09/12/2010 03:30 pm ET Updated May 25, 2011

Hawking and the Multiverse

I still have not received my review copy of Stephen Hawking's newest attempt at popularizing cosmology, The Grand Design, written with Leonard Mlodinow. But I thought I'd better say something about it since everyone else is. What I have to say is based on the reviews I have read, so let me first quote from these.

The Economist:

In their "The Grand Design", the authors discuss "M-theory", a composite of various versions of cosmological "string" theory that was developed in the mid-1990s, and announce that, if it is confirmed by observation, "we will have found the grand design." Yet this is another tease. Despite much talk of the universe appearing to be "fine-tuned" for human existence, the authors do not in fact think that it was in any sense designed. And once more we are told that we are on the brink of understanding everything."

Philosopher Craig Callender:

This multiplicity of distinct theories prompts the authors to declare that the only way to understand reality is to employ a philosophy called "model-dependent realism." Having declared, "Philosophy is dead," the authors unwittingly develop a theory familiar to philosophers since the 1980s, namely "perspectivalism." This radical theory holds that there doesn't exist, even in principle, a single comprehensive theory of the universe. Instead, science offers many incomplete windows onto a common reality, one no more "true" than another. In the authors' hands this position bleeds into an alarming anti-realism: not only does science fail to provide a single description of reality, they say, there is no theory-independent reality at all. If either stance is correct, one shouldn't expect to find a final unifying theory like M-theory - only a bunch of separate and sometimes overlapping windows.

Physicist Peter Woit:

One thing that is sure to generate sales for a book of this kind is to somehow drag in religion. The book's rather conventional claim that "God is unnecessary" for explaining physics and early universe cosmology has provided a lot of publicity for the book. I'm in favor of naturalism and leaving God out of physics as much as the next person, but if you're the sort who wants to go to battle in the science/religion wars, why you would choose to take up such a dubious weapon as M-theory mystifies me.

Cosmologist Larry Krauss:

As a scientist, I have never quite understood the conviction, at the basis of essentially all the world's religions, that creation requires a creator. Every day beautiful and miraculous objects suddenly appear, from snowflakes on a cold winter morning to rainbows after a late afternoon summer shower.

Yet no one but the most ardent fundamentalists would suggest that every such object is painstakingly and purposefully created by divine intelligence. In fact, we revel in our ability to explain how snowflakes and rainbows can spontaneously appear based on the simple, elegant laws of physics.

So if we can explain a raindrop, why can't we explain a universe? Mr. Hawking based his argument on the possible existence of extra dimensions--and perhaps an infinite number of universes, which would indeed make the spontaneous appearance of a universe like ours seem almost trivial.

Yet there are remarkable, testable arguments that provide firmer empirical evidence of the possibility that our universe arose from nothing.

Cosmologist Paul Davies:

Our universe is just one infinitesimal component amid this vast - probably infinite - multiverse, that itself had no origin in time. So according to this new cosmological theory, there was something before the big bang after all - a region of the multiverse pregnant with universe-sprouting potential.

A refinement of the multiverse scenario is that each new universe comes complete with its very own laws - or bylaws, to use the apt description of the cosmologist Martin Rees. Go to another universe, and you would find different bylaws applying. An appealing feature of variegated bylaws is that they explain why our particular universe is uncannily bio-friendly; change our bylaws just a little bit and life would probably be impossible. The fact that we observe a universe "fine-tuned" for life is then no surprise: the more numerous bio-hostile universes are sterile and so go unseen.

So is that the end of the story? Can the multiverse provide a complete and closed account of all physical existence? Not quite. The multiverse comes with a lot of baggage, such as an overarching space and time to host all those bangs, a universe-generating mechanism to trigger them, physical fields to populate the universes with material stuff, and a selection of forces to make things happen. Cosmologists embrace these features by envisaging sweeping "meta-laws" that pervade the multiverse and spawn specific bylaws on a universe-by-universe basis. The meta-laws themselves remain unexplained - eternal, immutable transcendent entities that just happen to exist and must simply be accepted as given. In that respect the meta-laws have a similar status to an unexplained transcendent god.

When Krauss says, "there are remarkable, testable arguments that provide firmer empirical evidence of the possibility that our universe arose from nothing " he means better arguments than M-theory. He goes on to tell how the total energy of the universe is zero, with the positive energy of matter balanced by the negative energy of gravity. This means no energy was required to create the universe, making it easy to come into being spontaneously. This was a point Hawking himself made in his 1988 bestseller A Brief History of Time. He should have stuck with his original story.

Krauss's colleague on the Origins Project at Arizona State University, Paul Davies, who won the 1995 Templeton Prize for Progress in Religion, is more willing than most cosmologists to cut religion a little slack. He refers to the meta-laws obeyed by all universes as unexplained and so having the same status as a "transcendent God."

In fact, the meta-laws have a plausible explanation. In the twentieth century physicists realized that there was a direct connection between the most important laws of physics and the basic symmetries of space, time, and the abstract space of quantum state vectors. These symmetries are required for any physical model to be independent of the special point of view of any observer. Any objective universe, therefore, must be governed by these meta-laws. Furthermore, the "bylaws" that are different from universe to universe result from the spontaneous breaking of some of the symmetries when the universe cools.

So, at least according to the reviews, Hawking and Mlodinow haven't said much that physicists and cosmologists haven't already heard before. However, thanks to Hawking's notoriety, at least more people will now have heard that science has plausible answers to how the universe came about naturally without the need for a creator. Hopefully this will include those theologians and apologists who continue to wrongfully insist that modern science has demonstrated a need for God.