50 Although elements 93 and 94, neptunium and plutonium, were created in 1940, their existence was not made public until after the war. They were given provisional names, when they were first made, of ‘extremium’ and ‘ultimium,’ because it was thought impossible that any heavier elements would ever be made. Elements 95 and 96, however, were created in 1944. Their discovery was not made public in the usual way – in a letter to Nature, or at a meeting of the Chemical Society – but during a children’s radio quiz show in November 1945, during which a twelve-year-old boy asked, ‘Mr. Seaborg, have you made any more elements lately?’
Chapter Seventeen: A Pocket Spectroscope
51 Auguste Comte had written, in his 1835 Cours de la Philosophie Positive:
On the subject of the stars, all investigations which are not ultimately reducible to simple visual observations are…necessarily denied to us. While we can conceive of the possibility of determining their shapes, their sizes, and their motions, we shall never be able by any means to study their chemical composition or mineralogical content.
Chapter Eighteen: Cold Fire
52 Uncle Abe told me something of the history of matches, how the first matches had to be dipped into sulphuric acid to light them before ‘lucifers’ – friction matches – were introduced in the 1830s, and how this led to a huge demand for white phosphorus over the next century. He told me of the awful conditions under which match girls worked in the factories and of the terrible disease, ‘phossy-jaw,’ they often got, until the use of white phosphorus was banned in 1906. (Only red phosphorus, far more stable, and far safer, was subsequently used.)
Abe also spoke of the hellish phosphorus bombs used in the Great War, and how there was a move to ban these, as poison gas had been banned. But now, in 1943, they were being used freely once again, and thousands of people on both sides were being burned alive in the most agonizing way possible.
53 Phosphorus, oxidizing slowly, was not the only element to glow when exposed to air. Sodium and potassium did this too, when they were freshly cut, but lost their luminosity in a few minutes as the cut surfaces tarnished. I found this by chance as I was working in my lab late one afternoon, as it gradually darkened into dusk – I had not yet switched on the light.
54 Equally important were cathode-ray tubes, which were now being developed for television. Abe himself had one of the original television sets of the 1930s, a huge, bulky thing with a tiny circular screen. Its tube, he said, was not much different from the cathode-ray tubes that Crookes had developed in the 1870s, except that its face was coated with a suitable phosphor.
Cathode-ray tubes in use for medical or electronic apparatus were often coated with zinc silicate, willemite, which emitted a brilliant green light when bombarded, but for television one needed phosphors that would give a clear, white light – and if color television was to be developed, one would need three separate phosphors with exactly the right balance of color emissions, like the three pigments in color photography. The old dopants used in luminous paints were quite unsuitable for this; much more delicate and precise colors were needed.
55 Uncle Abe also showed me other types of cold light. One could take various crystals – like uranyl nitrate crystals, or even ordinary cane sugar – and crush them, with a mortar and pestle, or between two test tubes (or even one’s teeth), cracking the crystals against one another – this would cause them to glow. This phenomenon, called triboluminescence, was recognized even in the eighteenth century, when Father Giambattista Beccaria recorded:
You may, when in the dark frighten simple people only by chewing lumps of sugar, and, in the meantime, keeping your mouth open, which will appear to them as if full of fire; to this add, that the light from sugar is the more copious in proportion as the sugar is purer.
Even crystallization could cause luminescence; Abe suggested that I make a saturated solution of strontium bromate and then let it cool slowly in the dark – at first nothing happened, and then I began to see scintillations, little flashes of light, as jagged crystals formed on the bottom of the flask.
56 The same phenomenon, I read, had been used ingeniously to make self-luminous buoys – these were encircled by rings of strong glass tubing containing mercury under reduced pressure, which would be swirled against the glass and electrified by the motion of the waves.
Chapter Twenty: Penetrating Rays
57 Shoe shops everywhere in my boyhood were equipped with X-ray machines, fluoroscopes, so that one could see how the bones of one’s feet were fitting in new shoes. I loved these machines, for one could wiggle one’s toes and see the many separate bones in the foot moving in unison, in their almost transparent envelope of flesh.
58 Dentists were especially at risk, holding small X-ray films inside their patients’ mouths, often for minutes at a time, for the original emulsions were very slow. Many dentists lost fingers by exposing their hands to X-rays in this way.
59 Henri Becquerel’s grandfather, Antoine Edmond Becquerel, had launched the systematic study of phosphorescence in the 1830s and published the first pictures of phosphorescent spectra. Antoine’s son, Alexandre-Edmond, had assisted in his father’s research and invented a ‘phosphoroscope,’ which allowed him to measure fluorescences that lasted as briefly as a thousandth of a second. His 1867 book, Lumiere, was the first comprehensive treatment of phosphorescence and fluorescence to appear (and the only one for the next fifty years).
Chapter 21: Madame Curie’s Element
60 In 1998 I spoke at a meeting for the centennial of the discovery of polonium and radium. I said that I had been given this book when I was ten, and that it was my favorite biography. As I was talking I became conscious of a very old lady in the audience, with high Slavic cheekbones and a smile going from one ear to the other. I thought, ‘It can’t be!’ But it was – it was Eve Curie, and she signed her book for me sixty years after it was published, fifty-five years after I got it.
61 Becquerel had been the first to note the injury that might result from radioactivity – he discovered a burn on himself after carrying a highly radioactive concentrate in his waistcoat pocket. Pierre Curie explored the matter, allowing a deliberate radium burn on his arm. Yet he and Marie never fully faced the dangers of radium, their ‘child.’ Their laboratory, it was said, glowed in the dark, and both, perhaps, were to die from its effects. (Pierre, weakened, died in a traffic accident; Marie, thirty years later, from an aplastic anemia.) Radioactive specimens were sent freely in the post, and handled with little protection. Frederick Soddy, who worked with Rutherford, believed that handling radioactive materials had made him sterile.
And yet there was ambivalence, for radioactivity was also seen as benign, as healing. Besides thorium inhalers, there was thorium toothpaste, made by the Auer Company (Auntie Annie used to keep her dentures overnight in a glass with ‘radium sticks’), and the Radioendocrinator, containing radium and thorium, to be worn around the neck to stimulate the thyroid or around the scrotum to stimulate the libido. People went to spas to take the radium water.
The most serious problem arose in the United States, where doctors prescribed the drinking of radioactive solutions such as Radithor as rejuvenating agents, as well as to cure stomach cancer or mental illness. Thousands of people drank such potions, and it was only the highly publicized death in 1932 of Eben Byers, a prominent steel magnate and socialite, that put an end to the radium craze. After consuming a daily radium tonic for four years, Byers developed severe radiation sickness and cancer of the jaw; and he died grotesquely as his bones disintegrated, like Monsieur Valdemar in the Edgar Allan Poe story.
62 Retaining his flexibility of mind to the last, Mendeleev renounced his Etheric hypothesis the year before he died, and acknowledged his acceptance of the ‘unthinkable’ – transmutation – as the source of radioactive energy.
63 The Ether was pressed into many other uses, too. For Oliver Lodge, writing in 1924, it was still the needed medium for electromagnetic waves and gravitation, even tho
ugh the theory of relativity, by this time, was widely known. It was also, for Lodge, the medium that provided a continuum, a matrix in which discrete particles, atoms and electrons, could be embedded. Finally, for him (as for J.J. Thomson and many others), the Ether took on a religious or metaphysical role, too – it became the medium, the realm, where spirits and Mind-at-large dwelled, where the life force of the dead maintained a sort of quasi-existence (and could perhaps be summoned forth by the efforts of mediums). Thomson and many other physicists of his generation became active members, founders, of the British Psychical Society, a reaction, perhaps, against the materialism of the time and the perceived or imagined death of God.
64 After reading about this, I wondered whether any radioactive substances actually felt warm to the touch. I had small bars of uranium and thorium, but they felt as cool as any other metal bars. I once held Uncle Abe’s little tube, with its ten milligrams of radium bromide, in my hand, but the radium was no bigger than a grain of salt, and I felt no warmth through the glass.
I was fascinated to learn from Jeremy Bernstein that he once held a sphere of plutonium in his hands – the core of an atomic bomb, no less – and found it uncannily warm to the touch.
Chapter Twenty-Three: The World Set Free
65 Marie Curie’s own laboratory notebooks, a century later, are still considered too dangerous to handle and are kept in lead-lined boxes.
66 Soddy envisaged this artificial transmutation fifteen years before Rutherford achieved it, and imagined explosive or controlled atomic disintegrations long before fission or fusion were discovered.
67 It was reading The World Set Free in the 1930s that set Leo Szilard to thinking of chain reactions and getting a secret patent on these in 1936; in 1940 he persuaded Einstein to send his famous letter to Roosevelt about the possibilities of an atomic bomb.
Chapter Twenty-Four: Brilliant Light
68 By 1914, the scientists of Britain and France and Germany and Austria were all caught up, in various ways, in the First World War. Pure chemistry and physics were largely suspended for the duration, and applied science, war science, took its place. Rutherford ceased his fundamental research, and his lab was reorganized for work on submarine detection. Geiger and Marsden, who had observed the alpha-particle deflections that gave rise to Rutherford’s atom, found themselves at the Western Front, on different sides. Chadwick and Ellis, younger colleagues of Rutherford’s, were prisoners of war in Germany. And Moseley, aged twenty-eight, was killed by a bullet in the brain, at Gallipoli. My father often used to talk of the young poets, the intellectuals, the cream of a generation wiped out tragically in the Great War. Most of the names he mentioned were unknown to me, but Moseley’s was the one I knew, and the one I mourned most.
69 This gave Bohr predictive power too. Moseley had observed that element 72 was missing, but could not say whether it would be a rare-earth element or not (elements 57-71 were rare earths, and 73, tantalum, was a transition element, but no one was sure how many rare earths there would be). Bohr, with his clear idea of the numbers of electrons in each shell, was able to predict that element 72 would not be a rare-earth element, but a heavier analog of zirconium. He suggested that his colleagues in Denmark seek this new element in zirconium ores, and it was swiftly found (and named hafnium, after the old name for Copenhagen). This was the first time the existence and properties of an element were predicted not by chemical analogy, but on the purely theoretical basis of its electronic structure.
70 It was also wondered, early in the twentieth century, what might happen to the ‘electron gas’ in metals if they were cooled to temperatures near absolute zero – would this ‘freeze’ all the electrons, turning the metal into a complete insulator? What was found, using mercury, was the complete opposite: the mercury became a perfect conductor, a superconductor, suddenly losing all its resistance at 4.2 degrees above absolute zero. Thus one could have a ring of mercury, cooled by liquid helium, with an electrical current flowing around it with no diminution, for days, forever.
71 The universe started, Gamow conceived, as almost infinitely dense – perhaps no larger than a fist. Gamow and his student Ralph Alpher went on to suggest (in a famous 1948 article that came to be known, after Hans Bethe was invited to add his name, as the alpha-beta-gamma paper), that this primal fist-sized universe exploded, inaugurating space and time, and that in this explosion (which Hoyle, derisively, was to call the Big Bang) all of the elements were created.
But here he was wrong; it was only the lightest elements – hydrogen and helium and perhaps a little lithium – that originated in the Big Bang. It was not until the 1950s that it became clear how the heavier elements were generated. It might take billions of years for an average star to consume all its hydrogen, but the more massive stars, far from extinguishing at this point, could contract, becoming hotter still, and start on further nuclear reactions, fusing their helium to produce carbon, fusing this in turn to produce oxygen, and then silicon, phosphorus, sulphur, sodium, magnesium – all the way up to iron. Beyond iron no energy could be released by further fusion, so this accumulated as an end point in nucleosynthesis. Hence its remarkable abundance in the universe, an abundance reflected in metallic meteorites and in the iron core of the earth. (The heavier elements, those beyond iron, remained a puzzle for longer; they only originate, apparently, with supernova explosions.)
Chapter Twenty-Five: The End of The Affair
72 This question again resonated for me when I read Primo Levi’s wonderful book The Periodic Table, especially the chapter called ‘Potassium.’ Here Levi speaks of his own search, as a student, for ‘sources of certainty.’ Deciding he would become a physicist, Levi left the chemistry lab and apprenticed himself to the physics department – to an astrophysicist, in particular. This did not work out quite as he had hoped, for while some ultimate certainties might indeed be found in stellar physics, such certainties, though sublime, were abstract and remote from daily life. More soul-filling, nearer life, were the beauties of practical chemistry. ‘When I understand what’s going on inside a retort,’ Levi once remarked, ‘I’m happier. I’ve extended my knowledge a little bit more. I haven’t understood truth or reality. I’ve just reconstructed a segment, a little segment of the world. That’s already a big victory inside a factory laboratory.’
73 I was not quite alone. A most important guide to me at this point was George Gamow, a scientist-writer of great versatility and charm whose Birth and Death of the Sun I had already read. In his ‘Mr. Tompkins’ books (Mr. Tompkins in Wonderland and Mr. Tompkins Explores the Atom, published in 1945), Gamow uses the device of altering physical constants by many orders of magnitude to make otherwise unimaginable worlds at least half-imaginable. Relativity is made comically imaginable by supposing the velocity of light to be only thirty miles per hour, and quantum mechanics equally so by imagining Planck’s constant increased by twenty-eight orders of magnitude, so that one can have quantum effects in ‘real’ life – thus quantum tigers, smeared out in a quantum jungle, are nowhere and everywhere at once.
I sometimes wondered whether any ‘macroquantal’ phenomena existed, whether one might ever be able to see, under extraordinary conditions, a quantal world with one’s own eyes. One of the unforgettable experiences of my life was exactly this, when I was introduced to liquid helium, and saw how this changed its properties suddenly at a critical temperature, turning from a normal liquid into a strange superfluid with no viscosity, no entropy whatever, able to go through walls, to climb out of a beaker, and with a thermal conductivity three million times that of normal liquid helium. This impossible state of matter could only be understood in terms of quantum mechanics: the atoms were now so close together that their wave functions overlapped and merged, so that one had, in effect, a single giant atom.
74 I wish I had realized – but that would not have been easy for me as a boy – that Crookes was wrong, that the new insight about the atom which prompted his thoughts (he was writing this in 1915, ju
st two years after Bohr) would serve, once assimilated, to expand and enrich chemistry enormously, not to reduce it, annihilate it, as he feared. There were similar anxieties about the first atomic theory: many chemists, Humphry Davy among them, felt there was danger in accepting Dalton’s notions of atoms and atomic weights, danger of pulling chemistry away from its concreteness and reality into an arid, impoverished, metaphysical realm.
Acknowledgments
I owe a huge debt to my brothers, my cousins, and, not least, my old friends, who have shared memories, letters, photographs, and memorabilia of all kinds; I could not have reconstructed the events of so long ago without them. I have written of them, and others, with some trepidation: ‘It is always dangerous,’ as Primo Levi remarked, ‘transforming a person into a character.’
Kate Edgar, my assistant, and editor of many of my previous books, has been a virtual collaborator on this one, not only editing the innumerable drafts I produced, but meeting chemists with me, going down mines, enduring smells and explosions, electrical discharges and occasional radioactive emanations, and putting up with an office increasingly filled with periodic tables, spectroscopes, crystals dangling in supersaturated solutions, coils of wire, batteries, chemicals, and minerals. This book would still be a two-million-word excavation had it not been for her powers of distillation.
Sheryl Carter, also working with me, has opened the wonders of the Internet for me (I am computer-illiterate, and I do all my writing with a pen or an old typewriter), and has found books and articles and scientific instruments and toys of all sorts which I could never have got for myself.