Radioactivity and the woman who discovered it

One of the most iconic female scientists, Marie Curie was the first scientist to share not one but two Nobel Prizes. She not only influenced the world, but her own family too.

Marie Curie was born Maria Sklodowska in 1867 – her parents were teachers: her mother ran a boarding school for girls and her father taught physics and mathematics. She was born in Warsaw, Poland, and remained there until 1891 when she followed her sister to Paris. While in Paris she studied physics, chemistry and maths at Sorborne, the University of Paris¹.

Maria – now known as Marie – studied during the day and tutored during the evenings. She barely earned her keep, but was awarded her physics degree in 1893. She continued studying and earned a degree in mathematics in 1894.

It was also this year that she met Pierre Curie – an instructor in the School of Physics and Chemistry – who was to become her husband and scientific collaborator. Their mutual interest in magnetism drew the pair together, but they are most well-known for their work on radioactivity. They married in 1895, shortly after Marie returned to Paris following rejection from Kraków University simply because she was a woman.

In 1986, Henri Becquerel discovered radioactivity – he noticed that uranium salts emitted rays resembling x-rays in their penetrating power, but didn’t require an external energy source. Marie was inspired and decided to look at uranium rays as a possible field of research for her thesis. Using an electrometer – a device developed by Pierre and his brother to measure electrical charge – she discovered that uranium rays caused the air around the sample to conduct electricity.

Using this technique, she discovered that the activity of uranium compounds must come from the atoms themselves. Her systematic studies included two uranium containing minerals – pitchblend and chalcolite.  Pitchblend was four times as radioactive as uranium and chalcolite twice as active – meaning something within them was more radioactive than the uranium. What’s more, she discovered thorium was the same.

Author Robert William Reid wrote: “The idea was her own; no one helped her formulate it and although she took it to her husband for his opinion she clearly established her ownership of it.”²

Marie knew the importance of publishing promptly – but perhaps for fear her work would not be taken seriously because she was a woman, her former professor Gabriel Lippmann presented her work to the Académie des Sciences in April 1898. Gerhard Schmidt had two months previously published his work on thorium, but no one had noticed Marie’s observation describing the relative reactivities of uranium, chalcolite and pitchblend.

At this point, Pierre joined Marie in investigating radioactivity and the two made some amazing discoveries. In July 1898 they published a paper announcing the existence of polonium – so called after Marie’s native Poland. In December that year, they also revealed the element radium and coined the word radioactivity.

But it didn’t stop there – they pair continued to attempt to break pitchblend into its constituents, obtaining traces of radium albeit contaminated with barium. Marie continued with her thesis working under Becquerel, and was awarded her DSc from the University of Paris in 1903.

Also that year, Pierre and Marie shared the Nobel Prize in Physics with Becquerel. At 36, Marie was the first female to receive the award, and in 1911 when she received the Nobel Prize for Chemistry became the first person to win or share two. She is only one of two people to have been awarded the prize in two fields. (The other is Linus Pauling; the first in Chemistry in 1954 for his research on the chemical bond, and the second for Peace in 1962 for campaigning against nuclear weapons testing.)

Winning the prize made the Curie’s instantly famous – Pierre was given a professorship and permitted to establish his own lab at Sorbonne and Marie became the director of research. In 1906, Marie took over Pierre’s position after he was killed in a street accident, becoming the first female professor at the University. Following her second Nobel Prize win, she was able to gain funding from the French government for the Radium Institute, built in 1914. In 1932, a second Radium Institute was built in Marie’s hometown of Warsaw. Both later changed their name to Curie Institute.

Shortly after the second Radium Institute was completed, Marie died. She passed away on 4th July 1934 from aplastic anaemia – similar to leukaemia, the bone marrow doesn’t produce enough new red and white blood cells and platelets to replenish the blood – it was almost certainly caused by exposure to radiation.  Her laboratory is preserved at the Museé Curie, and her papers – and even her cookbook – are considered to be too radioactive to handle; they’re still kept in lead-lined boxes.

Marie was laid to rest in Sceaux alongside her husband, but both were transferred to the Paris Panthéon in honour of their achievements. She became the first – and so far only woman – to be honoured in this way.

The legacy of Curie is far reaching; she is considered one of the most famous female scientists to date and received many awards and accolades in Chemistry both while alive – including Nobel Prizes, the Davy, Metteucci and Elliott Cresson Medals – and after her death. Several institutions in Poland and France are named after Marie and her husband Pierre, along with more in America where Marie visited to raise funds for her radium research.

The curie (Ci) – a unit of radioactivity – is named after the Curies, as is the element curium. Three radioactive minerals are also named after Marie: curite; sklodowskite; and cuprosklodowskite. The Curies’ work helped overturn established ideas in physics and chemistry and formed the basis of subsequent research in nuclear physics and chemistry.

Professor L Pearce Williams from Cornell University observed: “The result of the Curies’ work was epoch-making. Radium’s radioactivity was so great that it could not be ignored. It seemed to contradict the principle of conservation of energy and therefore forced a reconsideration of the foundation of physics.”³

Williams said the discovery of radium provided Ernest Rutherford with sources of radioactivity in order to probe the structure of the atom, which lead to the hypothesis of a nuclear atom. It also offered a means by which cancer could be attacked and the Marie Curie Cancer Care charity is named in honour of Marie.

As the first person to win two Nobel Prizes, Marie Curie’s work on radioactivity left a long-lasting legacy, not only on the world, but on her children. Her eldest daughter Irene helped Marie to run field hospitals in World War I – they pushed for the use of mobile x-ray units powered by radium for the treatment of wounded soldiers – and worked in the Radium Institute in Paris. She married one of her mother’s pupils, Frédéric Joliot, and together they discovered that one element could be turned into another by bombarding it with alpha particles to give radioactive isotopes. They were awarded the Nobel Prize for Chemistry in 1935. Unfortunately, Irene suffered a similar fate to her mother and died of radiation-induced leukaemia in 1946, aged 58.

Her younger daughter, Ève was also influenced by Marie. Although she obtained a science degree, Ève preferred the arts and became a writer and journalist and wrote Marie’s Biography Madame Curie. She didn’t receive a Nobel Prize like the rest of her family (although her husband Henry Richardson Labouisse Jr  accepted the Nobel Peace Prize on behalf of UNICEF in 1965), but she did live a long life, reaching the age of 102 before she died in her sleep in October 2007.

As one of the most iconic female scientists, Marie is better known than her husband, but the pair’s influence was – and hopefully still is – far-reaching. Not only did they discover several radioactive elements but they coined the term radioactivity and opened up a whole new branch of science. Their workbooks today still remain too radioactive to handle – their legacy is surely to be remembered for as long as radium’s half-life.