why is the sky blue?

Answer 1

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.

Answer 2

The correct answer is that the blue light is scattered by the air molecules in the atmosphere (Rayleigh scattering, or Tyndall effect), and that the blue light is scattered more, because the scatteing varies with the inverse of the fourth power of the incident wavelength. OK, but I've known science graduates who don't understand this.

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 gets bounced around by the molecules (what actually happens is that the light strikes the molecules and is absorbed, causing the molecules to vibrate and give off, or 're-emit' the lightt; but 'bounce around' is close enough).

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 ('scattered'), 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 water molecules can also scatter the blue light, which gives the intense blue colour to ice, if we look down a crevasse in a glacier.

This is one of the most popular questions in Yahoo, and has been asked over 400 times.

Answer 3

Because the sky is full of water molecules and the sun rays light them up giving it a blue color.

Answer 4

because of the way the sun rays and light rays reflect of the earths surface it makes the sky blue...blue is the most dominant color.