Roger Penrose’s theory that argues that the Big Bang will repeat is called “conformal cyclic cosmology” and Hossenfelder has her doubts about it. After summarizing the theory, she says, in part,

If the previous eon leaves information imprinted in the next one, then it isn’t obvious that the cycles repeat in the same way. Instead, I would think, they will generally end up with larger and larger fluctuations that will pass on larger and larger fluctuations to the next eon because that’s a positive feedback. If that was so, then Penrose would have to explain why we are in a universe that’s special for not having these huge fluctuations.

Another issue is that it’s not obvious you can extend these cosmologies back in time indefinitely. This is a problem also for “eternal inflation.” Eternal inflation is eternal really only into the future. It has a finite past. You can calculate this just from the geometry. In a recent paper Kinney and Stein showed that this is also the case for a model of cyclic cosmology put forward by Ijjas and Steinhard has the same problem. The cycle might go on infinitely, alright, but only into the future not into the past. It’s not clear at the moment whether this is also the case for conformal cyclic cosmology. I don’t think anyone has looked at it.

Finally, I am not sure that CCC actually solves the problem it was supposed to solve. Remember we are trying to explain the past hypothesis. But a scientific explanation shouldn’t be more difficult than the thing you’re trying to explain. And CCC requires some assumptions, about the conformal invariance and the erebons, that at least to me don’t seem any better than the past hypothesis.

Sabine Hossenfelder, “Will the Big Bang repeat?” atBackRe(Action)

*You may also wish to read:* The Big Bang: Put simply, the facts are wrong.

As to:

And here is the recent Kinney-Stein paper that disconfirms the cyclical model that she is referring to

The first reference in the preceding paper is the Borde, Guth, Vilenkin paper,

And in the following paper, Borde, Guth, Vilenkin further stated that, “This is a stronger conclusion than the one arrived at in previous work [8] in that we have shown under reasonable assumptions that almost all causal geodesics, when extended to the past of an arbitrary point, reach the boundary of the inflating region of spacetime in a finite proper time ”

Prior to this work by Borde, Guth, Vilenkin establishing, via Special Relativity, that the universe must have had an absolute beginning, Hawking, Penrose and Ellis, via General Relativity, (circa 1970), also proved that “time and space had a finite beginning that corresponded to the origin of matter and energy.”

And in the following fairly recent video, Dr. Stephen Meyer explains why the Borde, Guth, Velinken theorem turns out to be a much stronger proof for an absolute beginning for the universe than the previous proof from Hawking, Penrose and Ellis was.

Also of note: Brian Miller recently listed some fairly devastating problems with Penrose’s current CCC model that also render it untenable as a serious scientific theory. Most importantly, and devastating for Penrose’s theory, is that CCC “contradicts the empirical evidence.”

As to Sabine Hossenfelder’s observation that, “You can calculate this just from the geometry”, well, it is now also proven, via the extension of Godel’s incompletenesss into quantum physics, that any ‘geometry’ of any universe cannot be explained by reference to ‘bottom-up’ naturalistic processes.

Specifically, it is now proven that “even a perfect and complete description of the microscopic properties of a material is not enough to predict its macroscopic behaviour.,,,” and that “the insurmountable difficulty lies precisely in the derivation of macroscopic properties from a microscopic description.”

The overriding principle behind the preceding finding is really not all that hard to understand,

In short, and in conclusion, atheistic naturalists who desperately want to avoid an absolute beginning of the universe, in order to avoid the obvious Theistic implications therein, have been stopped dead in their tracks at every turn.

As Alexander Vilenkin noted elsewhere, “There is no escape, they, (cosmologists), have to face the problem of a cosmic beginning.”

Verse and Quote:

No matter how the universe began, which is unlikely to be Big Bang due to new evidence that is being ignored, the universe has a beginning. Just like the laws of physics had to have a beginning, including energy that cannot be created. With God, all things are possible, including the creation of energy. With man, not so much. The laws cannot be violated or broken in any way.