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michael_nielsen's profile
michael_nielsen
michael_nielsen
michael_nielsen
@michael_nielsen

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michael_nielsen

@michael_nielsen

Searching for the numinous. Co-purveyor of https://quantum.country/ 

San Francisco, CA
michaelnielsen.org
Joined July 2008

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    1. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      During a total solar eclipse, gradually changing snake-like "shadow bands" may be seen on the ground just before & after totality:pic.twitter.com/o34H8FAMbE

      1 reply 5 retweets 16 likes
    2. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      Replying to @michael_nielsen

      The origin of the bands is still somewhat controversial. The most accepted theory seems to be Codona's (1986): http://adsabs.harvard.edu/full/1986A%26A...164..415C …

      1 reply 0 retweets 2 likes
    3. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      Replying to @michael_nielsen

      The basic idea seems to be in two parts. (1) For a point light source, low-altitude turbulence will cause refraction, and so ...

      1 reply 0 retweets 0 likes
    4. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      Replying to @michael_nielsen

      differential illumination across different parts of the ground. (2) Integrating over a crescent shape we still get that differential illmn.

      1 reply 0 retweets 0 likes
    5. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      Wish I had a better understanding of (a) why the scale of the bands is centimeters; (b) why integration over a crescent preserves bands, but

      2 replies 0 retweets 1 like
    6. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      Presumably if I read the paper deeply I'd understand all that much better!

      1 reply 0 retweets 0 likes
    7. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      The comment about refraction can be put better: you can think of regions of turbulence as weird, tiny little lenses, bending light,

      1 reply 0 retweets 0 likes
    8. michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      focusing it in some areas, and causing it to be more diffuse in others.

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      michael_nielsen‏ @michael_nielsen 9 Aug 2017
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      But as to why it's in bands, I don't know. That's a surprise to me.

      8:44 PM - 9 Aug 2017
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      • Amit Patel
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        1. Rob Lewis‏ @GRobLewis 9 Aug 2017
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          Replying to @michael_nielsen

          You’re not getting it; it’s proof that everything science knows is wrong and the woo woo quantum uncertainty … something. Buy My Book!

          0 replies 0 retweets 0 likes
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        1. 1/(1 - 1/(1 - 1/(1 - Dan Piponi)))‏ @sigfpe 9 Aug 2017
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          Replying to @michael_nielsen

          I've always thought of it as a bit like Gibbs phenomenon from heating the low pass filter of the atmosphere with a Heaviside function.

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