• Question: why is the sky blue but space black

    Asked by anon-229943 to Alex, Anisha, Elena, Hira, Isaac, Sarah on 13 Nov 2019.
    • Photo: Sarah Knight

      Sarah Knight answered on 13 Nov 2019:

      Good question! Light is actually made up of all different colours. Each colour of light has its own “wavelength”: it might be long waves or short waves. When light from the sun hits the Earth’s atmosphere, the light is scattered in all directions by the different particles in the atmosphere. Blue light has short waves, and short waves are scattered more than long waves. This means more of the blue light is scattered towards our eyes, so the sky looks blue.

      At night, space looks black because our part of the Earth is facing away from the sun, so there’s no light being scattered. And if you were on the Moon, which doesn’t have an atmosphere to do any scattering, then it would be black all the time!

    • Photo: Anisha Wijeyesekera

      Anisha Wijeyesekera answered on 17 Nov 2019:

      Yep – as Sarah said above, light scatters when sunlight reaches Earth’s atmosphere, and goes in all directions. We see a blue sky much of the time as blue light travels as shorter, smaller waves. Space looks black because there is no light scattering from the sun in the same way.

Comments