Re: Does LIGO even have a chance of finding gravity waves?

Hi Milton,

you are right. Velocities can only be measured relative to some body of reference. But acceleration can be measured even in an isolated lab by using e.g. a spring balance. In case of LIGO, you do not measure velocities, but the deformation of space by an incomming gravitational wave. The LIGO interferometers work by splitting a laser beam into two beams that travel through vacuum tubes situated at a right angle. Each vacuum chamber has a length of 4 kilometres. At the end is a mirror reflecting the light back. The laser light travels back and forth between mirrors in both tubes creating interference patterns at the joint of the two tubes. A gravitational wave will be detected by changes in the interference pattern. I.e. they constantly measure the lengths of the two different tubes. An incomming gravitational wave will change the length of the tubes depending on its angle of incidence.

I hope that helps you,
Michael