The Basis of Everything

by Andrew Ramsey

  With its hum of machinery and ever-present blanket of factory smoke or low cloud – more often both in tandem – the city made for a rude reminder to Rutherford of his previous experiences in England. But it was a far greater culture shock for Mary and Eileen. Both had come to enjoy the clean air and natural attractions of Montreal and the Quebec landscape, so adapting to grim suburban life brought its challenges.

  In the years before Rutherford’s recruitment, Manchester’s physics operation had become recognised as the second most influential in Britain after the Cavendish. That had been mainly due to Arthur Schuster. He and his family had moved to Manchester from their native Frankfurt in 1870, and the Schusters formed part of an enduring connection between the university and Germany. That included campus architecture, as well as research-led teaching philosophies. When Rutherford arrived in 1907 there was also a distinctly Germanic influence within his laboratory team.

  One of those men was technician Hans Geiger, who would play a pivotal role in Rutherford’s history-defining discoveries. Working alongside Rutherford, Geiger also invented a revolutionary radiation detection and measuring device that would famously bear his name. Rutherford already held a high regard for German science and its practitioners, thanks to his collaborations with his McGill research student Otto Hahn, who would later emerge as a central figure in the evolution of nuclear physics.

  Although Manchester was not the beneficiary of the sort of largesse William Macdonald had showered upon McGill, Rutherford was pleased to find his facilities more than adequate, once his pilfered resources had been recovered. ‘The laboratory is very good, although not built so regardless of expense as the laboratory in Montreal,’ he wrote to his mother in New Zealand at June’s end in 1907.2

  The initial impression that many at Manchester gained of Rutherford, apart from his capacity for volcanic outbursts, was that he seemed much younger than his thirty-five years. In another letter to his mother, Rutherford delighted in recounting a story from very early in his tenure, when Schuster was still at the university and playing host to Japan’s minister of education, Baron Kikuchi. After Rutherford had been introduced, the distinguished visitor said discreetly to Schuster: ‘I suppose the Rutherford you introduced me to is a son of the celebrated Professor Rutherford’.3

  Having announced his arrival so emphatically, Rutherford also resumed his examinations of radioactivity with vehemence, and rapidly made startling progress. First he had to overcome a critical shortage of radioactive material from which he could source the alpha particles that were essential to his research. However, once he had won the administrative battle to secure supplies of the precious radium, he began writing more scientific history.

  Initially he sought to achieve that success by confirming his theory that particles being given off by the radium were of a different atomic structure from their source material – thereby proving the process of transmutation that had so alarmed Soddy.

  An individual atom of matter had never before been detected, and doing so would take some experimental foresight. It was known that when an electrical charge was passed through alpha radiation particles that had been isolated within a vacuum tube, the bands of colour that were produced could be studied through a spectroscope. The fact that individual elements were known to produce telltale spectral lines in the form of coloured bands separated by solid dark blocks – each as unique as individual fingerprints – meant Rutherford was able to prove the radioactive emanations in the tube were positively charged helium atoms. He and Soddy had theoretically established as much at McGill years earlier, but this represented the first time a single atom had been identified. It also showed definitively that radioactivity released matter of a different atomic structure.

  * * *

  The lofty place that Ernest Rutherford had come to command within the fast-changing world of sub-atomic exploration was formalised in 1908, the year after he left Canada, when he became a Nobel laureate – even if he won the honour in the field of chemistry, ‘for his investigations into the disintegration of the elements, and the chemistry of radioactive substances’ undertaken at McGill.

  In accepting his prize from the King of Sweden on 11 December 1908, Rutherford was later said by some gathered at Stockholm’s Musical Academy to have looked ‘ridiculously young’ and also to have delivered the evening’s best speech.4 In his address, Rutherford joked that he had seen many transformations in laboratories, but that the quickest one was the Nobel committee’s ‘instantaneous transmutation’ of him from physicist to chemist.5 Once the laughter had subsided, he proceeded to astonish his audience by detailing his most recent finding at Manchester: that particles expelled by the naturally occurring element radium were shown to be atoms of an altogether different element, helium.

  In light of the spectre that nuclear science would come to cast upon the world, there was perhaps an irony in this recognition of Rutherford’s work. After all, Alfred Nobel – whose name also adorns the accolade universally associated with peace – built the fortune that perpetually funds his eponymous prizes through his invention of dynamite. It was an innovation so effective that Nobel vainly believed – like the architects of the atomic bomb – it might put an end to all war.

  Ernest and Mary arrived back in Manchester just days before Christmas, and while eight-year-old Eileen was anxious to see the festive gifts her parents had brought back from the Continent, a much larger windfall loomed. The Nobel Committee for Chemistry’s cash prize of almost £7000 (worth around £800,000 today) meant that, for the first time in his already celebrated life, Rutherford was a man of means. He immediately wired sizeable gifts to his parents, brothers and sisters in New Zealand, and while a bulk of the remaining purse was prudently invested, he also splashed on a new Wolseley Siddeley motor vehicle.

  Rutherford had first witnessed the marvel of the ‘horseless carriage’, as it was known, while at the Cavendish in 1897, during a visit to the Crystal Palace – the relocated glass cathedral that hosted the 1851 exhibition that indirectly had determined his future. At the time, he wrote: ‘I was not very much impressed with the machines as vehicles, but I expect they will come into very general use shortly. They say the expense of running about 12 miles an hour [nineteen kilometres an hour] is about one penny per hour, which is rather cheaper than a horse.’6 Over the intervening decade, however, Rutherford had developed a keen interest in motorised vehicles and the autonomy they could provide him and his family.

  The fourteen-horsepower, four-seater tourer was described by Rutherford as ideally suiting their need for ‘quiet travelling’, and as ‘a means of getting fresh air rapidly’ by escaping Manchester’s choking pollution. However, as he explained to his mother in April 1910, he professed little experience behind the steering wheel of such a vehicle.

  We got our car on Good Friday and spent three days running around while I practised driving. We started on our tour Tuesday, and have so far gone 500 miles [800 kilometres] . . . We have enjoyed ourselves very thoroughly. I have learnt to drive fairly well without a single incident, even of running over a chicken.

  A car is very easy to manage and far more under control than a horse. We average about 17 miles an hour [twenty-seven kilometres an hour] over country, and on a good road run along freely at 25. We can do 35 or 40 if we want to, but I am not too keen on high speeds with motor traps along the road and a ten guinea fine if I am caught. These are the woes of motorists that I hope to avoid!7

  The spoils of Rutherford’s new-found means were not channelled solely into meeting his automotive fancies. Mary welcomed the installation of a small heating unit in their Withington house that warmed the ground-floor rooms, a luxury that also meant Eileen was able to invite schoolfriends for a birthday party, even though Manchester remained in the grip of lingering winter when she celebrated the occasion in late March.

  Mary also took on the role of regular social entertainer, whether that was at the Saturday-night suppers she hosted in the home’s white-walled d
ining room before the male guests adjourned to Ernest’s study, or the Sunday-afternoon teas in the drawing room that preceded a quick run across surrounding countryside in his beloved motor car.

  Not that Rutherford was about to throttle back on his laboratory work by assuming the satisfied semi-retirement of a comfortable academic. For a year or more, he had been applying his formidable intellect to the next great sub-atomic mystery.

  * * *

  Geiger later retained vivid memories of the scene that would greet him when he went in search of Rutherford to begin another session of counting alpha particles.

  I see his quiet research room at the top of the physics building, under the roof, where his radium was kept and in which much well-known work on the emanation was carried out. But I also see the gloomy cellar in which he fitted up his delicate apparatus for the study of the alpha rays. Rutherford loved this room. One went down two steps and then heard from the darkness Rutherford’s voice reminding one that a hot-pipe crossed the room at head level, and to step over two water pipes. Then finally, in the feeble light, one saw the great man himself seated at his apparatus and straightaway he would recount in his own inimitable way the progress of his experiments, and point out the difficulties that he had overcome . . .8

  Rutherford’s mission, during these intensive and reclusive sessions, was to establish the speed and properties of those radioactive particles being emitted from precious supplies of radium. The element was sparingly used in experiments, in the form of radon gas that could be ‘milked’ every few days from the mother lode.

  Each gram of radium, the most bountiful source of Rutherford’s alpha rays, was believed to release these radioactive particles at a rate of around 34 billion per second. His ambition was to unleash them, directed by a magnetic field, through a narrow slit from within a lead-lined box and train them at a target – as if he were firing them from a gun.

  The stream of alpha particle ‘bullets’ would then be aimed at a small glass plate coated with zinc sulfide, the same material Pierre Curie had applied to his glass tube, which would glow when exposed to radioactivity. Given that it was impossible to see sub-atomic particles travelling at one-seventh the speed of light with the naked eye, Rutherford would sit hunched over a microscope placed behind the plate and manually record each ‘scintillation’, as the phosphorescent pinpricks of an alpha particle striking the treated surface were known.

  During experiments he had conducted at McGill, Rutherford had noticed that some particles could be deflected from their direct path by a degree or two if forced to pass through solid matter, such as delicate mica sheets – silicate mineral, around three-thousandths of a centimetre thick. This suggested to him that some particles were being bumped off track. When the experiment was repeated using thin strips of foil fashioned from various metals, the degrees of scattering became more and more pronounced as the atomic weight of the metals increased.

  This method required the experimenter to sit in the darkened basement for half an hour until their eyes adjusted to the gloom and they could begin to count the fleeting scintillations. As a result, the useful viewing time for each individual was restricted to around thirty minutes.

  Rutherford decided it was close work best suited to young undergraduate student Ernest Marsden. The twenty-year-old, along with Geiger, began a series of experiments using gold foil six-one hundred thousandths of a centimetre thick – roughly the equivalent of 400 gold atoms – placed at an angle of forty-five degrees to the radioactive bullets.

  Most of those fired at the foil passed directly through, while a number deviated by a degree or two, as per previous findings. But there was also evidence that some alpha particles rebounded from the foil at an angle of ninety degrees.

  Intrigued, Rutherford then instructed that the target plate be positioned virtually alongside the particle ‘gun’. The men were stunned when scintillation marks showed that around one in 8000 particles bounced back at an angle greater than ninety degrees, while some scintillations were even detected at 150 degrees or more. In other words, these bullets flying at vast speeds were occasionally being flung back in the direction from which they came by a sheet of matter so thin that most other radioactive atoms sailed through it, unhindered.

  ‘It was quite the most incredible event that has ever happened to me in my life,’ Rutherford memorably said of his most famous experiment. ‘It was almost as if you fired a 15-inch shell at a piece of tissue paper, and it came back and hit you.’9

  Neither he nor Marsden could understand how this result was possible. Initially, Rutherford reasoned that the positively charged helium bullets had been repelled by an electric or magnetic force, but then he estimated it would take the equivalent of millions of volts to force a fast-moving atom of that size and substance into reverse. So he engaged his favourite piece of laboratory equipment: his capacity to sit quietly and think.

  For more than a year, he ruminated over the results while continuing other experiments and overseeing those of his students, giving lectures and writing papers.

  It was a neat symmetry that he finalised his working theory while tucking into plum pudding on Christmas Day 1910. He was now convinced he could no longer subscribe to J.J. Thomson’s theory, which likened atomic structure to that same dessert. Rather, his new vision was built upon the celestial bodies swirling in the night sky.

  One morning early in 1911, he appeared in the doorway of Geiger’s office bearing an enormous grin. ‘Rutherford, obviously in the best of spirits, came into my room and told me that he now knew what the atom looked like and how to explain the large deflections of the alpha particles,’ Geiger would recall.

  Rutherford then sat down, and became the first human to explain the atom in accurate detail.

  In essence, Rutherford’s conception of the atom – which was little different from the way it is understood today – was that it mostly comprised empty space. He theorised that at its core (he did not begin using the term ‘nucleus’ until several years later) was a dense, hugely powerful particle that was responsible for deflecting the alpha bullets through electrostatic repulsion. A few much smaller and lighter pieces of matter orbited this highly charged core in concentric rings.

  The comparative scale of the model prompted the oft-cited analogy that, if the atom were expanded to the size of St Paul’s Cathedral in London, the particle at its heart would appear as roughly the size of a single fly. However, the density of that tightly packed core would be so great it would account for 99.975 per cent of the structure’s total mass.

  The reason why most of the alpha particle bullets fired at the gold foil sailed through unhindered was that the chances of directly hitting the central core of each atom was remote. But when that happened, the bullets were repulsed at a stunning velocity.

  Rutherford’s radical revision of the atom did more than make J.J. Thomson’s plum pudding model redundant. ‘The Rutherford model of the atom was like a solar system,’ Mark Oliphant liked to summarise years later. ‘The nucleus taking the place of the sun, and the electrons that of the planets.’10

  It fundamentally changed science’s understanding of the essential blocks from which the world is built. No longer was the atom the solid billiard-ball representation conceived by Dalton, nor gelatinous dough, as Thomson had subsequently surmised. It was now revealed, by the man whose curiosity had been stirred in the rural backwaters of remote New Zealand, that the entity that makes up all known substances and being is essentially made of nothing. It is no more than a tiny, super-charged pinprick at the middle of a whirring, blurring void.

  From what would become neatly known as the ‘gold foil experiments’, an entirely new research field – nuclear physics – was born. Arthur Eddington, the astronomer who had worked in the Cavendish Laboratory and would famously go on to help prove a number of Einstein’s theories, proclaimed Rutherford’s discovery the most important development in science since Greek philosopher Democritus proposed the existence of the atom in the fi
fth century BC.11

  Baron Bowden, an influential scientist and educator who was examined for his PhD by Rutherford and Oliphant in tandem, was unequivocal as to the impact of this moment on subsequent history.

  The achievements of Rutherford, I am sure, would not have been rivalled by anyone else for at least ten to fifteen years. If nuclear physics had not got started then, and had gone on at the usual sort of rate, we should never have arrived at the possibility of the nuclear bomb at the beginning of the Second World War.12

  * * *

  Sceptical scholars soon wondered why the negatively charged electrons that supposedly hurtled around the positively charged core of Rutherford’s new atomic model did not follow Newton’s laws. According to those centuries-old principles, they should lose their energy by radiating it away – at which point, they would be drawn into the super-charged core through electrical attraction, thus rendering the entire structure unstable.

  To explain this anomaly, Rutherford had to enlist the expertise of a theoretical physicist. An avowed experimentalist, he made no secret of the suspicion he held for those whose research skills were best exhibited on a blackboard rather than a workbench. He was known to mock-seriously chide those of his students and staff who dared discuss matters of theory by warning them: ‘don’t let me catch anyone talking about the universe in my department’.13

  However, among the Manchester ‘boys’ was a theoretician who – as would later happen with Mark Oliphant – had been drawn into Rutherford’s orbit by the force of the professor’s vision. During the 1911 Cavendish Laboratory dinner at which Rutherford was lovingly reproached for his impatience towards apparatus, Niels Bohr became so inspired by the irrepressible New Zealander’s speech that he transferred to Manchester University soon afterwards.