Sir Isaac Newton (1642-1727) was a famous English scientist. He invented a new kind of mathematics, discovered the secrets of light, and explained how the universe is held together. Image to left: Newton's discoveries in optics changed the world. By passing a beam of light through a prism, he showed that white light is made up of a rainbow-like band of colors. Credit: World Book illustration by Paul Turnbaugh Isaac Newton was born in Woolsthorpe, in Lincolnshire. He graduated from Cambridge University and became a professor there.

Newton realized that the force that makes a pebble fall is the same force that keeps the moon traveling around the Earth. This force is called gravity. It also keeps planets moving around the sun. Drawing of a wooden telescope Newton later discovered that sunlight is a mixture of all the colors of light. He passed sunlight through a glass called a prism, which separated it into colors. Then he studied its colors. He was able to show that objects have color because they reflect light. For example, grass looks green because it reflects green light. Image to right: A reflecting telescope designed by Newton used a reflecting mirror instead of the usual combination of lenses. Credit: World Book illustration by Robert Addison

Newton also invented a new kind of telescope. His telescope used a mirror instead of several lenses. Newton and a German scientist named Gottfried Leibniz each invented a new kind of math, called calculus, on their own. Calculus can answer questions about things that are changing. Scientists use calculus to solve problems. How to cite this article: To cite this article, World Book recommends the following format: "Sir Isaac Newton." The World Book Student Discovery Encyclopedia. Chicago: World Book, Inc., 2005.