Time Traveling Question

Mental Time Travel normally dodges paradoxes because it only involves jumps backwards. No need to work out the effects of the changing the past since you can only get back to the future at 1 second per second anyway. Also you don't have extra (older versions of) people running around.

From the past-outsider's perspective there's no difference between a future self travelling back in time, and the present (past) self merely having a very detailed Prophetic Dream. There's still paradoxes of knowledge-from-nowhere.

Not to say there can't be paradoxes. If characters B and C travel back from futures that diverged to a shared past A, they can disagree about whether the other is a paradox or not. Or if someone travels back in time and prevents the creation of whatever allowed their time travel that can be viewed as a paradox. However from the past-outsider's perspective it just means the "traveller's" dream/vision isn't accurate anymore (if it ever was).

You must agree, my plan is sheer elegance in its simplicity! My Tumblr

If I'm understanding you right you're saying that Mental Time Travel is just like a prophet seeing the future but more advanced in ways.

Place your past in a book burn the pages let them cook.

Mental Time Travel doesn't seem like a good fit for this particular case either, because (putting aside the problems inherent to that concept) you still have the logical problem of existing in spite of there being no line of descent from which you could come into existence.

Level 3 Social Justice Necromancer. Chaotic Good.

I'm getting rid of the character killing their grandfather and instead the character stops a warlord from coming into power.

Place your past in a book burn the pages let them cook.

Now that's a lot easier. You can do that with a handwave (which you already said you didn't want to do) or come up with an explanation that doesn't make you want to harakiri yourself or something. Funnily enough, I'm also greatly concerned with logic, but I've learned that sometimes hard(er) science must take a backseat to the fantasy tale I'm trying to craft. In your case, hard(er) science may need to take a backseat to the sci-fi tale you're crafting.

Level 3 Social Justice Necromancer. Chaotic Good.

Well, if you are removed from causality, then as an acasual.. thing.. you are your own cause- effectively, a thing that exists because it exists. A weird causal tautology.

Which means you can totally kill your granddad. You can kill everyone, since your existence is predicated upon your existence. None of them need to exist for you to exist.

Of course, this just makes you an ontological paradox of sorts, since you are a thing that exists without having an origin.

I don't see how leaving the universe removes you from causality, but I, as a reader, would buy someone saying that time travel does. I mean, a time traveler can exist before they became and exist after they've ceased.

@Neko

I'm not entirely opposed to handwaves but I guess my question would be is non-paradox creating time traveling any more handwavy than a God or angels bring someone back to life?

Place your past in a book burn the pages let them cook.

If you handle it correctly, not really, it isn't ... well, any more than the whole "time travel" thing is itself.

If you have a setting that allows time travel, then you have a setting that is, presumably, in some way safeguarded against paradoxes from time travel, be that way something as simple as not being able to affect the past at all, or as complicated as having a time-line that splits into another one every time someone affects the past, or anything in-between those.

In fact, the whole "safeguarding against paradoxes" is why the difference between what is and what we think is, is so important: it is possible that the situation at hand only appears to be a paradox to the one trying to invoke it because the person does not have accurate information about the whole situation and made a wrong assumption (or assumptions). For example, we could have someone travelling to the past in order to kill their own grandfather before their father was born, but unaware that the person they are trying to kill was not their father's biological father (but merely pretending to be one, so that the child would have a father when the biological father was not there or wasn't someone to rely on); of course that still does make it possible that the future would change greatly enough that the one travelling through time would not be born or would not be able to do the jump through time because of it, but that's just a basic example and if you know how much not having certain information can change it is possible to play with that to the degree where paradoxes aren't an issue.

IIRC, in RL even the loophole that allows travel backward in time requires that the traveler also travel far enough in space that they couldnt possibly affect anything they did originally. For example, if you go back in time a year, you also have to travel at least one light year away. I could be remembering that wrong.

I always wanted to write a story where the protag goes back in time to stop something from happening (say Kennedy getting assasinated), succeeds, returns to his original point of origin, and no longer remembers the original history. "I failed, Kennedy still doesnt get re-elected!"

"We learn from history that we do not learn from history."

Is causality a law of nature?

Place your past in a book burn the pages let them cook.

What occurs naturally without a cause?

We could simplify it to ensure the paradox, and have them go back in time to kill their grandmother instead. Paradox is ensured, unless that causes alternate realities to split off.

That’s the epitome of privilege right there, not considering armed nazis a threat to your life. - Silasw

Point still remains, though, that it's possible to plan to do something based on the information we have, and do what appears to be this thing but in reality isn't because the information was flawed or not complete or whatever else.

Heck, even if you kill who you perceive as mother of someone, before that person is born, there is no guarantee that the person you'd killed is actually the person you'd thought it was (I'll just mention the rare but existent phenomenon where the grandparents adopt their grandchild because the kid's mother is a teenager herself). That is, if you look at it in general; in some individual cases you might approach certainty, and once again the very fact that you've done something in the past can result in a ripple that can write you out of existence or change you so greatly that you'd be virtually unrecognisable to yourself, unless—once again—your information is so faulty to begin with that you either are doing something that had always already been done at that time or otherwise not doing what you'd thought you were doing and that made all the difference.

But yeah, point taken, there might be people who are simply into it to cause a paradox and see what would happen. This means that the probability of a paradox happening if it is possible for one to happen is always 1 (will happen), so there has to be something to stop that from taking place, whatever that something is.

If someone exist outside of time would they be immune to causality?

Place your past in a book burn the pages let them cook.

I think you just need to be consistent. As an earlier post pointed out:

edited 22nd Jun '15 7:46:00 PM by editerguy

If someone exists outside of time, how can they do things, though?

Time is a measure of change after all. If you don't have time, then how can something become something else? You can't have been someone or will be someone because that would require time for a change to happen.

So I guess they'd be outside of causality by virtue of being unaffected and unable to affect anything, really.

That would mean attempting such a feat causes you to banish yourself from reality. You'd be trapped in some timeless existence for eternity, still unable to do whatever it is you were trying to do in the first place.

Level 3 Social Justice Necromancer. Chaotic Good.

I decided to go with the scenario where time traveling causes the person time travel into another universe. Instead of time traveling into their universe so the characters can only change the history of another universe and not their native universe.

So I wonder if this situation would cause Paradoxes or not?

A person from Universe 1 goes to the past of Universe 2 to prevent a disaster that occurred in Universe 2 past. But convinces himself from Universe 2 to go to the past of Universe 1 to prevent a disaster that occurred in Universe 1 past and to tell his younger self to go back to the past of Universe 2 to continue the Stable Time Loop forever.

Place your past in a book burn the pages let them cook.

If you are this worried about time paradoxes occurring, then just stop at "another universe" instead and get something that causes no paradoxes, of adding more stuff to it that makes it possible to get paradoxes again. So someone from universe 1 can go back in time to universe 2, someone from universe 2 can only go back in time to universe 3, and so on, and so on, and universe 1 doesn't get any time travellers.

Because really, as it is you are only making it more difficult for yourself.

Yes, this makes sense.

@Kazeto

The reason why I created the multiversal time loop situation is because I want the main character to have the opportunity to change his main timeline without paradoxes or handwaves. So I was curious if the situation that I wrote about made sense or was mind screwy?

Anyways thanks for the advice and I don't mean to be difficult on purpose I'm just a bit of a perfectionist when it comes to my stories.

edited 11th Jul '15 10:17:13 AM by warrior93

Place your past in a book burn the pages let them cook.

Eh, I am not saying that you are difficult. What I am saying is that you are making it more difficult for yourself.

We just answer, you are the one who can't write his own work because of it.

Because really, time travel is, at its core, already something that turns physics as we know it into an Escher painting. So all you need is to choose one reason, be it a hand-wave or something more in-depth, that causes it not to cause paradoxes, and keep it there. If you decide to make it that whatever makes time travel possible in this world of yours automatically stops time paradoxes via whatever you choose for it to do, then that's that and it works.

And I've seen enough ways to approach it. Multiple universes? Sure, seen that. Multiple time-lines, a new one created every time a change is made and them never merging? Yup, seen that too. Time-travellers being physically unable to do something that would result in a time paradox? Yeah, nothing new. Time-travellers turning into particle dust and disappearing as soon as they change something in a way that would have made their existence a paradox? Likewise. Universe adjusting in weird ways to rid itself or the paradox? Sure, been there, seen that. And so on, and so on. Heck, even the synchronisation system as seen in the Assassin's Creed series of games would have worked (the closer you are to a time paradox, the less able you are to act and screw it further), even if that was not about time travel.

So really, instead of reaching for something weird like that, simply incorporate something that would work into it and that's it. It doesn't have to get complicated for as long as it's believable, and if a hand-wave is worked into it in a way that is believable then there's nothing wrong with using it.

Ok, so the situation that I listed above about the multiversal stable time loop be believable for you?

Place your past in a book burn the pages let them cook.

That's ... well, I can say "possibly". Because there's nothing to protect the world from a paradox resulting from the time travel, but the choices of the person moving through time and their other self doing the same, so with this particular choice of explanation it all depends on how you write it.

edited 11th Jul '15 4:09:08 PM by Kazeto

I should feel it necessary to mention that one way to avoid all of this is to use the many-worlds hypothesis. The way time travel is handled in most works of fiction is never logically consistent, but this allows this causality to be preserved without breaking things.

Essentially, if you treat traveling back in time as creating an alternate reality upon point of entry then you can dodge the grandfather paradox altogether. For example, if I was to go back in time and shoot my grandfather, then instead of a temporal paradox causing me to disappear or some other circumstance instead all that will happen is that for this NEW world line I will never be born because the conditions for doing so will have been violated, but the incarnation of myself that shot my grandfather will continue to exist.

The problem with this is that traveling forward in time to your original timeline becomes impossible unless you create a workaround for it. Case in point, if I were to give my 5-year-old self $50,000 to invest in Amazon in the hopes that when I return to my own time I will be a millionaire, that will be impossible because my time travel will have resulted in an altered history where I became a millionaire and as a result there will be two of "me". You can't go back to your own world line as a result.

Anyway, that's a bunch of technobabble from me, but depending on your plot you may have use for this.

Splink!