The gravitational constant, symbolized G , is a physical constant that appears in the equation for Newton's law of gravitation. Sir Isaac Newton (1642-1727), the English mathematician, quantified the behavior of the force of gravity . He noticed that the gravitational force between two objects is proportional to the product of their mass es, and inversely proportional to the square of the distance between their centers.
According to Newton's law , given any two objects having mass m 1 and m 2 (in kilogram s) whose centers of mass are separated by a distance r (in meter s), there exists an attractive gravitational force F (in newton s) between the objects, such that:
F = Gm 1 m 2 / r 2
The value of G in this equation is approximately equal to 6.67 x 10 -11 newton meters squared per kilogram squared (N x m 2 x kg -2 ). This constant is uniform throughout the Solar System, and apparently throughout our galaxy and other galaxies in its vicinity.
Some astronomers believe that if the universe is expanding as the popular Big Bang theory suggests, the value of G is gradually decreasing.
Also see the Table of Physical Units and Constants.