So I hope this counts as a valid physics question, I didn't think it fit in philosophy even though it's probably speculative. My question is about where the universe gets its energy. From what science knows about the universe, would it need a giant power source to function, or is it a self contained system where the energy is somehow recycling or self sustained via some method unknown to me? I mean where does energy come from? Is it a side effect of the big bang that will run out? Any insight appreciated.