Pioneer of Radioactivity
By Professor Hélèn Langevin-Joliot
(Granddaughter of Marie Curie)
Hélène Langevin-Joliot (born 17 September 1927) is a French nuclear physicist.
Madam Curie started out by being just an assistant but became very famous. On the way she had many difficulties to overcome.
“I keep a sort of hope that this will not disappear into nothingness”
Marie Skłodowska-Curie (7 November 1867 – 4 July 1934) was a Polish and naturalised-French physicist and chemist who conducted pioneering research on radioactivity.
Maria Skłodowska was born in Warsaw, in the Russian partition of Poland, on 7 November 1867, as the fifth and youngest child of well-known teachers Bronisława, née Boguska, and Władysław Skłodowski. Maria’s older siblings were Zofia (born 1862), Józef (1863), Bronisława (1865) and Helena (1866).
Marie’s early life was quite a struggle. The family had lost property and money by being involved in Polish national uprisings and in fact her father was fired from his job for this. To make some money they took in lodgers.
Marie lost her mother to TB when she was ten years old and this is probably why she sent to boarding school. She later went on to attend a gymnasium for girls, from which she graduated on 12 June 1883 with a gold medal as she was a very good student.
After leaving school she began tutoring as she was not allowed to go to university because she was a woman. However she and her sister Bronisława became involved with the clandestine Flying University, a Polish patriotic institution of higher learning that admitted women students.
Marie made a pact with her sister Bronisława, that she would give her financial assistance during Bronisława’s medical studies in Paris, in exchange for similar assistance two years later. So she began her working life as a governess, first as a home tutor in Warsaw; then for two years as a governess in Szczuki with a landed family, the Żorawskis, who were relatives of her father.
Władysław Skłodowski with daughters (from left) Maria, Bronisława, Helena, 1890
At the beginning of 1890, Bronisława invited Marie to join her and her husband in Paris but Marie had to decline as she hadn’t saved enough money for the university tuition fees. During her years as a governess she continued to educate herself, reading books, exchanging letters, and being tutored herself and she began her practical scientific training (1890–91) in a chemical laboratory at the Museum of Industry and Agriculture at Krakowskie Przedmieście 66, near Warsaw’s Old Town.
In late 1891 she left Poland for France. In Paris Marie found she wasn’t as prepared as she first though and briefly found shelter with her sister and brother-in-law before renting a garret closer to the university, in the Latin Quarter, and proceeding with her studies of physics, chemistry and mathematics at the University of Paris, where she enrolled in late 1891. She subsisted on her meagre resources, suffering from cold winters and occasionally fainting from hunger.
Marie studied during the day and tutored evenings, barely earning her keep. In 1893 she was awarded a degree in physics and began work in an industrial laboratory of Professor Gabriel Lippmann. Meanwhile she continued studying at the University of Paris, and with the aid of a fellowship she was able to earn a second degree in maths in 1894.
Marie had begun her scientific career in Paris with an investigation of the magnetic properties of various steels, commissioned by the “The Society for the Encouragement of National Industry”.
In July 1894 Pierre Curie entered her life; it was their mutual interest in natural sciences that drew them together. It was a decisive encounter and she later described the relationship as “our scientific dream”.
Pierre Curie (15 May 1859 – 19 April 1906) was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity.
Piezoelectricity is the electric charge that accumulates in certain solid materials (such as crystals, certain ceramics, and biological matter such as bone, DNA and various proteins) in response to applied mechanical stress.
In 1880 Pierre and his brother had published the first in a series of papers about the discovery of piezoelectricity. 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 in her studies of radioactivity.
Pierre was an instructor at the School of Physics and Chemistry, the École supérieure de physique et de chimie industrielles de la ville de Paris (ESPCI). They were introduced by the Polish physicist, Professor Józef Kowalski-Wierusz, who had learned that Marie was looking for a larger laboratory space, something that Kowalski-Wierusz thought Pierre had access to. Though Pierre did not have a large laboratory, he was able to find some space for Marie where she was able to begin work and she helped change his view of women.
Their mutual passion for science brought them increasingly closer, and they began to develop feelings for one another. Eventually Pierre proposed marriage, but at first Marie did not accept as she was still planning to go back to her native country. Pierre, however, declared that he was ready to move with her to Poland, even if meant being reduced to teaching French.
In the summer of 1895 Marie had a holiday in Poland to visit her family, hoping that it might be possible to get a job there in her chosen field, but she was denied a place at Kraków University because she was a woman. A letter from Pierre convinced her to return to Paris to pursue a PhD.
They married on the 26th July 1895. He was promoted to professor at the École supérieure de physique et de chimie industrielles de la ville de Paris but the most historic part was that Marie was able to work there too.
Pierre and Marie Curie in the laboratory
In 1895 Wilhelm Roentgen discovered the existence of X-rays, though the mechanism behind their production was not yet understood. In 1896 Henri Becquerel discovered that uranium salts emitted rays that resembled X-rays in their penetrating power. He demonstrated that this radiation, unlike phosphorescence, did not depend on an external source of energy but seemed to arise spontaneously from uranium itself. This was very surprising and Marie was influenced by these two important discoveries, and decided to look into uranium rays as a possible field of research for a thesis.
In her research she was able to use the electrometer that had been developed by Pierre and his brother fifteen years earlier. Through her work she discovered that uranium rays caused the air around a sample to conduct electricity. She showed that the activity of the uranium compounds depended only on the quantity of uranium present. She hypothesised that the radiation was not the outcome of some interaction of molecules but must come from the atom itself, i.e. uranic rays were an atomic property. This hypothesis was an important step in disproving the ancient assumption that atoms were indivisible. This led her to search for other elements that emitted radiation, e.g. Thorium.
In 1897 Marie and Pierre had a daughter, Irene and to improve the family finances Marie began teaching at the École Normale Supérieure.
Pierre, Irène, Marie Curie
The Curies did not have a dedicated laboratory; most of their research was carried out in a converted shed next to the School of Physics and Chemistry. The shed, formerly a medical school dissecting room, was poorly ventilated and not even waterproof, and of course they had no idea how dangerous unprotected work with radioactive substances was. The shed became very badly contaminated.
Marie’s systematic studies included two uranium minerals, pitchblende and torbernite (also known as chalcolite). Her electrometer showed that pitchblende was four times as active as uranium itself, and chalcolite twice as active. She concluded that, if her earlier results relating the quantity of uranium to its activity were correct, then these two minerals must contain small quantities of another substance that was far more active than uranium. She began a systematic search for additional substances that emit radiation, and by 1898 she discovered that the element thorium was also radioactive.
This had been all Marie’s own work but Pierre was so intrigued by her results that he gave up his own research on crystals to join her. Together they carried out analytical chemistry and activity measurements on samples but she always made it abundantly clear that the research ideas were all her own. Even at this early stage of her career realised that many scientists would find it difficult to believe that a woman could be capable of the original work in which she was involved.
On 14 April 1898 the Curies optimistically weighed out a 100-gram sample of pitchblende and ground it with a pestle and mortar. However, they later realised that what they were searching for was present in such minute quantities that they would eventually have to process tons of the ore.
In July 1898 Curie and her husband published a joint paper announcing the existence of an element which they named “polonium”, in honour of her native Poland and celebrated by having a summer holiday with the baby.
On 26 December 1898, the Curies announced the existence of a second element, which they named “radium”, from the Latin word for “ray”. In the course of their research, they also coined the word “radioactivity”.
To prove their discoveries beyond any doubt, the Curies sought to isolate polonium and radium in pure form. To do this they had to separate out the radium salt by differential crystallisation. From a ton of pitchblende, one-tenth of a gram of radium chloride was separated in 1902. In 1910 Marie isolated pure radium metal. She never succeeded in isolating polonium, which has a half-life of only 138 days.
Between 1898 and 1902 the Curies published, jointly or separately, a total of 32 scientific papers, including one that announced that, when exposed to radium, diseased, tumour-forming cells were destroyed faster than healthy cells.
In 1900 Marie became the first woman faculty member at the École Normale Supérieure and in June 1903, having been supervised by Gabriel Lippman, she finally finished her thesis and was awarded her doctorate from the University of Paris. Pierre joined the faculty of the University of Paris.
Jonas Ferdinand Gabriel Lippmann (16 August 1845 – 13 July 1921) was a Franco-Luxembourgish physicist and inventor, and Nobel laureate in physics for his method of reproducing colours photographically based on the phenomenon of interference.
Also in June 1903 Marie and Pierre were invited to the Royal Institution in London to give a speech on radioactivity; however Pierre had to do the speech alone as being a woman, Marie was prevented from speaking.
In December 1903, the Royal Swedish Academy of Sciences awarded Pierre Curie, Marie Curie, and Henri Becquerel the Nobel Prize in Physics, “in recognition of the extraordinary services they have rendered by their joint researches on the radiation phenomena discovered by Professor Henri Becquerel.” At first, the Committee intended to honour only Pierre and Becquerel, but one of the committee members and an advocate of woman scientists, Swedish mathematician Magnus Goesta Mittag-Leffler, alerted Pierre to the situation, and after his complaint, Marie’s name was added to the nomination. Marie was the first woman to be awarded a Nobel Prize.
The Nobel Prize money allowed them to hire their first laboratory assistant and through numerous complaints they finally got a proper laboratory in 1906.
In December 1904, Curie gave birth to their second daughter, Ève
Ève, Marie and Irene Curie in 1908
By April 1906 the Curie’s had concluded that radioactivity was completely random, that a new kind of energy was involved, that there were many different radio elements and that it was spontaneous transformation of one chemical element into another with emission of radiation.
Disaster struck on 19 April 1906 when Pierre was killed by a horse-drawn vehicle when walking across the Rue Dauphine in heavy rain. Marie was devastated. She was now a widow with two young children.
On 13 May 1906 the physics department of the University of Paris decided to retain the chair that had been created for Pierre and to offer it to Marie. She accepted it hoping to create a world-class laboratory as a tribute to Pierre. She was now the director of her own lab and gave her first lecture on November 5th 1906. She was the first woman to become a professor at the University of Paris.
In 1909 there was an initiative to create the Radium Institute (Institut du radium, now Curie Institute, Institut Curie), by the Pasteur Institute and the University of Paris because Pierre Paul Émile Roux, director of the Pasteur Institute had been disappointed that the University of Paris was not giving Curie a proper laboratory.
In 1910 having succeeded in isolating radium Marie defined an international standard for radioactive emissions that was eventually named for her and Pierre: the curie. There was a setback in 1911, however, in that the French Academy of Sciences did not elect her to be a member by a couple of votes.
International recognition for her work had been growing to new heights, and the Royal Swedish Academy of Sciences honoured her a second time, with the 1911 Nobel Prize in Chemistry. This award was “in recognition of her services to the advancement of chemistry by the discovery of the elements radium and polonium, by the isolation of radium and the study of the nature and compounds of this remarkable element.”
Curie’s second Nobel Prize enabled her to persuade the French government into supporting the Radium Institute, which was eventually built in 1914. Here research was conducted in chemistry, physics, and medicine.
During World War I, Curie saw a need for field radiological centres near the front lines to assist battlefield surgeons. After a quick study of radiology, anatomy, and automotive mechanics she procured X-ray equipment, vehicles, auxiliary generators, and developed mobile radiography units, which came to be popularly known as petites Curies (“Little Curies”). She became the director of the Red Cross Radiology Service and set up France’s first military radiology centre, operational by late 1914. She later trained nurses how to use the X-ray machines.
Marie in a mobile X-ray vehicle
In 1915 Marie produced hollow needles containing ‘radium emanation’, a colourless, radioactive gas given off by radium, later identified as radon, to be used for sterilising infected tissue.
In 1920, for the 25th anniversary of the discovery of radium, the French government established a stipend for Marie and in 1921 she was welcomed triumphantly when she toured the United States to raise funds for research on radium. US President Warren G. Harding received her at the White House to present her with 1 gram of radium and Mrs. William Brown Meloney, after interviewing her, created a Marie Curie Radium Fund to raise money to buy radium and to publicise her trip. This fund-raising was necessary as France was ruined after the war. There was no money and radium necessary to investigate gamma radiation had gone missing from the labs.
The French government, recognising her growing fame abroad, and embarrassed by the fact that she had no French official distinctions to wear in public, offered Marie a Legion of Honour award, but she refused. In 1922 she became a fellow of the French Academy of Medicine because of her awareness of how her discoveries could benefit medicine.
In August 1922, Marie Curie became a member of the newly created International Commission for Intellectual Cooperation of the League of Nations.
Around this time she became interested in strong radioactive sources and the use of alpha particles to investigate matter.
In 1930, she was elected a member of the International Atomic Weights Committee where she served until her death.
In 1933 she was described as rather a mythical figure. On the 15th January 1934, in a letter to her daughter Eve about the discovery of artificial radioactivity she wrote “I have given a great deal of time to science because I wanted to, because I loved research”.
On 4 July 1934, Marie died at the Sancellemoz Sanatorium in Passy, in Haute-Savoie, from aplastic anaemia believed to have been contracted from her long-term exposure to radiation. Professor Langevin-Joliot described her as an affectionate mother and grandmother.