Stephen Hawking's "The Grand Design" – the review, part 5

M-Theory


String theory is considered by most physicists to be the best, if not the only, candidate for a theory that reconciles General Relativity with quantum mechanics. It's more than a little controversial, though, as it still remains completely untested. It is a grand idea, and one that seems very likely to be correct. But much remains to be decided.

String theory faced a bit of a hurdle in its early development – it seemed to be not one, but five different theories. But further research revealed that these were not distinct theories, but overlapping theories that explained the same phenomena. (If you're curious about the details, I highly recommend Brian Greene's Elegant Universe.) These five theories, together, are called M-Theory. It's such a ridiculously complex theory that it's still incomplete. In some theories, the answers to complex equations are approximations; in M-Theory, many of the equations themselves are approximations.

M-Theory (no one seems to know what the "M" actually stands for) predicts the existence of a finite multiverse. Apparently the fact that its prediction is finite (something like 10^500 of other universes) is a big deal, and Hawking uses these multiverses, in part, to explain the unique design of our universe. We could calculate the probability of universes with certain features forming, including our own. Many of these universes would be inhospitable to life, while others would quickly collapse before they could expand into a universe like our own. And just as extra-solar Earth-like planets make our own seem a little less remarkable, so too, Hawking argues, the existence of other universes would make ours seem a bit less special. While it's clear Hawking seems to think that M-Theory is the best hope for physics right now, he seemed more cautious to me than his critics had led me to expect when it came to making bold proclamations about the current state of the theory.


What's it all mean?

The Grand Design was an enjoyable read, but frankly a mild disappointment merely because at this stage of the game, I'm more interested in what's going on in physics and how cutting edge theories about branes and curled-up spatial dimensions can be tested. To that end, I've found books by Brian Greene and Lisa Randall, as well as some of Hawking's older material, a bit more robust and pragmatic. The Grand Design contains its share of difficult-to-comprehend quantum weirdness and plenty of grand ideas, but personally I would have liked a fair bit more exposition on the next steps physicists are taking. A more casual reader, though, would probably enjoy the book a great deal.

There's also very little that's new in The Grand Design. Again, this is not a problem for casual readers who might be put off by the size and scope of Lisa Randall's excellent Warped Passages, but for a guy like me who's not only read a number of popular science books on the subject but also subscribes to Scientific American which regularly features articles on cosmology, there wasn't a whole lot, aside from the concept of the universe not having a single past, that was new to me in this book.

Hawking's been criticized by theists and even some fellow physicists – Roger Penrose, to name one – for dragging God into the picture, particularly when so many of the theories to which he is appealing are conjectural. But I don't feel that Hawking overstepped his grounds, and the reactions to the book have been somewhat overstated. The fact is that a big part of a great many if not all religions is that there are religious concepts of the origin of the universe. Some assert that the universe is eternal; others, particularly Western religions, that the universe was created by a god who exists independently of the universe. So when scientists start investigating these big questions, a clash with religion is inevitable. But that's not science's fault, it's religion's. Science is in the business of exploring the deepest mysteries of our existence, and if the results clash with religious beliefs, guess which one has to change?

What Hawking has claimed in The Grand Design is not that he has disproved the existence of God. Nor has he appealed to speculative physics as though they were proven fact. He's suggested, rather, that what we know about physics removes the necessity of God from creation – in fact, the universe didn't have to be created at all. Sooner or later, believers will have to contend with the fact that developments in physics are slowly undoing many of our long-held beliefs about the nature of reality. Right now, believers who have responded to the book seem to take some comfort in the provisional nature of M-Theory, but I can't help but feel they've missed the point. The idea that God created the universe is no longer of any meaningful utility. And as I've often said before, the only thing worse than a god who doesn't exist is a god who might as well not exist.


Part 1 - Model-dependent realism

Part 2 - The universe has all possible histories


Part 3 - The not-so-miraculous design

Part 4 - A finite universe without a beginning

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