Christiaan Huygens (1629 - 1695),
Dutch mathematician,
physicist and
astronomer.
Among many other things, Huygens worked on improving
telescope lenses, and in 1655 he discovered Titan,
a satellite of Saturn, and studied Saturn's
impressive ring system. In 1659 he published his
findings in Systema Saturnium.
Additionally, he developed a wave theory of
light, as opposed to the corpuscular theory of
Newton who saw light as particles,
and formulated Huygen's Principle;
"Concerning light waves, every point on a wave
front is itself a source of new waves."
Huygens was also the inventor of the pendulum clock,
and he was the first one to discover the
polarization of light.