Mike Bourke from Campaign Mastery has thrown quite a challenge for November’s RPG Blog Carnival: a sequel to a previous post. I’ve been procrastinating a sequel to an article I wrote long ago about time travel in RPGs, so it is a 2×1 double-fit for me. There’s one catch though: the original article is in Spanish, so I guess you’ll have to guess its contents if you’re not from an alternate reality in which you are proficient with that language. Just if you’re too curious, it was titled «Roleplaying Chronodynamics» and it deals basically with time travel and how the concept is difficult not only in science but also in RPGs. What I’ll do now is to review the last part of that article, talking about some of the ways time travel has been used in fantasy, giving you the pros and cons about each using one in your campaign.

Leaving aside the means by which time travel is supposedly achieved, we’ll be focusing instead on the different ways time travel can messup with causality within the universe of each story. Needless to say, there are spoilers ahead!

Let’s start with the most realistic approach. We can find this in Ender’s Game by Orson Scott Card. In this science ficiton novel, time travel is as realistic as current theories explain to us how time travel could work: characters experience slower passage of time when they travel close to light speed, allowing just a few days or months to pass for those traveling while years pass on earth or other planets. It’s traveling forward through time like we normally do, but at different rates (Einstein called this the «twin paradox»). This kind of time travel doesn’t change the past or allow characters to make different decisions than the ones they already did – after all, it only allows time travel forward: it’s all one consistent historical trajectory. The original Planet of the Apes film is very similar, where astronauts experience extreme time dilation and then crash land on a strange ape-ruled planet that turns out to just be the Earth in the distant future.

Let’s focus now in less scientific approaches. After all, we’re talking about Dungeons & Dragons here. If we’re going to travel in time, let’s make it worthy. There are two big distinguishing features between different types of time travel in fiction. The first is whether or not the time traveler is there when history happens the «first time around»: is there a kind of «self-consistency» where, since time travel takes you to the past, when the past happened the first time, the time-traveling version of you was always there to begin with? Or does the very act of time traveling to the past change what happened and force the universe onto a different trajectory of history from the one you experienced prior to traveling?. The second distinguishing feature is: how does free will work when somebody is time traveling? Whose actions are allowed to move history onto a different trajectory, and whose aren’t?

One of the simplest time travels is the «do-over», where characters can re-play history starting exactly as it was at a certain point, with the only caveat being you remember your experiences from already having tried various possible future timelines (while no one else does). It’s essentially like playing a video game where you can start a level over with the foresight of what you did wrong the first time. The best example for this is the «Groundhog Day», where Bill Murray’s character relives the same day over and over again, and though he can make different choices each time, he always starts back at the same point (except with new memories of his previous choices). That is, until he figures out the one exact set of choices that frees him from the loop. Technically speaking, «A Christmas Carol» fits in this archetype too, even though it may not seem like time travel. But because Scrooge gets to visit the future of his current timeline, even though he has no ability to affect the timeline directly while «visiting», he can still change his actions in the present based on what he learns, essentially getting a “do-over.”

And then we have time travel where the very act of going to the past or future creates a fully new trajectory of history because precisely by time-traveling to where you weren’t the first time around, creates a new version of history. This includes the typical «anything goes» time travel movies like «Back to the Future» and «Star Trek: First Contact», where you can kind of instantly jump back and forth to any point in time you want, potentially resulting in multiple versions of yourself. From a causality perspective, anything you do in the past (and even just the act of going back in time) redirects the course of history onto a new timeline: in «Back to the Future», Marty’s interference with his parents falling in love results in the timeline of history being redirected towards a version of the future where he doesn’t exist (and because of this, he starts to disappear from photos and real life). And even after correcting that major deviation, his interactions with his parents while he’s in the past result in them being very different people when he returns to his present time; he accidentally caused history to progress in a slightly different direction. The movie ”Looper» is similar, but there’s a little more circularity because when you jump to the past, you cause history to branch onto on a trajectory where, in the future, the younger you also goes back in time the same way you just did. Both you and your past self still have enough free will to change that forward course of history, though, which results in weirdness like you getting new memories when your past self does things you yourself didn’t do, or if they lose a body part, suddenly you’ll lose it too, replaced by an old scar on your own body. So, changes to the present affect not just future timelines, but also future timelines that wrap back around to the present.

And where fantasy meets logic, we find what is to me my favorite from all literary methods: the one J.K. Rowling uses in «Harry Potter and the Prisoner of Azkaban». It’s a kind of time travel that doesn’t actually generate any new timelines. It manages that because in this universe, while you were experiencing your initial, pre-time-travel passage through a particular point in history, your «time-traveling clone» (Ireally lack the creativity rght now to find a better name) was also already there, doing everything you’ll eventually do when you time travel yourself. In the novel, Harry is saved from dying by their time-traveling self the first time through that timeline. It makes so much sense – if you go back in time, you really and truly were present at that point in time all along! This also means that during the period of overlap, the time-traveling you has no actual free will, since everything you do has in some sense already been done, which Harry comprehends when he realizes he has to save his past self because he was already saved by his future self when he was in the past.

The best thing about this approach is that it is logically consistent: it’s time travel to the past where you can’t change the past, because the past already happened. And there’s only one timeline – the one in which time travelers arrive from the future, do stuff, and at some later date, leave to go to the past. Logical consistency lays the foundation for good time travel stories, but not because logical consistency is important in an of itself, but because, most of the time, in order to care about the characters in a story, we have to believe that actions have consequences. And this is super important to achieve in rolepaying games. If everything is just a meaningless series of events, then we almost don’t have a story and our actions don’t matter, so it’s really helpful if there are rules by which the universe of the story works, whatever those rules may be.

Well, that’s it for my sequel to the original «Roleplaying Chronodynamics» article (which is more than six years old by now). If you want to allow time travel in your campaign, I hope this insight will help you to reduce the probability of inconsistenciesand preserve your sanity, Novikov style.