Question: the big bang theory proposed that everything in the universe started from something callled singularity which is smaller then an atom. how can you stuff everything in the universe????

Alessandro Guazzi answered on 12 Mar 2013:

Really good question! Let me start by saying that our knowledge of the very beginning of the Big Bang is very limited and full of guess-work, although they’re trying to recreate the kind of environment that was at the beginning of the Big Bang at CERN in Switzerland.

The answer to your question lies in the fact that actually there was little or no “stuff” to chuck into the singularity! At the temperatures and energies that we think the universe was created, all the forces that we know of in our present universe simply weren’t there! There was no gravity, so its hard to talk about mass, there was no electromagnetic force, so you can’t talk about charged particles or atoms, and so on. The best way to think about what there was at the beginning is by thinking of a really concentrated ball with lots and lots and lots of energy. As the universe, after the big bang, started expanding, things started to cool down and the matter that makes up our universe started to look more like what it looks like now.