The Basis of Everything

by Andrew Ramsey

  Earlier in the war, Peierls had been approached by British intelligence personnel for his opinion on how the activities of Germany’s leading physicists might best be monitored. It was an attempt to ascertain how far the Third Reich had progressed towards harnessing the frightening power within uranium atoms.

  Peierls had suggested keeping track of their published research output, which would verify whether they were still in their usual places of work or had been collectively sequestered elsewhere. He then offered to study the German-language science journals as they became available, for that purpose. It was the worryingly real fear that Hitler was engaged, and possibly ahead, in the race for the bomb that drove the pair relentlessly on.

  While Frisch was focused on isotope separation, Peierls – who had so craved a part in Britain’s anti-war effort that he had successfully applied to join Birmingham’s auxiliary fire service – immersed himself in fission theory. He understood that if the mass of material was too small, there was a high chance that the neutrons would escape without initiating secondary fission, thus rendering the material inert. Too large a mass, and the process would race away uncontrolled and effectively self-destruct.

  Producing a sustainable, managed chain reaction would require a very specific volume of fissionable material. The thesis on which Peierls based his initial calculations, published by French theoretical physicist Francis Perrin earlier in 1939, estimated that amount to be forty-four tons. If, however, the uranium was encased within lead or iron, from which neutrons that escaped might be reflected back into the reaction, it could possibly be reduced to thirteen tons.

  Perrin’s calculations were loosely supported by James Chadwick at Liverpool, who had advised Tizard that it could be anywhere between one and forty tons. This reinforced the idea put forward by Niels Bohr, and reiterated by Frisch in his report for the Chemical Society, that the size of any weapon utilising a uranium chain reaction would be so huge that it could not be transported by aircraft, and was therefore of little practical use.

  However, by improving the calculations in Perrin’s paper, Peierls showed that the mass might be significantly lower, though still in the order of tons. He discussed his findings with Frisch, who saw no issue with making them public, given that they echoed the existing literature, which ruled out the likelihood of a bomb. Peierls therefore submitted his paper for publication by the Cambridge Philosophical Society.

  Both men were now on the public record as having dismissed the prospect that uranium fission might fuel a bomb, but their search continued. Frisch focused on the one unexplored method by which an explosive chain reaction might be set off in uranium. It had been ruled out as unachievable through the firing of fast and slow neutrons at uranium-238. And his own recently published report showed that slow neutron bombardment of uranium-235 might yield energy for power generation, but at an insufficient rate for use as a weapon. The only outstanding scenario was to consider the effect that fast neutrons unleashed upon uranium-235 might bring.

  ‘I wondered – assuming that my Clusius separation tube worked well – if one could use a number of such tubes to produce enough uranium-235 to make a truly explosive chain reaction possible, not dependent on slow neutrons,’ Frisch later recalled. ‘How much of the isotope would be needed?’16

  The scarcity of insight into uranium-235 meant that Frisch had to estimate a crucial detail, the fission cross-section of the difficult to obtain isotope, so that he could insert it into the mathematical formula that Peierls had refined in his paper. A cross-section is a measurement employed by physicists to indicate the likelihood that a specific nuclear reaction will or will not take place.

  The answer that emerged when that approximate figure was used, if such a volume of uranium-235 could somehow be produced, left Frisch reeling.

  To my amazement, it was very much smaller than I expected; it was not a matter of tons, it was something like a pound or two. I discussed the result with Peierls at once. I had worked out the possible efficiency of my separation system with the help of Clusius’s formula, and we came to the conclusion that with something like 100,000 similar separation tubes one might produce a pound of reasonably pure uranium-235 in a modest time, measured in weeks. At that point we stared at each other and realised that an atomic bomb might after all be possible.17

  Not only possible. If the methodology and the mathematics employed by two ‘enemy aliens’ using reclaimed laboratory space at a university up to its neck in top-secret radar work had found the key to the most destructive force humankind could conjure, then surely Germany’s brilliant physicists gathered at Berlin’s Kaiser Wilhelm Institute were on the same path. If they hadn’t already reached the destination.

  Gripped by intense curiosity and surging fear, Frisch and Peierls went through more calculations to prove their astonishing theory. It was also necessary to project how much energy might be released in the fractions of a second it would take such a chain reaction to unfold. As Peierls filled in the equation by hand, the pair’s astonishment was compounded.

  ‘A rough estimate – on the back of the proverbial envelope – showed that a substantial fraction of the uranium would be split, and that therefore the energy release would be the equivalent of thousands of tons of ordinary explosive,’ Peierls would explain.

  ‘We were quite staggered by these results . . . As a weapon, it would be so devastating that, from a military point of view, it would be worth the effort of setting up a plant. In a classical understatement, we said to ourselves “even if this plant costs as much as a battleship, it would be worth having”.’18

  As the magnitude of their find washed over them, Frisch – a German national by dint of Austria’s annexation, and already fearful that he might be bound for a British internment camp – stammered: ‘shouldn’t someone know about this?’

  That someone was their academic superior, Mark Oliphant.

  * * *

  The professor listened in wide-eyed silence as the pair detailed their research, and nodded in schoolmasterly admiration as they presented their sound conclusions. He could see no initial glaring faults with the science, even if the theory tested him, and he instructed them to write it all down in a comprehensive report. Observing strictest secrecy, of course.

  Such was the paranoia over possible leakage of their revelations that the men deemed the task of committing them to print too sensitive to be entrusted to the university’s administrative staff. Instead, Peierls employed his basic typing skills and took on stenographic duties.

  The pair worked from Peierls’s small office in the single-level Nuffield Building, and with the door locked tight, the only relief from spring’s first burst of warmth came by opening the window, which faced onto a section of garden between Birmingham’s red-brick edifices.

  Suddenly, as they discussed details that might realistically shape the ongoing war, a face appeared at the window, having arrived with neither audible warning nor logical reason. Unless – as the speechless pair hunched over the metal typewriter immediately suspected – it was an act of espionage.

  ‘However, the “eavesdropper” was a lab technician who had planted some tomatoes along the south wall of the building, and was tending them in a spare moment,’ Peierls would later recount. ‘He had moved along bending over the plants and straightened up by our window. He had of course not paid any attention to what we were saying.’19

  The five foolscap pages of single-spaced text, punctuated by hand-drawn annotations where the demands of algebraic equations exceeded Peierls’s secretarial skills, were completed with a single carbon copy. They were then slipped inside a blank envelope, for hand delivery to Oliphant’s office.

  * * *

  There, in the opening week of March 1940 and behind the polished oak door set within a floor-to-high-ceiling timber wall, Oliphant became the first (apart from its authors) to read one of the war’s most influential documents. History would subsequently know it as the Frisch–Peierls Memorandum. Upon reaching the end,
he set it down, gazed for a few moments through the lead-lined windows towards the physics department car park, then picked it up to begin rereading.

  The report had been prepared in two parts. The first, entitled ‘On the Construction of a “Super-Bomb” Based on a Nuclear Chain Reaction in Uranium’, contained the technicalities, and outlined the premise of their calculations. Among the thorough explanations of uranium fission, the process for isotope separation, and the acknowledgment that some of the assumptions were based on guesswork because crucial data remained unknown, there were phrases that fairly leaped at Oliphant from the page.

  ‘If the reaction proceeds until most of the uranium is used up, temperatures of the order of 1010 degrees and pressure of about 1013 atmospheres are produced.’ In lay terms, a fireball similar in intensity to the sun’s interior, and a shockwave greater than the force exerted at the earth’s core, where metal is liquefied. And then: ‘The energy liberated by a 5kg bomb would be equivalent to that of several thousand tons of dynamite.’20

  The second part bore the heading ‘The Properties of a Radioactive “Super-Bomb”’, and was even more graphic. It was a less technical document, outlining the men’s conclusions and detailing the effects such a device would likely bring. Nobody who read those two pages could claim doubt as to what the development of an atomic bomb would mean for humanity.

  The blast from such an explosion would destroy life in a wide area. The size of this area is difficult to estimate, but it will probably cover the centre of a big city. In addition, some part of the energy set free by the bomb goes to produce radioactive substances, and these will emit very powerful and dangerous radiations.

  The effects of these radiations is greatest immediately after the explosion, but it decays only gradually and even for days after the explosion any person entering the affected area will be killed. Some of this radioactivity will be carried along with the wind and will spread the contamination; several miles downwind this may kill people.21

  The document went on to explain how the bomb could be constructed, with the concentrated uranium manufactured in two sub-critical parts – each of insufficient mass to enable fission – that would be kept separated ‘by a few inches’ during transportation to the proposed target, to avoid premature detonation. A mechanism within the bomb would then force the pieces together at the desired drop point, to set loose the chain reaction.

  The report also presented five conclusions, accompanied by a caveat that, as scientists, neither Frisch nor Peierls considered himself qualified to pass comment on the strategic value of such a weapon. However, they did reiterate that while the potential of such a ‘super-bomb’ would make it ‘practically irresistible’ because no known material or structure could withstand it, it would also bring far-reaching after-effects.

  The authors noted that although they held no evidence to suggest that any other scientists had reached this discovery, it was ‘quite conceivable’ that Germany was closing in on the same conclusions. And given that there existed no effective shelter from the destruction it would bring, the only plausible form of defence would be to threaten retaliation with a similar weapon.

  ‘Since the separation of the necessary amount of uranium is, in the most favourable circumstances, a matter of several months, it would obviously be too late to start production when such a bomb is known to be in the hands of Germany, and the matter seems, therefore, very urgent.’22

  If the spectre of this hideous tool under the control of Hitler’s Germany did not darken the soul, then the suggestion that Britain might require specialist squads armed with measuring instruments to detect the location and toxicity of invisible radiation clouds if such a bomb were launched surely did.

  The memorandum even considered, in passing, the moral debate that would rage from that day onward: whether Britain might consider such a weapon an unpalatable option, given that its impact could not be limited to purely military targets.

  Owing to the spread of radioactive substances with the wind, the bomb could probably not be used without killing large numbers of civilians, and this may make it unsuitable as a weapon for use by this country. (Use as a depth charge near a naval base suggests itself, but even there it is likely that it would cause great loss of civilian life by flooding and by the radioactive radiations.)23

  In the decades of debate that followed the bombing of Hiroshima, Otto Frisch and Rudolf Peierls would often be asked why – upon establishing the heinous consequences of the weapon they had imagined – they did not immediately abandon their investigations.

  Frisch’s response would be unequivocal, and the same as Peierls’s and Oliphant’s when that ethical question was posed to them. ‘The answer is very simple. We were at war, and the idea was reasonably obvious; very probably some German scientists had had the same idea and were working on it.’24 As Peierls put it fifty years after the war’s end: ‘The thought of this weapon exclusively in Hitler’s hands was a nightmare.’25

  * * *

  Oliphant stared at the pages, which were already turning soft in his clammy fingers. To the best of his knowledge, and as history would subsequently attest, he was one of three people on the planet at that moment who understood that the power of hell could at some point feasibly be delivered from the sky, to any chosen place on earth. He had quizzed Frisch and Peierls about their conclusions, and his questions were comprehensively addressed in the document he held. He also understood that if the vision of destruction outlined to him were to be realised during the conflict that continued to escalate across the Channel, then there were perhaps no better hands in which that shocking memorandum might rest.

  Certainly, there was little more that ‘enemy aliens’ Frisch and Peierls could achieve with it. By contrast, Oliphant knew the hierarchy of Britain’s war machinery, and how to get wheels moving within it. His conscience was also conflicted with the realisation that it was the partnership he had effectively forged – through his offer of safety from persecution – that had precipitated the five-page global death warrant now resting on his desk.

  Oliphant had previously shown few qualms about engaging in a bit of interventionist obstruction of bureaucracy, so he might conceivably have simply returned the memorandum to its authors. Or it could have been slid quietly among other papers in a bookcase.

  Instead, sitting silent and alone, at a junction where history and humanity diverged, Oliphant removed a sheet of notepaper from the top drawer of his desk and began writing a covering letter that his trusted secretary, Miss Hytch, would later type.

  I have considered these suggestions in some detail and have had considerable discussion with the authors . . . with the result that I am convinced that the whole thing must be taken rather seriously, if only to make sure that the other side are not occupied in the production of such a bomb at the present time.

  In fact, I view the matter so seriously that I feel that immediate steps should be taken to consult with the necessary authorities concerning the possibilities of palliative measures if such a bomb should be used . . . I should be very grateful if you should bring this matter to the attention of those who should be informed, though I think there are two reasons why considerable secrecy should be observed.

  Firstly, if we should tackle the manufacture of such a bomb ourselves a great deal of the effect it might produce would be lost if knowledge of its manufacture should be available beforehand.

  Secondly, if the enemy are preparing such a bomb, which is not unlikely, we should endeavour to obtain information to this effect through our Secret Service without revealing that we ourselves are aware of the possibility.

  I hope you will not think this a purely hare-brained scheme. It may well turn out to be impracticable, but in any case it is put forward with sincerity by Frisch and Peierls, and with considerable belief by myself.26

  The finished letter was then affixed to the front of the five pages of typed text, and sealed inside an envelope marked ‘Top Secret’. Oliphant then arranged its urgent
delivery to the man he knew offered the most pragmatic hope of ensuring an atomic bomb became a reality.

  It arrived on the desk of Henry Tizard on the morning of Tuesday, 19 March 1940.

  18

  MAUD

  Birmingham and London, 1940 to 1941

  The one unfamiliar face among the four that greeted Mark Oliphant when he arrived at Burlington House, mid-afternoon on 10 April 1940, confirmed the seriousness of the situation he had helped precipitate. Three weeks had elapsed since the Frisch–Peierls Memorandum was forwarded to Henry Tizard, whose response followed the best bureaucratic precedents – albeit with a rare undertone of urgency.

  ‘What I should like,’ Tizard wrote to Oliphant in response to the confronting document, ‘would be to have quite a small committee to sit soon to advise what ought to be done, who should do it, and where it should be done.’1

  The first gathering of this select group took place beneath a portrait of Isaac Newton in the main committee room of Burlington House, where the Royal Society had met for almost a century. Oliphant knew the room from previous visits, including the first, three years earlier, when he had been inducted as a fellow. He also understood that the meeting chamber was set sufficiently deep within the cobbled Annenberg Courtyard to ensure that noise from bustling Piccadilly, immediately beyond the building’s grand Palladian façade, would not intrude upon deliberations.