Time Travel Paradox

[Mr. 47]

I seemed to cause a bit on confusion with the Doctor Who stuff. I know the time travel is really implossable at times, but it jogged my thinking about the real-world mechanics of time travel.

I focused more on WWII then Hitler in my previous post, and while WWII might have been able to occur without Hitler, it would still have created a paradox. If Hitler was killed before he was a public figure, then he would be mostly, if not completely, unknown in the proposed future. Since there is no known man to kill, you wouldn't know to go back in time, to kill him.

I was putting another defenition to the grandfather paradox it seems, I thought it was the paradox when a man becomes his own grandfather (goes back in time, meets a woman, raises a family, the grandson is the man who goes back in time, cycle.) My mistake.

@ kouriichi: Yes, exactly my point. The event would and wouldn't have taken place, killing him would cause the travel back in time to not occur, and the time travel would cause the killing not to occur. Chicken and the Egg.

The Hitler stuff is just an example, I just picked a guy that everyone isn't too fond off (to say the least.) Say you went back in time to prevent the assassination of Abraham Lincoln, or JFK. They probably wouldn't change current events that much (or at least for those of us who aren't American) but since they were alive, you wouldn't have the concept in your mind to go back and save them, as you didn't know that they needed saving to begin with.

@randomsix: When Hitler is killed, the whole concept of Hitler would die with him, there would effectively be no Hitler in recorded history. Since there is no concept of Hitler, there is no knowledge of a man to kill, so you couldn't tell a man to go do the act, as you did not know that there is a Hitler to be killed.

As I said, I was ignoring the theorys of alternative timelines and fixed points in time, as they are not known mechanics of time travel. Both make the proposed event un paradoxical.

 

[JoshGod]

snip

I thought of something similar when I was young, I picked the scenario what if you went back in time and killed yourself, you would be dead and unable to go back in time to kill yourself, this led me to the conclusion time travel is impossible. Then again I don't think travelling between parallel universes has been disproven. Also this may be of interest if you have not seen it already http://www.escapistmagazine.com/news/view/109047-Physicist-Definitively-Rules-Time-Travel-Impossible.

 

[Beryl77]

Time travel is too complex for human minds to fully grasp it...yet. At least traveling to the past, maybe the only answer to those paradoxes(is that the plural?) is that time travel to the past is simply impossible.
Of course people have come up with other possible explanations. A very popular one is that when you go back to the past, you also travel to another dimension, so whatever you change there, it has no bearing on your your time and dimension.
Another one would be that you simply can't change anything when you go back in time because that's just how it has happened, if you had changed something, it would have happened differently. That means that if you try to kill Hitler, you just won't succeed because it didn't happen. There is an episode in Futurama where they go back in time and Fry meets his grandfather and Fry tries to protect him but because of him, his grandfather dies but that guy wasn't actually his grandfather he slept with his grandmother and became his own grandfather, weird I know but it's a possibility.
Others say that we can only go back in time to the point where we build the time traveling machine for the first time. It's impossible to go further back. It's like trying to send an E-mail to someone who doesn't have a computer, you need a receiving end. So, we can control very well who goes back and where that person goes to.
Or this [http://www.abyssandapex.com/200710-wikihistory.html].

 

[minus_273c]

You just create another time-line starting at the point that you changed the 'established' chain of events.

See 'Primer'. And then go "Wibble".

 

[Gather]

Or, you could steal Farscape's idea of time travel: The universe isn't as unstable as you think it is when it comes to time travel. Generally it'll try to "realign" itself with how it was supposed to end so that everything else isn't that horribly destroyed.

So yes, saving the entire planet could involve killing innocents, John Crichton.

 

[Valkyrie101]

The OP's point is a very goo one, and the reason why I don't like time travel, at least backwards time travel, to be featured in media. It really doesn't work without leaving a horrible paradoxical mess.

As for each and every variable causing the formation of a new alternate universe for every outcome: just think about how many variables there already are. Not much point in going back to kill Hitler if there are already a thousand different timelines in which he died in the First World War.

 

[Togs]

My laymans knowledge of physics tells me you'd change the future but you wouldnt change- something about you moving through the 5th dimension (aka choice).
But thats probably 100% wrong.

 

[Techno Squidgy]

To avoid Paradoxes most sci-fi goes along the alternate reality/timeline path when using timetravel.

 

[not_you]

I'm sure that if you're sent back in time (and sticking with example) to prevent WW2 then no matter how you get there, you'd end up doing what you were set out do to...

So what if Hitler wasn't a genocidal leader when you arrived... It's a matter of, you know what is going to happen in the future so you stop what you can regardless of what has happened up until that point...

I guess back on topic to the thing about the paradox, well... Of course it will.. If you change something in the past then the future is obviously going to be different...

It's like the chaotic theory of life.... (Chaotic theory being that if every atomic particle is moving and colliding then we can predict what is going to happen with each collision if we know enough about a certain moment)

If you change one thing about the past, the entire future will be re-written because certain particles and atoms aren't there to be collided with....
If that makes sense to you all....

 

[Magicmad5511]

I have a good theory on time travel. If you go back in time you are then a part of your own past. This would mean that you have already done the action in the past in your own present timeline. So with your Hitler example this would mean that if you go back you could not succeed for some reason or another because in your present Hitler had survived. So this means a paradox is impossible because you are already a part of the past.

The thing I hate is that time travel shows keep acting a if time is a river and if you interupt it it will change course. I see time more like a book, if you scribble on it, it doesn't change the writting it just adds more. Also doctor who just makes up rules as it goes.

I can unravel the mysteries of the universe but I still can't work out how to make my own thread.

 

[Zenn3k]

Why do people always reference killing Hilter in relation to time travel? I can think of some 'worse' people, Stalin, Khan... Michael Bay. In all seriousness, humans cannot bear our minds around time travel, its just how we process things. Because whenever I start up a talk, it always ends up turning into a subject about singularities.
Yeah we know how to do time travel, exceed or match light speed. But the conseqences to killing Michael Bay or whatever are out of our reach.

While killing Michael Bay would benefit everyone...actually the killing of Stalin would have likely causes Hitler to win the 2nd World War.

He would have easily invaded and conquered Russia, and not being attacked from both sides, would have probably made landfall in the United States sometime around 1949.

 

[satanslawer123]

how about this if you built your time machine for a completly diffrent reason say to go witness say a family mebers life when they were alive and you killed kitler by accident say running him over without knowing it was him, a paradox would have never been created and the reason to go back in time would still stand. theres probley some flaws to this pick them out if you please.

 

[The_root_of_all_evil]

Say if you do back in time to kill Hitler before the Second World War,

Hmmmm...Let's wait and see, shall we? [http://www.imdb.com/title/tt1795142/]

Oh, and by the way: Ezekiel Wigglesworth. [spoilers]

 

[Dchao]

You can't change anything important when it comes to time travel, I should know. I'm from the year 3012.

 

[Zenn3k]

While killing Michael Bay would benefit everyone...actually the killing of Stalin would have likely causes Hitler to win the 2nd World War.

He would have easily invaded and conquered Russia, and not being attacked from both sides, would have probably made landfall in the United States sometime around 1949.

*facepalm* Do you seriously think it was Stalin personally who stopped the nazis from conquering the Sovjet Union? Really? You don't think for a second it had anything to do with the russian climate, the sheer size of the country and its enormous industrial capacity? You think the one and only thing stopping them was Stalin's testicles?

Hell, they would have been far more succesful without that loony, seeing as how he basically exterminated all of the talented leadership in the whole Red Army, and he blindly refused to defend the country against the nazis until after they had already invaded.

Did someone abolish history in schools while I wasn't looking?

Without Stalin, its likely the Bolsheviks would not have gained power within the Soviet Government. This would have made the country vastly weaker militarily. It was under Stalin the country became an industrial powerhouse...without him there, they would have never done that, hence, likely been run over by the Nazi army.

Sure, the weather played a role in the Nazi's failed Invasion, but once the Soviets were able to muster their military, they were unstoppable.

Without Stalin in power, its likely the Nazi would have rolled into Moscow nearly unchallenged.

Learn some history yourself before you say such stupid things.

 

[dontlooknow]

The rules of quantum mechanics state (in part and very loosely put) that information cannot be destroyed - it can be moved around in the three spacial dimensions, but all information must remain a constant. Now, I'm going to give an example that may not seem entirely linkd to this paradox, but bare with me, we'll get there:

Stephen Hawking shows that black holes are not entirely black - they produce tiny quantities of radiation (aptly called Hawking Radiation), this means that if you could wait around long enough, the back hole would simply 'evaporate' away, creating a paradox - where does the singularity, and all of the information that fell in there, go? Not all the information can have been evaporated because general relativity tells us that nothing can go faster than light. But as I said earlier, quantum mechanics says that you can't just 'loose' information - this is called the Hawking paradox.

But recently, some clever fellows have come up with the idea of 'Phase Space' which unites the theories of quantum mechanics and relativity with the help of four additional dimensions that account for 1 energy and 3 momentum. So with the fuzzy rules of quantum mechanics applied on the macro level, we can show that if you dropped, say, Hitler in the black hole, then waited around for it to evaporated, as you looked back in time, the past would be so distorted and unquantifiable thanks to Heisenberg's uncertainty principle, that you could never be certain that he went in there in the first place!

More about that sort of thing is explained in this (very interesting) article:
http://www.newscientist.com/article/mg21128241.700-beyond-spacetime-welcome-to-phase-space.html but for now, lets get back to your time paradox. If you were somehow be able to got back and kill who ever it is you wanted to kill, when you arrived 'home' (in the time you'd set off from) you would have travelled such a distance that the effects of your actions would be unmeasurable - so you wouldn't know it was you who killed Hitler because the information that replaces the information erased from human history would have to be balanced by you being unaware of it in the first place. I think that makes sense?

Of course we know that travelling back in time probably isn't possible - we haven't had any visitors from the future, that we know of...