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Thread: why is it said....

  1. #1 why is it said.... 
    Forum Ph.D.
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    that observing an electron AFTER passing the slit, implies it travelled back in time?


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    Quote Originally Posted by curious mind View Post
    that observing an electron AFTER passing the slit, implies it travelled back in time?
    Rather, the implication is that information traveled back in time:
    https://en.wikipedia.org/wiki/Quantum_eraser
    https://en.wikipedia.org/wiki/Wheele...ice_experiment


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    Forum Ph.D.
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    ok haven't read the links yet, but observing an electron after the slit means middleing with it just as before the slit, i.e. i push you to stumble before the line or i do after.

    both will change the outcome vs not being pushed.
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    True, but the difference here is that if you meddle with it after it has passed the slit, how did it "know" to retroactively make the result?
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  6. #5  
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    it didn't, the observer did.
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    Quote Originally Posted by curious mind View Post
    that observing an electron AFTER passing the slit, implies it travelled back in time?
    I've never heard such a thing. Where did you get this idea from?

    Think of it like this; describe an experiment that would demonstrate that such an electron traveled back in time.

    I know that in particle physics they sometimes speak of antiparticles as if they were just the particles but going back in time, but only in a limited sense. After all there's no way to experimentally confirm such a thing.
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    Quagma SpeedFreek's Avatar
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    Using entangled particles, you can delay the choice (of losing the information of which slit a photon passed through, or not losing that information), until after the partner particle has been detected.

    Once you make the choice, if you chose to lose the information of which slit the partner photon passed through, the partner photon is then found to have formed part of an interference pattern.

    Look up the "Delayed Choice Quantum Eraser"
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
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    Quote Originally Posted by SpeedFreek View Post

    Look up the "Delayed Choice Quantum Eraser"
    Or, click the link in post number 2.
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    Quote Originally Posted by SpeedFreek View Post
    Using entangled particles, you can delay the choice (of losing the information of which slit a photon passed through, or not losing that information), until after the partner particle has been detected.

    Once you make the choice, if you chose to lose the information of which slit the partner photon passed through, the partner photon is then found to have formed part of an interference pattern.

    Look up the "Delayed Choice Quantum Eraser"
    Are you referring to this? http://philosophyfaculty.ucsd.edu/fa...tumEraser2.pdf

    A Common Fallacy in Quantum Mechanics: Why Delayed Choice Experiments do NOT imply Retrocausality by David Ellerman, University of California at Riverside, March 14, 2012
    Abstract -
    There is a common fallacy, here called the separation fallacy, that is involved in the inter-pretation of quantum experiments involving a certain type of separation such as the: double-slit experiments, which-way interferometer experiments, polarization analyzer experiments, Stern-Gerlach experiments, and quantum eraser experiments. It is the separation fallacy that leads not only to .awed textbook accounts of these experiments but to .awed inferences about retro-causality in the context of "delayed choice" versions of separation experiments.
    Last edited by PhyMan; May 28th, 2013 at 04:40 PM.
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    Malignant Pimple shlunka's Avatar
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    Quote Originally Posted by SpeedFreek View Post
    Using entangled particles, you can delay the choice (of losing the information of which slit a photon passed through, or not losing that information), until after the partner particle has been detected.

    Once you make the choice, if you chose to lose the information of which slit the partner photon passed through, the partner photon is then found to have formed part of an interference pattern.

    Look up the "Delayed Choice Quantum Eraser"
    Ugh, I'm still pondering over what the hell everyone is talking about. Slits, electrons, time travel? Why in the name of Lucifer's fire crotch can't we just say "magic" or "arcane wizardry" instead of supplying complicated explanations!?
    "MODERATOR NOTE : We don't entertain trolls here, not even in the trash can. Banned." -Markus Hanke
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  12. #11  
    Anti-Crank AlexG's Avatar
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    "Any sufficiently advanced technology is indistinguishable from magic." Arthur C Clarke
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
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  13. #12  
    Brassica oleracea Strange's Avatar
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    "Any sufficiently analyzed magic is indistinguishable from science." Agatha Heterodyne
    ei incumbit probatio qui dicit, non qui negat
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    Forum Bachelors Degree Kerling's Avatar
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    "No Phenomena is a phenomena, until it is an observed phenomena" (John wheeler in its original piece of the delayed choice experiment)

    In short, Copenhagen dictates that something doesn't exist, until it is observed. Hence time between observations only need to apply to general relativity rules of spacetime. And it doesn't need to travel back into time to explain it al.
    In the information age ignorance is a choice.
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  15. #14  
    Quagma SpeedFreek's Avatar
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    Quote Originally Posted by Neverfly View Post
    Quote Originally Posted by SpeedFreek View Post

    Look up the "Delayed Choice Quantum Eraser"
    Or, click the link in post number 2.
    Heh, you had a link to the "delayed choice" experiment and to the "quantum eraser" experiment. I was talking about that other experiment, the one that combines the two experiments you linked. :P
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
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  16. #15  
    Quagma SpeedFreek's Avatar
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    Quote Originally Posted by PhyMan View Post
    Quote Originally Posted by SpeedFreek View Post
    Using entangled particles, you can delay the choice (of losing the information of which slit a photon passed through, or not losing that information), until after the partner particle has been detected.

    Once you make the choice, if you chose to lose the information of which slit the partner photon passed through, the partner photon is then found to have formed part of an interference pattern.

    Look up the "Delayed Choice Quantum Eraser"
    Are you referring to this? http://philosophyfaculty.ucsd.edu/fa...tumEraser2.pdf

    A Common Fallacy in Quantum Mechanics: Why Delayed Choice Experiments do NOT imply Retrocausality by David Ellerman, University of California at Riverside, March 14, 2012
    Abstract -
    There is a common fallacy, here called the separation fallacy, that is involved in the inter-pretation of quantum experiments involving a certain type of separation such as the: double-slit experiments, which-way interferometer experiments, polarization analyzer experiments, Stern-Gerlach experiments, and quantum eraser experiments. It is the separation fallacy that leads not only to .awed textbook accounts of these experiments but to .awed inferences about retro-causality in the context of "delayed choice" versions of separation experiments.
    Yes, indeed. There is no retrocausality, and I hope I didn't imply otherwise. I just explained the mechanics of the experiment.
    "Ok, brain let's get things straight. You don't like me, and I don't like you, so let's do this so I can go back to killing you with beer." - Homer
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  17. #16  
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    Quote Originally Posted by SpeedFreek View Post
    Heh, you had a link to the "delayed choice" experiment and to the "quantum eraser" experiment. I was talking about that other experiment, the one that combines the two experiments you linked. :P
    Ohhhh...

    Picky, picky. FINE!
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