This is the “standard model” of today’s science. I am a believer in science. But that’s not like a religious belief or faith; instead, a matter of epistemology. Which refers to how we know things.
This doesn’t mean everything in science is “true.” That misunderstands the point. Scientific precepts (unlike religion) are always subject to revision with more information. That can disprove a theory, but none is ever proven with finality. That said, however, the bulk of modern science can be pretty much taken to the bank. The concept of biological evolution, for example, will not be disproven by new information. And the same applies to most of modern physics.
Note that the expansion doesn’t mean everything is enlarging. Instead it’s space itself that’s expanding, carrying everything along with it. And stuff all moving away from us doesn’t mean Earth is at the center.
Science has figured out the physics of the Universe’s start, back to a very teensy fraction of a second after the Big Bang. But then you get to a point where the extreme conditions of density and heat mean the laws of physics as we know them don’t work. We call this a “singularity.” (The same applies inside a black hole. Some scientists speculate that a black hole’s singularity can give off big bangs; maybe that’s our own origin.)
Inability to parse out just exactly what happened in that very first instant might be considered a problem in the standard model. But there’s a difference between “don’t know” and “can’t know.” While some theorists say “can’t know,” I prefer to suspend judgment on what future science may be able to penetrate. Scientists a century ago could not have imagined today’s knowledge.
The explanation is inflation: during an infinitesimally small interval after the Big Bang, the Universe expanded faster than light speed. But didn’t Einstein tell us nothing can travel faster than light? Yes; but that applies only to objects moving through space. In inflation, it was space itself expanding.
And what caused this? It’s theorized that the force of gravity suddenly reversed, pushing stuff apart rather than pulling it together. Then, just as suddenly, it switched back. We have some ideas about why that could have happened.
However that, and the whole inflation theory, is mainly supported on the basis that it’s the only way we can account for what we observe.
Here’s another problem. We know the law of gravity: proportional to mass and decreasing with the square of the distance between objects.
A possible solution is “Modified Newtonian Dynamics” (MOND). Just as some laws of physics change when it comes to the ultra small (quantum mechanics), the law of gravity might not apply to the ultra large distances associated with galaxies. Realize that gravity being far the weakest of nature’s fundamental forces — and diminishing with the square of the distance between objects — we’re talking about a force of evanescent smallness at galactic distances. A tweak to Newton’s gravity law might explain things without requiring any additional “Dark Matter.” (While I find this idea attractive, it is not orthodox physics.)
There’s yet another problem. We had assumed that after the Big Bang’s initial energy burst (and the inflation episode), the momentum of the Universe’s expansion would be slowing. There was debate whether it would eventually slow to a stop, with gravity then starting to pull things back together, toward a “big crunch;” or would expand forever, dissipating into virtual cold nothingness; or would do neither, reaching stasis (a “flat universe”). All dependent on exactly how much mass there is. The third option seemed to be winning.
But then a new discovery blew scientists’ minds: after having slowed for some billions of years, the expansion started speeding up! And is still accelerating.
So . . . the singularity; no Time before Time; inflation; Dark Matter; Dark Energy. Science likes beautiful elegant theories. The standard Big Bang model begins to look like a clunky a Rube Goldberg contraption. With a lot of question marks. Might it all be just a huge mistake? What could an alternative possibly look like?
But suppose the Universe’s expansion does ultimately run out of steam and reverse, falling into a Big Crunch. It wouldn’t necessarily have to collapse all the way back to a singularity. Before that point, the extreme conditions could conceivably trigger a new Big Bang. Going back and forth like that forever. This avoids the conundrum of a singularity and also of a “Time before Time.” Though not the mind-bender of the word “forever.”
This is called the “Oscillating (or Cyclic) Universe,” discussed in Brian Clegg’s book, Before the Big Bang. That title hooked me in, but a more accurate one would have been About the Big Bang. Anyhow, Clegg shows there are serious problems with the Oscillating Universe concept too. He says it’s either equivalent to a perpetual motion machine or else must eventually run out of energy and expire.
There are other theories, like “branes.” And multi-universes. I won’t go into them. None strikes me as anything more than complete speculation.
Anyhow, one is forced to confront an irreducible mystery. Either the Universe had a beginning, arising out of nothing. Or else something always existed, without ever having had a beginning. No human mind can really grasp either possibility.
“Why is there something” is a question deep in my consciousness. Why I have one is itself a conundrum; but that’s only one small piece of the far larger mystery of existence itself. Most of us take it for granted, but not me. In fact, it’s my understanding of the clockwork of existence — imperfect though that understanding surely is — that nags me with that final “Why?”
It seems we should more logically expect a Universe of nothingness — a non-universe. That at least would raise no deep questions whatsoever. It would just be. (Or not-be.)
* As I’ve discussed; here are some links: https://rationaloptimist.wordpress.com/2012/04/13/why-is-there-something-rather-than-nothing/; https://rationaloptimist.wordpress.com/2013/09/29/why-does-the-world-exist/;