# Did Isaac Newton Really Discover The Law Of Gravitation When An Apple Fell From A Tree And Hit Him On The Head?

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Historians have confirmed that the story of the apple is true. In 1665 British physicist (a scientist specializing in the study of matter, energy, and their interactions) Isaac Newton (1642–1727) discovered the law of gravitation, the force that holds in place all objects in the universe (also called universal gravitation), after an apple hit him on the head while he was sitting under a tree. The legendary incident took place when he was visiting his family's farm in Woolsthorpe, England, after graduating from Cambridge University. This simple experience led him to groundbreaking ideas on gravitation. (Gravitation is commonly called gravity, but gravitation is the correct term because it describes the force that operates throughout the universe. Gravity refers only to the Earth's gravitational force.) He theorized that the apple had fallen because matter (anything that has mass, or form, and occupies space) attracts other matter. He then theorized that the speed of the apple's fall was directly related to the force that the Earth exerted upon it. Newton expanded this insight to theorize that the same force that had pulled the apple down from the tree was responsible for keeping the Moon, planets, and other heavenly bodies in their orbits (paths).

Newton is recognized as one of the greatest scientists the world has ever known. He made contributions to the fields of mathematics, physics, and astronomy (the study of stars, planets, and heavenly bodies). After developing his theories on gravitation he turned his attention to experiments with light. In 1704 he discovered that light is made up of particles. He combined this realization with his theories of gravitation to develop the most comprehensive analysis of gravitation and motion on Earth and throughout the universe. He expanded on the study of motion conducted by Italian astronomer Galileo Galilei (1564–1642), developing three basic laws of motion. The first states that when a body is at rest it tends to remain at rest. Conversely, when a body is in motion it tends to remain in motion, moving in the same direction unless acted upon by an outside force. Newton's second law states that the force that moves a body is equal to the body's mass (measurement of amount of matter) multiplied by the rate of acceleration (increase in speed). This law is expressed as the mathematical formula F= MA; F is force, M is mass, and A is acceleration. The third law states that for every action there is an equal and opposite reaction. These laws led Newton to calculate the gravitational force between the Earth and the Moon. He also is noted for his construction of a reflecting telescope (1668), his contributions to the development of calculus, and his experiments with genealogy (study of family descent), alchemy (chemical science), and historical chronology.

**Further Information:** Hitzeroth, Deborah, and Sharon Leon. *The Importance of Sir Isaac Newton.* San Diego, Calf.: Lucent Books, 1994. "Sir Isaac Newton." *Electric Library.* [Online] Available http://www.encyclopedia.com/articles/09202.html, November 8, 2000; "Sir Isaac Newton." *MSN Encarta.* [Online] Available http://encarta.msn.com/index/conciseindex/57/057 ED000.htm, November 8, 2000; White, Michael. *Sir Isaac Newton: Discovering Laws that Govern the Universe.* Woodbridge, Conn.: Blackbirch Press, 1999.