I can’t suspend my disbelief long enough to watch movies that involve any kind of time travel because of their absurd errors. However, yesterday I watched the film Frequency where, through some phenomena, a son finds himself capable of talking to his dead father 30 years in the past over an AM radio.
There are many fallacies it’s a movie so who cares. But it did leave a gaping question that none of my friends could agree upon.
If it were possible for person X to change the past at time T, and in doing so, they change the future to the point that at time T person X does not change the past, what would happen?
In other words (using the movie as an example), say that the son in 1999 found an old AM radio in the closet and spoke to his father in 1969. The conversations they had changed the course of history. By changing the course of events in the past, say that the father in the past accidentally dropped the AM radio out the window and therefore the son in 1999 was never able to find the radio in his closet, talk to the past, and change the course of events that led to the radio not being there. What would the result be?
I think you mean a temporal parodox. Quantum physics has to do with atoms and their component parts.
Anyway, I’ll try to answer your question. Plese note that I’m not a physicist or anything and that my oppinion is based on a combination of:
a laymans understanding of the works of Einstein and Steven Hawkings
what I remember from physics class
things I’ve seen in episodes of shows like The X-Files, 7 Days, Sliders or the Star Trek franchises
movies like Terminator 1/2, Time Cop, 12 Monkeys, The Philadelphia Experiment and Back to the Future
Well here it goes. I have a couple of theories:
There is only one timeline. If that is the case then it would be imposible to alter history because everything that has happened has already happened. So theoretically, if you went back to prevent the Kennedy assasination, something would prevent you from saving him. You would get stuck in traffic, trip in the street, or some other minor twist of fate that would keep you from actually altering events. Parodoxes would not be possible because you are already part of the history we remember, albeit an insignigicant part.
There is more than one timeline. This is the so-called multiple parallel universes theory. Basically the idea is that there are multiple (perhaps infinite) variations of universes. Kind of like there’s one universe where Kennedy survives, another where Germany won WW2, another where the stapler on my desk is red, not black, another where the Giants didn’t SUCK in the superbowl last night.
So in this case you could have one timeline where the radio worked and another where it was busted. This theory is a little harder to accept becasue we can’t prove it with our conventional physics.
Einstein proved we can go forward in time. It’s not clear if we can go backward. I would hypothesize that we can’t since we haven’t met any time travelers from the future.
Of course nobody met a man who flew before until the Wright brothers built their airplane.
msmith has some interesting quantum insight into it, but I’d like to add some more.
I’ve never seen a theory that one could arbitrarily go backward in time, ut Kip Thorne et al have come up with a way to do it once you invent a new kind of matter with negative mass-energy.
As far as the Quantum stuff goes, it really depends on how one metaphysically interprets it. I like the Everette interpretation (msmith’s multiple time-lines). But, another way to look at it is through an sort of solipsistic world-line for the time traveller.
That is, the traveller does change time, but it involves no paradox. His “time line” might loop back onto itself, and then just continue. If one were to ask, for example, how the traveller managed to kill his grandmother and yet didn’t wipe himself out of existence he would simply say,
“I was born. I lived for some time, invented a time machine, went back in time and killed my grandmother. Neither could I have been born without her, but she could not have been murdered without me.”
Just doesn’t seem to paradoxical to me.
I recently read an article in Scientific American talking about using quantum physics to make time travel possible. It was done by forming a sort of quantum bubble around the time travelling object. The catch was that, while the object could go forward in time, it could never go back in time past when the bubble was first created. Basically meaning that if I created the quantum bubble right now, I could travel a few years in the future, but never further into the past than the present. I hope I got this right…if someone who had read the same article or has some knowledge of quantum physics could confirm/correct it would be appreciated.
WRT to the “kill your Grandma” thing: seems that the same way the traveler didn’t belong in 1962 (or whatever year he went to) he’ll return to existence he doesn’t belong in, but still exists (basically outside of time.) I don’t think that time is a conscious organism that can erase you or force you to trip, thus preventing an assassination. However, if you killed you grandma (preventing your own birth, a -3 trimaster abortion I guess), upon returning to 2001, there would be no other “you” to see. So you couldn’t meet yourself and give advice or anything, as happens in movies.
Just when the paradoxes start getting totally mind-boggling and seemingly impossible to resolve, Captain Kirk and his crew would find a way to undo all the damage and make everything just the same as it was before. Then they’d have a wry chuckle about it on the bridge.
If you will allow a minor hijack: question for sci-fi aficionados. Someone mentioned that time travel to the past seems impossible because we don’t have people from our future coming back to visit us. But it seems to me if someone did come back to us from the future, it might be very hard for him to prove that’s what he has done. Has anyone ever written a story along these lines - about someone trying to say ‘No, really, I come from your future’ and finding its a tough to one to prove in the face of scepticism \ indifference?
A way to think of it is this… you have your timeline. Things travel along this timeline. You find yourself able to “double-back” on the timeline. You kill your grandmother (you fiend!), which causes your future selves from that moment to cease to exist instantly. However, YOU still exist, traveling along the timeline at the exact moment of the erasure of yourself.
If you wanted to describe it in a nifty sci-fi quasi-intellectual way, you could say that to obliterate the anachronistic-you, the event would have to travel back in time, as well, to catch you when you kill your grandmother. However, it couldn’t, so you continue existing, albeit with huge pangs of guilt.
Yeah, it was called 12 Monkeys, and damn, was that a weird-ass movie (though not in a bad way).
Hmm, I would say that only the time traveller “exists” in this sense. The universe is created “for” or “by” him in that regard(why I mentioned the spolipsism). The time traveller cannot actually move backward in time (for example, when he travels backward he doesn’t get younger). So as far as he’s concerned he’s merely performing a series of actions involving people that seem to be the same throughout his life. That is, except for our traveller, time is actually infinitely discontinuous. It might even be for our traveller, too, but I don’t want to think about that (quantum physics might imply this anyway, what with its smallest unit of time, about 1 X 10E-42 second).
Otherwise we would have to change the conservation of energy law to include time(which it might anyway, I don’t know for sure). Because if we didn’t then the moment the traveller went back in time he took his mass/evergy with him, violating all sorts of laws. Unless he was somehow replaced by the exact same quantity of mass/energy from the past, of course (which I had a crazy dream about, remind me to mention that some time).
I don’t know of any time travel literature off the top of my head. It’s a pretty familiar theme in movies though. In movies like 12 Monkeys or Terminator, people usually believe the time traveler is insane or dilusional. Wouldn’t you?
I imagine it shouldn’t be too hard to prove. If you went back in time to oh, say 1985. You should be able to predict major events before they happen with pretty good
accuracy.
Is paradoxial because if you kill your grandmother before you’re born, you can’t exist. From grandmas frame of reference, she lives for a number of years and then dies childless.
From your frame of reference, your grandmother had your mom or dad, who had you. You built a time machine, went back, and killed grandma before all this happened.
It’s a parodox because the two situations contradict each other. Grandma couldn’t have been killed by you if you never were born. Kind of like this computer can’t be both on and off at the same time.
It’s still possible that you could go back but something would stop you. Try to find out if grandma ever killed an intruder when she was younger. The problem with this concept is that it implies that every moment in time is already pre-ordained.
If it were paradoxical then for you to travel back in time you would also have to age in reverse as it happened. You then couldn’t kill your grandmother because you would stop existing at some point.
The interesting notion that was brought up by neurotik was that Kip Thorne time machine. We create it at time A. It exists, then, in all times after A. Then anyone may travel back in time to A from B, C, or D. This also leads to some terrible paradoxes, the likes of which would take some serious explaining to do.
So long as no instant of time exists dependantly on any other existence of time then there can be no paradoes. So long as only the time traveller really exists then there can be no paradoxes. So long as timme travel is only possible by skipping around multiuniverse times (but never back to your own, except at the time you left) there are no paradoxes.
Only when time is uniform, continuous, and applicable to all objects in reality in the same way is time travel paradoxical.
The Kip Thorne book is a great read on relativity, though for the life of me I can’t remember its name.
Thinking about this problem, I came up with another.
If I invented a time machine and went back 5 min, grabed myself and jumped back into the maching and went back another 5 min, and repeated this several times. Could I create several versions of me. Now the problem is, if I know what I am thinking but do not know what the other “me’s” are thinking. Are they really me.
I was thinking along the same lines myself, but the more I thought about it, the less straightforward I imagined it might be.
For this discussion at least, let’s make some working assumptions. (1) When you go back to 1985, you retain your present mind and knowledge. (2) It’s the same 1985 you lived through, and the same things happen.
First of all, how many major events of any importance can you remember from 1985? Some people with specific interests might recall some significant info - sports fans might remember a few significant sports facts, business geeks might know some important movements on the stock exchange, movie buffs might know which film’s going to take the Oscars by storm. And so on.
But for a lot of people, you might find yourself a bit light on ammo when it came to making enough predictions which are sufficiently impressive to help you prove your case.
In any case, who would you take your case to? How would you get them to listen to you? And how would you prove a difference between “I can make several lucky predictions” and “I am from the future”?
It gets even harder if you go back in time, but to a different place \ country \ culture.
I think the more you get into it, the more potential problems arise. I feel there are some interesting stories to be spun from this cloth.
You have a more serious problem here than deciding whether or not they are you.
If you went back 5 mins, grabbed yourself 5 mins ago, then went back another 5 mins and repeated, you would have been grabbed and taken away 5 mins ago, so would be unable to go back in time and grab yourself ?
Now i’v clarified that
In a sence they would be you, they would have exactly the same experiances as you, exept for the last 5 mins, so would react to situations in an almost identical way to you, and would think of situations in a simaler way to you, but that last 5 mins of your life would have some effect, probably cause you to be thinking different things than the other “you’s” (for example the “you” from 5 mins ago would be wondering what the hell was happening, you would just be wondering why you don’t remember somone looking exactly like you abducting you 5 mins ago).
Hope that confuses you as much as it confused me
You can not change the past because it alrady happened, but you can create and additional future. And, you can not travel ahead in time unless you are in the past.
This is where it gets intresting. There is one orignal time line. If you travel back in time to 1985. You would jump into 1985 and at that moment a time line fork is created. So, now there is the orignal time line with a future and the new one that was just created. Yes, the past is the same for both time lines. But the future is not because the future for the fork you created has not happened.
This is why you can not travel into the future unless you are in the past. But, you can not travel in the future of the current fork you are in because the future has not occured yet.
You can however go into the future of the orignal time line or any other fork that is created that is further along than you are. But, if you travel into the future, you will create another time line fork unless it is the fathest point in any given time line fork or orignal time line.
Back to the example, you go back to 1985, new future fork created, you fix things and travel back to the future (orignal time line) and every thing is the same as before. Be sure to jump back to the current orignal time, not the same time you left. This way, you will not create another time line fork.
I agree that you would not be able to change what has happened, because it already happened that way. You, running around trying to save kennedy, would be a part of the history that already took place.
On a ligher note, since we’re talking about time travel:
Dude, after our history report, we have to be sure not to forget to come back and do all this stuff, or else it won’t happen!
But it did happen!
Excellent!
[air guitar]
One cannot change the past, only fulfill it. Reading a book by the name of Hyperspace right now by some asian. Any interested parties should inquire within, all time travel paradoxes are tossed aside like a rag doll.
Also: A Connecticut Yankee in King Arthur’s Court.
Traveling back in time may be possible given the quantum theory of a multiverse, but you wouldn’t necessarily wind up in your past, and killing your grandmother, well, she’s another quantum reality’s grandmother, not yours.
In Crichton’s Timeline, he addresses this very issue/concept as a central theme, but dismisses the idea of a paradox by stating that you cannot kill your father before you were born. How would you do it? Shoot him? You’d have to get a gun, find an appropriate place and time, but you could get stopped, or miss, or only wound him. He says that’s it’s a romantic idea, but you as an individual cannot have a very big effect on history like that.
I think it’s a cop out. If you went back in time and prevented JFK’s assassination by jumping Oswald before he got a chance to fire, then you would affect that quantum reality’s timeline, not your own. If you came back, you would return to this timeline, where JFK was killed.
