Why sky is blue ?

Question

Could someone give me scientific explanation why sky is blue.

Answer 1

The sun's rays hit the Earth's atmosphere, where the light is scattered by nitrogen and oxygen molecules in the air. The blue wavelength of this light is affected more than the red and green wavelengths, causing the surrounding air to appear blue. At sunset, the sun's light passes farther through the atmosphere, deflecting and decreasing the blue in the air. Scattering by dust particles and pollution in the air causes the sunset to appear red.

Answer 2

This question has been asked over 5000 times, and I've prepared a simple answer, without too much science:

The correct answer is that the blue light is scattered by the air molecules in the atmosphere (referred to as Rayleigh scattering). The blue wavelength is scattered more, because the scatteing effect increases with the inverse of the fourth power of the incident wavelength.

OK, but I've known science graduates who don't understand what this means.
Here's my attempt at an answer without too much physics:

I think most people know that sunlight is made up of light of several different wavelengths, and can be split up into the colours of the rainbow. Blue light has the shorter wavelength, and red the longest wavelength.

When sunlight hits the molecules in the atmosphere, the light strikes the molecules and is absorbed. The molecules vibrate and and give off, or 're-emit' the light. Because the molecules vibrate in all directions, the light is emitted in all directions (called 'scattering'). The molecules in the air are much smaller than the wavelength of visible light, but because the blue wavelength is shorter and more energetic, it reacts much more with the air molecules than the red and yellow wavelengths; which tend to pass straight through.

Because the blue radiation is re-emitted from the air molecules in all directions, it seems to us looking from the ground that the blue light is coming from everywhere; hence the sky seems blue.

Near sunset, because of the low angle of the sunlight, we see more of the red and yellow wavelendth passing straight through, hence the colours of the setting sun.

BTW: The sky isn't blue because of a reflection of the sea; its the other way round, although the blue colour of the sea is mostly caused by the water molecules scattering the blue light, in a similar way. This effect is even stronger with ice; which results in the intense blue colour we see if we look down a crevasse in a glacier, or down a hole in the snow made by a ski stock..

For a complete, scientific explqanation, look up 'blue sky' in Wikipedia.

Answer 3

The colour of the sky as seen from the earth is due to the scattering of sunlight by the molecules of the gases in the earth's atmosphere.The amount of scattering is inversely proportional to the fourth power of the wavelength.This is known as Rayleigh's scattering law.Hence the shorter wavelengths are scattered much more than the longer wavelengths.The shorter wavelength region of the solar spectrum is blue in colour.This scattered radiation causes the sky appear blue.

Answer 4

The sun rays from space are composed of VIBGYOR (Violet Indigo Blue Green Yellow Orange Red) These colors have different wavelengths with violet having least and red maximum . The molecules of air are of the order of the wavelength of blue color .So ROYG colors pas and VIB is scattered all over the sky Here blue is most dominant and hence the sky looks blue

Answer 5

For those who think the sky is blue because it is reflecting off the oceans, probably the opposite is true. The oceans look blue because they are reflecting off the sky. The Doctor is right about why the sky looks blue.

Answer 6

Nonsense, all of it (other than, maybe, what "the doctor" said). The blueness of the sky is due to the wavelength-dependent scattering of light (called Reyleigh Scattering). It's a very complex phenomenon... but is has NOTHING to do with light reflecting off water. This also explains the redness of sunsets.

Answer 7

as we know, light is made up of several colors. as light touches the atmosphere, the blue color in the light is the only color that the atmosphere reflects and the other colors are absorbed. as blue color bounces back, we get to see the sky to be colored blue.

Answer 8

light reflecting off the water

Answer 9

It's because the ozone

Answer 10

I don't know but I like it