It is driving you absolutely mental, this whole time paradox business. You lie awake nights wondering what would happen if you hopped into a time machine and went into the past and killed your own grandpa when he was a child. Because, as you well know, if you offed gramps he would never beget your father and if you father were never begotten he would never beget you and if you never existed you couldn’t kill your grandpa…
We may have a (kind of) answer for you. It is supplied by the professor who also supplied the grandpa hypothesis above. His name is David Kyle Johnson and he offers a course entitled Exploring Metaphysics, available from the Teaching Company’s Great Courses, which you may not have known, but you do now. Professor Johnson’s solution to the offed grandpa poser, which even he admits is a bit of a cheat, is that maybe your time machine (which probably doesn’t come with a warranty) not only carries you into the past, but also takes you into an alternate universe that is an exact duplicate of this one up until you began your temporal jaunt. So the gramps you might kill is not precisely your grandfather, but an exact copy of your grandfather, only in another universe. This, of course, leaves that universe’s version of you born and, presumably, able to do some grandpa hunting of his own. Will it never end? Well, that’s not our problem.
You’re probably familiar with the notions of both time travel and alternate universes, but you may not realize how far back they go. Time travel, for instance: you may think the first story involving that was H.G. Wells The Time Machine, first published in 1895 because… well, we’ve all seen the movies. (Okay, nitpickers, it was actually several movies.) But not even close. You could argue that the first story about someone moving forward in time appears in Hindu mythology and concerns a guy who went to heaven where he met the god Brahma and finds that when he returns to Earth ages have passed. We could date backward time travel fiction to Memoirs of the Twentieth Century, which appeared in 1733 and relates the doings of a guardian angel who brings state documents from 1998 to 1728.
On to the alternate universes trope. This probably hasn’t been used as story fodder as much as time traveling, but it, too, has a long ancestry, especially if you include stuff that appeared as “alternate history.” Let’s agree, for now, that alternate history fiction began with a story in which Alexander the Great went west instead of east, written in the first century CE by the Roman historian Livy.
Some of you may have fallen asleep a paragraph or two back, but for the rest… we may return to these matters next week. Of course, we’re speculating about the future here and… you just never can tell.