Twice upon a time
Yes, well, we’d all like a do-over, especially knowing what we know from the first time, the second time. My life would be less fraught with disasters and bad decisions.
Of course, I’d be someone else. They say all this shit is character building and if that is true I now have a large enough character to launch low orbit satellites by dropping them off the top of it. Well, whatever. It may be that there an infinity of alternate universes just a hairbreadth of a dimension away (part of the foundation for the Karres books, which may be supposed to be pure space opera, but bits of science kept sneaking in), and given enough iterations, one where my chaos-prone nature didn’t result in character building. I’m not sure if it is nature or nurture, but it does seem to be me.
So: time and again. Time travel has been a staple of sf since… well, Mark Twain, I guess. I mean traveling to the future is in a couple of myths and of course the like of Rip Van Winkel – but traveling into the past (and changing it) seems to be later idea. I can’t offhand think of any earlier ones, but I may well just not know it or have thought of it. Some books have been fairly successful, but it is a cow for paradox (the old you went back in time and killed your own grandfather, so you didn’t live go back in time, so your grandfather lived, so you went back in time… I have this mental images of versions of the universe winking on and off in an endless loop.
There tend to be two versions of ways to get around this: either the past reflects the effect of the time travelers (Spoiler: See Harry Harrison’s ‘Technicolor Time-Machine – and that’s the punchline to the whole book) or, more popularly the time traveler changes the future… but it is not his future (the multiverse concept, with breakpoints engineered in this scenario, by the activity of time traveler. Of course the latter has the fascinating dichotomy – can one person change future history, or is history ‘self-healing’ (you travel back in time to stop Archduke Franz Ferdinand being assassinated by Gavrilo Princip, to stop World War 1… and because that was merely a trigger to an unstoppable chain of events, something else promptly triggers the same chain, and, looked at from 500 years hence, ye Time Police arresting the time-traveling perp, discover that actually there is almost no difference as consequences.) It’s the sort of stunt you can pull once as short story, but really most time-travel sf tends towards the former. I have a feeling that the best scenario (for the writer, because it allows you to ‘borrow’ the plot from history) is that one person can make changes – but that history would trend slowly back to what we know. YMMV.
Of course the idea that we can see the past but not change it has been used too – as has the fact the past is a microsecond ago. (I am trying to remember the name of that story. Anybody help?)
Of course, there is travel into future (and sometimes back again, a la DOOR INTO SUMMER).
Or stopping time for everyone but the character (A favorite of mine: THE GIRL, THE GOLD WATCH AND EVERYTHING, and as part of various DISKWORLD novels.)
And then there is the idea in James White’s TOMORROW IS TOO FAR with travel in time being also, obligatorily travel in space (a fascinating idea I toyed with, once again in one of the Karres books, but I haven’t seen elsewhere).
Time travel does however seem to have largely been displaced by Alternate History.
But, because sf trends are rather like fashion, recurrent if not absolutely circular, maybe its time is coming again.