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Ojisan1 t1_jabhmis wrote

It’s like asking the question what’s at the edge of the earth? The answer is more earth. Just because you can’t see over the horizon doesn’t mean that’s all there is.

Similar with the universe - we can only see as far as light can travel in the amount of time since the universe began, just under 14 billion years. That’s like the horizon. But if you were able to magically teleport to 14 billion light years away from here, you’d still be able to see 14 billion light years in every direction. Similar to how if you teleported to the horizon on earth, you’d still just see the same distance to the horizon in every direction.

It’s more complicated because we are 3 dimensional beings in a 3 dimensional space, versus being 3 dimensional beings looking at the 2 dimensional surface of a sphere. If we were 4 dimensional beings, we could look at the 3D universe from a vantage point that would make it just as obvious that there’s no edge as it’s obvious to you that there’s no edge of a globe. But we aren’t 4 dimensional beings so we have to use analogies to understand without using math.

The way to understand expansion is that everything is getting further away from everything else. No matter where you are, everything else that exists is all moving away from you.

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iaintlyon t1_jabk6ga wrote

Hm. So is there a hypothetical shape of the universe?

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Ojisan1 t1_jabll0e wrote

That’s where it gets complicated. We don’t know because we can only observe 13.7 billion light years in every direction. So what we see is a sphere with us at the center. But there are some other things that suggest that the universe is a hypersphere or a hypertoroid.

It’s not possible for us to picture these objects except by approximation, or with math, or with analogies. But a short explanation: A sphere is a circle extended into an additional dimension. You can visualize that. A hypersphere is a sphere extended into an additional dimension. Can’t visualize it, but that’s what it means.

A torus is a donut shape, so a hypertoroid is a donut extended into an additional dimension.

There are videos about hypercubes, and hyperspheres, which attempt to help picture what it’s like, but because our minds operate in 3 dimensions, it’s not capable of truly comprehending these 4 dimensional objects.

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