Gravitation

Gravitation, or gravity, is a fundamental force of nature that attracts two bodies with mass. It governs the motion of celestial bodies, influences tides, and is responsible for the structure of the universe. Isaac Newton formulated the law of universal gravitation, describing gravity as a force proportional to the product of the masses and inversely proportional to the square of the distance between them. Albert Einstein later refined this understanding with his general theory of relativity, which describes gravity as the curvature of spacetime caused by mass.
For more information, visit the Wikipedia entry on Gravitation.