The New Time Travellers: A Journey to the Frontiers of Physics
By David Toomey
W.W. Norton £15.99, 391 pages
FT bookshop price: £12.79

This is real science fiction. Not cowboys and indians in space helmets, but a diverting account of how some of the brightest minds have seriously considered the possibility of time travel. So forget contraptions such as H.G. Wells’ time machine and Dr Who’s Tardis. The common starting point for David Toomey is the astonishing fact that Einstein’s general theory of relativity – the best description we have of the large-scale structure of the universe – permits time travel to the past. And his physicist heroes include Kip Thorne of Caltech, Stephen Hawking of Cambridge and Richard Gott of Princeton.

More precisely, there is nothing in Einstein’s equations of general relativity which prevents travel back in time unlike, say, the Second Law of Thermodynamics, which forbids the egg you smashed on the floor to jump back, whole, into the egg-cup. That time travel is possible is one thing; how it might be accomplished is another. Toomey’s book is devoted to the speculative ideas of those physicists brave enough to be seen publicly tinkering with a subject most scientists would lump in with parapsychology and faith healing.

The most popular vehicle for time travel is probably the “wormhole”. This is a tunnel through time and space created when the flat plane of space-time becomes folded, so that two widely separated geographic points are brought together until they almost touch. Much of The New Time Travellers is taken up with accounts of how enthusiasts such as Kip Thorne have developed theories of the creation and maintenance of wormholes: these delicate structures have to be propped open artificially if molecule, mouse or man is to escape down one.

Of course, there is no evidence for the existence of wormholes or any other time travelling device. Another problem is that even if the science is valid, time travelling swiftly throws up questions of philosophy and morality to which equations provide no answers. For example, could individuals who journey back in time influence the future? Why do we not see among us time tourists from a future age? Are we simply too uninteresting?

Toomey traces the origin of these studies to a groundbreaking paper published in 1988. He has written a lucid account of a brief period in modern physics when well-respected scientists felt free to explore a topic more commonly the province of crackpots and fiction writers. But as he points out, many of the scientists most involved with the subject in the 1980s and 1990s have now moved on to other things. Time travel has proved an intriguing diversion – but not a sustainable topic when there are other, more tractable problems to be studied.

Alan Cane is the FT’s senior technology correspondent.