The problem with Stephen Hawking writing for the layperson is that he, himself, isn't one. He's in continual danger of overestimating his readership: one that is almost exclusively drawn from a mathematical caste far below his and that of his Cambridge contemporaries. The project he's undertaken hereùto expound on some of the most intellectually unassailable concepts in physics and make them comprehensible to the same populace that finds Who Wants to be a Millionaire? challenging and divertingùis one that is apparently too ambitious, even for him.

The Universe in a Nutshell is designed to update us on any developments that have occurred since he wrote his 1988 blockbuster bestseller, A Brief History of Time. That book, which has sold nearly 10 million copies to date, was a 200-page survey course on the origins of the universe, the existence of black holes, the nature of time, and the ongoing efforts to wed the general theory of relativity to our understanding of quantum mechanics. In Universe, we're treated to many of the same concepts, albeit updated, in a slightly more accessible reference book where each chapter can be visited independently of the whole. However, despite the abundance in the book of full-colour pictures and graphs, and notwithstanding Hawking's simple, declarative writing style and affable chats about Star Trek, nothing can disguise the fact that this is an exceptionally challenging read. More than a few times during its 216 pages I begrudged my parents for having first met at a roadside diner and not a Mensa convention. Why couldn't they have bestowed me with superior cranial contents?

Take this paragraph from Chapter 2:

If the strings have Grassman dimensions as well as their ordinary number dimensions, the ripples will correspond to bosons and fermions. In this case, the positive and negative ground state energies will cancel so exactly that there will be no infinities even of the smaller sort.

Here's another from Chapter 4:

This means that in special relativity, the time measured by any freely moving observer increases smoothly in spacetime from minus infinity in the infinite past to plus infinity in the infinite future. We can use any of these measures of time in the Schrodinger equation to evolve the wave function.

Yes, it's unfair to make examples of the statements above without any of the context that Hawking provides. It's only right, though, that readers know what kind of language they're going to bump up against. The best that almost all of us can hope to do is clamber across great expanses of impenetrable text, looking for fissures we might enter and small deposits of knowledge we might take with us. The problem with all of this, of course, is that the hardy adventurers of the mind who make it to the end of this book will have retained only a loose conglomeration of cosmos trivia, not a systematic understanding. Hawking is unknowingly spawning hordes of barstool philosophers and rumpus room physicists who are right now spouting facile and sophomoric versions of supersymmetry theory to impress their friends.

All of this is not to say that Hawking's latest effort is a failure. He succeeds brilliantly in one respect: he lifts us out of our own quotidian lives and gives us a glimpse at a many splendoured universe whose wonders are usually too big or too small for us to appreciate.

Hawking asks us to confront a number of basic truths: First, the universe had a beginning. "If stars had been radiating for an infinite time," he says, "they would have heated up the universe to their temperature. Even at night, the whole sky would be as bright as the sun, because every line of sight would end either on a star or on a cloud of dust that had been heated up until it was as hot as the stars."

Second, the universe is expanding. Nearly all the other galaxies we've observed are moving away from our own. "If the galaxies are moving apart, they must have been closer together in the past. From the present rate of expansion, we can estimate that they were very close together indeed ten to fifteen billion years ago." He suggests that the universeùjust before the big bang that caused the expansionùwas once so tightly packed together it possessed infinite temperature and infinite density. In several billion years more, one of two scenarios will occur: either the gravitational attraction between galaxies will draw them back together in a big crunch that ends time, or gravity will prove insufficient to halt the expansion of the universe and it will grow progressively colder and emptier until effectively dead.

Third, "time and space do not exist independently of the universe or of each other." Rather, "they are inextricably tangled up" in a fourth dimension known as spacetime. This dimension is warped and distorted by the gravitational effects of matter and energy in the universe, which gives all time going back to the big bang a shape roughly corresponding to that of a pear. There may be six or seven additional dimensions that "are curled up so small we don't even notice them" or conversely, are extremely large or even infinite.

Fourth, the universe has multiple histories. Hawking likens the universe to a giant casino, "with dice being rolled or wheels being spun on every occasion." He says that because the universe "keeps on rolling the dice to see what happens next, it doesn't just have one history, as one might have thought. Instead the universe must have every possible history, each with its own probability. There must be a history of the universe in which Belize won every gold medal at the Olympic Games, though maybe the probability is low."

Fifth, the universe if dotted with collapsed stars or black holesùsingularities much like the big bang, where concentrations of matter and energy are so extreme, and spacetime is so warped, that the explanatory and predictive powers of mathematics break down. Hawking contends (and many in the scientific community disagree on this) that black holes aren't entirely black, but that they emit radiation very near their event horizons (the border inside of which not even light can escape the black hole's gravitational pull). This radiation, he says, "will carry away energy, which must mean that the black hole will lose mass and get smaller." Eventually the black hole will be reduced to zero mass and evaporate completely.

Hawking also tackles two other topics that have excited imaginations for centuries: the possibility of time travel and the existence of intelligent life on other worlds. Both, readers will be disappointed to find out, are highly improbable. He mentions what he calls his "Chronology Protection Conjecture: that the laws of physics conspire to prevent time travel by macroscopic objects." While he concedes that certain regions of the universe may sufficiently warp spacetime to send microscopic particles back in time, the odds of a human making a temporal leap backwards are "one in ten with a trillion trillion trillion trillion trillion zeroes after it." As for aliens, he makes this argument: "The human race has been in its present form for only two million years out of the fifteen billion years or so since the big bang. So even if life develops in other stellar systems, the chances of catching it at a recognizably human stage are very small." He adds that "because we claim to be intelligent . . . we tend to see intelligence as an inevitable consequence of evolution." This could be a mistake. "It is not clear," he says, "that intelligence has much survival value." There may be an inherent advantage for primitive life on other worlds to remain primitive.

This conjecture on evolution and intelligence comes from chapter six, the most readable and consequently, most intellectually exciting, chapter in the book. Hawking makes an egregious gaffe at its outset by pointing to "random collisions between atoms" as having formed the building blocks of life on Earth; he makes no mention of emergence or self-organization theories advanced by biologists like Stuart Kauffman, Roger Lewin, or M. Mitchell Waldrop. Once past this irresponsible omission, however, the reader is treated to a variety of futuristic teasers: computers will increase in complexity until they exhibit intelligence; we will grow human embryos outside the human body to allow for larger brains and superior mental capacities; we will completely re-design our DNA in the next thousand years. Ultimately, the author envisions a rapidly evolving, rapidly proliferating humanity that will begin colonizing this solar system and adjacent ones in the coming centuries.

Hawking was diagnosed with amyotrophic lateral sclerosis (Lou Gehrig's disease) at the age of 21. He was given two to three years to live. Now 60, it seems that it has been his tremendous curiosity and unremitting desire to understand the nature of things that have kept him alive. Reading his book, one can sense his massive, pervasive, and ultimately reassuring spectral intellect on every pageùan intellect continually projecting out of the cruel confines of his failing body into an ether of numbers and theorems that beggar the average human mind. There is no doubt that we're verging on a new epoch of understanding. Professor Hawking has been and will continue to be our most capable guide. ò