Time Travel Paradox

[Mr. 47]

I was thinking the other day after watching the new Torchwood (and wondering when the new Doctor Who will come out) about time travel, when I thought of something: If you go back in time for the purpose of changing an event, that would create a paradox.
Say if you do back in time to kill Hitler before the Second World War, and you succeed, WWII is averted, many lives are saved, doesn't this create a paradox? In the future of that time, Hitler died before he did anything historically significant, and since he would have no historical importance, you would have had no reason to kill him, or likely even know of him, so you wouldn't go back in time, and he wouldn't be assassinated.
If you go forward in time, for any reason (unless someone came back in time, and told you to change a future event) this wouldn't happen, as it wouldn't change the present history.

I don't know if this is a particularly original thought, or if I am completely wrong. The scenario above just applies to out known rules of time, not parallel universes, or fixed points in time.

 

[Extravagance]

It always will create a paradox if you physically do anything or say anything. It's one of the most basic paradox's within the Philosophy & Logic field, and one people don't really tend to spend much time on because it's unsolvable without changing your idea of how time works. And that gets overly complicaed.

 

[Valagetti]

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.

 

[JoJo]

This isn't a particularly original idea, just a form of the infamous grandfather paradox:

http://en.wikipedia.org/wiki/Grandfather_paradox

 

[warprincenataku]

The Doctor explains this in two ways, first off, some events in time are time locked and cannot be changed, these are generally large events that would cause too many problems if they were undone, like the Dalek-Timelord war or possibly, WWII.

The second is that when you are traveling, the knowledge that you have and the events that you cause are now your existence. So for example, you would be aware of the changes, but everyone else wouldn't be in the future.


So in summary, Hitler probably couldn't be killed because WWII is time locked and even if you could kill him, you would still remember the atrocities committed, but everyone else wouldn't.

 

[HerbertTheHamster]

WWII wouldn't be averted by killing Hitler, the treaty of Versailles made sure of that.

stop thinking about time travel, it's impossible. Doctor who is probably the worst show in the world to watch if you want to learn about spacetime and such.

 

[Srdjan Tanaskovic]

I was thinking the other day after watching the new Torchwood (and wondering when the new Doctor Who will come out) about time travel, when I thought of something: If you go back in time for the purpose of changing an event, that would create a paradox.
Say if you do back in time to kill Hitler before the Second World War, and you succeed, WWII is averted, many lives are saved, doesn't this create a paradox? In the future of that time, Hitler died before he did anything historically significant, and since he would have no historical importance, you would have had no reason to kill him, or likely even know of him, so you wouldn't go back in time, and he wouldn't be assassinated.
If you go forward in time, for any reason (unless someone came back in time, and told you to change a future event) this wouldn't happen, as it wouldn't change the present history.

Sense you are from a time line where Hitler did do something then the changes you make in the past won't affect you

 

[Merkavar]

anything to do with timetravel is to complicated as ends in a paradox. except maybe traveling back in time as an observer.

 

[Grouchy Imp_v1legacy]

You mean the Grandfather Paradox?

EDIT -

This isn't a particularly original idea, just a form of the infamous grandfather paradox:

http://en.wikipedia.org/wiki/Grandfather_paradox

Ninja'd. Damn.

 

[Fgw_wolf]

What you change is another dimension. I suggest that even if you do kill hitler the timeline for your dimension will remain unchanged because in your world he was alive before you went back in time and by killing him you created an alternate universe. Thats one idea I haven't seen in this thread so enjoy.

 

[Jordi]

Yeah we know how to do time travel, exceed or match light speed.

Would you care to elaborate on this? As far as I know time travel is fundamentally impossible, we know of nothing that moves faster than light and we can not even come close to making other things than light move at the speed of light.

I was thinking the other day after watching the new Torchwood (and wondering when the new Doctor Who will come out) about time travel, when I thought of something: If you go back in time for the purpose of changing an event, that would create a paradox.
Say if you do back in time to kill Hitler before the Second World War, and you succeed, WWII is averted, many lives are saved, doesn't this create a paradox? In the future of that time, Hitler died before he did anything historically significant, and since he would have no historical importance, you would have had no reason to kill him, or likely even know of him, so you wouldn't go back in time, and he wouldn't be assassinated.
If you go forward in time, for any reason (unless someone came back in time, and told you to change a future event) this wouldn't happen, as it wouldn't change the present history.

Sense you are from a time line where Hitler did do something then the changes you make in the past won't affect you

If you return to your own time (that is now altered), it will affect you, because the people around you affect you. You may "know" that WW2 happened, but a lot of the changes that came about because of its prevention will also affect you. For instance, if WW2 is what prevented us from having light sabres, you could go to the past to kill Hitler, come back and have some sweet light sabre duels.

 

[Fgw_wolf]

We do actually have light speed weapons I saw an interesting program about it on the history channel yesterday, heres a link: http://www.dailytech.com/US+Air+Forces+Laser+Air+Armada+Nears+Combat+Readiness/article17676.htm

 

[Amgeo]

There's also the idea that killing Hitler wouldn't actually change all that much, just that a different dictator would take his place. If you read Terry Pratchett's "Mort," you have a vague idea of what I'm talking about; namely, that history isn't built around single people.

 

[randomsix]

As long as you rig it so that someone has a reason to go back in time to kill Hitler then no paradox is created.

 

[ReservoirAngel]

It's a paradox that's a big point in the 2002 "Time Machine" movie, where a mutated Jeremy Irons (more awesome than it sounds, trust me) puts it perfectly:

If you build a time machine to go back in time to change something, then that event you tried to avert never happened, thus you wouldn't need to build a time machine. It's a constant paradox that you can't break out of.

 

[kouriichi]

I think that the action of killing him, would probably nullify you having to go back in time.

But that doesnt bring him back to life because you didnt go back.
Let me make a chart.

Part 1:
You make a time machine-----> You go back in time----> you Killed Hitler-----> You go Poof. ((you as you are now would not exist))

Part 2:
No war was fought-----> happyness was get-----> You were born----> lived your life.

I believe the action would only have to happen once for it to change the time line, and after it happened, you couldnt change that action, unless you stopped yourself from killing Hitler, by killing yourself before you killed Hitler.

You would only exist for a moments leading up until Hitlers death. ((when you got there, to when he died)) So there wouldnt be a paradox, you would just Poof. Into thin air. After that moment, you would never exist. The "you" who would be born wouldnt exactly be "You". He might have the same name, maybe the same parents, maybe even the same friends! But he wouldnt be you, because you wouldnt exist in that future.

Its weird. Now my head hurts.

 

[Not-here-anymore]

Given that both Doctor Who and Torchwood will (at least briefly) be running together, I'm curious as to whether or not the miracle will be mentioned at any point.
Though they could just avoid the present day in Dr. Who until Torchwood ends...

 

[No-one Special]

Actually, the way you're thinking about time, you're thinking of it as one long continuous thing. I have a different perspective. All time exsists at all moments. 5 minutes ago, right now, and 5 minutes in the futures, all of them are happening right now. They just exist on different planes of exsistance.

So theoretically with that in mind, there are literally billions of planes existing right now with every possible history imaginable, we just can't see them and we don't exist on that plane.

Think of it like a movie real. Every second, past, present and future, is a single frame. Now imagine all of those frames stacked on top of each other, but then they're in a single frame as opposed to infinite frames on top of each other.
How do other time lines come into their example? Take a completely different film, do the same thing, then put both frames together.

Ever get the feeling of deja vu? That's because you've already existed on that plane, but you're not supposed to have known.

Have fun with that.

 

[ShindoL Shill]

heres what you do: go back to sarajevo on the 28th of june 1914 to sightsee (check out Schiller's Cafe). if you notice a man named Gavrilo Princip:

this guy...
buying a sandwich, shoot him in the face and rob the cafe.
two world wars averted, no paradox (you went to sightsee remember, plus he would have been found with a cyanide pill and a pistol, so he would still be reported on and thus historically significant.)

Actually, the way you're thinking about time, you're thinking of it as one long continuous thing.

exactly, its actually...

As long as you rig it so that someone has a reason to go back in time to kill Hitler then no paradox is created.

but the reason needs to be valid if you remove hitler. thats why i use tourism. would you go visit your cousin who lived near The Best Museum Ever and then go to the museum? yes. what if your cousin never existed? you're still going to the museum, so you still go.

 

[WolfThomas]

As time travel (at least backwards) is pretty much impossible I don't think it's a problem. Otherwise it depends on what sci-fi rules you're playing with. You might remain but everything you know is different. Otherwise you might just create another alt-universe parallel to your own. You might disappear. Who knows?