Explain why is the sky blue? when you got to space, the sky is black but if you look at sky from earth, it looks blue. why is the sky blue and how does the color change over time?

As light moves through the atmosphere, alot of the longer wavelengths go straight through. a bit of red, orange and yellow light is affected by the air.
The blue light is 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. 

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