So I was watching the show "Curiosity" on the Discovery channel last night. In the show, Stephen Hawking describes the birth of the Universe, and why our theory of inflation leaves no place for God. I'm not going to comment on the God thing, but Hawking said something that got me thinking. Basically, he said that the entire Universe has zero energy because space is essentially equivalent to negative energy. This gave me an idea--if virtual particles are constantly being created and annihilated everywhere, then positive energy is always being created (even if the two particles annihilate, the annihilation has to create some energy, right?). So if energy is being created from vacuum at a constant rate, then negative energy (space) must be created to balance out that constant rate of energy creation. This would cause a *constant* rate of expansion for the universe, possibly similar to the one we've been measuring in the past couple decades. Does this make any sense at all? Is this what cosmologists mean when they say that vacuum energy is responsible for the expansion of the universe? I'm an undergraduate physics major, but I still haven't taken GR or Quantum Field Theory, so I could be way off.