Gravitation is a natural phenomenon by which objects with mass attract one anotherDoes Gravity Travel at the Speed of Light?, UCR Mathematics. 1998. Retrieved 3 July 2008. In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass. Gravitation compels dispersed matter to coalesce, thus it accounts for the very existence of the Earth, the Sun, and most of the macroscopic objects in the universe.

Modern physics describes gravitation using the general theory of relativity. Newton's law of universal gravitation provides an excellent approximation for most calculations.

The terms gravitation and gravity are mostly interchangeable in everyday use, but a distinction may be made in scientific usage. "Gravitation" is a general term describing the phenomenon responsible for keeping the Earth and the other planets in their orbits around the Sun; for keeping the Moon in its orbit around the Earth, for the formation of tides; for convection (by which hot fluids rise); for heating the interiors of forming stars and planets to very high temperatures; and for various other phenomena that we observe. "Gravity", on the other hand, is described as the theoretical force responsible for the apparent attraction between a mass and the Earth. In general relativity, gravitation is defined as the curvature of spacetime which governs the motion of inertial objects.

History of gravitational theory

main: History of gravitational theory

Early history

Efforts to understand gravity began in ancient times. Philosophers in ancient India explained the phenomenon from the 8th century BC.Dick Teresi (2002), Lost Discoveries: The Ancient Roots of Modern Science - from the Babylonians to the Maya, Simon & Schuster, New York, ISBN 0-684-83718-8:
quote: "Two hundred years before Pythagoras, philosophers in northern India had understood that gravitation held the solar system together, and that therefore the sun, the most massive object, had to be at its centre." According to Kanada, founder of the Vaisheshika school, "Weight causes falling; it is imperceptible and known by inference."

In the 4th century BC, the Greek philosopher Aristotle believed that there was no effect without a cause, and therefore no motion without a force. He hypothesized that everything tried to move towards its proper place in the crystalline spheres of the heavens, and that physical bodies fell toward the center of the Earth in proportion to their weight.