Sir Isaac Newton was an English physicist, astronomer and mathematician. He is best known for his theory of universal gravitation which became the basis for many subsequent scientific astronomical studies. Newton is considered one of, if not the most influential astronomers of all time. Besides his contributions to this field, he also invented a new form of math which he called calculus, and he discovered the secrets of light and color.
The Law of Gravity
In August 1684 Newton's work was interrupted by a visit from Sir Edmund Halley, the British astronomer and mathematician. Halley had come to discuss a problem he was having with orbital motion. Newton had previously studied the mechanics of planetary motion and this renewed his interest in it. During the following two and a half years he formulated three laws of motion. He applied these laws to Kepler's laws of orbit motion to come up with the law of universal gravitation. Newton said that the law of the universal force came to him one day when he was sitting in his garden drinking tea, and an apple fell out of a tree. It was at that time that he realized that the same force that attracted the apple toward the Earth is also what keeps the Moon in its orbit. Newton would publish his revolutionary findings in a book called "The Principia" which would mark a turning point in the history of science.
The law of gravity was not Newton's only important contribution to astronomy, his discoveries in light and optics were equally important. He used a prism to better understand the properties of light. What he discovered was that white light was actually created by a mixture of all the different primary colors. He conducted numerous experiments to study the different elements of light and published these finding in his book "Optics" in 1704. The properties that were recorded in "Optics" are still used today by scientists in order to determine the temperature, chemical composition, and even the speed of everything from a distant glowing star to material that has been heated in a laboratory. Newton took his knowledge of light and developed a new type of telescope. Traditional telescopes consisted of a series of lenses, but instead his new telescope used a reflecting mirror which greatly increased the magnification. The first telescope he constructed was only six inches long and through it Newton was able to see Jupiter's satellites.