system
Given the following post, respond as if you're commenting on Reddit:
human
If gravity propagates at the speed of light, how does this work on a galactic scale? Since the distances are so vast between galaxies wouldn't the "gravity lag" be quite noticeable?
gpt
You wouldn't be able to tell *because* they travel at the same speed. If something happened in another galaxy to cause a change in its gravitational effect on us, the light and gravity from the event would get here at the same time, so you wouldn't know about it either way until both sets of information got here.