If receiving a Nobel prize is the highest recognition for a scientist, being awarded twice by the Swedish Academy of Sciences is an extraordinary fact of which, until now, only four people can boast: Frederick Sanger, Linus Pauling, John Bardeen and Marie Curie.
Marie Sklodowska’s father was a physics teacher and her mother the principal of a girl’s school in the Polish capital Warsaw. She acquired from her father a positivism and an interest in science although to add the family finances she was forced, in 1885, to become a governess. She seems to have been on the fringe of nationalist revolutionary politics at a time when Polish language and culture were very much under Russian domination, but her main interest at this time appears to have been science. There was no way in which a girl could receive any form of higher scientific education in Poland in the 1880s, and so in 191 she followed her elder sister to Pars. Living in poverty and working hard she graduated in physics from the Sorbonne in 1893, taking first place She received a scholarship from Poland, which enabled her to spend a year studying mathematics; this time she graduated in second place.
In 1894 she met Pierre Cure and they marred the following year. He was a physicist of some distinction, having already made several important discoveries, and was working as chief of the laboratory of the school of Industrial Physics and Chemistry. Marie was at this time looking for a topic for research for a higher degree. Her husband was in full sympathy with her desire to continue with research, by no means a common attitude in late 19th century France. She was also fortunate in her timing and choice of topic – the study of radioactivity. In 1896 Henri Becquerel, had discovered radioactivity n uranium. Marie Curie had reason to believe that there might be a new element in the samples of uranium ore (pitchblende) that Becquerel had handled, but first she needed a place to work and a supply of the ore. It was agreed that she could work in her husband’s laboratory. Her first task was to see if substances other than uranium were radioactive. Her method was to place the substance on one of the plates of Pierre’s sensitive electrometer to see if it produced an electric current between the plates. In a short time, she found that thorium is also radioactive.
Her next discovery was in many ways the most fundamental. She tried to see whether different compounds of uranium or thorium would have differing amounts of radioactivity. Her conclusion was that it made no difference what she mixed the uranium with, whether it was wet or dry, in powder form or solution; the only factor that counted was the amount of uranium present. This meant that radioactivity must be property of the uranium itself and not of its interaction with something else. Radioactivity had to be an atomic property; it would soon be recognised as an effect of the nucleus.
One further advance was made by Marie Curie in 1898; she found that two uranium minerals, pitchblende and chalcolite, were more active than uranium itself. She drew the correct conclusion from this, namely that they must contain new radioactive elements. She immediately began the search for them. By the end of the year, she had demonstrated the existence of two new elements, radium and polonium, both of which were taken at this time against the levels of radiation, as their harmful effects were not recognised (Indeed, according to some scientists, her notebooks of this period were still too dangerous to handle!).
Her next aim was to produce some pure radium. The difficulty here was that radium is present in pitchblende in such small quantities that vast amounts of the ore were needed. The Curies managed to acquire, quite cheaply, several tons of pitchblende from the Bohemian mines thanks to the intercession of the Austrian government. As there was too much material for her small laboratory, she was offered the use of an old dissecting room in the yard of the school. It was freezing in winter and unbearably hot in summer – Wilhelm Ostwald later described it as a cross between a stable and a potato cellar. The work was heavy and monotonous. The limitation of her equipment meant that she could only deal with batches of 20 kilograms at a time, which had to be carefully dissolved, filtered, and crystallised. This procedure went on month after month, in all kinds of weather. By early 1902 she had obtained one tenth of a gram of radium chloride. She took it to the French chemist Eugène Demarçay (1852-1904) who had first identified the new elements spectroscopically. He now had enough to determine its atomic weight, which he calculated as 225.93.
The crucial question arising from the discovery of these new elements was, what was the nature of the radiation emitted? It was thought that there were at least two different kinds of rays. One kind could be deflected by a magnetic field while the other was unaffected and would only travel a few centimetres before disappearing. (These were identified as the alpha and beta rays by Ernest Rutherford.) A further question was the nature of the source of the energy. Pierre Curie showed that one gram of radium gave out about a hundred calories per hour. One further mystery at this time was the discovery of induced radioactivity – they had found that metal plates that had been close to, but not in contact with, samples of radium became radioactive themselves and remained so for some time.
The mysteries of radioactivity were explained not by the Curies but by Rutherford and his pupils. Although Marie Curie was no great theorist, she was an industrious experimentalist who with great strength and single mindedness would pursue important but basically tedious experimental procedures for years. Her thesis was presented in 1903 and she became the first woman to be awarded and advanced scientific research degree in France. In the same year she was awarded the Nobel prize for physics jointly with her husband and Becquerel for their work on radioactivity.
In 1904, when her husband was appointed as professor at the Sorbonne, Marie was offered a part-time post as a physics teacher at a girl’s school at sevres. In the same year her second daughter Eve was born. It is also about this time that she first appears to have suffered from radiation sickness Given all these distractions it is not surprising that for a few years after the completion of her thesis she had little time for research. In 1906 Pierre Curie died in a tragic accident. The Sorbonne elected her to her husband’s chair and the rest of her life was largely spent in organising the research of others and attempting to raise funds. She made two long trips to America in 1921 and 1929. On her first trip she had been asked what she would most like to have. A gram of radium of her own was her reply, and she returned from America with a gram, valued at $100000. She also received $50,000 from the Carnegie Institution. In 1912 the Sorbonne founded the Curie laboratory for the study of radioactivity. It was opened in 1914 but its real work could only begin after the war, during which Marie Curie spent most of her time training radiologists. Later her laboratory, with its gram of radium, was to become one of the great research centres of the world.
Her position in France was somewhat odd. As a foreigner and a woman, France was never quite sure how to treat her. She was clearly very distinguished for in 1911 she was awarded her second Nobel prize, this time in chemistry for her discovery of radio and polonium. Her eminence was recognised by the creation of the Cure laboratory, yet at almost the same time she found herself rejected by the Academie des Sciences. She allowed her name to go forward n 1910 as the first serous female contender but was defeated. There is no doubt that this offended her. She refused to allow her name to be submitted for election again and for ten years refused to allow her work to be published in the proceedings of the Academie.
The following year, 1911, worse was to happen and she became the centre of a major scandal. The physicist and former pupil of her husband, Paul Langevin was accused of having an affair with her. Langevin had left his wife and four children, but although he was close to Madame Curie is by no means clear that there were grounds for the accusations. Some of her letters to Langevin were stolen and published in the popular press and doubts were raised about Pierre Curie’s death. Most of the attacks seem to have emanated from Gustave Tery, editor of L’Oeure and a former classmate of Langevin. Langevin retaliated by challenging Tery to a duel. Langevin faced Tery late in 1911 at 25 yards with a loaded pistol in his hand. Both refused to fire and shortly afterward the scandal died down.
Her major published work was the massive two-volume Treatise on Radioactivity (1910). The Curie’s daughter Irene and her husband Frederic Joliot-Curie continued the pioneering work on radioactivity and themselves received the Nobel Prize for physics.
As stated earlier the Curie family obtained, 5 Nobel Prizes, an achievement that has had no parallel in the history of science.