Time Travelling

IMO there are only three ways time travel works well:
1. Time Travel is very limited; it can only be done for a brief period of time or can only be done once or twice (eg The Prisoner of Azkaban)
2. It's treated as something that shouldn't be taken too seriously, as its just a vehicle to get its characters into trouble. Oftentimes even the time travelers don't really know how it works (eg most of Doctor Who, Star Trek)

Outside of these two, time travel almost always causes tons of problems and plotholes. There's a reason time travel worked in The Prisoner of Azkaban and not in the Cursed Child. ok there are many reasons the Cursed Child didn't work, but the way they handled time travel was a major one.

>three ways
meant to say two

Nah, it's a rule for how that universe's time travel works. You can't travel to a place and time you've already been to unless special circumstances are involved. Meaning once you've landed in a time you have to solve problems and survive in real time.

I did a time travel campaign once. I only included time travel because it had been a normal campaign up until the last few sessions, and then while theory crafting for how it would end I realized that a series of coincidences across the campaign made a time travel reveal actually reasonable.

I spent a few sessions dropping hints and escalating how weird things were until the big reveal. Was fun, players loved how well it had 'come together' and the table actually cried when one of the characters shot an NPC to create a paradox to cause a better timeline.

>2. It's treated as something that shouldn't be taken too seriously
That's kind of a shame, I'd like to see more things try and treat timetravel very rigorously.
Shit like this seems like it's almost made for science fiction plots:
en.wikipedia.org/wiki/Novikov_self-consistency_principle
iopscience.iop.org/article/10.1088/0264-9381/9/10/014/pdf

>8ball falls a bit off course due to time fuckery in picture
>rolls out window
>window happens to be 10 stories up in the middle of city
>falls and kills scientists who normally ended up curing a horrible disease
>MILLIONS ARE DEAD

>iopscience.iop.org/article/10.1088/0264-9381/9/10/014/pdf
Ah crap, that needs a login. Here:
f.lewd.se/Dmf1XQ_TheJinnofthetimemachine.pdf
Basically, it describes a way that a time machine can "create" items and information out of thin air, provided they later return to the time machine, and calls those objects "Jinnee".

It gets way more bizarre than that.

AAAAAAAH

I didn't word that very well. By "shouldn't be taken too seriously" I meant that the causes and effects of it should be kept as simple as possible and that the author shouldn't spend too much time delving into how it works exactly to avoid writing themselves into a corner or creating unnecessary plotholes.

As for your picture, I'm pretty sure that's how it was handled in Prisoner of Azkaban.

>By "shouldn't be taken too seriously" I meant that the causes and effects of it should be kept as simple as possible and that the author shouldn't spend too much time delving into how it works exactly to avoid writing themselves into a corner or creating unnecessary plotholes.
Fair enough.

>As for your picture, I'm pretty sure that's how it was handled in Prisoner of Azkaban.
Huh, you're right. Interstellar is the probably the example of NCP time travel I'm most familiar with. but I'd not noticed that Harry Potter did it too.

What do you think about "observer effect" approach? You can't change the past, but if you don't know what actually happened, results remain "unset" so you can change details in the past.

As a story element time travels are really only satisfying when they work within closed loops. You travel back in time to change the past but the more you try the more you realize that you travelling back in time to change the past was always part of the event chain that caused the past to get messed up in the first place.

That doesn't work very well for tabletop games however. In that medium your best bet is more likely something akin to Moorcock's multiverse (or the short-lived concept of Hypertime in DC Comics) where you can travel between alternate timelines and worlds and fuck things up without necessarily affecting your original timeline.

Yes.

Sure. Just be sure to establish how it works up front so you don't have to pull some exception out of your ass to move things along or run into some weird loophole in your rules because you didn't think them through.

And maybe make sure you arrange the setting so that all the consequences of whatever time shit you've cooked up actually affect the world. Don't just shove it into a corner and ignore it when it's inconvenient.

Time is an arrow, always moving forward, it can only change it's direction after it's looped around already. time travel is just taking the long way around, but with the universe.

You cannot change the past, but if you wait long enough, the past will be your future again.

OR Travelling forward into the future only.

Forgot pic

In terms of systems, Continuum is the only one I've seen approach this with anything like reasonable success.

Although I've also got a PC whose backstory turned out to be a time travel plot in a game I'm currently in, which was a clever but rather awesome surprise from the GM for me.

Yes, that's why you travel to a day before you landed the first time. That way you cannot meet yourself and universe doesn't try to erase you.

Waitasecond, if you have a machine that does a computation and sends back the result in time, wouldn't you have the result ready even before turning the machine on? I mean, if you can pick arbitrary point in time to send back the message why not the one before you pushed the button to start the calculation?

And if you see the result before starting what does this mean for free will? Can you choose not to start the program in that case, or are you forced by the concrete wall of causality to act?

That also wont work.

Basically, think of it like this: as the time traveller, your own personal timeline has to maintain integrity. You can change thevworld around you, but you can't change YOU.

Its not proximity to yourself that causes the paradox. The paradox is that you dont remember this happening the first time. There are now two versions of you: one where this happened andvone where it didnt, instead of the same person at two different points in time.

By experiencing an event, you have made that event concrete FOR YOU. Go back in time a day earlier, and you cant change anything that would invalidate that event. You might, however, be clever enough to subvert it. You still have to watch your friend die, but maybe you can rig it so what you saw wasnt entirely true.

A funny side effect if this is that each time traveler is essentially luving in their own little universe. The timeline will likely look vastly different to two seperate time travelers.

Well yeah, which is why I don't like how doctor who handles it. It's basically how writers handwave away why the characters cannot use time travel to solve their problems in a show about time travel.

Thats fair. At the same time, its almost impossible to have a plot in a show with easy, consequence free time travel if you can just effortlessly avoid any problem before it actually comes up.

Theres a reason Hiro Nakamura lost his powers every season.

...

Ever see that one movie, Project Almanac? I consider it to be a great example of time fuckery.

>MC and friends dicover time machine
>Use it to do all the fun things they never got to do in High School.
>Timeline changes, they realize this, and become the popular kids.
>MC gets girl
>MC then drops the spaghetti and spergs out
>MC goes back alone to fix his autism
>Keeps fucking up details, then tries ti fix them, making it worse.
>Ends up going batshit insane while drawing massive diagrams of how the splits and choices connect.
>Due to the now massive scale of the choices he made, he is unable to predict the choices necessary to rein the madness in.
>Shit happens
>Eventually realizes his insanity was unavoidable, as he had unknowingly made choices that led to the friend's discovery of the machine in the first place.
>Uses that to travel back and burn the schematics, but leaves his camera behind, with which during the entire movie, had been filming them.
>Timeline ends, he dies.
>He and his friends now have the entire thing documented, but due to the original timeline ending, the schematics still exist.

Essentially Steins;Gate for non weebs.

Time Travel is a trap. Once you ga in the ability to change your past your lufe goes to shit, because you become obsessed with redoing your mistakes over and over until you cant accept the idea of failure anymore. The future will never be good enough. You will always want to change something to make it even better, and its only a matter of time before you start making mistakes you cant fix.

>My name is Barry Allen, and I'm the fastest fuckup alive.

It would be a lot of work for the GM, but if he keeps records of what date and time the players are doing shit, it could be done right.

Every time you go back in time, it creates a completely seperate timeline- from the timeline's perspective, it 'branched' when a bunch of people simply appeared from nowhere. The party's past is still doing whatever they're doing, and events will happen the way they did the first time around, except for what happens if the players fuck something up, such as meeting their previous selves.

It has been

Yeah, CW Barry had to learn this the hard way.

Even had to have Best Flash sit down and give him "the talk"...

"Alright, Barry. Imagine this teacup is the time stream. Now-"

"I put my dick in it."

"Barry, NO."

Step 1: watch Primer.

Step 2: Did you understand all of it? If not, look up some timelines and theories and watch it again. Repeat until you understand it.

Step 3: Be willing to accept that level of fuckery in your game, or just throw the whole thing out and say "it just works"

I love time travel, but would never want people who don't think of it like myself to play in a RPG involving it. Shit would just get too messy too fast. Players killing each other's grandparents would be the least of your issues.

I hated Primer. Not because it's bad at time travel, but because it's a bad movie. Entire scenes skipped over, and only merely 'implied' and all sorts of bullshit like that.

It use to work just fine, but someone went back and change it.

That's your opinion, I can respect that. Personally, I like the leaving of things out so I can feel smart when I figure stuff out, but YMMV.

youtube.com/watch?v=HUMGc8hEkpc

The amount of inoculations you'd need would make planning a trip to the Congo look like a pin prick.

Let alone maintaining a sealed suit so you don't malaria blanket everyone.

Yes.

Just switch of system within the game.

Welcome to philosophy 102

Time travel only makes sense if you aren't actually traveling back in time, but to a different time line/dimension that has no causal link with the one you left.

The purpose of time travel being to marry your father's best friend before she becomes your mother, of course.

There is a way to do it.

You run a game. Have your characters see shit that is hard to understand, like why a bridge that was raised suddenly lowered allowing you and your party to escape. Events like that, running into unexpected allies when you should have been all on your own and about to die. The right Items and gear showing up conveniently. That kind of thing.

Then you travel back.

You've got to set this shit up while going through whatever else you're going through while fucking around in the past and if you fuck up it can have unexpected consequences. Like if you forgot to place a sword in the corner where your past self was just disarmed and pressed against the wall.

You have a temporal save roll or something. If your past self rolls a save he gets out of the event with time being relatively intact. If you fail, your past self could end up losing a limb or straight up die. If that happens you just fade out of existence, leaving your companions one team mate short through the rest of the run.

Honestly it could be done, but you would need to keep notes, very detailed notes. Cause if a PC died, you'd need to adjust future events.

>Time travel only makes sense if you aren't actually traveling back in time, but to a different time line/dimension that has no causal link with the one you left.
I'd say there are three functional models of time travel.

The first is the one you're describing, where each trip into the past actually creates an "alternate history", and so questions about retrocausality or paradoxes are side-stepped. That's probably the simplest model to actually use, but it rules out a number of interesting things.

The second model is the traditional "mutable history" one used in fiction (think Back to the Future), where going back in time will actually change history directly. This generally requires some kind of idea of "meta time" to try and make sense of, and allows for the creation of paradoxes. It looks intuitive, but it almost always ends in a confusing mess.

The third model is "fixed history", where any effects by timetravel had always been a part of history. People can travel back and have an effect on history, but their impact won't be a 'change' because history had always been that way. Paradoxes are clearly impossible. This is probably the least intuitive, but it allows for some really neat shit.

Okay Veeky Forums, theory crafting time;

Can we make anymore functional models of time travel?

>Causality? What's that?
Time travel is possible, paradoxes don't cause you to fuck off, and there's really no way to bring back a future once it's been changed. You could say it's been overwritten, but it's more like it never will exist.

Go ahead and fuck your ancestors, you'll be fine. There's just no way to go back.

>'Bouncy' Time
You can change basically anything you want, but a lot of things have staying power. They'll bounce back. You might accidentally create a world where Rome never fell and blue is a natural hair color, but certain things tend to happen regardless.

Oh, and people remember things. Especially if many rewrites "happen" very "quickly". It's very hard to erase someone from existence. You can change who they are or even what or where, but it's very hard to just drop someone from reality.

>Zipper Time
There are maybe a dozen "Presents" experiencing time. Loose time threads get pulled into a rope on one end, and come out the other only to be pulled apart, only to get pulled back in by the next "Present" in succession.

Threads held by the "Presents" can't be messed with, but feel free to cut and sew and whatever the fuck else to the loose threads. "Once" the change hits a lower "Present" however, it immediately and retroactively takes that change or changes into effect.

There may be some loose threads hanging around, but they don't technically 'exist' unless someone splices them in.

>Polluted Time
Someone in the distant future invented time travel. And then, due to recklessness on their part, everywhen and everyone had access to time travel. Technologies and ideas, even entire regions and peoples got scattered up and down the once pristine timestream. 'Eventually' things calmed down when it was puzzled out how to protect yourself from a shifting timeline, and now years are more like nations all trying to screw each other over to improve their own lives.

Causality's gone, not that anyone really cares anymore.