Where does the force of gravity come from?
Gravity is a force of attraction between two masses. For us to detect the effects of gravity one of the masses must be very large indeed – typically the mass must be that of a planet(oid) (10^23 kg) or that of a star (10^30 kg). Newton’s theory of universal gravitation relates the force of attraction and the masses, with the expression: – F = G.M.m …….——– ………r^2 Where ‘F’ is the force in Newton’s theory with ‘M’ the mass of the large body, ‘m’ the ‘probe’ object’s mass with ‘r’ as the separation between their centre points and ‘G’ is Newton’s universal gravitational constant. In Newton’s theory of gravity, all of the mass is concentrated at a central point. Unfortunately, Newton did not give us an account of exactly what gravity was only that it was a property of mass and was attractive in nature. However, in 1915 Albert Einstein published ‘The Foundation of the General Theory of Relativity’ in which he described gravity as the distortion of space-time by the presence of
