- The Washington Times - Sunday, December 30, 2001

OUR COSMIC HABITAT
By Martin Rees
Princeton University Press, $22.50, 205 pages
REVIEWED BY LARRY WITHAM

Not long ago, cosmologists occupied a fringe of science that was sometimes suspect, but almost always viewed as speculative.
That changed soon after the 1965 discovery of a cosmic background radiation, or leftover heat, predicted by the "hot big bang" theory. In the 1990s, the Hubble Telescope sent back pictures of galaxies 9 billion light years away and the COBE satellite measured more rippled afterglow from the birth of the universe, said to be an explosion from a single point.
And so it was that cosmology, which must use mathematics more than observation, was consecrated a hard science. On this rising tide of good standing, Sir Martin Rees' "Our Cosmic Habitat" advances the cause further with an enjoyable introduction for lay readers.
Now Britain's Astronomer Royal, Mr. Rees began as one of the young Turks who emerged in the 1960s from the celebrated Cambridge circle of astrophysicists that also produced a Stephen Hawking. Mystery still shrouds how many of the millions of buyers of Mr. Hawking's "Brief History of Time" read it, let alone understood it. But this is clearly not at issue for Mr. Rees' accessible work. Written to inaugurate the Scribner Lectures at Princeton, the book version is concise and shines with the dry wit and street-wisdom of a veteran in the field.
The diplomacy of seniority also shows. He knows there are skeptics our there, and that university public relations departments, or eager scientists, can "hype" the "truths" of the cosmos before the evidence is in. Still, he writes, "The big bang theory deserves to be taken at least as seriously as anything geologists or paleontologists tell us about the early history of our Earth."
Cosmologists can measure the constants of physics (unlike fossil research), he writes, and thus they have "90 percent confidence in extrapolating right back to the first few seconds of cosmic history." What is more, it is a science that "deepens our sense of intimacy with the nonterrestrial."
The author mostly delivers on that promise by a table-side manner, even as the topics range from the impersonal anatomy of stars, our sun and planets, the role of atoms and molecules and ways of galaxies. One sparkle of the book is Mr. Rees' use of analogies to explain the abstract (plus, there's easy-going diagrams).
Your jet flight, for example, is but a millionth the speed of light. And overall, the universe's matter is evenly spread, making its extent visible, much as low waves on an ocean (but not high waves) allow the eye to see across its surface. "Stars are basically, now well understood," Mr. Rees writes. "We know enough about atoms and about gravity to calculate what a gravitationally confined fusion reactor" which means a star "would look like."
But if star colors, brilliancies, types and life cycles are an open book, galaxies remain a mystery.
Their various circular shapes are a puzzle, as is why, with so little gravity-anchoring matter in them, they do not fly apart. The bets are on the presence of "dark matter" in every galaxy, which has gravity but is unseen. Mr. Rees thinks it will be understood by 2010.
But finally his story has a design to it, which is to present the case for a field in which he takes the lead: the theory of multiple, or infinite, numbers of universes. "The multiverse concept is already a part of empirical science," he argues. "We may already have intimations of other universes, and we could even draw inferences about them and about the recipes that led to them."
As with others around Cambridge in the 1960s and '70s, Mr. Rees was part of the research on the remarkable fine-tuning of our universe. He probed "anthropic" coincidences, a long list of exacting cosmic numbers from forces in atoms to ages of stars and the size of the universe that made possible a planet with human life.
To this, some scientists said, "So what? Of course the world looks fine-tuned for us, because we are here." Those of a religious bent turned the data into the gospel of a Designer. Mr. Rees, however, says that while the fine-tuning is a genuine surprise, it is far less so if there are more universes than one. By analogy, a shopper at a well-stocked "off-the-rack clothes shop" would not be surprised to find at least one suit that fit. "Likewise, if our universe is selected from a multiverse, its seeming design or fine-tuned structure would not be surprising," he writes. Then he raises the question on everyone's mind. Is this testable science, or is it more like philosophy? He notes that indeed technology and the speed of light limit what humans can see, but that is not a limit on reality.
"Some day we may therefore have grounds, either for belief or disbelief, in other universes," he writes. It may be a kind of full circle for astronomy which, he reminds us, "is by far the oldest quantitative science."

Larry Witham is a reporter for The Washington Times.


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