Why is the sky blue is a q i have always wondered about?

Question

please don't answer i don't know or who cares.

Answer 1

http://www.sciencemadesimple.com/sky_blu...

Answer 2

Why is the sky blue?

Well, 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.

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.

Answer 3

Diffuse sky radiation is solar radiation reaching the Earth's surface after having been scattered from the direct solar beam by molecules or suspensoids in the atmosphere. It is also called skylight, diffuse skylight, or sky radiation and is the reason for changes in the colour of the sky. Of the total light removed from the direct solar beam by scattering in the atmosphere (approximately 25% of the incident radiation when the sun is high in the sky, depending on the amount of dust and haze in the atmosphere), about two-thirds ultimately reaches the earth as diffuse sky radiation.

The important processes in the atmosphere (Rayleigh scattering and Mie scattering) are elastic. No energy transformation results, only a change in the spatial distribution of the radiation.

The sunlit sky appears blue because air scatters short-wavelength light more than longer wavelengths. Since blue light is at the short wavelength end of the visible spectrum, it is more strongly scattered in the atmosphere than long wavelength red light. The result is that the human eye perceives blue when looking toward parts of the sky other than the sun. 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 green light is scattered out, leaving the sun rays and the clouds it illuminates red. Therefore, when looking at he sunset and sunrise, you will see the color red more then any of the other colors.

Scattering and absorption are major causes of the attenuation of radiation by the atmosphere. Scattering varies as a function of the ratio of the particle diameter to the wavelength of the radiation. When this ratio is less than about one-tenth, Rayleigh scattering occurs in which the scattering coefficient varies inversely as the fourth power of the wavelength. At larger values of the ratio of particle diameter to wavelength, the scattering varies in a complex fashion described, for spherical particles, by the Mie theory; at a ratio of the order of 10, the laws of geometric optics begin to apply.

There are three commonly detectable points of zero polarization of diffuse sky radiation (known as neutral points) lying along the vertical circle through the sun.There is essentially no direct sunlight under an overcast sky, so all light is then diffuse sky radiation. The flux of light is not very wavelength dependent because the cloud droplets are larger than the light's wavelength and scatter all colours approximately equally. The light passes through the translucent clouds in a manner similar to frosted glass. The intensity ranges (roughly) from 1/6 of direct sunlight for relatively thin clouds down to 1/1000 of direct sunlight under the extreme of thickest storm clouds.

Note that the blue of the sky is more saturated when you look further from the sun. The almost white scattering near the sun can be attributed to Mie scattering, which is not very wavelength dependent. Clouds in contrast to the blue sky appear white to achromatic gray.

The water droplets that make up the cloud are much larger than the molecules of the air and the scattering from them is almost independent of wavelength in the visible range

Rayleigh scattering refers to the scattering of light off of the molecules of the air, and can be extended to scattering from particles up to about a tenth of the wavelength of the light. It is Rayleigh scattering off the molecules of the air which gives us the blue sky.As a qualitative examination of sky brightness and the saturation of the blue sky color, measurements of the color of the sky photograph were made from a computer monitor using Adobe Illustrator's color tools. None of the data should be taken as quantitatively reliable since the original photo had been transformed several times, and the measurements were taken from a non-calibrated computer monitor. Nevertheless, it might be useful as an example of the progressions of sky color.

Answer 4

http://search.yahoo.com/search?fr=ieas&p...

Answer 5

Refraction of the sun's radiated spectrum, specifically the wavelength we see as blue.  Most of the visible wavelengths come fairly directly to us from the sun which is what you see as you look at the sun.  But blue gets bent pretty severly.

Edit: hmmm, perhaps I misremember.  This article I found shows that it's actually gas molecules re-radiating light in the blue wavelenght.  I'll dig some more for you.

Edit once again:  Looks like scattered light due to the Oxygen molecule being the same size as the blue/violet wavelength band is the answer which makes most technical sense to me, "Wherever we look towards the sky, some light is bouncing off an oxygen atom and entering our eyes, making the sky appear to be blue. " See second link.