Q:

Nothing vs. empty space

This question quotes Hawking saying: 

[...] you enter a world where conjuring something out of nothing is possible (at least, for a short while). That's because at this scale particles, such as protons, behave according to the laws of nature we call "quantum mechanics", and they really can appear at random, stick around for a while, and then vanish again to reappear somewhere else.

Nowever, is empty space really nothing? is there a distinction between non-existence and the "nothingness" of space?
Perhaps space is something, we just cannot grasp exactly what it is. Anyone can shed light on whether space is something and what exactly that "something" is.

A:

is empty space really nothing?

The physicist's 'nothing' is an example of something to the philosopher for which 'nothing' is well, let this philosopher explain in a review of "A Universe from Nothing" by Lawrence Krauss:

empty space governed by quantum mechanics (or any other laws
  of physics, or even just the laws of physics by themselves) is not
  nothing, and not even an “example” of nothing (whatever an “example of
  nothing” means), but something.  And it remains something rather than
  nothing even if it is a “good first approximation” to nothing (which
  is what Krauss presumably meant by “good first example”).  When people
  ask how something could arise from nothing, they don’t mean “How could
  something arise from almost nothing?”   They mean “How could something
  arise from nothing?”  That is to say, from the absence of anything
  whatsoever -- including the absence of space (empty or otherwise),
  laws of physics, or anything else.

