Temporal Based RPGs

[virgil]

I have a germ of an idea on time-travel and temporal magic in an RPG, but I think too much sometimes. For awhile there, I've considered the most satisfactory explanations of time-travel to use loops (where time-travel is already within the chain of events). However, I've been thinking and realized there's what's called a Ontological Paradox with that, and now I'm rethinking the whole concept again.

Are there any good RPGs that handle temporal mechanics in a satisfactory manner? Heck, what would satisfy me?

[IGTN]

You can just accept that such paradoxes happen and deal with it, although that might damage the tone of your game.

You can also try to use differing timelines, but that might not be satisfactory; that only lets you visit the past, but not change the present with it.

I'm not entirely sure if there is a good way to do time travel that does everything that people expect of time travel and doesn't create paradoxes.

There's also the approach where, as soon as time travellers look away, the timeline starts doing contrived things to put everything right, with some upper limit on how contrived.

Possibly also make it so that relevant people (PCs, villains, etc.) be immune to time-travel; that is, they are always born regardless of what happens in the past, or, if that is impossible, they spontaneously generate, and always remember their "true" past, even if someone changes things up. If a villain goes back in time so that Hitler wins world war 2, the PCs, because they're special, know how things are supposed to be (and, possibly, everything they should know from growing up in a changed world. Of course, if their grandparents died in the war, then they didn't grow up in the Nazi timeline and instead spontaneously generated into it, and so don't get those memories).

[angelfromanotherpin]

Are there any good RPGs that handle temporal mechanics in a satisfactory manner? Heck, what would satisfy me?

Use probabilistics instead of absolutes?

In the GURPS time travel setting, the present that the PCs come from is not the present, but merely a highly-probable present. They contest with time travellers from an alternate highly-probable present in a history-nudging game to make each other less probable. The math shows that when a timeline becomes insufficiently probable, it loses access to time-travel, but it never fades from existence entirely due to really low-probability events like thermodynamic miracles which could cause it to exist no matter what.

[ludomastro]

Don't know how much of a fan of handwavium you are; however, you could use the concept of some moderating force like galactic time police or an alternate person filling the same role.

Scenario:
The PCs try to knock off Hitler before he can launch WW2.

GTP Answer:
Aliens, men from the future, angels, whatever step in and prevent the PCs from doing so with a curt, "It would make things worse in the long run."

Alternate Person:
Hitler is "removed;" however, Himmler takes over the Nazi movement and the same things (98+ % anyway) happen.

[Cynic]

I've run two time-travel related games so far. One of which, you (Virgileso and not the collective you of TGD*) were a part of.

The problem is not that ontological paradoxes exist but that no matter how much you try to keep them from happening, your own players will bring them up.

If you are hell-bent on a time-travel game, I think it's okay to leave the paradox in. It makes it hard to keep things straight so you'll need a lot of notekeeping if it's a long-term game.

[Username17]

There are many versions of time travel, and the Free Lunch Paradox is only a paradox in some of them.

Self Regulating Time

• In a self regulating model, there is only one time stream and its past and future are intimately connected. If you go back and change the past, then in an amount of time it takes to get from that past to the present you came from, your history and your time travel decision will be different, which in turn will change the past. Even though the actual time traveling takes real time, the loop will play itself out an infinite number of times before a stable future will result meaning that the future from your time travel jump will always be from a history where your time leap caused the past that caused your time leap. In practice this means that you can change the past, but in doing so you will change yourself into something that genuinely experienced and caused that very past to occur.
  
  There is no "ontological paradox" in this model because the final stable result is the result of perhaps millions or even trillions of iterations of time overwriting themselves. So even if you can no longer see the origins of an idea or force, they did have one.

Immutable Time

• Kind of like a self regulating model, save that the time loops were already predestined before hand. Not only did every time traveler cause their own history, but even this history was written long before they're time distortions. This is the logical extension of hard fatalism.
  
  There is no "ontological paradox" in this model because the skein of time exists immutably in both directions from beginning to end. Nothing truly has any causes or effects because the time stream never changes nor alters its path for anything. If an item or idea exists in a closed loop of time in the middle and does not extend to either extreme that's fine, because that is just as arbitrary as any of the other fixed positions that any other items and ideas have in the unchanging fate that the time stream represents.

Dimensional Time

• In a dimensional time model, time is just a direction, and your place in time is literally a place. If you pick up and hop to a different place in time then that is your present and what happened in your subjective past is now an unknowable future. In this model, virtually any mucking with the past at all will render your future impossible to visit. The history you remember is destroyed past the point where you altered it meaning that your subjective origins no longer exist anywhere in time. If you return to your home date you find no home for yourself there. Your house will have another living in it if it even exists at all.
  
  There is no "ontological paradox" in this model because an item once moved is now placed in its current position rather than continuously and magically tied to an arbitrary past. Thus an item brought in from a forgotten and overwritten future may appear as an orphan, but its own subjective history has not changed for it. The events that pushed it to its state will never be experienced nor were they experienced by anything else in the universe, but the cause effectively remains exactly what it always was.

---

Now as it happens, the third option is really obviously how physics actually works. After all, if you move really fast you physically experience less time. Meaning that when you return home everything around you is from the fucking future and nothing ceases to be or really gets hung up about that fact in any way, shape, or form.

Whether you can actually move physical objects backwards in time or not is an open question. Honestly, it really sounds like it's running right into Conservation of Mass and Energy, which is a huge no no.

-Username17

[Manxome]

"Dimensional Time" (as you described it) sounds like it only really works rigorously if you presuppose some sort of meta-time. If you go back in time, and change things such that your future self never decides to go back (or never exists at all), then your subjective past no longer objectively exists in the timeline, so unless there's an alternate timeline or meta-timeline from which you came, then from the perspective of the universe, you just popped in out of nowhere with no cause and remember things that never happened. You're treating time like a spatial dimension, but then you are also supposing that you have something else that behaves more like a traditional conception of time.

If you're telling a story, of course, you always have meta-time, which is the narrative, so that can work really well, but I don't think it actually resolves the paradox from a physics standpoint. And consequently, I think you are severely overstating the case for this being "really obviously how physics actually works." Feel free to correct me if I'm wrong, though.



I feel compelled to give a shout-out to Charles Stross' Eschaton series, even though it's similar to what ludomastro already covered. Basically, lots of people have access to technology that would let them go time-traveling, and the reason the timeline isn't all mucked up is that there is a transcendent godlike supercomputer (called the Eschaton) that will smite you if you do anything that would violate causality (it doesn't want anyone endangering its own existence). And it sends messages back in time to itself, so you can't surprise it. But this doesn't work if you want to run an actual time-travel campaign, because you don't actually get to time travel. Civilizations that try are known to experience everything from suspicious equipment failures to giant asteroids hitting their planet.

[virgil]

The 'really obviously how physics actually works' only applies for going forward at varying speeds in comparison to some reference point. One of the very real rules of physics is the speed of light, which is not just energy/mass, but information as well; and breaking 'that' rule allows for traveling backwards through time.

Before you try to counter my statement with references to known experiments that have exceeded the speed of light in some fashion, those are special cases and they're not capable of transmitting information faster than light speed.

Ugh. Consistency in a game just melts if I try to think of a model that allows time travel at all. Metatime could potentially work, but it will ultimately place the players above the setting in a fairly detached way, at least the part that can be messed with, temporally.

[Ice9]

http://www.animationarcade.com/animation/timefight.html

This is the kind of stuff you're dealing with if you give out full short-range time travel. Great to watch, but that's because the animator figured out the convolutions beforehand. In play, I imagine a lot of replaying the same round would be needed.

[ludomastro]

Ice9 has it right. The video was awesome but I can't imagine how that would work with any coherent set of rules.

[Manxome]

For some reason, that movie reminds me of one game I played with an item called the "time keeper" that froze the user for a small length of time, and then let him act for the same amount of time "instantaneously" while the rest of the world was frozen. Unfortunately, the game got dropped before we got to do much with it.

Anyway, if you want to do actual time travel in your game, you're limited by two major real-world constraints:
1. Out-of-character, your players know everything that has happened in the narrative up to the current point, whether you want the characters to have that knowledge or not.
2. Since you don't have actual time-travel available to you for purposes of running the game, you can't narrate effects of choices the players haven't made yet, no matter how much you want to.

So here's one possible mechanic you can use:

Countably Infinite Timelines:
There exists an original timeline (call it T0) which is how things play out without any effects of anyone or anything traveling backwards in time. From the perspective of this timeline, anyone that tries to go back in time seems to simply disappear, and the universe continues on its merry way. (This probably means that not too many people try to go back in time, and that anyone who does so thinks he's the first person ever to succeed.)

However, there is another timeline, T1, which is where you actually go if you're living in T0 and try to go back in time. T1 looks like T0, except that everyone from T0 who "goes back in time" actually ends up in T1, with all the effects that entails. So T0 and T1 are exactly the same until the first time-traveler arrives, and then they diverge, but you can't create any paradoxes, because everyone who arrives "from the future" is actually arriving from T0, not T1, so there is nothing you can do that will alter or prevent their arrival.

Similarly, everyone in T1 who "goes back in time" ends up in another timeline, T2, which looks exactly like T0 except it gets all the people who left T1 to try to change the past. This includes all the people who were originally native to T0, but who tried to time-travel twice.

This has the possibly undesirable effect that, if the BBEG goes back in time, the PCs can avoid the effects of everything he does "in the past" by simply not following him. But if they ever have to time-travel for some other reason, the fact that they didn't follow him back and stop him will come back to bite them. And the players don't necessarily have to know that these are the mechanics you're using.

Additionally, there's no reason for the players to start in T0. They actually start in TN, where there have already been some unknown number of iterations, and the DM can write in any NPC time-travelers he wants.

There is no way for a higher-numbered timeline to affect a lower-numbered one in any way, so there are no paradoxes, and everything can be resolved linearly (you technically need to resolve T0 through the end of time to make sure that there are no more jumps into the stretch of T1 you care about, but that can be hand-waved, especially if players are trying to prevent some cataclysmic event like the end of the world). Of course, you can still get things that look like time loops, if several consecutive timelines are similar enough, but that's probably a feature.

[Username17]

I don't see why you'd need meta time. The "current" future can send anything it wants to the "present", and in doing so, the present will change and there will be a different future that is given that same opportunity. But the current group of time manipulators will have the opportunity to actually have enough to work to get to the future before the new future has the choice to send travelers back. So you wouldn't get fractal invasions where a million futures modified only by a fraction of a second of time traveller interference converge. But you could easily get a situation where a key event had a large number of interested parties at various times in future history who wanted to change it would all show up and fight - creating new futures that had more interested parties. Kind of like the 1980s really.

So yeah, each time orphan would be greeted by other time travellers from a future that was the result of everything he would have done if he hadn't met the subsequent time orphans. And then his actions would be different and the two groups of time travellers would both be orphaned in time.

-Username17

[ludomastro]

If you wanted to have some degree of time travel without all the problems, you could the temporal manipulation to bullet time a la The Matrix and a round or two of time re-wind a la Prince of Persia and other games.

[Bigode]

If you wanted to have some degree of time travel without anything interesting from actual time travel stories, you could the temporal manipulation to bullet time a la The Matrix and a round or two of time re-wind a la Prince of Persia and other games.

Fixed.

[ludomastro]

Well, that is one way of looking at it there, Bigode.

It is simply easier from a rules perspective.

[zeruslord]

In most stories, the interesting part comes from the paradoxes and changing of the future, and you lose that if you remove it. How many time-travel stories have you read where no paradox comes into play and the main characters can't meaningfully change the future?

[Manxome]

I don't see why you'd need meta time. The "current" future can send anything it wants to the "present", and in doing so, the present will change and there will be a different future that is given that same opportunity. But the current group of time manipulators will have the opportunity to actually have enough to work to get to the future before the new future has the choice to send travelers back. So you wouldn't get fractal invasions where a million futures modified only by a fraction of a second of time traveller interference converge. But you could easily get a situation where a key event had a large number of interested parties at various times in future history who wanted to change it would all show up and fight - creating new futures that had more interested parties. Kind of like the 1980s really.

So yeah, each time orphan would be greeted by other time travellers from a future that was the result of everything he would have done if he hadn't met the subsequent time orphans. And then his actions would be different and the two groups of time travellers would both be orphaned in time.

-Username17

You sound like you're actually describing something like Self-Regulating Time, except where we (the people listening to the narrative) actually see each of the iterations play out until we reach a self-consistent one, rather than jumping straight to the end state. And since that's only a narrative difference, it's not actually a different mechanic from the perspective of the universe. Though I could also still be misunderstanding your explanation.

Take this example: you go back in time and meet your past self. In scenario A, your past self does the same things that your future self remembers doing, eventually traveling back in time to meet himself again. In scenario B, something happens, the future plays out differently, and you never travel back in time.

Most time travel stories would interpret scenario A as consistent and concluded, with your past self becoming your future self, but scenario B as requiring the narrative to go back and watch events play out differently, because now your past self will never meet your future self. If you want to take the position that exactly one copy of you arrives in the past in both scenarios, then you've broken causality, because the thing that causes that event in scenario 1 (you choosing to travel back in time) does not occur in scenario 2, yet the effect still occurs--that means your arrival was uncaused. So, as far as I can tell, those two scenarios either need to have different outcomes (not necessarily the traditional ones, just different from each other) or you've got a paradox.

[Kaelik]

Most time travel stories would interpret scenario A as consistent and concluded, with your past self becoming your future self, but scenario B as requiring the narrative to go back and watch events play out differently, because now your past self will never meet your future self. If you want to take the position that exactly one copy of you arrives in the past in both scenarios, then you've broken causality, because the thing that causes that event in scenario 1 (you choosing to travel back in time) does not occur in scenario 2, yet the effect still occurs--that means your arrival was uncaused. So, as far as I can tell, those two scenarios either need to have different outcomes (not necessarily the traditional ones, just different from each other) or you've got a paradox.

I think you missed the point. What Frank means by all the Orphan in time stuff is precisely that you have uncaused time jumps.

It's actually DragonballZ. Trunks goes back in time to stop Cell/Androids.

He succeeds by warning Goku.

End result, Trunks does not travel back in time, but future trunks is still hanging around, just because he has nowhere to go.

Then I think he dies or something, but whatever, the point is that he literally is an uncaused cause in the new timeline.

[Manxome]

But this system was supposed to prevent ontological paradoxes!

Let me try another example. Tim goes back in time (A) and meets his past self (B). You want to say that if (B) ages, gets a time machine, and goes back in time, he becomes (A), and if he doesn't, then (A) just appears out of nowhere.

Now let's say that (B) goes back in time, but he deliberately does something differently than (A). Say he travels to a different time, or a different place, or he makes sure to take some object or information with him that (A) didn't have.

(B) is now clearly not becoming (A), since (B) is discernibly different from (A). Since (B) does not cause (A), this system presumably wants us to say that (A) still shows up, he's just uncaused. But now (A) and the future (B) both show up in the past, so now we have three Tims running around instead of two, even though none of them has ever performed time travel more than once. Repeat as many times as desired to amass an unstoppable army, research every possible topic in the universe, or just to give your past self arbitrary wealth. You really see no problem with this?

If you want to avoid that, then either (B) can't arrive in the past, or he doesn't meet (A) there. If he doesn't meet (A) there, then he has either prevented (A) from ever time-traveling, or he's in a separate timeline, which Frank claims is not needed. So how does this work?

[Username17]

You sound like you're actually describing something like Self-Regulating Time, except where we (the people listening to the narrative) actually see each of the iterations play out until we reach a self-consistent one, rather than jumping straight to the end state. And since that's only a narrative difference, it's not actually a different mechanic from the perspective of the universe. Though I could also still be misunderstanding your explanation.

Not at all. The idea of this kind of time is that each actor has a distinct and immutable "history" while the actual timeline gets fudged all to hell and gone.

The best example is a river rock. The river rock is shaped by the river as it flows over it. If you physically pick up the rock, and move it upstream so that the course of the river is different, then the river goes somewhere else. With the new course of the river, a rock at that location would never be shaped like that, but this in no way causes the rock you actually moved upstream to cease to exist or alter in shape. Only now the river is time, the course of the river is the historical narrative, and the rock is a person born at some point in the future who is time traveling.

So when you go back to the past, the past becomes the present. Your past is still your past, and you still remember it. It still "causes" everything you do. It just probably doesn't exist any more anywhere in the actual time stream because you are changing the present which means that the future will be different. The river is gone, but the rock remains.

-Username17

[Heath Robinson]

Since it was mentioned in Manxome's post, any good attempt at a time travel RPG will put limits on the Gemini. Be it that the Gemini is dangerous, or noting that the Geminis you pull out of potential futures are unlimited but also probably more likely to try to hit on Helen of Troy than help you in any meaningful way.

In a universe that permits existances that will be uncaused in the current course of history you should be making a test based on your dedication to achieving a task and your ability to persuade people to help you (these people are yourself, but they've had a different history to you and are therefore different people). In the SR4 stat block it'd be Willpower and Charisma, in your stat block it might be different. Apply modifiers based on the physical danger of the task, the risks/benefits to people significant to your character and how fun the task is. Some sort of conversion factor translates this to the number of future selves that turn up to help you.

All the other potential Geminis figured you had enough people (or got so bored of doing the same thing over and over) then pissed off down the big bang burger bar to gamble on your odds of success, should it please them.

[Caedrus]

I have a germ of an idea on time-travel and temporal magic in an RPG, but I think too much sometimes. For awhile there, I've considered the most satisfactory explanations of time-travel to use loops (where time-travel is already within the chain of events). However, I've been thinking and realized there's what's called a Ontological Paradox with that, and now I'm rethinking the whole concept again.

Are there any good RPGs that handle temporal mechanics in a satisfactory manner? Heck, what would satisfy me?

A few options that immediately come to mind:

Chrono Trigger: You can go to preset times, except the exact time you go back to is progressive (so that you don't just undo all the changes you've made when you go back to 10,000 BC again. Or meet yourself coming back. Or whatever.) Your actions change the future, and indeed it looks like you caused the dinosaurs to die out. Might create the paradox you're talking about.

Tales of Phantasia: You can travel around in time and change history, but you cannot travel in time to any point in which you have existed. Ergo, you cannot ever meet yourself. Your actions change the past, and they WEREN'T that way before.

Terminator: Time travel is made by some inhuman force that you don't understand, so the consequences are hazy, and you can't really control exactly where you go and how everything works. However, it's clear that you can change the future by changing the past.

A modern theory based on observations in quantum physics: Taking actions in time travel doesn't actually have any effect at all on YOUR reality, because each new choices creates a parallel dimension. Endless parallel dimensions exist for every choice that was ever made. You can go back in time to figure out what the Romans were like, and hell you can make a whole new dimension where you gave the Romans machine guns, but it won't change your dimension at all and you can just go back to it. This theory avoids paradoxes, so far as I know. You can make a new future, but you can't actually change the past of the dimension you came from, and therefore you cannot affect your own coming into existence.

[virgil]

Going by Frank's vision, there is a sort of metatime, in that time-travellers become 'unstuck' and are largely exempt to changes in the stream.

As for future-Trunks in DBZ, he doesn't get killed. His present is unchangeable, and goes back to a Cell-destroyed world after Cell is defeated. The reason he goes back in time is to train and learn about the androids while they're weak, so he can know how to beat them back in his present (the damage they've done is already done). Basically, going backwards in time creates a timeline branch. He can revisit the same branch so long as he only goes to a future point along that branch (so he can't double up); but his personal past is very real and unchangeable, and returnable.

[RandomCasualty2]

Here's a few more choices:

You-Fix-It Time: Time Travel is a lot like nuclear power. It can be used as a tool or as a weapon of mass destruction. And it can blow up in your face if you aren't really careful. The responsibility of preventing paradoxes are on the time travelers themselves, as there is no internal regulation to time. If a given change screws up time to create a paradox, something really bad happens. Maybe reality implodes or what not, and that's something people try to prevent. Thus most of the work done by Time travellers is to stabilize the past and create plausible timelines by dealing with paradoxes. This is nice for an RPG because it always gives you something interesting to do. It does require some kind of technology or magic that can predict incoming temporal catastrophes and some kind "speed of time" restriction so that there's some time to actually fix a potential catastrophe before it happens.

Rejected Timelines: Time travel doesn't always work. Sometimes it simply fails, and your time machine blows up, or otherwise spectacularly fails. This happens when the projected time change would create a paradox, or other series of events that can't happen. And in such a case, the events don't happen. Since you going back in time would screw shit up, you never make it back in time, because that's the only possible result. Basically for an RPG standpoint, this means that you play out the time travel as normal, but if there's an unresolved paradox, all that occurred during that time jump is simply ignored, and you pretend it never happened, going back to the point where the timejump first occurred and simply saying that it failed. If you wanted to be harsh and unforgiving it may even cause a TPK.

[Manxome]

Not at all. The idea of this kind of time is that each actor has a distinct and immutable "history" while the actual timeline gets fudged all to hell and gone.

The best example is a river rock. The river rock is shaped by the river as it flows over it. If you physically pick up the rock, and move it upstream so that the course of the river is different, then the river goes somewhere else. With the new course of the river, a rock at that location would never be shaped like that, but this in no way causes the rock you actually moved upstream to cease to exist or alter in shape. Only now the river is time, the course of the river is the historical narrative, and the rock is a person born at some point in the future who is time traveling.

That's a pretty analogy, but as far as I can tell all you're doing is sneaking in a concept of metatime (represented in your analogy by: time). The rock that you moved upstream comes from a point that, at the end of your narrative, is not part of the space-time continuum, and therefore does not exist unless you allow that something outside that continuum exists. So you need something outside of normal space-time (like metatime, or alternate timelines) or you have an ontological paradox, just as I've been saying for several posts.

Things also get a lot more complicated if you point out that it doesn't make sense to talk about time shaping something without any time actually passing, so your analogy apparently requires that everything in your stream is always moving downstream at the speed of the water except when "time-travel" occurs. Which makes it really hard to envision one of the rocks altering the course of the stream in the first place.

Not to mention that people don't exist at a point in time, they exist over a continuous stretch of time, from their birth to their death. So if you're viewing time as a spatial dimension, time-travel (as traditionally conceived) isn't relocating an entire person to a different point in the timeline, it's cutting them in twain and moving part of them to a different point. So when you get down to specifics, I don't even know what the different parts of your analogy could validly represent.

So, unless I'm still totally missing some important and fundamental point, your analogy fails. I am unable to convert any interesting scenarios at all between "real" terms and the terms of your analogy, in either direction.

It does require some kind of technology or magic that can predict incoming temporal catastrophes and some kind "speed of time" restriction so that there's some time to actually fix a potential catastrophe before it happens.

Which, incidentally, also requires meta-time. Speed is a way of describing position as a function of time. Describing something's position in time as a function of time is...rather uninteresting, unless "time" refers to different things in each instance.