eMTe wrote:How is it possible that a closed system suddenly explodes without use of external force if it is the only closed system existing (space and time still don't exist)? And if it was infinitely hot and dense (so must have exploded) how it is possible that it reached that state "inside itself" without space and time existing within it?
I'm afraid this is not a question that we can answer with the tools that we currently have.
How long it took to reach that state? Maybe it was in that state for several billions of years and all of a sudden decided to explode, but how it survived for such a long time being infinitely dense and hot?
But time is/was/smujh (don't have the proper verbs) meaningless. It smujh bang. My unofficial theory is that a former universe either broke down or reached the end of infinite and all of its matter and energy was released into a new universe. How did that one form then? Well, from the one before that. How did the first one form then? Well, you see, smujh is like a loop, with no end and no beginning, and... Hell, we aren't able to comprehend this.
Also, I don't quite understand why this baby Universe decided to divide itself into the particular number of particles and forces we predict to exist today. It exploded, OK, but what happened afterwards must have been either written in it as some kind of DNA code or it exploded in this way, because something outside let it spread under these, and not other, circumstances. It sounds funny that something that is extremely hot and dense later becomes something built of several dozens of different particles (why several dozens and not only two - one could ask)."
Well, there are two options: Either you try to apply meaning to randomness or you say there is a plan behind it.
As long as randomness follows certain observable rules, it becomes predictable, but you'll never be able to explain completely why a certain result was obtained (it was "random"). But the number "two" would be extremely unlikely, since the rules of this universe say that "extremely hot and dense" is also extremely volatile, in constant flux. As soon as it started expanding and you put time into the equation, you got slightly less extremely hot and less extremely dense areas, which would naturally lead to the formation of new particles due to a different point of flux. And so on and so on until enough yoctoseconds had passed for the core to be spent. Existing particles would then continue to mutate as they were exposed to new amounts of density and temperature. This is inevitable due to the physical laws of this universe.
If you say there's a plan behind it, it becomes a theological discussion.
What I find interesting is that the universe is flat (or very nearly so). For whatever reason the universe existed within 0 spatial dimensions. Now, for whatever other reason, when the Big Bang occurred, the universe only spread in 2 dimensions. It does occupy 3 dimensions now, but the spread should be much, much larger if it had wandered into the third dimension at an early age. Why 2 dimensions? Why not 1? Why not 3? Why did it go from 0 to 2? Did the third dimension not exist to begin with?
Obviously other people have thought about this, but this boggles my mind. The "answer" is that the universe had an exact "critical value" of matter and energy to spread in two dimensions (practical, this must be the case) and that it suddenly hugely increased its rate of expansion (cosmic inflation, theoretical). Even small deviations, which would have happened if the universe had spread at a constant rate of expansion, would have messed up the universe, and it would have either crunched in on itself or spread too thin for gravitational forces to form galaxies. The combination of the exact amount of matter and energy with a sudden, unexplained increase in rate of expansion to form a flat universe is one hell of a lucky shot.
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but its basics are very simple. As usual.