• Question: why is the cloud smoke white and the cloud is blue?

    Asked by rubaty to Angela, Gabriele, Karen, Shane on 20 Nov 2013.
    • Photo: Shane Mc Guinness

      Shane Mc Guinness answered on 20 Nov 2013:

      Nice question,
      Well clouds aren’t smoke, they’re water vapour, just like what comes out of your kettle. Though neither are blue. They’re closer to white really. These water droplets scatter light from the sun, causing their white appearance.
      Smoke is made up of particles of burnt material which are floating in hot air, which rises because it’s less dense. Their colour is causes by the colour of the ash and small particles that are floating in the air. Think of the colour of the ash in your fireplace….

    • Photo: Gabriele De Chiara

      Gabriele De Chiara answered on 20 Nov 2013:

      Hi rubaty! I like this question! The colour of a cloud depends crucially on the material composing it. In the case of a smoke cloud this can go from bright white to dark grey. It is because the tiny particles flying in the air and coming from combustion of paper for example scatter light in all directions. Depending on the material that is burning and the amount of carbon/oxygen you have different colours of smoke. Now sky clouds are made not made of water vapour which is invisible. They are made of condensed water, that is small liquid droplets that are so light that float in the air. They condense and get together in a cloud. Again depending on the amount of droplets, their density and the position of the sun, clouds can have different colour: from bright white to dark grey (just before it starts raining!) and at sunset they are super fantastic! All the shades of pink, yellow, orange, purple and red! A simple natural phenomenon, but so nice to see!

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