The sky is blue and the spread over a layer of the cloud like silk screen, in a short time, show a color halo around the sun. It is like a rainbow, but no rainbow bright; Rainbow colour arrangement is in red, uv and halo contrary, is purple red. This is called the "halo", commonly known as "solar or lunar halo".
Our ancestors have long for "halo" was observed and recorded. Now "halo" guizhang away. In the western zhou dynasty was "halo" official as the weather is recorded, until 1630, while the europeans are detailed records about the "halo", later than our country for over one thousand years.Although people have long noticed the beautiful phenomenon, but scientific explanation for the cause of it, is nearly one thousand two hundred years. In 1666, Newton made a very simple but had a great influence on the later development science experiment. He made a beam of sunlight through the prism, the results appear red, orange, yellow, green, green, blue, violet seven color bar. The human realized for the first time, the sun is made up of seven different colors of light, when they move through the prism, due to difference of wavelength, the Angle of refraction that shows their true colors. This discovery, laid the foundation for "halo" of scientific explanation.
Sounding data show that the white clouds, such as silk, is made up of six cylinder shape of small ice crystals. The six-party cylinder of ice crystals like a prism, article can split the sunlight into seven colours. When there is no ice crystals with hundreds of millions of little sign by sunlight, the light is refracted by certain Angle, formed colorful halo ring.