Ernest Rutherford (1871-1937)
Ernest Rutherford naquit en août 1871 à Nelson, en Nouvelle-Zélande. À partir de 1898, il fut avec Marie Curie le principal pionnier de l’exploration de l’atome. Il est surtout célèbre par sa mise en évidence en 1911 d’un noyau dans l’atome, mais on lui doit bien d’autres découvertes qui lui avaient valu le prix Nobel dès 1908. C’est lui en particulier qui identifia la nature des rayons alpha et bêta et formula la loi de décroissance radioactive.
In October 1895, landed in England a 24 years-old young New Zealander. His name was Ernest Rutherford and he travel halfway around the world to enter a prestigious laboratory, the Cavendish Laboratory at Cambridge.
A month after his arrival, the announcement of the discovery of X rays by Roentgen shook the scientific world and public opinion. JJ Thomson, who welcomed him, is just about to find the electron and to become famous. In 1897, Thomson guided his young assistant on the Becquerel rays that they just started to hear about.
By January 1898, after completing his thesis, he published a study on the radiation of uranium, where he wrote : "These experiments show that the radiation of uranium is complex and involves two distinct types of radiation: one that is easily absorbed and will be called for convenience the alpha radiation, and the other, a more penetrating one, which is called beta".
Appointed young professor at McGill University in Montreal, he met a young talented chemist in Canada, Frederick Soddy. With Soddy, he identifies radioactive emanation of radium as radon and he demonstrates that nature changes atoms when decaying.
That is still Rutherford who expresses the notion of the period and establishes a connection between alpha particles and helium. During his speech in Stockholm for the Nobel Prize in 1908, he even causes a stir by proving that these helium atoms are doubly charged.
Upon returning from Sweden, he started an experiment, known as his principal claim to fame. With extraordinary insight and flair, he interprets the results of his students Geiger and Marsden on "the diffusion of alpha particles" and shows the existence of a nucleus in the core of atoms in 1911.
video : Dr Brian Cox takes us on a journey through the history of particle physics. In this episode we learn how Ernest Rutherford conducted a historical experiment that revealed that most of the mass of an atom is concentrated in a tiny nucleus made of protons and neutrons.
Rutherford's discoveries between 1898 and 1919 deserve more Nobel Prizes and would be sufficient to many busy lives. He had an extraordinarily pragmatic and practical mind; he was open to any new developments unforeseen, but accepted a result or an assumption only if it was based on rigorous experimentation. He was immediately able to see the consequences even far away in time of a newly discovered property.
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