Programming the Universe By Seth Lloyd

Software for the great cosmic computer

All the evidence suggests that our Universe started out very simple, in the Big Bang, and has got more and more complex as time has passed. How has this happened? According to Seth Lloyd, a professor at the Massachusetts Institute of Technology, it is because the expanding Universe processes information in the same way that a computer operating on the principles of quantum mechanics processes information. The bigger the Universe/computer gets, the more room it has to process information, so there is increasing scope for complexity.

The particular novelty of this package is the application of quantum principles to computing, which is Lloyd's area of expertise. Many people will be aware of the mysterious nature of the quantum world, where an electron may be in two (or more) places at the same time, and Schrödinger's famous cat can be both dead and alive at the same time.

Fewer people are aware that computers using these bizarre properties have already been constructed, so that the switches inside them can be both "on" and "off" at the same time - although as yet these computers are very modest and unlikely to match the power of conventional computers for several decades. Once they do, though (for reasons Lloyd explains), they will make the best conventional computers as obsolete as the slide rule.

In Programming the Universe, Lloyd does an excellent job of explaining all this in clear, accessible language, for which he gives credit to Sara Lippincott, although she is not listed as a formal co-author. He is less successful when he moves out of his own area of expertise, and among other things gives an incorrect explanation of why sexual reproduction has been an evolutionary success, wrongly refers to the Big Bang as an "explosion", and - worst of all - makes the classic howler of describing the butterfly effect thus: "the flutter of a butterfly's wing, can be amplified over time and distance, becoming a hurricane."

The essential point about the butterfly effect is that there is no amplification. The intended image in chaos theory is that a complex system such as the weather might be poised in a delicate state between two different futures, requiring only a tiny nudge to divert it from one path to another. The "flap of a wing" might make the hurricane hit New Orleans rather than Galveston, but the hurricane is going to happen somewhere whatever the butterfly does.

These errors are worth highlighting because most of the book is so good. It provides an easy introduction to computing, to information processing, to some aspects of quantum physics and even to the story of life.

Too much space is taken up with the kind of personal background that is becoming de rigueur in popular books by scientists, and the illustrations are mostly a waste of space; but by starting out with the basics and moving smoothly up through the gears, Lloyd's approach mimics the progress of the Universe itself from simplicity to complexity. It would have been good to have an index rather than four pages of autobiography at the end, but nobody is perfect.

All of the author's infelicities can be forgiven just for his lovely explanation of the difference between sitting a large number of monkeys in front of a row of typewriters and waiting for them to produce Hamlet, and sitting the same number of monkeys in front of a row of computer terminals and waiting for a meaningful computer program to emerge. I won't spoil it, but I urge you to buy the book and check it out for yourself.

John Gribbin is the author of 'Deep Simplicity: Chaos, Complexity and Life' (Penguin)