Third Phase

In the third phase of his scientific career, he turned towards the field of radioactivity. His wife Marie was studying the phenomena of the penetrating radiation emitted by uranium compounds, which was discovered by Henri Becquerel. Fascinated by Becquerel’s discovery, Pierre and Marie began experimenting and in 1898, discovered two new radioactive substances – Polonium and later, Radium. This discovery marked a new history and opened a new field for scientists –the field of Radioactivity. In 1899, André Debierne, a colleague and student of Pierre, discovered actinium.

Pierre, abandoning his work on crystals, joined Marie in further research of unknown radioactive substances. They chose the ore pitchblende, a uranium ore, which in its pure state is about four times more active than uranium oxide. Pierre himself concentrated on the physical study of the new radioactive substances. He published two papers on the physiological action of radium rays after subjecting his arm to a burn and studying their toxic effects on mice and guinea pigs.

Eventually, he discovered that 1 gm of radium salts released 22,500 cal / h. The heat which Pierre first identified with atomic energy is much less than now produced by induced nuclear fission. He explained the effects of the rays including luminous and chemical effects in his research paper.

Experimenting on the action of magnetic fields on the radioactive rays, he proved the existence of particles and differentiated electrically as positive, negative and neutral. Ernest Rutherford later called them alpha (a), beta (ß) and gamma (g) rays. Further, he also observed the physiological effects of radium rays. This paved the way to cure the dreaded disease like cancer and this radium therapy become popular as Curie Therapy.

For their valuable work in the field of radioactivity, the Curies were awarded with the Nobel Prize in 1903. Pierre Curie worked under very trying conditions, with barely adequate laboratory facilities and under stress of having to take up teaching in order to earn their livelihood.

His works are recorded in numerous publications in the Competes Rendus de J’ Academie des Sciences, the Journal de Physique and the Annales de Physique et Chime. His complete works were published posthumously, in 1908.

Dr. Pierre Curie has left a legacy of 58 publications, based on which modern physics is taking shape.