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Universes in perspective.

Review by Edmund Bertschinger

How vast is the universe? How were the laws of nature set? How is it that there are creatures able to ask these questions? These queries underlie a wonderful tour of cosmology and scientific practice led by Martin Rees, Astronomer Royal of Great Britain and one of the world's leading theoretical astrophysicists.

It has long been fashionable for cosmologists to speculate in areas overlapping with philosophy, metaphysics, and religion. Questions of origins - of the universe and ourselves - hold endless fascination for scientists as well as for the public. Rarely, however, does a scientist of Rees's stature summarize so clearly our current understanding and then extrapolate so plausibly to a more complete picture of our place in the universe.

The concept of a universe expanding according to Einstein's general theory of relativity dates to the 1920s. Cosmologists often describe the universe with an "open" or "closed" mathematical model beginning instantaneously with a "big bang" and looking the same, on average, everywhere on large scales. However, as Rees explains, it is more natural to suppose that the portion of the universe we can see is only a small part of a much larger and more varied cosmic archipelago, for which he has coined the term "multiverse."

Within our cosmic "horizon" and perhaps far beyond, the universe is similar to our relatively smooth, expanding neighborhood. At vastly larger distances - far beyond the 15 billion light-years we can now see - there may be other regions where the constants of nature are radically different, where space itself may even have a different number of dimensions. Although these ideas are unproven, they follow naturally from modern views of the early universe firmly grounded in mainstream physics.

If the multiverse concept is right, then the coincidences that enable intelligent life to evolve in the universe may have a natural explanation within physics. Most but not all "universes" (demoted now to parts of the multiverse) are stillborn because their fundamental laws would not favor the development of complexity and intelligence. Given a large enough (and possibly infinite) ensemble of universes with different laws, one or more could host beings able to wonder about their existence.

What takes this book far beyond armchair philosophy is Rees's skill in explaining the key ideas of modern cosmology and in tackling head-on the coincidences that have enabled life to evolve in our universe. For example, one of the puzzles of modern physics is why gravity is so much weaker than the other fundamental forces of nature (electromagnetism and the short-range forces between subatomic particles) As Rees shows, the longevity of stars and of our universe depends on the weakness of gravity. If gravity were much stronger, we wouldn't be here to inquire. Similarly, the primeval ripples that seeded structure in our universe could not have been much stronger or weaker without destroying the conditions needed for intelligent life to arise.

These arguments are examples of the "anthropic principle" stating that conditions in the universe were necessarily such that intelligent life could arise. Anthropic reasoning has been unpopular among some scientists because it appears to surrender predictive power. Instead of striving for a "theory of everything" (as argued, for example, in Dreams of a Final Theory by physicist Steven Weinberg), cosmologists may be admitting defeat.

Not Rees. He shows us that, even without understanding fully the fundamental laws of physics or their origin, we can nevertheless make reasonable inferences. "In the broader perspective of a 'multiverse,'" he explains, "anthropic reasoning acquires genuine explanatory force." Rees's book is an important addition not only to the popular cosmology literature but also to the history and philosophy of science itself.

Before the Beginning is exceptional for its broad scope. Not only does Rees review the astrophysics of neutron stars, black holes, cosmological dark matter, the cosmic microwave background radiation, and cosmic strings (all subjects to which he has made significant research contributions); he also highlights the origin of the chemical elements, the nature of hypothetical wormholes, and the recent discoveries of planets around Sun-like stars. These topics are enlivened by an array of "what if" questions. For example, if neutrinos interacted much more strongly or weakly with other forms of matter, massive stars would not explode as supernovae and thereby not pollute the galaxy with the chemical elements needed for life.

The historical "what ifs" are equally fascinating: physicist Robert H. Dicke was preparing to search for cosmic microwave background radiation in 1965 when it was accidentally discovered by Bell Laboratories radio engineers Arno A. Penzias and Robert W. Wilson. Three years later, Jocelyn Bell and Anthony Hewish discovered pulsars in another scientific accident; neutron stars could well have been discovered earlier with optical measurements of the Crab Nebula or later with X-ray telescopes in space.

Rees provides fascinating commentary on the sociology and methodology of science and on the relationship between scientists and the media. How scientists choose problems to study, how discoveries become recognized, the interplay between theory and experiment or observation, and the role of journalistic hyperbole (often instigated by the scientists themselves) are all skillfully addressed.

A playful dialogue between Rees and his Cambridge colleague Stephen Hawking underlies this book beginning with Hawking's foreword. While providing readers with a longer chronology than Hawking's Brief History of Time, Rees has produced a book that explains much more and deserves to be as widely read.

Rees, Diebel Win Bower Awards

On April 30th, Martin Rees was honored with the 1998 Bower Award and Prize in Science from Philadelphia's Franklin Institute. The prize of $250,000 is given annually to "a distinguished scientist for outstanding work in the life or physical sciences."

The Institute also honored John C. Diebel, founder and chief executive of Meade Instruments Corp., with the Bower Award for Business Leadership. He was cited for "his courage, insight, and leadership of a commercial venture founded on the premise of making astronomy accessible and affordable to the public." The award carries no cash prize.

EDMUND BERTSCHINGER is a cosmologist and professor of physics at the Massachusetts Institute of Technology. His research includes using supercomputers to simulate the formation of structure in the universe.
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Title Annotation:critique of Martin Rees' book 'Before the Beginning: Our Universe and Others'
Author:Bertschinger, Edmund
Publication:Sky & Telescope
Article Type:Bibliography
Date:Aug 1, 1998
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