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Own Grandfather

  1. Jul 16, 2011 #1
    In a slightly disturbing episode of futurama, Fry (the main character) goes back in time and through a series of disturbing events discovers he is his own grandfather.

    If you think about the situation, you can go in a perpetual loop trying to figure out the causality. He went back in time because he was born and he was born because he went back in time. In other words, he necessitated his own existence.

    I thought this was an interesting concept - where the causality is ambiguous.

    Is this situation observed in physics?
  2. jcsd
  3. Jul 16, 2011 #2


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    No. It's a cartoon.
  4. Jul 16, 2011 #3


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    Obserbed in physics? No. But people do worry about the existence of closed timelike curves in GR, often with a desire to rule them out. But so far nobody's been quite able to rule them out. Which is quite a long ways away from having observed them....
  5. Jul 16, 2011 #4


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    The science-fictional idea dates back at least as far as a 1958 story by Robert Heinlein: http://en.wikipedia.org/wiki/—All_You_Zombies—

    As pervect has noted, closed timelike curves (CTCs) are a subject that has been studied extensively in general relativity:

    A good popularization: Time Travel in Einstein's Universe: The Physical Possibilities of Travel Through Time by J. Richard Gott

    CTCs are not necessarily paradoxical:
    Friedman, Cauchy problem in spacetimes with closed timelike curves, http://authors.library.caltech.edu/3737/
    Echeverria, Billiard balls in wormhole spacetimes with closed timelike curves: Classical theory, http://authors.library.caltech.edu/6469/
  6. Jul 17, 2011 #5


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    There was also a story ca 1956 called "Z", by Charles Fontenay, which avoided closed timelike curves, achieving time-travel via pair creation. A lightning bolt hits a tree, and a man and woman emerge, apparently unharmed. As time passes the man ages normally, but the woman grows progressively younger. Eventually she becomes the same age as her son, at which point mother and son disappear in a second explosion. The punchline is that mother, father and son were all the same person, and the explosions had caused his/her/its timeline to reverse. (For some reason, traveling backwards in time turns you into a woman.)
  7. Jul 17, 2011 #6

    George Jones

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    Another good popularization:
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