What on earth, then, can Krauss have been thinking? Well, there is, as it happens, an interesting difference between relativistic quantum field theories and every previous serious candidate for a fundamental physical theory of the world. Every previous such theory counted material particles among the concrete, fundamental, eternally persisting elementary physical stuff of the world — and relativistic quantum field theories, interestingly and emphatically and unprecedentedly, do not. According to relativistic quantum field theories, particles are to be understood, rather, as specific arrangements of the fields. Certain arrangements of the fields, for instance, correspond to there being 14 particles in the universe, and certain other arrangements correspond to there being 276 particles, and certain other arrangements correspond to there being an infinite number of particles, and certain other arrangements correspond to there being no particles at all. And those last arrangements are referred to, in the jargon of quantum field theories, for obvious reasons, as “vacuum” states. Krauss seems to be thinking that these vacuum states amount to the relativistic-quantum-field-theoretical version of there not being any physical stuff at all. And he has an argument — or thinks he does — that the laws of relativistic quantum field theories entail that vacuum states are unstable. And that, in a nutshell, is the account he proposes of why there should be something rather than nothing.
But that’s just not right. Relativistic-quantum-field-theoretical vacuum states — no less than giraffes or refrigerators or solar systems — are particular arrangements of elementary physical stuff. The true relativistic-quantum-field-theoretical equivalent to there not being any physical stuff at all isn’t this or that particular arrangement of the fields — what it is (obviously, and ineluctably, and on the contrary) is the simple absence of the fields! The fact that some arrangements of fields happen to correspond to the existence of particles and some don’t is not a whit more mysterious than the fact that some of the possible arrangements of my fingers happen to correspond to the existence of a fist and some don’t. And the fact that particles can pop in and out of existence, over time, as those fields rearrange themselves, is not a whit more mysterious than the fact that fists can pop in and out of existence, over time, as my fingers rearrange themselves. And none of these poppings — if you look at them aright — amount to anything even remotely in the neighborhood of a creation from nothing.
Krauss, mind you, has heard this kind of talk before, and it makes him crazy. A century ago, it seems to him, nobody would have made so much as a peep about referring to a stretch of space without any material particles in it as “nothing.” And now that he and his colleagues think they have a way of showing how everything there is could imaginably have emerged from a stretch of space like that, the nut cases are moving the goal posts. He complains that “some philosophers and many theologians define and redefine ‘nothing’ as not being any of the versions of nothing that scientists currently describe,” and that “now, I am told by religious critics that I cannot refer to empty space as ‘nothing,’ but rather as a ‘quantum vacuum,’ to distinguish it from the philosopher’s or theologian’s idealized ‘nothing,’ ” and he does a good deal of railing about “the intellectual bankruptcy of much of theology and some of modern philosophy.” But all there is to say about this, as far as I can see, is that Krauss is dead wrong and his religious and philosophical critics are absolutely right. Who cares what we would or would not have made a peep about a hundred years ago? We were wrong a hundred years ago. We know more now. And if what we formerly took for nothing turns out, on closer examination, to have the makings of protons and neutrons and tables and chairs and planets and solar systems and galaxies and universes in it, then it wasn’t nothing, and it couldn’t have been nothing, in the first place. And the history of science — if we understand it correctly — gives us no hint of how it might be possible to imagine otherwise.
Perhaps my ignorance of quantum physics allows me to feel greater awe at the mystery of particles popping into existence than the reviewer's fist when he rearranges his fingers, but I still get the point. I have often heard that physicists have five different definitions of "nothing". Krauss, if his critic is right, seems to be saying that we can have creation from nothing in one (trivial) sense, and if we insist on asking if we can have creation from nothing in a stronger (untrivial) sense, well just shut up.
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