mathematicalproiectionofme Posted July 12, 2019 Share Posted July 12, 2019 ^ Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted July 12, 2019 Share Posted July 12, 2019 No one knows. 1 Link to comment Share on other sites More sharing options...
Phi for All Posted July 12, 2019 Share Posted July 12, 2019 Also, the BB wasn't necessarily the beginning of the universe. The BB theory describes only the development from an earlier very hot and very dense state. It's possible the universe has always existed. 1 Link to comment Share on other sites More sharing options...
mathematicalproiectionofme Posted July 12, 2019 Author Share Posted July 12, 2019 Just now, Phi for All said: Also, the BB wasn't necessarily the beginning of the universe. The BB theory describes only the development from an earlier very hot and very dense state. It's possible the universe has always existed. good point 1 Link to comment Share on other sites More sharing options...
QuantumT Posted July 12, 2019 Share Posted July 12, 2019 15 minutes ago, Phi for All said: Also, the BB wasn't necessarily the beginning of the universe. The BB theory describes only the development from an earlier very hot and very dense state. It's possible the universe has always existed. But if the "hot dense state" was the universe (spacetime), then the nothingness around it was not, I assume. Or do we count the "place" that spacetime is expanding into as a part of the universe? Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted July 12, 2019 Share Posted July 12, 2019 1 minute ago, QuantumT said: But if the "hot dense state" was the universe (spacetime), then the nothingness around it was not, I assume. Or do we count the "place" that spacetime is expanding into as a part of the universe? No. I think we count it as part of our imaginations. There is absolutely no evidence that it is there, and there is no requirement for it aside from the way we tend to think. Link to comment Share on other sites More sharing options...
QuantumT Posted July 12, 2019 Share Posted July 12, 2019 (edited) 24 minutes ago, J.C.MacSwell said: No. I think we count it as part of our imaginations. There is absolutely no evidence that it is there, and there is no requirement for it aside from the way we tend to think. So, you're saying that "everything" (spacetime) grows bigger, but there is no place to grow in? Doesn't that defy logic? Edit: Unless we name the place it's growing into: "Does not exist", of course. Edited July 12, 2019 by QuantumT Link to comment Share on other sites More sharing options...
Strange Posted July 12, 2019 Share Posted July 12, 2019 24 minutes ago, QuantumT said: But if the "hot dense state" was the universe (spacetime), then the nothingness around it was not, I assume. There is no nothingness around it. The universe is all there is (nothing outside) 24 minutes ago, QuantumT said: Or do we count the "place" that spacetime is expanding into as a part of the universe? It is not expanding into anything. If that is hard to get your head around, there are two things that might help: 1. Assume the universe is infinite. If it gets bigger, it is still infinite (see Hilbert's Hotel for a good analogy). 2. Just think of it as the distance between things increasing, rather than the universe getting bigger. 3. Or think of it as the average density decreasing. Note that even if the universe is finite, there is no "edge" or boundary, so there is no "outside". Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted July 12, 2019 Share Posted July 12, 2019 (edited) 12 minutes ago, QuantumT said: So, you're saying that "everything" (spacetime) grows bigger, but there is no place to grow in? Doesn't that defy logic? Yes. Based only on the set of assumptions we are wired with it certainly does. But there is no reason to believe that set of assumptions is correct. There is no evidence or requirement for it. Edited July 12, 2019 by J.C.MacSwell Link to comment Share on other sites More sharing options...
Strange Posted July 12, 2019 Share Posted July 12, 2019 8 minutes ago, QuantumT said: Doesn't that defy logic? It might defy intuition, but that's not the same thing (and not really relevant!) Link to comment Share on other sites More sharing options...
QuantumT Posted July 12, 2019 Share Posted July 12, 2019 4 minutes ago, Strange said: There is no nothingness around it. The universe is all there is (nothing outside) It is not expanding into anything. If that is hard to get your head around, there are two things that might help: 1. Assume the universe is infinite. If it gets bigger, it is still infinite (see Hilbert's Hotel for a good analogy). 2. Just think of it as the distance between things increasing, rather than the universe getting bigger. 3. Or think of it as the average density decreasing. Note that even if the universe is finite, there is no "edge" or boundary, so there is no "outside". It might defy intuition, but that's not the same thing (and not really relevant!) 5 minutes ago, J.C.MacSwell said: Yes. Based only on the set of assumptions we are wired with it certainly does. But there is no reason to believe that set of assumptions is correct. There is no evidence or requirement for it. I get it now. But it wasn't Hilbert's Hotel that helped me. It was a name I gave it. I call it: "Does not exist" 1 Link to comment Share on other sites More sharing options...
J.C.MacSwell Posted July 12, 2019 Share Posted July 12, 2019 3 minutes ago, QuantumT said: I get it now. But it wasn't Hilbert's Hotel that helped me. It was a name I gave it. I call it: "Does not exist" Probably a pretty safe bet... Link to comment Share on other sites More sharing options...
StringJunky Posted July 12, 2019 Share Posted July 12, 2019 22 minutes ago, QuantumT said: I get it now. But it wasn't Hilbert's Hotel that helped me. It was a name I gave it. I call it: "Does not exist" Space is created between things, so, we don't need an 'outside'. Link to comment Share on other sites More sharing options...
QuantumT Posted July 12, 2019 Share Posted July 12, 2019 (edited) 6 minutes ago, StringJunky said: Space is created between things, so, we don't need an 'outside'. There are two reasons I thought of an "outside". Mainly because I've seen universe simulation videos, where you actually look at it from beyond. And secondly because of the multiverse model, where our universe is just one of countless neighbor universes in an endless vast vacuum. Edited July 12, 2019 by QuantumT Link to comment Share on other sites More sharing options...
StringJunky Posted July 12, 2019 Share Posted July 12, 2019 22 minutes ago, QuantumT said: There are two reasons I thought of an "outside". Mainly because I've seen universe simulation videos, where you actually look at it from beyond. And secondly because of the multiverse model, where our universe is just one of countless neighbor universes in an endless vast vacuum. Yes, it's a necessary visual device to imagine an outside but we should be mindful it is not actually part of that model. The MV model is another different model but don't mix them up and it's not generally accepted as the mainstream model. Link to comment Share on other sites More sharing options...
QuantumT Posted July 12, 2019 Share Posted July 12, 2019 3 hours ago, Phi for All said: Also, the BB wasn't necessarily the beginning of the universe. The BB theory describes only the development from an earlier very hot and very dense state. It's possible the universe has always existed. Are you suggesting a big bounce? By asking that, I also bring this thread back on the intended track Link to comment Share on other sites More sharing options...
Phi for All Posted July 13, 2019 Share Posted July 13, 2019 46 minutes ago, QuantumT said: Are you suggesting a big bounce? I was pointing out that assuming the BB was the "beginning of the universe" was incorrect. I think it's likely the universe is cyclic, but we can't assume it. We observe expansion, but what mechanism does the universe use to contract back? Link to comment Share on other sites More sharing options...
beecee Posted July 13, 2019 Share Posted July 13, 2019 10 hours ago, Phi for All said: I think it's likely the universe is cyclic, but we can't assume it. We observe expansion, but what mechanism does the universe use to contract back? Particularly since we observe that the expansion is accelerating. I suppose though that that scenario would rest on whether the DE will always be there. Link to comment Share on other sites More sharing options...
swansont Posted July 13, 2019 Share Posted July 13, 2019 14 hours ago, QuantumT said: So, you're saying that "everything" (spacetime) grows bigger, but there is no place to grow in? Doesn't that defy logic? It defies your preconceptions Link to comment Share on other sites More sharing options...
Strange Posted July 13, 2019 Share Posted July 13, 2019 14 hours ago, QuantumT said: Are you suggesting a big bounce? There are multiple speculative ideas for what might have happened: big bounce, continuous inflation, universe from nothing, infinitely old universe, and on and on. There is no evidence for any of them currently, so pick your favourite. Dark energy would seem to make the big bounce unlikely, but maybe future discoveries will make it plausible again. Link to comment Share on other sites More sharing options...
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