Celestial colour (one)

We had seen a lot of scenery pictures in Qinghai-Tibet Platean arsis, most moment, na Zhan of our deep feeling's blue sky and white Yun Duo, still have the rosy clouds of various beauty and rainbow. But occasionally we still can have a lot of doubt: When weather fine is good, the sky that we see is azure normally, but downy sky is met La Defa is dark, even La Zhong band is black, is what didn't the cloud also see on Campagna so white... why can you be such? Why to go up in the prairie, the rainbow that we often can see beauty and gorgeous rays of morning or evening sunshine...

Sky why so blue?

In the sky all sorts of multicolored the colour of much appearance is to be below different weather condition, sunshine causes in the scattering in aerosphere. The color of the sky that we see, it is the color of the light of aerosphere scattering actually. If the sky is very pure, without the scattering action of atmosphere and other particle, so, besides can see the sun, moon, tiny spot, whole sky setting will be a darkness. Because " day " itself does not have color, blue is not " day " color, however atmosphere element scattering the cause of the blue light in sun's rays.

Earthly surface is surrounded by atmosphere, after sun's rays enters atmosphere, air element and particle (dust, water, ice crystal) meeting general sun's rays to all around scattering. Sun's rays is by red, orange, yellow, green, blue, indigo, violet 7 kinds of smooth composition, grow with glow wave the longest, violet smooth wavelengh is the shortest. The shade transmission sex such as the glow with longer wavelengh is the biggest, can shoot through the particle in atmosphere directly to the ground. And wavelengh is shorter blue, indigo, violet wait for shade, be dropped very easily by the atomic scattering in atmosphere. In shortwave wave band, blue light energy is the biggest, the light-wave that scattering comes out is most also, because this sky that we see presents a sky blue normally.

After cold air of autumn winter season passes, we are in density in very big cold air group, the day appears special azure blue. The air on high mountain and highland is rare, blue wear off of the sky, colour of sky is sent dark. For example, on the photograph of a lot of color that pat in Mount Everest, the day presents blue black, even black, it is this truth. If be in 10 thousand meters altitude flight, the glazing through plane cockpit is looked up at to zenith, can see head apical sky often is dark blue.