Something that bugs me about time travel.

[Sean Hollyman]

I'll try and explain it using a scenario.

So there you are, sitting on a bench and you're pretty hungry. Suddenly your future self from 2016 pops in and gives you a sandwich. Then he leaves.

So you live your life normally until 2016, and you realize this is the day that you're supposed to go back and give yourself the sandwich.


What would happen if you choose not to?

It's already happened in your past, but how can it happen if you don't go back and do it?

 

[LaoJim]

What would happen if you choose not to?

It's already happened in your past, but how can it happen if you don't go back and do it?

Ah the joys of time-travel science fiction. Possibly you would cease to exist, or slowly morph into the kind of person you would be today if you hadn't eaten a sandwich two years ago. (and what wonderful transformations that sandwich wrought on your life!). Perhaps you would discover that it was actually a clone or robot-simulation of yourself who went back in time. Perhaps, when just about to eat a sandwich you would end up tripping over a wire in a science laboratory into the time machine, banging your head hard enough to give you amnesia, and when you woke up you decided to give your sandwich to the stranger (not clearly viable due to your concussion) as you didn't feel like it anymore. Perhaps the paradox would be enough to wipe out this universe and a couple of other universes that happened to be in the vicinity. Perhaps Dr Who would turn up and have a nice friendly chat with you about your responsibilities to the space-time continuum.

I'd say the possibilities are endless, though really I think sci-fi has explored most of them over the years...

 

[Colour Scientist]

What kind of cold-hearted bastard wouldn't go back in time to give their past-self a sandwich?

If things were really messed up because you chose not to, you could always travel back in time so you could travel back in time to give yourself sandwich. Then, I suppose, if that version of you then chose not to travel back to 2016 in order to travel back to 2014 and give yourself a sandwich, the same dilemma occurs.

 

[Thaluikhain]

I'd say the possibilities are endless, though really I think sci-fi has explored most of them over the years...

More or less, yeah.

Though, most sci-fi does this really badly. They might have time travel as a gimmick, but they'll avoid dealing with it to any great degree.

Time travel has become a background thing that's sciency to throw into a show, everyone has seen it all before, so there's no point actually bothering to develop it. Despite it being a totally fictional concept (as far as we know), with whatever rules you can think up for it.

 

[lechat]

pretty sure this is already solved by a bunch of physicists smarter than most of us in here.

1. new universe is created and alternate you gives sandwich.

2. universe blinks out of existence.

3. no such thing as time travel that allows you to give ppl sandwiches.

i always forget how time travel (theoretically) works and just go with the flow.

 

[LaoJim]

EDIT: Opps part of this got messed up badly. Try and get it right this time...

1. new universe is created and alternate you gives sandwich.

2. universe blinks out of existence.

3. no such thing as time travel that allows you to give ppl sandwiches.

I always forget how time travel (theoretically) works and just go with the flow.

Yeah, time it seems is pretty complex stuff and if time travel is possible its rules are probably highly counter-intuitive.

I'm not convinced by 1. You know your universe already exists. Why would there be another identical universe with a you who wants to travel across dimensions to give you a sandwich? Did he receive his own sandwich from another you from yet a third dimension and now needs to pass the favour on? If you don't feel like giving yourself a sandwich, why would he?
It may be that at the moment you chose to go back to the past, a new universe with a new past is created and anything you do to alter the past doesn't affect your original universe.

My paragraph about explains why...

Though, most sci-fi does this really badly. They might have time travel as a gimmick, but they'll avoid dealing with it to any great degree.

It's very difficult to create a time-travel story that is completely watertight and also investigates the potential issue with time travel in a believable way.

The issue with 2 is when does it blink out of existence? In 2014 or 2016? It might be better to say that such a universe could never have existed in the first place (If we think that everything that happens in the universe is determined by its starting conditions). Imagine that we know you received a sandwich from your future self. Instead of simply deciding not to go back in time you decide to flip a coin to see if you will go back or not. Since we know you did, the result of that coin flip must come up heads. Suppose that now you decide to flip two coins and only go back if both of them are heads. Again they must both be heads. Add as many coins as you want the result should still be the same, however as you start to get to infinitely small possibilities the chances of it being a clone/robot/other strangeness I mentioned becomes more and more likely relatively to the possibility getting the right number of heads. I imagine writing a story where time travel becomes as cheap as flying abroad and everyone can do it. In this reality the chances of such an Earth existing without paradox quickly becomes much more unlikely than some devastating calamity wipes out the human population.

Number 3 is of course the most likely.

 

[Scarim Coral]

Depending on how sufficient that sandwich is, I assume your life will alter according on how it would of been played out when you don't hand the sandwich to your past self. Who knows, it could of been trivial at best (your past self just went to a sandvich shop) or it could of been major (like I dunno, without getting that sandwich, you had gotten run over by a car when you cross the road to go to the sandwich shop!). Yet again, it could be a butterfly effect if you don't hand your past self your sandwich or you had reacted an alter universe for not handing that sandwich?

Also how would you know it was the exact day you supposed to hand the sandich? The attire you are wearing or how the sandwich was presently made or maybe you were wearing a one of a kind clothing or you had emerge from a battle (so you look battle scar just as your future self did)?

 

[Keoul]

I believe in two theories for time travel.
1. Everything has already occurred, you will go back in time to deliver that sandwich no matter what since it has already happened, the thought of not delivering that sandwich won't even occur to you.

2. By being given that sandwich what has happened is that you have created an alternate universe where a future version of yourself has given you a sandwich, time has been altered and you may or may not go back in time in 2016 and give your past self a sandwich since the sandwich originated from an alternate universe.

 

[Aerosteam]

No matter how hard you try to change it, every single outcome will have you giving your past self a sandwich.

Think why your future self gave you a sandwich in the first place - it doesn't matter what it was, you ended up doing it.

There's no point in not doing that action, because you already did it in the first place.

 

[Jacco]

I'm not convinced by 1. You know your universe already exists. Why would there be another identical universe with a you who wants to travel across dimensions to give you a sandwich? Did he receive his own sandwich from another you from yet a third dimension and now needs to pass the favour on? If you don't feel like giving yourself a sandwich, why would he?
It may be that at the moment you chose to go back to the past, a new universe with a new past is created and anything you do to alter the past doesn't affect your original universe.

My paragraph about explains why...

Though, most sci-fi does this really badly. They might have time travel as a gimmick, but they'll avoid dealing with it to any great degree.

It's very difficult to create a time-travel story that is completely watertight and also investigates the potential issue with time travel in a believable way.

The issue with 2 is when does it blink out of existence? In 2014 or 2016? It might be better to say that such a universe could never have existed in the first place (If we think that everything that happens in the universe is determined by its starting conditions). Imagine that we know you received a sandwich from your future self. Instead of simply deciding not to go back in time you decide to flip a coin to see if you will go back or not. Since we know you did, the result of that coin flip must come up heads. Suppose that now you decide to flip two coins and only go back if both of them are heads. Again they must both be heads. Add as many coins as you want the result should still be the same, however as you start to get to infinitely small possibilities the chances of it being a clone/robot/other strangeness I mentioned becomes more and more likely relatively to the possibility getting the right number of heads. I imagine writing a story where time travel becomes as cheap as flying abroad and everyone can do it. In this reality the chances of such an Earth existing without paradox quickly becomes much more unlikely than some devastating calamity wipes out the human population.

Number 3 is of course the most likely.

It's not that the universes blink in and out of existence. They already exist with the predetermined set of events that lead to that specific outcome. According to my (limited) understanding of multiuniverse theory, there is a universe that exists for every possible outcome to every possible action. So if you live in the universe where you went to give yourself a sandwich, then you go to give yourself a sandwich. If you live in the universe where you don't, then you don't. Both possibilities exist simultaneously and both happen simultaneously.

If you want to get hairy, then to "time travel" you are going to a universe that exists at a point in the past of your current universe to give yourself the sandwich. So that universe is one where you got the sandwich and will likely be one where you travel to ANOTHER universe that exists at that point in time compared to the universe that existed in the past when the first universe existed in the present.

My brain hurts from just typing that.

 

[LaoJim]

It's not that the universes blink in and out of existence. They already exist with the predetermined set of events that lead to that specific outcome. According to my (limited) understanding of multiuniverse theory, there is a universe that exists for every possible outcome to every possible action. So if you live in the universe where you went to give yourself a sandwich, then you go to give yourself a sandwich. If you live in the universe where you don't, then you don't. Both possibilities exist simultaneously and both happen simultaneously.

If you want to get hairy, then to "time travel" you are going to a universe that exists at a point in the past of your current universe to give yourself the sandwich. So that universe is one where you got the sandwich and will likely be one where you travel to ANOTHER universe that exists at that point in time compared to the universe that existed in the past when the first universe existed in the present.

My brain hurts from just typing that.

Don't worry, without being rude, if I try to reply to your comment intelligently both our brains will probably explode. So I'll take this opportunity to bow out gracefully.

 

[Bad Jim]

I think it would simply be impossible to not give yourself the sandwich, or kill your parents before you were conceived, or anything like that. You might try, but either something would force you into giving yourself the sandwich, or maybe you were mistaken and the sandwich giver was an identical twin or maybe from 2017 and lied.

I general I'd say that if you were a contrary sort of person you wouldn't receive a sandwich from yourself.

 

[Delock]

The additional mass added by that sandwich in the past would not be removed by subtracting that mass from the universe in this new timeline. Thus you would contribute to the quickening of the over extension of the universe and hasten its death, you heartless bastard.

In all seriousness, what would the addition of mass created by a time displaced object do to the world? Would the air it appears in be forced away violently? I have seriously wondered this for awhile now.

 

[lechat]

gonna simplify this question for anyone that wants to try and wrap their head around this.

Imagine your computer could send a signal 10 seconds back in time to itself .
It sends the command "turn off"
enjoy!!!

 

[Jadak]

Personally, I start with believing the theory that it would be unavoidable. The reasons you go back in time to give yourself a sandwich will be the same as the reasons the first time travelling you did, thus you would make the same decision for the same reasons because everything would be identical. The future you decide to follow through rather than challenge it thus you will as well, otherwise it never would have happened in the first place.

But then I think, that's bullshit, you can do what you want. Thus, I tend to believe time travel is not possible, but short of that, I believe in branching timeline approach, meaning you can do what the fuck you want, it will not make a difference to your own past.

 

[Jadwick]

I don't worry about it, if time travel we're ever going to be invented, we would already know about it.

What you should really worry about is how deja vu is really your brain perceiving a timeloop and how to expand and use said ability.

 

[Imperioratorex Caprae]

What kind of cold-hearted bastard wouldn't go back in time to give their past-self a sandwich?

Me, because I'm kinda mean to myself sometimes. And lazy. Why the hell should I bother? I already ate the sandwich...

 

[Little Woodsman]

If you game-master FRPG's questions like this come up with alarming frequency.

So (having learned from experience) when I start a new campaign/adventure one of the things I decide from the start is what model of Time-Travel exists for the world/universe the game is set in. There are two models that I favor:

1-The Marvel Comics model. Established by lots of people asking Reed Richards how the heck time travel worked. Basically in this model any future that someone comes to you from is an 'alternate' future... because it hasn't been reached yet. From any point in time there are a gigantic number of possible outcomes, and therefore possible different universes. *Every* one of those possible universes exist. In a huge number of those 'alternate' futures you decided to go back and give yourself the sandwich.
Using this model one of your future selves made it back to your universe from their alternative one.

2-The You Are Being Watched Over model. One or more super-advanced/super-natural races is watching over you to prevent exactly this kind of mess up. (My preference for a watcher race is the Crusader Koalas From Beyond Time-- not my invention, they are from the old Ghostbusters RPG). These beings routinely intervene to prevent such paradoxes.
Using this model, one of the Crusader Koalas disguises itself as you and goes back in time to give you the sandwich.


It's really the same as the "How do you kill a vampire?" question. You are able to kill a vampire in whatever way the game-master/writer decides.

 

[madwarper]

As usual with time travel, this all depends on whether there are multiple universes or just the one.

If multiple universes, then you don't have to give yourself the sandwich, because there's a universe where you never got the sandwich.

Else, if there's just the one universe, then you giving yourself the sandwich is a forgone conclusion and any attempt to avoid that fate will only cause it to happen.

 

[OrokuSaki]

The answer is simple, if you don't go back in time to give yourself the sandwich, then you will have created a divergent timeline. There are now 2 known realities, the sandwich world, and the starving world. You exist in the sandwich world, having received the sandwich. But now there's an alternative in which you did not receive a sandwich, and that version of you lives to the year 2016 and goes back in time to deliver a sandwich to himself when he most desperately wanted it (It must have been such a time since he bothered to take note of it). And this third version of you grows up not knowing the pain of lacking a sandwich, and selfishly does not use a time machine to grant himself this boon. Which means that this third person and the you are the same.

BUT and this is a huge but: the second person, the one who had given you the sandwich, having initially created the divergent time line, travels forward to the year 2016 to find that, because he'd created a new reality, he is already there in the form of you, person #1. So both a beneficent and heartless version of yourself exist in the same place at the same time and now you need to figure out how to resolve the situation because there can be only one. Do you let person #2 live because he's the better person, or do you, person #1 continue to live out your own life because you're the one who rightly belongs in this timeline, it having progressed through your obtaining of the sandwich? Naturally you choose yourself, brutally murdering your kinder gentler side so that you can continue to live on.

Don't do time travel kids. Time travel always leads to duplicate murder.