Le texto fonte de Paradoxo del granpatre

[[File:Grandfather paradox billiard ball.svg|thumb|right|<u>In alto</u>: trajectoria original del bolla de biliardo.<br /><u>Al medio</u>: le bolla de biliardo emerge del futuro, e da al bolla del passato un colpo que lo devia ante entrar in le machina de exploration temporal.<br /><u>In basso</u>: le bolla de biliardo non entra in le machina temporal, lo que ingenera le paradoxo, questionante le facto que le bolla plus vetere pote emerger del passato e deviar su trajectoria.]]

Le '''paradoxo del granpatre''' es un [[paradoxo]] relative al [[viage temporal]] in que eventos incoherente occurre a causa de modificationes del passato.<ref name="lobo">{{cite web |url=https://arxiv.org/pdf/gr-qc/0206078v2.pdf |title=Time, Closed Timelike Curves and Causality |page=2 |author=Francisco Lobo |year=2002 |accessdate=2015-11-02}}</ref> Le nomine del paradoxo veni de su description habitual: un persona viagia in le passato e occide su proprie granpatre ante que su patre o matre es concipite, lo que impedi le existentia del viagiator temporal.<ref name="sagan-nova">{{cite web|url=https://www.pbs.org/wgbh/nova/time/sagan.html |title=''Carl Sagan Ponders Time Travel'' (Carl Sagan medita super le viage temporal)|work=NOVA|date=1999-12-10|publisher=[[PBS]]|accessdate=2016-05-21}}</ref> In despecto de su titulo, le paradoxo del granpatre non concerne exclusivemente le contradiction de occider su proprie granpatre ante haber essite concipite. Plus tosto, le paradoxo concerne ulle action que altera le passato,<ref name="Norman">[https://www.sfu.ca/~swartz/beyond_experience/chap08.htm|pp=226&mdash;227 "Beyond Experience: Metaphysical Theories and Philosophical Constraints"], Norman Swartz, Pressa del Universitat de Toronto, 2001.</ref> viste que un contradiction es create cata vice que le passato deveni differente de lo que illo esseva antea.<ref name="NicholasSmith">{{cite web |url=http://plato.stanford.edu/entries/time-travel/index.html#CauLoo |author=Nicholas J.J. Smith |date=2013 |title=Time Travel |work=Stanford Encyclopedia of Philosophy |accessdate=2015-11-02}}</ref>

==Prime exemplos==
Le paradoxo del granpatre esseva mentionate in litteratura a partir de 1929, e in 1931 illo esseva describite como "le argumento antique de impedir vostre nascentia per occider vostre granparentes" in un littera al magazine american de scientia-fiction ''Amazing Stories''.<ref name=":0">{{cite book|url=https://books.google.com/books?id=39KQY1FnSfkC|title=Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction|last1=Nahin|first1=Paul J.|date=1999|publisher=Springer|year=|isbn=0387985719|edition=2nd|location=New York|pages=255, 286}}</ref> Le prime historias de [[scientia-fiction]] parlante del paradoxo es le historia curte ''Ancestral Voices'' per [[Nathaniel Schachner]], publicate in 1933,<ref>{{cite book|last1=Ginn|first1=Sherry|last2=Leach|first2=Gillian I.|title=Time-Travel Television: The Past from the Present, the Future from the Past|date=2015|publisher=Rowman & Littlefield|location=London|isbn=1442255773|page=192}}</ref> e le libro 1944 ''Future Times Three'' per René Barjavel, ben que numerose altere obras appochava le subjecto in le annos 1930s e 1940s con plus o minus de detalios.<ref name=":0" />

==Variantes==
Le paradoxo del granpatre 
se refere a qualcunque cambiamento del passato,<ref name="NicholasSmith"/> e es presentate sub multe variationes. Le physico John Garrison e alteres presenta un variation del paradoxo con un circuito electronic que invia un signal trans un machina temporal commandante le circuito de extinguer se, e recipe le signal ante haber inviate lo.<ref>{{cite journal|last1=Garrison|first1=J.C.|last2=Mitchell|first2=M.W.|last3=Chiao|first3=R.Y.|last4=Bolda|first4=E.L.|title=Superluminal Signals: Causal Loop Paradoxes Revisited|journal=Physics Letters A|date=August 1998|volume=245|issue=1-2|pages=19–25|doi=10.1016/S0375-9601(98)00381-8|arxiv=quant-ph/9810031|bibcode=1998PhLA..245...19G}}</ref><ref>{{cite book|last1=Nahin|first1=Paul J.|title=Time Machine Tales|date=2016|publisher=Springer International Publishing|isbn=9783319488622|pages=335-336}}</ref> Un paradoxo equivalente es cognoscite in [[philosophia]] como le ''autoinfanticidio'': retornar in le passato e occider se mesme al stato de neonato.<ref name="horwich">{{cite book|last1=Horwich|first1=Paul|title=Asymmetries in Time: Problems in the Philosophy of Science|date=1987|publisher=MIT Press|location=Cambridge, Massachusetts|isbn=0262580888|page=116|edition=2nd}}</ref>

Un altere variante del paradoxo del granpatre es le "paradoxo de Hitler" or "paradoxo del assassinato de Hitler",<ref>{{cite web|url=https://www.bostonglobe.com/arts/books/2013/04/06/book-review-life-after-life-kate-atkinson/OL6nDqGHPFgxaUBrJgXEHL/story.html|title=Book review: Life after Life’ by Kate Atkinson|author=Eugenia Williamson|date=6 April 2013|work=The Boston Globe|accessdate=9 August 2013|quote=Cerca in Google le parolas ‘retornar in le passato e’ e le motor de recerca suggere completar con le simple directiva: ‘kill Hitler’. Le desiro de assassinar le dictator nazi es si grande que illo ha su proprie subgenere intra le fiction speculative, un tropo cognoscite como le ‘paradoxo del assassinato de Hitler’ in que un viagiator temporal retorna assatis longe in le passato pro applattar le leader — e le Secunde Guerra Mundial — in le button, typicamente con consequentias inattendite.}}</ref> un motivo relativemente frequente in scientia-fiction, ubi le protagonista retorna in le passato pro assassinar [[Adolf Hitler]] ante que ille pote instigar le [[Secunde Guerra Mundial]] e le [[Holocaust]]. In loco de necessemente impedir le realisation del viage temporal, le action elimina le ''ration'' del viage e alsi ulle cognoscentia de ille ration, lo que rende le viage initial inutile.<ref>{{cite book|last1=Brennan|first1=J.H.|title=Time Travel: A New Perspective|date=1997|publisher=Llewellyn Publications|location=Minnesota|isbn=9781567180855|page=23|edition=1st|url=https://books.google.com/books?id=UBf_HjZHUxkC|quote=A variation on the grandfather paradox . . . is the Hitler paradox. In this one you travel back in time to murder Hitler before he starts the Second World War, thus saving millions of lives. But if you murder Hitler in, say, 1938, then the Second World War will never come about and you will have no reason to travel back in time to murder Hitler!}}</ref> In ultra, le consequentias del existentia de Hitler es tanto monumental e universal que pro omne personas nascite post le guerra, il es probabile que illo ha influentiate lor nascentias de un maniera o un altere.<ref>{{cite web|last1=Inglis-Arkell|first1=Esther|title=Are we running out of time to kill Hitler via time travel?|url=http://io9.com/5932026/are-we-running-out-of-time-to-kill-hitler-via-time-travel|website=io9|accessdate=2013-08-12|date=2012-08-06|archivedate=2014-03-23|archiveurl=https://web.archive.org/web/20140323134449/http://io9.com/5932026/are-we-running-out-of-time-to-kill-hitler-via-time-travel}}</ref>

Alicunes recommenda prender in consideration le existentia potential de [[multiverso|universos parallel]] pro studiar le paradoxo. Quando le viagiator temporal occide su granpatre, in realitate illo occide un version de su granpatre de un universo parallel, e le universo original del viagiator non es modificate; on ha arguite que, viste que illo modifica le historia de un altere universo e non illo de su universo, isto non es un viage temporal "authentic".<ref>[http://plato.stanford.edu/entries/time-travel-phys "Time Travel and Modern Physics"], ''Stanford Encyclopedia of Philosophy'', Frank Arntzenius, Tim Maudlin, 2009-12-23.</ref> In altere variantes, le actiones del viagiator temporal ha nulle effecto foras de su experientia personal, como describite in le historia curte de [[Alfred Bester]] ''[[The Men Who Murdered Mohammed]]''.{{Citation needed|date=May 2018}}

==Analyse philosophic==
Mesmo sin saper si le viage temporal verso le passato es physicamente possibile, on pote usar le [[logica modal]] pro monstrar que alterar le passato resulta in un contradiction logic. Si il es necessemente ver que le passato occurreva de un certe maniera, il es tunc false e impossibile que le passato occurreva de un maniera differente. Un viagiator temporal non poterea alterar le maniera como le passato ''es'', illo solmente agerea de un maniera jam consistente con lo que ''necessemente'' occureva.<ref name="Norman"/><ref>{{cite book|last1=Dummett|first1=Michael|title=The Seas of Language|date=1996|publisher=Oxford University Press|location=Oxford|isbn=0198236212|pages=368–369|edition=New}}</ref>

Le studio del paradoxo del granpatre ha conducite alicun personas al idea que le viage temporal es paradoxe per su natura mesme e ergo logicamente impossibile. Per exemplo, le philosopho [[Bradley Dowden]] faceva iste typo de argumento in le manual ''Rationamento Logic'', affirmante que le facto que crear un contradiction es possibile impedi le viage temporal verso 
le passato completemente. Totevia, alicun philosophos e scientistas pensa que illo non necessemente es logicamente impossibile a condition que il existe nulle possibilitate de modificar le passato,<ref name="NicholasSmith"/> assi que isto es suggerite, per exemplo, per le [[principio de autoconsistentia de Novikov]]. Bradley Dowden, ille mesme, reconsiderava iste option post haber essite convincite per le philosopho Norman Swartz.<ref name="Swartz">{{cite web|url=https://www.sfu.ca/~swartz/time_travel1.htm |title=Time Travel - Visiting the Past|author=Norman Swartz|year=1993|publisher=SFU.ca |date= |accessdate=2016-04-21}}</ref>

===Physica theoric===
Le studio del possibilitate de viagiar verso le passato in un universo hypothetic, describite per un [[universo de Gödel]], conduceva le famose logicista [[Kurt Gödel]] a affirmar que le tempore mesme poterea esser un sorta de illusion.<ref name="Yourgrau">{{cite book|last1=Yourgrau|first1=Palle|title=A World Without Time: The Forgotten Legacy of Godel and Einstein|date=4 March 2009|publisher=Basic Books|location=New York|isbn=9780786737000|page=134|url=https://books.google.com/books?id=GtY907BlhxYC&pg=PA134&lpg=PA134&focus=viewport&vq=%22time+itself+-+hence+speed+and+motion+-+is+but+an+illusion%22&dq=2005+A+World+Without+Time:+The+Forgotten+Legacy+of+G%C3%B6del+and+Einstein#v=onepage|accessdate=December 18, 2017}}</ref><ref name="holt">{{cite news|last=Holt|first=Jim|title=Time Bandits|date=2005-02-21|publisher=The New Yorker|url=https://www.newyorker.com/magazine/2005/02/28/time-bandits-2|accessdate=2017-12-13}}</ref>

==Buclas causal==
Un viage temporal que non crea un paradoxo del granpatre crea in su loco un bucla causal. In le principio de autoconsistentia de Novikov, un proposition es exprimite secundo que viagiar a traverso del tempore poterea esser possibile sin ingenerar paradoxos. Conforme a iste hypothese, le phenomenos physic eveniente intra o cerca omne [[curva spatiotemporal claudite de typo tempore]] (machinas temporal) pote solmente esser consistente con le leges universal del physica, e assi solo eventos autoconsistente pote occurrer. Omne cosa facite per un viagiator temporal in le passato debe haber essite includite in le historia depost le initio, e le viagiator temporal non pote jammais facer un cosa que impedi su viage in le passato proque isto esserea un inconsistentia. Novikov e alteres usa un exemplo fornite per le physico [[Joseph Polchinski]] pro le paradoxo del granpatre: un bolla de biliardo se dirige verso un machina temporal; le bolla del passato emerge del machina e percute le bolla del presente, de sorta que le bolla del presente non entra in le machina. Novikov e altere recercatores monstrava como solver iste systema a fin de evitar le paradoxo del granpatre, ben que isto ingenera un bucla causal.<ref>{{cite journal|last=Lossev|first=Andrei|last2=Novikov|first2=Igor|date=15 May 1992|title=The Jinn of the time machine: non-trivial self-consistent solutions|journal=Class. Quantum Gravity|volume=9|pages=2309–2321|url=http://thelifeofpsi.com/wp-content/uploads/2015/01/Lossev-Novikov-1992.pdf|doi=10.1088/0264-9381/9/10/014|bibcode=1992CQGra...9.2309L|accessdate=16 November 2015}} {{Webarchive|url=https://web.archive.org/web/20151117014658/http://thelifeofpsi.com/wp-content/uploads/2015/01/Lossev-Novikov-1992.pdf |date=17 November 2015 }}</ref><ref name="Thorne">{{cite book|last1=Thorne|first1=Kip S.|title=[[Black Holes and Time Warps|Black Holes & Time Warps: Einstein's Outrageous Legacy]]|date=1995|publisher=W.W. Norton|location=New York|isbn=0393312763}}</ref> Alicun physicos suggere que le buclas causal existe solmente al scala quantic, de un maniera similar al conjectura de protection del chronologia proponite per [[Stephen Hawking]], lo que significa que historias habente loco super scalas plus grande non se repete infinitemente.<ref name="Thorne" /> Un altere conjectura, le [[hypothese de censura cosmic]], suggere que cata curva claudite de typo tempore transversa un [[horizonte de eventos]], lo que impedi le observation de tal buclas causal.<ref>{{cite journal|last1=Visser|first1=Matt|title=Traversable wormholes: The Roman ring|journal=Physical Review D|date=15 April 1997|volume=55|issue=8|pages=5212–5214|doi=10.1103/PhysRevD.55.5212|arxiv=gr-qc/9702043|bibcode=1997PhRvD..55.5212V}}</ref>

Seth Lloyd e altere recercatores proponeva un version expandite del principio de Novikov, conforme a que eventos probabile es distorquite pro impedir le occurrentia de paradoxos. Consequentias devenirea de plus in plus estranie a mesura que on se prepara a perpetrar un acto interdicite, proque le universo debe favorir le eventos improbabile pro impedir illos impossibile.<ref>{{cite web|last1=Sanders|first1=Laura|title=Physicists Tame Time Travel by Forbidding You to Kill Your Grandfather|url=https://www.wired.com/2010/07/time-travel-2/|website=WIRED|accessdate=2017-01-02|date=2010-07-20|quote=But this dictum against paradoxical events causes possible unlikely events to happen more frequently. 'If you make a slight change in the initial conditions, the paradoxical situation won’t happen. That looks like a good thing, but what it means is that if you’re very near the paradoxical condition, then slight differences will be extremely amplified,' says Charles Bennett of IBM’s Watson Research Center in Yorktown Heights, New York.}}</ref>

===Physica quantic===
Le physico [[David Deutsch]] ha arguite que le computation quantic con un retardo negative&mdash;le viage temporal in retro&mdash;produce solmente solutiones consistente con illos mesme, e le region que infringe le chronologia impone restrictiones non evidente per rationamento classic.<ref name="Deutsch">{{cite journal|last1=Deutsch|first1=David|authorlink=David Deutsch|title=Quantum mechanics near closed timelike lines|journal=Physical Review D|date=15 November 1991|volume=44|issue=10|pages=3197–3217|doi=10.1103/PhysRevD.44.3197|bibcode=1991PhRvD..44.3197D}}</ref> In 2014, alicun recercatores publicava un simulation que validava le modello de Deutsch con photones.<ref name="Ringbauer">{{cite journal|last1=Ringbauer|first1=Martin|last2=Broome|first2=Matthew A.|last3=Myers|first3=Casey R.|last4=White|first4=Andrew G.|last5=Ralph|first5=Timothy C.|title=Experimental simulation of closed timelike curves|journal=Nature Communications|date=2014-06-19|volume=5|page=4145|doi=10.1038/ncomms5145|pmid=24942489|bibcode=2014NatCo...5E4145R|arxiv=1501.05014}}</ref> Deutsch usa le termino "multiple universos" in su papiro con le intention de exprimer le phenomenos quantic, mais ille nota que iste terminologia es insatisfactori. Alteres ha interpretate isto como significante que le "viage temporal deutschian" implica le existentia de universos multiple a fin de solver le paradoxo del granpatre.<ref name="Billings">{{cite news|author1=Lee Billings|title=Time Travel Simulation Resolves 'Grandfather Paradox'|url=http://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox/|accessdate=24 September 2014|agency=Scientific American|date=2 Sep 2014}}</ref>
Il esseva tamen demonstrate in un articulo per Tolksdorf e Verch que le condition de puncto fixate del curva claudite de typo tempore de Deutsch pote esser satisfacite gratias al technica de precision arbitrari in qualcunque systema quantic describite secundo le [[theoria quantic del campos]] super le spatios-tempores ubi tal curvas es excludite, lo que permitte de dubitar super le possibilitate que le condition de Deutsch es o non vermente characteristic del processos quantic qui imita le curvas claudite de typo tempore in le senso del [[relativitate general]].<ref>{{cite journal
| last1        = Tolksdorf
| first1       = Juergen
| authorlink1  = 
| last2        = Verch
| first2       = Rainer
| authorlink2  = 
|date=2018
| title        = Quantum physics, fields and closed timelike curves: The D-CTC condition in quantum field theory
| journal      = Communications in Mathematical Physics
| volume       = 357
| issue        = 1
| series       = 
| pages        = 319-351
| arxiv        = 1609.01496
| bibcode      =2018CMaPh.357..319T 
| doi          =  10.1007/s00220-017-2943-5
}}</ref> Daniel Greenberger e [[Karl Svozil]] suggereva que in le modello de viage temporal fornite per le [[mechanica quantic|theoria quantic]], le passato debe esser autoconsistente.<ref name="greenberger">{{cite book|doi=10.1007/3-540-26669-0_4|title=Quo Vadis Quantum Mechanics?|year=2005|arxiv=quant-ph/0506027|bibcode=2005qvqm.book...63G|chapter=Quantum Theory Looks at Time Travel|series=The Frontiers Collection|last1=Greenberger|first1=Daniel M.|last2=Svozil|first2=Karl|isbn=3-540-22188-3|page=63}}</ref><ref>{{cite news|last=Kettlewell|first=Julianna|url=http://news.bbc.co.uk/2/hi/4097258.stm|title=New model 'permits time travel'|publisher=BBC News|date=June 17, 2005|accessdate=2017-04-26}}</ref>

==Vide etiam==
*[[paradoxo del predestination]]
*[[catto de Schrödinger]]
*[[paradoxo temporal]]
*[[bucla temporal]]
*[[viage temporal in fiction]]

==Referentias==
{{en}}
{{Reflist}}

{{Traduction|en|Grandfather paradox}}
[[Categoria:Paradoxos]]
[[Categoria:Mechanica quantic]]