What is zero point energy?

Question

What is zero point energy?

Answer 1

Put really simply (and, some might argue, a little inaccurately), it's the energy of spacetime itself.  Nothingness still involves something, for various reasons.

Things that happen on a very small scale can sometimes grab a bit of the zero point energy temporarily and then give it back, which has led some to propose that we could find a way to grab enough zero point energy to power our technology at the large scale.  Others think that it doesn't work that way, and you can never do better than teeeeny fluctuations above zero.

And, of course, there's the decidedly minority (but fun for science fiction) opinion that if you managed to tap ZPE too deeply, you'd remove a piece of spacetime in the process, which could be a Bad Thing.  Especially if reality becomes unraveled as a result.