La Jetée (1962) dir. Chris Marker
Time travel is a popular device among sci-fi writers, and have often provided a glance at possible utopias and dystopias. So, for this entry in my 45.1 Dystopias series, I'll forgo the usual political analysis and focus on the time travel plot device in La Jetée.
Throughout the history of film and literature, only a tiny number of works on time travel have attempted to portray a realistic outcome. La Jetée is one, and derives its power from its crushing logic.
The Block Model
It seems useful to imagine time as a 4th dimension. So if Davos is in Paris in 1962, we can describe his latitude, longitude, altitude and year as (+48.86, +2.35, 130, 1962).
We are all moving through the 4th dimension, but only in 1 direction and it is difficult for us to significantly increase our relative speed. Causality seems to hold up in all circumstances thus far tested. What I do at (+48.86, +2.35, 130, 2010.8) will affect (+48.86, +2.35, 130, 2010.9), similar to how adjacent events and objects along the X, Y and Z axes affect each other.
In La Jetée, Davos is a child on the pier at (+48.86, +2.35, 130, 1962.0) where he sees the woman and sees a man killed. War breaks out, and he is a prisoner underground at (+48.86, +2.35, 130, 1982.1). Through the experiments, he jumps back in time to (+48.86, +2.35, 130, 1960.8). Then, he travels to (+48.86, +2.35, 130, 2101.5) to visit the advanced humans.
The 2101 Parisians are reluctant to help the 1982 Parisians. But, Davos reminds them that "because humanity had survived, it could not refuse to its own past the means of its survival."
Davos is technically wrong, but he is basically right. The fact that humans exist in 2101 proves that they do not go extinct before that date. It doesn't matter why they don't go extinct - we just know for a fact that they don't.
(It does seem to create a closed time loop. They seem weird, but as long as they're consistent, they're not any weirder than the closed loop of existence itself.)
Davos then brings the new energy core to (+48.86, +2.35, 130, 1982.1) and is sent to (+48.86, +2.35, 130, 1960.0) as an adult, where his child self sees his adult self killed.
The narrative problem with this block model is that it appears to be a fatalistic world. "There was no escape from time."
You can't go back in time and kill Baby Hitler. You can try, but we already know you fail. If you succeeded, the Holocaust wouldn't have happened, but we know it did. Furthermore, you wouldn't have reason to go and kill Baby Hitler anyway.
The anxiety time travel movie characters have about "changing the past" or running into their past selves is ridiculous, especially in a block model. We already know you didn't change the past. And if you ran into your past self, you'd already know about it. You don't have to worry about accidentally killing your infant grandfather, because there's no way you did so.
Personally, I don't think that foreknowledge changes anything about the determinism v. free will argument, but that's far from a settled philosophical question.
Anyway, it's not a relevant one. In a block model time travel movie, the problem isn't that the characters know what's about to happen, but that the audience does. Greek tragedy doesn't play well to modern Americans.
The 5th Dimensional Model
Time travel fiction typically avoids fate by introducing a 5th dimension. Alternate, parallel universes or histories exist.
Easy enough to imagine. A mainstream interpretation of quantum physics suggests that an infinite number of alternate universes or timelines exist, each with one of an infinite number of permutations.
The time machine doesn't just travel along the 4th dimension, but along the 5th as well. Personally, I find this to be a much more impressive technological feat than time travel, but most fiction doesn't dwell on this aspect.
So, let's say I am an Austrian, living in 2010, in our own alternate reality. My coordinates could be (+48.15, +13.20, 351, 2010.8, 1). I decide to go back in time to kill Baby Hitler. I hop in my machine, and visit (+48.15, +13.20, 351, 1889.3, 2).
I snatch little Adolf from his mother's arms and toss him in the river. Job done, I hop back in my machine. What have I accomplished?
In universe 1, Hitler grew up to lead the Nazi Party and cause the Holocaust. I accomplished nothing. The 12 million universe 1 people still died.
In universe 2, I did save millions of lives. But if we're talking infinite universes here, I'm not sure I 'changed' anything either. Universe 2 was/is/will be always only one of the trillions of infinite universes along the 5th dimensional axis where the Holocaust didn't happen. If every possibility exists, there's no possibility to change any one possibility.
Our choices in this infinite universe model don't change the world - they simply reflect whichever world we happen to live in.
Its really just the block model with a whole bunch of blocks. The activity of travel between different universe blocks only increases the number of permutations in an already infinite set.
From a practical narrative standpoint, what coordinates do I set my machine to after drowning Baby Hitler? At (+48.15, +13.20, 351, 2010.81, 1), there will still be a Holocaust Museum. At (+48.15, +13.20, 351, 2010.81, 2) the me born in universe 2 will co-exist.
Ignoring It All
The overwhelming majority of popular time travel fiction - Back to the Future, Primer, etc. - doesn't follow either model. Or rather, it follows both models.
Sometimes time travel exists in the same universe, and Marty can co-exist with himself. Other times, time travel brings Marty to a different dimension, where he has "changed the past," relative to his memory. These instances are especially odd, because universe 2 Marty mysteriously disappears just before universe 1 Marty shows up.
We've got 9 different universes on the 5th axis, and you may notice some rather odd things. Sometimes time travel brings you along the same universe, and other times it doesn't.
Time travel is the least of the things this accidental device can accomplish. Entire universes are occasionally created ex nihilo, depending on nothing other than whether the plot requires it or not. Peoples' memories are patched over onto new-universe clones, in an Omphalos-style creation. Randomly, Aaron and Abe were sometimes born in these new universes, and sometimes they were not, but everyone acts like they were anyway.
Most popular time travel fiction simply doesn't make sense.
Now, there's no need to get pedantic about it. The rules don't really apply to fantasy like Groundhog Day or A Christmas Carol, and soft sci-fi like Back to the Future aren't intended to pass logical rigor.