It's what ya get on your head for posting vanities.Just kidding!!!!! Just kidding!!!!
My questions for the big bang theory: Who made what blew up, and who made it blow up? ;-)
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There is evidence for this, and other related theories. Quantum physics says that, roughly speaking, matter can be created out of "nothing", with some small probability. Every once in a while, the nothingness of space-time will simultaneously generate a particle and its corresponding antiparticle. Usually, the two particles recombine to annihilate each other, but under certain circumstances they won't. For example, if the particles happen to appear at the event horizon of a black hole, one may get sucked into the black hole while the other is ejected.
Since individual particles are formed all the time due to quantum mechanics, occasionally multiple particles will be formed at the same location. The probability is very small, but space-time has been around forever, so it has happened a lot. With very, very small probability, quantum mechanics says that a whole universe can pop right up out of space-time. Again, since space-time has been around forever, the probability that it would happen eventually is basically 1.0. Well, it did happen, and here we are.
There are some interesting problems with the Big Bang theory, even among physicists. The most striking is similar to the one you mention. You wondered why everything didn't just fly off in all directions without ever forming larger particles, much less galaxies. I think the explanation for your problem is that early on in the universe's history -- way before one-trillionth of a second -- the material of the universe was dense enough that it formed large clumps that persisted after inflation, and turned into stars, galaxies, and galactic clusters.
The other problem that physicists wonder about is why the universe is actually so homogeneous. Why is it that whatever direction you look in the universe, it's actually pretty much the same? In principle, any minor variations during the early formation of the universe should have persisted, so there should be something like cracks or discontinuities in the patterns of galaxies. But there aren't.
Joao Magueijo -- in a book called "Faster Than the Speed of Light" -- has a new, post-Einsteinian, post-inflation theory of the cosmos that explains this strange homogeneity. Basically it posits that during the first sub-trillionth of a second of the universe, the speed of light was faster than it is now. This enabled energy to be shared and equalized across the entire universe simultaneously, producing the subsequent homogeneity. There's no experimental proof for this theory (comparable, say, to Einstein's prediction that the mass of the sun would bend starlight), but it hasn't been disproved yet, either.