• Question: how dose the gassis in the atmothear effect the couler of the sky ?

    Asked by 12parrk to Lyn, Katy, Paul, PB, Ruth on 21 Jun 2013. This question was also asked by georgiechiko, holmenat.
    • Photo: Peter Balfe

      Peter Balfe answered on 21 Jun 2013:


      The blue we see is probably pretty universal, as it’s light scattering which underpins it is. Check out the lovely blue sky in some of the landscape pictures sent back from Mars…

    • Photo: Ee Lyn Lim

      Ee Lyn Lim answered on 21 Jun 2013:


      Gas molecules in the air scatter light waves coming from the sun, and light with shorter wavelengths (blue, indigo, purple) are scattered more than light with longer wavelengths (red, orange, yellow). During the daytime when the sun is overhead, lots of scattering means lots of blue light finds its way into your eyes, which is why we see the sky as blue. But during sunrise and sunset, the sun is much further away, and by the time the sunlight reaches your eyes all the blue light has been scattered away. What’s left are the light waves that aren’t scattered as much, which are red and orange, which is why the evening sky looks red.

      If there are other particles in the sky besides the usual nitrogen and oxygen, the colour of the sky can change too. Water droplets (like clouds, mist or fog) are very large compared to molecules, and scatter all light colours equally, so you see white. If there are small particles in the air (like from volcanic eruptions or smoke) they can scatter different wavelengths of light, and make the sky different colours too.

    • Photo: Paul Waines

      Paul Waines answered on 25 Jun 2013:


      The colour of the sky is caused by light scattering. Blue skies happen because of something called the ‘Rayleigh Effect’- its caused by air molecules (which are tiny) scattering light.

      White light is a mixture of lots of different colours (rainbows are caused by white light entering raindrops and being split into these colours). We see the blue light because its more likely to be scattered by air molecules.

      Red sunsets are seen after a warm day, normally. The warmth of the day mixes the different air molecules up, including the bigger ones, and this is why you see red, which usually is more difficult to scatter.

    • Photo: Katy Brown

      Katy Brown answered on 25 Jun 2013:


      Yep, I think that pretty much covers it. Some people study the colour of the sky and how things in the sky look from Earth – this is called Atmosphere Optics (http://en.wikipedia.org/wiki/Atmospheric_optics).

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