One hundred – fourteen years ago, in 1895, the H. G. Wells classic story, “The Time Machine,” was first published in book form. As befits the subject matter, that was minus tenth anniversary of the first publication, in 1905, of Albert Einstein’s special theory of relativity. It was Einstein, as every schoolchild knows, who first described time as “the fourth dimension” – and every schoolchild is wrong. It was actually Wells who wrote, in The Time Machine, that “there is no difference between Time and any of the three dimensions of Space, except that our consciousness moves along it.”

Since the time of Wells and Einstein, there has been a continuing literary fascination with time travel, and especially with the paradoxes that seem to confront any genuine time traveller (something that Wells neglected to investigate). The classic example is the so- called “granny paradox,” where a time traveller inadvertently causes the death of his granny when she was a small girl, so that the traveller’s mother, and therefore the traveller himself, were never born. In which case, he did not go back in time to kill granny . . . and so on.

A less gruesome example was entertainingly provided by the science fiction writer Robert Heinlein in his story, “ By His Bootstraps (available in several Heinlein anthologies).” The protagonist in the story stumbles on a time travel device brought back to the present by a visitor from the far future. He steals it and sets up home in a deserted stretch of time, constantly worrying about being found by the old man he stole the time machine from — until one day, many years later, he realises that he is now the old man, and carefully arranges for his younger self to “find” and “steal” the time machine. Such a narcissistic view of time travel is taken to its logical extreme in David Gerrold’s The Man Who Folded Himself (Random House, 1973).