“As I understand it, the lasers are used to measure the distance between a number of separated masses. As a gravitational wave passes by, it will induce motion in them. Even with "arms" 4 kilometers long, the strongest gravitational waves will only change the distance between the ends of the arms by at most roughly 10 to the minus 18th meters...so the lasers have to be really accurate!” [excerpt]Ok, so the gravity effects the 'arms', and then the laser interferometers measure how much the 'arms' have been effected?
Ditto.