Time Travel

The current popular science literature is rich in examples of this craze. A recent one combines free trips backwards in time with the marvels of quantum computing. This is the book of David Deutsch (The Fabric of Reality, Allen Lane, Penguin, 1997). You can travel all over time taking in a few different Universes along the route! A more "serious" excursion of the same genre was published in the New Scientist on April 1st, 1996 (very appropriately, since in England that day of the year is called All Fools' Day), when the editors of that journal announced that Professor Gunther Nimtz had transmitted Mozart's 40th Symphony over a distance of about ten centimeters at a speed double that of light. What they meant was that some of the (mythical) photons, which are alleged to be carrying this musical message, travel faster than light. It is a consequence of Einstein's Principle of Locality that nothing goes faster than light, and Einstein introduced this principle because he was the first to prove that going faster than light was equivalent to going backwards in time.