Playing with Planets

Gerard 't Hooft is a Nobel laureate (physics, 1999) who made important contributions to particle physics, most notably by refining the mathematical formulism of electroweak theory, an important step toward the standard model for particle physics. Playing with Planets is a popular science book dealing with extreme futurology.

Its purpose is twofold: to dismiss much science fiction as exactly that, a set of fictional constructs that will never be realised because they break fundamental physical laws, and, secondly, to predict the future in a thoroughly scientific manner by examining what we already know, and extrapolating without violating the laws of physics.

Some of the topics discussed are rather predictable and have been widely covered elsewhere. For example, the future of computing is hitched to the famous Moore's law, published in 1965, which showed that the number of transistors on a computer chip doubles every 18 months. The trend still holds true, although the time constant is now about 24 months. Hooft considers that this trend will continue. "I have complete faith in human ingenuity," he writes, predicting that nanotechnology will drive down the size of memory to the point where individual atoms are manipulated.

In terms of applications, Hooft's view is that technical innovation will take us to the atomic scale, but not below it. Subatomic particles feature in science fiction as quark computers, magnetic monopoles, warp drives and so on. But as the physical scale of the Large Hadron Collider demonstrates, the manipulation of the smallest particles now requires the largest physics experiment ever built. While it is true that totally new discoveries will be made (for example, supersymmetric particles), a reality check shows that it is inconceivable that they will lead to devices that humans could exploit.

Hooft is highly realistic on the difficulties of interstellar travel, or simply getting beyond the solar system. In the not-too-distant future, it should be possible for a spacecraft to reach Pluto in about a year by sailing along in the solar wind. But for more distant targets, the slow acceleration of nuclear-powered craft gives a limit of about 1 per cent of the speed of light before the engines have to be reversed to slow the craft.

To reach the nearest stars would take thousands of years, and no discovery that is within the envelope of the present laws of physics can change that conclusion, which is still ignored by fiction writers. Therefore it is extremely unlikely that humans could ever journey to other stars, and that has implications for the debate on intelligent life in the universe. Aliens millions of years ahead of humans in terms of technological advance still have to operate within the laws of physics, meaning that it is unlikely that they could ever develop interstellar travel. Perhaps this is how we can solve the Fermi paradox, which asks: if a multitude of advanced civilisations exists in the galaxy, why have we not been visited by spaceships or probes? Answer: the travel time is far too long.

In 1950, Arthur C. Clarke's book Interplanetary Flight proposed a future in which there would be colonies on the Moon and Mars. From today's perspective, a lunar scientific base now looks just about feasible - in, say, 20 or 30 years' time - but a presence on Mars surely lies very far in the future. Hooft concludes that the dream worlds envisaged by visionaries are impossible dreams. Throughout this entertaining book he dissects fact from fiction to see what the future might hold, and maintains a dry sense of humour.