• Question: What's the shape of the Earth?

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      Asked by i love science to Andy, Chris, Harriet, Jess, Nikki on 17 Mar 2016.
      • Photo: andy chapman

        andy chapman answered on 17 Mar 2016:

        For a very long time we thought it was a flat, then an indescribably clever experiment by Eratosthenes confirmed the ancient greek suspicion that it was a sphere by measuring the earths circumference:

        https://en.wikipedia.org/wiki/Eratosthenes#Measurement_of_the_Earth.27s_circumference

        We now now that it is actually an slightly squashed sphere (since it spins around the poles, centrifugal force – like the force pulling you off a spinning round about in a play park – makes the earth bulge around the edge). Technically it is an oblate spheroid

      • Photo: Christopher Blanford

        Christopher Blanford answered on 17 Mar 2016:

        Andy beat me to this answer, so I’m going to chime in with a fun fact:
        The roundest object ever made by people is a sphere of silicon that they’re using to define the standard ‘mole’ (the chemist’s way of keeping track of lots of molecules). If the sphere were the size of the earth, the highest mountains would only be 5 metres tall!

        http://www.nist.gov/pml/si-redef/kg_new_silicon.cfm

      • Photo: Harriet Reid

        Harriet Reid answered on 17 Mar 2016:

        An oblate spheroid, ie a slightly squashed ball.

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