system
Given the following post, respond as if you're commenting on Reddit:
human
By guessing the rate of the Expansion of the universe, do we know how big the unobservable universe is?

So we are closer in size to the observable universe than the plank lentgh, but what about the unobservable universe.
gpt
We measure the size of the unobservable universe by measuring the curvature of the local universe. If it has zero curvature, the universe is flat and infinite. If it has negative curvature, it has a hyperbolic shape, and is also infinite. If it has positive curvature, it has a hyperspherical shape (like a sphere but in more dimensions), and we can use the curvature to work out the size of the universe.

Currently it really looks like the universe is very very flat, so it looks like it's infinite. Unfortunately, all measurements must have an uncertainty, which means that it's technically possible that the universe is finite in size - it's just that the curvature is so small that we can't actually see it.

Edit: For a flat universe, Ω=1. For a spherical universe, Ω>1. We have Ω=1.00±0.02. For Ω=0.98, the radius of curvature of the universe would be about 30 gigaparsecs, which is on the scale of the total size of the observable universe - although we've only observed galaxies up to about 4 Gpc, and only with tricky lensing techniques.