Generalized uncertainty principle: ((dA)*(dB)) >= 1/2*|<[A,B]>| dA= standard deviation of the operator A, <Q>= <psi|Q|psi> Now, I know people say that there can't be such thing as a true vacuum, particles must be created and destroyed all the time, or else we'd know the exact position & momentum, which would violate the heisenberg uncertainty principle, a special case of the general uncertainty principle above ([pos,mom]= hbar*i). Normally, <psi|psi> is required to be 1, but in a true vacuum, devoid of anything, psi=0. This would (trivially) satisfy the Schrodinger equation, and though it wouldn't be normalizable, I don't see why it would have to be, since by assumption there's nothing to be found there. In the above equation, we'd get (dA)*(dB) >= 0. Presumably, we could measure both position and momentum to be 0 every time. So why can't a true vacuum exist?