Lenard had observed that when the power was on, the negative plate produced a stream of rays which caused the tube walls to glow with a soft green light. Rontgen was prepared for this. What startled him was that, despite the black card with which he had mantled his tube to exclude exterior influences on his observations, a nearby paper screen painted with fluorescent substances (barium platinocyanide) was also glowing brightly. In fact, each time electricity pulsed through the blacked-out tube, the paper screen luminesced. Rontgen moved the screen two yards away from the tube, but still it glowed.
Lenard's experiments had demonstrated that cathode rays were stopped by quite thin barriers, so Rontgen realized that some sort of penetrating rays—hitherto unknown and which he therefore named "x-rays"—were escaping through the glass walls of his tube. He further deduced that these x-rays were caused by the impact of the cathode rays on the tube's glass walls. He discovered that although his x-rays could penetrate thick books or decks of cards, they could not pass through denser materials like metal so easily. When he placed his hand between the tube and the fluorescent screen, Rontgen was staggered to see the shadows of his own bones. The rays had penetrated the soft tissue, but the denser bones were sharply delineated on the screen.
Rontgen tested the rays' effects using photographic plates, capturing in the world's first x-ray pictures images of everything from a compass needle in a metal case to his bones. Rontgen realized the implications: His rays could be used to identify fractures in bones and find bullets embedded in tissue. In January i 896 he announced his discovery publicly in Berlin, and before the month was out radiographs were being produced around the world. In 1901 he would become the first recipient of the Nobel Prize for Physics, introduced that year after Alfred Nobel left the bulk of his estate in trust for the annual award of five prizes for services to physics, chemistry, medicine, literature, and peace. In the years ahead, the physics and chemistry awards would be dominated by those exploring the new atomic science.
As news of the miraculous rays spread and they were successfully put to work in medical diagnosis, Rontgen became a reluctant celebrity, forced to dodge newspaper reporters. Some people, though, were disturbed by his discovery. Women seriously contemplated buying "x-ray proof underwear" to repel lascivious Peeping Toms. One rhyme warned:
Punch cartoon of Rontgen's x-rays
I hear they'll gaze
Tharough cloak and gown—and even stays
Those naughty, naughty Rontgen rays
Punch magazine quipped:
We do not want, like Dr. Swft,
To take our flesh off and to pose in
Our bones, or show each little rift
And joint for you to poke your nose in.
We only crave to contemplate
Each other's usualfull-dress photo;
Your worse than "altogether" state
Of portraiture we bar in toto/
Becquerel's smudges showing the first proof of radioactivity
Meanwhile, puzzled scientists struggled to explain the source of the mysterious x-rays. In Paris, the physicist and professor Henri Becquerel decided to investigate whether phosphorescent and fluorescent substances produced these invisible rays.* Becquerel carefully placed successive glowing materials on photographic plates that he had previously wrapped in thick black paper to see whether rays would penetrate the paper and darken the plates. Nothing happened until he selected the powdery white salts of the rare metal uranium, luminous in sunlight. At last, there was a result. When the plates were developed, Becquerel noted faint smudges—evidence of penetrating radiation. He conducted further tests, sometimes adding a coin or metal sheet and observing the faint traces of their outline.
One day he placed uranium salts, together with a copper cross, on a photographic plate, but the Paris weather became overcast. Sharing the common belief that substances needed natural sunlight to luminesce, he thrust the plate into a drawer to await a brighter day. Some days later, on i March 1896, sheer chance or what another scientist William Crookes—who was present and saw what happened—admiringly called "the unconscious pre-vision of genius" caused Becquerel to develop the plate. He found that despite being in darkness the uranium salts had emitted radiation. The image of the copper cross was "shining out white against the black background."
Becquerel wrote up his results with both puzzlement and excitement. He had, in fact, discovered radioactivity—the first new property of matter since Isaac Newton identified gravity. Although he did not appreciate the full significance of his findings, he realized that they were important and unexpected, and was therefore piqued when they attracted little comment. Rontgen's x-rays still commanded all the attention.
· · ·
However, Marie Curie read Becquerel's work and was, as she later wrote, "much excited by this new phenomenon, and I resolved to undertake the special study of it." Since the subject was "entirely new"—no one except Becquerel had yet written about it—all she needed to do before getting started on her doctorate was to read his papers. Marie was offered a damp little glass-paneled storage room on the ground floor of the School of Physics as her laboratory and on 16 December 1897 began work. Becquerel had noted that his rays released a light electrical charge into the air. Marie therefore decided to measure the electric current emanating from uranium salts. The Curie brothers' piezoquartz electrometer, sensitive to the faintest trace of electrical current, was tailor-made for her purpose. She found the rays' activity to be directly proportionate to the quantity of uranium in the specimens and that it was unaffected by light, temperature, or the chemical form the uranium was in.
Wondering whether other chemical elements besides uranium might share these qualities, she plundered her colleagues' shelves for specimens. Her careful examination of these elements revealed that, in addition to uranium, only thorium, the heaviest of the known elements after uranium, was active. Her measurements also showed that pitchblende, a heavy, black ore rich in compounds of uranium, appeared to be nearly four times as active as pure uranium. This was not what she had expected. She repeated her meticulous tests twenty times, but her results remained the same. Since she had already tested all known elements for activity, logically this could only mean one thing: The pitchblende contained a new element. She told her sister Bronya, "The element is there and I've got to find it."
Marie immersed herself completely in her work, helped by Pierre. As their younger daughter Eve later wrote, he had followed his wife's progress "with passionate interest. Without directly taking part in Marie's work, he had frequently helped her by his remarks and advice. In view of the stupefying character of her results, he did not hesitate to abandon his study of crystals for the time being in order to join his efforts to hers in the search for the new substance."
They began breaking down the pitchblende to extract the tiny fragment containing the activity, hoping thereby to solve the puzzle. They did this by extracting from the pitchblende sulfur of bismuth, a substance which, according to their measurements, was far more active than uranium. Since pure sulfur of bismuth was itself inactive, this meant that the new active ingredient had to be present in the bismuth.
It was laborious, painstaking, but exciting work. As soon as they had extracted a tiny amount of active material, Marie bore it off to Eugene De-marcay, a specialist in spectrography—the science of identifying elements by the rainbow-colored "spectra" they display when energized by an electric current. Although Demarcay had lost an eye in a laboratory accident, his abilities were still acute. He analyzed Marie Curie's specimen and declared it was something he had never seen before.
The Curies announced their discovery of what they believed to be a new element in July 1898 in the Academy of Sciences' Comptes Rendus, the most influential scientific publication in France. They declared that, if proved correct, they would name it "polonium" in tribute to the land of Marie's birth. The title of their paper—"On a New Radioactive Substance Contained in Pitchblende"—coined a new word. The t
erms radioactive and radioactivity, from the Latin word radius, meaning "ray," were quickly taken up. So was the term ra-dioelement to define any element with this property.
After a cycling trip to the Auvergne with baby daughter Irene, whose first words—"Gogli, gogli, go"—Marie recorded with as much delight as her experimental findings, they returned to Paris to resume their investigation. As they labored, they were astonished to discover a further new radioactive element in the pitchblende. On 26 December 1 898, just six months after finding polonium, they announced the likely existence of this second new element, naming it "radium" and telling the world that its radioactivity "must be enormous." Their paper also stated that "one of us" (probably Marie), had shown that "radioactivity seems to be an atomic property"—in other words, it derived from some characteristic within the atom, the tiny brick from which all matter is built.
The Curies had made these startling discoveries with tremendous speed—within a year of Marie beginning her doctoral thesis. They next had to convince the many skeptics that radium and polonium were not fanciful chimera but real. So far they had succeeded in isolating only tiny specimens of each. To prove their existence beyond dispute, they needed larger samples.
It was already clear that radium was the more active of the two and therefore easier to isolate. Accordingly, Marie Curie focused on extracting pure radium—a formidable task since radium constitutes less than a millionth part of pitchblende. She needed fifty tons of water and some six tons of chemicals to process just one ton of pitchblende, from which the maximum yield would be no more than four hundred milligrams of radium—about one hundredth of an ounce. The task required facilities on an industrial scale. Instead, the School of Physics offered the Curies what Marie called a "miserable old shed" abutting the narrow Rue Lhomond. This old wooden hangar with a leaking skylight and a rusting cast-iron stove had been used as a dissecting room. A visiting German chemist likened it to a cross between a stable and a potato cellar.
The Curies' laboratory circa 1898
As Marie Curie recalled, she felt "extremely handicapped by inadequate conditions, by the lack of a proper place to work in, by the lack of money and of personnel." Nevertheless, the Curies moved in and awaited the delivery of ten tons of pitchblende residue from the St. Joachimsthal uranium mines in Bohemia, the principal source of uranium ore in Europe. The valuable uranium salts extracted from pitchblende were used to dye skins for the then fashionable yellow gloves and to stain glass in rich hues of orange and yellow, but the residue was considered worthless. The Curies hoped it would still contain enough radium for their purposes. When horse-drawn carts finally delivered the sacks of ore, Marie impatiently ripped one open, spilling the contents, still mixed with Bohemian pine needles, out on the courtyard. She tested a chunk with an electrometer and to her relief found it highly radioactive.
Marie effectively took charge. Pierre later admitted that, left to his own devices, he would never have embarked on such an enterprise. Day after day the small figure dressed in a baggy, stained linen smock could be seen obsessively filling cauldrons in the courtyard. She processed the pitchblende in batches, pulverizing, crystallizing, precipitating, and leaching to purify and extract the precious radium, which glowed blue in its glass containers. As she later recalled, "Sometimes I had to spend a whole day mixing a boiling mass with a heavy iron rod nearly as large as myself. I would be broken with fatigue at the day's end. Other days, on the contrary, the work would be a most minute and delicate fractional crystallization, in the effort to concentrate the radium."
The hangar lacked any proper ventilation, so, unless it was raining, Marie performed her chemical treatments in the courtyard to avoid breathing in the noxious fumes. By the time the work was complete she would have shed nearly fourteen pounds. However, there were compensations. As Marie later recalled, "Our precious products . . . were arranged on tables and boards; from all sides we could see their slightly luminous silhouettes, and these gleamings, which seemed suspended in the darkness, stirred us with ever newr emotion and enchantment."
As the work progressed, with Pierre helping to interpret and present their results, the Central Society of Chemical Products offered Marie facilities to carry out the early stages of purification on a more industrial scale. She accepted gratefully, and the work was overseen by one of Pierre's students, young chemist Andre Debierne from the Sorbonne, who in 1899 had isolated a third radioactive element in pitchblende: actinium.
On 28 March 1902, over three years after announcing her belief in its existence, Marie Curie finally had sufficient radium—one tenth of a gram—for a definitive test. Once again she hurried to the expert spectroscopist Eugene Demarcav. He confirmed definitively what she had known intuitively—that radium was indeed a new element. She weighed it carefully and recorded the result: 225 times the weight of hydrogen, the lightest element (and very close to the current agreed weight of 226). By May 1903 Marie Curie's thesis, "Researches on Radioactive Substances," was ready for the printer. In June she appeared before three luminaries of the Sorbonne to be questioned on her work, a pale figure austerely clad in black. But it was a formality. She knew far more about her findings than her inquisitors. With little ado they conferred her degree with the accolade tres honorable. Seven months later, in December 1903, the Academy of Science of Stockholm announced the awarding to the Curies of the Nobel Prize for Physics, shared with Henri Becquerel, for the extraordinary services they had rendered by their study of Becquerel rays.
Like Rontgen before them, the Curies became unwilling celebrities. People hailed radium as a "miracle substance." It seemed to offer limitless possibilities and quickly became the most costly substance in the world, valued at 7co,000 gold francs a gram. An American chemist speculated, "Are our bicycles to be lighted with disks of radium in tiny lanterns? Are these substances to become the cheapest form of light for certain purposes? Are we about to realize the chimerical dream of the alchemists—lamps giving light perpetually without consumption of oil?" The American exotic dancer Loi'e Fuller, who had arrived in Paris with Buffalo Bill's "Wild West Show" to become the toast of the Folies-Bergere, begged the Curies for shimmering "butterfly wings of radium." They had to disappoint her, but Loi'e nevertheless insisted on performing one of her outre routines in their small house.
The Curies' success had been rapid and dazzling, but there was a price. When Pierre Curie raised his glowing tube of radium aloft at the party to fete his wife's doctorate, a guest noticed that his long, slender hands were in a very inflamed and painful state. This was the result of exposure to radium rays. Sometimes he found it impossible to button his clothes. He also suffered disabling stabbing pains in the legs for which he dosed himself with strychnine—then a recognized treatment for rheumatism—but which, in retrospect, were probably the result of radiation. Marie's fingertips, too, were hardened and burned. A few weeks later she would suffer a miscarriage. Neither understood the risks they had been taking.
Indeed, alerted by reports from two German scientists that radium appeared to have physiological effects on the body, Pierre Curie had actually begun experimenting on his own body, tying a bandage containing radium salts to his arm for a few hours. The resulting wound, as he observed with interest, took months to heal. In his detailed report on it he added that "Madame Curie, in carrying a fewr centigrams of very active material in a little sealed tube, received analogous burns." These effects sparked the thought in Pierre Curie's mind that radium could, perhaps, be used to destroy cancerous cells, and he began to work with physicians. Radium was first used in radiotherapy—known as Curietherapy in France—as early as 1903 to treat cancers but also such conditions as the skin disease lupus, strawberry marks, and granulations of the eyelids. A number of treatments evolved, ranging from washing in a solution of radium, to injections of radium, to drinking radium "tonics." The treatment for cancer was to place tiny glass or platinum tubes containing radium directly next to the malignant cells. The Curies, though, derived no personal fi
nancial benefit from the "miracle" substance. They decided not to patent their process for extracting radium, believing it to be against the spirit of science to seek commercial advantage. Such knowledge should be available to all.
· · ·
Marie Curie's discovery of radium was an emphatic push on a door just starting to open on a new subatomic world whose implications challenged long-established beliefs. To some they were unthinkable. Unraveling the mysteries would require intuitive skills, a daring but disciplined imagination, physical energy, and a first-rate scientific mind. These were exactly the qualities of the guest who had been observing Pierre Curie's damaged hands with such sympathetic interest: the young New Zealand physicist Ernest Rutherford.
*The licence es sciences is comparable to a bachelor of science degree.
†Piezoelectricity comes from the Greek piezein, meaning to "press tight."
* Fluorescent substances absorb light of one color or wavelength and in its place radiate light of another color. When the source of the light is turned off, that radiation ceases. With phosphorescent materials, the radiation continues after the light source has been removed.
TWO
A RABBIT FROM THE ANTIPODES
RUGGED, RUDDY, AND ROBUST, Ernest Rutherford looked more like a rugby player than a scientist. His appearance reflected his roots in the still-young British colony of New Zealand, where he was born in 18 71, a few miles south of the pioneering town of Nelson on South Island. His grandfather George Rutherford, a craggy-faced wheelwright with muttonchop sideburns, had arrived in New Zealand from Dundee in Scotland with his family in 1843. The party included his five-year-old son James, who in 1866 married schoolteacher Martha Thompson. Ernest was their fourth child and second son.
Before the Fallout Page 3
