Marin Mersenne, French mathematician and scientist, early 17th century.
© Science Museum / Science & Society Picture Library
In 1611 Marin Mersenne (1588-1648) became a Minim Friar. A resident of Paris, Mersenne was in contact with such scientists as Pascal, Hobbes and Descartes. Mersenne did research into pendulums and discovered the law between its length and period of oscillation.