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Ask Kildor anything ~(> _ >)~

Why is the sky blue?
The atmosphere is the mixture of gas molecules and other materials surrounding the earth. It is made mostly of the gases nitrogen (78%), and oxygen (21%). Argon gas and water (in the form of vapor, droplets and ice crystals) are the next most common things. There are also small amounts of other gases, plus many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans. 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. However, 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. As 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.
 
Why is grass green
Like many plants, most species of grass produce a bright pigment called chlorophyll. Chorophyll absorbs blue light (high energy, short wavelengths) and red light (low energy, longer wavelengths) well, but mostly reflects green light, which accounts for your lawn's color. But chlorophyll isn't just for eye candy. It also figures importantly in the process of photosynthesis, by which plants convert an inorganic material (light) into a useable, organic one (sugar). Chlorophyll molecules absorb quanta of light and transfer the energy to special molecules that can, when stimulated, fire off an electron that causes chemical changes in the plant. Further processes turn the chemical energy into sugar.
 
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