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SunderedWorldDM
2020-04-23, 08:53 PM
As it says in the title. How have you used time travel in your games? What have you done to make it work really well? I'm running a Doctor Who campaign and another one that I'm considering putting some eon-hopping into, but I'm sure the Playground can enlighten me on ways to do time travel better, or just share some silly stories!

EggKookoo
2020-04-24, 08:41 AM
I don't.

But if I did..!

I'm partial to overlapping timelines. Works like this. You're in 2020. You travel back in time to 2010. This creates a new timeline that moves forward in real time, overwriting the previous timeline. So until you reach 2011 from your frame of reference, the original 2011 timeline is still accessible via time travel. Once your temporal frame of reference reaches it (which takes about a year of your time), that old timeline is overwritten and only the new 2011 remains.

If I, in 2020, travel back to the same exact moment in time in 2010 but I depart after you do ("after" meaning from my frame of reference in 2020), I experience the new 2010 timeline you created, and you exist as a time traveler in that time. In fact, even if I arrive in 2010 after you do, I still experience your timeline as long as the amount of time later I arrive is less than the amount of time in 2020 that I wait before leaving. So if you go back to noon Jan 1st 2010, and I wait five minutes in 2020 then follow you to any time up to five minutes past noon on Jan 1 2010, I will see your new timeline. If I wait five minutes but jump to six minutes past noon, I'll still see the old timeline (your new one will always be one minute behind me, but I can't perceive it).

In this model, the present is created by the past but not dependent on it. It's like footprints on the beach. You walk down the beach, leaving a trail of footprints. The trail is your "past," and where you are at any given moment is your present. The waves come in and erase a section of the trail, but you don't disappear. Once created by the events of the past, the present is self-contained.

If you jump to 2010 and then come back to 2020, the new timeline you created continues to move forward after you leave. It will never catch up to you, though. By the time the new timeline reaches 2020, you'll be in 2030. In fact, coming back to 2020 created a third timeline that began overwriting the previous 2020 timeline...

PopeLinus1
2020-04-24, 10:12 AM
The campaign I'm playing right now isn't about time travel, but my character is a time traveler (they're my avatar, by the way) and my current approach is quite simple: Flavor text.

I was obviously slowing down time when I cast haste on myself, and obviously dimension door was just me personally going back to a time when I was standing there, and did you think I reload my guns? Hells no, I just rewind time for the bullets so they reload themselves.

Democratus
2020-04-24, 10:35 AM
I've used time travel on numerous occasions:


A Dwarf character goes back in time, meets the founder of his clan, and is given his legendary weapon (considered lost in all the ages since the founder disappeared)

A Tavern where every "room" is a portal to an earlier moment in the campaign, allowing characters to try to correct mistakes they may have made (or compound them!)

A campaign where the characters are eventually cast back into the distant past, only to discover that they are the gods who are worshiped in the 'present'

Segev
2020-04-24, 11:07 AM
My players may hate me for it, but the Exalted campaign I'm running features time shenanigans.

One of the iron-clad rules in Exalted is that there's no backwards time travel. This is, metagame-wise, meant to enforce the notion of consequences being absolute. Right up there with "no resurrections."

In my game, this is enforced by the Games of Divinity, whose primary purpose is to be something that can't be casually undone. Making a move in the Games is permanent. No take-backs, no Chaos Lords deciding to change the rules...the Games enforce their rules on anybody who is even aware of their existence.

And, since one of those rules is "no take-backs," once something has happened, it's happened, and you can't go back in time to change that.

However, the way it works is also that time moves foward only as the Games are played. Not that there's a rigid one-turn-to-one-unit-of-time progression, but there is a definite PRESENT. And there is only one past leading to that present.

But there are myriad possible futures, because the present hasn't solidified them yet by advancing through and selecting only one.

During the Primordial War, one Twilight-Caste Solar known as the Crowned Hawk's Wing created an "NP-Hard Completer," a terrifying temporal weapon that spins out billions of possible futures in an attempt to find one where a desired outcome has occurred, and then bring elements from that future back to the present to determine how it as done and bring that outcome about.

The PCs exist in one of those possible futures. And in order to make sure theirs is the one that happens, they need to find out how the thing that was desired was done. They need to rediscover the secret to killing Titans. Because while they live in a future with the Neverborn's existence proving Titans can be killed, and where the Primordial War was won, nobody in their time knows how it was done. When they find it, they need to take that secret back in time to the present, during the Primordial War, and use it to ensure their future is the one that comes to be.

SunderedWorldDM
2020-04-24, 11:12 AM
I don't.

But if I did..!

I'm partial to overlapping timelines. Works like this. You're in 2020. You travel back in time to 2010. This creates a new timeline that moves forward in real time, overwriting the previous timeline. So until you reach 2011 from your frame of reference, the original 2011 timeline is still accessible via time travel. Once your temporal frame of reference reaches it (which takes about a year of your time), that old timeline is overwritten and only the new 2011 remains.

If I, in 2020, travel back to the same exact moment in time in 2010 but I depart after you do ("after" meaning from my frame of reference in 2020), I experience the new 2010 timeline you created, and you exist as a time traveler in that time. In fact, even if I arrive in 2010 after you do, I still experience your timeline as long as the amount of time later I arrive is less than the amount of time in 2020 that I wait before leaving. So if you go back to noon Jan 1st 2010, and I wait five minutes in 2020 then follow you to any time up to five minutes past noon on Jan 1 2010, I will see your new timeline. If I wait five minutes but jump to six minutes past noon, I'll still see the old timeline (your new one will always be one minute behind me, but I can't perceive it).

In this model, the present is created by the past but not dependent on it. It's like footprints on the beach. You walk down the beach, leaving a trail of footprints. The trail is your "past," and where you are at any given moment is your present. The waves come in and erase a section of the trail, but you don't disappear. Once created by the events of the past, the present is self-contained.

If you jump to 2010 and then come back to 2020, the new timeline you created continues to move forward after you leave. It will never catch up to you, though. By the time the new timeline reaches 2020, you'll be in 2030. In fact, coming back to 2020 created a third timeline that began overwriting the previous 2020 timeline...

Wow, my brain bent while reading that! That's a cool take on timelines. I myself don't like to much around with parallel universes and timelines causing drastic changes, but I think this way of thinking may be cool enough to consider it...


The campaign I'm playing right now isn't about time travel, but my character is a time traveler (they're my avatar, by the way) and my current approach is quite simple: Flavor text.

I was obviously slowing down time when I cast haste on myself, and obviously dimension door was just me personally going back to a time when I was standing there, and did you think I reload my guns? Hells no, I just rewind time for the bullets so they reload themselves.
Ah yes, the oldie but goodie fluff! I once remember I had a gnome wizard who cast all of their spells out of a ghostbusters-style proton pack. They loved using Witch Bolt... That sounds like a really cool character! How did they get to time travelling?


I've used time travel on numerous occasions:


A Dwarf character goes back in time, meets the founder of his clan, and is given his legendary weapon (considered lost in all the ages since the founder disappeared)

A Tavern where every "room" is a portal to an earlier moment in the campaign, allowing characters to try to correct mistakes they may have made (or compound them!)

A campaign where the characters are eventually cast back into the distant past, only to discover that they are the gods who are worshiped in the 'present'

Ooh, those are cool, might steal some of those! How did you set those up and get them to work?

EggKookoo
2020-04-24, 11:26 AM
Wow, my brain bent while reading that! That's a cool take on timelines. I myself don't like to much around with parallel universes and timelines causing drastic changes, but I think this way of thinking may be cool enough to consider it...

It's like the universe can support only one timeline, coupled with the idea that matter and energy have a kind of "temporal momentum" that keeps them moving forward. If you fire a gun, and while the bullet is in mid-air somehow vaporize the gun, it's not like the bullet is affected. Once something is put into temporal motion, it stays in motion regardless of what happens to its past.

It causes some weirdness, like you can remember the events of a past that no longer exists. If you go back and overwrite 2011, I (still here in 2020) remember the previous version of 2011. But that's fine -- I don't remember 2011 because I have some real-time connection to it. It's just how my neurons were organized from when they were in 2011. That neural configuration remains in the present. Honestly it's no different from how things work in the real world (assuming time travel isn't a possibility). My memories of the past don't exist in the past.

Segev
2020-04-24, 12:17 PM
It's like the universe can support only one timeline, coupled with the idea that matter and energy have a kind of "temporal momentum" that keeps them moving forward. If you fire a gun, and while the bullet is in mid-air somehow vaporize the gun, it's not like the bullet is affected. Once something is put into temporal motion, it stays in motion regardless of what happens to its past.

It causes some weirdness, like you can remember the events of a past that no longer exists. If you go back and overwrite 2011, I (still here in 2020) remember the previous version of 2011. But that's fine -- I don't remember 2011 because I have some real-time connection to it. It's just how my neurons were organized from when they were in 2011. That neural configuration remains in the present. Honestly it's no different from how things work in the real world (assuming time travel isn't a possibility). My memories of the past don't exist in the past.

That's one way to look at it. Another is that your neurons wouldn't be shaped as they are from the "old" 2011 memories because you now never experienced that particular 2011.

But that is a different model than the one on which you're running.

EggKookoo
2020-04-24, 12:28 PM
That's one way to look at it. Another is that your neurons wouldn't be shaped as they are from the "old" 2011 memories because you now never experienced that particular 2011.

But I did experience that particular 2011. It's just no longer accessible via time travel. But look, the real 2011 is no longer accessible or even arguably in existence at all whatsoever. So why don't my memories of it disappear?

Segev
2020-04-24, 01:02 PM
But I did experience that particular 2011. It's just no longer accessible via time travel. But look, the real 2011 is no longer accessible or even arguably in existence at all whatsoever. So why don't my memories of it disappear?

Like I said, it depends on your model. I was pointing out an alternative model's way for it to work. Your model says that you're a product without a cause, but that you are what you are. And that's fine.

Of course, the Mandella Effect tells us that people can remember histories that are entirely fictitious, too. Depending on how strongly you believe in the Mandella Effect, that is. (Is it the "Berenstein Bears" or the "Berenstain Bears?")

EggKookoo
2020-04-24, 01:20 PM
Like I said, it depends on your model. I was pointing out an alternative model's way for it to work. Your model says that you're a product without a cause, but that you are what you are. And that's fine.

Well, sort of. I guess my model says that the present is configured by the past, but once the present state is set, it no longer needs the past to maintain its configuration (or to become the "past" for the next instant in time). So maybe dominoes are good metaphor. Imagine a strange Rube Goldberg 100-domino setup. The dominoes are tightly packed, so that the moment you tip the first one, it begins pushing the second one, which pushes the third one, and so on. So pushing that first domino instantly tips over all 100 of them. But it's also configured so that domino #100 is thrown through the air and (with astounding precision) displaces domino #1. The "domino timeline" has been altered such that #100 is now in the place of #1. Is it reasonable to say domino #100 is now the one that started the process from its own perspective?

I mean we have to assume the dominoes have some equivalent of memory and can know the sequence that led to them being knocked over.


Of course, the Mandella Effect tells us that people can remember histories that are entirely fictitious, too. Depending on how strongly you believe in the Mandella Effect, that is. (Is it the "Berenstein Bears" or the "Berenstain Bears?")

Or is it the Mandela (https://en.wikipedia.org/wiki/False_memory#Commonly_held_false_memories) Effect? :smallwink:

Segev
2020-04-24, 01:55 PM
Well, sort of. I guess my model says that the present is configured by the past, but once the present state is set, it no longer needs the past to maintain its configuration (or to become the "past" for the next instant in time). So maybe dominoes are good metaphor. Imagine a strange Rube Goldberg 100-domino setup. The dominoes are tightly packed, so that the moment you tip the first one, it begins pushing the second one, which pushes the third one, and so on. So pushing that first domino instantly tips over all 100 of them. But it's also configured so that domino #100 is thrown through the air and (with astounding precision) displaces domino #1. The "domino timeline" has been altered such that #100 is now in the place of #1. Is it reasonable to say domino #100 is now the one that started the process from its own perspective?

I mean we have to assume the dominoes have some equivalent of memory and can know the sequence that led to them being knocked over.Part of the issue with a lot of these sorts of models is that they envision a "meta-time."

"After a certain amount of time passes, the old 2011 stops being accessible. But before the change was made, you formed your memories, so you retain them after the change."

It works in a narrative as long as you accept the notion that there's a real timeline of events in which all these other timelines are embedded, and that EggKookoo going back to 2000 and making changes happens AFTER the 2000 where EggKookoo didn't show up, and AFTER the 2019 where EggKookoo builds the time machine to go back in 2020 to 2000. So there's a 2011 that happens before EggKookoo builds a time machine, and a 2011 that happens after EggKookoo goes back in time to 2000.

This works, again, as long as you can use just that one timeline to keep it all lined up, and EggKookoo is the only time traveler whose hypertimeline has to be kept straight.

It starts getting very convoluted if your hypertimeline starts to be messed with. What if Segev only builds a time machine in 2022 because he learned that the 2020 that would have happened had EggKookoo not gone back in time to change the past would have been way better, and he goes back to 1995 to set things up so that by the time EggKookoo arrives in 2000, things are set up so that he's thwarted and never makes the changes? Did Segev go back to a 1995 that is the same as the 1995 that was prior to the 2000 EggKookoo went back to AND the 2000 EggKookoo never went back to? In our hypertimeline as we've been watching it, EggKookoo was the "first" time traveller, but how do we know that it wasn't actually Red Fel engaging in some nefarious plan of his own that touched neither of them directly? Did either of their time travels interfere with REd Fel's? Cause Red Fel's? be caused by Red Fel's?

And it gets worse if you eliminate the concept of the hypertimeline.



Or is it the Mandela (https://en.wikipedia.org/wiki/False_memory#Commonly_held_false_memories) Effect? :smallwink:*cue Twilight Zone theme*

Necroticplague
2020-04-24, 02:17 PM
Continuum is an RPG all about time travel you might be able to take some notes from. Of particular note is the idea that the universe itself reacts to sapient will and intentions, so some of the headache of time-dealing can be pasted over because they don't really effect you until you're aware they should.

There's also the idea of Frag, which is a handy way of dealing with paradoxes by not making it completely on/off in terms of existence, among other things. Something can have a few problems with its timeline and still be reasonably fine. The idea is the The Universe Is (predestination is strictly true, and the universe will eventually reach a steady state where all paradoxes are solved and all time travel has occured and been accounted for. Its just assumed you aren't playing in that moment of Yet) also allows for an offload of some of the probllems by allowing you to push off the explanation of it into an irrelevant "eh, it'll work out eventually somehow". Sure, it's a paradox for now, but that's only because it hasn't been fixed Yet.

Also, introduces some useful terminology for time travelers, like how to talk about your personal past and future seperate from the world's. Things you've done (personal past) are in your Age, things you're going to do (personal future) are in your Yet. normal past and future refer to the universe's

Segev
2020-04-24, 02:33 PM
Also, introduces some useful terminology for time travelers, like how to talk about your personal past and future seperate from the world's. Things you've done (personal past) are Down of you, things you're going to do (personal future) are in your Yet. normal past and future refer to the universe's

Quibble: I thought your personal history was your Age, not "Down."

False God
2020-04-24, 03:07 PM
Not the normal time travel of going backwards, but we instead went forwards. We knew we were going on an epic adventure (we were all like, level 20-something) that would take us a long way from home so.

To ensure the safety of where we were leaving the party druid developed (with DM permission) a variant of Awaken Plant specifically to create a treant who could create more treants like himself if needed. Unfortunately after giving the now sentient plant the general insutrctions of "protect this place" the tree apparently *coughconnected to the internetcough* saw the horrors non-plant creatures had done to plants, and went about creating treants and having them create treants and the whole thing went south very quickly as incredibly religious (seeing the creating character as a god of nature) and incredibly aggressive trees proceeded to murder or enslave all non-plant life on the large island/small continent where we had made our home base.

Fast forward 750 years later when we returned, the trees had just recently landed forces on the mainland and were preparing for full-blown world conquest.

Yeah....

Unfortunately the campaign didn't continue after that, but our DM did inform us they succeeded.

EggKookoo
2020-04-24, 03:12 PM
Part of the issue with a lot of these sorts of models is that they envision a "meta-time."

Possibly. When I first started playing with this mentally, I assumed a meta-time. I was also trying to work out a time travel mechanism that avoided paradoxes. Alternate timelines works well for that. Marty goes back and prevents his parents from meeting. He wouldn't fade away, he just created a branch where he was never born. Doc Brown even spells this out in the second BttF movie, but I guess he wasn't paying attention during the first. :smallwink:

Anyway, alternate timelines is fine but it also feels kind of weak from a narrative or storytelling perspective. If you "change the past" but really just make a new universe, you're less time-traveling and more universe-hopping. Which is fun in its own right but not quite the same thing. I wanted to work out a way to make altering the past more of a consequence, but avoid the paradox issues that a single-timeline model would cause.

So I thought of time as a form of momentum, rather than a bound-up causal chain. Just like you can be thrown through space, and will continue to move through space with no added energy so long as nothing stops or slows you, perhaps we're all thrown through time. Some initial event set us in motion and we're basically coasting.

I admit this is not my original idea. Years ago a friend recommended I read To Say Nothing of the Dog (https://en.wikipedia.org/wiki/To_Say_Nothing_of_the_Dog), which posits a similar idea. We're not tightly bound to our place in time. Rather we're all being carried along by the same current, and conservation of energy tends to keep us clustered. That's why time passes more or less the same for me and you.

But that got me thinking about how fast that current travels. And around the same time (late 90s) there was a lot of discussion about whether or not gravity travels instantly or is limited to the speed of light (we now know it's limited). Conventional time travel stories suggested changes in time happened instantly. Go back to the age of the dinosaurs, divert the asteroid, and instantly all future history changes. It turned out this was actually the source of the paradox, since changing the past instantly could make it so there's no "room" for you to go back and make the change in the first place. But what if the change in time had a speed limit?

Again, not my original idea. In fact, the first Back to the Future implies this with the gradual fading of Marty's history (as absurd as the fading photo or hand is, it served as Hollywood shorthanding). The 80s miniseries (based on the 70s short story) Millennium also had something similar -- when big changes in the timeline happened, they rippled forward in perceptible ways.

But that got me thinking. Why is the speed of time still so fast? Why wouldn't the speed of time be the same speed that you and I are moving? I mean, why would there be two speeds? So that got me thinking, what would happen if there was a single timeline, but changes in the timeline propagated forward at the speed of time. And us experiencing the present? We're subject to the same temporal physics, so we're all moving at that same speed.

Whew. That's a lot of wind...


It starts getting very convoluted if your hypertimeline starts to be messed with. What if Segev only builds a time machine in 2022 because he learned that the 2020 that would have happened had EggKookoo not gone back in time to change the past would have been way better, and he goes back to 1995 to set things up so that by the time EggKookoo arrives in 2000, things are set up so that he's thwarted and never makes the changes? Did Segev go back to a 1995 that is the same as the 1995 that was prior to the 2000 EggKookoo went back to AND the 2000 EggKookoo never went back to? In our hypertimeline as we've been watching it, EggKookoo was the "first" time traveller, but how do we know that it wasn't actually Red Fel engaging in some nefarious plan of his own that touched neither of them directly? Did either of their time travels interfere with REd Fel's? Cause Red Fel's? be caused by Red Fel's?

It might mean that time itself is just the product of some far-distant future entity mucking around with temporal physics. Of course it wasn't the far future for them. It only became so when they started mucking around.

But we could map this out. We'll need to label the timeline rewrites. I'll use colors.


It's 2020. The timeline is blue, and always has been. I go back to 2010 to make some kind of change to the timeline.
In 2010, my changes alter the timeline to red. Time prior to this is blue. The red starts moving forward at the speed of time.
In 2022, using some kind of meta-time sense, you see this growing line of red, spanning 2010 to 2012. It's two years because you're seeing it two years after the point at which I left.
You travel back to 1995. You make your changes to the timeline. Time at 1995 becomes yellow and starts moving forward. There are 15 years between the leading edge of yellow and the beginning of the red.
When the yellow time hits the red in 2010, it begins overwriting my changes. Meanwhile, assuming I haven't time traveled again, I'm in 2027 (15 years ahead of 1995, plus the two years you waited before time traveling).
When my red timeline reaches 2020, it overwrites the time there. This wipes out my time travel attempt, but since we're all just moving forward based on momentum, it has no effect on me. In fact, I remember a different 2020 than I'm not seeing, but I'm not confused by that as I'm a time traveler.
Your yellow time will eventually overwrite my 2020 but I won't care. I'm living in the world that I made with my time travels. Also assuming you don't time travel again, you'll have experienced 35 years (1995 to 2020) in the world that you made.
In 2040 (doesn't matter the color), Red Fel travels back to 1994 because they want history to be a certain way. Time from 1994 changes to purple. This purple time will consume the beginning of your yellow time in one year, but by the time this happens I'll be in my own 2040 and you'll be in your own 2023 (if I did that math right).


So if I have a swath of red time that you want to get rid of, your choice is to time travel to just before I arrived, thereby consuming it all but never fully eliminating it since you can't close the gap, or to time travel to just before the end of my red time so you overwrite it almost as it's being created, with the acceptance that there will be an initial stretch you can't consume. Although, I suppose there's nothing preventing you from doing both...

I could imagine a kind of time war, where competing forces go back further and further to alter time to their liking. Part of which would be trying to prevent the development of time travel in the new timeline, which may have varying degrees of success. And then complacency would tempt them to sit tight in their new timeline (or risk inadvertently re-introducing time travel). But the longer they do that, the greater the risk it'll develop anyway, and then the whole thing starts over. You could even have sanctuaries, like hidden years that creep forward where things are very different from the timelines before and after. They would do what they can to disguise themselves to avoid detection from the big guns.

Hm... I feel a homebrew coming on...

Segev
2020-04-24, 03:39 PM
And that makes for fun storytelling, but gets into issues if you try to play with it too closely.

For example, if I'm in red-2012, having just been hanging around 2010 when you showed up in my backyard and went off to do your thing to change the timeline, and I get ahold of a time machine and go forward to 2029, am I in red-2029 or blue-2029? From my personal perspective, it's been 2 years since you instituted the red change.

Let's make this more confusing.

So, starting in 2020, all timelines are blue.
You go back to 2010, institute the Red Change.
Psyren (to pick a random forumdweller without his knowledge or consent) from 2008 has a time machine that he just (in 2008) finished, and goes forward to 2011. Is he in blue-2011 or red-2011?
Me, in 2022, "sees" your red change propagating up the timeline, with 2012 being the furthest extent of it (since I'm 2 years after you left in 2020 to make the change in 2010). I go back to 2007 and let Psyren know that you're going to make a change in 2010. Does this change whether Psyren shows up in blue-2011 or red-2011?

In 2022, I go back to 2009, and just hang around, making no changes. Do you show up in 2010 and make the red change, or do you not? Which timeline am I in?

If I go back to 2009 and make a Yellow Change, does the Yellow Change erase you having gone back to 2010? Or do you show up in 2010 in the blue AND yellow timelines, and make the Red Change in both? Or maybe teh REd Change in one and the Orange Change in the other? Are they in parallel, or is one overwriting the other?

You, having gone back to 2020 after making your change, just hang out for a few years, until in 2023, you notice my having gone back to 2009 by the Yellow Change I've caused that's encroaching on 2010. If you go back in time to 2010 again, will you be entering the Yellow, Blue, or Red timeline?

In 2030, I get sick of all of this, and, being an evil necromancer, go back to 2020 just moments before you make your jump to 2010, and kill you. The you of 2030 has moments from when I jump back to realize something is wrong before my "black timeline" overwrites the whatever-color-it-is-by-now timeline of 2020 (your red timeline should just be catching up, in fact). Is the you of 2030 dead, despite remembering having lived through that moment, since he has no memory of it? I'm guessing "no," since it will take 10 years for the black timeline to catch up to 2030.

But in that case, should 2030 you even care enough to go back and stop me from murdering his past self, since the black timeline will never catch up to him, as he's always 10 years ahead of it even if he never time travels again?

Necroticplague
2020-04-24, 04:27 PM
Quibble: I thought your personal history was your Age, not "Down."

Ah, yep, you're right.

Looks like I got Age/Yet confused with Down/Up. That's what I get for not having the frankly vocab-heavy book open while trying to spew from it.

Anyway, just to contribute some additional speculative media as potential references:

Achronal is an RTS that handles something others mentioned here rather interestingly. Basically, the meta-time concept I see discussed does exist in a very tangible way in the form of entities called 'time waves' that propogate time forward from where they catch up with time. So paradoxes actually have simple solutions: they'll alternate which state is true each time a time wave moves past them. As a result, any period within two waves is internally consistent, if you're willing to accept that things can pop up out of nowhere as not breaking consistency (as that's what appears to happen when things move from one set of waves to another). And you can (and, if you want to win, should) either avoid or trigger results of time catching up to a unit by time-travelling past or into a time wave. The game's almost a decade old now, but one should still be able to dredge up old footage or guides of it if they want to see some applied time shenanigans.

EggKookoo
2020-04-24, 05:08 PM
And that makes for fun storytelling, but gets into issues if you try to play with it too closely.

So do paradoxes. I mean time travel in general often falls apart under any kind of scrutiny. The safest is pure alternate-timelines but eventually the writer will mess that up too.


For example, if I'm in red-2012, having just been hanging around 2010 when you showed up in my backyard and went off to do your thing to change the timeline, and I get ahold of a time machine and go forward to 2029, am I in red-2029 or blue-2029? From my personal perspective, it's been 2 years since you instituted the red change.

So to be clear, you're kind of in red 2012, but really you're turning it into yellow-2012. Strictly speaking, red-2012 is the version that you're not there.

But I had you jump to 1995, so by the time you do your next time jump, I've had 19 years to paint time red. Seventeen between your arrival in 1995 to 2012 (painting it yellow the whole time, go you!), plus the two years before you left 2022 after I left in 2020. So my red timeline spans 2010 to 2039, and you land in red-2029.


Let's make this more confusing.

So, starting in 2020, all timelines are blue.
You go back to 2010, institute the Red Change.
Psyren (to pick a random forumdweller without his knowledge or consent) from 2008 has a time machine that he just (in 2008) finished, and goes forward to 2011. Is he in blue-2011 or red-2011?
Me, in 2022, "sees" your red change propagating up the timeline, with 2012 being the furthest extent of it (since I'm 2 years after you left in 2020 to make the change in 2010). I go back to 2007 and let Psyren know that you're going to make a change in 2010. Does this change whether Psyren shows up in blue-2011 or red-2011?

Ok, it has to go in order. Psyren has to go first.

Psyren in 2008 jumps forward to 2011. The timeline goes, say, purple at that location.
In 2020, I live in purple time. Pyren arrived 9 years ago from my perspective, and since 9 is less than the amount of time since he jumped (which was 12 years ago), I'm in his rewritten timeline. Unless I was aware of his time traveling, I'm probably oblivious to these changes and it's just normality for me.
I jump back to 2010, which is still blue time. I start changing time to red. When 2011 arrives, my new red time overwrites Psyren's purple time. I basically erase the effects of his arrival (along with the original blue timeline) with my new one.
You, in purple 2022, go back to 2007. 2007 is blue time, which you now start changing to yellow. You bump into Psyren in 2008, but at this point you're repainting time yellow, so everything that happens as a result of this meeting is still yellow time.
Assuming Psyren still jumps to 2011 based on your question, he would end up in red time. The reason is I initiated red time at 2010. Two years pass before you jump back to 2008, so when you do that red time has reached 2012. Then you wait another year before you find Psyren and he jumps to 2011. At that point red time has reached 2013.


In 2022, I go back to 2009, and just hang around, making no changes. Do you show up in 2010 and make the red change, or do you not? Which timeline am I in?

I kind of assume there's no such thing as "making no changes." Your mere insertion into a timeline is enough to change its color.

So changing the scenario a bit? If you went to 2009 from 2022 you'd end up in blue time, since I don't convert time to red until 2010, and Psyren doesn't change it to purple until 2011. So 2009 hasn't had anything happen to change its color.


If I go back to 2009 and make a Yellow Change, does the Yellow Change erase you having gone back to 2010? Or do you show up in 2010 in the blue AND yellow timelines, and make the Red Change in both? Or maybe teh REd Change in one and the Orange Change in the other? Are they in parallel, or is one overwriting the other?

Assuming the other conditions haven't changed (I leave from 2020 and you leave from 2022), yes, your 2009 trip will start changing time to yellow and override my red time. It functionally erases my changes three years after I make them. This means there's a 3-year red patch moving forward, followed by yellow time.


You, having gone back to 2020 after making your change, just hang out for a few years, until in 2023, you notice my having gone back to 2009 by the Yellow Change I've caused that's encroaching on 2010. If you go back in time to 2010 again, will you be entering the Yellow, Blue, or Red timeline?

Yellow. It kind of depends on how long I stay in the past before returning to 2020, but there's almost no least amount of time that would let me get back to my red 2010. Just the three years I wait until 2023 would insure that.


In 2030, I get sick of all of this, and, being an evil necromancer, go back to 2020 just moments before you make your jump to 2010, and kill you.

Ouch!

Ok, before we proceed, understand that killing me doesn't prevent me from going back to 2010, since I did that 10 years ago from your perspective. All it does is create a new black timeline in which I didn't go back, which moves forward from 2020. But I already had gone back to 2010. In fact, if you wait until 2030, it's possible my new red time has already reached 2020 and you might not even see me go back, since it's a different timeline there.


The you of 2030 has moments from when I jump back to realize something is wrong before my "black timeline" overwrites the whatever-color-it-is-by-now timeline of 2020 (your red timeline should just be catching up, in fact).

Yes! You see it!


Is the you of 2030 dead, despite remembering having lived through that moment, since he has no memory of it? I'm guessing "no," since it will take 10 years for the black timeline to catch up to 2030.

There is no me of 2030. That would have been the me of blue time, but he left in 2020. Oh, well, I guess I did come back and then jumped back again in 2023. Either way, though, I'm not there.


But in that case, should 2030 you even care enough to go back and stop me from murdering his past self, since the black timeline will never catch up to him, as he's always 10 years ahead of it even if he never time travels again?

Ok, for sake of argument, lets say I came back to 2020 after turning time red in the past. Not sure why I would do that since my whole plan was to alter blue time, which for whatever reason I didn't like. So it makes sense I would live out my life in red time. But let's say I do come back and stay put. No more time traveling. I would have no memory of your attempt on my life in 2020, since that didn't happen in my current timeline. All you doing is changing time from 2020 forward from blue to black (which involves removing me), but like you say I'm always 10 years ahead of it. All that happens is if Psyren decides to travel to black time to speak to me, I won't be there.

Man, this stuff is fun.

Xuc Xac
2020-04-24, 05:53 PM
You can't go back in time and change history because it already happened.

If you are in 2020 and you travel back to 2010 to change something, it doesn't work. You can try, but you'll find out that it's already been done. From the point of view of 2020, you've already traveled back to 2010 and tried to change things: the events of 2010-2020 are the result of whatever you did in 2010 (both the 2010 you and the 2020 time-traveling you).

"I want to travel back to the 1930s and kill Hitler!"
"Well, you can try, but the 1930s already happened. You can go there now, but from the point of view of the present you've already been there and you obviously didn't get him. If you did kill Hitler in the 1930s, you wouldn't be here now talking about going back to kill him."

The fun part in a game is letting them try to change the past and then coming up with reasons that things turned out the way they did anyway in spite of (or because of) their past intervention.

Necroticplague
2020-04-24, 06:30 PM
You can't go back in time and change history because it already happened.

If you are in 2020 and you travel back to 2010 to change something, it doesn't work. You can try, but you'll find out that it's already been done. From the point of view of 2020, you've already traveled back to 2010 and tried to change things: the events of 2010-2020 are the result of whatever you did in 2010 (both the 2010 you and the 2020 time-traveling you).

"I want to travel back to the 1930s and kill Hitler!"
"Well, you can try, but the 1930s already happened. You can go there now, but from the point of view of the present you've already been there and you obviously didn't get him. If you did kill Hitler in the 1930s, you wouldn't be here now talking about going back to kill him."

The fun part in a game is letting them try to change the past and then coming up with reasons that things turned out the way they did anyway in spite of (or because of) their past intervention.

This only really works if you basically assume a strictly deterministic universe, though. Like one that even our universe appears to fail to adhere to. In which case, the point of time travel as a plot device seems rather pointless, as it isn't any more distinct than, say, just moving to a sufficiently different location.

Reathin
2020-04-24, 08:35 PM
Silly stories, you say? Well, okay then!

A while back, my RP group did a game based on Warehouse 13 (a neat series where historical/mythological artifacts sometimes obtain genuine supernatural powers). We were Warehouse 12, set as a prequel in the late 1800s, using the Fate system for game mechanics. The game included two character with an atypical relationship to time. One was a time traveler from the 22nd century's Warehouse 14 (the Warehouse has several time-travel related artifacts, some of which can change the future and some cannot, apparently, which is a fun idea) who destroyed her time machine accidentally when arriving in the past (our present), while my own character possessed Aladdin's Ring, which he used to wish for ageless immortality.

Part of the fun was our characters different approach to their time-traveling situations. The convention backwards time traveler was a woman, so she had to navigate 1800's London's attitudes and lack of 22nd century tech that she was so good with, while my own was centuries old taking the "long way" through time, which did a number on his empathy (case in point, when we were exposed to Doctor Henry Jekyll's Hyde potion, it unleashed a NICER personality). Eventually, when our main plotline was done (defeating the nefarious plans of Jules Verne), the conventional time traveler was able to go home, because in the future, they had records of her involvement in the final battle and so knew when and here to target pulling her back.

And my character, who was still ageless, was there to meet her with a snarky "what took you so long". Loved that game.

Tvtyrant
2020-04-24, 08:49 PM
I did a groundhogs campaign in a city where an Elder Evil got free. The party had to relive the last day of existence over and over again to get clues on how to stop it from punching through, with all sorts of weird anomalies and monsters all over the city.

aglondier
2020-04-25, 01:24 AM
I was part of a very long running Forgotten Realms campaign. Most of the party were wizards of some description, and mine was also a Chronomancer. Shenanigans with Time started small, but escalated...

After letting me have the power of Chronomancy, our GM kinda just ran with all later time stunts, just making sure I remembered to deal with the other end of things...it became a bit of a running gag later with the number of times we would have to bail out our younger selves...

The first real stunt was when I was dropped out of the sky. While falling to my death, a me from the future appeared beside me, taunted me, and handed me a ring of featherfall that belonged to another party member, saying to make sure to return it next Tuesday. Which I did. Later, I arranged to borrow the ring and delivered it to my falling self. And yes, I made damn sure to taunt my idiot earlier self...

At one point we needed a very specific weapon to defeat a foe, so I reached into the Timestream and pulled it out from when/wherever it had been. Later we had to got back and participate in the forging of the weapon...something we did a number of times, but what mastersmith would refuse the willing and freely given aid of a band of mysterious archmages?

Later, during our early epic adventures, I travelled back to before the fall of Netheril and studied epic spellcasting there. Later still, I went further back and set things up so I could take those studies.

At the end of the campaign, I travelled back to the very moment Io created the realms, and participated, taking the name and role of Amauntor by being there first and naming everything as it was created.

Despite the temptation, no, we didn't train every archmage worthy of that name in the realms...only about half of them...we knew their names, and had access to epic divinations, so...

NichG
2020-04-25, 06:48 AM
I think the propagating color-line model works better if rather than assuming some kind of universally shared meta-time, you think of the timeline as a stream of particles being emitted from the past to the future - so rather than a given event in time happening 'once', it's constantly re-happening with or without the intervention of time-travellers - it just happens that unless there's an intervention, (in a deterministic universe) it re-happens the same way every time so it appears to not be changing. Note, if we go to a probabilistic universe, this is going to have interesting consequences for what time travel would be like, which is what I eventually want to get to with this idea.

So anyhow, you've got a stream of particles emitted from the past, flowing towards the present. You don't need a global meta-time, but each particle has its own meta-time in the sense that there's a unique ordering to it's transformations from an internal perspective. The main thing we gain from this is, like in relativity, we don't need to worry about simultaneity anymore - unless two particles happen to be co-located in time and space, we're going to make no claims about their relative meta-time coordinates, nor will we need to.

So in this system, time travel is implemented by taking some of the particles as they enter a certain space-time region, and moving them along a curve which re-enters the main stream of events before it left (but, particles traveling along that tube still advance their own meta-time coordinate - e.g. no clocks going backwards, de-aging, etc - they're still traveling forwards in time, but doing so is just landing them in the past).

There's nothing particularly paradoxical, or even un-computable about this kind of setup. You could literally build this with pipes and water, or simulate it on a computer, and see what happens. It can get a bit tricky if the existence or shape of the 'tube' going backwards depends in some way on the particles - that is, if space-time interacts with matter rather than just being a static substrate for it - but it's not really THAT hard to deal with - just let particles carry themselves backward in time if their internal states are configured a certain way, for example.

There are some interesting consequences from this setup if you take the particle motion model quite literally. It resolves some of the usual de-conservation paradoxes from time-travel: e.g. if you transport matter from future to past, you could increase the amount of mass-energy in the universe arbitrarily. The resolution is that these particles normally flow at a certain density, and if you inject more particles by looping them around from the future into the past, you're increasing the density and so you might expect something like a pressure field which resists this proportionately to how much you're trying to squeeze in. E.g. to transport 1kg of mass-energy from future to past, you have to overcome a pressure gradient (do work on the substrate of space-time) costing 1kg of mass-energy. Probably overly detailed for a tabletop campaign, but it's a good excuse for why temporal recursion bombs don't destroy the setting the moment time travel becomes feasible. Another advantage of this compared to branching timelines is that the number of parallel times that can theoretically impinge on a particular space-time coordinate is linear in the period of time that time-travel is available in the universe, not exponential. So while you can have multiple future selves from different parallel futures end up meeting each-other for drinks, you won't get more copies than atoms in the universe suddenly converging on one spot - e.g. it partially resolves timetravel's bright sky paradox; the fact that traveling back takes as long as traveling forward also serves to bound this in practice.

So anyhow, you've got this fluid flow model of time, what happens in practice? Lets say you leave 2020 for 2010 - one consequence is, this should take 10 years of internal time to happen. All of these particles travel at the same speed, just different directions, so if your forward maximal rate of time per meta-time is 1 year per year, that would also be true in reverse. This lets you resolve some of the race conditions you would otherwise get e.g. 'if I'm in 2010 and I make a change to kill someone in the current 2020, who plans to travel back to 2011, do I meet them in 2011 or not?'. The answer is - you do meet them, but it's someone from a 2020 that doesn't reflect your changes yet. Specifically, it's the person from the 2020 of 9 meta-years ago, who was already time-travelling by the time you killed their past self.

If you want to be in a 2011 which doesn't reflect this person's future time-traveling self, you would have to kill them in 2010, then (at any point - doesn't matter when) travel back in time at least 10 years yourself, and afterwards arrange to pass through the corresponding 2011.

In a system like this, you could have all sorts of weird entities where they are bounded to a specific interval of the timeline, but are constantly advancing their own perceptual time (groundhog day loopers). If you passed through a time with a looper, traveled back in time before that period, and passed through it again, the looper would remember your previous visit even if you've changed events since then. E.g. you can't 'erase' someone by making a trivial change to a part of the timeline that is in the past relative to their coordinates and letting that front catch up with them, even if they're standing still in time.

You could also have compound entities where different parts of their body are moving different directions in time from each-other - like a mess of nested loopers with different loop periods who all meet for drinks on Thursday May 14th, 2015.

So, that's all deterministic universe stuff. What happens if there is really true stochasticity in the universe and not just chaos?

Then, traveling backwards in time is guaranteed to place you into an alternate past from the one you remember, no matter what. Because every 'slice' of the stream of future-ward traveling particles corresponds to different random past events for every moment of past time from the beginning of the universe. If that stochasticity isn't incredibly mild, time-travelers are pretty much guaranteed to arrive in deep space - because the planet they live on formed at a slightly different orbital position, which has then been exaggerated by billions of years of orbital motion and interactions. And since the slice width in time (e.g. the interaction radius between moments) must be very very thin in order for cross-time effects to not be noticeable at normal human timescales, this would apply even for imperceptibly short instances of time travel. In a tabletop setting with fixed rounds and spacings, one could imagine that this is actually the fundamental physics of the setting from which the idea of a '6-second round' or '1-second round' or whatever derives: that's basically the interaction range, within which events in absolute time have ambiguous orderings, and only events in internal (perceptual) time have strict orderings. So, time travel outside of this interaction range and you might as well be doing a random planeshift.

Though that does admit the possibility of a more nuanced and sophisticated approach than flinging yourself from moment to moment. What if you could first scry on where you're going to land, combine it with a teleport etc, or even shuffle through nearby moments to find a timeline that you like? Well, the problem is the travel speed of signals. Lets say I send a pulse back 1 second, have it look around, and then have it try to get that message back to me in the present. It's going to be 2 seconds behind me. So I myself can't benefit from this knowledge - that signal is outside of my lightcone. However, there's a resolution which I think is kind of neat thematically:

As long as I'm willing to take a risk that I might not have anywhere to land, I can arrange to meet my signal.

That is to say, I have to send my pulse backwards in time at, say, 1 second per meta-second, while I myself start heading backwards at 1/2 second per meta-second. Once my pulse finds a landing spot for me, it changes direction and travels forwards at 1 second per second. I can still meet my pulse, but once I've committed to this plan I am guaranteed to be unable to return to my own (stable) time if the plan fails. So the first person to do this has to hope beyond hope that having a life-supporting planet within their teleport range is not such a rare thing in the sheaf of possible universes that they'll never find another one. E.g. if you believe in the anthropic principle, this mission would basically be suicidal - you might have to scan through 10^10^100 universes before you find another one that you can land on safely.

Another thing you can do with this is to say, maybe the universe isn't fully stochastic, but has some kind of correlated fluctuations to it maintained by a constant low-level rate of natural time-travel smoothing out the differences between nearby slices. So nearby moments are more similar to each-other than far-away moments, and the further back you try to go, the more what you find looks like an alternate timeline than your own past. This is a lot gentler for tabletop play, and also provides the possibility of there being temporal terrain - different areas of the timestream show different features, and you may have to tunnel down through harsh timezones to find the nice ones again.

jayem
2020-04-25, 08:33 AM
Both fixed and alternate universes have about 5 natural timey-wimey stories in them ("Hey it's ____ time travel", "I can use time travel to profit", "First Competitive time travel", "time travel doesn't help*", "Max-out time travel").
Having the time-travel between more or less disjoint destinations (Dr who is the prime example of this and I quite like NichG's correlated universes), gets maximum time travel fun while stretching out things as much as possible.


*So in stable time-travel, the fundamentals are more or less going to be the same. There's almost no point even trying to go back to stop hitler, either you know you fail or if you succeed it's because hitler was potentially more deadly (such that only WW2 is the good outcome),but if you did naff all that happens anyway...
Of course there is a case where it matters if hitler was actually stopped by your heroic time travel, actual events or say a super villainous thanos gambit (or maybe an amazing subversion of historical record, so WWII was a complete fiction to cover up mankinds emigration to Alpha Cent,which we're going to find out about in 5,4... as they come back to fix climate change). But that is story 5 and you can only do one of them.
*And in an alt-verse time travel, sure you now get to experience the version where hitler is stopped, but all the affects of WW2 on the original world and your memory are there (and if you are fine with that then if someone goes back from your new universe to recreate it, there's nothing you can or need do).
Again there's probably a case where it matters how many WWII's and not-WWII's there are. Some kind of infinite earth crisis.

Satinavian
2020-04-25, 08:53 AM
When i use timetravel it will make heavy use of closed timelines and predestination paradoxa and i avoid alternative timelines.

So there is no use to try to change the past, but timetravel is immensely useful to get information about the past.

EggKookoo
2020-04-25, 10:17 AM
I think the propagating color-line model works better if rather than assuming some kind of universally shared meta-time, you think of the timeline as a stream of particles being emitted from the past to the future - so rather than a given event in time happening 'once', it's constantly re-happening with or without the intervention of time-travellers - it just happens that unless there's an intervention, (in a deterministic universe) it re-happens the same way every time so it appears to not be changing. Note, if we go to a probabilistic universe, this is going to have interesting consequences for what time travel would be like, which is what I eventually want to get to with this idea.

I agree with most of your post, and yeah, I'd like to avoid a literal meta-time if possible. I had been visualizing that every particle or frame of reference has its own internal clock, and the appearance of universal time is mostly an illusion.

I hadn't thought about how having a "speed of time" would limit backward travel, but you're absolutely right. If I travel back to 2010, I will age 10 years during the journey. I better pack snacks! It puts a natural limit on how far you can go. No going back beyond your own natural remaining lifespan without some form of suspended animation or stasis tech. And going forward is pointless -- we're all already doing that. It also degrades the notion that the lack of time travelers in the present means there are no time travelers in the future. Maybe time travel isn't invented until a point in the future from where no one can reach us?

Satinavian
2020-04-25, 10:58 AM
And going forward is pointless -- we're all already doing that. It also degrades the notion that the lack of time travelers in the present means there are no time travelers in the future. Maybe time travel isn't invented until a point in the future from where no one can reach us?
There are other options to explain that.

For example how if a time machine must exist for all times you want to travel too. So building a time machine does mean less that you are now able to travel to the past and more that you are now able to receive visitors from the future.

Red Fel
2020-04-25, 03:09 PM
In our hypertimeline as we've been watching it, EggKookoo was the "first" time traveller, but how do we know that it wasn't actually Red Fel engaging in some nefarious plan of his own that touched neither of them directly? Did either of their time travels interfere with REd Fel's? Cause Red Fel's? be caused by Red Fel's?

I'm gonna say that counts as three.

So, fun fact, timeline theories are actually a hobby of mine. And why, as a storytelling mechanism, I prefer to use multiverse theory. It's cleaner. Basically, pursuant to multiverse theory - or, at least, one commonly accepted version thereof - when you time travel, you aren't actually traveling to a point in your history. Rather, you are traveling to an alternate dimension, identical except for the fact that, in that dimension's history, you traveled there. That is an established historical fact. As a result, neither timeline is disrupted by your actions. Your own past remains the same, having never been changed because you never traveled to it, and this alternate history remains intact, because your having traveled to it was always a thing. Nice and neat, clean and efficient.

However, that doesn't necessarily make for good gameplay. Nothing compelling about saving a completely unrelated timeline. What do my players look like, an eggplant-haired monkey in a midriff-cut denim jacket? For that, I like to dip a little into paradox. Does anyone remember the original Final Fantasy? Well, if you don't, spoilers for a thirty-year-old game:

The game begins with your heroes going to the Temple of Chaos to stop the wicked knight Garland who has kidnapped Princess Sarah. From there, you set forth into the world to defeat the Four Fiends, who have stifled the Four Great Forces - the four elements - and are killing the planet. Once you have succeeded, you discover that they were channeling the Four Great Forces back to the Temple of Chaos, so you return to the Temple and discover a portal to the past. There, you must defeat the Fiends again, and then their wicked master, Chaos. When you engage him, he reveals that he is actually Garland - the Four Fiends in the past summoned him on the moment of his death, using the power of the Four Great Forces, and in the future he - as Chaos - send them into the world to gather those same Forces. It creates a paradox - Chaos exists because you defeated him, and will continue to recreate himself in a temporal loop. This creates a paradox - if you fail to defeat Chaos, he will continue to generate this temporal loop. And clearly you failed, because the Fiends exist in the future. And yet, if you succeed, your story ceases to exist, because without the Fiends in the future, your heroes will never be summoned to save the world. Obviously, you win and your heroes fade into obscurity.
It makes for great tragedy. But I don't like tragedy. I like triumphant heroic stories. (Or, you know, stories of inevitable descent into corruption. As I call them, comedies.) So how to fix?

Predestination paradox. The PCs travel to the past because history shows that they did. The record is conveniently obliterated as to what specifically they did or whether they were successful, but it is clear that they did. Because the record shows that the PCs traveled to the past, there is no paradox from the fact that they travel to the past. What, you want another illustration? Have some Gargoyles.

David Xanatos claims to be a self-made multi-billionaire. In fact, his fortune began because a mysterious benefactor sent him an ancient coin in a sealed envelope, worth thousands of dollars in modern currency - money he used to build his empire. In one episode, he travels with his fiancee and father into the past, to engage in some shenanigans. In the process, he earns a favor from a royal who happens to be a member of a secret society. He gives him one envelope with some local currency in it - the very coins he would receive a thousand years later - with instructions to mail them to the young him in the future. He gives another envelope, to be given to him the morning of his time travel adventure, containing instructions on everything he did that day. In this way, he creates the circumstances of his own fortune, and ultimately the very circumstances under which he would travel to the past eventually.
Okay, so how do we ensure that they only do so in ways sanctioned by history? That's easy. Fiat. Time travel only works under certain circumstances. It's not a spell or ritual, it's a particular place and time connecting to another particular place and time. It's just Point A to Point B. Think of it like a very particular Stargate, that only operates in certain coordinates in both space and time. After all, you can't have the PCs traveling through time willy-nilly.

Unless, of course, it's a time-travel adventure. In that case, do whatever you want and throw causation to the wind. Who's to say that, because the PCs travel one hundred years into the past, the entire continent doesn't become a mega-nation with its national language being Esperanto?

Not I. Not I.

DataNinja
2020-04-25, 04:31 PM
Achronal is an RTS that handles something others mentioned here rather interestingly. Basically, the meta-time concept I see discussed does exist in a very tangible way in the form of entities called 'time waves' that propogate time forward from where they catch up with time. So paradoxes actually have simple solutions: they'll alternate which state is true each time a time wave moves past them. As a result, any period within two waves is internally consistent, if you're willing to accept that things can pop up out of nowhere as not breaking consistency (as that's what appears to happen when things move from one set of waves to another). And you can (and, if you want to win, should) either avoid or trigger results of time catching up to a unit by time-travelling past or into a time wave. The game's almost a decade old now, but one should still be able to dredge up old footage or guides of it if they want to see some applied time shenanigans.

Yeah, Achron was definitely the thing that came to mind when the "time waves" thing was mentioned.



For my own time travel story, one game that I'm running for a player involves some time travel, but more of a... overarching plot thing. A time traveller came back from the future to try and bring something from her past back to her time in order to keep it safe from an apocalypse that would ravage the world.

In this case, time tries to repair itself. You can make all the changes you want, but the further away you get from the traveller's change, then the closer it gets to the original. If you kill a dictator, then someone else will rise to take their place, and things will remain fundamentally the same. If you kill the founder of a town that's named after them, that town will still be there, just likely with a different name. In a less lethal sense, if you get a time traveller to go back to prevent a mistake you make, because it ruined your life... you'll avoid making that mistake, but things will conspire so you end up making a mistake equally as bad that you regret as equally. Bigger changes might take longer to 'correct', but you can't escape what happens.

Time travellers basically never go into the future, because by observing it, you can never change it. If it's bad... you're out of luck.

And then to resolve personal paradoxes... if two time-versions of things or people exist at the same time, the version that arrived there via time-travel begins to deteriorate. People get mental anguish, then eventually begin to physiologically shut down, while inanimate objects begin to corrode or rot or whatever into dust.

Mutazoia
2020-04-27, 09:58 PM
Time travellers basically never go into the future, because by observing it, you can never change it. If it's bad... you're out of luck.

*coughTheTimeMachinecough*

The main reason not to go into the future is not that you then set things as a fixed event, but because it's harder to know you are going to "land" in a safe location. The ground you are standing on "now" may be a pool of molten lava in a hundred years, or ground zero for a nuclear blast with skin melting levels of radiation, or simply be the new location of a rather sturdy wall.

There was a short story I read a while back, the name escapes me at the moment. But the basic plot was that time travel had been invented, and people only went forward in time, as they figured out nothing could be learned from going backward. So temporal archeologists would go forward in time and study what they found there. So in the book, a man's father goes forward in time and never comes back. He goes looking for him but doesn't find him. He finds traces of him having been there (everything is in ruins) and he finds his claim markers. And a knife. The knife is made from no metal known to man. He takes the knife back and scientists start studying it, shaving off a small piece to analyze the metal. He eventually figures out that where he found the knife was the ruins of where they were studying it, and the realizes that the knife has been traveling back in time over and over, getting thinner and thinner each time as it is "discovered" and brought back for analysis again and again.

Which brings us to...


And then to resolve personal paradoxes... if two time-versions of things or people exist at the same time, the version that arrived there via time-travel begins to deteriorate. People get mental anguish, then eventually begin to physiologically shut down, while inanimate objects begin to corrode or rot or whatever into dust.

We've watched enough Dr. Who, Star Trek 3, Quantum Leap, Back to the Future, etc. to know that personal paradoxes don't exist. The universe hates a paradox, which is why you can't go back in time and kill your grandfather as a baby. A good example of this is "The Time Machine" rule.

"The Time Machine" rule is simply this: If you create a time machine to go back in time to stop an event, that event can never be changed. Like our poor hero in the book found out when he created a time machine to keep his wife from dying.

Why? His wife's death was the direct cause of the time machine being created.

If he manages to stop his wife from dying, he has no reason to create the time machine, and thus can't go back in time to save his wife. Since he can't save his wife, he decides to create the time machine to go back and save his wife. Once he saves her life, he doesn't have a reason to create the time machine....repeat ad nauseam. This is why, no matter how many times he went back in time, he could never save his wife.

Which is why you can't go back and kill your grandfather as a baby. The moment you do, you stop your birth. Since you were never born, you can't go back in time and kill your grandfather as a baby...

Dr. Who has labeled certain events as "fixed points in time" (kind of like Sean Bean deaths) and things like the above are prime examples. Everyone will have personal fixed points that they can't change (or have changed for them). A villain can't go back in time and kill the hero's mother before he's born, as Skynet found out (the hard way). The moment the hero's mom dies, the future/present villain has no reason to go back in time (or send someone/something back).

This makes going back in time and altering events difficult.

One way theorists and sci-fi writers have gotten around this is the theory of alternate timelines. Every time you change a thing in the past, everything you experience from then on is an alternate history. Even if you immediately jump forward (go back to your own "time") in time right after you make your change, you will simply be jumping forward on the new timeline. Your memories of your old timeline will not be erased or changed, because you did live them (or learn about them in history class), they just don't apply on the new timeline, which is basically an alternate universe. So in a sense, you are not really time traveling at all, just hopping between an infinite number of alternate universes, based on the things you choose to change in the "past". Each time edit shifts you imperceptibly into an alternate reality, kind of like "Sliders" without the glowing wormhole. Fortunately, "The Time Machine" rule still applies, but it IS possible to find an alternate timeline where you were never born in the first place (or were born the opposite gender, or in a different country, etc) because of events that you, yourself (or your enemies) never changed via time travel.

Honestly, I could go on about this for days, but I would run out of characters long before I exhausted this topic.

Segev
2020-04-27, 10:30 PM
If he manages to stop his wife from dying, he has no reason to create the time machine, and thus can't go back in time to save his wife. Since he can't save his wife, he decides to create the time machine to go back and save his wife. Once he saves her life, he doesn't have a reason to create the time machine....repeat ad nauseam. This is why, no matter how many times he went back in time, he could never save his wife.

Which is why you can't go back and kill your grandfather as a baby. The moment you do, you stop your birth. Since you were never born, you can't go back in time and kill your grandfather as a baby...

Won't help with the grandfather one, but for saving his wife, all he has to do is arrange for it to look like his wife died in the same way that inspired him to come back to save her, and rescue her and bring her back to the future with him. He is thus still inspired to build the time machine and go back to save her and leave the faked death to inspire him to go build the time machine so he still goes back to save her.

LordCdrMilitant
2020-04-27, 10:46 PM
As it says in the title. How have you used time travel in your games? What have you done to make it work really well? I'm running a Doctor Who campaign and another one that I'm considering putting some eon-hopping into, but I'm sure the Playground can enlighten me on ways to do time travel better, or just share some silly stories!

I had a session of Black Crusade where two party members, as a consequence of doing all the warp-powered space-crack [don't do drugs kids. If you do, the Keeper of Secrets will eat you], were displaced out of time.

I had three time travel scenes: one several years prior, one several months prior, and one in the future.

The one several years prior was actually a scene from a previous Dark Heresy campaign with different players in the same sector. I had the displaced player experience the scene one of the scene's participants, in which they had enough agency to gather information and interact with the scene but didn't really make a meaningful difference to the outcome.

The one in the future I ran by asking one player how he saw his character in the future. The displaced player wound up experiencing the scene as that player. I basically just estimated where they party would be in the future for what was happening. There was a pretty trippy moment where he talked to his future self.

The last one was a few months in the recent past from the campaign, where two players experienced the scene as other characters in the scene, once again they had enough agency to play the scene and have some humorous confusion, but the scene fundamentally turned out the same way.


I left it deliberately ambiguous as to whether or not they were participating in and altering the actual event of the past, whether it had actually happened that way already and the timeline just can't be changed, or if they were experiencing a simulation of the past/future that they could gather information in but it wouldn't change reality. [though the "correct answer" is "all three, to some degree".]

DataNinja
2020-04-29, 02:07 AM
*snip*

Oh, I'm fully aware that the way I did it is certainly not the "standard", or even a generally used form of time travel - I was simply saying how it happened to work in my campaign, which was deliberately set in a way so that PCs don't need to worry about breaking things terribly via careening around.

I apologize if my post gave the impression that I was trying to say "this is how time travel works" from an absolute point. The OP just wanted stories of how we'd done them.

EggKookoo
2020-04-29, 05:41 AM
Won't help with the grandfather one, but for saving his wife, all he has to do is arrange for it to look like his wife died in the same way that inspired him to come back to save her, and rescue her and bring her back to the future with him. He is thus still inspired to build the time machine and go back to save her and leave the faked death to inspire him to go build the time machine so he still goes back to save her.

He would have to fake her death in a way that looked like an actual death. So he can't just grab her and bring her to the future. She's not dead then, but rather she's now "missing." Whatever he does, it needs to leave behind a convincing body or it needs to "kill" her in a way that it makes sense that there is no body, without also triggering "missing, not dead."

I mean sure, it could be done, but it's not quite as simple as it might seem at first.

Millstone85
2020-04-29, 11:12 AM
Anyway, alternate timelines is fine but it also feels kind of weak from a narrative or storytelling perspective. If you "change the past" but really just make a new universe, you're less time-traveling and more universe-hopping. Which is fun in its own right but not quite the same thing.I very much share that opinion.


Continuum is an RPG all about time travel you might be able to take some notes from. Of particular note is the idea that the universe itself reacts to sapient will and intentions, so some of the headache of time-dealing can be pasted over because they don't really effect you until you're aware they should.I haven't paid much attention to the mechanics of C°ntinuum, but I love the setting.

The idea is that post-humans, with the super cool name of Inheritors, travel almost all the way back to the Big Bang and colonize the entire universe, leaving only the Earth in a bubble of preserved causality. It turns the Fermi paradox into a time-travel one.

And one of the factions hate this. "Humanity does not make it to the stars", they say, since the Inheritors no longer qualify as human. The faction's efforts are directed toward "crashing free" into alternate timelines, which they insist can exist. Ironically, said efforts often turn them into a different kind of post-human.


Also, introduces some useful terminology for time travelers, like how to talk about your personal past and future seperate from the world's. Things you've done (personal past) are in your Age, things you're going to do (personal future) are in your Yet. normal past and future refer to the universe'sI especially like how the present tense is encouraged when not talking about your Age or Yet. Not only is it an elegant solution, but things like "WW2 begins in 1939" really illustrate the belief that the timeline is what it is.

Segev
2020-04-29, 11:48 AM
He would have to fake her death in a way that looked like an actual death. So he can't just grab her and bring her to the future. She's not dead then, but rather she's now "missing." Whatever he does, it needs to leave behind a convincing body or it needs to "kill" her in a way that it makes sense that there is no body, without also triggering "missing, not dead."

I mean sure, it could be done, but it's not quite as simple as it might seem at first.

Oh, indeed. It's not simple. In fact, you could construct an entire story or story arc around it.

Quertus
2020-04-29, 08:37 PM
Shrug. I'm a fan of the "create an alternate reality" model, outside of single author fiction. It's… much more workable in a game.


Won't help with the grandfather one, but for saving his wife, all he has to do is arrange for it to look like his wife died in the same way that inspired him to come back to save her, and rescue her and bring her back to the future with him. He is thus still inspired to build the time machine and go back to save her and leave the faked death to inspire him to go build the time machine so he still goes back to save her.

At last, someone who gets it. If I had (will have? Tenses are either hard or irrelevant here) a time machine, I might just leave it to you.

vasilidor
2020-04-29, 08:38 PM
in a game i am currently running, multiple people have tried to do time travel with science/magic. everytime someone comes up with a machine/spell/mechanism with which to do so and turn it on, the machine/caster/mechanism disappears and in its place is a book called "why time travel is a Bad Idea."

otherwise i think what would actually happen with time travel is it would incontrovertible change some aspect of the future. you would never be able to go to the future and see your future self, why because you just jumped forward in time, any interaction with the past would change your present. you may not be capable of perceiving the changes, but they would be there nonetheless. an example of changes you would not notice is your presence interfered with a bee colony, now that bee colony is slightly larger do to it trying to go into a reproductive frenzy resulting in slightly more bees, about 5-10% after die off, due to your interference. ultimately no matter how hard you tried there would be some sort of change. if you are lucky, or unlucky, you cannot notice the changes.

Mutazoia
2020-04-29, 09:22 PM
He would have to fake her death in a way that looked like an actual death. So he can't just grab her and bring her to the future. She's not dead then, but rather she's now "missing." Whatever he does, it needs to leave behind a convincing body or it needs to "kill" her in a way that it makes sense that there is no body, without also triggering "missing, not dead."

I mean sure, it could be done, but it's not quite as simple as it might seem at first.

So, you're saying that one could convince multiple doctors, nurses, police, morticians, family, and friends all to conspire to pretend she is dead, just so you can wait the several years it takes yourself to invent the time machine?

Most likely what will happen is: She dies. The grief-stricken present/past you shambles off to lock himself away to invent the time machine. Almost as soon "you" are out the door, future you comes back in and injects the wife with a miracle drug that saves her life. You astound the doctors and take your wife "home" to "recuperate" (wisk her off to the time machine to bring her back to the present/future). The doctors are excited about this miracle cure, and news spreads. Doctors swing by your home to question "you" about the drug. Naturally, you know nothing and insist your wife is dead. The doctors, who saw you walk out with your wife, now suspect foul play and contact the police. With several witnesses who saw you two leave, you are now arrested in the murder of your wife, with the theory that you originally poisoned her, but gave her the antidote so you could kill her and dispose of the body privately (foiling an attempt an autopsy). You are convicted of murder and sentenced to death. The time machine never gets built, so you never go back in time to save your wife.....

The ONLY loophole in "The Time Machine" rule is if your wife vanishes with no witnesses, such as falling overboard on a cruise ship at night, or goes for a walk one day and never returns...any scenario in which the wife simply vanishes, without leaving a body, and nobody saw what happened. Then you could be the one to abduct your own wife back to the "future". Provided that you could find sufficient motivation to develop the time machine to go back in time, rather that waiting for your wife to come home some day.

Quertus
2020-04-30, 06:30 AM
Let's go with "the Time Machine" physics, because it's known, and a good example.

So, your wife dies. Every time you go back in time to save her, she still dies, because, otherwise, you would never have bothered to build the time machine.

OK, fine. However, nothing else is sacred. Like, that poor guy who ran her over that one time, his life is clearly changed by your meddling.

So, one simple answer is to have a bomb explode somewhere where you *know* your wife is. You simple abduct her before the bomb goes off, boom, done.

Now, maybe you ought to take her to the future, flash clone her, strip her, dress the flesh doll in her clothes, and drop it off in time for the big bang.

Any reason now why you wouldn't a) still build a time machine, and b) exit the loop with your wife intact?

Questions about her sanity, or willingness to remain married to you notwithstanding.

EggKookoo
2020-04-30, 07:49 AM
Any reason now why you wouldn't a) still build a time machine, and b) exit the loop with your wife intact?

A much simpler approach would be to go back in time and talk to yourself.

"Ok, here's the deal. Your wife didn't really die yesterday. I came back in time and took her to my time moments before her death. We're living out our lives together. You know that time-concept you have in the back of your head? Well, her disappearance will prompt you to build a functional time machine, with the goal of coming back here and finding her. Trust me, I've thought about this. It's the only way to save her and be able to be with her. Don't worry about your ability to pull it off. The fact that I'm here means you succeed. Okay? Okay, good talk. I'll see you again when you're me."

Millstone85
2020-04-30, 08:43 AM
A much simpler approach would be to go back in time and talk to yourself.

"Ok, here's the deal. Your wife didn't really die yesterday. I came back in time and took her to my time moments before her death. We're living out our lives together. You know that time-concept you have in the back of your head? Well, her disappearance will prompt you to build a functional time machine, with the goal of coming back here and finding her. Trust me, I've thought about this. It's the only way to save her and be able to be with her. Don't worry about your ability to pull it off. The fact that I'm here means you succeed. Okay? Okay, good talk. I'll see you again when you're me."You could even skip the fake-death part.

"Ok, here is the deal. If your wife is in Bridge Street tomorrow at 4pm, she will die. Have her take a small detour. Also, do you remember that diagram with the 8 ball?

https://i.imgur.com/6UkawIgm.png

Well, we are the ball pushing itself toward the wormhole. You have to build a functional time machine, with the goal of coming back here and telling yourself all this."

Quertus
2020-04-30, 12:28 PM
A much simpler approach would be to go back in time and talk to yourself.

"Ok, here's the deal. Your wife didn't really die yesterday. I came back in time and took her to my time moments before her death. We're living out our lives together. You know that time-concept you have in the back of your head? Well, her disappearance will prompt you to build a functional time machine, with the goal of coming back here and finding her. Trust me, I've thought about this. It's the only way to save her and be able to be with her. Don't worry about your ability to pull it off. The fact that I'm here means you succeed. Okay? Okay, good talk. I'll see you again when you're me."


You could even skip the fake-death part.

"Ok, here is the deal. If your wife is in Bridge Street tomorrow at 4pm, she will die. Have her take a small detour. Also, do you remember that diagram with the 8 ball?

https://i.imgur.com/6UkawIgm.png

Well, we are the ball pushing itself toward the wormhole. You have to build a functional time machine, with the goal of coming back here and telling yourself all this."

This… doesn't violate the physics of time travel from "the Time Machine" (as I understand such), but may violate human psychology, depending upon the couple in question.

For this particular wrinkly bit, I might try letting them *both* in on the details, and make sure that they *both* know that the only way to save her life is to have him obsessively build the time machine. Otherwise, she dies. Depending on the couple, you may get more or less dedication to the project under those conditions.

Now, even if the psychology of the couple is such that you get adequate dedication to the project, there is still another potential problem. Specifically, the problem here is if completing the time machine requires not just time (heh) and dedication, but a certain… mad brilliance, that wouldn't be present if she lived.

This is why I went with the… more certain approach of faking her death. But, yes, there are certainly… "better" plans to try before murdering people just to save the one you love, especially if you have, you know, a time machine, no?

jayem
2020-04-30, 03:19 PM
ThisÂ… doesn't violate the physics of time travel from "the Time Machine" (as I understand such), but may violate human psychology, depending upon the couple in question.

From a game perspective it also has the disadvantage that the moment of choice comes after the plot (and indeed effectively it's success) is revealed.

With the established fact of the (false perception of) the death, the player has to work to get what they want out of the 'known' facts or admit defeat.

If the player is informed in advance what they did, in theory they could spend the interim years exploiting their effective immortality and the leave the GM to force the time travel (or write them a letter from long lost uncle Joe "Your wife said you were stupid enough to believe in time travel") or the players can follow the rails obediently.

From an abstract story point of view, both can work, but with different moments of authorial cleverness and suspense.

Mutazoia
2020-04-30, 08:59 PM
From a game perspective it also has the disadvantage that the moment of choice comes after the plot (and indeed effectively it's success) is revealed.

With the established fact of the (false perception of) the death, the player has to work to get what they want out of the 'known' facts or admit defeat.

If the player is informed in advance what they did, in theory they could spend the interim years exploiting their effective immortality and the leave the GM to force the time travel (or write them a letter from long lost uncle Joe "Your wife said you were stupid enough to believe in time travel") or the players can follow the rails obediently.

From an abstract story point of view, both can work, but with different moments of authorial cleverness and suspense.

Speaking from a purely game-centric standpoint, time travel needs to be carefully controlled, lest you have your players repeatedly looping back in time, trying every possible permutation of actions until they get the optimal outcome. (The old series "Red vs Blue" comes to mind.)

Quertus
2020-05-01, 03:11 AM
Speaking from a purely game-centric standpoint, time travel needs to be carefully controlled, lest you have your players repeatedly looping back in time, trying every possible permutation of actions until they get the optimal outcome. (The old series "Red vs Blue" comes to mind.)

Isn't that the point of "groundhog day" gaming? :smallconfused: Are you accusing perfectionists of BadWrongFun? :smallamused:


From a game perspective it also has the disadvantage that the moment of choice comes after the plot (and indeed effectively it's success) is revealed.

With the established fact of the (false perception of) the death, the player has to work to get what they want out of the 'known' facts or admit defeat.

If the player is informed in advance what they did, in theory they could spend the interim years exploiting their effective immortality and the leave the GM to force the time travel (or write them a letter from long lost uncle Joe "Your wife said you were stupid enough to believe in time travel") or the players can follow the rails obediently.

From an abstract story point of view, both can work, but with different moments of authorial cleverness and suspense.

"the player has to work to get what they want out of the 'known' facts or admit defeat" - and this differs from (roughly) every game ever how, exactly? Isn't "find some way to win within the rules, or admit defeat" all but the definition of a "game"? :smallconfused:

What makes this tricky is that the game (or, at least, the core gameplay centered around the specific events of "The Time Machine", and currently under discussion) involves human psychology. This not only turns the game into "mother may I", but has the added detriment that you may learn more about your GM's misunderstandings of humanity than you ever cared to know. :smalleek:

But, no, I don't consider "established fact" and "rails" to be synonyms - especially when, for example, I could (theoretically) travel to an ("alternate") future, install "dedication" wetware, go back in time, save my wife, build time machine.

There are so many creative paths forward from the starting point of "the Time Machine"; only a bad railroading GM makes the setup + physics of "the Time Machine" into a railroad.

EDIT: thinking about uncreative railroad GMs reminds me of this recent Dilbert comic (https://dilbert.com/strip/2020-01-25).

NichG
2020-05-01, 06:26 AM
The thing that bothers me about 'you can't change established events' is that it implicitly promotes the idea of a preferred observer, and that's fundamentally a meta-game construction. That is to say, it in practice gives precedence to things which have been explicitly seen onscreen. That kind of meta-game structure can work, but I think it requires going all-in (PCs are literally chosen ones, there is literally an Observer or set of Observers, etc) or it starts to feel awkward or contradictory.

There's a construction like this in Timemaster (a Robert Forward sci-fi novel) where to use a time machine to head off natural disasters and terrorist events, they establish a reporting protocol where certain details are intentionally omitted from future reports - whether or not the event was successfully headed off, for example. The idea was then that this would free them to be able to intervene without contradicting future information they possessed. But to me, just because the person who wrote the message didn't include whether or not the event was prevented explicitly, that doesn't change whether or not there was a causal connection between the specific outcome of the event and the specific message.

For example if there was a bombing and someone wrote a message 'attempted bombing on such and such date', then one could imagine that handwriting analysis could determine their emotional state and thereby provide different information whether the bombing happened or was prevented. If it's a digital message, the exact timing of the point of origin of the message relative to the event which provoked it could be similarly informative; or the wording used. And at the level of physics, even if its not possible for a human to interpret, atoms would be in different positions and so on.

So changing the choice of what information to include (or 'faking' an event) shouldn't change the probabilities of whether the event went well or poorly. However framing it this way gives players the impression that they could influence those probabilities by being clever in what information they include or hide. Which creates an opportunity for desync between the GM's understanding of what makes sense, and players' understanding of what makes sense. Preventing that desync requires the explicit meta-game construction that 'only things seen by you on-screen matter' and, e.g., some side NPC also receiving future information or performing handwriting analysis or whatever doesn't factor in.

Segev
2020-05-01, 10:53 AM
The thing that bothers me about 'you can't change established events' is that it implicitly promotes the idea of a preferred observer, and that's fundamentally a meta-game construction. That is to say, it in practice gives precedence to things which have been explicitly seen onscreen. That kind of meta-game structure can work, but I think it requires going all-in (PCs are literally chosen ones, there is literally an Observer or set of Observers, etc) or it starts to feel awkward or contradictory.

There's a construction like this in Timemaster (a Robert Forward sci-fi novel) where to use a time machine to head off natural disasters and terrorist events, they establish a reporting protocol where certain details are intentionally omitted from future reports - whether or not the event was successfully headed off, for example. The idea was then that this would free them to be able to intervene without contradicting future information they possessed. But to me, just because the person who wrote the message didn't include whether or not the event was prevented explicitly, that doesn't change whether or not there was a causal connection between the specific outcome of the event and the specific message.

For example if there was a bombing and someone wrote a message 'attempted bombing on such and such date', then one could imagine that handwriting analysis could determine their emotional state and thereby provide different information whether the bombing happened or was prevented. If it's a digital message, the exact timing of the point of origin of the message relative to the event which provoked it could be similarly informative; or the wording used. And at the level of physics, even if its not possible for a human to interpret, atoms would be in different positions and so on.

So changing the choice of what information to include (or 'faking' an event) shouldn't change the probabilities of whether the event went well or poorly. However framing it this way gives players the impression that they could influence those probabilities by being clever in what information they include or hide. Which creates an opportunity for desync between the GM's understanding of what makes sense, and players' understanding of what makes sense. Preventing that desync requires the explicit meta-game construction that 'only things seen by you on-screen matter' and, e.g., some side NPC also receiving future information or performing handwriting analysis or whatever doesn't factor in.

In the "single fixed timeline" version of things, it's not that there's a preferred observer. It's that things DID happen as they happened.

Let's take the disney-death example of Bob falling to his death into a pit of lava, corpse never found after it burns to ashes before anybody can get to it. If all Alice and Dave see is Bob fall over the side, then they have no idea what happened after that. They can conjecture that there's a high probability that Bob fell to his doom, but they don't know for sure.

In the classical version of this storyline, Alice and Dave (or at least one of them) orchestrates a time heist to steal Bob's falling body from the air so that what Alice and Dave saw happen isn't altered, because they know that what Alice and Dave saw happened and is immutable. But they also know that there are ways Bob could have survived that Alice and Dave didn't see.

Let's put a twist on this, though. Alice and Dave are not adept time travellers with protocols for protecting themselves from future knowledge or the skill to pull off a time heist that fools their past selves. But they're not so inept that they can't save their friend Bob as he's falling to his doom, given time-and-space teleportation capabilities. Alice rushes after Bob, shouting his name as he falls and looks over the side of the cliff. Because the timeline is fixed, and Dave and Alice definitely do go to get their time machine to save Bob, Alice sees the time machine appear below her and sees Dave catch Bob while Alice holds the machine steady.

The two actual reasons why more experienced and supposedly-savvy time travellers Charlie and Erin avoid looking over the side of the cliff is to give themselves hope, and to promote dramatic tension for the audience. The audience doesn't know that Bob definitely survived if Charlie and Erin don't, so even as Charlie and Erin attempt their time-rescue, the audience is theoretically tense and unsure if they'll succeed (or at least as unsure as if they were watching Bob fall to his doom and wondering how he'd be saved in a non-time-travel movie).

Meanwhile, for Charlie and Erin, it gives them hope in the uncertainty because this way they don't see Bob definitely die, and it MIGHT be possible they could rescue him.

It's fooling themselves, essentially, because if the timeline is truly fixed, it doesn't matter if they know they'll rescue Bob or not; Bob gets rescued whether Alice sees his rescue or merely sees nothing at all by the time she peers over the side.

Necroticplague
2020-05-01, 11:43 AM
The thing that bothers me about 'you can't change established events' is that it implicitly promotes the idea of a preferred observer, and that's fundamentally a meta-game construction. That is to say, it in practice gives precedence to things which have been explicitly seen onscreen. That kind of meta-game structure can work, but I think it requires going all-in (PCs are literally chosen ones, there is literally an Observer or set of Observers, etc) or it starts to feel awkward or contradictory.

There's a construction like this in Timemaster (a Robert Forward sci-fi novel) where to use a time machine to head off natural disasters and terrorist events, they establish a reporting protocol where certain details are intentionally omitted from future reports - whether or not the event was successfully headed off, for example. The idea was then that this would free them to be able to intervene without contradicting future information they possessed. But to me, just because the person who wrote the message didn't include whether or not the event was prevented explicitly, that doesn't change whether or not there was a causal connection between the specific outcome of the event and the specific message.

For example if there was a bombing and someone wrote a message 'attempted bombing on such and such date', then one could imagine that handwriting analysis could determine their emotional state and thereby provide different information whether the bombing happened or was prevented. If it's a digital message, the exact timing of the point of origin of the message relative to the event which provoked it could be similarly informative; or the wording used. And at the level of physics, even if its not possible for a human to interpret, atoms would be in different positions and so on.

So changing the choice of what information to include (or 'faking' an event) shouldn't change the probabilities of whether the event went well or poorly. However framing it this way gives players the impression that they could influence those probabilities by being clever in what information they include or hide. Which creates an opportunity for desync between the GM's understanding of what makes sense, and players' understanding of what makes sense. Preventing that desync requires the explicit meta-game construction that 'only things seen by you on-screen matter' and, e.g., some side NPC also receiving future information or performing handwriting analysis or whatever doesn't factor in.

Continuum also goes a bit on this idea: Sentient Force (although, for my pedantry, Sapient Force is more accurate) is essentially a tangible force that acts on the timeline to determine 'when' things happen from a gameplay perspective.

Say, for instance, you are going to annoy another Spanner, who decides to pester you by grandfather paradoxing you. Not out of existence, since The Universe Is, but at least apply a bit of Frag (time damage) to you. When in your Age do you take the damage? The moment he gets annoyed enough to Span away to do it. At that point, she has applied Sentient Force to the timeline, and the changes thus propogate. In-game, this would be when she takes the Action to do so in time combat, occurring during our real-life linear time. You wouldn't take it from the time in your personal past when the event came to be because the Sentient Forces had not met then, while they are now.

This does, however, mean that 'what they don't know won't hurt them' is basically an actual rule. And thus, the reason time travelers tend to hold their cards incredibly close to their chest: information about the Age and Yet is almost literally a weapon. Things you know happened can't be changed by you without creating a paradox without getting clever (since you would now have a memory of something that never happened), but things you intentionally remain ignorant about (or are kept ignorant about, "Further Information is not available at this time" is a common saying for these situations) give you some more wiggle room in that regard. Thus, 'if you think something bad will happen, look away so you have the most wiggle room to change it later' is actually a common practice among time travelers.

The fact Sentient Force is required to change time also has some convenient narrative applications: runaway unintended butterfly effects don't happen because that wasn't what the Force was applied to, so the narrative is at followable. Even when you declare things happened in the past or will happen in the future (like Slipshanking) have definite moments in the meta-time of a gameplay session when they occur. Before I took that action to Slipshank, that gun was never there. After I did, it had always been there. And the Force the action represented is what made the difference. And yes, only things 'on-screen' counted, because otherwise, Sentient Forces haven't met.

jayem
2020-05-01, 01:52 PM
"the player has to work to get what they want out of the 'known' facts or admit defeat" - and this differs from (roughly) every game ever how, exactly? Isn't "find some way to win within the rules, or admit defeat" all but the definition of a "game"? :smallconfused:

That's the point, in the "wife (appears to) die" version, you get a game. The player sees the consequences of the decisions after they've made them. The GM may have a bit of running round, particularly if the player tries to produce an obvious contradiction (but then the player deserves everything they get), but they get off pretty lightly. Everythings playable.

In the other version, "the player goes back in time and tells the player not to be an idiot", problems arise from the start.
I would contend that in this case the player doesn't have to admit defeat, and so can get what they want for nothing and hence (as in your reasoning) you don't get a game.
The first chronological event from the players perspective is "someone turns up", who decided that was what the player WILL do? The player (or the GM) is then told the events of the next X sessions, or at least the inevitable conclusion. Once this is set down, it's (almost) set down, the one fixed point of the game is that you will win. To put it in chess metaphors, you've been told that you white will win ending in such a position, you could follow the opening etc that is planned, or you could move f3 g4 and watch black desperately struggle.

You could bubble-verse it, so you see your wife die, go back in time and change reality, but that's a different model (and probably has NichG's problem of a privileged observer)

Segev
2020-05-01, 02:13 PM
That's the point, in the "wife (appears to) die" version, you get a game. The player sees the consequences of the decisions after they've made them. The GM may have a bit of running round, particularly if the player tries to produce an obvious contradiction (but then the player deserves everything they get), but they get off pretty lightly. Everythings playable.

In the other version, "the player goes back in time and tells the player not to be an idiot", problems arise from the start.
I would contend that in this case the player doesn't have to admit defeat, and so can get what they want for nothing and hence (as in your reasoning) you don't get a game.
The first chronological event from the players perspective is "someone turns up", who decided that was what the player WILL do? The player (or the GM) is then told the events of the next X sessions, or at least the inevitable conclusion. Once this is set down, it's (almost) set down, the one fixed point of the game is that you will win. To put it in chess metaphors, you've been told that you white will win ending in such a position, you could follow the opening etc that is planned, or you could move f3 g4 and watch black desperately struggle.

You could bubble-verse it, so you see your wife die, go back in time and change reality, but that's a different model (and probably has NichG's problem of a privileged observer)
One way to handle this is the same way the "save your wife from death by deceptive time travel" scenario works:

All the player knows for sure is that somebody who claimed to be his PC from the future - who could be telling the truth or could be a convincing liar, for all that he's able to prove - has told him how things are going to go.

If the player goes along with this, and struggles and strives to make it all happen, the GM can choose to massage things to ensure it will work out that way. Bam, loop fulfilled. If the player does NOT go along with this, or if the dice and/or player choices (despite best intentions) flub it to the point that it's impossible, the GM could have a backup, alternate scenario where it never was the PC's future self; it was Dastardly Doppelganstro, pretending to be the PC from the future in order to try to trick the PC into following Dastardly's scheme.

NichG
2020-05-01, 03:24 PM
In the "single fixed timeline" version of things, it's not that there's a preferred observer. It's that things DID happen as they happened.

Let's take the disney-death example of Bob falling to his death into a pit of lava, corpse never found after it burns to ashes before anybody can get to it. If all Alice and Dave see is Bob fall over the side, then they have no idea what happened after that. They can conjecture that there's a high probability that Bob fell to his doom, but they don't know for sure.

In the classical version of this storyline, Alice and Dave (or at least one of them) orchestrates a time heist to steal Bob's falling body from the air so that what Alice and Dave saw happen isn't altered, because they know that what Alice and Dave saw happened and is immutable. But they also know that there are ways Bob could have survived that Alice and Dave didn't see.

Let's put a twist on this, though. Alice and Dave are not adept time travellers with protocols for protecting themselves from future knowledge or the skill to pull off a time heist that fools their past selves. But they're not so inept that they can't save their friend Bob as he's falling to his doom, given time-and-space teleportation capabilities. Alice rushes after Bob, shouting his name as he falls and looks over the side of the cliff. Because the timeline is fixed, and Dave and Alice definitely do go to get their time machine to save Bob, Alice sees the time machine appear below her and sees Dave catch Bob while Alice holds the machine steady.

The two actual reasons why more experienced and supposedly-savvy time travellers Charlie and Erin avoid looking over the side of the cliff is to give themselves hope, and to promote dramatic tension for the audience. The audience doesn't know that Bob definitely survived if Charlie and Erin don't, so even as Charlie and Erin attempt their time-rescue, the audience is theoretically tense and unsure if they'll succeed (or at least as unsure as if they were watching Bob fall to his doom and wondering how he'd be saved in a non-time-travel movie).

Meanwhile, for Charlie and Erin, it gives them hope in the uncertainty because this way they don't see Bob definitely die, and it MIGHT be possible they could rescue him.

It's fooling themselves, essentially, because if the timeline is truly fixed, it doesn't matter if they know they'll rescue Bob or not; Bob gets rescued whether Alice sees his rescue or merely sees nothing at all by the time she peers over the side.

Well, this is why I said it's a meta-game effect and not a game effect. In terms of the way the universe works as presented, it shouldn't matter if the PC Alice looks over the cliff or not. However, because it's a game, Alice's player increases their agency by not looking - if they look, they are asking the GM to make decisions about the trajectory of events, but if they don't look then they the player get to make decisions about that trajectory instead.

So choosing to look or not isn't supposed to matter, but it actually does matter in (the easiest form of) tabletop implementation of this idea.

Segev
2020-05-01, 03:38 PM
Well, this is why I said it's a meta-game effect and not a game effect. In terms of the way the universe works as presented, it shouldn't matter if the PC Alice looks over the cliff or not. However, because it's a game, Alice's player increases their agency by not looking - if they look, they are asking the GM to make decisions about the trajectory of events, but if they don't look then they the player get to make decisions about that trajectory instead.

So choosing to look or not isn't supposed to matter, but it actually does matter in (the easiest form of) tabletop implementation of this idea.

Oh, definitely. Though as a GM, I'd pull the same thing an author would for the drama: Alice sees nothing but the drop into the lava, and possibly a burning puff of smoke which may or may not be Bob's corpse. I'd be re-inserting the obfuscating drama, but for a slightly different reason: I, the GM, don't yet know what has already happened there!

Jay R
2020-05-02, 11:33 AM
I won't do it.

1. I don't like the idea of separate timelines created by travel into the past. That's like saying you want to drain a swamp, and then leaving the swamp alone and moving to the desert. If going into the past only creates a new timeline, then you failed to change what you wanted to change.

2. I dislike the notion that PC actions cannot inherently change things. That makes the PCs' actions meaningless.

3. I don't ever want to say that an adventure that my players have had suddenly no longer exists.

I can be true to these ideas only by not having time travel.

Feel free to have your time travel stories. I am not saying other people shouldn't run them. These are the reasons why I will not run them.

LordCdrMilitant
2020-05-02, 04:25 PM
I won't do it.

1. I don't like the idea of separate timelines created by travel into the past. That's like saying you want to drain a swamp, and then leaving the swamp alone and moving to the desert. If going into the past only creates a new timeline, then you failed to change what you wanted to change.

2. I dislike the notion that PC actions cannot inherently change things. That makes the PCs' actions meaningless.

3. I don't ever want to say that an adventure that my players have had suddenly no longer exists.

I can be true to these ideas only by not having time travel.

Feel free to have your time travel stories. I am not saying other people shouldn't run them. These are the reasons why I will not run them.

I did mine as an information gathering exercise, which they used to learn where some people had taken an object they were looking for in the present time, so they could go and get it in the present.

The "time traveler" found themselves in control of one of the scene participants from the past scene, which they participated in and were able to manipulate enough to learn information they needed.

They didn't change things, but their actions weren't meaningless and contribute towards their planning.




It was also the product of the space drugs they took, so there's already questions about the mechanics of how it worked.

Lord Raziere
2020-05-02, 05:05 PM
1. I don't like the idea of separate timelines created by travel into the past. That's like saying you want to drain a swamp, and then leaving the swamp alone and moving to the desert. If going into the past only creates a new timeline, then you failed to change what you wanted to change.


as someone who likes time travel talking to someone who doesn't: this trope is less to do to with making actions meaningless with time travel, and more about making your actions make sense at all.

without alternate timelines you start running into paradoxes that will either screw up what your trying to change anyways, start running into unchangeable timelines that somehow resist you making any change at all without even the hope of a parallel timeline where things are good, or you can change the future but this just leads to other time travelers showing up and changing it to increasingly worse and worse scenarios as future conquerors and apocalypse bringers all try to arrive before each other until its a massive pileup of time travelers at the beginning of time screwing up everything.

with parallel universes, there is a modicum of sanity where you have a timeline that can be good without paradox or future plot pileup, even if its not the timeline you came from, and thus can be like an adopted home that you can defend and make sure is always good despite other timelines being bad. I'd rather have it over needing to do endless loops, or having to avoid paradoxes because logically even going to the past and exposing your future germs is probably going to cause a paradox by introducing stuff that doesn't exist yet, thus causing problems without any action of your own other than existing, or people somehow changing the future but this somehow does not affect other time travelers for some reason.

or you end up with Doctor Who, the time travel rules of which are literally "whatever the plot needs it to be at the moment".

jayem
2020-05-02, 06:50 PM
I won't do it.
I can be true to these ideas only by not having time travel.

Feel free to have your time travel stories. I am not saying other people shouldn't run them. These are the reasons why I will not run them.
In a distinction without a difference.

It could probably be done:
As Segev show's even in the more restrictive case you can just about let the players change things.
You can just about avoid the alternate universe means running away from the problem (to use your metaphor, your hometown might still be a swamp but you can still make a desert town from the swamp town)
Even in the over-riden adventure occurence, I don't think you have to make it totally non-existant, it's in their memory, it's in their muscles.
and even if not, you could do something you dislike, if it were worth it.

I do think time-travel makes it a lot lot harder (and the more you push at it by having loops the more so), and everything else you wrote follows just as well from that.
You have perfectly good reasons/aims, and they are (possibly) perfectly satisfied by not having time travel. And you aren't stopping anyone else.
If] for some reason you decided time-travel gave you something you valued playing as a one shot, then I think it would be worth reconsidering.

Crucius
2020-05-03, 09:14 AM
I once ran a two-shot in an existing campaign so the DM could play for a few sessions, featuring time stuff. Not time travel really, but time stuff for sure :P

The premise was that the party was to support a wizard who was planning to teleport into a dragon's lair to rob the place. This was all misdirection as the wizard was not particularly capable in spellcasting and was reciting his grocery list as part of the vocal component and the party was teleported to a barren wasteland. The wizard teleported into a rock and died. With the party stranded in this weird place they decided to explore, walking towards the only point of interest; a mountain in the distance.

On their way there they encountered three NPC's who were being attacked by some enemies commanded by a BBEG on a flying mount. One of the NPC's gets hurt, bad. When the enemies are defeated and the BBEG has flown away the three NPC's reveal that they have been here for a long time, but that they can't remember how they got here. All they know is that they are on their way to a temple that holds a way to escape this place, but before they can enter that place they must acquire a way to communicate telepathically. When asked why they cannot really remember why, just that they once decided that they needed it. They ask the party to get the communication method and then return here, as the three NPC's are unable to travel with one of them being critically injured.

After the party obtains the communication method (sending stones, telepathy, you name it) they return to the three. Meanwhile it feels as if the party never gets tired, even though the trek takes many hours. When the party arrive at the location where they last saw the three they see a familiar sight. The exact same events as before occur: three NPC's are attacked, one is critically injured leaving them unable to travel further and the BBEG flies away. Upon assisting again they don't remember the party at first. Then after a few moments it all comes back like some faint memory. Finally some progress for the three as they tell you where the temple is that holds the key to escape. They obviously cannot join.

The party goes to the temple which is in a state of decay. In a main hall there are two weird shimmering walls (one runs lengthwise, the other width-wise) that block access to the other side of the hall. In one of the walls are piles of bones on the floor. When the players interact with the wall it appears as if everything that enters the wall freezes in time. There is a console of sorts at the beginning of the hall, as well as one on the other side of the walls. When the console is activated the whole temple seems to revert in age (prince of persia warrior within, anyone?) and the bones reassemble into fully fleshed temple guards. The walls could then be operated by my character as a DMPC (receiving orders from the other players using the communication method acquired earlier), sectioning off the battlefield with movable walls. A guard captain would do the same for the enemy side. Once defeated the mcguffin could be grabbed and the temple would revert back to old age and start to collapse. Yadayada escape sequence, you get the idea, this message is already way to long.

Once outside the 'BBEG' is waiting for the party. He explains that the three NPCs are actually criminals of cosmic proportions. In their lifetimes they had achieved power befitting gods, therefore the gods imprisoned them here. Where is here? The Astral Plane (Woaaah, we're no longer on the prime material, mind=blown (that's not how it went, it was really underwhelming haha)). They put the three in a permanent loop; their own prison. Every day they'd think they had a chance to get out of this place, only to be prevented from progressing somehow. The 'BBEG', or The Warden is sort of sentenced to the same fate as it is his duty to keep them locked in here. Either way, the current stalemate has been broken so the party must choose who to side with, and wipe out the other party. Do they choose the warden for their sense of cosmic justice, or do they side with the three, believing that after aeons of mind erosion by reliving this loop they are no longer the criminals they once were, and that they should be absolved and approached as completely different persons.

The party then exited the realm only to arrive at the exact same time back in the campaign, thereby not having wasted a single minute (because time doesn't really pass in the Astral Plane). Really proud of that one, because it means that it can be inserted in any campaign without 'wasting' time in a more time-pressured scenario.

TL;DR:
Not really time travel, but time shenanigans for sure. Might be interesting nonetheless.

Time loop to lock up prisoners and erode their minds.
Time based walls that prevent ranged attacks/AoE from passing through, cannot be walked through, but can be walked in for damage immunity but leaving the player frozen in time, until some third party moves the wall off of that player.

NichG
2020-05-04, 08:41 AM
So, I couldn't help coding up a simulation of the jet-stream model of time travel: https://youtu.be/LboB_WznuII

This is a hard sphere simulation where a sphere that crosses the boundary on the x axis has its direction of travel in time reversed. Spheres moving in different directions from each-other don't collide. However, a sphere entering from one direction can end up sort of telefragging another sphere (even a lagged/leading copy of itself) that was already in that position in the other direction. This can create short-time self-interactions that lead to oscillations of a period of about 1 timestep between alternate time-lines, and those oscillations spread destructively throughout the system.

So in the end, even with this kind of jet-stream model, you can get basically total chaos moment-to-moment when looking at the timeline as a whole.

However, none of that chaos appears in the co-moving frame. So every observer inside this crazy universe will still see nice, smooth trajectories and other more or less sensible things, with 'causality violations' mostly taking the form of spontaneous events that had no apparent prior cause.

From an tabletop RPG perspective, if you're playing a campaign with the jet-stream model, you'd frequently encounter time travellers from wildly different futures/pasts, and there'd be almost no 'causal effects' of time-travel - no predestination paradoxes, no changing your past actions (trying to do that will just get you a totally random alternate world), etc. If you wanted to produce those kinds of stable loops, you'd somehow have to shield from the spreading high-frequency chaos that seems to happen with this kind of simulation. Note, having a smoothing interaction like you'd normally do in a physical system to provide an ultraviolet cutoff (diffusion, viscosity, etc) seems pretty hard to write down with this kind of model, since you'd also have to worry about interacting with your immediate future and past selves, and the universe would tend to be strictly dissipative rather than having energy conservation.