The sky is the most beautiful gradient card. The air itself is colorless, so is the wind, and all kinds of floating gaseous molecules are weak and transparent. It is because that distant star shines day and night, crossing 1.496 million kilometers, that it reaches this little star covered by clouds. When light penetrates the atmosphere, it encounters molecules and particles in the air and refracts, thus changing the levels of cold and warm colors. "Sky Color Card" series photography works "Sky Series Selected Works 20 1 1" are from new york modern art photographer Eric Kahan. He records the sunrises and sunsets all over the world, and interprets the pure colors brought by each light with minimalist photography. As he said, the color of each work is moving, so simple and incredible. Do things that cannot be changed have to be boring? We are still easily moved by the sunrise and sunset every day. It will be exactly the same without a color card. At the same time of morning or sunset, you will see different colors in different parts of the earth. If a place is particularly polluted or foggy, its sky will lose its beautiful color, leaving only a dead gray. This is because the scattering of light on particles is too dense, and all the light in visible light bands are mixed together.