An easy way to solve EVERY time travel paradox

Time travel paradoxes. They can trip up any sci-fi fan who spends even a few seconds thinking critically about such acclaimed classics as Back to the Future, The Terminator, and even Harry Potter.

Time travel paradoxes come in many forms, but usually revolve around characters doing something in the past that necessarily influences their future self who decided to mess with the past in the first place.

Or they do something that changes the past, which would change the course of their life, thereby making it impossible for them to have ever traveled in the past in the first place to fix it.

Or crazier still, characters often just don’t think of time as fluidly as they could, so even if they could avoid paradoxes, through a lack of imagination, they fail to solve their own problems. Skynet needs to kill John Connor, as he’s part of the Resistance. So they send a Terminator back in time to kill Sarah Connor. Simple enough.

But when they fail, they send a second Terminator, not to kill Sarah Connor, but to kill 12-year-old John Connor.

And then in T3, they send a Terminator to kill adult John Connor. Why not kill baby Sarah Connor instead of dealing with a John Connor who is increasingly becoming more like the John Connor that is leading the Resistance?

You know all about time travel paradoxes: let’s solve them once and for all! In this article, I’ll share with you my own strategy for resolving any time travel paradox in fiction.

Reliance on headcanon

As a ground rule, this strategy relies on headcanon. Canon, of course, is the “official” facts and laws that make up any fictional universe. Canon typically consists of the published movies, books, comics, video games, etc., in a given fictional series. Fan-made material and unlicensed spin-off products (or just poorly conceived spin-off products) and typically NOT canon.

Headcanon, though, is the canon you carry around in your head. It’s not official, nor endorsed by the authors or creators of said fictional work. It’s your own determination about what is “true” and what is “not true” about a fictional world.

So if you’re courageous enough to fill your head with your own canon surrounding fictional works, let’s dive in!

The Dark Tower’s approach to time travel

The Dark Tower series by Stephen King is one of my favorite fantasy/sci-fi stories, and it has a unique approach to time travel that I haven’t seen replicated in other fictional works involving time travel. I’ll start by sharing King’s view of time travel, then use that as the basis for my own theory of time travel.

In the Dark Tower, our heroes travel between worlds, most notably the Western-fantasy world of Mid-World and our modern, present world—the world you and I live in right now! In the modern world, our heroes travel to several different versions of the world in the 1960s, 1970s, 1980s, and 1990s. This opens up all kinds of time travel paradoxes, right?

King flips the time travel formula on its head by establishing one important fact: one world, our world, is the keystone world. This is the real world, the true world. All other worlds, including Mid-World, are pale imitations of the real world.

What makes the keystone world different than all other worlds? One thing: time travels in only one direction in the keystone world.

Our heroes travel back and forth through time, but only to a limit. The keystone world ever marches forward, and once a time period has passed, there’s no recalling it. If you want to save the world, and permanently alter it, you have to do it in the keystone world, not the other worlds.

The keystone world eliminates most time paradoxes. Because time only goes in one direction, the time travel doesn’t have to worry about changes in the future affecting changes in the past: there is no past.

All possible worlds exist on the normal curve

King’s view of time travel is close to solving time paradoxes, but it raises other questions. If the keystone world is the only one that matters, then does it make any difference what one does in the other worlds? Can a time traveler’s actions in other worlds even affect the keystone world?

If they can’t, then time traveling is a fruitless endeavor. It should instead by seen as traveling to parallel universes, not traveling in time.

The many-worlds interpretation posits that all possible universes are real. While I don’t give this theory much credence in the real world, I do think it’s acceptable for sci-fi to explore the many-worlds interpretation.

While traveling to alternative universes makes for some great storytelling, it eliminates the intrigue of time travel. The attraction of time travel is that the time traveler can actually change history, in their own world. To explain away time travel as simply travel to an alternative dimension, a dimension that “appears” to be the past but really isn’t, is a cheat.

Is there a way of reconciling time travel with the many-worlds interpretation? I think there is, and this is where my faith is restored in time travel fiction.

This headcanon strategy starts with the keystone world. Assume that in the fictional universe there is one true world, a world were time travels forward, not backward.

For the Terminator series, then, this explains why Skynet couldn’t send a robot backward farther in time after it failed to kill Sarah Connor: the moment had already passed.

Second, this headcanon strategy assumes that the many-worlds interpretation is true. However, not all worlds are equally likely. Some are more likely than others. All possible worlds can be fit to a normal curve as follows:

Image courtesy of the Oxford Math Center.

Image courtesy of the Oxford Math Center.

This is a probability curve. It’s pretty easy to read. Points close to the center are more likely, or probable, then points farther from the center. The normal curve appears all over the place in nature.

Height is a great example. Most adults fall within a standard range for height: let’s say 5-6 feet. Of course, other heights are also possible for adults, like 3 feet or even 9 feet. But those heights are very improbable and those data points exist at the outliers of the curve.

This same idea, then, can be applied to alternative fictional worlds. Most alternative universes will be very similar to the keystone world. It’s possible that there’s an alternative Terminator universe were Terminators are dinosaurs, rather than machines. But this is very unlikely.

Influencing the keystone world

So far, I’ve posited that there’s a keystone world, a la Stephen King, where time only goes forward. Second, every possible universe exists, but they exist along the normal curve, meaning most alternative worlds will be very similar to the keystone world.

The final part of the strategy involves the element of agency. If alternative worlds exist, then how does time travel make any difference? If characters travel to an alternative world and effect change, what consequence does that have on the keystone world?

Simply: the closer an alternative world is to the keystone world, the greater effect each world has on the other.

Skynet’s self-awareness exists in an alternative world, one very close to the keystone world. In the Terminator franchise, the primary world where we meet Sarah Connor and John Connor is the keystone world: time only goes forward. The world of Skynet is very close to the Connor’s keystone world, so it has a great effect on it. But the effect is not absolute.

When the Terminator leaves the Skynet apocalypse world, they enter the keystone world. When Sarah Connor kills the Terminator, her actions have a strong ripple in the alternative worlds closest to the keystone world, including the original Skynet self-awareness alternative world.

Thinking of alternative worlds as having consequence in the keystone world, then, gives the time traveler some agency. If the time traveler makes major changes in an alternative world, then it’s likely that some of those changes will carry over into the keystone world.

But all those changes might not hold, especially if time has already moved on in the keystone world.

To summarize, you can solve all time travel and dimension hopping paradoxes—and make your fictional works that much more enjoyable!—by following a simple strategy:

  1. Create your own headcanon for that fictional universe.
  2. Designate one of the timelines in that fictional universe as the keystone world, the one true real world where time only moves forward.
  3. Accept that in the fictional universe, all alternative universes are possible, but these alternative universes fall along the normal curve.
  4. The time traveler/dimension hopper can most affect the keystone world when s/he makes changes to worlds most similar to the keystone world, and changes in the keystone world most affect alternative worlds that are already similar to it.

With this strategy, I can now enjoy any time traveling fiction without worrying about pesky paradoxes. No need to let a little rationality ruin otherwise compelling stories about heroes traveling through time to make a real difference in their world!

Feel free to share your time traveling thoughts on this Back to the Future Day!

See you in the future,

2 thoughts on “An easy way to solve EVERY time travel paradox

  1. I think this is much better than my strategy, which is to just enjoy the story. You can enjoy the story even more this way.

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