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Gravitational Waves IV

January 26, 2012

SCOFIELD: We’re on the roof of the corner station at Hanford, looking out across the desert. This desert was set aside for production of plutonium in World War II, so this is the Hanford Nuclear Reservation. Since each of our arms is two-and-a-half miles long, it makes sense to site such a big facility out here in this protected desert.

Robert Scofield is a scientist with LIGO — a gravitational wave observatory with detectors at Hanford, Washington, and Livingston, Louisiana. Each detector consists of a pair of “arms” in which a laser measures the distance to a mirror that’s two-and-a-half miles away. Passing gravitational waves — “ripples” in spacetime created by the motions of massive objects such as pairs of “dead” stars that are merging — would cause the distance from the laser to the mirrors to change — by about one-ten-thousandth of the width of a proton.

But lots of things right here on Earth can cause the laser and mirrors to “jiggle,” changing the distance between them: earthquakes, construction, passing trucks, and, in Hanford, the whirring fans of cooling towers at a nearby nuclear power plant. And LIGO is being upgraded to make it more sensitive, which will only amplify the noisy environment.

To insulate them from that environment, the detectors are sealed in vacuum chambers, and sit on floors that are isolated from the buildings around them. Springs dampen the jiggling of earthquakes.

More tomorrow.


Script by Damond Benningfield, Copyright 2011


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