Quote Originally Posted by drewmandan View Post
I've never understood how the cyclical universe hypothesis dealt with entropy. Either the laws of thermodynamics break down at the big bang, or there's an external area outside our universe, giving us more energy. Neither option is very satisfying.
Energy is never lost. It is lost as thermal energy, and dissipates through the universe. It doesn't leave the universe--the universe is a closed system (for this argument. Just as you said, it doesn't make sense for energy to come in from an outside source, it also doesn't make sense for it to leave to an outside place.). The universe has the same amount of stuff (energy and matter) as it had in the first place.