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Gravitational Wave Detection Imminent?
Seumas Hyslop writes "The UK Telegraph is reporting that we may finally have equipment that are sensitive enough to measure gravitational waves, which are incredibly small and have evaded detection despite the theories that they are present as a way of explaining gravitational effects. Basically, a laser beam is split into two branches that are sent down two identical 2000 feet long tubes and back again via mirrors. Assuming the two arms remain exactly the same distance, they will cancel each other out. But the scientists think that the beams will interfere with each other owing to the effect of gravity, meaning the length of the branches is altered and a gravitational wave has been detected."
It sounds as if the system is set up to detect gravity waves by detecting microscopic changes in the distances between two mirrors and a third object. Yes?
Aren't there be lots of things that could cause a microscopic motion of one of the mirrors? (Sound? Seismic activity? Changes in temperature? The ground settling underneath the structure that supports a mirror?) How do you construct the apparatus to make sure that either (a) the mirrors move only if affected by a gravity wave, or (b) any motion due to another cause is clearly distinguishable?