Portrait of Newton by Godfrey Kneller (1689).

Sir Isaac Newton was a mathematician and physicist whose brilliance helped launch an age of scientific exploration. Newton had a harsh early life. He was born in Woolsthorpe, England, as a tiny, premature baby who surprised everyone by surviving. His father, a farmer, died just before Newton was born. At age 3, he was separated from his mother, who left him with his grandparents in order to remarry. The family, including half-siblings and Newton’s grandmother, all moved in together after the death of Newton’s stepfather.

In 1661, Newton went to Cambridge University, the place where he would spend a good portion of his life. He helped pay for his tuition by working as a servant to other students. He began to work on a law degree, but quickly became interested in geometry, seeking out and studying major books of mathematics on his own.

In 1665, an outbreak of the bubonic plague ravaged England, killing thousands of people. The University closed and Newton returned home, where he began some of his tremendous works in the fields of mathematics, optics, physics and astronomy. He worked out principles and techniques for what would become calculus, established his ideas about the way light and color worked, and theorized about the motions of the planets.

Two years later, Newton went back to Cambridge. In 1669, at only 27 years old, he became a professor. He began that career by explaining that white light is made up of colors — a strange idea at the time. This concept led him to produce the first reflecting telescope, since he had concluded that the lenses used in refracting telescopes would always produce a distorted image as their lenses separated white light into colors. His presentation of the reflecting telescope to the major scientific organization of the time, the Royal Society, made him known in scientific circles.

Newton suffered occasional emotional breakdowns during his life, and was known for his temper. Early conflicts with other scientific figures of the time seemed to make him reluctant to publish or share his discoveries. His work on gravity was released after the astronomer Edmund Halley visited him with a question about the motion of planets that was confounding astronomers, and found to his shock that Newton had worked out the answer four years earlier and simply kept it to himself.

Newton, urged by Halley to publish his work, spent the next two years refining his ideas about planetary motion and in 1686 produced the “Philosophiae Naturalis Principia Mathematica,” or Mathematical Principals of Natural Philosophy. The Principia explained how gravity was a force that applied to all objects in the universe. Many people consider it the most important book in the history of science.