I'm a complete layman, and very curious, but don't have a lot of in-depth knowledge to tackle the following: Recently, someone presented an argument to me against the Big Bang. His argument was that taking into account the matter of the universe and the nature of gravity, the universe should have collapsed back into itself shortly after the Big Bang. I read in "The Fabric of the Cosmos" that a theory exists t hat gravity can have a repulsive effect rather than an attractive force under certain conditions, and the time shortly after the Big Bang was one of those brief moments (in addition to light traveling faster than it does now.) But I'd like to know more about this, if anyone can help. In addition, this person posed the question "Why don't Population II stars contain heavy elements?" I'm not sure how this ties into the Big Bang, or disproves it, but maybe someone can shed some light. He seemed pretty sure that for the Big Bang to exist, it should have produced heavy elements in ALL stars. I'm showing my ignorance here, but this looks like the best place to get some answers. I'd appreciate it!