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By GILBERT WONG

Hands up all those who bought a copy of Hawking's previous book, A Brief History of Time, in 1988 and never finished it.

His latest enjoys an even more grandiose title, though thankfully it is much more readable and the text is accompanied by illustrations, diagrams and photographs, including the delightful fantasy image of Hawking playing poker with Einstein, Newton and Commander Data from Star Trek: the Next Generation.

As Hawking reminds us, he sits in the Lucasian chair at Cambridge, a position most famously occupied previously by Isaac Newton, though as Hawking quips, it wasn't electrically operated in Newton's day.

The quips come few and far between Hawking's explanations of what is essentially esoteric mathematics put in layperson's terms. Mostly he succeeds. If you ever needed a good primer on the latest in theoretical physics, this is it.

Which is not to say that much here is as easily digested as the image of the apple dropping on Newton's head courtesy of gravity. This is hardly Hawking's fault. In the 300 years since Newton the universe has grown a lot bigger and much, much stranger.

The title restates Hawking and other theoretical physicists' quest to unify the two grand theories of 20th-century science, Einstein's theory of general relativity and quantum theory.

Einstein's theory is great at explaining the grand scale of the universe. His work predicted the existence of black holes and the fact that intense gravity will warp light. He brought space and time together into space-time, a fourth dimension. Quantum theory explains what happens to the tiniest subatomic particles when matter becomes indistinguishable from energy waves, and uncertainty rules.

Find the theory that puts these two grand ideas into the same framework and you will have explained how the universe works.

Imprisoned by degenerative motor neurone disease, Hawking's intellect is conveyed solely through electronic means.

His computer-generated tones have become as widely recognised as the voice of Elvis Presley. Yet he remains alien and is made more so because much of his time is spent in a mathematical universe constructed from abstruse theorems and counterintuitive concepts that struggle to explain the invisible concrete of everyday reality.

Hawking takes us on a ride into very weird territory. He revisits super string theory, once a leading candidate for a grand unified theory, which envisages all particles in the universe as made up of vibrating strings that exist in 10-dimensional space-time. While once held up as the great hope of theoretical physics, several competing super string theories have failed to make progress.

His tour takes on Brane Space, a view of the universe that suggests we live in a reality of 10 or 11 dimensions, but with six or seven of them curled so small we are not aware of them. Theorist and mathematician Paul Townsend calls these dimensions p-branes, which is exactly the sort of humour Hawking employs when he talks of the background cosmic microwave radiation, that echo of the Big Bang, as useless for heating pizza.

The geeky jokes belie the big questions behind Hawking's work. He and mathematician Roger Penrose appear to have proved that time does not go on forever but has a beginning and an end, which in turn implies that reality is determined by scientific rules.

The pair maintain that time has a structure and wouldn't you know it, it is pear-shaped.

On the way he takes side trips into other questions: is time-travel possible? How feasible are worm-holes, the multi-dimensional shortcuts that leapfrog through the usual three dimensions we experience?

Nor does Hawking shirk controversy. As fond as he is of Star Trek, he doesn't think Captain Kirk represents the future.

He predicts that genetic engineering will inevitably produce enhanced humans. The limit of intelligence is brain size. Brain size is limited in turn by the size of the birth canal. So genetic engineering and in vitro births give us the means to engineer big-headed and hopefully big-brained babies who might one day crack the codes of existence that thwart Hawking. Sounds like science fiction? Well, so did black holes once.

Bantam Press

$75

* Gilbert Wong is an Auckland journalist.