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Why does the sky change color?

Basically what the title says. What mechanisms are significant and how do they contribute to make the sky blue. Also when the sky is not blue, like when the sun sets, how does it happen?

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marked as duplicate by dmckee Oct 15 '12 at 17:27

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Related to physics.stackexchange.com/questions/17 –  Waffle's Crazy Peanut Oct 15 '12 at 17:14
Hello Andreas, Please have in mind, to refer to Wikipedia before asking such questions. It's also a duplicate... Be Careful while posting next questions.... –  Waffle's Crazy Peanut Oct 15 '12 at 17:29

2 Answers 2

up vote 0 down vote accepted

Because of scattering. Blue light scatters more then other colours, because of its high frequency.

For more information read


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It's better to avoid answering duplicated questions... :-) –  Waffle's Crazy Peanut Oct 15 '12 at 17:19
I did not notice –  Prathyush Oct 15 '12 at 17:20

Sunset & Sunrise sky is reddish coz red light with longer wavelength tend to travel longer in atmosphere.

And when Sun is up in the sky Blue light is reflected mostly by the gases in atmosphere. Visible lights with longer wavelengths pass right through(actually, around).

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Hello Sparkot, Your answers are good. But, it won't be noticed 'cause it's already in this site. –  Waffle's Crazy Peanut Oct 15 '12 at 17:27
Even still, the lack of information might confuse some. The red light is seen because scattering is high and red light isn't as scattered because it has a high wavelength ($~700\text{ nm}$) and Rayleigh says that scattering is inversely proportional to the 4th power of the wavelength. –  Nick Mar 7 at 11:02

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