Christiaan Huygens was a Dutch astronomer, mathematician, and physicist whose numerous original scientific discoveries earned him wide recognition among scientists of the 17th century. Among his discoveries was the wave theory of light which was based on his principle that states that every point on the front of an advancing wave is itself a source of new waves. The need for an exact measure of time for observing the heaven lead him to use a pendulum to regulate the movement of clocks. Huygens did a further study into the correlation of the length of a pendulum and the period of oscillation. This lead him to formulate theories on the centrifugal force in circular motion which would influence Sir Isaac Newton in formulating the Law of Gravity.
He wanted to find a better way to study the solar system, so he started to work on ways to develop sharper definition lenses. He developed a new technique to polish the lenses and was able to discover the first satellite of Saturn. Huygens also was able to explain Galileo's observations that Saturn appeared to be a triple planet. He showed that this appearance was due to the rings of Saturn which were previously undiscovered.
The Martian Day
Huygens also studied and drew the first maps of Mars. While studying Mars he noticed a V-shaped mark, later named the Syrtis Major, that reappeared every 24 hours. He deduced from this terrestrial feature that this time period represented the length of the Martian day.