why is the sky blue?

Answer 1

Because if it was green then the sky and the ground would blend together.

Answer 2

This is a commonly asked question. and the correct answer is that the molecules in the air scatter the blue wavelength of the spectrum (known as Rayleigh scattering), allowing the other wavelengths to pass through.That is fine, but I know science graduates who still don't understand this explanation.
Here is my explanation, with a limited amount of physics involved:

I think most people know that white light is made up of a spectrum of different colours, which can be broken down with a prism (or in a rainbow), showing a range of different colours, from red to blue. Technically, the red light has the longer wavelength, and the blue the shorter wavelegth (there are other wavelengths such as infrared and ultraviolet that our eyes cannot see).

When the light passes through the atmosphere, the red and yellow wavelengths pass right through, because their wavelength is larger than the size of the air molecules, and they don't interact. However, the blue wavelength is just the right size to hit the air molecules, and they bounce off in all directions (ie, they are scattered). (To understand this, imagine you are walking through a cloud of fine mist. It might be a bit unpleasant, but the tiny mist droplets are too small to cause you to slow down, and you can pass straight through. However, if you were walking through a packed crowd of people the same size as you, you couldn't pass through without colliding with and bouncing off some of the people. An elephant however, would have no trouble passing through).

That is why, when we look up at the sky, the sky seems blue, and the blue colour seems to be coming from all directions. We are seeing that scattered blue light (closer to the sun, the blue colour is not as strong. because of the red and yellow light passing straight through). The air molecules act like a sort of filter, letting the red and yellow wavelengthe straight through, but causing the blue light to bounce around. When the light reaches us on the ground, we see the combined effect of the red and yellow wavelength light passing straight though, mixed with the blue light reaching us from the sky.

If you see a sun beam passing through a narrow space into a dark room (eg through a slit in a blind) it will look more yellow, because it lacks the scattered blue part of the spectrum.

That is not quite a scientifically accurate explanation, but is the bestI can think of, without using physics.

A similar question was aked a little while ago about why water in quarries is often blue, and the answer is similar (in this case, the scattering is caused by colloidal clay particles)

Answer 3

When every color on the ligth spectrum is mixed together, we get white light. Different objects appear as different colors because the reflect certain colors and absorb others. The sky is blue because the particles in the atmosphere absorb a majority of the other colors of the spectrum as light from the sun passes through it. The color blue is the most reflected color, and therefor the color that we see the most of. At night the sky is black because of a lack of light (ie: the opposite of white).

If the sky where blue from light reflecting off of the ocean, then it would seem to follow that the sky over a midland region should appear brownish or greenish in color, which it does not.

Answer 4

As you know, we receive light here on the Earth from the Sun. By using a prism to diffuse the "white" light, Newton showed the existence of the seven colours of the spectrum in the sun's rays. When the sun's rays pass through the atmosphere, the air scatters short wavelength light, preferring longer wavelength light. Blue is one of these lights that are scattered by the air.

Answer 5

The sky is blue because the sun's lighrays are scattered as they pass thru our atmosphere, and the blue frequencies are scattered more than any other, hence we see blue. it's called Rayleigh Scattering.

Answer 6

kevin gave an excellent answer... all the other colors of the spectrum is absorbed, except for blue in this situation.

Answer 7

because of the ozone
ozone has the chemical composition o3
we see it as blue during the day only because we have light from the sun

u ppl saying its because of the water are complete morons
the ozone is blue

Answer 8

its blue becuz of da atmoshere

Answer 9

The suns reflection from the earths waters, mainly oceans

Answer 10

To match your pretty eyes...hahah