You just ask. Explain the limits of your knowledge so she/he can gear the answer accordingly. If you're in the 4th grade and studying earth science, the answer will be phrased differently than if you are a post-graduate student in theoretical physics.
The big bang theory is a cosmological model. Is this really the question you are trying to ask?
No big bang, no universe, no stars, no life on any planet, nobody here to ask what would've happened without a big bang.
Then we wouldn't be here, and you wouldn't be able to ask this question.
OK, I'll ask. "What is the evidence?"
According to the believes of physics and the big bang, we know that the big bang was both big and a bang. Since we are still receiving radiation from the big bang, So considering that factor I would say that it was big and a bang. What do you believe?
Big Bang - Big Bang album - was created on 2009-08-19.
Current theory is the Big Bang
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How did it what? - It isn't known what caused the Big Bang, if that's what you mean.
The big bang created itself.
big bang: This is the big bang theory
I guess you mean "disprove". There is lots of evidence for the Big Bang; I don't think you'll be able to disprove it. Anyway, look up some texts or videos about the Big Bang, to be familiar with what it proposes. Then you can either change your mind and decide that the Big Bang model is reasonable after all, or if you don't, at least you know what you are fighting against. Well, I think that personally, they shouldn't have shown Penny in bed with Leonard. But then, perhaps I should ask, "Which Big Bang" are you talking about?