by P. D. Smith
* * *
Umberto Eco’s The Name of the Rose is a dark novel about zealotry and forbidden knowledge. The Franciscan monk Brother William of Baskerville, whose name hints knowingly at the scientific detective Sherlock Holmes, is investigating a series of monastic murders. He has a keen eye for ‘the evidence through which the world speaks to us like a great book’.16 The solution to this medieval mystery seems to lie in a profane manuscript which was read by all the victims. In this godly community, someone wants to teach the monks a lethal lesson about the dangers of forbidden knowledge.
This fatal manuscript has its deadly equivalent in the atomic age. For there is a real text whose pages are literally lethal to its readers. The three black notebooks used by Marie Curie in her experiments from December 1897 are still so radioactive that they have to be kept in a lead safe in the Bibliothèque Nationale in Paris. Anyone wishing to consult them must sign a form acknowledging that they are aware of the risks. They are among the most haunting documents of the atomic age.
The Curies’ makeshift laboratory, its furniture and Marie’s notebooks became radioactive by contact with the chemicals processed by the first two atomic scientists. Visitors at the time reported that the walls of the laboratory ‘glow visibly at night’.17 Marie Curie died in 1934 of leukaemia contracted through her exposure to radioactivity.
It was Henri Becquerel’s discovery of natural radioactivity, a few months after Röntgen’s X-rays were revealed, that propelled Marie Curie into her dangerous quest for radioactive elements. Unlike Röntgen’s X-rays, the discovery of the so-called Becquerel rays provoked little public interest. But the fact that uranium emitted rays apparently similar to X-rays had a greater impact on the course of the next century than any other scientific discovery.
Henri Becquerel came from a thoroughly scientific family. His father and grandfather had both been eminent scientists. Becquerel’s own son would also follow in his father’s footsteps. In the 1840s, Becquerel’s grandfather told his son: ‘I will never be satisfied with explanations they give why some chemicals and minerals shine in the dark. Fluorescence is a deep mystery and nature will not give up the secret easily.’18 Father and son dedicated their lives to the study of this strange phenomenon, which most people thought was caused by the slow release of absorbed sunlight.
When Becquerel heard that Röntgen had discovered rays that could affect photographic plates, he began investigating whether visible fluorescence was accompanied by invisible X-rays. He assumed that sunlight was needed to make the fluorescent chemicals active, and so his experiment consisted of leaving sealed photographic plates, on which some uranium sulphate had been placed, out in the sun. But a spell of cloudy weather intervened, and Becquerel put his experimental apparatus away, locking the uranium sulphate and the photographic plate in a dark drawer. It was lucky that he did, and even more fortunate that he later decided to develop the plate. For when he did so, he was amazed to see an image. By the end of February 1896 he could tell the French Academy of Sciences that ‘there is an emission of rays without apparent cause. The sun has been excluded.’19 It was an astonishing discovery: matter produced rays which came not from the sun but from some unknown energy source deep within itself.
By the end of 1897, Marie Curie had just given birth to her first child, Irène. The 30-year-old chemist was now on the lookout for a suitable subject for her doctoral thesis. She was intrigued by the idea of Becquerel rays, and set about investigating them by testing as many metals and minerals as she could. Both Becquerel rays and X-rays had the unusual effect of enabling air to conduct electricity, and Curie began looking for elements with this property. She soon found that the dark, lustrous mineral pitchblende, which contains uranium, made air more conductive than pure uranium. This suggested the presence of some other element that was a more powerful emitter of Becquerel rays than even uranium. Curie had found a subject for a doctorate: isolating whatever substance was responsible, and explaining the phenomenon that Becquerel had discovered. She set to work using pitchblende from the mines of St Joachimsthal in Bohemia (Jáchymov in today’s Czech Republic).
Ernest Merritt, Professor of Physics at Cornell University, introduced Marie Curie’s discoveries to the readers of a contemporary popular magazine. He came up with an apt analogy to describe the difficulty of the task Curie faced in separating radium from pitchblende. Her job, he said, was like that of a ‘detective who starts out to find a suspected criminal in a crowded street’. Pitchblende, a heavy brown-black uranium ore, is ‘one of the most complex of minerals, containing twenty or thirty different elements, combined in a great variety of ways’.20 There is a single gram of radium in seven tons of pitchblende. But Marie Curie was a remarkable and tenacious chemical detective.
Merritt’s article was accompanied by two striking illustrations. One was a photograph of a chunk of pitchblende in normal light. The other was rather more dramatic. It was taken by placing the rock directly onto a photographic plate. No camera was used: the Becquerel rays themselves made the exposure. In this photograph, said Merritt, ‘every crack and seam where radium is present has made its impression, while the ordinary rock in which the ore is embedded has left no trace’.21 This rock looks like a volcano at night, with glowing lava streaming down its fissures. The photograph creates an eerie impression, and powerfully evokes the hidden forces within matter. Many of the first fictional descriptions of atomic explosions would liken them to erupting volcanoes.
Formed billions of years ago in the hearts of stars which exploded as supernovae, blasting their contents through our Galaxy, uranium provides the main source of heat within our planet. The heat from its radioactive decay also drives the tectonic shifting of the continents. Ironically, given the future importance of uranium in the development of nuclear weapons, Merritt comments: ‘If uranium had proved to be the only radioactive substance, I doubt whether the subject would have aroused very general interest.’ It seems scarcely believable, but in 1904, uranium seemed a rather unexciting element. In contrast, the properties of radium were dramatic and, most importantly for the media, photogenic. For as Professor Merritt commented dryly, ‘the scientific investigator is by no means devoid of the taste for something sensational’.22
By the end of 1898, Marie Curie had returned from what Merritt called her ‘journey into an unexplored land’ with truly sensational news – not one but two new elements.23 It had taken her a year. The first one she named polonium, in honour of her Polish homeland. The other she called radium, from the Latin for ray, radius. In her scientific papers announcing the new elements, she also coined the term ‘radioactivity’.
Polonium is more radioactive than radium or uranium. A milligram of polonium-210 emits as many alpha particles as 5 grams of radium. A capsule containing half a gram of polonium-210 can reach a temperature of 500°C and provide a lightweight heat source to power thermoelectric cells in artificial satellites. But polonium is also more difficult to isolate. There are about 100 micrograms in a ton of uranium ore. Isolating it is like finding a grain of salt in a sack of sugar.
Like polonium, radium is luminescent, and has a blue glow. ‘The light given out is sometimes so bright that it is possible to read by it,’ Merritt told his readers.24 Marie Curie once talked about the joy she felt on entering her laboratory at night and seeing the rows of faintly glowing tubes. They were like fairy lights, she said. She even used to keep some radium salts by her bed so she could see it glowing in the dark – an atomic nightlight. Radium metal is pure white but blackens in air. It emits alpha, beta and gamma rays. Radium-226 loses just 1 per cent of its radioactivity in 25 years, decomposing ultimately into lead. Its rays cause diamonds to shine ‘with a clear phosphorescent light’.25 Imitation stones do not, as more than one shocked lady attending a lecture on radium discovered to her cost. But radium rays are also dangerous. Marie and Pierre Curie soon found that exposure for just five minutes was enough to produce nasty sores, although strangely these did not appear for several d
ays.
From 1899, Marie Curie worked her way through tons of pitchblende, delivered to her from the St Joachimsthal mine. Mixed in with the sackfuls of reddish-brown dust were pine needles from the Bohemian forest where the pitchblende had been dumped after the uranium had been extracted. Marie did the chemical work of separation while Pierre concentrated on the theoretical physics. The Ecole de Physique et de Chimie Industrielles in Paris, where Pierre taught, gave the Curies a disused medical dissection room to work in. Marie described it as ‘a wooden shed with a bituminous floor and a glass roof which did not keep the rain out’.26 The Chemist Wilhelm Ostwald called it a cross between a stable and a potato shed. Boiling hot in summer and freezing in winter, it was totally inadequate as a laboratory. But Marie Curie was not one to complain.
Although she appeared shy and reserved to those who met her for the first time, Curie was in fact a determined and single-minded woman. By all accounts she relished what was a formidable challenge of separating out the new elements: ‘I had to work with as much as 20 kilograms of material at a time, so that the hangar was filled with great vessels full of precipitates and of liquids. It was exhausting work to move the containers about, to transfer the liquids, and to stir for hours at a time, with an iron bar, the boiling material in the cast-iron basin.’27
It took Marie Curie almost four years of back-breaking work to isolate one-tenth of a gram of radium chloride. By July 1902, she had enough to convince even the sceptical world of science ‘that radium is truly a new element’.28 The result of her dangerous labours was a rather ordinary-looking substance: white crystals, like coarse-grained salt. But as Merritt told his readers in 1904, ‘a pinch of this innocent-looking salt costs more than a thousand dollars’.29 Radium was at least a hundred times more valuable than gold.30 This was far more than even the alchemists could have dreamed of. But more important than its monetary value was the wealth of knowledge it promised. As one contemporary put it, locked up in this ‘strange substance’ were all ‘the riddles of matter and energy’.31
The twentieth century has been called the century of the electron, the subatomic particle that makes possible our electronic computer age. In the year that Marie Curie began her search for new radioactive elements, on the other side of the English Channel a Cambridge physicist, J. J. Thomson, made the first discovery of a particle smaller than an atom – the negatively charged electron. It enabled Thomson to construct a theory of atomic structure that would later become known by the rather wonderful name of the plum pudding model (or, as Thomson himself put it rather less memorably, ‘a number of negatively electrified corpuscles enclosed in a sphere of uniform positive electrification.’32)
According to Thomson, electrons were unimaginably small, a mere fraction of the size of the smallest atom, hydrogen, which was itself so tiny that a crowd of them ‘equal in number to the population of the whole world would be too small to have been detected by anymeans then known to science’.33 In fact, there is no consensus on its size, or even on what ‘size’ really means when applied to the electron. Estimates vary from 20,000 times smaller than an atom, right down to it being a dimensionless point. The electron possesses charge, and is responsible for creating electric fields and thus magnetic fields. These in turn give rise to electromagnetic waves: radiation across a huge spectrum of wavelength and frequency, from radio waves, through visible light, to X-rays and gamma rays. The existence of this subatomic particle was the first evidence that atoms were not solid and might even be divisible. John Dalton’s atomic theory, which had ruled unchallenged for a century, suddenly looked distinctly shaky. Was it possible that atoms could be split after all?
In 1898, J. J. Thomson’s brilliant 27-year-old assistant, Ernest Rutherford, deepened the understanding of atomic structure still further by identifying and naming alpha, beta and gamma rays as forms of radiation. All radiation is dangerous to humans but some forms are more harmful than others. Alpha radiation consists of relatively heavy particles (the positively charged nuclei of helium atoms) which can be easily stopped, even by a sheet of paper. Beta radiation is more penetrating and can cause skin injury. It consists of lighter particles, which were later realized to be electrons. Like light and X-rays, gamma rays are forms of electromagnetic radiation. They can travel several metres through air and are extremely dangerous, potentially lethal. Cobalt-60, the radioactive product of the deadly cobalt bomb discussed at the Round Table in 1950, is a powerful source of gamma radiation.
Ernest Rutherford was born in New Zealand, to where his grandfather, a wheelwright from Dundee, Scotland, had emigrated in 1843. After graduating with a double first in mathematics and physical science from Canterbury College, Christchurch, he won a scholarship to Cambridge in 1894. According to those who knew him, Rutherford never quite lost the gruff manner of a pipe-smoking colonial farmer. He was, said Paul Langevin, a ‘force of nature’.34 Another colleague compared him to a battleship ploughing through a stormy sea. A brilliant experimentalist who famously commented that all science was either physics or stamp collecting, Rutherford was notoriously sceptical about new theories. A visitor to Cambridge’s Cavendish Laboratory, which he directed in typically no-nonsense style from 1919, once asked about the significance of Einstein’s theories. ‘That stuff!’ harrumphed Rutherford. ‘We never bother with that in our work.’35
Following his researches with Thomson at the Cavendish, Rutherford was offered the Macdonald Chair of Physics at McGill University, Montreal, in 1898. Once there, Rutherford focused all his energies on understanding radioactivity. He had noticed that, like radium, the naturally radioactive element thorium produced a gas, or ‘emanation’ as it was then called. In October 1901 he asked the 24-year-old chemist Frederick Soddy to find out what it was. Soddy, born at Eastbourne in Sussex, had spent a couple of years researching at Oxford before taking a post as chemistry demonstrator at McGill. He recalled that at this time Rutherford was an ‘exuberant, natural young man with a moustache and breezy manner, full of the joie de vivre of the indefatigable investigator… There was a spirit of adventure about him coupled with a dogged determination to reach his quest.’36
The two men became acquainted at a meeting where Soddy had presented a paper on the indivisibility of the atom. He engaged in a characteristically robust debate with the physicists – including Rutherford – arguing against the existence of subatomic particles, and concluded with the comment: ‘I feel sure chemists will retain a belief in, and a reverence for, atoms as concrete and permanent entities, if not immutable, certainly not yet transmuted.’37 But when Soddy investigated the problem Rutherford had set him, he found that the thorium emanation or ‘thoron’ was an inert gas, possibly argon (it was subsequently identified as an isotope of radon). If true, this was a shocking discovery. How was it possible that the element thorium, a solid, was turning into another element, a gas? According to Dalton and everything that Soddy had ever been taught, elements could not change. Transmuting one element into another was the preserve of alchemists.
It was true that some people, even at the dawn of the twentieth century, still clung doggedly to the dreams of alchemy. The Swedish playwright August Strindberg became obsessed with transmuting lead oxide into gold in the 1890s. He even published a text on chemistry, Antibarbarus, in 1894 and claimed to have successfully created gold. Despite his hopes of winning the Nobel Prize in Chemistry, few believed him, due in part to his unconventional views on science. Strindberg had once been spotted by the owner of an open-air restaurant injecting an apple hanging from a tree with a syringe full of morphia. When the worried owner asked what he was doing, Strindberg replied that he wanted to observe the apple’s reaction. ‘I am a botanist,’ he explained. The patron decided he was probably from the nearby asylum.38
Such eccentric behaviour might be expected of a man who claimed to be walking in the footsteps of the alchemists. But Frederick Soddy was a trained chemist, and the most eccentric thing Rutherford ever did was to stride around his laboratory singing
‘Onward Christian Soldiers’. Nevertheless, Soddy could see that there was no alternative explanation: ‘if a chemist were to separate, say, silver from lead and found that as fast as he separated it the silver reformed in the lead, the only possible conclusion would be that lead was changing spontaneously into silver’.39 He recalled turning to his colleague and saying, ‘Rutherford, this is transmutation: the thorium is disintegrating and transmuting itself into argon gas.’40
Rutherford was equally shocked: ‘They’ll call us alchemists, charlatans, and try to cut off our heads!’41
In 1902, Rutherford and Soddy announced their astonishing findings to the world. Atoms did indeed spontaneously disintegrate, creating energy in the process. Their so-called ‘disintegration hypothesis’ showed that radioactive substances such as thorium and radium were in a state of constant but gradual disintegration. Their atoms were perpetually firing off streams of energetic, bullet-like particles. The process was likened at the time to a ‘series of explosions’.42 Transmutation and radioactivity were the same process. As Soddy put it, the ‘expulsion of rays is the break-up of the atom’.43
If they had been proved wrong, it could have been fatal for the careers of these two young scientists. But they were right, and both men would go on to win Nobel prizes. Rutherford and Soddy also established the principle of radioactive decay. We talk now of the half-life of, for example, thoron, as being one minute, so that, in Soddy’s words, ‘60 seconds from any time of starting, the quantity of thoron is only half what it was to begin with’.44 Soddy recalled these days as being among the most exciting of his life, filled with ‘intense mental exaltation’. Through their work on the theory of atomic disintegration, the pieces of the radioactivity ‘jig-saw puzzle’ were gradually being fitted into a coherent whole.45
In the autumn of 1902, Rutherford and Soddy used what was at the time the latest in laboratory technology: a liquid-air machine. But they were not interested in repeating Charles Tripler’s spurious experiments to create free energy. Instead, they used liquid air to cool the gases produced by thorium and radium to pure liquids, thus helping to demonstrate to a sceptical scientific establishment that one element could indeed give birth to a new one. The disintegration of the radium atom to yield an atom of radon gas and an alpha particle was described by Frederick Soddy as ‘surely the strangest transformation of matter in the whole history of chemical discovery!’46 It heralded a revolution in the way people thought about matter, one that would yield an energy source more awesome than even Tripler could have imagined.
