system
Given the following post, respond as if you're commenting on Reddit:
human
Does the force of gravity extend over an infinite distance (only becoming infitesimilally small with large distances) or is there a distance after gravity has no influence?

Basically I'm asking whether there is a fundamental 'unit' to gravity at which point the force cannot get any smaller without ceasing to exist at all (quantization I guess).

And is this true of the other forces too, magnetism, strong and weak nuclear forces?

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*Edit: Thanks all, there have been some truly mind expanding answers in here and certainly a lot to chew over.*
gpt
Not... quite. See, the deal is that gravity stems from General Relativity. We solve the equations of GR around a massive body (like the sun) but we do so by assuming the sun is the only thing in the entire universe. And we get a curvature of space-time; this curved space-time gives rise to the effects we commonly call "gravity," as in Newtonian Gravitational Attraction (with some slight modifications that are very important, but that's a different discussion). 

**But** let's go back to that initial "sun is the only thing" assumption. Clearly it's not. But the same kinds of solution seems to work on the scale of galaxies, and even clusters of galaxies. This is why the Andromeda and Milky Way galaxies are gravitationally attracted to each other and going to collide eventually. 

But what happens when we look on the very very large scales, cosmological scales; scales where galaxies are just little point masses (approximately). Well on these scales the universe is approximately uniformly dense (at a very very low mass density). And we solve GR here, and we find not gravitation, but the metric expansion of space. 

So on local (galaxy clusters and smaller) scales, GR generally solves for gravitation. And on Cosmological scales, GR solves for metric expansion. Does this mean that gravity doesn't "stretch" across the voids between galaxy clusters? Not exactly, it's just not the gravity you're familiar with; it's highly modified by the vast integrated volumes of dark energy between them.