Christiaan Huygens
Dutch mathematician and physicist in the17th century. Probably he is most famous for the wave theory of light (Traite de la lumiere, 1678), but he studied and wrote on various topics; a treatise on probability and games of chance (De Ratiociniis in Ludo Aleae, 1657), observations of the Saturn's rings (Systema Saturnium, 1659), the study and improvement of clocks and the pendulum (Horologium Oscillatorium, 1673), and the theory of motion, etc.
Huygens was a mathematical mentor of Leibniz, and both were relativists against absolutists of motion (and space and time) like Newton; they left important correspondence on relative and absolute motions.
See a biography in McTutor History of Math.