Gravity is a natural phenomenon by which all things with mass or energy—including planets, stars, galaxies, and even light—are attracted to one another. On Earth, gravity gives weight to physical objects, and the Moon's gravity causes the ocean tides.
Sir Isaac Newton's law of universal gravitation, published in 1687, was the first to mathematically describe gravity. Albert Einstein's theory of general relativity, published in 1915, provides a more accurate description of gravity as a consequence of the curvature of spacetime.
Gravity is one of the four fundamental forces of nature and is essential for understanding the structure and evolution of the universe, from the formation of stars and planets to the orbits of celestial bodies.