• Question: When lasers are sent in the direction of the moon to see how long it takes for them to return in order to see how far away the moon is. How does the laser return once touching the moon?

    Asked by jodiebeard to Mike, Pip, Tianfu, Tim, Tom on 26 Jun 2012.
    • Photo: Tom Lister

      Tom Lister answered on 26 Jun 2012:

      The moon is made mostly of grey rock, so the light bounces back just like when you shine light on a grey rock. Admittedly, most of the light is absorbed or bounces of in the wrong direction, but enough light must travel back.

    • Photo: Tim Stephens

      Tim Stephens answered on 26 Jun 2012:

      The astronauts that went to the moon in the late 1960’s and early 1970’s left something called a ‘corner cube reflector’ on the moon. This is a special reflector that returns a beam of light directly back to where it came from. So the laser beam that’s sent to the moon is reflected off this and sent back to the laboratory that is measuring the distance.
      The reflectors that you see on the back of bicycles and cars (with the kind-of crinkly appearance) are also corner cube reflectors.

    • Photo: Tianfu Yao

      Tianfu Yao answered on 26 Jun 2012:

      Agree.

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