Why is the sky blue?

Blue sky, regarded as a rare phenomenon from where I live, the north of England. The north isn’t exactly blessed with great weather, I might as well live in Winterfell as it always feel like, well, winter.

Although on the rare occurrence when the clouds do disperse and the Sun pops out for all of five minutes we are greeted by beautiful blue skies. But why is the sky blue?

Light from the Sun appears white but it actually consists of many colors. If you pass this light through a prism, the light is separated and you will see all of the colors that you see in a rainbow. Light travels as a wave, and the distance between the peaks and troughs have an effect of what color the light will be. Blue light waves are shorter than red light waves for example.

Light travels in a straight line unless it is reflected, refracted or dispersed. When the light from the Sun hits the atmosphere it is scattered in all directions, due to all of the gases and particles in the air. As the light is scattered in the atmosphere most of the longer wavelengths pass straight through. However most of the shorter wavelength light is absorbed by tiny molecules in the air. The absorbed blue light is then radiated in all direction giving the sky its blue color. At the horizon the sky is a paler color, this is due to the light having to pass through more air.

However the sky isn’t always blue. When the Sun is close to the horizon, during sunrise and sunset, sunlight has to pass through more of the atmosphere, so most of the blue light has already been scatter leaving the longer wavelength light such as red.

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