History Main / GrandfatherParadox

24th Jul '16 9:08:00 PM Geoduck
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->'''Rarity''': “How in Equestria is my travelling in time supposed to prove that time travel is impossible?”\\
'''Twilight''': “I explained this Rarity. Travel back along a given time line can’t be possible, because it could violate causality-—do you know about the ''Grandmother Paradox''?”\\
'''Rarity''': “No.”\\
'''Twilight''': “Suppose you travelled back in time to a point before you, and your parents, were born, and you killed your maternal grandmother…”\\
'''Rarity''': “Why would I ever want to do that? My grandmother is a delightful lady. Even if she does insist on wearing those dreadful frocks with such old fashioned sleeves.”\\
'''Twilight''': “But hypothetically—-suppose you did-—by accident-—”\\
'''Rarity''': “I would have trouble-—she’s a tough old mare.”\\
'''Twilight''': “Yes, but, ''theoretically'' you could do it-—when she was young. But then she would never give birth to your mother, so you would never be born—-so you could never go back in time to kill her-—it’s a paradox-—see!”

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->'''Rarity''': “How How in Equestria is my travelling in time supposed to prove that time travel is impossible?”\\
impossible?\\
'''Twilight''': “I I explained this Rarity. Travel back along a given time line can’t be possible, because it could violate causality-—do you know about the ''Grandmother Paradox''?”\\
Paradox''?\\
'''Rarity''': “No.”\\
No.\\
'''Twilight''': “Suppose Suppose you travelled back in time to a point before you, and your parents, were born, and you killed your maternal grandmother…”\\
grandmother…\\
'''Rarity''': “Why Why would I ever want to do that? My grandmother is a delightful lady. Even if she does insist on wearing those dreadful frocks with such old fashioned sleeves.”\\
\\
'''Twilight''': “But But hypothetically—-suppose you did-—by accident-—”\\
accident-—\\
'''Rarity''': “I I would have trouble-—she’s a tough old mare.”\\
\\
'''Twilight''': “Yes, Yes, but, ''theoretically'' you could do it-—when she was young. But then she would never give birth to your mother, so you would never be born—-so you could never go back in time to kill her-—it’s a paradox-—see!”paradox-—see!
16th Jul '16 4:05:52 PM nombretomado
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* In ''WesternAnimation/TheAdventuresOfSonicTheHedgehog'', one episode in the four episode arc about the Chaos Emeralds starts with Sonic foiling a plot by Dr. Robotnik to prevent his ancestors from marrying and thus eliminate Sonic from the timeline. Sonic succeeds in sending Robotnik packing, but then ''causes the paradox himself'' by ordering a chili dog from his maternal ancestor, causing his paternal ancestor to become impatient waiting to be served and leaves. After Sonic disappears, Tails solves the paradox in about a minute by forcing the meeting to happen.

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* In ''WesternAnimation/TheAdventuresOfSonicTheHedgehog'', ''WesternAnimation/AdventuresOfSonicTheHedgehog'', one episode in the four episode arc about the Chaos Emeralds starts with Sonic foiling a plot by Dr. Robotnik to prevent his ancestors from marrying and thus eliminate Sonic from the timeline. Sonic succeeds in sending Robotnik packing, but then ''causes the paradox himself'' by ordering a chili dog from his maternal ancestor, causing his paternal ancestor to become impatient waiting to be served and leaves. After Sonic disappears, Tails solves the paradox in about a minute by forcing the meeting to happen.
22nd Jun '16 11:07:26 AM PF
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So, then, killing your grandfather causes you to not exist, and since you don't exist, you never killed him. Which means he survives, so you exist, so you do go back to kill him. Which means he doesn't, so you don't; therefore he does, so you do, etc ... [[LogicBomb are you confused yet?]]

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So, then, killing your grandfather causes you to not exist, and since you don't exist, you never killed him. Which means he survives, so you exist, so you do go back to kill him. Which means he doesn't, so you don't; therefore he does, so you do, etc ... etc. [[LogicBomb are Are you confused yet?]]
22nd Jun '16 11:06:49 AM PF
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A type of TemporalParadox. The name comes from the most famous variation - namely "what would happen if you traveled back in time and killed your own grandfather?", but also applies to anything that happens while time traveling that should logically make your original time travel trip impossible or unnecessary.

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A The grandfather paradox is a type of TemporalParadox. The name comes from the most famous variation - variation, namely "what would happen if you traveled back in time and killed your own grandfather?", but grandfather?" However, it also applies to anything that happens while time traveling that should logically make your original time travel trip impossible or unnecessary.
22nd Jun '16 10:24:14 AM Willbyr
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[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/grandfather_paradox.jpg]]



A type of TemporalParadox. The name comes from the most famous variation - namely "what would happen if you travelled back in time and killed your own grandfather?", but also applies to anything that happens while time travelling that should logically make your original time travel trip impossible or unnecessary.

For example, if you killed your grandfather in the past, you should [[RetGone never have been born]], and therefore you couldn't have travelled to the past to kill your grandfather. Destroyed the time machine? Okay, but how did you use said machine to travel into the past in the first place? Kill the evil overlord while he's a child? Then [[HitlersTimeTravelExemptionAct you shouldn't have any reason to travel into the past to kill him]], because he never grew up to [[DoomedHometown destroy your village]] and all.

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A type of TemporalParadox. The name comes from the most famous variation - namely "what would happen if you travelled traveled back in time and killed your own grandfather?", but also applies to anything that happens while time travelling traveling that should logically make your original time travel trip impossible or unnecessary.

For example, if you killed your grandfather in the past, you should [[RetGone never have been born]], and therefore you couldn't have travelled traveled to the past to kill your grandfather. Destroyed the time machine? Okay, but how did you use said machine to travel into the past in the first place? Kill the evil overlord while he's a child? Then [[HitlersTimeTravelExemptionAct you shouldn't have any reason to travel into the past to kill him]], because he never grew up to [[DoomedHometown destroy your village]] and all.



This paradox doesn't stop you from travelling to the future and [[InvertedTrope killing your future self and your offsprings]], however.

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This paradox doesn't stop you from travelling traveling to the future and [[InvertedTrope killing your future self and your offsprings]], offspring]], however.






* [[MadScientist Brainstorm]] built a time machine in ''ComicBook/TransformersMoreThanMeetsTheEye'' that was specifically constructed to be immune to this paradox [[spoiler: so that he could go into the past and kill Megatron before the Great War started]].

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* [[MadScientist Brainstorm]] built a time machine in ''ComicBook/TransformersMoreThanMeetsTheEye'' that was specifically constructed to be immune to this paradox [[spoiler: so [[spoiler:so that he could go into the past and kill Megatron before the Great War started]].



Blade Star then decides to confront Queen Chrysalis and expose her to the ponies earlier than in canon, severely injuring her in the process. The paradox this causes is so huge that Discord has to come in and fix the mess, stating that this was simply way too much chaos for one being, [[EvenEvilHasStandards even by his standards.]]

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Blade Star then decides to confront Queen Chrysalis and expose her to the ponies earlier than in canon, severely injuring her in the process. The paradox this causes is so huge that Discord has to come in and fix the mess, stating that this was simply way too much chaos for one being, [[EvenEvilHasStandards even by his standards.]]standards]].



* Inverted in two separate ways in Literature/{{Rant}}: [[spoiler: Traveling back in time to kill your parents will cause you to be outside of time, and therefore immortal (in-universe this is known as "severing ties"). Going back and impregnating your mother, or a direct matriarch of your family (grandmother, great-grandmother) will result in gaining heightened faculties (this is known in-universe as "stoking". Combo points for [[{{Squick}} impregnating each one down the line until you are born]].)]]

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* Inverted in two separate ways in Literature/{{Rant}}: [[spoiler: Traveling ''Literature/{{Rant}}'': [[spoiler:Traveling back in time to kill your parents will cause you to be outside of time, and therefore immortal (in-universe this is known as "severing ties"). Going back and impregnating your mother, or a direct matriarch of your family (grandmother, great-grandmother) will result in gaining heightened faculties (this is known in-universe as "stoking". Combo points for [[{{Squick}} impregnating each one down the line until you are born]].)]]



* [[DiscussedTrope Discussed]] in Creator/StephenKing's ''Literature/ElevenTwentyTwoSixtyThree''.

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* [[DiscussedTrope Discussed]] {{Discussed|Trope}} in Creator/StephenKing's ''Literature/ElevenTwentyTwoSixtyThree''.



** Though he initially hand-waves, King does answer the question implicitly: Nothing would happen to the traveler. People who go through the portal are 'out' of the timestream and thus not eliminated as a result of their actions. [[spoiler: Although progressively worse things happen to the traveler the more the traveler tries to make a major change to the timeline, and although the traveler will return to the exact moment of departure, the effects of time spent in the past--such as aging--are not reversed.]]
* Discussed and inverted in ''[[Literature/LocksmithsCloset Locksmith's Closet]]''. When Lock and Gary travel into the future and find it uninhabited, Gary remarks that "at least we don't have to worry about our grandkids coming along and shooting us just to see what'll happen."

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** Though he initially hand-waves, King does answer the question implicitly: Nothing would happen to the traveler. People who go through the portal are 'out' of the timestream and thus not eliminated as a result of their actions. [[spoiler: Although [[spoiler:Although progressively worse things happen to the traveler the more the traveler tries to make a major change to the timeline, and although the traveler will return to the exact moment of departure, the effects of time spent in the past--such as aging--are not reversed.]]
* Discussed and inverted in ''[[Literature/LocksmithsCloset Locksmith's Closet]]''.''Literature/LocksmithsCloset''. When Lock and Gary travel into the future and find it uninhabited, Gary remarks that "at least we don't have to worry about our grandkids coming along and shooting us just to see what'll happen."



* Discussed in ''Literature/TheDresdenFiles'' novel ''Literature/ColdDays'', when Harry asks Vadderung what would happen if he were to travel back in time and attempt to kill his grandfather. The answer is that [[BadassGrandpa Harry's grandfather would beat him senseless]], because [[spoiler: Harry's grandfather is Ebenezer [=McCoy=], Harry's mentor and the White Council's Blackstaff.]]
** Eventually he gives a more serious answer, it would destroy the current timeline and create two new ones, one where he failed and one where he succeeded.
* Parodied in one of Brian Aldiss's "Three Enigma" stories. A time traveller goes back in time and falls in love with his grandmother, causing his grandfather to commit suicide. "I can see this is going to be awkward," says the time traveller as he fades out of existence.

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* Discussed in ''Literature/TheDresdenFiles'' novel ''Literature/ColdDays'', when Harry asks Vadderung what would happen if he were to travel back in time and attempt to kill his grandfather. The answer is that [[BadassGrandpa Harry's grandfather would beat him senseless]], because [[spoiler: Harry's grandfather is Ebenezer [=McCoy=], Harry's mentor and the White Council's Blackstaff.]]
**
]] Eventually he gives a more serious answer, it would destroy the current timeline and create two new ones, one where he failed and one where he succeeded.
* Parodied in one of Brian Aldiss's "Three Enigma" stories. A time traveller traveler goes back in time and falls in love with his grandmother, causing his grandfather to commit suicide. "I can see this is going to be awkward," says the time traveller traveler as he fades out of existence.



* The ''TabletopGame/{{Warhammer 40000}}'' supplementary material has an Ork warboss who traveled back in time a day and proceeded to kill his past self so he could have two copies of his favorite gun.

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* The ''TabletopGame/{{Warhammer 40000}}'' supplementary material has an Ork warboss who traveled back in time a day and proceeded to kill his past self so he could have two copies of his favorite gun. Unfortunately, this so confused the Orks under his command that the WAAAGH! he was leading fell apart.



* [[Series/{{Mythbusters}} Adam and Jamie]] decide to put this trope and the MyOwnGrandpa trope to the test when they went back in time in ''IrregularWebcomic''. They botch it up when they accidentally swapped grandmothers, making ''each other'' their grandfathers (Adam is Jamie's grandfather, Jamie is Adam's). Incidentally though, this does make them their own great-great-grandfathers, proving that this trope and the MyOwnGrandpa trope is possible. Myth confirmed!

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* [[Series/{{Mythbusters}} Adam and Jamie]] decide to put this trope and the MyOwnGrandpa trope to the test when they went back in time in ''IrregularWebcomic''.''Webcomic/IrregularWebcomic''. They botch it up when they accidentally swapped grandmothers, making ''each other'' their grandfathers (Adam is Jamie's grandfather, Jamie is Adam's). Incidentally though, this does make them their own great-great-grandfathers, proving that this trope and the MyOwnGrandpa trope is possible. Myth confirmed!



* While this paradox is almost always associated with time travel, it is actually also a [[Analysis/FasterThanLightTravel consequence of faster than light travel or communications.]] The problem is that when a signal travels faster than light, it is possible for the signal to travel faster the action that caused the signal to be sent. An example would be telling someone to not fire a bullet that you see would hit you. How could you tell them to not fire the bullet if your telling them would prevent you from seeing it and thus telling them?

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* While this paradox is almost always associated with time travel, it is actually also a [[Analysis/FasterThanLightTravel consequence of faster than light travel or communications.]] communications]]. The problem is that when a signal travels faster than light, it is possible for the signal to travel faster than the action that caused the signal to be sent. An example would be telling someone to not fire a bullet that you see would hit you. How could you tell them to not fire the bullet if your telling them would prevent you from seeing it and thus telling them?
21st May '16 2:21:12 PM Doug86
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* [[IDWPublishing IDW]]'s ''ComicBook/BackToTheFuture'' establishes 1985-A (the hellish 1985 from ''Film/BackToTheFuturePartII'') as an impending grandfather paradox, as Doc Brown finds out that his alternate universe double [[spoiler:has been lobotomized]]. If Doc Brown never builds the time machine, then Old Biff can't give the almanac to his 1955 self; and if he doesn't give the almanac to himself, then 1985-A can't happen...

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* [[IDWPublishing [[Creator/IDWPublishing IDW]]'s ''ComicBook/BackToTheFuture'' establishes 1985-A (the hellish 1985 from ''Film/BackToTheFuturePartII'') as an impending grandfather paradox, as Doc Brown finds out that his alternate universe double [[spoiler:has been lobotomized]]. If Doc Brown never builds the time machine, then Old Biff can't give the almanac to his 1955 self; and if he doesn't give the almanac to himself, then 1985-A can't happen...
6th May '16 4:27:01 PM eroock
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[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/grandfather_paradox.jpg]]
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6th May '16 4:26:15 PM eroock
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[[quoteright:350:http://static.tvtropes.org/pmwiki/pub/images/grandfather_paradox.jpg]]
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27th Feb '16 2:51:15 PM DynamiteXI
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Added DiffLines:

* [[IDWPublishing IDW]]'s ''ComicBook/BackToTheFuture'' establishes 1985-A (the hellish 1985 from ''Film/BackToTheFuturePartII'') as an impending grandfather paradox, as Doc Brown finds out that his alternate universe double [[spoiler:has been lobotomized]]. If Doc Brown never builds the time machine, then Old Biff can't give the almanac to his 1955 self; and if he doesn't give the almanac to himself, then 1985-A can't happen...
27th Jan '16 9:47:11 AM ChronoLegion
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Added DiffLines:

* In ''VideoGame/TheJourneymanProject'' series, it's fairly easy to change something in the past, but, since the DelayedRippleEffect travels only forward in time, it will not affect the time traveler himself, provided he doesn't return before the wave reaches his point of departure. This is also how, in the first game, the [[TimePolice Temporal Security Annex]] keeps a copy of the world history from being overwritten by a time wave. A disk with the copy is kept in the distant past. If a ripple is detected ([[HandWave somehow]]), a time agent it sent back to that period to retrieve the copy, which can be then compared in the present to the history in the Annex's data banks to figure out the point of divergence. This is {{Hand Wave}}d in later games, and the TSA simply knows where and when the change took place without the copy, but an agent still needs to be sent back before the wave hits to avoid him or her becoming part of the new timeline.
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