Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Why isn't the sky Green?

  1. Nov 19, 2005 #1
    The sky is blue because the white light is diffused by the light particles, which scatter out the blue end of the spectrum, hense a blue sky. In the afternoon, it is often red or orange, because the light has to travel much longer through the atmosphere, scattering out the red end of the spectrum. Why then, between these two times, when the depth of the atmosphere through which the light travels increases, does our sky not change from colour to colour through the spectrum, from blue to orange? Why isn't the sky green?
  2. jcsd
  3. Nov 19, 2005 #2


    User Avatar
    Gold Member

    The way I see it is that there will always be more red light reaching you directly than any other colour of the spectrum, and likewise there will be more blue diffracted light reaching you than any other colour. One of these two will normally dominate over the other colours. If I remember my atmosphere lectures right, lower wavelengths are more prone to diffract forwards, than higher wavelenghts that scatter more evenly, so this explains the orange sky around sunset.
    Anyway, I don't know about you but I've seen some pretty nice turquoises around sunset.
  4. Nov 19, 2005 #3
    http://www.squamish.ca/PublicDownloads/DistrictPhotoLibrary/Wallpaper/GreenSunset.jpg [Broken] for instance.
    Last edited by a moderator: May 2, 2017
  5. Jun 26, 2011 #4
    There is a phenomena known as the green flash that actually occurs shortly after sunset or before sunrise, where the sky is briefly green.
  6. Jun 26, 2011 #5
  7. Jun 26, 2011 #6


    User Avatar

    Staff: Mentor

    This thread has been dead for 6 years. Congrats.
  8. Jul 2, 2011 #7


    User Avatar

    Staff: Mentor

    If the sky scatters blue light the sky scatters blue light. Period. Making the path longer won't make it scatter red. What happens at sunset is that you start seeing light fromthe other things besides just the sun and empty sky (clouds and haze), through a lot of sky. The light from everything you see near the sun at sunset is thus nearly absent blue light.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook