Paul Langevin
French physicist, philosopher of science and pedagogue (1872-1946)
Paul Langevin (23 January 1872 – 19 December 1946) was a French physicist who was active at the beginning of the 20th century.
![](http://up.wiki.x.io/wikipedia/commons/thumb/9/9c/Paul_Langevin_Wellcome2.jpg/220px-Paul_Langevin_Wellcome2.jpg)
He invented sonar and worked with Albert Einstein.