We all know beyond the universe, there's nothing. How come is that possible?

We all know beyond the universe, there's nothing. How come is that possible? Theory says the big bang happened, and that theory has been accepted since it was "released". But where was the energy that caused it? And how did it existed, if there was nothing? Is there anything in the "nothing"? And, if we talk about religion, how did god exist? Who made it? How was he created if there was nothing? Some people say it created himself, but how the heck that happened if there was nothing?

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