• Question: How come from space water on earth looks blue when it is actually clear?

    Asked by rosafernandes25 to Ed, Hayley, Jason, Nathan, Sophie on 16 Mar 2013.
    • Photo: Hayley Evers-King

      Hayley Evers-King answered on 16 Mar 2013:

      This is to do with the way water interacts with light. Light is made up of many colours – the ones you see when it is split up in to a rainbow. When you have deep water, different colours of light are absorbed and scattered differently. Water absorbs red light and scatters blue light, the effect of this is that when you look at deep water you see the blue light being reflected back at you. This can change if their are other things in the water – the ocean can look green and even red if their are lots of algae (they absorb blue light).

Comments

  • Photo: scibtings123

    scibtings123 commented on :

    yes you are right that the water is clear. its because the sky is reflecting on to the water.

    • Photo: Hayley

      Hayley commented on :

      Actually that’s not right. The ocean doesn’t reflect the sky or vice versa. The molecules in the sky scatter blue light more than others, that is why the sky is blue.The ocean (when it is sufficiently deep enough) absorbs red light and reflects blue light. When you have a glass of water there is not enough of it to absorb all the other colours of light, so you see all the colours i.e. white or clear light. It’s nothing to do with the sky. If you get enough light (a really big torch for example) and shine it on the ocean at night time, it will still look blue/green/brown/red depending on the substances that are in it.