# Does inflation theory assume a finite universe?

Inflation theory has it that the early universe was causally connected, and could “mix”, hence explaining relative homogeneity of the CMB. The universe then rapidly expanded and became causally disconnected as it is now.

Now, when I picture the Big Bang, I picture a coordinate grid appearing out of nowhere, and the universe “expanding” is simply the act of “zooming” into the grid. The grid is obviously infinite in this case, and hence I cannot see why one point can be “causally” connected to another point arbitrarily far from it (since even the early universe was infinite).

To me then, inflation theory seems to assume that the early universe (and the universe as it is now, for that matter) was finite, and hence could be causally connected, before rapidly expanding to the way it is now.

I don’t think my thought process is right here, so it would be appreciated if anyone can correct my misconceptions.

• I don't think we need to assume that points in the early universe arbitrarily far away from each other are causally connected. I think inflation just enables causal connection in the early universe between points that would be unconnected if the universe had always expanded at a uniform rate. Commented Nov 19, 2023 at 10:04
• @gandalf61 isn’t inflation supposed to solve how the entire CMB ia homogenous? So wouldn’t that mean the entire universe? Commented Nov 19, 2023 at 16:29
• The entire visible universe. Two points that we see in the CMB in opposite directions from us were a finite distance apart when the CMB formed - they were never arbitrarily far away from each other. Commented Nov 19, 2023 at 16:57
• Ah that makes more sense. Commented Nov 19, 2023 at 17:00