Isaac Newton was a famous scientist and mathematician from England who lived long ago, and he was born in the manor house at Woolsthorpe, in England, where his family were farmers. At school, Newton's reports called him idle and inattentive, and his mother took him out of school to run the family farm. He returned to school and went on to university. He went to Trinity College, part of Cambridge University, where he studied the work of Johannes Kepler, René Descartes and other giants of the Scientific Revolution. As a student he wrote in a notebook, in Latin, 'Plato is my friend, Aristotle is my friend, but my best friend is truth.' According to de Moivre, Newton's interest in mathematics began in 1663, when he bought an astrology book at a fair in Cambridge and could not understand its mathematics.

Then a sickness called the plague closed Cambridge University, so Newton went home to Woolsthorpe. While away from Cambridge because of the plague, Newton began important work in mathematics, light, physics and astronomy in less than two years. Every scientist since Aristotle had believed white light was a single basic thing, but Newton shone sunlight through a glass prism and saw a band of colors. He split white light into colors with one prism, then used a second prism to join the colors back into white light. In a key experiment, Newton passed one color from the spectrum through a hole and a second prism, and the second prism bent it by the same amount without changing its color. The experiment showed that each color is a pure part of white light. White light is made of all the colors of the rainbow, as Newton showed.

Newton explained the color of an object as the colors it reflects after it absorbs all the others, and he named seven colors in the spectrum, admitting that choosing seven was rather arbitrary. Newton reasoned that lens telescopes would always blur colors, and so built a reflecting telescope, though MacTutor calls that conclusion erroneous. A mirror reflects all colors of light by the same amount, so a mirror telescope fixes this. Others, such as James Gregory in 1663, had described ideas for a reflecting telescope, but Newton was the first to build one. His used a mirror to gather light and a second mirror to send it to an eyepiece, and the first one he built was only about six inches long.

As of November 2026, reflecting telescopes, which use mirrors as Newton's did, are mainstays of astronomy, including the Hubble Space Telescope. Newton was elected a Fellow of the Royal Society in 1672. His first scientific paper, 'New Theory About Light and Colours,' appeared in the Philosophical Transactions of the Royal Society in March 1672, after the Royal Society asked for a written account of his telescope. Robert Hooke and Christiaan Huygens objected to Newton trying to prove by experiment alone that light is made of small particles rather than waves. His Opticks appeared in 1704. It covered the theory of light and color, the colors of thin sheets known as Newton's rings, and diffraction of light. Newton measured the colored rings made when a lens is pressed against flat glass, and the gap between lens and glass grows evenly with each ring.

John Conduitt, who worked with Newton at the Mint, wrote that in 1666 Newton, musing in a garden, thought gravity might reach as far as the Moon. Newton did tell a story about watching an apple fall from a tree. No one knows for sure if an apple really fell the way the story says, and the part where it hits him on the head is called a myth. Newton said that everything pulls on everything else, and he called this pull gravity. In 1666 he imagined that the Earth's gravity reached the Moon, balancing the Moon's outward push. Gravity does not give the Moon its speed, but it stops the Moon from running away and keeps it in some orbit. Newton's law of universal gravitation says all matter attracts all other matter.

In 1684 Edmond Halley asked Newton what orbit a body follows under an inverse-square force. Newton replied at once that it would be an ellipse. Halley persuaded Newton to write out his new physics in full. The result, the Principia, was published in 1687, and Halley paid to have it printed. Newton wrote a famous book about how things move, and a mathematician at the Open University wrote that it made him famous even though few people read it and even fewer understood it. In the Principia, Newton applied his laws to orbiting bodies, projectiles, pendulums and free-fall near the Earth, and it explained the eccentric orbits of comets, the tides and their variations, the wobble of the Earth's axis, and the Moon's motion as pulled by the Sun's gravity.

Before Newton, thinkers assigned different causes to different types of motion, according to physicist Stephen Hawking. By unifying all motion, Newton shifted science toward a search for large, unifying patterns in nature. Scientists on the European continent did not accept Newton's idea of action at a distance. They kept to Descartes's vortex theory, in which forces work through contact. In 1669 Newton became the Lucasian Professor at Cambridge, and he was the second person to hold the professorship. At Cambridge, Newton showed little interest in teaching, and his lectures were sparsely attended. Sometimes no one showed up at all. He became Warden of the Royal Mint in 1696 and Master of the Mint in 1699, a post he kept until his death in 1727, and he helped take old coins out of use and replace them with more reliable ones.

In 1703 Newton was elected President of the Royal Society, a group of scientists, and Queen Anne made him a knight in 1705. He lived to be 84 years old. He is buried in Westminster Abbey in London, where his monument was finished in August 1730 and unveiled the following year. The carved scene on the monument shows figures with a telescope, a prism, and a balance weighing the Sun and planets. Newton's laws are still used to reach the Moon, Mars and other places beyond Earth. Newton famously said that if he saw farther than others, it was because he stood on the shoulders of giants. Near the end of his life he said he felt like a boy on the seashore, finding a smoother pebble or prettier shell while the great ocean of truth lay undiscovered.

Words to know

• spectrum: band of colors
• ellipse: stretched circle
• diffraction: light bending around
• erroneous: mistaken
• orbit: path around something