• Question: Hi there, How is the sky blue? Does the sea reflet off the sky or vise versa?

    Asked by anon-259411 on 11 Sep 2020.
    • Photo: Ashleigh Barron

      Ashleigh Barron answered on 11 Sep 2020:

      The sky is blue because the light from the sun (which is white but made up off all the visible colours – the same as in a rainbow) bumps into and scatters off of molecules, gasses and particles in the atmosphere. Blue light is scattered more than the other colours in the sunlight as it has a shorter wavelength so the sky appears blue. The sea is blue because red light (which has the longest wavelength of visible light) is absorbed by the sea leaving behind the blue colour which we see.

    • Photo: Constance Schere

      Constance Schere answered on 11 Sep 2020:

      Great question! The reason the sky looks blue to us is because blue light travels in shorter waves than the other colours (red has the longest wavelength, for example). The light coming from the sun might seem white but it’s actually made up of all the colours. When this light shines down on us, only the blue and violet waves are small enough to hit the gas molecules found in the atmosphere and become separated from the other colours (red, green, yellow, etc.), which remain white to us. In other words, blue light is scattered when it hits gas molecules and other particles in the atmosphere while the other colours are not.

      Sunsets appear red because the sun gets lower in the sky and so more of its light is visible to us. This scatters more of the blue light, and the red and yellow can shine through! Also big particles of dust, pollution, and water vapour tend to reflect and scatter more of the reds and yellows, making the whole sky look red.

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