system
Given the following post, respond as if you're commenting on Reddit:
human
What experiment shows that gravity travels at the speed of light?

I've seen it mentioned on this forum that gravity travels at c, but I'm not sure how anyone could set up an experiment to confirm that. Do we have experimental evidence, or is it more of a "well, according to our theories, it should behave this way" kind of thing?
gpt
Gravitational waves have yet to be experimentally observed, but the purpose of experiments that are attempting to do so (such as LIGO) is to use these waves as telescopes, not as confirmations of General Relativity.  General Relativity has been confirmed in many other ways by many other experiments, and also happens to predict gravitational waves propagating at speed c.  Given its extraordinary previous predictive success, there is not reason to believe that it is wrong in this instance.