The title of the post is a bit provocative on purpose.
I’d like to help better visualize why it appears we are at the center - as in why is everything moving away from us. Why is the universe a sphere around our specific position?
This can be visualized with a simple question:
What is the center of the surface of a sphere?
You will find that no matter where you put a point on a sphere - it will always appear to be at center of the surface from it’s perspective. All other points will always curve away from it. If you are confused as to what I mean by ‘center’, imagine the center of a hemisphere.
A equivalent experience is that ours on earth. Every person has their own independent ‘up’. The difference in the angle of ‘up’ is dependent on the distance they are from you on the earth.
Notice also that this effect is relative - simply meaning that from the other persons perspective, your ‘up’ is also increasingly wrong the further you are from them.
This ‘centering’ is of course an illusion brought about by the fact that the surface is curved.
Our universe is made up of spacetime that is curved in a similar way.
Instead of experiencing the surface drop away from us like on the sphere, we experience this curvature in spacetime as expansion.
Every point in the universe appears to be at the center, with all other points accelerating away from it. The rate of expansion is dependent on the distance away from the point.
This inverse of a sphere is hyperbolic space. Instead of points converging at a pole, they diverge.
Small note on expansion
Keep in mind, objects in the universe aren’t actually all moving away from each other. Spacetime itself - the underlying ‘grid’ - is expanding.
It’s like drawing two points on fabric and then stretching the fabric itself.
This is an illusion of curvature in spacetime, just like standing on a sphere. The surface of a sphere doesn’t have a center, and neither does the universe. Every point is the center, because there isn’t one.
Consideration
Because of Causality limiting the speed of light, it is impossible to know whether the universe is infinite or not. There is a horizon where the expansion is faster than the speed of light, so we can never know what is beyond.
But if we assume that expansion is a result of curvature, then we know it can’t be infinite - and we also know that it can’t have an edge (by definition it’s the universe - nothing could be beyond the edge) - so we know that it must loop around, kind of like a sphere does.
This effect is again relative. Every part of the universe experiences the same phenomenon - everything else rapidly accelerating away from it - in the same way any point on a sphere will see the ground dropping away. Something at the far edge of your universe will see you at the far edge of theirs.
Everything is expanding away from Everything because of hyperbolic curvature, and we are at a center that doesn’t exist. The center is everywhere and nowhere at the same time.
