I understand that the notion of “before” the Big Bang is a little bit of a misnomer since our time began at that moment. But what are some theories about what was happening before that moment? Where did all this stuff in our universe come from and where was it before it became our universe?
Bonus question: Was there ever a moment when the universe was as dense as a black hole?
I am not qualified to answer this, but if I understood Michao Kaku correctly, he said that it was possible that universes are born out of the vacuum all the time. He pointed out that there are two kinds of nothing. Nothing, which is the absence of anything and the vacuum which is the absence of matter. It has an average energy of zero, but at the quantum level, there are fluctuations of energy and out of these could be born new universes. It’s my understanding that these other universes would have no contact with ours (they are out-of-phase, if you will).
Someone will be along shortly to explain how wildly inaccurate my answer is.
FWIW,
Rob
The mainstream scientific answer is that the question is meaningless, since, as you say, time began at that moment. Though there are also a multitude of non-mainstream answers.
I think it’s Jeopardy, or some local show.
One almost mainstream theory is eternal inflation: most of the universe (multiverse, omniverse, totality of all that there is, who can tell anymore!) is continuously inflating (by which I mean expanding exponentially fast), but at some localized regions, inflation stops, the inflaton field decays, and you end up with something that you might justifiably call a universe, such as ours. There are many such universes, and overall, spacetime has a fractal kind of structure consisting of inflating areas containing bubble universes.
Another theory is loop quantum cosmology, an offshoot of loop quantum gravity, which is a contender of string theory in the effort of finding a quantum theory of gravity, and in which the prequel to a big bang seems to always be a big crunch; that is, every universe’s beginning is another’s end. The whole thing is often called a big bounce.
Oh, and a recent one is Roger Penrose’s conformal cyclic cosmology. Here, the idea is that every universe’s final state is so completely featureless that one might as well take it to be the beginning of the universe, which is also (near) completely featureless. But this is even more conjectural than the other proposals, requiring some unknown new physics for which there does not seem to be any motivation other than that Penrose really likes the idea.
Another idea is that the universe consists of two or more 3-D branes embedded in some higher dimension. Our local “universe” started when two of these branes collided and teh energy of that collision is the big bang. But before that the local area was probably just quieting down from the last time it happened.
I have no idea how accepted this idea might be.
Oh and your bonus question: I’m pretty sure sufficiently large black holes don’t have to be very dense at all. And if there is enough matter/energy in the universe to halt its expansion and turn it into a contraction, then the universe itself is essentially a black hole. (But I cold be wrong you know.)
One would think that the answer would be the universe.
Given the contract until critical mass / explode / expand until limits are reached / latherrinserepeat concept, immediately prior to the Big Bang was the universe. It was just scrunched into one ball.
Or something like that.
My unscientific theory is that there was another universe just like this one that was humming along just fine until some guy figured out how to fly faster than the speed of light, causing the whole damn ball of wax to collapse.
My brane hurts!
It’s all about quantum fluctuations , cycles of contraction-inflation-expansion and stuff like that.
We just happen to live in one of those fluctuations that occured recently (15 billion years or so ago), and appears to be still going on, for a while at least.
There’s a lovely quote from a famous cosmologist named Edward Tyron that “a universe is just one of those things that happen from time to time.”
Sorry.
Does this mean a Gumby is God?
After each Big Bang came a Big Cigarette.
At the temperatures created by such energy, wouldn’t the ball of wax have completely melted?
Some say this universe is merely someone’s drug-induced fantasy. This is the “Big Bong Theory.”
Sorry.
I was gonna say, before The Big Bang came The Big Inhale, so that makes more sense now.
Actually, it’s specifically the fantasy of a youngish, neurotic Manhattanite who used to live with an actor friend until he married his best friend’s sister and is still working out the emotional impact of his father being a transvestite.
It’s the Big Bing Theory.
The “yo-yo universe” theory.
That’s the slang expression. The official title is the Jersey Shore Universe Theory. 