• Question: how did they measure the size of a planet?

    Asked by melisa13 to Susana, Sam, Ed, Dave, Ben on 24 Jun 2013.
    • Photo: David Briggs

      David Briggs answered on 24 Jun 2013:

      Trigonometry – if you know how far away the planet is, and you can measure the distance across the disc of the planet as it appears down a telescope, then you can work out it’s approximate size.

      If you send space probes there you can get closer and make more accurate measurements.

    • Photo: Susana Teixeira

      Susana Teixeira answered on 24 Jun 2013:

      Yes, Dave said it already. If you want more details I find this page explains it well: http://www.astronomynotes.com/solarsys/s2.htm

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