• Question: When and why is the moon sometimes red?

    Asked by lisaloo to Claire, Kate, Matt, Rob, Sam on 24 Jun 2013.
    • Photo: Claire Lee

      Claire Lee answered on 24 Jun 2013:

      This happens during a lunar eclipse – when the earth comes in between the sun and the moon.

      We see the part of the moon that reflects the light from the sun. A full moon is when the sun and moon are on opposite sides of the earth, so the suns rays pass the earth, bounce off the moon, and come back to us.

      But the earth can make a shadow too, and sometimes the moon passes through the earth’s shadow – at this point the moon looks dark, and that’s called a lunar eclipse.

      Now this is when the cool stuff happens – while the moon is in the shadow, some light from the sun passes close to the earth, through our atmosphere, and is bent (refracted) on to the moon. Light is made up of all the colours of the rainbow, and these colours get scattered away as light passes through the atmosphere, until only the red light is left. So in this particular instance you have red light going to the moon, and reflecting back to us, making hte moon appear red 🙂

      Here is a nice site with great pictures too:
      http://earthsky.org/space/why-does-the-moon-look-red-during-a-total-lunar-eclipse

    • Photo: Kate Husband

      Kate Husband answered on 24 Jun 2013:

      The moon is normally redder when it is near the horizon in the same way the Sun is (during a sunset/sunrise). This is because the red light is scattered less (because its wavelength is longer) and so all the blue light is scattered out the way leaving the red light behind. This effect is increased when the object is near the horizon as the light travels through more atmosphere.

    • Photo: Matthew Pankhurst

      Matthew Pankhurst answered on 25 Jun 2013:

      The moon sometimes appears red because the light is filtered out by the atmosphere. The molecules and dust in the air bounce the blue light away, but red light is sort of less bouncy! It happens when the moon is low on the horizon, because there is more air between you and the moon! There is less air between you and the moon when it is directly above you, so just about all of the light gets through to you 🙂

Comments