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Time travel theory avoids grandfather paradox

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If I'm understanding correctly, most of you are missing the point.
The post simply attempts to prove that if you should succeed in going back in time to the past, you would be unable to kill your own parents no matter what you try.
It's essentially an attempt to scientifically prove causality.

Personally, my favorite theory on time travel is as follows:
You'll never know whether or not you will travel back in time, and trying to change the past is impossible. When turning back the clock, you turn back the clock of all observers in the universe as well. With no way of detecting that you have traveled backwards, you will have no way of knowing whether the past has been changed.

Besides, for all we know, the entire universe is actually moving backwards in time (backwards from out perspective) and there's a whole system of worlds and life forms that travel backwards with it.
 
Sahakiel said:
If I'm understanding correctly, most of you are missing the point.
The post simply attempts to prove that if you should succeed in going back in time to the past, you would be unable to kill your own parents no matter what you try.
It's essentially an attempt to scientifically prove causality.

Personally, my favorite theory on time travel is as follows:
You'll never know whether or not you will travel back in time, and trying to change the past is impossible. When turning back the clock, you turn back the clock of all observers in the universe as well. With no way of detecting that you have traveled backwards, you will have no way of knowing whether the past has been changed.

Besides, for all we know, the entire universe is actually moving backwards in time (backwards from out perspective) and there's a whole system of worlds and life forms that travel backwards with it.
Click to expand...

And conversely, hypothetically if you were able to kill your grandparents, you would not be allowed to go back in time.


I also like that second theory the most. It also implies that time can be going backwards for us all the time, just in order for time to go backwards, all information (or in our case memory) of the present has to be undone or erased.
 
I don't understand why physicists waste their time trying to prove time travel into the past is possible. It's not, and attempting to prove that it is is a colossal waste of effort. It's a sci fi device used for entertainment. I don't see biologists trying to prove how it could be possible for a human to fly like superman.
 
Kev said:
I don't understand why physicists waste their time trying to prove time travel into the past is possible. It's not, and attempting to prove that it is is a colossal waste of effort. It's a sci fi device used for entertainment. I don't see biologists trying to prove how it could be possible for a human to fly like superman.
Click to expand...

iirc time travel into the past is an implication of general relativity.


could be that our understanding of the past and why it is the past is incredibly naive.



anyway, this particular theory basically says that if you tried to kill your grandfather before you were born the gun would jam, the bullet would misfire, a gust of wind would blow it away, the knife would break, your hand would break, something. odd events would happen to prevent the really odd event from happening.
 
If you go back in time and kill your grandfather then you would not be born, could never have built a time machines, and gone back to kill your grandfather.
 
Patranus said:
If you go back in time and kill your grandfather then you would not be born, could never have built a time machines, and gone back to kill your grandfather.
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yes thats the classic description of the paradox.

BUT...if you go back in time..at that point...its not yet DETERMINED that its your grand father.

The relationship to you only occurs through many circumstances "in the future". But since you travelled back in time..this future is not yet written 🙂
 
flexy said:
Easy "proof":

If you travel back in time to murder your grand father..you are NOT back in the actual, same time at that (past) date. Because the two pasts, the original one where you were not there and the one where you murder your GF, are two different pasts.
(And will also have a totally different outcome)

From that point of view its not even a paradox...its PROBABLY like that you "simply" change the way how that one path goes..and find yourself not related to that guy who was your GFather in that one past.

The more interesting question...if you could go back in time and murder (what in this one time line/reality) was your GFather.....but then are able to GO BACK in the same original time-line where you started. (This would be paradox and should logically not be possible.)

Eg. i cannot go back in time, kill hitler, and then return back where everyone remembers 3rd reich and hitler,although i killed him before he even came into power...

OP: I dont understand what you posted, even after multiple reading. What is post-selection? What does that theory say? Sorry...lost...
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But what if at the same time your version in the parallel universe goes into your universe and you both kill your grandfathers?? Then what??
 
flexy said:
yes thats the classic description of the paradox.

BUT...if you go back in time..at that point...its not yet DETERMINED that its your grand father.

The relationship to you only occurs through many circumstances "in the future". But since you travelled back in time..this future is not yet written 🙂
Click to expand...

I disagree.
If someone else becomes your grandfather your fathers genetics as well as your genetics will be different. This coupled with his upbringing would have significant impact on their life choices and outcomes and would possibly lead to your father never meeting your mother and most certainly put you in a different situation where you would/could not build a time machine.

Your future has to be written at that point because if it wasn't you wouldn't have been able to travel back in time.
 
JS80 said:
But what if at the same time your version in the parallel universe goes into your universe and you both kill your grandfathers?? Then what??
Click to expand...

The point of the multiverse theory is specifically to counter that. Both you and you from the other universe will jump to a universe that had your respective grandfathers murdered and you never existed.
 
Iron Woode said:
I love these threads.

too bad all this violates the laws of causality.
Click to expand...

uhm..causality is WAY too simple in that time of quantum physics 🙂

Event A results in state B which results in state C..etc...etc...

It should be impossible to manipulate A ...the fact alone that you change "A" (with your presence alone)...does make it only a similar looking copy of "A."

In other words:

The past where you smash a hammer over your "Grandfather"'s head is ANOTHER past as opposed to the past where you did not visit.

Since its another past you don't violate causality. <-- ???
 
KIAman said:
The point of the multiverse theory is specifically to counter that. Both you and you from the other universe will jump to a universe that had your respective grandfathers murdered and you never existed.
Click to expand...

But if you never existed then you would have never gone back in time (other universe) to kill off your parallel grandfather.
 
KIAman said:
The point of the multiverse theory is specifically to counter that. Both you and you from the other universe will jump to a universe that had your respective grandfathers murdered and you never existed.
Click to expand...

Then that would mean there's a universe for every universe...which means there would be an infinite # of universes
 
Patranus said:
But if you never existed then you would have never gone back in time (other universe) to kill off your parallel grandfather.
Click to expand...

From that other universe that you never existed, yes, that is true, but you from the other universe will never jump to a universe where you existed in the first place.
 
Patranus said:
I disagree.
If someone else becomes your grandfather your fathers genetics as well as your genetics will be different. This coupled with his upbringing would have significant impact on their life choices and outcomes and would possibly lead to your father never meeting your mother and most certainly put you in a different situation where you would/could not build a time machine.

Your future has to be written at that point because if it wasn't you wouldn't have been able to travel back in time.
Click to expand...

Yes i agree,

but the key here would be to get away from that "linear" thinking, especially how we perceive "time" and how causalities are "lined up" on the time line. This is just how we perceive all this.

Is the future "written"?

If we take some multiverse theory...yes, all possible (infinite nr. of) futures are already "written" in some way (as possibilities)...a formerly "valid" one would just suddenly become invalid. ???
 
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