Anwser :: Gravity is a force of attraction that exists between any two masses, any two bodies, any two particles. Gravity is not just the attraction between objects and the Earth. It is an attraction that exists between all objects, everywhere in the universe. Sir Isaac Newton (1642 -- 1727) discovered that a force is required to change the speed or direction of movement of an object. He also realized that the force called "gravity" must make an apple fall from a tree, or humans and animals live on the surface of our spinning planet without being flung off. Furthermore, he deduced that gravity forces exist between all objects.

Newton's "law" of gravity is a mathematical description of the way bodies are observed to attract one another, based on many scientific experiments and observations. The gravitational equation says that the force of gravity is proportional to the product of the two masses (m1 and m2), and inversely proportional to the square of the distance (r) between their centers of mass. Mathematically speaking,

F=Gm1m2 / r2,

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The fundamental force of attraction that all objects with mass have for each other. Like the electromagnetic force, gravity has effectively infinite range and obeys the inverse-square law. At the atomic level, where masses are very small, the force of gravity is negligible, but for objects that have very large masses such as planets, stars, and galaxies, gravity is a predominant force, and it plays an important role in theories of the structure of the universe. Gravity is believed to be mediated by the graviton, although the graviton has yet to be isolated by experiment. Gravity is weaker than the strong force, the electromagnetic force, and the weak force. Also called gravitation. See more at acceleration, relativity.

The story of Isaac Newton discovering the laws of gravity by watching apples falling from a tree is probably just a myth. He did do his work on gravity while at a farm, but that is about as much as can be proven.

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Sir Isaac Newton developed his Theory of Universal Gravitation in the 1680s. He found that gravity acts on all matter and is a function of both mass and distance. Every object attracts every other object with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. The equation is often expressed as:

Fg = G (m1 ∙ m2) / r2

Fg is the gravitational force
m1 and m2 are the masses of the two objects
r is the distance between the two objects
G is the universal gravitational constant