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Gravitational Waves III

January 25, 2012

Almost everything that moves produces ripples in space and time known as gravitational waves. Most of them are tiny — like the ripples produced by a mosquito landing on Lake Michigan — far too tiny to detect. The biggest ripples — like those produced by splashing boulders — come from some of the heaviest and fastest objects in the universe, like merging stellar corpses — and those are the ones that scientists are trying to detect.

RAAB: We’re looking for warpages in space that are traveling at the speed of light and are generated by big violent motions like the formation of a black hole from the merger of two neutron stars.

Fred Raab is the supervisor of a gravitational-wave detector at Hanford, Washington. Along with a second detector in Louisiana, they form LIGO — the Laser Interferometer Gravitational Wave Observatory.

Each detector measures the distance from a laser light source to a mirror that’s four kilometers away. Each detector has a pair of these laser “arms” set at right angles to each other. If a gravitational wave passes by, it’ll cause a tiny change in the length of the detector arms. David Reitze is the head of the LIGO scientific collaboration:

REITZE: When a gravitational wave passes, what it will do is, it will alternatively stretch and compress each arm of the interferometer differentially, so while one arm is compressing, the other arm is stretching.

The effect is tiny and subtle, though, so it can get lost in the rumbling and jiggling of the detectors themselves. More about that tomorrow.


Script by Damond Benningfield, Copyright 2011


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