Hi, First: I'm pretty sure my question has been asked numerous times, so I'm absolutely happy with links to other threads. I've used search but it didn't come up with satisfying responses, probably mainly because I don't really know what search terms to use. So the question is: How can a Michelson-interferometer-like device detect gravitational waves based on the change of length differences between the arms? How are changes in length detectable if space itself is distorted? The length of a ruler along an arm changes as well, so why doesn't it take the light exactly the same time?