is the color of the sky really blue or is it an illusion?
410647
It's really blue. Because you see it as blue.
387674
You can't see the stars during the day due to a process call Rayliegh scattering.\nBasically the sun radiates many visible colours of visible light even though it looks yellow. The blue light that the sun radiates is scattered by the atmosphere in all direction whilst other colours are unaffected. This gives the sky a blue appearance during the day. The blue sky is much brighter than the stars and thus we cannot see them.\nStrange fact: It is because the atmosphere is mostly nitrogen that the sky is blue, if the atmosphere was mostly oxygen it would be green.
159646
The blueness of the sky is caused by sunlight scattering off particles in the atmosphere.  The intesity of the scattering is a strong function of the wavelength of light, so the blue light (one end of the spectrum) is observed more than red (the other end).
929659
reflection of light\n\nDuring daylight the sky has the appearance of a deep blue surface, but this is the result of the air scattering sunlight. [1] There is no "blue object" above the earth in any normal sense, so it is hard to say what object the sky is. The sky is thus sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars. But if we then say that the sky is the entire visible universe, it would not be the same thing we see during the day.
117362
One meaning to this is that you did not check the archive of previously asked questions before you posted your question about the sky's color. This has been asked and answered almost 400 times so far here (see link below). \n\nHowever, the reason the sky appears blue (at least most of the daylight hours) is that the atmosphere is mostly oxygen and nitrogen, which are just the right size molecules to scatter the blue light, but let the other colors pass unimpeded. \n\nSo when you take the blue away from the mostly white sunlight, you get sorta yellow sunlight. \n\nAs the sun sets, the sunlight passes through more air, and more blue is scattered away, leaving the sunlight even less blue, that is, more orange. \n\nAs the sun sets even farther, even more blue is scattered away, and the sunlight appears red.
530719
During daylight the sky has the appearance of an opaque blue surface, but this is the result of the air scattering sunlight. [1]There is no "blue object" above the earth in any normal sense, so it is hard to say what object the sky is. The sky is thus sometimes defined as the denser gaseous zone of a planet's atmosphere. At night the sky has the appearance of a black surface or region scattered with stars. But if we then say that the sky is the entire visible universe, it would not be the same thing we see during the day. The color of the sky is a result of diffuse sky radiation.\nDiffuse 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\nThe sky is blue partly because air scatters short-wavelength light in preference to longer wavelengths. Where the sunlight is nearly tangent to the Earth's surface, 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, at sunrise and sunset.
24151
Everyone else is wrong. This has nothing to do with water. The sky is blue because as the light waves pass trhough the air they collide with molecules, effectively scattering the blue wavelenghts of light. This is demonstated by the fact that the sky at lower angles appears more blue, because there is more air that the light must travel through.
274364
the sky appears blue becuase that is the color of ozone (O3), the gas that surrounds the earth.
1174306
The refraction (scattering) of light waves from the sun by our atmosphere causes the sky to appear blue.
1057175
Blue sky is cause the the defraction of blue light in the atmosphere... at night there is no light to defract....
1121858
Light infusion from the sky gives the blue appearance that most observe
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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.\n\nHowever, 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.\n\nAs 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.
810923
The sky appears blue to us on a clear day, because the atoms of nitrogen and oxygen in the atmosphere separate the suns white light into its many colours, and scatter them throughout the atmosphere.The wavelength of the blue light scatters better than the rest, predominates over the other colours in the light spectrum, and makes the sky appear blue to us.The scientific name for this phenomenon is the Tyndall effect, more commonly known as Rayleigh scattering.\n\nThis phenomenon describes the way in which light physically scatters when it passes through particles in the earths atmosphere that are 1/10th in diameter of the color of the light. The light spectrum ranges in wavelength from red to violet, and, since the wavelength of the blue light passes through the particles with greater ease than the wavelengths of the other colors of light, the sky appear blue to the naked eye.\n\nThe human eye has three types of light receptors, known as cones, located in the retina. The cones are either considered to be red, or blue, or green, based upon their strong response to light at these wavelengths. As light stimulates these receptors, our vision translates the signals into the colors we see.\n\nWhen gazing at the sky, the red cones respond to the small amounts of red light scattered, and even less strongly to the orange and yellow wavelengths. Although green cones respond to yellow, their response to scattered green and green-blue wavelengths is stronger. Finally, colors near the strongly scattered blue wavelengths stimulate the blue receptors.\n\nIn short, the skylight stimulates the red and green cones almost equally, while stimulating the blue cones more strongly. For these reasons, our vision naturally adjusts as clearly as possible to separate colors.
755768
The atmospheric conditions are affecting the refraction of light & hence it doesn't appear to be blue today.
267281
Well.........\n\nThe 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. \n\nHowever, 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.
629153
The sky is what people back in the day called what they saw above them because they didnt know what it was..\n\nnow that we know, we know that what we see as blue sky is just refraction of light, and when there is no light ( night ) we just see things out in the universe that reflect light(moon) or emit light ( stars ) \n\nso the sky doesnt really exist, what it is is gases that refract sunlight during the day, and let you see through at night
20213
Why is the sky blue? why is the grass green? some things are just unexplainable...