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 ?
Among the anticipated sources of gravitational waves are supernova explosions and double black holes.
Scientists hope the $450-million LISA Pathfinder mission will demonstrate it's possible to shield objects from external influences well enough to detect the minute effects of gravitational waves.
When the gravitational waves rolling in from space are detected on Earth for the first time, a team of Northwestern University astrophysicists predicts astronomers will "hear," through these waves, five times more colliding black holes than previously expected.
It should be observed that if we examine this question from a quantum mechanical perspective we are inevitably struck by the fact that the role of Planck's constant in gravitational wave phenomena has always been taken for granted without questions regarding the possible limits of its applicability being asked, which is somewhat perplexing since no purely gravitational measurement of Planck's constant exists.
Although the ejection of a supermassive black hole from a galaxy by recoil because more gravitational waves are being emitted in one direction than another is likely to be rare, it nevertheless could mean that there are many giant black holes roaming undetected out in the vast spaces between galaxies.
There was a general consensus that gravity might exist in the form of gravitational waves and that these waves could be a part of “what we've been calling, empty space.
They cover a brief review of general relativity, gravitational waves, beyond the Newtonian limit, sources of gravitational radiation, gravitational-wave detectors, analyzing gravitational-wave data, and gravitational-wave astronomy and astrophysics.
The authors note the ultimate proof of the merger model will have to await the detection of gravitational waves -- ripples in the fabric of space-time predicted by relativity.
It is also thought the strange twins could emit mysterious gravitational waves.
Topics examined include the H1 distribution of the Milky Way; progenitors of core-collapse supernovae; gravitational waves from merging compact binaries; physical properties and environments of nearby galaxies; hot subdwarf stars; high-contrast observations in optical and infrared astronomy; magnetic reconnection in astrophysical and laboratory plasmas; magnetic fields of nondegenerate stars; star-formation histories, abundances, and kinematics of dwarf galaxies in the local group; complex organic interstellar molecules; the chemical composition of the sun; teraelectronvolt astronomy; and the study of gamma-ray bursts in the era of the Swift satellite.
GLASGOW University professor Sheila Rowan is at the cutting edge of science, leading the hunt to prove the existence of gravitational waves.