system
Given the following post, respond as if you're commenting on Reddit:
human
The force of gravity decreases over distance, but does it ever stop?

For example, say there were two grains of sand floating in interstellar space, a light-year apart. If they were not being acted upon by outside forces, would they have a gravitational attraction to one another that would bring them together? And if so, does that mean that I'm currently being effected by the gravitational force of everything in the universe?
gpt
Yes, gravity never just stops propagating, but you do have to take the speed of light limit into account. There are regions of the Universe that are so far away that they've never had time to influence us gravitationally. However, if the Universe went through an early period of accelerated expansion called inflation, as we think it likely did, then the region which could have influenced us at one point or another is going to be significantly, many orders of magnitude, larger than the part of the Universe we can observe today.