• Question: Why is the earth a sphere and not a cuboid, for instance?-

    Asked by to Daren, Lynne, Phillip, Simon on 23 Jun 2014. This question was also asked by .
    • Photo: anon

      anon answered on 23 Jun 2014:

      Everything has gravity – you are attracting everything around you ever so slightly, just not strongly enough for you to notice!

      When the earth formed, gravity pulled all the particles together. Gravity pulls things in from the centre of mass (in this case, the centre of the earth) and any new particle coming to join the earth went to the position that was closest to the centre. The best shape where every particle on the surface is the same distance from the centre is a sphere. If the earth was a cube, the points would have been much further away!

    • Photo: Lynne Thomas

      Lynne Thomas answered on 23 Jun 2014:

      The centre of the earth is much denser than the surface and this means that it has a strong gravitational pull – there is in essence much more “stuff” there than anywhere else on earth. It is about the same strength in all directions so the rest of the mass sticks to it in something that is approximately a sphere. Because the earth spins on an axis and rotates around the sun, the shape is actually not a perfect sphere – it is flatter at the poles and bulges at the equator but not by so much that it makes much of a difference.

    • Photo: Daren Fearon

      Daren Fearon answered on 23 Jun 2014:

      Earth being a sphere means all the points of the surface of the Earth are fairly similar (not identical as the Earth isn’t a perfect sphere) distances to the Earths core which is much denser and applies gravitational pull to the surface. If the earth was a cube then the gravitational tug would differ on the parts that are further away from the centre.

    • Photo: Phillip Manning

      Phillip Manning answered on 25 Jun 2014:

      The Earth is not a perfect sphere. It is an Oblate Spheroid. The term “Oblate” refers to it’s slightly oblong appearance. The term “Spheroid” means that it is almost a sphere, but not quite. This shape is indeed a direct function of gravity…with the materials that construct our planet aligning relative to the fields of gravity pulling everything towards to the core.

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