Question: Why is the sky blue?

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  1. The sky is blue because the earth has a layer of gases around it – the atmosphere. This layer of gases (like nitrogen, oxygen,carbon dioxde), tiny bits of ice and water vapour protects us from radiation from the sun, helps regulate the temperature of the planet and produces weather. When sunlight hits this layer of gases, the light is scattered. As you would know, white light is composed of 7 colours – red, orange,yellow, green, blue, indigo, purple. Red light has a longer wavelength than blue light, purple light has a shorter wavelength still. The longer wavelengths just pass through the atmosphere. But the different gas molecules absorb the shorter wavelengths of light, like purple and blue, then scatters it in different directions. So everywhere you look, as long as the sun shines, the sky is blue.


  2. It’s all about selective scattering of the different coulours of light that make up the spectrum… i.e. what Upulie said 😉

    A similar effect causes the beautiful colours of sunrise and sunset, where the dust in the lower atmosphere scatters the blue light more than red, so the sky appears orange/red



  1. I always admired the colour of the sky and how it changes colour at night or when it dawn.