Nine Crazy Ideas in Science: A Few Might Even Be True

  • Robert Ehrlich
Princeton University Press: 2001. 254 pp. $24.95, £16.50

Niels Bohr once remarked, when confronted with an unorthodox theory, that the problem was not whether it was crazy, but whether it was crazy enough to be true. Modern science, especially physics, is replete with outlandish ideas that defy common sense and intuition. It is almost impossible for the non-scientist to discriminate between the legitimately weird and the outright crackpot. If black holes, antimatter and virtual quantum particles are taken seriously, why is faster-than-light travel or extra-sensory perception pooh-poohed by scientists?

Credit: DAVID NEWTON

Physicist Robert Ehrlich has assembled a fascinating collection of apparently crazy ideas, and subjected them to careful analysis, assigning each a 'cuckoo' index of implausibility. Some of them, like the claim that small doses of nuclear radiation might actually be beneficial, he finds fairly convincing. To others he gives a decisive thumbs down, such as the much-publicized theory that AIDS isn't caused by HIV, or that having more guns in circulation leads to less crime. Ehrlich points out how statistics can be misleadingly presented in these cases, and how the distinction between effects that are causally related and those that are merely correlated often gets blurred.

Readers will make their own judgements about the various claims. Personally, I would not give the existence of tachyons — hypothetical particles that exceed the speed of light — quite the zero cuckoos that Ehrlich assigns. I do, however, share his enthusiasm for the offbeat theory of Thomas Gold that reserves of oil, coal and gas are not all produced by biological processes (the conventional story) but can be generated by primordial methane percolating up from deep in the Earth's crust and subjected to the activities of subterranean microbes. Gold has received a lot of flak for flying in the face of geological orthodoxy, and although I feel that the case he makes is far from decisive, I believe he deserves far more credit for his ideas. In particular, his early championing of the theory that there exists a deep, hot biosphere turned out to be startlingly accurate, and is now generally accepted.

One crazy idea to which Ehrlich assigns medium plausibility is time travel. It is a recurring theme of science fiction, but can it really be done? Travel into the future is unproblematic, and known to be possible; it is a standard prediction of Einstein's theory of relativity and has been confirmed experimentally many times. But going back in time is another matter entirely. If that were possible, then all sorts of causal paradoxes loom, such as the famous example of the time traveller deliberately killing his grandfather as a baby, thus negating his own existence.

In spite of its bizarre overtones, the possibility of visiting the past has attracted the attention of many serious researchers in recent years. Most of the work relates to the proposal that a wormhole in space could be used as a time machine. A wormhole is like a black hole, but with an exit as well as an entrance. If one existed, it could provide a short-cut between distant points in space. Whereas falling into a black hole would be a one-way journey to nowhere, entering a wormhole might enable you to come out moments later in another part of the Universe. The theory of relativity predicts that a wormhole can be adapted so that an astronaut traversing one would come out before he went in. Wormholes remain highly speculative, but no knock-down argument yet exists that proves them to be physically impossible.

Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time

  • J. Richard Gott
Houghton Mifflin: 2001. 291 pp. $25, £18.99

In Time Travel in Einstein's Universe, Richard Gott has come up with an alternative method of visiting the past, using hypothetical entities called cosmic strings. These would be exceedingly narrow tubes of trapped energy left over from the Big Bang, containing enough mass to seriously warp space and time. Gott envisages a pair of parallel cosmic strings flying past each other at high speed, and argues that an astronaut following a path looping around the strings could be transported back in time.

Gott's proposal is hardly practicable, being even less plausible than engineering a wormhole. Still, the merit in studying time travel lies not so much with the practicalities, but more with the way in which the topic illuminates the deep foundations of physics. Obviously, science must give a rational and self-consistent account of reality, so genuine paradox is not permitted.

Gott tries heroically to make the subject accessible to the non-specialist reader, although some of the discussion gets pretty technical, and occasionally mysterious. Perhaps his most striking claim is that the entire Universe could be a time machine that reaches back to the Big Bang and engineers its own creation. Some readers may well regard this idea as a reductio ad absurdum of the whole subject, but for those who enjoy a speculative romp across some of the most fascinating topics in modern physics, Gott's book will prove a delightful challenge.