Pierre Curie

Pierre Curie (1859-1906) was a noted physicist who became famous for his collaboration with his wife, Marie Curie, in the study of radioactivity. Before joining his wife in her research, Curie was already widely known and respected in the world of physics.

Pierre Curie was a noted physicist who became famous for his collaboration with his wife Marie Curie in the study of radioactivity. Before joining his wife in her research, Pierre Curie was already widely known and respected in the world of physics. He discovered (with his brother Jacques ) the phenomenon of piezoelectricity—in which a crystal can become electrically polarized—and invented the quartz balance. His papers on crystal symmetry, and his findings on the relation between magnetism and temperature also earned praise in the scientific community. Curie died in a street accident in 1906, a physicist acclaimed the world over but who had never had a decent laboratory in which to work.

Pierre Curie was born in Paris on May 15, 1859, the son of Sophie-Claire Depouilly, daughter of a formerly prominent manufacturer, and Eugène Curie, a free-thinking physician who was also a physician's son. Dr. Curie supported the family with his modest medical practice while pursuing his love for the natural sciences on the side. He was also an idealist and an ardent republican who set up a hospital for the wounded during the Commune of 1871. Pierre was a dreamer whose style of learning was not well adapted to formal schooling. He received his pre-university education entirely at home, taught first by his mother and then by his father as well as his older brother, Jacques. He especially enjoyed excursions into the countryside to observe and study plants and animals, developing a love of nature that endured throughout his life and that provided his only recreation and relief from work during his later scientific career. At the age of 14, Curie studied with a mathematics professor who helped him develop his gift in the subject, especially spatial concepts. Curie's knowledge of physics and mathematics earned him his bachelor of science degree in 1875 at the age of sixteen. He then enrolled in the Faculty of Sciences at the Sorbonne in Paris and earned his licence (the equivalent of a master's degree) in physical sciences in 1877.

Curie became a laboratory assistant to Paul Desains at the Sorbonne in 1878, in charge of the physics students' lab work. His brother Jacques was working in the mineralogy laboratory at the Sorbonne at that time, and the two began a productive five-year scientific collaboration. They investigated pyroelectricity, the acquisition of electric charges by different faces of certain types of crystals when heated. Led by their knowledge of symmetry in crystals, the brothers experimentally discovered the previously unknown phenomenon of piezoelectricity, an electric polarization caused by force applied to the crystal. In 1880 the Curies published the first in a series of papers about their discovery. They then studied the opposite effect—the compression of a piezoelectric crystal by an electric field. In order to measure the very small amounts of electricity involved, the brothers invented a new laboratory instrument: a piezoelectric quartz electrometer, or balance. This device became very useful for electrical researchers and would prove highly valuable to Marie Curie in her studies of radioactivity. Much later, piezoelectricity had important practical applications. Paul Langevin, a student of Pierre Curie's, found that inverse piezoelectricity causes piezoelectric quartz in alternating fields to emit high-frequency sound waves, which were used to detect submarines and explore the ocean's floor. Piezoelectric crystals were also used in radio broadcasting and stereo equipment.

In 1882 Pierre Curie was appointed head of the laboratory at Paris' new Municipal School of Industrial Physics and Chemistry, a poorly paid position; he remained at the school for 22 years, until 1904. In 1883 Jacques Curie left Paris to become a lecturer in mineralogy at the University of Montpelier, and the brothers' collaboration ended. After Jacques's departure, Pierre delved into theoretical and experimental research on crystal symmetry, although the time available to him for such work was limited by the demands of organizing the school's laboratory from scratch and directing the laboratory work of up to 30 students, with only one assistant. He began publishing works on crystal symmetry in 1884, including in 1885 a theory on the formation of crystals and in 1894 an enunciation of the general principle of symmetry. Curie's writings on symmetry were of fundamental importance to later crystallographers, and, as Marie Curie later wrote in Pierre Curie, "he always retained a passionate interest in the physics of crystals" even though he turned his attention to other areas.

From 1890 to 1895 Pierre Curie performed a series of investigations that formed the basis of his doctoral thesis: a study of the magnetic properties of substances at different temperatures. He was, as always, hampered in his work by his obligations to his students, by the lack of funds to support his experiments, and by the lack of a laboratory or even a room for his own personal use. His magnetism research was conducted mostly in a corridor. In spite of these limitations, Curie's work on magnetism, like his papers on symmetry, was of fundamental importance. His expression of the results of his findings about the relation between temperature and magnetization became known as Curie's law, and the temperature above which magnetic properties disappear is called the Curie point. Curie successfully defended his thesis before the Faculty of Sciences at the University of Paris (the Sorbonne) in March 1895, thus earning his doctorate. Also during this period, he constructed a periodic precision balance, with direct reading, that was a great advance over older balance systems and was especially valuable for chemical analysis. Curie was now becoming well-known among physicists; he attracted the attention and esteem of, among others, the noted Scottish mathematician and physicist William Thomson (Lord Kelvin). It was partly due to Kelvin's influence that Curie was named to a newly created chair of physics at the School of Physics and Chemistry, which improved his status somewhat but still did not bring him a laboratory.

In the spring of 1894, at the age of 35, Curie met Maria (later Marie) Sklodowska, a poor young Polish student who had received her licence in physics from the Sorbonne and was then studying for her licence in mathematics. They immediately formed a rapport, and Curie soon proposed marriage. Sklodowska returned to Poland that summer, not certain that she would be willing to separate herself permanently from her family and her country. Curie's persuasive correspondence convinced her to return to Paris that autumn, and the couple married in July, 1895, in a simple civil ceremony. Marie used a cash wedding gift to purchase two bicycles, which took the newlyweds on their honeymoon in the French countryside and provided their main source of recreation for years to come. Their daughter Irene was born in 1897, and a few days later Pierre's mother died; Dr. Curie then came to live with the young couple and helped care for his granddaughter.

The Curies' attention was caught by Henri Becquerel's discovery in 1896 that uranium compounds emit rays. Marie decided to make a study of this phenomenon the subject of her doctor's thesis, and Pierre secured the use of a ground-floor storeroom/machine shop at the School for her laboratory work. Using the Curie brothers' piezoelectric quartz electrometer, Marie tested all the elements then known to see if any of them, like uranium, emitted "Becquerel rays," which she christened "radioactivity." Only thorium and uranium and their compounds, she found, were radioactive. She was startled to discover that the ores pitchblende and chalcolite had much greater levels of radioactivity than the amounts of uranium and thorium they contained could account for. She guessed that a new, highly radioactive element must be responsible and, as she wrote in Pierre Curie, was seized with "a passionate desire to verify this hypothesis as rapidly as possible."

Pierre Curie too saw the significance of his wife's findings and set aside his much-loved work on crystals (only for the time being, he thought) to join Marie in the search for the new element. They devised a new method of chemical research, progressively separating pitchblende by chemical analysis and then measuring the radioactivity of the separate constituents. In July 1898, in a joint paper, they announced their discovery of a new element they named polonium, in honor of Marie Curie's native country. In December 1898, they announced, in a paper issued with their collaborator G. Bémont, the discovery of another new element, radium. Both elements were much more radioactive than uranium or thorium.

The Curies had discovered radium and polonium, but in order to prove the existence of these new substances chemically, they had to isolate the elements so the atomic weight of each could be determined. This was a daunting task, as they would have to process two tons of pitchblende ore to obtain a few centigrams of pure radium. Their laboratory facilities were woefully inadequate: an abandoned wooden shed in the School's yard, with no hoods to carry off the poisonous gases their work produced. They found the pitchblende at a reasonable price in the form of waste from a uranium mine run by the Austrian government. The Curies now divided their labor. Marie acted as the chemist, performing the physically arduous job of chemically separating the pitchblende; the bulkiest part of this work she did in the yard adjoining the shed/laboratory. Pierre was the physicist, analyzing the physical properties of the substances that Marie's separations produced. In 1902 the Curies announced that they had succeeded in preparing a decigram of pure radium chloride and had made an initial determination of radium's atomic weight. They had proven the chemical individuality of radium.

The Curies' research also yielded a wealth of information about radioactivity, which they shared with the world in a series of papers published between 1898 and 1904. They announced their discovery of induced radioactivity in 1899. They wrote about the luminous and chemical effects of radioactive rays and their electric charge. Pierre studied the action of a magnetic field on radium rays, he investigated the persistence of induced radioactivity, and he developed a standard for measuring time on the basis of radioactivity, an important basis for geologic and archaeological dating techniques. Pierre Curie also used himself as a human guinea pig, deliberately exposing his arm to radium for several hours and recording the progressive, slowly healing burn that resulted. He collaborated with physicians in animal experiments that led to the use of radium therapy—often called "Curie-therapie" then—to treat cancer and lupus. In 1904 he published a paper on the liberation of heat by radium salts.

Through all this intensive research, the Curies struggled to keep up with their teaching, household, and financial obligations. Pierre Curie was a kind, gentle, and reserved man, entirely devoted to his work—science conducted purely for the sake of science. He rejected honorary distinctions; in 1903 he declined the prestigious decoration of the Legion of Honor. He also, with his wife's agreement, refused to patent their radium-preparation process, which formed the basis of the lucrative radium industry; instead, they shared all their information about the process with whomever asked for it. Curie found it almost impossible to advance professionally within the French university system; seeking a position was an "ugly necessity" and "demoralizing" for him ( Pierre Curie ), so posts he might have been considered for went instead to others. He was turned down for the Chair of Physical Chemistry at the Sorbonne in 1898; instead, he was appointed assistant professor at the Polytechnic School in March 1900, a much inferior position.

Appreciated outside France, Curie received an excellent offer of a professorship at the University of Geneva in the spring of 1900, but he turned it down so as not to interrupt his research on radium. Shortly afterward, Curie was appointed to a physics chair at the Sorbonne, thanks to the efforts of Jules Henri Poincaré. Still, he did not have a laboratory, and his teaching load was now doubled, as he still held his post at the School of Physics and Chemistry. He began to suffer from extreme fatigue and sharp pains through his body, which he and his wife attributed to overwork, although the symptoms were almost certainly a sign of radiation poisoning, an unrecognized illness at that time. In 1902, Curie's candidacy for election to the French Academy of Sciences failed, and in 1903 his application for the chair of mineralogy at the Sorbonne was rejected, both of which added to his bitterness toward the French academic establishment.

Recognition at home finally came for Curie because of international awards. In 1903 London's Royal Society conferred the Davy medal on the Curies, and shortly thereafter they were awarded the 1903 Nobel Prize in physics—along with Becquerel—for their work on radioactivity. Curie presciently concluded his Nobel lecture (delivered in 1905 because the Curies had been too ill to attend the 1903 award ceremony) by wondering whether the knowledge of radium and radioactivity would be harmful for humanity; he added that he himself felt that more good than harm would result from the new discoveries. The Nobel award shattered the Curies' reclusive work-absorbed life. They were inundated by journalists, photographers, curiosity-seekers, eminent and little-known visitors, correspondence, and requests fr articles and lectures. Still, the cash from the award was a godsend, and the award's prestige finally prompted the French parliament to create a new professorship for Curie at the Sorbonne in 1904. Curie declared he would remain at the School of Physics unless the new chair included a fully funded laboratory, complete with assistants. His demand was met, and Marie was named his laboratory chief. Late in 1904 the Curies' second daughter, Eve, was born. By early 1906, Pierre Curie was poised to begin work—at last and for the first time—in an adequate laboratory, although he was increasingly ill and tired. On April 19, 1906, leaving a lunchtime meeting in Paris with colleagues from the Sorbonne, Curie slipped in front of a horse-drawn cart while crossing a rain-slicked rue Dauphine. He was killed instantly when the rear wheel of the cart crushed his skull. The world mourned the untimely loss of this great physicist. True to the way he had conducted his life, he was interred in a small suburban cemetery in a simple, private ceremony attended only by his family and a few close friends. In his memory, the Faculty of Sciences at the Sorbonne appointed Curie's widow Marie to his chair.

Further Reading on Pierre Curie

Curie, Eve, Madame Curie: A Biography by Eve Curie, translated by Vincent Sheean, Doubleday, 1937.

Curie, Marie, Pierre Curie, Macmillan, 1923.

Giroud, Françoise, Marie Curie: A Life, Holmes & Meier, 1986.

Heathcote, Niels H. de V., Nobel Prize Winners in Physics 1901-1950, Henry Schuman, 1953.

Magill, Frank N., The Nobel Prize Winners: Physics, Volume 1: (1901-1937), Salem Press, 1989.

Reid, Robert, Marie Curie, Dutton, 1974.

Romer, Alfred, editor, The Discovery of Radioactivity and Transmutation, Dover, 1964.

Segre, Emilio, From X-Rays to Quarks: Modern Physicists and Their Discoveries, University of California Press, 1980.

Weaver, Jefferson Hane, The World of Physics, Simon & Schuster, 1987.

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