That’s a question I got on twitter just now after the Feynman gig from @elainepixie.

I said (broken down into 140 character chunks):

One definition of “nothing” is “vacuum”, by which physicists mean “lowest energy state”. That exists. But in quantum mechanics it’s not really empty. It is permeated by quantum fields (e.g. the photon field) and it fluctuates. Particles pop in and out of brief existence, even in the lowest energy state of space-time. And in fact the field of the Higgs boson doesn’t even fluctuate around the value of zero, but around 246 GeV. So I guess really to have “nothing” means no physical laws, no time, no space. In that sense not sure what it means to say such a thing “exists”. You can speak about it, but surely it’s the opposite of “existence”?

Hmm. Anyone got a better answer?