• Question: Why is the sky blue?

    Asked by sevvalA to Heather, Helen, Hugh, Jane, Julian on 11 Nov 2014. This question was also asked by *Samara*, RowantheBird.
    • Photo: Julian Onions

      Julian Onions answered on 11 Nov 2014:

      The sky is blue because blue light is scattered a bit more than red light, so it tends to look a bit bluer than red.

      This video covers it in 10 seconds

      or if you’ve got longer – here is a slightly longer explanation

    • Photo: Jane MacArthur

      Jane MacArthur answered on 11 Nov 2014:

      The sky appears blue because molecules in the air scatter blue light waves from the sun more than they scatter red light. This is because the blue light travels as smaller shorter waves than the red light.

    • Photo: Helen Johnson

      Helen Johnson answered on 11 Nov 2014:

      The sky is blue because our atmosphere splits up the light from the Sun, just like a prism, and scatters it into different colours. The blue light is scattered more than the other colours, and that’s why we see blue the most. There’s a good explanation with some diagrams here: http://spaceplace.nasa.gov/blue-sky/en/

    • Photo: Hugh Osborn

      Hugh Osborn answered on 11 Nov 2014:

      Imagine waves coming into a harbour. Sometimes those waves are able to ‘turn the corner’ and rock boats in the entire harbour, even if they’re not ‘in line’ with the waves coming from out at sea. In will seem like the sea waves will spread out from the harbour entrance in all direction [ like | | | | : ) ) ) ]. However, this actually only happens when the distance between the waves (wavelength) matches the width of the harbour entrance. This is called diffraction.

      The same thing happens with light. Blue light has a wavelength that is close to the distance between particles in the air (think the width of the harbour entrance), meaning blue light is diffracted elsewhere. Red, yellow and green light has a longer wavelength, so is not diffracted as much. So, when you’re looking at the sky rather than directly at the sun, you’re seeing blue light being bent ’round the corner’ into your eyes.

      Hope that helps!

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