A question about time travel

[Umbran]

Replying to myself is weird, but this is a bit of an aside.

Well, there's no actual answer to that in physics. So, as a game designer, what do you want to do with it? Maybe it just sucks that you don't know the new timeline - perhaps after repeated trips, you don't know what you should change, becuse your knowledge of history is out of date.

This is a problem that can plague time travel games - if the PCs substantially change history, the GM needs to rewrite the history each time, which is kind of a pain.

Thus, most games are about maintaining the timelines, so if the PCs win, you don't need to rewrite history much.

 

[Jd Smith1]

This sounds like this book I read where white South Africans travel back to American Civil War and give machine guns to the South.

View attachment 127831

This, yes, and Tim Power's Annibus Gates.

 

[Jd Smith1]

Congrats, you've discovered the bugaboo of all 'go back to the past' stories: Paradox. That's why alt history works better, no paradoxes. Unfortunately, I can't think of many ways to make it work that don't involve GM fiat. "That's the way it works, because I said so!" Of course, if you're ok with that, it solves a lot of problems. (Say, the PCs are part of an organization that is HQed in a time bubble that is 'outside the time stream'. That's been used a few times with reasonable effect.)

I was afraid of that. And no, I'm not comfortable with GM fiat.

Well, that's how it goes.

Thanks for the input, guys.

 

[Nytmare]

In a closed loop single timeline, permanently changing the timeline via time travel would involve having to plant seeds for a new impetus for change.

Going back to save the princess would necessitate leaving yourself a note to let you know that you will not only have to go back in time to prevent an accident that didn't happen, but you'll also have to remember to write this same note and leave it for yourself.

Also you wouldn't be able to just reuse the same note because if you did, that note would continue to age and eventually rot away to nothing, causing the princess to go unsaved.

Single timeline time travel stories are boring.

 

[MarkB]

Also you wouldn't be able to just reuse the same note because if you did, that note would continue to age and eventually rot away to nothing, causing the princess to go unsaved.

I remember one story which included exactly that, The Stainless Steel Rat Saves The World. One of the supporting cast is supposed to write a covering note on the package they're going to send back to the protagonist's past self - but they run out of time, so the protagonist just slaps on the same note he took off the package when it arrived in his past. That bit always bothered me, for precisely the reason you stated.

Single timeline time travel stories are boring.

And single timeline time travel games are constraining. They don't work unless the entire group shares a single focused goal and wants to work towards ensuring that predestined outcome.

 

[Umbran]

In a closed loop single timeline, permanently changing the timeline via time travel would involve having to plant seeds for a new impetus for change.

That depends on how the universe deals with the paradox if you don't leave a note.

There is a book, Timemaster, by Robert L. Forward, who is a fairly famous physicist, who covered a version of time travel that seems to be valid under Einstein - basically, you can do what you want, but the result will be self consistent.

The end result is that, from our perspective, the time traveler loses free will, because certain things WILL happen, but from their own perspective, they just keep going forward making their choices, even though we know what they will be. It is an interesting read, but would probably make a pretty lousy game.

 

[Voadam]

Single timeline from Seven Monkeys can work in an RPG.

I ran a Pathfinder Reign of Winter game (the Baba Yaga Adventure Path).

In the Pathfinder world one of the historical facts is that centuries ago Baba Yaga conquers part of the viking lands and installs her daughters as rulers over the now eternal winter witch land enslaving a large number of viking peoples. There is conflict between the witch lands and the remaining viking lands and vikings have a history of conflict with evil witches since then.

In my game the party traveled through a fey portal and I expanded on the module to have it be a journey into the fey First World where reality and time work differently instead of an instantaneous pop to the other side of the portal.

They were going down a path when a gnome runs up from the forest jumps onto the path and asks for protection, a witch is chasing him. The gnome says that if they stay on the path they will be safe and if he is under someone's protection on the path he will remain safe too. The viking paladin in the group immediately agreed. Crashing through the woods comes a young slavic looking woman in a flying giant mortar who wants revenge against the gnome. The party quickly realizes this is young Baba Yaga from the past who they are meeting up with in the Timey-Wimey First World. She asks the party to give up the gnome from the protection of the path so she can have her revenge and offers a reward if they do. The paladin refuses and she glowers and promises revenge against him and his people for generations but he does not leave the path and she takes no immediate action against him.

The paladin realized that her revenge was raising an army to conquer and enslave his people in her timeline. He set up the established historical conquering of his people.

This is the Seven Monkeys theory of time travel, there is one timeline existing start to finish, with some loops where time travel happened, but everything happened and nothing in the existing timeline changes from the time travel.

As a DM I did not need for things to work out this way, I did not plan from the start for this or any PC to be the cause of the history invasion, but I capitalized on how the PC's choices worked in the situation to go with it.

The party was interacting with a small number of variables, not themselves or their ancestors in the past, and they realistically would not kill archmage Baba Yaga as a low level party, so there was some interaction but not a lot of risk of changing anything. If the party had not incurred her wrath the game would have worked out perfectly well, her reason for invading the viking lands would have just remained a mystery.

It gets a lot trickier if the party can go back to themselves or be in other positions to create paradoxes.

 

[MarkB]

Single timeline from Seven Monkeys can work in an RPG.

I ran a Pathfinder Reign of Winter game (the Baba Yaga Adventure Path).

In the Pathfinder world one of the historical facts is that centuries ago Baba Yaga conquers part of the viking lands and installs her daughters as rulers over the now eternal winter witch land enslaving a large number of viking peoples. There is conflict between the witch lands and the remaining viking lands and vikings have a history of conflict with evil witches since then.

In my game the party traveled through a fey portal and I expanded on the module to have it be a journey into the fey First World where reality and time work differently instead of an instantaneous pop to the other side of the portal.

They were going down a path when a gnome runs up from the forest jumps onto the path and asks for protection, a witch is chasing him. The gnome says that if they stay on the path they will be safe and if he is under someone's protection on the path he will remain safe too. The viking paladin in the group immediately agreed. Crashing through the woods comes a young slavic looking woman in a flying giant mortar who wants revenge against the gnome. The party quickly realizes this is young Baba Yaga from the past who they are meeting up with in the Timey-Wimey First World. She asks the party to give up the gnome from the protection of the path so she can have her revenge and offers a reward if they do. The paladin refuses and she glowers and promises revenge against him and his people for generations but he does not leave the path and she takes no immediate action against him.

The paladin realized that her revenge was raising an army to conquer and enslave his people in her timeline. He set up the established historical conquering of his people.

This is the Seven Monkeys theory of time travel, there is one timeline existing start to finish, with some loops where time travel happened, but everything happened and nothing in the existing timeline changes from the time travel.

As a DM I did not need for things to work out this way, I did not plan from the start for this or any PC to be the cause of the history invasion, but I capitalized on how the PC's choices worked in the situation to go with it.

The party was interacting with a small number of variables, not themselves or their ancestors in the past, and they realistically would not kill archmage Baba Yaga as a low level party, so there was some interaction but not a lot of risk of changing anything. If the party had not incurred her wrath the game would have worked out perfectly well, her reason for invading the viking lands would have just remained a mystery.

It gets a lot trickier if the party can go back to themselves or be in other positions to create paradoxes.

Sure, but that only works if the fixed constant in your timeline is invulnerable. If the party has any kind of chance of actually defeating either Baba Yaga or one of her daughters, it doesn't work.

Basically, constraining the party's choices is implicit in the concept.

 

[Voadam]

Sure, but that only works if the fixed constant in your timeline is invulnerable. If the party has any kind of chance of actually defeating either Baba Yaga or one of her daughters, it doesn't work.

Basically, constraining the party's choices is implicit in the concept.

The fixed constants are inherent to the concept of the one timeline.

Also the invulnerability of the situation would only come up if the party chooses to interfere and can actually do so. 18th level young Baba Yaga is not really threatened by 3rd level party in the woods so no real issue. You could have it be 7th level BY who could be threatened though and the party could choose not to mess with her so again no issue. If they do take out 7th level BY who does not have a contingency you have to deal with possible paradox because the one timeline no longer works.

Ways to get around it without paradox would be, its not Baba Yaga they killed, she got raised later from a contingency she had planned, there are many Baba Yagas not just one (or its actually a title in an organization) and they take revenge for the murder of their sister. Very similar considerations to working prophecies into a game, the reverse of going back in time.

The extent of the deus ex machina to preserve the timeline and avoid paradox can be strained narratively so the more the plot gets tangled up with itself the messier it can be. The party interacting with itself is particularly fraught for making this concept of time work in the game.

 

[Shiroiken]

I'm kicked around ideas for future campaigns, which I usually do about the time my current campaign reaches the mid-point.

The point I'm currently considering is this:

Say time travel into the past is possible, with a max 'depth' of two hundred years.

I was considering how, and why, this could be used. If changing the past immediately changes the future/present, then there would be motivation for extremist groups to desire the tech so they could re-order history; for an example, modern-day Nazis sending a team back in time to aid the Third Reich in winning WW2. However, this would also wipe out the persons who undertook this plot, because as history adjusted itself, the scope of changes such an alteration of history would have would mean that the plotters would be facing the possibility of not having been born, or having been born to such radically changed circumstances as to be completely different people.

I know this is rambling and foggy, but I'm going around and around in circles: to change the past would take a motivated and professional (and thus intelligent) team; changing the past would mean the undoing of those same team members.

Am I looking at this wrong?

You've got to decide the "rules" of time travel for your game beforehand. Honestly, if you make the timeline fixed, where the party can't change the outcome, this is going to be both frustrating and disappointing to the players. I prefer the multiple timeline option, where the travelers can change history to create a new timeline at the cost of potentially destroying their own. This allows the players to decide the ramifications, as they can never return home, forced to live within the new timeline (either in the past or the present, depending on how you want the machine to work). I did this with my first campaign as a way to adjust the changes from 1E D&D to 2E, with only the party aware of the changes.

Another interesting option is to use it for failure, as per Groundhog Day and Happy Death Day. If you travel into a timeline where you exist, you inhabit your body of the time. You use the time machine to attempt the change an event, only to fail. You then use the machine to return to the original starting point to attempt it again. The players slowly both gain levels (or whatever character improvement is used) and knowledge they need to succeed. If a character dies, they respawn as their last incarnation (you'll need to keep a copy each time they reset in case). An evil trick is to have another character also going back in time to a similar point that changes other things for their own reasons, keeping things subtly different each time.