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Physics, Astronomy & Cosmology / Does anyone understand Roger Penose's view of cyclic universe?

« on: 03/01/2023 02:38:36 »

You can pick this up on almost any youtube clip if you search his name and view of universe or whatever.

His general view appears to be that there was a universe before ours.  Then one before that.  Then one before that.  Not a "multiverse", with bubble universes going on all over the place, all at different times and the same time both, but just one after the other.  So far, so good, I can at least understand that.

But when he goes into more detail about his theory, he loses me.  He basically said our universe started out of the old one, which (according to him, but which I've heard others have said) will have in the far far future little or no mass left (he kind of hems on this point), and that when there is little or (presumably) no math left, time stops, because matter is a wave and you need waves to keep time, and when that happens the universe somehow goes from huge and with no matter anywhere to what we see as the big bang.  He claims that you don't need inflation in his model - indeed what we think of as inflation happens naturally in the "old" universe.  Something like that.

I can't even picture it.  On the time thing, if there is no mass, there are still photons/energy, which so far as I can tell have wave like properties, at least as much as mass, so why would time stop if there was no mass in the universe?  On the more general point about some huge, cold, no mass having universe somehow transitioning to one that is incredibly hot, expanding, etc. etc., he does not explain that, and I do not understand it.

Does anyone understand his proposal?

Thanks!

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Physics, Astronomy & Cosmology / Question about relativity's "relative" movement

« on: 02/01/2023 23:47:50 »

I understand that if one thing is moving at close to light speed relative to something else that is moving little, the one moving at close to the speed of light experiences a time slow-down - if it were to look at a clock held by the item moving little that clock would be ticking very, very fast from its point of view (and a clock held by the fast moving item would look to be ticking very slow to the slow moving item).

Question - let's say in the entire universe there are only those two items described above - how on Earth (lol) would "the universe" determine which is moving fastly relative to the other? From any point of view, they would be approaching each other, or moving away from each other, very quickly, but it would seem impossible to tell which is moving relative to the other. How does the "universe" "know" which one really has the relatively fast motion and thus which clock should be running fast and which slow?

Related question - I've always heard that relativity theory says basically that space is not an absolute - there is no "ether" for example. Space is not its own thing per se, but just describes relationships between different objects or other things. If that were the case, my question above would seemingly be valid.

But I distinctly remember listening to an audiobook some time ago that seemed to say that the motion of objects in the universe was actually RELATIVE to spacetime. This seemed weird to me, like almost inconsistent with everything I had ever heard (or thought I had heard). But, if that is right, then the "universe" should not have a problem determining which particle was doing the (fast) moving and which one was not.

Is what I heard right or wrong?

Thanks!