Tuesday, 29 March 2011

Grand design book review

Nobody has ever accused Stephen Hawking of thinking small. His life has been devoted to asking foundational questions about the nature of spacetime and the origin of the universe. In his famous "A Brief History of Time" (1988), he attempted to bring the mysteries of black holes and the early universe to a wide audience. Now Mr. Hawking and Leonard Mlodinow have written "The Grand Design," which addresses some of the biggest questions of all: Why is there something rather than nothing? Why does nature have the laws it does? Why do we exist? These sorts of "Why?" questions are often neglected by most scientific practice, but the recent progress of cosmology and fundamental physics makes this a good time to tackle them in earnest.
[hawking2] NASA via Getty Images
A mosaic image of the Crab Nebula, a remnant of a supernova explosion, taken by the Hubble Space Telescope.
Putting the word "design" in the book's title is the kind of cheeky humor that Mr. Hawking has become known for. The authors' answer to the riddle of the universe has nothing to do with intelligent design or with religion generally. "Some would claim the answer to these questions is that there is a God who chose to create the universe that way. . . . We claim, however, that it is possible to answer these questions purely within the realm of science, and without invoking any divine beings."
The Hawking vs. God debate has featured prominently in the news of late. He and Mr. Mlodinow don't claim to have proved that God doesn't exist; their argument is somewhat more confined, but still important in its implications. We understand enough about the ultimate laws of physics, the authors say, to conclude that we don't need God to understand the universe.
In this short and sprightly book, Messrs. Hawking and Mlodinow take the reader through a whirlwind tour of fundamental physics and cosmology, concluding with an enthusiastic endorsement of the idea that our observable universe is only a tiny part of a much larger conglomeration, the multiverse. The universe we see is big, featuring over a hundred billion galaxies, but it's still finite. The multiverse idea suggests that there are other regions, equally impressive in size, where conditions might be quite different, right down to different physical laws or different numbers of dimensions of space.

The Grand Design

By Stephen Hawking and Leonard Mlodinow
Bantam, 198 pages, $28
But "The Grand Design" aims beyond simply surveying hot topics in contemporary physics. It has a point—that some of the evergreen "Why?" questions of philosophy may be on the verge of being answered by modern science. Each chapter serves as a step along the path to finding such answers. The key that unlocks the them is not a new idea: It's the "anthropic principle," a subject of considerable controversy among cosmologists.
If there are many different environments in the universe, we should not be surprised to find ourselves living in those environments that are hospitable to our existence. In the solar system, for example, we should not be surprised that life arose on the surface of the Earth rather than on the sun (too hot) or the moon (too dry). Similarly, if there are many different universes, we should not be surprised to find ourselves living in this one. We might hope to explain certain features of our universe simply by insisting that it allow for intelligent life. If the mass of the neutron were smaller than the mass of the proton, for example, chemistry as we know it would be impossible. Perhaps there is some other universe where neutrons are lighter than protons; but we can't live there, since such a universe might not be able to support life.
Messrs. Hawking and Mlodinow trace the logic of quantum mechanics, general relativity and superstring theory, showing how a variety of existing universes isn't merely possible but arguably natural. In string theory, space inevitably has extra curled-up dimensions that we can't see. But there are many ways for dimensions to curl up, and each of them leads to different apparent "laws of physics." Then there's the idea of inflation, which predicts that an extremely tiny region of space can blow up into a universe-sized domain. Modern cosmologists believe that inflation, once it starts, can keep going forever, continually creating new "pocket universes" with different conditions in each one.
This is a picture that has been put together by a number of theoretical physicists over the past couple of decades, although it remains speculative. Mr. Hawking's own major contributions have involved the spontaneous creation of the universe "from nothing." The basic idea comes straight from conventional quantum mechanics: A particle does not have some perfectly well-defined position but rather lives in a superposition of many possible positions. As for particles, the logic goes, so for the entire universe. It exists in a superposition of many possible states, and among those states is utter nothingness. The laws of quantum cosmology purport to show how nothingness can evolve into the universe we see today. Speculative, yes; crazy, not necessarily.
"The Grand Design" thus attempts to outline, in under 200 pages, a complete scenario for the nature of the universe and our place in it. The universe exists because it must exist; if it didn't, it would come into existence spontaneously. Once it exists, the combination of quantum mechanics and general relativity coaxes the universe into creating a dizzying variety of regions with different local conditions and physical laws. Most of these might be extremely alien and inhospitable; but some will be just right to allow for the development of complexity and consciousness. Among those, happily, is our own.
Whether this ambitious conception is actually correct remains unclear. It's not especially idiosyncratic; many theorists hold similar views of the multiverse and the anthropic principle. The important lesson of "The Grand Design" is not so much the particular theory being advocated but the sense that science may be able to answer the deep "Why?" questions that are part of fundamental human curiosity.
It is unfortunate that Messrs. Hawking and Mlodinow choose to open their book by picking a pointless disciplinary fight: "Traditionally these are questions for philosophy, but philosophy is dead." The authors nevertheless quote a number of philosophers with apparent approval and engage in more than a bit of armchair philosophizing themselves. They advocate "model-dependent realism," which asserts that the "reality" of various elements of nature depends on the model through which one interprets them. This is an interesting approach to ontology, but it won't come as shocking news to philosophers who have thought about the problem. Answers to the great "Why?" questions are going to be subtle and difficult. Our best hope for constructing sensible answers lies with scientists and philosophers working together, not scoring points off one another.



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