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The description of how the universe is expanding sounds like how an explosion expands. Rapidly then slower until it settles down and stops (with no collapse at
by gaoshan 1y ago
The description of how the universe is expanding sounds like how an explosion expands. Rapidly then slower until it settles down and stops (with no collapse at the end, just matter in place where it landed). I wonder if that could be the closest analogy?
- BurningFrog 1y agoRiess' original discovery is the opposite: The universe expands faster and faster over time.
- pavlov 1y agoAn explosion has a center. I'm not a cosmologist, but my understanding is that the universe expands everywhere and at a rate that's in fact accelerating rather than slowing down.
- dylan604 1y agoWhat does the has a center comment have to do with the rest of the comment? The big bang had a center too. That doesn't mean anything in the context though.
- Aloisius 1y agoI thought the big bang had no center because there is no edge. Rather expansion was of space itself that happened everywhere.
- faceloss 1y ago[dead]
- layer8 1y agoNo, it’s not space itself. Relative to what would it expand? It’s galaxies moving away from one another, which necessarily increases the space between them. See also: https://en.wikipedia.org/wiki/Expansion_of_the_universe#Expansion_of_space https://en.wikipedia.org/wiki/Expansion_of_the_universe#Expa...
- meroes 1y agoI don't think the big bang or the universe ever had a center.
- deleted 1y ago[deleted]
- mr_mitm 1y agoThe other two sibling comments expressed some doubt, but I can tell you with absolute certainty that in the standard model, and to the best of our knowledge in reality, the big bang did not have a center.
- dylan604 1y agoThis makes no sense to me. Are we saying the universe existed before the big bang? The big bang went boom and everything started expanding from it. How is it not the center?
- mr_mitm 1y agoNo, we are not saying that. We are saying that the entirety of space - and not just its contents - have been compressed into a point (ignoring quantum gravity for now). Any two points in space have been arbitrarily close if you play the movie backwards sufficiently close to the first moment.
- TheOtherHobbes 1y agoIt's a 4D spacetime, not a 3D space. Start with a tiny sphere. Expand it. The sphere gets bigger, but no point on the 2D-like surface is the centre. It's like that, but the surface is a 4D spacetime. You can't use your imagination to visualise this. But you can use math to describe it. Whether there's some kind of ultradimensional hypercentre is a different question. Even if there was, it wouldn't be accessible from this universe. And don't forget we don't have a clue what spacetime is. Relativity has some nice descriptions of what it does, but there's no fundamental explanation of how the universe generates the phenomena we call position, time, and distance.
- _jmh_ 1y agoThat is the best explanation I've ever heard about that "where is the center question". Thank you. Perhaps some day I'll be able to wrap my head around your closing caveat. I suspect any question I ask on that would be another "where is the center" type question.