Einstein published the general theory of relativity in 1915-1916. There is one postulate of general theory of relativity. The relativity postulate is gravitation is equivalent to acceleration where gravity does not depend on the properties of matter rather gravity must take place from the properties of space-time. Gravitational mass of a body is equal to its inertia mass. Newton’s law of motion:
(Force) = (inertial mass) Х (acceleration)
The “inertial mass” is a characteristic constant of the accelerated body. If now gravitation is the cause of the acceleration:
(Force) = (gravitational mass) X (intensity of the gravitational field)
The “gravitational mass” is a characteristic constant for the body. Therefore:
(acceleration) = (gravitational mass) X (intensity of the gravitational field)
(inertial mass)
Einstein used his famous “thought experiment” to explain the relationship between gravity and space-time. The general theory of relativity has been described as, “matter tells space-time how to curve, and curved space-time tells matter how to move.” Einstein has gravitational field equations that describe mathematically how space-time is curved by matter and energy.