If you really wanted to know some of the evidence for the big-bang just crack open a 6th grade science text book. For all their faults, they hit the major points. As for the "multi-dimensional garbage", I'm not sure what you're specifically speaking of, but it seems to be a new idea from string theory. So, for all of you who keep saying, "but why did it ever 'decide' to expand?" your answer can be found there. Just another point of contention, the universe isn't necessarily infinite, unless you're speaking in terms of time. There are a couple of models of what our universe will do due to its expansion. The first being that it will continue expanding for eternity. The second, that the universe will reach a point where it will stop expanding and rebound bring itself back together.
So, if you really wanted to find some evidence of the big bang, I'd suggest hitting the library and cracking a textbook.
And the Ignorant shall fall to the Squirrels - Chip 2:54