The thread on The Terminator in Cafe Society reminded me of something that’s bothered me for a long time.
A scenario:
John is a scientist, and also a baseball fan. In 2027 he goes to a major league game where he finds himself sitting next to Mary. They talk, start dating, and in2030 they get married.
In 2032, Mary dies. Grief-stricken, John throws himself into his work and invents a time machine.
Being a sentimental guy, John decides on what would have been their 10th wedding anniversary to go back to that ball game in 2027. There is little risk of running into himself, since he gets a seat on the other side of the stadium. He uses binoculars to watch that magical moment in which they met.
That was so special to him that in 2045 he decides to do it again on their 15th anniversary. How many Johns would be in the stadium that day – just 2027 John and 2045 John, or would 2040 John also be there? Might there be more Johns there? Might the 2040 John at the stadium also go back in 2045, making there be two 2045 Johns there?
It really depends on what “rules” you set up for time travel, but I would say both 2040 and 2045 John would both be there. It’s like in Back to the Future 2, where there’s 2 Martys in 1955.
It didn’t involve time travel, but a particular Calvin & Hobbes story arc had him duplicating himself 4 or 5 times and they end up beating each other up while the tiger says Wow! how existential can you get?
The 1973 book The Man Who Folded Himself is about a guy with a time machine who jumps around to various times, encountering numerous different versions of himself. At one point he sets up a party which is attended by dozens of iterations of himself from the past and the future. He also has sex with other versions of himself. I’ve never been sure if that act should be called “masturbation” or something else.
There was a short story about a guy who discovers time travel, and eventually decides that this one particular year is the best year ever, so he just keeps repeating it. Every New Years, he goes to the same bar, and all the iterations of himself celebrate before jumping back in time. Half-way through the evening, a girl walks into the bar, and he ends up dating her, and then she starts showing up with the older versions of himself.
Sheldon: Marty and Doc never had have had brought the time machine to 2015. That means 2015 Biff could also not had have had brought the almanac to 1955 Biff. Therefore, the timeline in which 1955 Biff gets the almanac is also the timeline in which 1955 Biff never gets the almanac. And not just never gets. Never have, never hasn’t, never had have hasn’t.
Robert Silverberg in his novel Up the Line talks about Time Travel Tourism, and about how some critical events in history – the Crucifiction of Christ is the real Big One – are heavily overpopulated by Time Travelers who all want to be there. The outfits running Time Tours try to limit attendance at such crucial events.
In The Hitchhikers Guide to the Galaxy, they talk about a guide to grammar for time travelers. “Will have haven’t had” and such. They note that later editions of the book save money by leaving most of the pages blank, because no one in history every managed to read further than the first chapter.
It is quite impossible for us to know. We do know, based on the information you have provided, that there will be at least three Johns there; the 2027 version that met Mary, the 2040 version that first went back to watch the first meeting, and the 2045 version.
However, John as of 2045 does not know if future Johns have also travelled back in time. Assuming there is no limitation on use of the time machine, John after the 2045 anniversary could have gone back every year for thirty years, or every DAY for thirty years; the stadium may be teeming with Johns, presumably wearing disguises. The 2045 John can only be sure there are at least three, including himself, but cannot know for sure if there are more. In 2045 he might have resolved not to go back again, he cannot know, as of the 2045 anniversary, that his resolve held out.
This was also true in 2040; the original, 2040 and 2045 Johns are all there. The 2040 John does not know the 2045 John is there, but he is. However, the 2040 John also has no way of knowing if the only Johns there are the ones he is sure about, or if there are scores of them.
C. L. Moore’s novella “Vintage Season” from 1946 is the first classic about time traveler tourism. It definitely influenced Silverberg’s book. In fact he wrote a sequel to the story, “In Another Country” in 1989 that was printed with “Vintage Season” in 1990. Apparently the 1992 movie Timescape was also based on the story.
John Kessel’s Corrupting Dr. Nice is another important novel about time travel tourism, although his travelers create their own alternate histories that preserve the narrative we know.
True. I first read “Vintage Season” in the anthology The Science Fiction Hall of Fame. But, to my recollection, although it was about time travelers going to “preferred” times and places, they weren’t flashy critical historical events taking place in them – they were just “vintage” spots in Space/Time. So you didn’t have the problem of overpopulation at popular spots, and they never discussed that.
Timescape was indeed based on the Moore story (I have a copy on DVD), but, as they did in adapting Mimsy were the Borogoves into the movie The Last Mimzy, they changed the ending to something – less threatening and more happy!
That is a hard nut to crack for a translator. German just about works, Spanish has me scratching my head.
I see by the answers so far that Stanisław Lem is not much known in the USA, that’s a pity. Just google “Ijon Tichy Series by Stanisław Lem” and enjoy. Stanisław Lem in general is most amusing, but his time travel paradoxa are hilarious.
The Man Who Folded Himself by David Gerald deals with this. There is a time and place where all versions of himself from all times and genders hang out.