Gravitation is a natural phenomenon that is described by the physical attraction between composites of matter. The theory of gravitation may be best described by Einstein's general theory of relativity, which states that gravity is due to the curvature of space-time.
While Sir Isaac Newton quantified gravity in his three laws of motion, Einstein posited a general theory of relativity. In his theory, Einstein deduced that massive bodies caused distortions in space-time by causing light to bend around that object. Einstein also observed that electromagnetic radiation is slightly stretched out inside a gravitational field; this can be demonstrated by the Doppler Effect, whereby the frequency of waves becomes greater to an observer, when the source is accelerating towards them, and less when accelerating away.