system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - How did we verify that gravity has a speed?

Gravity apparently travels at or near the speed of light, but how do we know that?
gpt
It was a theory that came out from general relativity. When people started to apply the new theory of general relativity on different mechanics to see if they could find a flaw it was discovered that the observed motions of Mercury were much closer to the calculations if you used the fact that gravity were limited to the speed of light. This was one of the first big observations that would help make general relativity accepted.