Jean Baptiste Perrin, his discoveries resolved a dispute that had lasted a century

Jean Perrin

September 30, 1870, in Lille (France) – April 17, 1942, in New York (United States)

He studied in Lyon and then moved to Paris, where, in 1890, he entered the École Normale Supérieure.

Perrin compared the structure of the atom with a solar system, in which the planets would be the negative charges and the Sun would be a positive charge concentrated in the center of the atom. In 1895, he found that cathode rays deposit charge on an electroscope (an instrument that can read whether a body is electrically charged), thereby demonstrating the transfer of negative charges by cathode rays to the surface upon which they strike. He published his findings in the Académie des Sciences and Joseph J. Thomson became interested in measuring the speed of such particles, which would eventually be identified as electrons.

With this discovery, the electrical nature of the atom was confirmed, understanding it as the smallest and most indivisible unit of matter. In 1901, Perrin suggested that the attraction of negative charges surrounding the center (positive charge) is counteracted by the force of inertia.

Modelo de Jean Baptiste Perrin

Perrin was a pioneer in suggesting the discontinuous structure of the atom, however, he never insisted on designing an experiment that would help verify this concept.

This model was later supplemented and refined by Ernest Rutherford, who asserted that all positive charge in the atom was located in the center of the atom and that the electrons orbited around it. However, this model had some limitations that could not be explained at the time and the model was used as a basis by the Danish physicist Niels Bohr to propose his own in 1913.

When he finished, he was awarded a scholarship to research and present his thesis, in 1897, on "Les rayons cathodiques et les rayons Roentgen".

In 1898, he became professor of Physics-Chemistry at the Sorbonne University, a subject in which he was appointed professor at the Faculty of Sciences in 1910. He headed the department of Physics-Chemistry from 1927 to 1940.

Movimiento Browniano Perrin

In 1905, Albert Einstein published his theoretical explanation of Brownian motion (random motion observed in particles found in a liquid or gas medium as a result of collisions with the molecules of said fluid) in terms of atoms and Perrin made the experimental work to test and verify Einstein's predictions, thus settling the century-long dispute over John Dalton's atomic theory.

In 1909, he published his research on the Brownian motion of particles in aqueous solution, indicating that said motion was a consequence of the incessant bombardment of the particles by water molecules and offering estimates of their size and the value of Avogadro's Number (number of molecules contained in a mole of gas under normal conditions) more exact than those that existed up to that time. The results of his experiments were accepted as proof of the existence of molecules.

In 1918, he was made a member of the prestigious Royal Society of London and, in 1923, he entered the Académie des Sciences.

In 1919, he realized that the mass of one helium atom is less than that of four hydrogen atoms and that Einstein's mass-energy equivalence implies that nuclear fusion could release enough energy to make stars shine for a long time. billions of years.

In 1926, he received the Nobel Prize in Physics for his work on the discontinuous structure of matter and for the discovery of the sedimentation equilibrium.

In 1936, he became part of the government of León Blum as Undersecretary of State for scientific research, for which he was able to promote the Palais de la Découverte (1937) and the Center National de la Recherche Scientifique (1939).

Libros de Jean Perrin

Among his works it is worth mentioning: “Osmose et parois semi-perméables” (1900), “Principles of Physical Chemistry” (1901), “Les Atomes” (1912) and “Les éléments de la physique” (1930).

In 1940, he moved to the United States where he headed the scientific department at the Free School of Advanced Studies in New York.

His son, Francis Perrin, was also a physicist, a specialist in nuclear fission, and headed the French Atomic Energy Commission (CEA) from 1951 to 1970.

He died on April 17, 1942 in New York, but his ashes were transported to the Pantheon in Paris on November 17, 1948.


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