Paul Langevin

Paul Langevin

Paul Langevin (23 January 1872 – 19 December 1946) was a French physicist who developed Langevin dynamics and the Langevin equation. He was one of the founders of the Comité de vigilance des intellectuels antifascistes, an anti-fascist organization created after the 6 February 1934 far right riots. Being a public opponent of fascism in the 1930s resulted in his arrest and being held under house arrest by the Vichy government for most of World War II. Langevin was also president of the Human Rights League (LDH) from 1944 to 1946, having recently joined the French Communist Party.

He was a doctoral student of Pierre Curie and later a lover of widowed Marie Curie. He is also known for his two US patents with Constantin Chilowsky in 1916 and 1917 involving ultrasonic submarine detection. He is entombed at the Panthéon.

Biography

Paul Langevin was born on 23 January 1872 in Paris. Langevin graduated from ESPCI Paris in 1892 with a degree in Physics. He then studied at the École normale supérieure, where he passed the agrégation in 1897. The following year, he went to the University of Cambridge, where he studied under J. J. Thomson in the Cavendish Laboratory. In 1901, Langevin became a preparator in the Physics Teaching Laboratory at the University of Paris, where he received his Ph.D. the following year, supervised by Pierre Curie.

From 1903 to 1905, Langevin served as Curie's deputy at ESPCI Paris, where he became a professor in 1905, and Director of Studies in 1908. In 1909, he was appointed to the Chair of General and Experimental Physics at the Collège de France, where he remained until his death in 1946.

Research

Langevin is noted for his work on paramagnetism and diamagnetism, and devised the modern interpretation of this phenomenon in terms of electron spin. His most famous work was in the use of ultrasound using Pierre Curie's piezoelectric effect. During World War I, he began working on the use of these sounds to detect submarines through echo location, though the war ended before the system became operational. During his career, Paul Langevin also spread the theory of relativity in academic circles in France and created what is now called the twin paradox.

Personal life

In 1898, he married Emma Jeanne Desfosses, and together they had four children, Jean, André, Madeleine and Hélène.

In 1910, he had an affair with the then-widowed Marie Curie; some decades later, their respective grandchildren, grandson Michel Langevin [fr] and granddaughter Hélène Langevin-Joliot married one another. He was also noted for being an outspoken opponent of Nazism, and was removed from his post by the Vichy government following the occupation of the country by Nazi Germany. He was later restored to his position in 1944. He died in Paris in 1946, two years after living to see the Liberation of Paris. He is buried near several other prominent French scientists in the Panthéon in Paris.

In 1933, he had a son with physicist Eliane Montel (1898–1993), Paul-Gilbert Langevin, who became a renowned musicologist.

His daughter, Hélène Solomon-Langevin, was arrested for Resistance activity and survived several concentration camps. She was on the same convoy of female political prisoners as Marie-Claude Vaillant-Couturier and Charlotte Delbo.

Submarine detection

In 1916 and 1917, Paul Langevin and Chilowsky filed two US patents disclosing the first ultrasonic submarine detector using an electrostatic method (singing condenser) for one patent and thin quartz crystals for the other. The amount of time taken by the signal to travel to the enemy submarine and echo back to the ship on which the device was mounted was used to calculate the distance under water.

In 1916, Lord Ernest Rutherford, working in the UK with his former McGill University PhD student Robert William Boyle, revealed that they were developing a quartz piezoelectric detector for submarine detection. Langevin's successful application of the use of piezoelectricity in the generation and detection of ultrasound waves was followed by further development.

Recognition

Awards

Memberships

Achievements

• Foreign Member of the Royal Society — 1928
• Copley Medal — 1940
• Grand Cross of the Legion of Honour — 1946
• Hughes Medal — 1915
• Notable work: La Pensée et l'Action
• Notable work: La physique depuis vingt ans
• Held posts at Collège de France and ESPCI Paris, PSL University
• Educated at ESPCI Paris, PSL University, University of Cambridge and University of Paris
• Fields of research: chemistry, experimental physics, pedagogy and philosophy of science