Why is the sky blue?

Question

Why not green or any other colour? Is it something to do with reflecting the rays of the sun or what? A web link would be useful!!!

Answer 1

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.

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.

Because of the strong wavelength dependence (inverse fourth power) of light scattering according to Raleigh's Law, one would expect that the sky would appear more violet than blue, the former having a shorter wavelength than the latter. There is a simple physiological explanation for this apparent conundrum. Simply put, the human eye cannot detect violet light in presence of light with longer wavelengths. There is a reason for this. It turns out that the human eye's high resolution color-detection system is made of proteins and chromophores (which together make up photoreceptor cells or "Cone" structures in the eye's fovea) that are sensitive to different wavelengths in the visible spectrum (400 nm–700 nm). In fact, there are three major protein-chromophore sensors that have peak sensitivities to yellowish-green (564 nm), bluish-green (534 nm), and blue-violet (420 nm) light. The brain uses the different responses of these chromophores to interpret the spectrum of the light that reaches the retina.

When one experimentally plots the sensitivity curves for the three color sensors (identified here as long (L), middle (M), and short (S) wavelength), three roughly "bell-curve" distributions are seen to overlap one another and cover the visible spectrum. We depend on this overlap for color sensing to detect the entire spectrum of visible light. For example, monochromatic violet light at 400 nm mostly stimulates the S receptors, but also slightly stimulates the L and M receptors, with the L receptor having the stronger response. This combination of stimuli is interpreted by the brain as violet. Monochromatic blue light, on the other hand, stimulates the M receptor more than the L receptor. Skylight is not monochromatic; it contains a mixture of light covering much of the spectrum. The combination of strong violet light with weaker blue and even weaker green and yellow strongly stimulates the S receptor, and stimulates the M receptor more than the L receptor. As a result, this mixture of wavelengths is perceived by the brain as blue rather than violet.

Answer 2

Light coming from the sun is what's called "white light" White light contains all the colors of the rainbow. When it enters Earth's atmosphere this light is separated into its individual colors by chemical elements in the atmosphere and scattered across the sky. Nitrogen is the most abundant element in our atmosphere, and that element scatters the color blue across our sky more than the other colors. In space, there is no atmosphere to separate colors from the white light and space looks black.

Answer 3

The Sky
By John Wayne

The sky is blue
The grass is green
So get off yer butt
and join the Marines

Answer 4

Because blue is my favorite color! Its nice and soothing too, don't you think? Green is ok, but it wouldn't bring out the color of the leaves or my eyes, and red is an angry color. Purple and pink skies would make people think I'm gay, and permanent gray or tan are just terrible feng shuei anywhere. Black is a negative color and would look kind of post-modern if it stayed that way when the sun was up.

Answer 5

Go to yahoo and type:

Why is the sky blue?

and you will get about 11 million pages in about 0.12 seconds.

Answer 6

SKY IS NOT BLUE!
sky colour looks blue by viewing from earth but its colour is black when you look from space.its colour looks blue from earth because of reflection of light.you know that blue rays have more wavelength and turns to earth more than other coloured rays and so we look blue colour.