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Who discovered the cause of a red moon?

  1. Sep 21, 2015 #1
    The moon often glows red during a total eclipse because light from Earth's atmosphere is refracted into the Earth's umbra, and Rayleigh scattering filters out blue wavelengths. Who first came up with this idea and how? I'd love to know the history behind that insight.
     
  2. jcsd
  3. Sep 21, 2015 #2

    marcus

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    Lord Rayleigh contributed to understanding
    1. John Strutt (1871) "On the light from the sky, its polarization and colour," Philosophical Magazine, series 4, vol.41, pages 107-120, 274-279.
    2. John Strutt (1871) "On the scattering of light by small particles," Philosophical Magazine, series 4, vol. 41, pages 447-454.
    3. John Strutt (1881) "On the electromagnetic theory of light," Philosophical Magazine, series 5, vol. 12, pages 81-101.
    4. John Strutt (1899) "On the transmission of light through an atmosphere containing small particles in suspension, and on the origin of the blue of the sky," Philosophical Magazine, series 5, vol. 47, pages 375-394.
     
  4. Sep 21, 2015 #3

    marcus

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    that is a nice question, Opus. John Strut = Lord Rayleigh. As you indicate, he figured out why the sky is blue. ("Rayleigh scattering")

    Because the size of air molecules make them more effective at scattering shorter wavelengths like green and blue. So given that understanding
    it is not such a big jump to see that light that had passed thru the atmosphere and been refracted onto the eclipsed moon would be reddish.

    People already knew about refraction (e.g. by air) when Strut was working.
     
  5. Sep 22, 2015 #4
    Thanks for those references, I'll start digging into them! What I'm really looking for, though, is the first publication where someone made the explicit connection between Rayleigh scattering and eclipses. Perhaps this is as close as it gets, and there wasn't really an "aha!" publication about it, but rather behind the scenes discussions. I was just curious if any definite history about the discovery had been preserved.

    Thanks for pointing me to John Strutt's papers, though. I'm excited to read them!
     
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