Gravitational wave

Gravitational waves are disturbances in the curvature of spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. They were predicted in 1916 by Albert Einstein on the basis of his general theory of relativity. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Observations of gravitational waves are used to infer data about their sources, such as binary white dwarfs, neutron stars and black holes; and supernovae, and the expansion of the universe after the Big Bang.

The Laser Interferometer Gravitational-Wave Observatory (LIGO) is a system of two observatories designed to detect cosmic gravitational waves by laser interferometry. These observatories use mirrors spaced four kilometers apart which are capable of detecting a change of less than one ten-thousandth the charge diameter of a proton.

LIGO also determined that the graviton (the hypothetical quantum of gravity) was the lightest particle known to nature, at 8.9×10−59 kg or 4.7×10−23eV/c2. Although these experiments cannot detect individual gravitons, they provide information about properties of the graviton. For example, if gravitational waves were observed to propagate slower than c (the speed of light in a vacuum), that would imply that the graviton has mass.

The detection of gravitational waves was first reported in 2016 by the LIGO Scientific Collaboration (LSC). Scientists involved in the project and the analysis of the data for gravitational-wave astronomy are organized by the LSC, together with over 500,000 active Einstein@Home users.

In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves".

As of December 2019, LIGO has made over 50 detections of gravitational waves from black hole mergers and neutron star mergers.

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