okay i've been researching about time travel, paradoxes and alternate universes for more than a week now and it seems that there are so many theories out there but a few stood out for me. ie they weren't excessively confusing or labelled as impossible There's the whole notion that if you go back in time and change something(which is inevitable) a parallel universe will branch off from the original. It basically says that when something happens it either happens or it doesn't meaning the two universes split running parallel to eachother both with similar events and what not. but if thats the case then shouldnt there be like thousands upon thousands of parallel universes? The typical Grandfather paradox - where by someone goes back in time and kills his grandfather. If he does this he would never be born and therefore cannot commit the gruesome act. This one is pretty straight forward but none the less confusing for me. There was also a theory that a man can go back in time and be his own father which i don't quite understand????? The pre-destination paradox which was one of the main premises of the terminator movies where a master computer called SKY-NET sends a cyborg back in time to kill the mother of John Connor who will inevitably become the leader of the human resistance. The humans also send back their own person who ends up being John's father. in the second movie we see the development of the chip from the first cyborg, which will be the basis of the skynet technology. does anyone know of any logical theories to prevent the proverbial time paradox or explain the whole be your own father thing? EDIT: also, if a man wants to go back in time to stop his building from burning and finds he was the root cause does he see himself knock over a lamp or something or does he just go and remove the lamp. And also if he fails and tries again does he come back to find a horde of others staking out the place trying to set things right? i hope people understand my ramblings
This is probably what will happen. Also, there are more than likely an infinite number of unerverses, each with its own timeline.
Ooh, ooh. Read Pastwatch by Orson Scott Card. He bypasse the entire paradox issue by making time seperate from causality (cause and effect) He said that the reason we see the two as the same thing is because causality almost always runs parallel with time, but since they are two different things you can go back and kill your grandfather and it won't do a single thing to you because according to causaulity you have already been born, that is no longer a cause now, it is an effect. Spoiler In the book the world is coming to and end because it is running out of resources so a team of scientists tries to figure out where they can send someone back in time to a key point and change history. They determine that Colombus is the turning point. It turns out that Colombus has already had one visit from the future, and that is what set him on his course to sail to the new world. The people had done that in order to prevent a historical event where the native american empires had discovered how to sail and then invaded Europe. This group of scientists goes back to the time when colombus finds the new world and try to convince him that the native americans are equals and not inferior creatures. It works, in the end colombus sails back to europe with a fleet of native american ships and there is peace talks all around, thus preventing one of the bloodiest times in history and changing the future forever.
I like the theory of parallel universes and enjoyed watching Sliders. However I don't really believe that there would ever be parallel universes just because someone goes back in time to change something. For me the most plausible time travel events are those where time travelers don't change the past and/or happen to be part of it. Examples of the types of time travel stories I believe the most are like the show Final Countdown where a modern day aircraft carrier ends up back in time near Pearl Harbor before the Japanese bomb it. The captain plans to change Pearl Harbor but ultimately does not. Another example is in the first dragon riders of pern book where Lessa travels back in time by accident to two times in her past and then realizes that she was a part of those events twice. I believe that if time travel were ever possible that there would be no way to change the past and that there would be no parallel universes created. You would simply be a part of the past event or simply an observer. If you tried to change the past you would simply end up being part of the past that you remember. I don't believe anyone could ever become their own parent. Somehow you would not be able to kill your own grandparent. If you went back in time to change some major event you would likely end up with a better understanding of that event but in the end not be able to change it. If your part in that event ends up being significant and yet it was not recorded in history books it simply means that your participation was not recorded in the history books, perhaps intentionally or that no one witnessed how you affected that event. Who knows, your participation in the event could have been classified top secret by the government at the time and kept out of the history books.
Let's throw up a hypothetical scenario. You go back in time and stop the dropping of the atomic bomb. In the end the U.S. has to invade Japan and your grandfather was killed during the invasion. (assuming that the hypothetical "you" is from the U.S.) Under normal paradox issues that can't work because if you changed that then you wouldn't be born, so you couldn't change that. According to the relationship between cause and effect and time that Card puts forward you would be able to do that and it would change all of history. We end up in a world where you were never born, the U.S. was so weakened by the war in Japan that it didn't recover in time for the cold war and the Soviet Union became the dominant world superpower, but you don't dissapear. You are a random person floating around with no recorded birth. According to the current timeline you did not exist until the moment you arrived in the past and started changing things. In the current timeline you weren't born, but in the chain of cause and events you were clearly born, grew up, traveled back in time and changed history. What he's saying is that going back in time is not the same thing as going back in the chain of cause and effect. The previous history is wiped out completely, but it affected you, so it's effects live on in you. It affected you, you affected the timeline, so while what came on before is gone, it's influence is still there filtered through you.
let us suspend our disbelief for a while and say that time travel is possible. if you went back in time your mere physical presence changes something its not like you'd be invisible. I think that even this little disturbance causes either the parallel universe thing where its an alternate from what you know or it is the predestination theory by which you were meant to go back and step on that crunchy looking leaf causing the cahin of events that led up to before your time travel
I support the deterministic stand on this. If you were to go back in time, you already did so and did nothing (or something, but that is the history you remember) to affect history.
i see what you mean now. Here's a different scenario. Lets say you go back in time to prevent something insignificant as dropping a glass and failed, each time you went back would you see other versions of yourself failing or would you be stuck watching a doppleganger arriving from the future?
Going this route then to me it would be what you call predestination. I realize going back in time some things will change no matter how small. I would think that you could not change anything that would affect your past. Your memory of events would not change because your having been back in time would simply be a part of your memory if anything you did while in the past impacted yourself in some way. So if there was a plate of cookies with 5 cookies on it where you were on 8 Sep 08 at 9:47AM. Then lets say a year later you decide to go back in time and change the number of cookies that was on that plate at 9:47AM. Too me somehow you would not be able to because you remember there being 5 cookies there. So if you went back to 8 Sep 08 at 9:35AM a time you were not in the room and found 7 cookies on the plate. If you then ate more than 2 cookies then someone else would find a way to place enough there between your two visits to make the number be 5 or you would simply find that you had mis remembered how many cookies were there at 9:47AM. But ultimately I would think that whatever condition you left the room in from your journey back in time then that is the condition that you would have seen or remembered before you time traveled with the intent of making a direct change that should affect you. I hope I was able to explain that good. I always find it tricky when thinking about time travel and how to change past events.
I think, and I stress "think" because I'm not sure if I got this right, that you would end up with multiple copies of yourself. You miss the glass, so you live you life in such a way that you end up with access to a time machine, let's say you build one. You go back in time, and since you haven't changed anything you see the original you trying to stop the fall. Let's say you try to help out and the both of you still fail. You talk to yourself and explain who you are. This is where history changes. The new "old" you now knows that he can invent a time machine, so he goes on and does it. Meanwhile the new you goes on and lives his life doing whatever, perhaps he makes another time machine. Whichever one finishes his time machine first is the one who goes back in time, and the other one is erased from influence beyond the point of the glass. The newest version of you then sees the other two and has the choice of interfering again. Then you end up with three versions of you that are able to make a time machine. Again the first one to finish his machine and travel back is the only one to travel back, and he sees the other ones.
True, and it's not as unrealistic as it sounds. There are physicists who believe our universe splits into infinitely many copies every second, since that would explain some peculiarities in the random behaviour of microscopic particles. In this theory, a time traveller travelling back to his own past would find another copy of himself. He would leave behind a universe (A) where he's missing from the point that he steps into his time machine, and enter a parallel universe (B) where he suddenly pops into view and exists alongside a younger version of himself. Both copies of the time traveller will remain in universe (B) until their deaths, unless one of them decides to go on a new time trip. That person will leave behind a universe (B) where only one copy of himself remains from that moment on, and enter a new parallel universe (C) with two copies of himself. This theory assumes that the time line is singular and unchangeable. The tricky part is to explain what prevents the time traveller from changing anything. Is it a physical force, that will simply stop him from raising his arm and firing his gun at his grandfather? Or maybe a mystical force, that causes events to conspire against the time traveller (the bullets in the time traveller's gun are mistakenly exchanged for blanks, the time traveller to step on a twig and warns his grandfather just as he is about to shoot, and so on). In this theory, someone travelling back in time could become his own grandfather, but only if that was what happened "from the start". The time traveller doesn't change history by marrying his grandmother and conceiving his father; it's how "it always was". (I'm assuming that he marries his grandmother, since anything else would be indecent!) In this theory, the time traveller could also meet and talk to himself, but it would not be a second copy of himself. It would be the same copy at a different point in time. The older version of himself would remember having the same conversation, but from the viewpoint of his younger self. The younger self would grow old and end up entering the time machine exactly the way his older self described it - since he will become his older self. There are also more exotic time travel theories, like two-dimensional time. I think Asimov uses it in "The End of Eternity". In this theory, there is a single timeline, but every time trip causes it to change. The people living "inside time" don't notice the alterations, since everything is changed retroactively, including their memories of past events. But the people "outside of time", the time travellers, can see how the time line goes through iteration after iteration. Unfortunately, most movies, books and comics mix different time travel theories without much thought, leaving an impenetrable mess for the reader.
this was exactly what i was thinking but i got confused about how exactly you would find multiple copies of yourself at a scene. but what happens to the other copy who doesn't manage to go back in time? i mean if you're writing a story about it then it'd leave a big gap in logic making the reader feel cheated. So theoretically if you continued to fail to stop whatever it is you went back to do the number of your copies would increase? Then if you finally succeed with your team what then? This is a new approach that seems rather interesting let me see if i can find something on it. but i agree that it would work. this is confusing...
The other copy who doesn't make it back is erased because the timeline resets from that point. The only reason he is there at the scene of the event is because he was there already. If you wanted to reduce the number of copies all you have to do is appear a moment or two before the copy. Since he is erased from the future he can no longer travel back in time. If you arrive a moment after him, then he is still there and things continue as said before. If you finally suceed with your team then everybody goes their seperate way and try to figure out how to live in a world that has a record of only one of them. I imagine it would be very hard for the copies to get jobs or do anything that requires an oficial record since the only one is held by the first guy. If they all used the same social security number to open up multiple bank accounts, hold multiple jobs, and get multiple passports to go to different countries and start a new life it would appear very suspicious on the official records. There would probably be an investigation. Who knows, mabey they would end up having a death match where the only one left alive gets to take on the "normal" life.
I thought about this and it looks like what i thought of is pretty similar to the whole "Causality vs Time" theory mentioned before. If you go back in time then you could kill your own grandfather, and nothing would happen. This is because you already exist, independant of whether you alter the events that happen. However, i think the most important thing to consider, which hasnt been mentioned yet, is how time travel is acheived. And i dont mean that we sit here and try to puzzle out a way to make working time machine . I mean that in any time travel hypothetical, it all comes down to the method of time travel. In my view, the most feasible method for a person to time travel (akin to saying the most pleasurable method of torture ) would be, for example, to put them in some sort of pod, and then in some way reverse time outside of the pod. if that was the method of time travel, then i would say that the theory mentioned above would happen. E.g. time is a straight line A______________(C)_________B where A is the beginning and B is the present, if you "rewound" time around you until it reached C, then you arriving at C would be the new present, and everything leading up to B would be effectively erased. (though this includes your birth etc. you already "exist" at C so it doesnt matter that your birth is erased ) However, if you assume that time is a straight line A____________B______C__________D Where A is the beginning and D is the (hypothetical) end, and you somehow had a method to jump about it at will, e.g. from C to B, then the determinism theory comes into play, where everything has already "happened", so whatever you do from point B onwards will already have "happened" so will lead to point C and eventually to point D. If you go with the infinite parallel universe theory (which i will NOT attempt a diagram of ) then your method of time travel would involve somehow inserting you into a changing universe somewhere, which would effectively create a new universe (the one where you are inserted), which would then split off infinitely as well. A bit like creating a new "branch" somewhere in this crazy, infinite tree of universes. So if you go with this, then not only would there be infinite parallel universes that branch off without you being inserted, there would be infinite parallel universes that branch off with you being inserted So yeah the way i see it, the hypothetical "answers" to time paradoxes basically come down to how you hypothetically managed this time travel, which in turn is based on your idea of what the timeline is. I personally think the timeline is just a straight line from the beginning to the present, rather than infinite parallel universes where every possibility is played out or whatever. Depending on what you imagine the timeline to be, you'll probably have a different idea of which time travel theory would happen if we tried it out.
I'm currently reading Frederik Pohl's Time Patrol, which uses this model of time. There's a very good discussion of several models of time, and how they would affect causality loops, in James P. Hogans Thrice Upon a Time. I rather like the dynamic model of time he settles upon for the story.
Basically it is all theory at the moment and chances are we are completly wrong. We could be thinking like scientists hundreds of years ago, that the world was flat. We could be going wrong severly. So until someone slingshots round the sun at a high warp speed and proves any of this, im a sceptical to say the least. Fun to think about though
I was gonna write a novel about time travel, but ended up ditching the idea. It was just too much heavy thought. Maybe some other time. My basic premise was that the time machine wasn't just a "time" machine, but was actually capable of crossing over into other parallel universes and even existed in its own universe, independent of all others. The first time someone uses the machine, he or she is severed from his or her time line and becomes tethered to the machine's universe, allowing him/her to do as he/she pleases (killing your parents, altering history, etc) without any personal repercussions. The key to writing time travel pieces is getting your PPPs (paradox prevention protocols) straight, and I had no idea where I was going with mine.
I only read the first few posts so this is my response to the OP. Here are my explanations to the paradoxes. Let's say you try to go back and kill your grandfather. You succeed. The theory is that this will branch into another universe. Frankly, I don't buy this theory because there is no clear distinction as to when another universe will be created. Another theory is that you would fail if you tried to kill your grandfather. Let's take your example of the man whose house caught on fire. If he were to go back in time, this theory states that no matter what he did, he wouldn't be able to prevent the fire. And yet another theory is that you can't go back in time before the time machine was invented. You can only go into the future and as far back as to when the time machine was created. As for the theory about being your own father, that wouldn't be possible because the child that is born is not you since you're the father and not your dad. (hope that made sense).
I guess my personal take on the matter would be more along the lines of the butterfly effect. You may have one set goal for change in mind, but how many other changes will be set into motion from seemingly unnoticeable actions? Every footstep could lead to even greater changes than the intended change. And how could there be any way of calculating the probability that a given change in events would have the desired end result that far down the path of subsequent reactions?
I found the Butterfly Effect scenario too purposefully pessimistic. I doin't believe the universe would single-mindedly punish someone for tampering with the timestream (there was really nothing random about it). As for the butterfly effect theory itself, that miniscule changes will result in huge deviations "downstream", I think it is very unlikely as a general rule - it flies in the face of chaos theory, which had not yet been considered whan the butterfly effect notion of time travel was first proposed. I feel that if causality paradoxes are possible, most timestreams are self-stabilizing, just as most water streams would not be greatly altered by dropping in a pebble. Some events, however, could be far less stable. Small changes in the handling of the Cuba Missile Crisis could have had devastating long term effects. But assassinating Hitler as a child would probably not have deflected WW II, because the social and economic conditions in Germany after WW I left a vacuum for that type of leader to take control. The names would have changed, but the war would probably have taken place and followed much the same course.
I recently read a book called Corrupting Dr. Nice by John Kessel. The book is set in the future, in which time travel is a tourist thing. Like, you can go to ancient Rome, but people from the future have built modern resort hotels there. It explains it in the book in a way that makes sense. I would have to re-read it to explain it satisfactorily.
