Marin Mersenne, (born 8 September 1588, in modern-day Sarthe, died 1 September 1648, in Paris) was a French theologian and mathematician. He developed the first laws of acoustics, which was known by his name for a long time. Today, he is mainly remembered for the Mersenne primes. Together with Galileo Galilei he built the laws which describe how a mass falls in an empty space. He was in favour of modern science, and did not agree with "occultist" movements.