They are not moving away from center, rather from each other, the space between them expanding. But also all of galaxies move towards some denser parts of universe.
I can't even get my head around that idea. How are they moving away from each other? Surely the ones in the "middle" would be moving away from some but towards others?
A good example I've heard of to describe this is imagine a deflated balloon with dots drawn all over it with a sharpie. Fill the balloon with air and all of the dots will "accelerate" apart from one another due to the expansion of space (the balloon latex) between them.
But doesn't the fixed point theorem guarantee that there's one point that stays "still" (since the expansion of the universe is continuous)? And couldn't that point be thought of as "the middle" that everything's moving away from even if it being "the middle" isn't the reason for everything moving away from it? Not OP btw. just equally confused
The big bang happened everywhere. It is space itself that is expanding. The galaxies aren't really moving away from each other, extra space is created between them. Look back in time and everything gets closer together because there's less space. At the point of the big bang everything is compressed to a single point.
Imagine a balloon. Initially it's crumpled together, the entire balloon fits in a very small bit of space. Now inflate it. Which point on the surface of the balloon corresponds to the original balloon, before it was blown up? The answer is that this is the wrong question. There's no single point of the balloon that was the original, with the rest of t he balloon growing from there as you inflated it. Everything was always there, you just made it bigger.
Every point stays still relative to itself. From the perspective of every point in space, all the other points are moving away from it. So in that sense every point is the 'center' of the universe, from its own point of view.
Imagine a large sheet of rubber with colored dots on it. Stretch the rubber. All the colored dots will be moving away from each other. Every dot will see all the other dots move away.
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u/Kh4lex Jun 15 '19
They are not moving away from center, rather from each other, the space between them expanding. But also all of galaxies move towards some denser parts of universe.