why is the sky blue?

Answer 1

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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.

As you look closer to the horizon, the sky appears much paler in color. To reach you, the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Less blue light reaches your eyes. The color of the sky near the horizon appears paler or white.

Answer 2

Same reason why some people have blue eyes. There is no human pigment that is blue, only "yellow/red" and "brown/black", pheomelanin and eumelanin. So where does blue come from?

The blue color of the sky and eyes is due to Rayleigh scattering. It's also the reason why the sun appears yellow. Shorter wavelengths scatter when they hit the molecules of the air, but longer wavelengths pass through. The "blue" is the scattered light of a shorter wavelength, which is why it appears everywhere. The yellow wavelength is longer, so it does not get shattered as much, so you see the sun as such. When the sun is on the horizen, more light wavelenths gets scattered, including green, so the only light that is not scattered is red, the longest wavelength of light.

Why doesn't the sky appear violet or purple, instead of blue, you might ask, since violet gets shattered more then blue.
(violet + blue = purple). The answer is the color recepters in human eyes pick up blue, but percieve the violet less so.

Answer 3

The first thing to recognize is that the sun is an extremely bright source of light -- much brighter than the moon. The second thing to recognize is that the atoms of nitrogen and oxygen in the atmosphere have an effect on the sunlight that passes through them.

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 (color) 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.

So when you look at the sky on a clear day, you can see the sun as a bright disk. 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.)

Answer 4

If you look at the blue color and think it's just blue, you're missing what it is. It's stretches of endless space that extends out into starscapes and nebulas. It's not nothing- there are gangs of dust particles and invisible gases competing in there for your attention. The theory is that color is a reflection of the light that is not absorbed by objects. All of that dust is absorbing every color in sunlight except blue, which is reflected out to your eyes. So then the question becomes why is blue the one color not absorbed by dust in the air? It has a higher and shorter frequency wavelength so it "scatters" better than the other colors.

Answer 5

The sky is blue partly because air scatters short-wavelength light in preference to longer wavelengths. Combined, these effects scatter (bend away in all directions) some short, blue light waves while allowing almost all longer, red light waves to pass straight through. When we look toward a part of the sky not near the sun, the blue color we see is blue light waves scattered down toward us from the white sunlight passing through the air overhead. Near sunrise and sunset, most of the light we see comes in nearly tangent to the Earth's surface, so that the light's path through the atmosphere is so long that much of the blue and even yellow light is scattered out, leaving the sun rays and the clouds it illuminates red.
Tyndall Effect
The first steps towards correctly explaining the colour of the sky were taken by John Tyndall in 1859. He discovered that when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more strongly than the red. This can be demonstrated by shining a beam of white light through a tank of water with a little milk or soap mixed in. From the side, the beam can be seen by the blue light it scatters; but the light seen directly from the end is reddened after it has passed through the tank. The scattered light can also be shown to be polarised using a filter of polarised light, just as the sky appears a deeper blue through polaroid sun glasses.

This is most correctly called the Tyndall effect, but it is more commonly known to physicists as Rayleigh scattering--after Lord Rayleigh, who studied it in more detail a few years later. He showed that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles. It follows that blue light is scattered more than red light by a factor of (700/400)4 ~= 10.

Dust or Molecules?
Tyndall and Rayleigh thought that the blue colour of the sky must be due to small particles of dust and droplets of water vapour in the atmosphere. Even today, people sometimes incorrectly say that this is the case. Later scientists realised that if this were true, there would be more variation of sky colour with humidity or haze conditions than was actually observed, so they supposed correctly that the molecules of oxygen and nitrogen in the air are sufficient to account for the scattering. The case was finally settled by Einstein in 1911, who calculated the detailed formula for the scattering of light from molecules; and this was found to be in agreement with experiment. He was even able to use the calculation as a further verification of Avogadro's number when compared with observation. The molecules are able to scatter light because the electromagnetic field of the light waves induces electric dipole moments in the molecules.

Why not violet?
If shorter wavelengths are scattered most strongly, then there is a puzzle as to why the sky does not appear violet, the colour with the shortest visible wavelength. The spectrum of light emission from the sun is not constant at all wavelengths, and additionally is absorbed by the high atmosphere, so there is less violet in the light. Our eyes are also less sensitive to violet. That's part of the answer; yet a rainbow shows that there remains a significant amount of visible light coloured indigo and violet beyond the blue. The rest of the answer to this puzzle lies in the way our vision works. We have three types of colour receptors, or cones, in our retina. They are called red, blue and green because they respond most strongly to light at those wavelengths. As they are stimulated in different proportions, our visual system constructs the colours we see.

Answer 6

The sky is blue due the scattering effect of light. As Sunlight travels through the earths atmosphere, it gets scattered by large no. of molecules present. It basically represents change in direction.

Rayleigh, a scientist said intensity of scattered light is inversely proprtional to fourth power of its wavelenght. Since BLUE colour HAS MINIMUM WAVELENGHT IT SCATTERS THE MOST giving sky its color. need more ?http://en.wikipedia.org/wiki/rayleigh_sc...
http://science.howstuffworks.com/questio...
http://ww2010.atmos.uiuc.edu/(gh)/guides...

Answer 7

when the dust particles in the air combines with the vapour and when it reaches our eyes it appears blue.

Answer 8

Chlorophyll it also makes Grass green