Seriously, why is the sky blue?

Question

Seriously, why is the sky blue?

Answer 1

I like these answers... but they are all wrong, the reason the sky is blue is so u can see the birds better

Answer 2

The technically 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.

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 is absorbed; causing 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'). 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, or get absorbed by the atmosphere (which warms the air and gives rise to the world's climate).

Because the blue radiation is re-emitted from the air molecules in all directions, and it also gets 'bounced around' from molecule to molecules in this way, it seems to us looking from the ground that the blue light is coming from everywhere; hence the sky seems blue. And of course; we are looking upwards through several kilometres of air; so there are plenty of molecules to scatter the blue light.

Near sunset, because of the low angle of the sunlight, the blue light has already brrn scattered away, and we see more of the red and yellow wavelendth, 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. As well as reflecting the blue from the sky at the surface, sea water also scatters the blue light. 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 scattering 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. Also, don't listen to any body who tells you it is a reflection  of the ocean.

Answer 3

The sky is not blue, it just appears blue to our eyes.  The shorter wavelength light (blues and violets) get reflected and scattered by the dust and water molecules in the earth's atmosphere when light from the sun hits them, while the shorter wavelength light (yellows and reds) go through more easily.  

On the moon, where there is no atmosphere, the sky is alwyas black.  On the earth, when you look at the horizon, the sky appears less blue (and more pale) because the horizon is farther away and the blue wavelengths are more reflected and scattered so less of it gets to your eyes.

Answer 4

jus' check out topics on reflection.you'll get it!

Answer 5

It has to do with the reflection of the Earth's atmosphere and the sun.

Here's a nice and brief article I found - http://spaceplace.nasa.gov/en/kids/misrs...

Answer 6

There is a physical phenomenon called Rayleigh scattering that causes light to scatter when it passes through particles that have a diameter one-tenth that of the wavelength of the light. Sunlight is made up of all different colors of light, but because of the elements in the atmosphere the color blue is scattered much more efficiently than the other colors. The blueness you see everywhere else is all of the atoms in the atmosphere scattering blue light toward you. (Because red light, yellow light, green light and the other colors aren't scattered nearly as well, you see the sky as blue.)