Sir Isaac Newton (1642-1727) was an English scientist and mathematician who was considered one of the most important scientists of all time. Newton formulated laws of universal gravitation and motion—laws that explain how objects move on Earth as well as in outer space. He studied the behavior of light and built the first reflecting telescope. He invented the area of mathematics called calculus.

Newton’s helped explain the world in mathematical terms, which suggested that science may provide explanations for other phenomena as well (this was really the beginning of modern science!).

Newton made sundials, model windmills, a water clock, and a mechanical carriage when he was just a boy. However, he did rather poorly in school because he didn’t pay attention!

He recorded his first thoughts on gravitation when he saw an apple fall from a tree. At the time, Newton was trying to determine what type of force could hold the Moon in its path around Earth. The apple’s fall led him to think that the force acting on the apple might be the same force acting on the Moon. Newton believed that this force held the Moon in its orbit.

Newton also began to investigate light. Newton’s first experiments with a prism helped change the view that white light was simply white. Passing a beam of sunlight through a prism, he saw that the beam spread out into a colored band of light, called a spectrum. Newton concluded through experimentation that sunlight is a combination of all the colors of the spectrum and that the sunlight separates when passed through the prism because its colors bend differently.

His earlier experiments with the prism convinced him that a telescope is limited by the way different colored rays bend. Newton observed that lenses refract, or bend, different colors of light by a slightly different amount. He believed that these differences would make it impossible to bring a beam of white light (which includes all the different colors of light) together at a single point (focus). He turned his attention to building a reflecting telescope, or a telescope that uses mirrors instead of lenses, as a solution. Mirrors reflect all colors of light by the same amount.

Scottish mathematician James Gregory had proposed a design for a reflecting telescope in 1663, but Newton was the first scientist to build one. He built a reflecting telescope with a 1.3-in (3.3-cm) mirror in 1668. This telescope magnified objects about 40 times.

By 1679 Newton returned to the study of planetary orbits. Newton tried to combine his ideas about the attraction between two objects (like the apple being attracted to the earth) with German astronomer Johannes Kepler’s Third Law, which said the closer a planet comes to the sun, the faster it moves.

With the help of English astronomer Edmond Halley, Newton came up with his theory of gravity.

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