from amazon.com:

. ..When Dr. Krauss and other physicists talk about nothing, they are speaking with the vulgar. What they mean by nothing is an area with no space that the laws of nature even came out of [[to our knowledge, symmetry breaking that happens during the big bang produces the parameters of gravity, the weak and strong forces, and electromagnetism). In reality, the "absolute nothing" that some readers are whining about has never been shown to be the earliest state of the universe. According to the Einsteinian view of time, the universe exists as a block with time as a tenseless dimension of space. This block extends infinitely into the past and the future. The earliest point we know about [[the singularity) is nothing more than a misapplication of relativity to the quantum realm and will be scrapped when a quantum theory of gravity [[possibly m-theory or quantum loop) is adopted. This makes the big bang an interesting event but not a beginning in the way that many have misconstrued it [[for a popular guide to this, read Brian Green or Michio Kaku's excellent non-technical books).

and

..http://www.sciencefriday.com/program/archives/201201132

[The answer lies in quantum mechanics.]