• Question: Why does the sun look red when it sets but during the day and some night the sun isnt red? plaese reply. ty ;]

    Asked by hillierl to Alastair, Emma, Hywel, Keith, Vicki on 16 Jun 2010 in Categories: .
    • Photo: Hywel Vaughan

      Hywel Vaughan answered on 16 Jun 2010:

      That is a really good question! It is all based upon the principles of light and how different wavelengths travel through the air. I believe there was a question earlier about why the sky is blue, and it is all the same answer (I may have explained it better there!)

      Quite simply, as light travels through the atmosphere, it interacts with the air particles and bits of dust etc. This causes different parts of light to scatter at different angles. As light it made up of waves (like everything in the electromagnetic spectrum), the different colours have different wavelengths. Short wavelengths such as blue are effected the most, whereas red has a longer wavelength and keeps going.
      During the day, the light from the sun is going through a small amount of atmosphere and the blue is being refracted at an angle so you can see it. At sunset, when the light has to travel through lots more atmosphere, the red keeps going straight towards you, hence why it appears red 🙂

    • Photo: Keith Brain

      Keith Brain answered on 16 Jun 2010:

      The sun looks red whenever is it low in the sky because the light travelling from the sun has to pass through a greater thickness of the atmosphere. In the atmosphere, blue light is scattered (bounced away) most easily, and so all you see is the red light. This effect can be even greater if there are levels of particulates (eg. pollution) between you and the horizon, so how red the sun looks at dusk and dawn can vary from day to day.

    • Photo: Alastair Sloan

      Alastair Sloan answered on 16 Jun 2010:

      This is due to the light from the sun being scattered and split into its different wavelengths. This During the day the shorter wavelength blue light travels through the atmosphere and is scattered by gas molecules and into our eyes so the sky looks blue. and we can’t see the longer wavelength red light. At sunset light has further to travel through the atmosphere so the blue light travels out of our sight but the red light is left to be pass through the atmosphere and into our eyes, hence the sun looks red.

    • Photo: Vicki Stevenson

      Vicki Stevenson answered on 16 Jun 2010:

      If you shine white light through a prism, you can split it into red, orange, yellow, green, blue, indigo and violet – this is called refraction. The sun shining through rain drops is the same effect and causes a rainbow. When the sun shines directly through our atmosphere in the middle of the day the light refracts so we see the sky as blue. At dawn or dusk, the light travels through more atmosphere, so the sky looks red.

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