Why is the sky blue?

Answer 1

because god made it that way

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, The blue colour of the sea is a little more complicated, because as well as the water molecules scattering the blue light, the water absorbs more of the red and yellow wavelengths, leaving the blue part of the spectrum, as well as part of the green (which is why deep water can appear bluish-green). 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..
My thanks to varoius contributers for correcting me on some details.

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

Answer 3

Its because of the way the light reflects into our eyes.

As white light passes from the sun to our atmosphere, it comes into contact with many molecules. When it does, some components of the light are absorbed and some pass stright through. It is common for the blue to be absorbed and then re-emitted a short time later. It gets scattered in all directions, which is why when we look up, the sky looks blue.

Answer 4

A clear cloudless day-time sky is blue because molecules in the air scatter blue light from the sun more than they scatter red light. When we look towards the sun at sunset, we see red and orange colours

Answer 5

Why is it that this question is asked a dozen times a day, and many people answer it each time, but people just won't use the Search function on here first to read all the great (and accurate) answers in abundance on YA.

Answer 6

Light is refracted through the atmosphere, and blue is the easiest to pick out from all these colors.

Answer 7

Similar question which had been asked and answered more than 15 times.

Answer 8

i have answered this type of question about a bazillion times...check my profile and you will get the answer

Answer 9

6,115 hits

http://answers.yahoo.com/search/search_result;_ylt=AqgY4PfynMqxpUqhqdcW4eMDxgt.;_ylv=3?p=why+is+the+sky+blue

This question will cause me to go on a mad rampage.