Forget fiction: time travel is real.

Owning a time machine is like having super powers. You could send the lottery results back in time and win millions. Or become a world expert on a new technology that has yet to be invented. Such power comes with a price, though. You may also accidentally change reality so much that you cease to exist. Until recently, travelling through time has seemed little more than fantasy. But quantum theory and relativity open up ways to make time travel possible - and there is no physical law preventing it.

How to Build a Time Machine explains our best understanding of time and how it can be manipulated. We visit a time traveller's convention where no one turned up, and see why a time machine might not be able to travel back further than the point it was first invented. We explore the remarkable possibilities of real time travel that emerge from quantum entanglement, superluminal speeds, neutron star cylinders and wormholes in space. Then there's Ronald Mallett, a man who has dedicated his life to devising a way to travel back in time to meet his father, who died when Mallett was very young. We are finally ready to take on this ultimate challenge and see that a time machine may really exist in the not to distant future.

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Brian Clegg conjectures on the totally conjectural world of time and space travel and brings it all beautifully down to earth. Brilliant. Johnny Ball

This fascinating, complex, slightly frightening book begins with a sentence that makes you sit up rather quickly: “There is no physical law that prevents time travel.”.. It’s mind-scrambling stuff. A natural successor to the likes of Magnus Pyke or Edward de Bono, Clegg clearly appreciates that science is only as dry as the ivy-covered professors who make it so... as with the author’s delightful Inflight Science, most readers should find it thoroughly lucid and engrossing. Word Magazine (Ali Catterall)

British pop-science writer Clegg notes that time travel is not just a trope of science fiction any more. Increasingly, serious physicists accept that travel to the future and back, or to the past and back, is theoretically possible. The laws of physics provide a few interesting options, and examining them provides an opportunity to look at some interesting corners of modern science. Einstein's theories of special and general relativity describe how motion and gravity affect objects and people. Movement at high speeds, or in powerful gravity fields, changes the rate at which time flows... Clegg also dissects schemes such as going into the past and playing the stock market armed with foreknowledge of what will rise or fall. He covers most of the themes advanced by science fiction, plus some of the more adventurous scientific minds, generally avoiding math or tricky technical details. A solid overview of some of the quirkier corners of physics, with an entertaining connection to pop culture. Kirkus Reviews

Mr. Clegg, as a writer and not a professional scientist, prefers to focus on the human side of the quest to understand time, giving it equal billing with the scientific details and skipping the equations. His prose is sprightly, and most readers will be readily drawn into his examples from science fiction and anecdotes about the human side of science. We are told, for example, that Einstein was ordered by his doctor not to buy tobacco; interpreting this literally, Einstein simply filched the tobacco from his friend Niels Bohr... read "How to Build a Time Machine" to get some sense of the high stakes and exciting ideas that abound in this field. - Wall Street Journal (Sean Carroll)

An excellent overview of the scientific basis of time travel as well as the attempts both real and imaginary that have been made regarding time travel. - Professor Ronald Mallett, University of Connecticut

Clegg is both a writer and a physicist; and it's as a writer – one who is able to communicate physics to the non-specialist – and that makes this book so very enjoyable. The hard stuff is there, between the lines, but we're not asked to deal with it – Clegg leads us through, in his own inimitable style... Perfect. I'm sure I'll go back and re-read it. If only I had the time – or a time machine perhaps? Popular Science website (Peet Morris)

Physics indicates it may be possible to go back to the future, and in How to Build a Time Machine, Brian Clegg argues that it's never too early to prepare... New Scientist (Manjit Kumar)