Mathematician and scientist, born in Oize, N France. He became a Minim Friar in 1611, and lived in Paris. Devoting himself to science, he corresponded with all the leading scientists of his day, including Descartes, Fermat, Pascal, and Hobbes, acting as a clearing house for scientific information. A pioneer in the theory of prime numbers, he also experimented with the pendulum and found the law relating its length and period of oscillation, studied the acoustics of vibrating strings and organ pipes, and measured the speed of sound. He also wrote on music, mathematics, optics, and philosophy.