WHY IS THE SKY BLUE?
1 THE SUN'S LIGHT
Light from the Sun may look white, but it is actually a combination of many colors. The colors blend into one another, causing us to see white. The colors have different wavelengths, frequencies, and energies.
2 THE COLLISION OF BLUE
As the Sun's light enters the atmosphere, it collides with the nitrogen and oxygen molecules. The longer red wavelengths pass through unaffected, but the shorter blue wave lengths collide and scatter in all directions, creating the shades of blue in the sky.
3 MORE COLLISIONS FOR SUNSET
As the Sun gets lower on the horizon, there is more atmosphere for its light to travel through. All this extra atmosphere has scattered out all the shorter wavelengths, including blue, leaving only the red ones to hit your eyes.