Frequently Asked Questions in Cosmology
under "What about the oscillating Universe?"
(First that intro):
If the Universe recollapses, then there is another singularity at the time of the Big Crunch. A singularity means that the laws of physics break down, so we have no way to predict whether the Big Crunch will connect to another cycle of expansion. Even if the density were high enough to cause a recollapse, there would be no guarantee that the Universe would oscillate. But the current evidence is strongly against any recollapse, which would rule out the oscillating Universe. See PBS or Ask an Astronomer about this.
Note: I will be debating the latter assertion.
The PBS blurb on Oscillating Universe:
I know this topic has been addressed in other threads, but I'd like a fresh start here if I may.
One of the implications of the big-bang theory is that the universe will one day end, or at least any life in the universe will come to an end. If the universe is either open or flat, meaning that it expands forever, it will survive for an infinite period of time. But eventually all the material in all the generations of stars will be exhausted, and the universe will grow cold and dark. In a closed universe, in which the expansion eventually stops and a contraction follows, the end is far from cold and dark—as the Big Crunch approaches, the universe grows hotter and brighter until it implodes into a singularity and gets crushed out of existence.
But is that what would really happen? Some scientists speculate that the Big Crunch would not signal the end. Perhaps another Big Bang would follow the Big Crunch, giving rise to a new universe of possibilities. The idea that Bangs follow Crunches in a never-ending cycle is known as an oscillating universe. Though no theory has been developed to explain how this could ever happen, it has a certain philosophical appeal to people who like the idea of a universe without end.
BTW, I have critiqued Lynde's model on a site I forgot, but "time reversal" is not an option for me, as per my repetitive critique of time in my "spacetime thread."
But I have have a similar model that doesn't require a sci-fi rendering of time.
Our cosmic event horizon is just a small bubble of visibility *within* the thickness of the "rubber" of the good old cosmic expanding balloon. This mini-cosmos within the maxi-cosmos, the Whole Balloon, is cycling through bangs and crunches even as the whole balloon keeps expanding.... *Yes*... out into the infinity of space.
Anyway, we can't even "see out of the rubber" (the visible cosmos) let alone see the *yes* empty space within or beyond the bubble.
Well, this should stir up some more trouble.
BTW, I ask all respondents to refrain from starting with "expanding space" as an established fact. I know "stuff expanding out into empty space" is usually called a "misconception"... but I see it as a viable contender as a cosmology.
Nuff for now.