A gravitational wave moves at the speed of light. So if you compare arrival times from several widely-spaced detectors, you can get a pretty good idea of what d

A gravitational wave moves at the speed of light. So if you compare arrival times from several widely-spaced detectors, you can get a pretty good idea of what direction the wave came from. Even a single detector has two arms at 90 degrees to each other, which can give you a rough idea of where in the sky it came from. But now that we have multiple detectors online we get better and better about spotting the origin.