‘draw scientific men away from experiment towards broad metaphysical conceptions’. On the other hand, when the Nazis dismissed Max Born, the pioneer of quantum mechanics, from his chair of theoretical physics at Göttingen, Rutherford immediately moved heaven and earth to find him support, a niche to work in at the Cavendish Laboratory and a house in Cambridge. Rutherford disapproved of people who spoke several languages – ‘you can express yourself well in one language and that should be English’ – yet he was in correspondence with all the prominent European physicists and went out of his way to help whoever was in professional or personal trouble. He helped Marie Curie when her love affair with the physicist Paul Langevin was picked up as a scandal by the French papers. Far from being the jingoist his utterances implied, he maintained contact with his friend Stefan Meyer, the head of the Vienna Radium Institute, even when the outbreak of the First World War had made him technically an enemy. In 1921, when the survival of Meyer’s Institute was threatened by runaway inflation, Rutherford saved it by getting the Royal Society to pay Meyer £500 for radium loaned to his Manchester laboratory before the war. When Jewish scholars were dismissed from German universities by the Nazis, Rutherford took a lead in founding the Academic Assistance Council, which raised money for their support and re-establishment in this country: but strangely for such an outspoken man, he refrained from any public condemnation of the Nazis’ anti-semitic policies for fear of offending the Germans and in a desire to remain ‘non-political’. This timid attitude reflected a widespread misjudgment which bolstered the Nazis’ conviction that the British would never fight.

Rutherford’s leadership at the Cavendish Laboratory was crowned by the remarkable achievements of 1932 when Chadwick discovered the neutron, Cockroft and Walton split the lithium atom and Blackett demonstrated the existence of the positron. These triumphs overshadowed the dawn of a new science in a small sub-department of the Cavendish, the Crystallographic Laboratory. There J.D. Bernal, a colourful and brilliant young Irishman, was beginning to apply physics to the study of living molecules such as proteins and viruses. As Bernal’s research student, I was disappointed that Rutherford never looked in to find out what we were doing, and thought this was because he was indifferent to sciences other than atomic physics, but Wilson relates that the conservative and puritanical Rutherford detested the undisciplined Bernal, who was a Communist and a woman-chaser and let his scientific imagination run wild. I was surprised to read that Rutherford had actually wanted to throw Bernal out of the Cavendish Laboratory, but was restrained from doing so by W.L. Bragg, Rutherford’s successor at Manchester and at Cambridge. Had Bragg not intervened, Bernal’s pioneering work in molecular biology would not have started, Kendrew and I would not have solved the structure of proteins, and Watson and Crick would never have met.

I was disappointed to find the famous laboratory poorly equipped, and some of its members making a virtue of necessity by boasting of the great discoveries that had been made with no more apparatus than string and sealing-wax. Apparently Rutherford, though irritated by the chronic breaking-down of machines, was uninterested in raising money for more reliable components. Wilson believes that despite his Jovian confidence in his scientific genius he lacked the confidence to ask for big money, but this seems doubtful – perhaps it was just not his style of working. To the detriment of the laboratory, Rutherford’s failing was shared by Bragg, even though in his youth Bragg himself had suffered under the penny-pinching tyranny of the formidable Lincoln, the moustached laboratory steward who survived to my day. In mitigation it must be said that Rutherford and Bragg were not interested in money for themselves either. Like Faraday, Rutherford never took out a patent and would have strongly disapproved of the gene technologists’ present scramble for money. Rutherford was also averse to snobbery, even though he proudly accepted a peerage. But Wilson is wrong in describing his laboratory as free from class distinctions. There may have been none among the scientists, but there was a sharp division between them and the technicians, symbolised by separate tea rooms. This aroused much ill-feeling when technicians came to include qualified engineers. Rutherford forbade people to work in the laboratory after 6 p.m., on the grounds that they should go home and think, and for many years after his death, I was refused a key to the Cavendish site. If I wanted to switch off my X-ray tube at night, I had to climb over the tall wrought-iron gate and brave the wrath of Alf the porter patrolling the dimly-lit courts.

None of this mattered very much. What did matter, Kapitza described to his mother when he arrived at the Cavendish in 1921 – it was still true when I left the Laboratory 41 years later. ‘Crocodile’, I should explain is Kapitza’s nickname for Rutherford.

With us in Russia everything was cut according to the German pattern ... But England provided the most outstanding physicists and I now begin to understand why: the English school develops individuality ... and provides infinite room for manifestation of personality ... Here they often do work which is so incredible in its conception that it would simply be ridiculed in Russia. When I asked why ... it emerged they were simply ideas of young people, but the Crocodile values so highly that a person should express himself that he not only allows them to work on their own themes, but also encourages them and tries to put sense into their sometimes futile plans. The second factor is the urge to achieve results.

Having been Science Correspondent for the BBC for twenty years, Wilson is an experienced populariser, and keeps his descriptions of Rutherford’s experiments free from unnecessary jargon. I got stuck in only one passage, where Wilson describes Rutherford’s measurement of the charge of the alpha particle. I found that he had omitted to mention Rutherford’s use of a Faraday cage to measure the total positive charge emitted by his radium sample, and also his deflection of the beta rays by a magnetic field.