Monday, 31 July 2017
A temporal round trip would be "then and back again," as in The Time Machine by HG Wells or in "Flight to Forever" by Poul Anderson. To be complete, such a round trip should return the time traveller to the moment of his departure whereas the Time Traveller re-enters his nineteenth century laboratory several hours after leaving it although he had spent several days in the future.
Did Wells and his earliest readers simply assume that a return must happen after a departure or did Wells deliberately avoid the obvious paradoxes: could the Time Traveller have returned in time to see his younger self departing? Could he even have prevented that departure? Can a younger and an older Time Traveller coexist and converse? The story is tantalizing for the questions that it implies but does not ask.