• Question: Why is the sky blue during day and orange during sunset?

    Asked by anon-187764 to David on 8 Nov 2018.
    • Photo: David Ho

      David Ho answered on 8 Nov 2018:

      The sky is blue during the day because when light from the sun hits the atmosphere, it gets scattered off air molecules (the physicist’s name for this is “Rayleigh Scattering”). Blue light gets scattered more than other colours, so that’s why it looks like there’s blue light coming from everywhere in the sky.

      During sunset the sun is lower in the sky, so light has to pass through a longer distance in the atmosphere before it reaches us. This means that the blue and green light is scattered so much it doesn’t reach us anymore, so we only see the other colours of light — mainly red and orange.

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