Legend to the letter: Einstein's links to French scientists

In 1905, the so-called miraculous year, Albert Einstein published five innovative works on the corpuscular structure of light, an approach to proving the existence of atoms by studying the movement of granules in a liquid, the theory of relativity, and his famous formula E=mc2 - describing the relationship between mass and energy.

Jean Perrin is a French physicist. Motivated by Einstein’s theories, he carried out, between 1905 and 1909, experimental research on the movement of granules suspended in a liquid to prove the existence of atoms. This triggered his election to the Académie des Sciences in 1923, and led to his 1926 Nobel Prize in Physics win.

On June 12 1933, Jean Perrin suggested the Academy of Sciences elect Albert Einstein as a foreign associate member. The Academy is one of the world's largest scientific institutions. Einstein gladly accepted this new international recognition.

On June 26, 1933, the Minister of National Education Anatole de Monzie, received correspondance from the Academy of Sciences announcing the Einstein’s election, and asking him to submit it for approval by Albert Lebrun, President of the Republic.

Albert Einstein responded with this the official letter confirming his election. The Académie des sciences welcomes him onboard. He can now attend the lectures and take part in the Academie’s works.

His election became official a few days later.

The election decree was sent to Einstein at Princeton University. With the rise of Hitler to power in Germany, Einstein moved permanently to Princeton in 1933, becoming a lifetime member of the new Institute for advanced study. He stayed for 22 years.

A few months after his election, Einstein - touched by this recognition - thanked the two secretaries of the Academy. He sent a first handwritten letter of thanks to Alfred Lacroix, Permanent Secretary of the 2nd Division (chemical, biological and medical sciences).

He sends a second typed letter to Émile Picard, Permanent Secretary of the 1st Division of the Academy of Sciences (mathematics and physics).

Albert Einstein completes his registration file and returns it.

He sends an autographed photo to the Academy.

Einstein had important exchanges with other members of the Academy, including French physicists and mathematicians like Henri Poincaré, Paul Langevin, Marie Curie, Jean Perrin, Maurice de Broglie, Jacques Hadamard, Paul Painlevé, and Emile Borel. He met them at the international Solvay congresses (in 1911, 1913, and 1927), as well as during visits to France in 1922 and 1929.

As a member of the Academy of Sciences, Albert Einstein finds two of his academic friends. This is the mathematician Elie Cartan and physicist Louis de Broglie with whom he has a long correspondence.

Here, a letter, to Elie Cartan, where he evokes the death of a relative of his. He mentions that the passage of time and the "now" are illusory.

Another letter to Elie Cartan between 1929 and 1932, Einstein and Cartan exchange many letters, with strong scientific content, and at a steady pace. Cartan takes the trouble to explain in detail to Einstein his theory of "involutionary" differential systems. Einstein is very happy to learn how to use this mathematical theory and thanks Cartan.

In another letter, to Elie Cartan, he alludes to the death of the son of Elijah, killed by the Germans.

Einstein's correspondence with Louis de Broglie and Elie Cartan sheds a particularly important light on the scientific ideas of the top intellect of the 20th century. This is a letter to Louis de Broglie.

In 1924, Einstein was the first to understand the importance of Louis de Broglie's ideas concerning the undulatory structure of matter. These ideas led Erwin Schroedinger to write his famous equation in 1926.

In 1953, as in this letter, a dialogue is established between Einstein and Louis de Broglie concerning the interpretation of the wave (psi) appearing in the Schröedinger equation.
In the last paragraph, Albert Einstein humorously quotes the Biblical episode on the Tower of Babel.