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Anh Vo

Ritsumeikan University APU

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Need explanation for Feynman's statement

Someone with great patience can help me explain the statement mentioned in Sean Carroll's talk with great details. I managed to follow its logic but got stuck halfway.

Feynman says, "From the hypothesis that the world is a fluctuation, all the predictions are that, if we look at a part of the world we've never seen before, we will find it mixed up, and not like the piece we've just looked at (high entropy). If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it. We therefore conclude the universe is not a fluctuation."

The thing is that I think I completely understand everything in the talk but this very statement. I think Feynman didn't care about writing comprehensible sentences for dummies like me. Therefore, I do dare to rephrase his statement this way and want to ask you if I have done it right:

"If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it. However, in fact, we do see parts of the world we've never seen before every new second along the arrow of time with entropy increasing definitively. We therefore conclude the universe is not a fluctuation."

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    Aug 19 2011: Feynman discusses the idea of order in the universe arising from a fluctuation (in an otherwise unordered universe) in his famous "Ratchet and Pawl" lecture, which can be found in "The Feynman Lectures on Physics," Volume I, chapter 46. I would recommend reading the entire chapter, for context, but pay particular attention to Section 46-5, "Order and entropy."

    Mike Gottlieb
    Editor, The Feynman Lectures on Physics
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      Anh Vo

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      Aug 21 2011: The thing is that I think I completely understand everything in the talk but this very statement. I think Feynman didn't care about writing comprehensible sentences for dummies like me. Therefore, I do dare to rephrase his statement this way and want to ask you if I have done it right:

      "If our order were due to a fluctuation, we would not expect order anywhere but where we have just noticed it. However, in fact, we do see parts of the world we've never seen before every new second along the arrow of time with entropy increasing definitively. We therefore conclude the universe is not a fluctuation."
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        Aug 22 2011: The first sentence seems to me a more or less correct rephrasing (though not as detailed as the equivalent part of Feynman's statement). However, what follows, about the arrow of time and entropy increasing, has, so far as I can tell, nothing directly to do with what Feynman is saying in the quotation for which you seek clarification.
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    Aug 20 2011: He's attempting to disprove a popular notion that the universe could be filled with wave-functions, or be a wave-function.

    This theory arose from the results of the "double-slit" experiment that proves the strangeness of quantum mechanics. In the famous "Copenhagen interpretation" random natural processes that have random outcomes would have multiple outcomes until they were observed by someone. Feynman argues that this should inevitably caused us to witness very strange things as witnessed in the double-slit experiment.

    He has a point. If nature was a probability, we would notice the strange things caused by the collapse of large wave-functions & we would notice some occasional fluctuations...

    It would be fun to debate whether or not fluctuations would take a recognizable form. Even if we were to observe infinite space for an infinite amount of time, I just somehow doubt that we would ever see an apple pie pop into existence. It's just hard to believe...

    Double-slit experiment:
    http://youtu.be/DfPeprQ7oGc
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    Aug 19 2011: yeah, i'd like to know that too. at a glimpse, it seems totally bogus to me.