I was reading a Wikipedia article on the Big Bounce. The gist of it is that the Big Bang could have been the initial, or recurrence, of a cycle of expansion and contraction of the universe.
If this were true, would the current universe, as it exists now, be replicated on future cycles?
Suppose we get to the end of the universe, and it collapses back in on itself in a “big crunch.” Then later on, another big bang happens. What would be the likelihood that there will eventually be another me, sitting at a desk that looks just like this crappy, cluttered old desk I’m sitting at, listening to music, and composing this foolishness as my mind wanders?
Theoretically, if this is true and the cycle occurs an infinite number of times, every possible universe might also occur an infinite number of times.
All theoretical, of course. Having no way to experimentally test theories about what occurred prior to the Big Bang, we can’t honestly say that this is a scientific theory.
If the universe did crunch instead of expanding forever until heat death, why would it replicate our universe? And if there was a cycle, wouldn’t it lose energy with each bounce? Just like a ball bounces lower and lower each time.
On the second question, it couldn’t lose energy if we posit that the universe is a closed system. A bouncing ball loses energy because it leaks it into the environment as heat. In a closed system there’s nowhere for the energy to go.
The real problem with energy is that the Big Crunch seems like the ultimate violation of entropy. But maybe one can get around that by positing that during the crunch phase time runs backward.
Which leads back to the first question. If one believes that all quantum behavior is fully deterministic even if not knowable, then one can also believe that there’s no mechanism for the introduction of randomness and each cycle will exactly replicate the previous one. Peter Lynds put forward just that theory, according to the Wiki article, which also says it’s been generally rejected for lack of a mathematical model for it. We don’t really understand what happens at the Big Bang and the laws of physics may not apply either there or during the Crunch. Maps of the cosmic microwave background radiation certainly suggest a lot of randomness occurring during the expansion.
Each re-bounce might produce entirely different fundamental laws of physics, as the forces that are unified at high temperatures break up into separate forces, their exact values contingent on…unknowns.
Also, the whole shebang might be embedded in some higher-dimensional thingie (technical term here) so that the bounces might lose energy in that overall context. Each bounce might bleed off energy (or something vaguely similar to energy) into that higher cosmos.
Or…that higher cosmos might not even have laws of conservation at all.
In any case, our universe appears to be expanding without limit, so we might not collapse back into a crunch or bounce at all. Looks more like a great expanding whoosh. (Oh, wait, that’s a term of art also!)
Isn’t eternal expansion the agreed upon outcome at this point?
I have no idea about the point the OP makes. What are the odds of our finely tuned universe even supporting life? Trillions to one seems like a very very low balled number considering minor changes in many values would make chemistry impossible.
The odds aren’t really relevant. The weak anthropic principle in its common interpretation more or says says that the physical constants must be appropriately tuned in order for observers to exist. It’s not relevant that there may be an infinity of universes not so tuned with no one to observe them. The strong anthropic principle goes further with various interpretations that basically state some variant of the thesis that observers are necessary for the universe to exist at all.
“Eternal expansion” appears to be the agreed-upon outcome at one level of understanding. At a deeper level this has to assume that our level of understanding is sufficient to make that prediction. What if physical laws are not constant, or our understanding of basic phenomena like time is not correct? What if, as Hawking has suggested, space-time is Euclidian and our perception of the arrow of time is just an illusion of our existence? This would mean that the universe in true reality is neither expanding nor collapsing but is constant, finite but unbounded like the surface of a sphere with time bundled in. In this model of “imaginary” or Euclidian time, the paradox of the singularity goes away because it’s just an ordinary coordinate. Just like the North Pole isn’t a singularity or the end of the world or the beginning of it, it’s just a place.
A slight nit-pick, the Hartle-Hawking ‘no boundary proposal’ implies a closed Universe that collapses to a big crunch, which is not currently borne out by observational evidence.
