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 Originally Posted by MIKEovMANTON
Cool thread.
Keep that in mind as I'm about to pick on your choice of words. (Note that I'm not picking on you, just the sentences.)
Originally Posted by MIKEovMANTON
Where is the centre of the universe?
I don't even know if this is a reasonable question. Where is the center of the surface of the Earth?
Originally Posted by MIKEovMANTON
Science tells us that anywhere can be considered the centre
No, I have to stop you there. Science tells us a procedure to answer a very specific category of questions, those with measurable answers. Science doesn't tell us anything about the universe. Science tells us how to check if someone's claims about the universe are in line with our own observations.
Scientists tell us about the universe. Science tells us how to evaluate those claims made by scientists. Science makes no claims (other than the implicit claim that science itself is a viable process); science provides a system by which claims are verified or refuted.
Originally Posted by MIKEovMANTON
anywhere can be considered the centre, but that makes absolutely no sense. If the Earth is at the centre and the CMB is at the edge (of the visible universe at least) and I travelled 1billion light years towards the CMB, I would surely not still be able to class myself as being at the centre of the universe? or would I?
Yeah. I agree it makes no sense. It's difficult to imagine anything outside of space-time. Nonetheless, space-time is expanding. Does that mean that there is something besides space-time that space-time is expanding into? I don't know. Physics does not answer questions about unobserved things.
The CMB is not stationary, it is the photonic residue from when electrons transitioned from one spin state to another during the ridiculously early universe. Photons are light, and they travel at the speed of light. The CMB is expanding outwardly away from you at the speed of light. No conceivable travel you could do for any amount of time would change the fact that the CMB makes a sphere around you. No matter what you do, you will never be any closer to the CMB; it will always be receding away at the speed of light, and you can't go that fast.
More fundamentally, we have observed a miniscule fraction of the universe, both in scope and in duration, and we just don't know how to answer a question like "Where is the center of the universe?" We don't know the fundamental topology of the universe, so we don't know what "shape" space-time is. We don't know how many dimensions it truly needs to appear as it does to us in 3 spacial dimensions and 1 time dimension.
What if the universe as we perceive it is really the surface or a projection of some many-dimensional form? The notion of a center is meaningless, then.
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Why does the idea of the center of the universe fascinate us? It seems to me that it would be just like any other part of the universe.
I think scientists think they're clever when they say the center is everywhere. I understand the logic. Big bang = everything is one place (never mind that no one knows what that really means), so if everything was in one place... and it's not everything that moved, but the place that grew... then everything exists exactly where it did in the beginning, and it's merely the growth of space-time that made the universe bigger. So everything is right where it started, which is the center.
I mean... come on, right? I find that a less comfortable answer than... well, we're too ignorant as a species to answer that question or even know if it's a reasonable question. Is it that hard to say "I don't know."?
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Once again, please don't let my harsh treatment of this question put you off. It's a borderline-physics question, and it's one that I can't easily answer or explain why I can't answer or say "that's not physics"... it's a tough one, and a good one for all of those reasons.
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