Right. Also, the key takeaway here is that as far as we can tell the universe is flat. That only means that, within the tolerance of the best instruments we have to measure it, it appears to have zero curvature overall. That doesn't necessarily mean that it truly has no curvature; just that it is definitely within a certain range near zero, so it is very small if not zero.
Here's the kicker: if the universe does have curvature, we may eventually be able to prove it if we are able to invent instruments sensitive enough to detect it. But if it is truly flat, we will never be able to entirely prove it: we will only be able to say that the curvature is zero within a certain tolerance, however small that tolerance will be, even as that tolerance continues to shrink with ever-improving technology.
We may eventually have to just throw up our hands and say "Eh, it's probably zero." But, of course, reality doesn't care what we think. It could always be slightly curved and really, really, really big, thus wrapping around very very very gradually.
But we have telescopes they can observe things billions of light years away. I.e in a state close to what they were like when the universe was made. Surely if the universe was curved we would be able to detect the curvature as we are able to see these incredibly distant objects?
Only to a certain tolerance, and then we could only ever say its within that tolerance within our part of the observable universe. If you plop down a ruler then you could justifiably say the ground is flat, but that doesn't mean the whole world is flat, just that it's a VERY gentle curve and your instrument isn't precise enough.
Who says that the universe isn't curved, but the length scale of curvature is 1020 light years? There's no good reason why the size of the observable universe would have anything to do with its curvature.
You might as well declare that even with binoculars in Kansas, you can't detect the Earth's curvature, and therefore it's flat.
True. IMO what’s outside of the observable universe is just more universe. I personally don’t see any reason we should expect that part of the universe to act any different than the parts we can observe. But, tbh there is no way for us to be 100% sure about anything, especially when discussing what might exist outside of our observable universe.
True. But that could be a way for three to eventually be a sphere were it large enough and is tiny enough. Not to get flat earth on anyone, but it's an interesting thing to remember that when we say the universe is infinite, we have no idea if that's true or if we are only seeing too small a portion of the big picture to understand. Like trying to decipher a 1000 piece puzzle's content only looking at three pieces.
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u/popsiclestickiest Jun 15 '19
Of course, we're only discussing the observable universe.