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Asked by lakhtar to James, Jayne, Kara, Sharon on 23 Mar 2011 in Categories: General.
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Sharon Sneddon answered on 23 Mar 2011:
Hi Lakhtar,
Our atmosphere is made up of different gases, mostly nitrogen and oxygen, which are in the form of molecules. Sunlight is made up of light waves of different wavelengths, which appear to us as different colours. The wavelengths that are longer, so red, yellow and green light pass pretty much straight through the atmosphere. However, the shorter wavelengths towards the blue end of the spectrum bounce off all of the molecules in our atmosphere and we see that reflected blue light everywhere we look. When you look at the horizon the sky is usually much paler and that’s because the blue light has to pass through more atmosphere to reach your eyes and gets scattered more.
This is known as Rayleigh scattering after the British physicist Lord Rayleigh.
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Jayne Charnock answered on 23 Mar 2011:
Its all to do with light scattering. Im afraid thats as much as I knew so i did a little reserach myself….!
The blue color of the sky is due to Rayleigh scattering. As light moves through the atmosphere, most of the longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.
However, much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.
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