Could a TTer change the past?

[Maddie]

um...interesting.

[imomar]

what if u couldnt travel to a time b4 the time machine was invented?
just a though

[my name would go here]

The story with the dinosaurs and the butterfly changing everything is called "A sound of thunder"

[Gardez]

Hello imomar,

A TM that would only allow you to travel back to the moment it was created is called a CTC, or close timelike curve.
Also the machine would have to remain on at all times. Professor Mallet at Connecticut University is working on a 'CTC'.

There are many other possible TM's that work with singularities (Kerr), Event Horizons (Professor Hawking), wormholes (Professor Thorne at CalTech), energy below the ZPF/ZPE (ANEC), FTL 'spaceships' (Physicist Cramer), huge m@ssive rotating cylinders (Professor Frank Tipler) ,etc.

If you hovered near an EH and traveled back to earth you could find yourself thousands of years in the future.
(Einstein's GTR)

But if you wanted to go 'back' you'd probably have to go hunting for a wormhole, and pray for a lot of luck.

Or maybe a (Professor) Kerr singularity.

:-)

I'm currently looking into ANEC and Bondi K-Calculus....arghhhhhhhhhhhhhhhh!

[doublegulp20]

Ok so this may be a little hard to follow because even i am still cofused with what i am trying to say so here it goes.

Say that i am sitting here on may 30th 2004 and i have a badly scared face from being in a fire 4 years ago. I TT back 4 years ago and prevent the fire which means that on may 30th 2004 i will no longer have a scarred face. But how did i do it and when did i do it? Am i supposed to travel back 4 years, prevent the fire and then relive the the 4 years of my life over again? Or do i go back to the present day, may 30th 2004 and have a scar free face? If i keep the memories of time travel with me then reliving 4 years would be a pain in the arse, and if i keep the memories but return to the present day, how will i know how me not being in the fire 4 years ago affected my life? I believe that if one time travels backwards, it is impossible to go back to the day they started. So we would be forced to relive the 4 years again. In tru calling it is only one day she has to repeat with all her memories, imagine repeating years. Would it be worth it? The one way that a person can TT without going insane is to have no memory of the time travel and go on living as if nothing has happened, so we actually could have live our lives more than one and not know it. So i am sitting here in front of my computer, how do i know if this is the first time or if it is the second time after the travel?

Although now that i think about it, it would be impossible to travel back in time with no memory of the future because then we wouldn't know what we came back to do. If tru didn't remember already living the day once, how does she know how to change it. So i think that traveling back in time is impossible to do without keeping the memories of the future and it is not worth reliving all over again when you know you have done it before.

There is one more thing i would like to look at if i haven't lost you guys already. Say it is possible to go back 4 years, avoid the fire and then return to the present day, would all the memories you have had for the past 4 years stay the same or would they change to explain how life was different for 4 years without scars? Is it possible that all you can remember is the 4 years with the scars but have no idea what happened in the 4 years that you havent had the scars due to the TT? I know this part is confusing but it is really something to think about.

I would really love to hear comments or questions with my theory or what ever you want to call it. I am not scientist so if it makes no sense you should understand.

[doublegulp20]

Ok so this may be a little hard to follow because even i am still cofused with what i am trying to say so here it goes.

Say that i am sitting here on may 30th 2004 and i have a badly scared face from being in a fire 4 years ago. I TT back 4 years ago and prevent the fire which means that on may 30th 2004 i will no longer have a scarred face. But how did i do it and when did i do it? Am i supposed to travel back 4 years, prevent the fire and then relive the the 4 years of my life over again? Or do i go back to the present day, may 30th 2004 and have a scar free face? If i keep the memories of time travel with me then reliving 4 years would be a pain in the arse, and if i keep the memories but return to the present day, how will i know how me not being in the fire 4 years ago affected my life? I believe that if one time travels backwards, it is impossible to go back to the day they started. So we would be forced to relive the 4 years again. In tru calling it is only one day she has to repeat with all her memories, imagine repeating years. Would it be worth it? The one way that a person can TT without going insane is to have no memory of the time travel and go on living as if nothing has happened, so we actually could have live our lives more than one and not know it. So i am sitting here in front of my computer, how do i know if this is the first time or if it is the second time after the travel?

Although now that i think about it, it would be impossible to travel back in time with no memory of the future because then we wouldn't know what we came back to do. If tru didn't remember already living the day once, how does she know how to change it. So i think that traveling back in time is impossible to do without keeping the memories of the future and it is not worth reliving all over again when you know you have done it before.

There is one more thing i would like to look at if i haven't lost you guys already. Say it is possible to go back 4 years, avoid the fire and then return to the present day, would all the memories you have had for the past 4 years stay the same or would they change to explain how life was different for 4 years without scars? Is it possible that all you can remember is the 4 years with the scars but have no idea what happened in the 4 years that you havent had the scars due to the TT? I know this part is confusing but it is really something to think about.

I would really love to hear comments or questions with my theory or what ever you want to call it. I am not scientist so if it makes no sense you should understand.

[doublegulp20]

Ok so this may be a little hard to follow because even i am still cofused with what i am trying to say so here it goes.

Say that i am sitting here on may 30th 2004 and i have a badly scared face from being in a fire 4 years ago. I TT back 4 years ago and prevent the fire which means that on may 30th 2004 i will no longer have a scarred face. But how did i do it and when did i do it? Am i supposed to travel back 4 years, prevent the fire and then relive the the 4 years of my life over again? Or do i go back to the present day, may 30th 2004 and have a scar free face? If i keep the memories of time travel with me then reliving 4 years would be a pain in the arse, and if i keep the memories but return to the present day, how will i know how me not being in the fire 4 years ago affected my life? I believe that if one time travels backwards, it is impossible to go back to the day they started. So we would be forced to relive the 4 years again. In tru calling it is only one day she has to repeat with all her memories, imagine repeating years. Would it be worth it? The one way that a person can TT without going insane is to have no memory of the time travel and go on living as if nothing has happened, so we actually could have live our lives more than one and not know it. So i am sitting here in front of my computer, how do i know if this is the first time or if it is the second time after the travel?

Although now that i think about it, it would be impossible to travel back in time with no memory of the future because then we wouldn't know what we came back to do. If tru didn't remember already living the day once, how does she know how to change it. So i think that traveling back in time is impossible to do without keeping the memories of the future and it is not worth reliving all over again when you know you have done it before.

I would really love to hear comments or questions with my theory or what ever you want to call it. I am not scientist so if it makes no sense you should understand.

[Gardez]

Hi Double,

Interesting nic, considering your theory.


The short answer is that we simply do not know for sure. But we can speculate.

According to Einstein's theories time travel 'is possible', so thats not even a question.



Your theory/speculation asks the important question: 'Could a TTer change the past?'

The Great Stephen Hawking conceived the CPC or chronology protection conjecture.
The CPC said that nature itself would interfere with any time traveler attempting to change the past. For example, if someone traveled back in time and attempted to shoot their own GrandFather, their gun would jam and the TTer would fail in their attempt.

But since then Stephen Hawking has changed his mind and said that 'some bastard may be able to travel back in time and kill their own GrandFather'.
So we have some of the greatest minds of the last century saying that TT is possible and that a TTer could change the past.

What the results of such a journey would be, we don't know.
Suppose you stayed in the past after traveling there, then there would be two of you.



One the correct age for that time period
and another four years older.

Suppose that you decided to stay in the past.
What would happen once you reached your departure date again?

Would one of you simple cease to exist in that instant?

Even if you immediately traveled back to the time you left, what would happen to the other you that re-lived the last four years?

'What if' you continued to travel back in time to different events in your life and each time returned to the time you left?

[clintonbrant]

Gardez said:

LOL!

It took me a 'second'..

Give a man a fire and he'll be warm for a day,
Set a man on fire and he'll be warm for the rest of his life.
- Terry Pratchett - Discworld

I never heard that one b4.

Albert Einstein Said it was not possible ;D
that is good enough for me!

[LouisaB]

Interesting theories on this thread.

Personally I am a believer in that anything is possible. Maybe not right now but certainly at some point in the future. The light speed theory has been one I think hold the most water when it comes to time travel.

I think that if it were possible to travel to through time it would be possible to alter the past. But only on an impersonal scale. If you tried to alter it in a personal way then it would not be possible. I think that the new version of The Time Machine actually explains it quite well in that respect.

If you create a time machine to alter something in your past then once it is altered then why would you create a time machine in the first place? So then you don't have the time machine and the past is not altered and you end up in a time loop. I don't think the entire universe would unravel but you would be pretty much stuck. The only thing would be that you don't actually know that you are.

The killing the grandfather theory would wind up with a similar loop. Except the person would cease to exist as soon as the grandfather died. But if they don't exist then they can't have killed them and again you are going round in circles forever.

However even impersonal things might have an effect on the future. You just don't know.

If time travel were possible one can only hope it would be monitored very carefully. Though I think the universe is probably pretty resilient.

Does anyone know who wrote A SOUND OF THUNDER? Just curious as it sounds like an interesting read.

And great Pratchett quote! Though I must admit I prefer the books starring Death, especially Reaper Man. Too funny.

[JB]

Half and Half

[Somebody Help Me]

There was an episode of The Twilight Zone (I think), and this TT brings this old guy from the future back to the Nazi era, where he meets his younger self (a soldier killing people). The younger man (the soldier) is about to kill the older one (not realizing it is himself), when the older one pulls out a picture of his old red bike. The soldier freaks, and shoots him. Now, the soldier will (in theory) get old, and travel back, only to confront himself and be shot by his younger self.

Wouldn't this keep repeating? The younger shoots himself as older, grows up, goes back, gets shot, and the loop begins again.

If nothing is ever changed, and the TT returns to his natural time, maybe it is possible. But the slightest change could change all of humanity.

In the grandfather example, the kid (even though killing his grandfather) would still be alive, but let's say he didn't kill the GF and stayed in that time. Would there be two of him?

[JB]

When you were giving that example about that "The Twilight Zone" ep, it would be possible that there would a continued loop. But what would happen if after so continued loops, could a further-in-the-future self (about 100 years after the continued loop started) stopped its own future self?

[cb007]

Hmm this is confusin: