In the review, Professor of Philosophy David Albert tries to address Krauss's thesis, that quantum field theory provides such a compelling explanation for the origin of the universe that religion is unnecessary. As I'll explain briefly below, I agree that such a premise on its own would be a significant over-statement. However, I can't quite tell whether Professor Albert misunderstands Krauss's premise, or whether his frustration with the book prevented him from explaining himself clearly.
First, Professor Albert appears to take issue with the the assertion that under quantum field theory (the most well-tested theory in physics), there is no empty space. He does correctly understand that the matter we see represents specific arrangements of quantum fields that produce particles. He also understands that in a vacuum, these fields undergo quantum fluctuations that spontaneously produce and destroy particles. The misunderstanding may come when Professor Albert tries to define the opposite of these fields as "nothing". While nothing is a philosophically meaningful idea, it is not a physically meaningful one. Under quantum field theory, there is no place in the Universe where one could find an absence of quantum fields. According to physics today, there is
no nothing.
This is an important contribution to philosophical cosmology, because it raises the possibility that the Universe may not have been created. We know that the visible Universe had some form of a beginning in time, the Big Bang. Physicists do not yet know with certainty what happened in the first moments of the Big Bang, nor before then. One idea that physicists are working on is that the fields that define physical interactions in the Universe might have spontaneously emerged from an underlying eternal quantum reality. Their hypothesis is that the particular characteristics of those fields might be a product of quantum variations, and that the form of the fields that give rise to our habitable universe is just one of many possible arrangements of the fields. This suggests two things. First, it suggests that there is nothing special about the time at which the Big Bang occurred, because it was initiated from an already-existing reality. Second, it suggests that the Universe we live in might be one of infinitely many possible universes that actually exist, thereby explaining how by chance we could find ourselves in a Universe suited for our habitation.
I would advise that healthy skepticism be applied to this idea. As of yet, there is no experimental evidence to support the hypothesis that our Universe emerged from an eternal quantum reality. We have seen no indication that the parameters of our quantum field theory themselves vary quantum mechanically; they seem to be constant within the visible Universe. Therefore, the idea is merely an extrapolation.
And yet, while Krauss's quantum cosmology is not supported by data, the philosophical and religious cosmologies that he is seeking to displace are completely detached from scientific data. Indeed, quantum cosmologies have the possibility of developing into true physical theories, with testable predictions. In the future, it may be possible to falsify quantum cosmology, or even to conduct successful experiments that would yield deeper insight into the nature of the Universe. At the moment, I am unaware of any framework for producing testable experiments from either philosophy or religion.
I must point out, though, that the above argument means that the title of Krauss's book is misleading. If the Universe originated in quantum fields from an eternal reality, it was not created out of nothing. It is possible that this is the point that Professor Albert was trying to make.
This brings me to my second criticism of Professor Albert's review. He implies that Krauss's thesis can be dismissed because there is no explanation for where the underlying quantum reality has come from. While it is true that Krauss has to take quantum mechanics for granted, it is equally true that all philosophical and religious cosmologies have to take their fundamental premises for granted too.
What, then, is the difference between saying, "Quantum mechanics just is" and "God just is?" There is only one difference, as far as I can tell. Unlike religious or philosophical premises, quantum mechanics (or something currently indistinguishable) is verified to exist in this Universe. I admit, the leap from knowing quantum mechanics works in the visible Universe to assuming it applies to a greater reality is big. I am skeptical. However, that leap is much, much smaller than assuming something exists -- such as God, or even Nothing -- that has no verifiable manifestation in the current Universe.
As I've said, while I'm familiar with the arguments that other scientists have presented, I haven't yet read Krauss's book. Perhaps his tone is too condescending, as those passionate about their faith are often wont to be. Perhaps he's also significantly over-reached in claiming that his hypothesis is an explanation.
However, I am surprised that Professor Albert, as a philosopher, would imply that the appeal of quantum cosmology is "pale," "small," or "silly." It is not. This quantum hypothesis is appealing because it may be testable. If it is, it won't just bring problems into clearer focus, it will provide tools to confirm that we have learned more.
