Why Does the Sky Appear Red at Sunrise/Sunset?

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    Light Scattering
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Discussion Overview

The discussion revolves around the phenomenon of the sky appearing red during sunrise and sunset, exploring the underlying reasons for this color change compared to the blue sky observed during the day. Participants delve into concepts of light scattering, atmospheric effects, and human perception of color.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant notes that the sky appears blue due to the scattering of blue light, as described by Rayleigh's law, and questions why the sky appears red during sunrise and sunset despite the scattering of blue light.
  • Another participant explains that at lower angles, light passes through more atmosphere, resulting in increased scattering of shorter wavelengths and allowing longer wavelengths, such as red, to reach the observer's eyes.
  • A different participant suggests that the color of the sky is determined by the light that gets scattered rather than the light that directly reaches the observer, indicating that blue light is scattered during the day, making the sky appear blue.
  • One participant elaborates on the scattering process, stating that air, while transparent, still scatters light, and at longer atmospheric distances, shorter wavelengths are scattered, leading to an orange and red sky.
  • Another participant raises the question of why the sky appears blue instead of violet, despite violet being the shortest visible wavelength.
  • A later reply attributes the perception of the sky as blue rather than violet to the color receptors in human eyes, which are more sensitive to blue light.

Areas of Agreement / Disagreement

Participants express various viewpoints regarding the mechanisms of light scattering and color perception, with no consensus reached on all aspects of the discussion. Some points are clarified while others remain contested.

Contextual Notes

Participants discuss the effects of atmospheric conditions on light scattering, but the discussion does not resolve the complexities of color perception or the specific reasons behind the dominance of blue over violet in the sky's appearance.

AlchemistK
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I know that the sky appears blue because the blue light gets scattered the most due to its high frequency(according to Raleigh's law) but then during the sunset or sunrise, why does the sky appear red? Doesn't almost all of the blue light get scattered , and maybe just a small portion of red? Then why does the sky appear more red than blue?
 
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As I understood it:
Lower angle, more atmosphere to pass through, more scattering of shorter wavelengths, which in turn leaves only the longer(read: RED) wavelengths free to reach your eyes.
 
Isn't it supposed to be that the light that gets scattered forms the color of the sky rather than the light left from the sun? Because during the day,as i know it, the blue light gets scattered and the sky appears blue and the rest reaches our eyes as it is.
 
Consider the meaning of scatter :)
However transparent, air is still matter and has an effect on the light coming from the sun.
When a coherent beam hits the atmosphere, it gets scattered in all direction which means each molecule gets to "shine" with whatever color/wavelength it's diffusing.
At shorter atmospheric traveling distances shorter wavelengths are scattered and the sky shines blue, at longer distances it gets orange and red.

While we are on the subject, there is another mystery as well - why is it that the sky is blue and not violet, considering it is the shortest visible wavelength. :)
 
Oh. I know that, the problem of us not seeing the sky violet is because of the the colour recptors in our eyes, they have a tendency towards blue more than violet, hence the sky appears more of a shade of blue. Atleast this is what i read somewhere.
 

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