December 19, 2018 – Lecture: "Jean Perrin: From the Atom to the Palais de la Découverte"
Kamil FADEL, Director of the Physics Department at the Palais de la Découverte, will give a lecture on Jean Perrin, from the atom to the Palais de la Découverte.
Wednesday, December 19, 2018
Classroom 16.01 at 1:15 p.m.
Faculty of Sciences – Triolet Campus
Jean Baptiste Perrin (September 30, 1870, in Lille, France – April 17, 1942, in New York, United States) was a French physicist, chemist, and politician.
He was awarded the 1926 Nobel Prize in Physics “for his work on the discontinuity of matter, and particularly for his discovery of sedimentation equilibrium¹.”
In 1895, Jean Perrin demonstrated that cathode rays consist of negatively charged particles.
After Albert Einstein published (in 1905) his theoretical explanation of Brownian motion based on the random movement of molecules, Jean Perrin conducted experiments to verify Einstein’s predictions. In 1908, he demonstrated a complete agreement between theory and experiment, confirming the actual existence of atoms—a concept proposed a century earlier by John Dalton—and he determined, using several methods, a precise value for Avogadro’s number.
In 1919, Perrin proposed that nuclear reactions could be the source of energy for stars. He noted that the mass of a helium atom is less than that of four hydrogen atoms and that Einstein’s mass-energy equivalence implies that the energy released by the 4 H → He reaction could be sufficient to keep stars shining for billions of years. It would fall to Hans Bethe and Carl Friedrich von Weizsäcker to elucidate the detailed mechanism of the reaction during the 1930s2,3.
