Why is the sky blue?

Question

WHY?!!!

Answer 1

Light from the sun is made up of a spectrum of colors. The longest wave lengths of light are on the red end of the spectrum and the shortest wave lengths are on the blue end of the spectrum. Oxygen and nitrogen atoms in the air scattered more of the shorter wave length which hit the atmosphere.

There is also a red & blue shift of the spectrum that has to do with sun rise & set. But you did not ask that.

Answer 2

The earth has a gasseous atmosphere mostly made up of Nitrogen (78%). Light, mostly from the sun, enters the atmosphere where the longer wavelengths (green yellow orange and red easily pass through. The shorter wave lengths, especially blue are scattered by the nitrogen molecules. Hence whenever you look to the sky you see these scattered blue wave-lengths and the sky appears blue. Dust and water vapor tend to scatter longer wave lengths; That's why sunsets in dusty places like Arizona are so red.

Answer 3

The sky is blue due to an atmospheric effect called Rayleigh scattering - certainly not because its reflecting the ocean which people sometimes say! Rayleigh scattering involves the scattering of light by molecules smaller than the wavelength of light. It has a smaller effect on colours with longer wavelengths and that is why the sky is blue - and also in fact why the sun is yellow - if you added up all the blue tint in the sky and focused it in the area of the sun you would get its actual colour of bright white, which is what you’d see out in space.

Physicists used to say that Rayleigh diffraction was responsible for the reddish tint in sunrise and sunset because the light had to travel through more atmosphere to reach us however this is currently disputed and there is another optical theorem at work called 'Lorenz-Mie theory'.

http://en.wikipedia.org/wiki/Diffuse_sky_radiation
http://science.howstuffworks.com/question39.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html
http://math.ucr.edu/home/baez/physics/General/BlueSky/blue_sky.html
http://www.exo.net/~pauld/physics/why_is_sky_blue.html
http://www.sciencemadesimple.com/sky_blue.html

Kind regards.