In 1659, the first sketch of Mars was drawn by the Dutch astronomer, Christiaan Huygens. He used a telescope of his own design, which had a magnification of 50 times (much stronger than previous telescopes). He was also the first man to see the white south polar cap of the planet, and he estimated it revolved around the Earth once every 24 hours. Christiaan Huygens (1629-1695) was a prominent Dutch mathematician, astronomer, physicist and horologist. His work included early telescopic studies elucidating the nature of the rings of Saturn and the discovery of its moon Titan, the invention of the pendulum clock and other investigations in timekeeping, and studies of both optics and the centrifugal force. Huygens is seen as the first theoretical physicist as he was the first to use formulae in physics.