Gravitational waves are distortions in space travel at the speed of light away from a mass that moves. Predicted by Albert Einstein's Theory of Relativity in 1916, and at one time the subject of a hoax, gravitational waves have never been observed until 2015, when the first evidence of their existence was confirmed.
Gravitational waves are essentially "ripples", similar to the ripples made in a pond when a pebble is tossed in, but on a cosmological scale. The mass in question are binary systems - pulsars, neutron stars, or black holes - which orbit around each other. According to Einstein's General Theory of Relativity and his formula E=mc2, both objects emit gravitational waves while losing energy as they gradually approach, eventually resulting in a collision at one-half the speed of light, forming a single object as well as emitting a final, very strong burst of gravitational waves
As part of his relativity theory, Einstein came up with his "quadrupole formula", which describes the rate of wave emmissions from a system of astronomical masses based on the change of the mass itself, what he called the "quadrupole moment". His formula as originally postulated was
- gravitational wave, and mass quadrupole moment.
The results of his findings were published in 1916 as Näherungsweise Integration der Feldgleichungen der Gravitation ("Approximate Integration of the Field Equations of Gravitation"), but serious errors led him to a revision, published in 1918 as Über Gravitationswellen ("About Gravitational Waves").
- Einstein, Albert. "Näherungsweise Integration der Feldgleichungen der Gravitation"; Proceedings of the Royal Prussian Academy of Sciences (1916), Berlin, Germany.
- Einstein, Albert. "Über Gravitationswellen"; Proceedings of the Royal Prussian Academy of Sciences (1918), Berlin, Germany.