In 1895, Perrin showed that
cathode rays were of negative
electric charge in nature. He determined the
Avogadro constant by several methods. He explained
solar energy as due to the thermonuclear reactions of
hydrogen. In 1901, Perrin proposed a hypothesis that each
atom has a positively charged
nucleus, similarly to
Hantaro Nagaoka later, but never developed it further. It came to be known the
Rutherford model. By the mid-1900s, Perrin was interested in
statistical mechanics questions, which are close to the study of
Brownian motion. Following
Albert Einstein's publication (1905) of a theoretical explanation of Brownian motion in terms of atoms, Perrin (along with Joseph Ulysses Chaudesaigues who was working in Perrin's lab) did the experimental work to test and verify Einstein's predictions, thereby providing data that would settle the century-long dispute about
John Dalton's
atomic theory, before the end of the decade. Perrin was the author of a number of books and dissertations. Most notable of his publications were: - "Les Principes, Exposé de thermodynamique" (Gauthier-Villars, 1901) - "Les Atomes" (Félix Alcan, 1913),translated into English, German, Polish, Russian… - "Matière et lumière - Essai de synthèse de la mécanique chimique", Ann. Physique, v9(11), 1919 - "La Recherche scientifique" (1933) - "Grains de matière et grains de lumière" (Hermann, Paris, 1935) - "Rayons cathodiques et rayons X" - "Electrisation de contact" - "Réalité moléculaire" - "Lumière et Reaction chimique". Perrin was also the recipient of numerous prestigious awards including the Joule Prize of the Royal Society in 1896 and the La Caze Prize of the
French Academy of Sciences. He was twice appointed a member of the
Solvay Committee at Brussels in 1911 and in 1921. He also held memberships with the
Royal Society of London and with the Academies of Sciences of Belgium, China, Prague, Romania, Soviet Unio, Sweden and Turin. He was Docteur honoris causa: universities of Berlin, Columbia, Ghent, Oxford, Princeton. In 1926, he was made Commander of the
Order of Léopold (Belgium) and of the French
Legion of Honour, then Grand officier in 1937. In 1919, Perrin proposed that
nuclear reactions can provide the source of energy in stars. He realized that the mass of a helium atom is less than that of four atoms of hydrogen, and that the
mass-energy equivalence of Einstein implies that the nuclear fusion (4 H → He) could liberate sufficient energy to make stars shine for billions of years. A similar theory was first proposed by American chemist
William Draper Harkins in 1915. It remained for
Hans Bethe and
Carl Friedrich von Weizsäcker to determine the detailed mechanism of
stellar nucleosynthesis during the 1930s. In 1927, Perrin founded the
Institut de biologie physico-chimique together with chemist André Job and physiologist André Mayer. Funding was provided by
Edmond James de Rothschild. In April 1933, following a petition by Perrin signed by over 80 scientists, among them eight Nobel Prize laureates, the new French education minister (succeeding in this position, to her friend Irène Curie, daughter of Pierre and Marie Curie) set up the Conseil Supérieur de la Recherche Scientifique (French National Research Council). In 1936, Perrin, now an undersecretary for research, founded the Service Central de la Recherche Scientifique (French Central Agency for Scientific Research). portrait by
Auguste Léon, 1918 At the same time, under the new Blum government, a fund was created to finance major public works projects to combat unemployment. Jean Perrin successfully used this fund to build laboratories (53 million francs), finance research (33 million francs), and create large-scale survey databases (13 million francs). It was within this framework that he founded, in 1937: - the Haute-Provence Observatory and the Paris Institute of Astrophysics, directed by Henri Mineur; - the Ivry Atomic Synthesis Laboratory, entrusted to Frédéric Joliot-Curie, which formed the beginnings of what would become the Atomic Energy Commission. The laboratory received, in particular, funding for the construction of a cyclotron; - the Laboratory for Large-Scale Chemical Processing, located in Vitry, was to be directed by Georges Urbain. His death in 1938 led to a change in the project, which became the Center for Metallurgical Studies under the direction of Georges Chaudron. The Institute of Human Biometrics, directed by Henri Laugier. - the Laboratory of Nutritional Physiology, directed by André Mayer. - the Institute for Research and History of Texts, which is part of the National Archives. - the General Inventory of the French Language, whose mission was to create the Littré dictionary of the 20th century. Finally, Jean Perrin took advantage of the 1937 Universal Exposition in Paris to found the
Palais de la Découverte, a
science museum in
Paris. == Personal life and death ==