sky

[DOUG666STING]

why is the sky blue

[mlbt]

chemical reactions between light from the sun and the mad crazy radiation that sits between the atmosphere and space......
Just for the record, water is actually blue as well, not just reflecton from the sky. It is not, as most people will no doubt argue, transparent.

[Clanad]

The appearance of blue for the sky has a name... Rayleigh scattering after John William Strutt (Lord Rayleigh) a British physicist and mathematician of the late 1800's, who calculated a mathematical formula that demonstrated that, even in an atmosphere without smoke and dust, gas molecules like oxygen could redirect sunlight and scatter it in many directions. Sunlight is a form of visible light that contains all of the colors. When it is scattered, it is perceived by the human eye as having a specific color. When sunlight encounters gas molecules in the atmosphere, high frequency blue light is scattered out first. The most intense blues are usually seen between 10:00 a.m. and 3:00 p.m. on cloudless days, if we look at the sky about 45 degrees above the horizon with our with our backs to the Sun.

As the Sun begins to set, the sky at the horizon often appears to be red. Sunlight entering at the horizon level travels through more atmosphere than sunlight entering overhead. Most of the shorter wavelength light has been scattered out, allowing longer wavelengths of light to reach our eyes. When particles of dust provide additional opportunities for scattering, sunsets have a red glow. The brilliance is often enhanced in the sky by clouds. (With partial assistance from Teacher's Guide)

[Clanad]

...And actually, water is transparent... white sunlight contains all colors.. Water absorbs some of these colors more than others. But you need a lot of water to notice this effect - which is why water cupped in your hand has no color at all. In a large body of water though, the water molecules quickly absorb red light, but they don't absorb blue light nearly
as well. So in this case, more blue light is transmitted through the water. It's actually the same principle behind why the sky is blue. Water that appears green or dark has suspended particulates or plant material that accentuates those colors... It's for good reason the Missouri River is known as the Big Muddy...

[mibn2cweus]

. . . If I can be excused for joining in on the fun . . .

Sunlight, which illuminates the sky, consists of a broad spectrum of visible light. The colour blue is widely scattered by oxygen and nitrogen molecules in the atmosphere and redirected toward the eye from all directions while other colours follow a straighter more direct path from the sun to the eye.

More details here: Why is the Sky Blue?

[new_squizza]

coincidentally, this question was answered in metro this morning.

i'd quote the article, but i left my copy on the train!

(sorry, that's not much help at all is it?)

[CosmoK]

I have the Metro article in front of me and it says it was Irish scientist John Tyndall who discovered why the sky was blue and its called the Tyndall effect. So did he use Rayleigh's caluclations?

[CosmoK]

Just checked website above which clears up tyndall/rayleigh matter. Never mind my post above!

[Catso]

And on a slightly different tack, I once read liquid air is pale blue. Dunno whether that is true, I've never seen it.