Katie MackIf you ever get awed and overwhelmed by the incomprehensible vastness of space, just keep in mind that it’s expanding, more rapidly minute by minute, and to the best of our understanding it will never ever stop
CharlieG@AstroKatie Is it possible to say where we are in terms of the centre of the universe? Presumably at the centre of the *observable* universe, but overall?
@Charles We have no reason to believe there is a center
sbi@AstroKatie @Charles That is confusing, to say the least. In my common reference frame, every expansion can be reversed (at least in a thought experiment), and then leads to a center which things expand from.
I absolutely hear you saying this isn't true for space, but I utterly fail to wrap my head around something that so thoroughly contradicts my everyday experience.
I absolutely hear you saying this isn't true for space, but I utterly fail to wrap my head around something that so thoroughly contradicts my everyday experience.
Pierre Massé@sbi @AstroKatie @Charles imagine you're a 2D person living on the surface of a balloon and someone's blowing up that balloon. your universe is expanding, you can observe it doing so, but that doesn't help you define the "centre" of the spherical surface that is your universe ('cause there isn't one). the balloon has a centre, sure, but it's also got one more dimension than you.
so we might be living on the 3D surface of a 4D torus, if that helps.
@pierrotechnique @AstroKatie @Charles I know the balloon parable, and while it helped me to understand that every place feels like it's the center of the expansion, but isn't, you can still reverse the expansion (in your head) until you arrive at a balloon that's a singularity, and get the "real center".
🆘Bill Cole 🇺🇦@sbi @pierrotechnique @AstroKatie @Charles
The "Real" center in the balloon analogy is unreachable and imperceivable to anyone on the 2D surface.
Adding a dimension to everything, we live in a 3D space 'surface' of a 4D space-time universe, and the "Real" center would be...
OVER THERE->
(Imagine that I am pointing backwards in time... )
@grumpybozo @pierrotechnique @AstroKatie @Charles Yeah, but this, basically, just says "You cannot understand this!" and calls it a day. Which is very likely true, but does, inevitably, lead to replies like my first in this thread.
@sbi @pierrotechnique @AstroKatie @Charles
Not exactly. "The Center" no longer exists as a spatially localizable point in space.
~13.7Bya everything was within micrometers and milliseconds of The Center, but what *was* that tiny dense volume is now spread out across more space than anyone anywhere "inside" can see due to the inflation of space.
Points in space aren't persistent entities. They're only "points" because we cannot perceive the time-cones through space-time that they represent.