Marie Curie Finds Radium and Radioactivity
Here, behind me, on the Rue Vauquelin in Paris, France, there once stood a wretched, cold, wooden shed with no floor and a leaky roof. Inside that shed a husband and wife team created one of the most productive scientific laboratories in the world.
It was around the turn of the century, 1895 to 1905, that Marie and Pierre Curie, discovered two unusual new elements, radium and polonium. The atoms of these new elements shot out strange new rays that darkened photographic plates. Besides naming the new elements, Marie Curie, herself, coined the word that described this unusual new behavior. The atoms were, she wrote, "radioactive."
Let's follow the story of the Curies' discovery of radioactive atoms and see why it was of such significance to the development of modern physics and chemistry, and 20th century technology and society.
The time of the Curie's discovery was a time of rapid change in physics and chemistry. The outlines of a modern atomic theory had been slowly put together throughout the nineteenth century.
All things, chemists and physicists discovered, were made of tiny particles called atoms. These tiny atoms could arrange and rearrange themselves into molecules and crystals. The molecules and crystals joined together to make up all the "things" of the world-rocks, air and water, plants, animals and people. These same molecules and crystals acted together to make up all the "happenings" of the world-corrosion and fire, growth and decay, birth, life and death.
There were only a limited number of kinds of atoms. All of them could be grouped into what a Russian chemist named Dmitri Mendeleev called a Periodic Table of the Elements. The smallest atom was hydrogen, atom number one of the periodic chart. Next came helium, number two. This was followed by Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, and so forth, all the way up to number 92, uranium, the largest and heaviest of the natural elements. Our whole world, in other words, came in just 92 flavors.
When Mendeleev first proposed this way of grouping the atoms there were only 63 elements known to exist. Mendeleev was so sure of his theoretical grouping that he predicted more elements would be found to fill in the gaps in his listing.
And very soon most of the gaps were filled with new elements newly discovered by chemists and physicists in France, Germany, England and Italy. It was only a matter of time, many scientists thought, before the chart would be completely filled in, the properties of the individual elements completely described and the only work left for chemists and physicists would be to add a few decimal points to their charts and equations.
As one prominent scientist put it in 1895, "All the important discoveries have now been discovered; all the important inventions have now been invented."
One of the people who did not believe this was a poor Polish girl, Marie Sklodowska, born in Warsaw in 1867 (just after the Civil War in America and about the same time Mendeleev in Russia was first putting together his Periodic Chart of the Elements.)
Marie's father was a physics teacher at a high school in Warsaw, and her mother was the principal of a girls' school. She grew up in a stimulating intellectual atmosphere but also one of great sadness and privation.
Marie's mother died of tuberculosis when Marie was still a child. At that time Poland was under the domination of Russia and her father, being a patriotic Pole, was forced out of his teaching job.
As a result the family was poor and there was little money for the children's education. In addition, in order to keep the Polish people under their domination the Russians would not allow Polish young people to get a university education in their own country.
Marie was fascinated by science as a young girl and wanted above all to become a scientist. The only way this was possible was to leave Poland and get a university education in some other country. Marie had an idea how to do this. She would work and help support her older brother and sister while they got an education. Then, they in turn would help.her.
After high school she took work as a governess for a wealthy family and sent some of the money she earned to support her older brother and sisters education in Paris. In the meantime, fascinated by science, Marie studied from books and saved every penny she could, looking to the day she, too, could go to school in Paris.
That day finally came in 1891 when she took a train-fourth class, hardly better than a cattle car to Paris, and enrolled here in the world famous Sorbonne.
Her brother and sister helped her but her meager savings and their help barely paid for her tuition, books and a very small room - in the attic of a building near the Sorbonne. Marie had so little extra money for food that at times she literally fainted from hunger white trying to concentrate on lectures in physics.
When she graduated, however, in 1894, she graduated at the top of her class, That same year she met and then married a French chemist, Pierre Curie, who already had made a name for himself by discovering how crystals could generate electricity under certain conditions of pressure. Seldom have two people been more ideally matched. For their wedding they skipped the usual fancy clothes and wedding rings and instead bought bicycles on which they toured the countryside on their honeymoon.
These turn-of-the-century years were times of rapid change in the world of science. The same year they were married, 1895, William Roentgen in Germany was experimenting with high voltage tubes when he discovered a strange new invisible ray coming out of his tubes. This ray, he found, easily penetrated the skin of people, giving a picture of their bones on photographic film. Roentgen called these strange rays, x rays.
Within months Henri Becquerel in Paris found that a plain chunk of uranium (the heaviest known element) would also darken photographic plates. Another mysterious new "ray" had been discovered in England. William Crookes recently drew air out of a glass tube creating one of the best vacuums yet made. When he put a high voltage across the tube he found a ghostly column of light went from one pole to another. Crookes theorized that the ghostly light was some third kind of matter, different from ordinary atoms and molecules.
A few years later, J.J. Thomson and his colleagues at Cambridge University proved that this ghostly light was really a stream of tiny negatively charged particles that he called "electrons."
It is worthy of note while this research was going on, no one-neither the man on the street nor the scientist in the laboratory-had the least idea any of this would be of any practical use. The scientists who discovered the electron had a party and a famous toast to celebrate the discovery: "To the useless electron, long may it be so."
The crucial question for science was, what were these new rays? Where were they coming from? How did they fit onto the periodic chart?
Marie Curie entered this new world of strange rays and particles with zest, intelligence and an incredible capacity for hard work. For her doctors degree she investigated the rays coming from samples of uranium. She found that there were not one, but three types of rays-alpha, beta and gamma. Alpha rays were positively charged and bent in one direction by an electrical field.
Beta rays were negatively charged since they bent the opposite way. Gamma rays had no charge at all, but behaved like light and other electromagnetic waves.
It was Marie Curie who gave the name "radioactivity" to this unusual behavior of uranium.
She set herself to invent new ways to measure the intensity of this radioactivity. Using her new methods on many different samples of uranium she showed that some samples gave much more radiation than others, far more than could be accounted for by the amount of uranium present.
She guessed that there must some other more intensely radioactive element, as yet undiscovered, in some of those uranium samples.
Marie's husband Pierre realized she was opening doors into a new world and he abandoned his own work and came to work with her to explore this new world. At the time, Pierre was teaching full time at a physics school in Paris and Marie was a new mother of a baby girl, Irene. Between teaching and their parental duties the Curies worked long hours alone and together for the next seven years to solve some of the mysteries of these new rays and particles.
In 1898 Marie proved that, besides uranium, the element thorium was also radioactive. By July of that year, she and Pierre had successfully isolated a small pinch of another element from some uranium ore which they proved was hundreds of times as radioactive as uranium. It was a new element. Marie named it polonium after her home country.
Fall turned to winter and by December they had found`what they thought was a still more highly radioactive 'substance, perhaps an as yet undiscovered element in some of the uranium samples. They called this possible new element, radium.
The problem now was that they had such a tiny amount of this rare element they could detect it only by its radiations. To prove its existence they needed to have enough to see and to weigh.
To do this they realized they would need very large quantities of uranium ore, and would have an immense job of separation and purification.
Undaunted by the challenge they found a mine in what is now the Czech Republic that would give them the ore they needed. To the mine it was an unwanted waste. Pierre then convinced his physics school to let them use the unheated shed on this site in Paris for their laboratory, and they set to work.
Four YEARS later, thousands of laborious crystallizations, they succeeded in isolating a tenth of a gram of pure radium! Eventually they worked down eight tons of uranium ore to produce one gram of radium, which made it the rarest and most expensive substance in the world.
The next year, 1903, Marie finished her doctoral dissertation-one of the most famous scientific dissertations of all time. For it and for her and her husband's work on radiation, she and Pierre received a share of the Nobel Prize for Physics in 1903.
Tragedy struck the husband and wife team a few years later. Pierre was killed by a horse drawn carriage on the streets of Paris. Marie was devastated. By that time Pierre had obtained a coveted professorship at the Sorbonne, and in a unprecedented appointment, Marie was chosen to succeed him, becoming the first woman to ever teach at the Sorbonne. Her first lecture began at the exact point where Pierre had left off before his death.
The Curies' pioneering work on radioactivity was only a part, though a very important part, of the scientific changes in physics and chemistry in those early years of the 20th century. In this office at the Institute Curie in Paris, Marie worked for the last decades of her life, continuing her own research as well as directing the research of other scientists at the Institute. One of these scientists, Jean Perrin, said of her: "Madame Curie is not only a famous physicist, she is the greatest laboratory director I have ever known."
By now she was world famous, a colleague and friend of most of the famous physicists of the early 20th century, men like Ernest Rutherford and Albert Einstein-the scientists who, along with her, eventually put together a whole new view of the atom and of energy, of space and of time, the view that we share and profit from today.
Through their work our view of the atom changed from picturing it as a small marble to realizing that each atom was instead a tiny solar system of its own with an incredibly small nucleus made of protons and neutrons surrounded by fast moving electrons. Further research with that tiny nucleus, aided by Einstein's revolutionary view that matter itself could be converted to energy according to his famous e=mc2 scientists discovered nuclear energy.
Radioactive decay series, nuclear fission and fusion have been important. However, by far the most important results of this turn-of-the-century work with the atom and radiation has been to provide the scientific knowledge base for just about all the breakthroughs in electronics, chemistry and biology we are familiar with today in the final decade of the 20th century. Computers, television, antibiotics, DNA, plastics, thousands of new drugs, hundreds of thousands of new materials, space travel, none of these would have been possible without new knowledge of the basic physics and chemistry of the atom and of radiation. And for that basic knowledge we can thank Marie Curie and her turn-of-the century colleagues.
Despite this achievement and acclaim Marie Curie still suffered from sex discrimination when she was refused entry into the French Academy of Science simply and plainly because she was a woman.
In 1911 she received her second Nobel Prize, this time in chemistry, the first and as yet the only woman to be so honored.
Marie Curie also had the satisfaction of seeing one of her daughters become a famous chemist in her own right and win a Nobel Prize as Madame Irene Joliet-Curie. Her other daughter, Eve, became a well known writer and biographer.
Besides her scientific work, Madame Curie gave generously of herself to humanitarian work. During the first World War she organized a special ambulance with x ray equipment and often drove the ambulance herself to help wounded soldiers at the front. She was particularly interested in the uses of radium for treating cancer and other diseases. For a few decades it was used widely and still today radiation treatments are among the more successful of treatments for certain kinds of cancer.
Radioactive elements are also used in many other scientific studies, from tracing chemical pollutants in the biosphere to tracing the path of chemicals in the human body.
In 1922 Marie Curie travelled to America and was welcomed by President Harding at the White House. She toured the country afterwards to a succession of honorary degrees and other accolades to the most famous woman scientist of all time. Unfortunately she did not enjoy the public attention. Her friend and colleague Albert Einstein once wrote that "Marie Curie is, of all celebrated beings, the only one whom fame has not corrupted."
She was in ill health her final years and wrote her sister, "Sometimes my courage fails me and I think I ought to stop working, live in the country and devote myself to gardening. But I am held by a thousand bonds, and I don't know when I shall be able to arrange things otherwise. Nor do I know whether, even by writing scientific books, I could live without the laboratory."
Sadly and ironically, she herself suffered most from the very work that was her most precious satisfaction when she died at the age of 66 from a form of leukemia, probably caused by her long exposure to radioactive substances.