How to get something from nothing

Review of "A universe from nothing" (Lawrence Krauss)
Published in Skeptical Inquirer, Nov/Dec 2012.

There are two voices in this book. One is that of Krauss the science popularizer, carefully leading his reader through the intricacies of modern cosmology. The other is that of Krauss the anti-theistic rhetorician, eager to deflate philosophy and theology by denying their ability to make any contribution to the truly fundamental questions that perplex us about our existence. I had quite different reactions to these two personae.

Krauss uses the philosophical question of whether Something can come from Nothing as a recurring theme in his voyage to the forefront of cosmology. His explanations of the science are first-rate. They constitute most of the book, and make it well worth reading. However, I was not convinced of his claim that science gives a positive answer to the question of whether Something can come from Nothing. I also found it hard to discern a coherent viewpoint in the (anti-)philosophical rhetoric with which he surrounds the science: he made expansive claims on behalf of science, but he also expressed a more modest view of its reach.

What can Science answer?

To start with the rhetoric, most skeptics will share Krauss's irritation at theologians who seriously propose that we need God as the first cause of the universe. As he notes (p173), these arguments can be refuted in short order by pointing out that the God of religion is loaded with far more assumed properties than are required for a first cause. After making this point, I think the anti-theist's best bet is to stop talking. If you try to make it seem as if science can answer the big questions that religion claims to address then you will likely end up offering science-inspired speculations that undermine your own skeptical credentials. Krauss starts by shrugging off such inhibitions, offering science as the answer to deep questions (p xvi, p182). But later in the book he seems to assign it a more limited role.

Defining Nothing

If you want to apply science to big questions like can Something come from Nothing? then, as Krauss makes clear (p144) you need a scientific formulation of the question that allows it to be tested by experiment. However, his efforts to define Nothing seem half-hearted; he mostly defines it as empty space which is not noticeably more precise. He also proposes equal amounts of matter and antimatter (p177) and space filled with a constant energy density (p103), both of which sound more like Something than Nothing. There are sharper definitions available: the most obvious would be all the degrees of freedom are in their lowest-energy state (ground state): we'll return to this below. A more radical definition would be no degrees of freedom at all, in which case it would certainly be impossible to get Something from Nothing.

The Great Explainer

The bulk of the book, its first eight chapters or so, is dominated by the familiar voice of Krauss the science popularizer. Krauss unveils an extremely understandable introduction to modern cosmology. He starts off with dark matter, the unidentified but now almost indisputable extra ingredient whose presence in galaxy clusters has been revealed by the way its gravitational field bends light passing through the cluster from more distant objects. He spends one chapter on the flatness of the universe, which can be inferred from the pattern of microwave brightness that we observe in the sky. An apparent detour in to quantum mechanics and the energy of virtual particles prepares us for more exotic and speculative aspects of cosmology, starting with dark energy, a completely mysterious background of uniformly spread-out energy that is posited to explain the recently-noticed acceleration of the expansion of the universe. Krauss spends a chapter drawing out the dismal consequences: if the universe continues its accelerating expansion then most of it will disappear from view, leaving future astronomers in a cooling shrinking prison. More cheerfully, the same acceleration process, occurring in a violent burst early in the big bang, gives us inflation, an explanation of the flatness of the observed universe. Krauss's coverage of these topics is both expert and informal. Using a combination of historical anecdotes, down-to-earth examples, and simple diagrams, he manages to communicate both well-established science and cutting-edge research in a way that will be accessible to almost any reader.

Something from Nothing?

In places throughout the book, and in a more sustained way in later chapters, Krauss returns to the question of whether the science that he has described shows that one can get Something from Nothing. His strongest pronouncement is that theologians and philosophers have no foundation in science for their contention that Nothing will always remain Nothing (p174). Here Krauss is making an interesting and provocative claim, but I think it is an overstatement. If one uses a natural scientific definition of Nothing, namely the lowest-energy state of a system, then it is a simple consequence of Schrodinger's equation that this state will never evolve in to any other state. Krauss suggests that fluctuations in the ground state can be the source of Something, but this is really just an artefact of using classical language which obscures the static and unchanging nature of the quantum mechanical ground state. The only way such so-called fluctuations can become real is through the influence of an environment consisting of additional degrees of freedom that, through a process called decoherence, effectively measure the state of the original system. But decoherence will not occur if the environment is also in its ground state (C. Kiefer and D. Polarski, Adv. Sci. Lett. 2, 164-173 (2009)). So, as long as we are in the realm of conventional quantum mechanics, current science supports the theologians: Nothing will always lead to Nothing.

Conventional quantum mechanics, however, does not include the dynamical flexing of space that we think is an essential aspect of gravity. For that one would need a theory of quantum gravity. Krauss, as usual being admirably clear about the fact that he is stepping in to speculative uncertainty, outlines some ideas that have been suggested about the quantum-gravitational nucleation of baby universes and the possible origin of our universe from them. However, this does not imply that one is getting Something from Nothing. As Krauss himself notes (p182), theories of quantum gravity may not contain anything corresponding in a straightforward way to our current concepts of Nothing and Something. This leaves one unable to come to any scientific conclusions about questions involving these concepts. At this point the science of Nothing is overwhelmed by so much ambiguity and speculation that I am not sure how much advantage it has over theology.

It's a science book

It is remarkably enjoyable to read a book and find it full of insightful truths, especially when it is spiced with provocative authorial contentions. I am impressed at Krauss's strong commitment to evidence over prejudice. He always tells the reader how much evidence supports the ideas he is presenting. His discussion of the anthropic principle is excellent, and includes the rarely-emphasized point that in order for it to be a genuine explanation one needs to know the underlying probability distribution (p176). I loved his quotation from Feynman, rejecting the idea that science is a search for ultimate laws of physics (p177); I think it shows that Feynman understood that science is not in the business of answering the big questions. To quote Krauss himself, what is really useful is not pondering this question but rather participating in the exciting voyage of discovery... (p178). In other words, after all the promises of scientific answers to the big questions, the whole question of Something from Nothing turns out to be a nice authorial device for motivating a wide-ranging explanatory tour through modern cosmology. And there's no question that Krauss is one of the master tour guides, with the rare gift of bringing understanding of science to audiences far beyond the ivory tower of academic research.

Mark Alford (2012)


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