(The following information is paraphrased from "The Illustrated Encyclopedia of Astronomy and Space," Ian Ridpath, Thomas Y. Crowell, Publishers, New York, 1979, p. 142.)

**Sir Isaac Newton**

(1642-1727)

Isaace Newton is known as a British mathematical physicist whose discoveries included the idea of universal gravitation and important understandings in the field of optics. As a result of the Great Plague of 1665, Newton left Cambridge University to live in his home in Woolsthorpe, Lincolnshire, England. There, his research began and was continued on his return to the University after the threat of the plague had ceased. This work was summarized in his famous book, "Philosophiae Naturalis Principia Mathematica" (Mathematical Principles of Natural Philosophy), which is often called "Principia."

The crowning glory of Newton's work was the statement of understanding of the physical Universe in mathematical terms. This contribution combined the works of both Kepler and Galileo in a mathematical set of equations. Newton's work included the three famous laws of motion which comprise the laws of movement, momentum, and reaction of Earth's physical bodies. Furthermore, his understanding of the law of gravitation was stated as a mathematical formula which related gravitation attraction to the mass of two bodies and the distance between them. He found that the relationship was inversely proportional to the square of the distance separating two bodies.

In the field of mathematics, Newton founded Calculus in order to obtain proof of his results. Later use of Calculus proved very beneficial to science and technology. Newton's contributions to astronomy were numerous and innovative. He experimented with the dispersion of white light showing that white light was composed of a spectrum of every color of light. His work with light led to the design of a reflecting telescope which used mirrors not lenses. He constructed a mirror telescope in 1668, an item which has been one of the most important instruments of astronomy. His findings became the science of spectroscopy, which was the seed that grew into astrophysics, the study of the stars.