A skillful retelling of the story of our universe's birth

By Lawrence M. Krauss
Lawrence M. Krauss is chair of the physics department at Case Western Reserve University and author of "The Physics of Star Trek" and "Atom." His new book, "Hiding in the Mirror: The Mysterious Allure

March 6, 2005

I confess that when I agreed to review Simon Singh's new book, "Big Bang: The Origin of the Universe," I did so with some trepidation. Singh is one of the leading popular expositors of science in Britain, but there are dozens of popular books of vastly varying quality, most of which I have read at one time or another, that deal with this very subject. They would seem to leave little room for anything new to be said, either well or poorly.

I was pleasantly surprised to discover that although much of the material in "Big Bang" has indeed been covered in earlier books, there are fascinating historical nuggets interspersed throughout, and the account itself is so comprehensive, compelling and clear that it proves a useful addition to the literature — and comes at a time, moreover, when the cosmic story badly needs retelling.

The current vogue in writing about cosmology is to focus on new ideas — like multiverses and dark energy — many of which have little empirical basis as yet. In Singh's book, however, you will not read much about the last decade in cosmology — perhaps the most revolutionary decade since the 1920s, when the astronomer Edwin Hubble's pioneering observations first established that our universe is expanding and therefore must have had a beginning at a finite time in the past. Indeed, except for a brief concluding chapter and an epilogue, Singh's book brings the reader only up to 1965, when a Bell Laboratories antenna in New Jersey picked up a mysterious microwave signal that was soon identified as the afterglow of the explosive birth of our universe — the Big Bang — and which laid to rest any lingering doubt in the scientific community as to the Bang's reality.

What makes Singh's story particularly useful is that he carefully builds up, step by step and in vivid and explicit detail, the empirical basis of our modern understanding of the universe. Beginning with a delightful introduction to the methods used by the Greeks to estimate the size of Earth, the moon and the sun, Singh proceeds to describe the discoveries of the great astronomers from Galileo to Hubble and to lay out with authority the theoretical interpretations of their discoveries and the predictions that have subsequently been verified by a host of further observations and experiments.

This interplay between sound theory and definitive observation is the basic stuff of science, and it is too often overlooked. A cogent example of this interplay occurs early in the book, when Singh explains why it was not unreasonable, on the basis of the evidence then at hand, that Ptolemy's Earth-centered solar system was favored for centuries over the sun-centered system that had been proposed by Aristarchus some 400 years earlier. As Singh points out, an Earth-centered cosmology, even with its complicated epicycles within cycles, allowed more accurate predictions of the motions of the planets than a sun-centered solar system in which the planets moved in circular orbits. It was not until the 17th century, when Johannes Kepler — using the meticulous astronomical observations of his mentor Tycho Brahe — showed that the actual orbits of the planets around the sun were described by ellipses and not circles, that the sun-centered model was finally embraced, as much for its predictive power as for its simplicity.

In this country, 23 centuries after Aristarchus, the scientific community finds itself at the forefront of a desperate battle against well-financed and well-organized groups whose prime purpose is to attack the very foundations of our scientific picture of the universe. The recent attack on evolution by groups espousing a vague and largely untestable notion called "intelligent design" has received a great deal of media attention. What is less noticed is that in almost all cases when the teaching of evolution in the public schools has come under attack, an assault on the teaching of the Big Bang has not been far behind.

These groups make use of a semantic trick. They argue that evolution and the Big Bang are mere theories, not facts. In doing so, they distort the definition of a scientific theory. A theory is not a hypothesis. Theories — like evolution, the Big Bang and, for that matter, Einstein's theory of general relativity — have achieved their standing not because they are simply speculation but because their myriad predictions have withstood the test of time and experiment. What Singh's book makes eminently clear is that there are few human intellectual achievements as remarkable or as well grounded as the realization that we live in an expanding universe that is roughly 14 billion years old and whose earliest moments began in a fiery dense phase that almost defies imagination to picture.

Yet picture it we can. We can perform complex calculations, based on experiments at nuclear reactors, that precisely define the conditions in the first seconds of the birth of the universe. As a result, we are able to predict (or "postdict") the distribution of the primordial elements (hydrogen, helium, lithium) that resulted. And a plethora of astronomical observations has confirmed — to our satisfaction and perhaps also our amazement — that the cosmic abundances of these so-called light elements do indeed agree with our predictions.

Perhaps the most significant prediction of the Big Bang model is one that was not widely known until after its effect had been observed. Arno Penzias and Robert Wilson, the two Bell Laboratories scientists who discovered the microwave afterglow of the Big Bang, had no idea that Ralph Alpher and Robert Herman, along with their mentor, noted Russian American physicist George Gamow, had argued more than a decade earlier that such background radiation must exist and that it should have a temperature very close to the temperature of the background that Penzias and Wilson measured approximately and that we have now measured to better than 1 part in 10,000.

Singh's readers will come away with not only a clear understanding of these remarkable developments but also an accurate picture of the scientific process itself — and an appreciation of the extraordinary individuals who contributed bits and pieces of our present understanding of the universe. While they will miss out on some of the details that we cosmologists are currently debating, they will be in a much better position to appreciate the 2,500-year-long, ongoing scientific journey to determine exactly how the universe began and what its future will be. •