The Grandfather Paradox

[|RK|]

Time for a lighter debate. Ok, now you all should know that some scientists are beginning to believe that time travel could be possible, and now instead of viewing time as a stream, they use a whirlpool for a model.

So, the Grandfather Paradox is the paradox that says...

You go back in time to destroy something. You succeed. Then would you have really gone back in time? Meaning you wouldn't have destroyed that thing, meaning you could go back in time, and it loops infinitely from there.

Is the Grandfather Paradox actually sound? Shouldn't time correct itself?

Bring whatever into this debate, video games, etc. But keep it sorta serious. That means no Futurama or the like. Also use only the closest to realistic evidence from these sources.


I personally believe that it is impossible for time to circle infinitely. If time didn't move, then nothing would move. Whether or not time can circle itself is irrelevant. How can events over a short period of time continue to repeat themselves? This is not possible. I figure that time would eventually correct itself, meaning that it would have moved on as normal from jumpstart.

EDIT: http://www.pbs.org/wnet/hawking/mysteries/html/kaku1-1.html

 

[2001]

Not to be rude, I believe every part of your post, but could I see a source? I havent heard of this until now but it sounds really cool so i'd like to read more about it until I start discussing it. Thanks.

 

[|RK|]

http://www.pbs.org/wnet/hawking/mysteries/html/kaku1-1.html

Thar ya go, buddy!

 

[Eor]

It would be impossible to "succeed". If you would succeed, then obviously you'd never go back in time, and it would be a paradox. Therefore, it's impossible for you to actually do it. Beyond that, going back in time is in itself impossible in the sense people think of it. If you would go back in time, it'd be like rewinding a video tape. It's not possible to "teleport" into some earlier time period.

 

[Lixivium]

Well you could theoretically do it, but you would be unable to "change the future". The chain of events that led up to you traveling back in time would be already pre-determined and contingent on you having traveled back in time.

 

[KrazyGlue]

I could imagine someone being able to see the past, but not change it. Because obviously if they did something it would mess up things in the future. I don't think the future is pre-determined. For instance, if the inventor went back in time and for some reason they did something to cause their parents to die... well, then it's a paradox.

 

[Eor]

I could imagine someone being able to see the past, but not change it. Because obviously if they did something it would mess up things in the future. I don't think the future is pre-determined. For instance, if the inventor went back in time and for some reason they did something to cause their parents to die... well, then it's a paradox.

His parents wouldn't die, because that would create a paradox which can't happen, besides a person cannot go in the past like that. With what we know, it's scientifically impossible for someone to do that.

 

[RDK]

I read an article somewhere in a physics journal about scientists contemplating the nature of time travel if it were to become possible, and one physicist likened it to a sort of film reel with a built-in limit.

Basically he said that when you finally created the time machine, you would be able to go back in time, but only up until the point you actually built the time machine, because any time before that would cause impossible paradoxes. So there would be no going back and seeing extinct animals like dinosaurs, or anything like that.

 

[Miggz]

Nah, I don't believe its possible. Although the idea is very fascinating nonetheless. But if one where to succeed, it would be extremely frightening. I wouldn't want it to happen. Its just so many other scenarios that I could think of that wouldn't make the journey worth it.

 

[Vickey]

I read an article somewhere in a physics journal about scientists contemplating the nature of time travel if it were to become possible, and one physicist likened it to a sort of film reel with a built-in limit.

Basically he said that when you finally created the time machine, you would be able to go back in time, but only up until the point you actually built the time machine, because any time before that would cause impossible paradoxes. So there would be no going back and seeing extinct animals like dinosaurs, or anything like that.

With this scenario you would still be able to see yourself as a younger person. That's still an impossible paradox and scenario when viewed with logic. If a time machine were to be created it seems more logical that it could only take you back to the time-frame of your own lifetime.

It seems very unlikely that a time machine could ever be developed, because time is for the most part linear. The only proof that there has been to give for the possibility of time travel is the breaking down the properties of time at light speed. However, going back in time farther than your own lifetime or the creation of the time machine seems impossible. If that was the case, we would have known if time travel existed by now, from the travelling of future generations.

 

[Nysyarc]

The only proof that there has been to give for the possibility of time travel is the breaking down the properties of time at light speed.

Therein lies the problem. Only light can reach the speed of light. No object with any amount of physical mass can ever match the speed of light without destroying itself, since it would take way too much energy. If time travel were possible, I don't think light would have anything to do with it, but even if it did, we would have to transform ourselves into light in order to time travel... which would be destroying ourselves anyways, unless we devised a way to safely return to flesh and bone.

If that was the case, we would have known if time travel existed by now, from the travelling of future generations.

We wouldn't necessarily be aware of such instances. Another problem with time travel is that the machine that executed it would have to also be able to transport the person to a set location. If you simply 'traveled back in time', that's too vague; you could end up floating in space several thousand light-years from our solar system. I don't think time travel will ever be possible, but even if it will be possible and people will try it... I doubt we will know about those attempts.

In any case, time travel to the past would be useless, because everything you do in the past will have already happened in your own past. If someone traveled back in time, it is still the present for them, but it is the past for the rest of the world, and it is still exactly as it happened in the first place. In other words, that person existed as a younger and older version before, and their younger version could have seen their older version (but nothing the older version does will change what actually happened, because whatever they do... already happened).

That brings to mind the movie Twelve Monkeys. The movie ends with two characters who have travelled back in time; one of the two dies, and then the other sees the younger version of the person who died. Since the younger person is obviously still alive, and will eventually die in the same manner when he is older, is time a constant loop? I don't believe it is, because for anyone who did not travel back in time, it continues. Maybe for someone who does go back in time and ends up dying before returning to the present, time is an endless loop, because no matter what they do, they will always end up going back in time and dying when they are older.

 

[AltF4]

Okay, let's first analyze what "Paradox" means in the context of science:

A "Paradox" is just a fancy way of saying "Something that is highly counter-intuitive". There are no "true" paradoxes in the sense that they produce real contradictions. Contradictions are impossible. What a Paradox is in science, is a situation (which appears to be reasonable) but then leads to a contradiction. Paradoxes are interesting because they demonstrate that what we THINK is reasonable is actually wrong. In other words, they demonstrate failings in our current understanding of the world.

Well known "Paradoxes" include the EPR Paradox, Zeno's Paradoxes, of of course the Grandfather Paradox. Some have been "solved", which in this sense means that we have fully explained how the contradiction inherent in the paradox do not occur. Others we have not yet.



The Grandfather Paradox says the following:

1) Suppose that time travel into our own past is possible.
2) Suppose that we have Free Will to act upon anything we wish.

Conclusion: Contradiction. Given both premises, it would be possible to act in the past in such a way as to violate causality. Namely, murdering one's own grandfather. (Note that the Grandfather Paradox holds for ANY action made while time traveling. Not just the murdering of one's family. But this the most obvious.)

Possible resolutions to the paradox now become apparent. One of the two premises above needs to be false.

A) We cannot travel into our own past. (Note that we could still travel into someone else's past, where the murdering of people is of no consequence, because they are not related to you.)

B) There is no such thing as Free Will.

C) There is no such thing as Free Will WHILE time traveling.


Take your pick. But it currently looks like B) is true. (IE: No "Free Will")

 

[L666]

I'll address the two paradoxes from the article:

One stubborn problem with time travel is that it is riddled with several types of paradoxes. For example, there is the paradox of the man with no parents: What happens when you go back in time and kill your parents before you are born? If your parents died before you were born, then how could you have been born to kill them in the first place?

You were born.
You travel back in time.
You kill your parents.
You are not born into the future, but you still exist in the present (of the past). No contradiction.

There is also the paradox of the man with no past. For example, let’s say that a young inventor is trying futilely to build a time machine in his garage. Suddenly, an elderly man appears from nowhere and gives the youth the secret of building a time machine. The young man then becomes enormously rich playing the stock market, race tracks, and sporting events because he knows the future. Then, as an old man, he decides to make his final trip back to the past and give the secret of time travel to his youthful self. Where did the idea of the time machine come from?

Youth spends lifetime building a time machine.
Old man travels back in time to give the secret to his former self and presumably dies off somewhere.
After his former self enjoys life, he repeats the cycle and effectively stagnates time forever. No contradiction.

 

[t3h n00b]

This sounds like the easy/lazy answer, but I think that an answer to the situation is legitimately impossible, and that's why a time travel machine can't be invented. If your time travel changes something from the past, you won't enter into the future you left. Like I don't think an answer can be given in terms of the real universe if you're also involving time travel. This is a cool topic though.

 

[Vickey]

Okay, let's first analyze what "Paradox" means in the context of science:

A "Paradox" is just a fancy way of saying "Something that is highly counter-intuitive". There are no "true" paradoxes in the sense that they produce real contradictions. Contradictions are impossible. What a Paradox is in science, is a situation (which appears to be reasonable) but then leads to a contradiction. Paradoxes are interesting because they demonstrate that what we THINK is reasonable is actually wrong. In other words, they demonstrate failings in our current understanding of the world.

Well known "Paradoxes" include the EPR Paradox, Zeno's Paradoxes, of of course the Grandfather Paradox. Some have been "solved", which in this sense means that we have fully explained how the contradiction inherent in the paradox do not occur. Others we have not yet.



The Grandfather Paradox says the following:

1) Suppose that time travel into our own past is possible.
2) Suppose that we have Free Will to act upon anything we wish.

Conclusion: Contradiction. Given both premises, it would be possible to act in the past in such a way as to violate causality. Namely, murdering one's own grandfather. (Note that the Grandfather Paradox holds for ANY action made while time traveling. Not just the murdering of one's family. But this the most obvious.)

Possible resolutions to the paradox now become apparent. One of the two premises above needs to be false.

A) We cannot travel into our own past. (Note that we could still travel into someone else's past, where the murdering of people is of no consequence, because they are not related to you.)

B) There is no such thing as Free Will.

C) There is no such thing as Free Will WHILE time traveling.


Take your pick. But it currently looks like B) is true. (IE: No "Free Will")

Your option "C" seems like the most likely. It makes no sense that if we can time travel that we cannot visit our own pasts. Therefore it makes the most sense that we would not be able to affect any of the outcomes of the past. This would mean we would almost be like spectres, able to view the past, and walk around in the past, while not being able to affect anything. We would be virtually inexistent (invisible and ethereal) to the people of that time.

Were this not the case, our world would have already been affected. People would have travelled from the future already, and we would be aware of time travel. Up until this point we have had no evidence that time is anything but linear, and it does not seem like we would be able to affect it.

A time machine that would allow us to simply view the past while not being able to affect it seems to be the most logical.

 

[AltF4]

I want to make something more clear. When I say "our past" there is something very specific I'm referring to. Sometimes you'll hear someone say something along the lines of:

"Maybe time travel is possible, but you'll form an alternate timeline, where you can affect the past without causing contradictions."

This isn't actually time travel at all. It's just space travel. And space travel isn't all that interesting, you do that every morning on the way to work/school! To illustrate why the above is NOT time travel, let me use a hypothetical situation...


Suppose that you buy two houses, each identical to one another. One of the houses you live in, and one of the houses is left alone. You then continue to live in one of the houses for many years. The dishwasher starts to break, the beds start to creak, and it in general begins to wear.

Suppose you then moved to the other house, the one that has not been used. As you walk through the door, it would appear that you've traveled through time! Your dishwasher will be brand new, your bed no longer creaks! For all intents and purposes, you've traveled back in time to when you first bought the house!

But this is of course not what actually happened. You didn't time travel, you just moved across the street!

Similarly, traveling to an "alternate timeline" is exactly the same thing. You are not traveling through time, but rather space. You are moving to another universe which just APPEARS to be like your past. But it is not your past, just like the second house is not your house. It just looked like it.


When we speak of "time travel", we are talking about REAL time travel. Which necessitates that you have to be traveling to "your own" past.

 

[Mic_128]

That's more traveling in Dimensions than Traveling in Space, imo.

 

[Ryan Ludovic]

Currently, time-travel can be possible without the paradox of "If you kill your grandfather, you will not cease to exist because then no one would be born to kill your grandfather" because of a multi-dimensional and infinate matrix of time. What this means, is that every choice you make, places you directly on linear with your timeline in another dimension of reality. This ofcourse, goes on scales that consider time the 4th dimension, and include that of 10-11 dimensions.

Whittingly put into a song I enjoy:

every time i move i'm in another dimension
everything i do changes what i want
i see a choice i make explode in thousands of pieces
every time i choose i become a shard

 

[AltF4]

That's more traveling in Dimensions than Traveling in Space, imo.

Well, what is a "dimension" then? The word "dimension" is often misused by science fiction authors to mean "alternate universe". A dimension is really just a direction. So I would avoid using the word "dimension" in that sense.

Traveling to another universe (assuming a multiverse exists) is travel through SPACE, however. Not time. It is not time travel, like I had said last post.

Currently, time-travel can be possible without the paradox of "If you kill your grandfather, you will not cease to exist because then no one would be born to kill your grandfather" because of a multi-dimensional and infinate matrix of time. What this means, is that every choice you make, places you directly on linear with your timeline in another dimension of reality. This ofcourse, goes on scales that consider time the 4th dimension, and include that of 10-11 dimensions.

An "infinite[sic] matrix of time"? You have no idea what you're saying do you... Neither have you read anything I just posted. Both is bad if you're trying to get access to the DH.

 

[Disfunkshunal]

Currently, time-travel can be possible without the paradox of "If you kill your grandfather, you will not cease to exist because then no one would be born to kill your grandfather" because of a multi-dimensional and infinate matrix of time. What this means, is that every choice you make, places you directly on linear with your timeline in another dimension of reality. This ofcourse, goes on scales that consider time the 4th dimension, and include that of 10-11 dimensions.

Whittingly put into a song I enjoy:

think about this, the past is anything that has already happened ok? let's say that i kill someone and then i am immeadiately arrested, the killing i did is in the past. If somehow went back into time to stop myself i would only change what could have happened. An alternate dimension would not be created in any way. Just think, if an alternate dimesion was created wouldn't you be absent form the first dimension and affect the current and future events in that way? Also depending what and how many things in the past you change in theory there would be thousands of dimensions.

i think if time travel was possible like alt said in his 'c' option we would only be able to watch what goes on. i explained why i think alternat dimensions wouldn't work, another popular belief i want to

Deja vu
i think if time travel was possible this would be the lesser realistic of the two options. If this was the case then in all instances of time travel there would be no evidense except memories of experincing the event before. Going back to my past example of murdering someone, going back before i muredered them would be me in the same place i was at the same time, right? This would be me away form a time machine and possibly out of reach of it. i will know what the events are that are about to take place but would i know i time traveled? I think the idea of being able to genuinel relive something is a lot less realistic than the one below.

being able to watch the past as your present self
If this were to occur, you would be able to only see what happen and think about what could have happened. in theory you cannot meet your pass self without something going wrong. in acctuality you two are the same being and it is impossible to be in to places at once.

 

[Ryan Ludovic]

(Note that we could still travel into someone else's past, where the murdering of people is of no consequence, because they are not related to you.)

No. If I pay you $100,000 to murder me in the past, i will not exist to pay you, and the paradox takes on meaning again. Also. ANYTHING you do can then influence the future that could possibly influence your decisions on time travel. It could either convince you to not time travel at all, or influence how you act, so when you go in, you can then make DIFFERENT choices, and these would stack creating an infinate end result of everchanging history.
Unless you suggest that is what would happen.

"Maybe time travel is possible, but you'll form an alternate timeline, where you can affect the past without causing contradictions."

This isn't actually time travel at all. It's just space travel. And space travel isn't all that interesting, you do that every morning on the way to work/school! To illustrate why the above is NOT time travel, let me use a hypothetical situation...


Suppose that you buy two houses, each identical to one another. One of the houses you live in, and one of the houses is left alone. You then continue to live in one of the houses for many years. The dishwasher starts to break, the beds start to creak, and it in general begins to wear.

Suppose you then moved to the other house, the one that has not been used. As you walk through the door, it would appear that you've traveled through time! Your dishwasher will be brand new, your bed no longer creaks! For all intents and purposes, you've traveled back in time to when you first bought the house!

So what you are saying, is that the houses are DIFFERENT timelines?
Because if not, this metaphor is simply disinformation unless you are addressing it as so.

An "infinite[sic] matrix of time"? You have no idea what you're saying do you... Neither have you read anything I just posted. Both is bad if you're trying to get access to the DH.

Firstly, this is a debate. You have not even addressed your belief, only provided unsourced information.

Have I read what you wrote? Yes. Have you considered my opinions, or have you just grabbed your nose and stuck out your tounge.

Your house analogy is poor.

When you travel back in time, it is linear. When you influence a CHANGE only then does it become a new decision on a new path to a new future.

time travel is only possible IF you can have a situation like I previously mentioned. In any other situation, I do not believe time travel is possible.

 

[AltF4]

No. If I pay you $100,000 to murder me in the past, i will not exist to pay you, and the paradox takes on meaning again....

No, no. You are just misinterpreting what I'm saying. The point of the sentence which you quoted can also be phrased as:

"Note that we could still travel into the past of an alternate universe, where the killing of people will have no consequence because it does not impact your universe."

Perhaps that makes better sense.

So what you are saying, is that the houses are DIFFERENT timelines?
Because if not, this metaphor is simply disinformation unless you are addressing it as so.

No, the houses are not different timelines. They are just different places within the same timeline.

The houses are similar to traveling to another universe. (Sometimes erroneously referred to as a "dimension") The houses illustrate why traveling to another universe does not constitute time travel, despite it appearing to be.

Firstly, this is a debate. You have not even addressed your belief, only provided unsourced information.

And I am a moderator, in case the red name didn't give it away. I am not here to debate you. I am here to provide structure and information. If you would like sources, go to a university level physics course. Or go to Wikipedia. Both are excellent sources of information.

Have I read what you wrote? Yes. Have you considered my opinions, or have you just grabbed your nose and stuck out your tounge.

This is not a matter of opinion, but one of fact. It is, actually, not a very good debate hall thread for this very reason. This is a scientific topic, not one where opinions even make sense.

If you have a belief or an 'opinion', it must be supported by evidence.

Your house analogy is poor.

Then surely you can demonstrate to me exactly where it fails.

When you travel back in time, it is linear. When you influence a CHANGE only then does it become a new decision on a new path to a new future.

Linear? Nothing about time is linear. Einstein put that to rest a hundred years ago.

time travel is only possible IF you can have a situation like I previously mentioned. In any other situation, I do not believe time travel is possible.

Well, unfortunately for you, time travel IS possible. And in fact happens all the time. And does not happen "in the way you described" where decisions (can you even try defining a "decision" for me?) create alternate timelines.

The physicist Richard Feynman did much early work in quantum mechanics, specifically particle-antiparticle collisions. What's most interesting about this is that antiparticles can be seen as normal particles moving backwards through time.

There is, in fact, only one particle, not two. The particle moves forward in time, then stops, moves backward in time (at which point we'd observe it as an "antiparticle") then begin moving forward again. (see bottom of the page on this link)

This is called a Closed Timelike Curve.

 

[Vickey]

So we're coming to a conclusion that the alternatives are either


A- Time / Dimension / Space travel is impossible.

B- We may be able to travel through time, but unable to affect it, only witness it.

C- We may travel through time (or space) into an alternate similiar universe, but not the same one. Things affected there will not affect our time.

D- We can travel to our own past only, affecting anything in the present that happened within our timeline.

E- We can travel to the past change it, but that would form a different timeline (Could also be C, except that in C the universe already exists, we do not create it)

F- We can travel as far as the existence of the time machine, altering any events up until that point.



Just felt like throwing some organization into this debate.