gravitational waves


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gravitational waves

(gravitational radiation) Extremely weak wavelike disturbances that were predicted by Einstein's general theory of relativity. They represent the radiation associated with the gravitational force, and are produced when massive bodies are accelerated or otherwise disturbed. They are ripples in the fabric of spacetime that travel at the speed of light, with a wide range of frequencies, and carry energy away from the source. They should affect all matter: gravitational waves hitting a suspended body, for example, should make it vibrate slightly. The interactions are very small, however.

No conclusive direct evidence of the existence of gravitational waves has been forthcoming from the various highly sensitive experiments designed to detect them. Laser interferometers could be sufficiently sensitive. They consist of two identical extremely long tubes, set at right angles and with mirrors at both ends. A laser beam is split and sent down the tubes. A relative change in the two lengths would indicate a passing gravitational wave, and would be seen in the interference patterns produced when the reflected beams are recombined.

Gravitational waves should be emitted during supernova explosions or energetic events in the cores of active galaxies. They should also be emitted by two massive stars in close orbit. Recent observations of the binary pulsar PSR 1913+16 show that its orbital period is decreasing by 76 ± 2 microseconds per year. The observed value corresponds almost exactly with the decrease predicted to result from the emission of gravitational waves (75 μs per year) and is at present the best indirect evidence for their existence.

A quantum of gravitational radiation is known as a graviton, analogous to a photon.

References in periodicals archive ?
Camille Carlisle replies: I suppose we could say that both electromagnetic and gravitational waves travel at the maximum speed possible in spacetime: 300,000 kilometers (186,000 miles) per second.
Gravitational waves are the distortions in space-time that are caused by the most powerful space events and objects.
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Last year we saw the historic first detection of gravitational waves culminating in international researchers being awarded the 2017 Nobel Prize in Physics.
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Neutron star mergers, witnessed via both gravitational waves and light, "could be the tiebreaker," said Brandeis University astrophysicist Marcelle Soares-Santos.
When the neutron stars collided a flash of light in the form of gamma rays was emitted and seen by satellites orbiting the Earth about two seconds after the gravitational waves.
Until August, all detected sources of gravitational waves had been black hole mergers.
This is a source we always thought we would see," said David Reitze, Executive Director of the Laser Interferometer Gravitational-Wave Observatory (LIGO), which detected the cosmic ripples called gravitational waves, speaking at a news conference.
US scientists Rainer Weiss, Barry Barish and Kip Thorne won the 2017 NobelPrize for Physics for their pioneering role in the detection of gravitational waves, prize organisers said on Tuesday.
Scientists have successfully detected gravitational waves from space for the fourth time.
Ripples in Spacetime: Einstein, Gravitational Waves, and the Future of Astronomy