• Question: Why is the earth round?

    Asked by mrsrichards to Andrew, Daniel, Hayley, Natalia, Peta on 16 Nov 2011.
    • Photo: Peta Foster

      Peta Foster answered on 15 Nov 2011:

      The Earth is round because of gravity. Gravity it the force you feel keeping your feet on the ground… it is caused because you have mass and the earth has mass and mass is attracted to mass via the gravitational force.

      What we can weight is what you get if you multiply the mass by the gravitational force… so if you were standing on the moon your mass would be the same but you would weigh less because the gravity there is lower because the moon is less massive as compared to the earth.

      Gravity pulls with equal strength in all directions; therefore any variations from a spherical shape will lead to gravitational forces that bring the shape back into that of a sphere.

      This physics allows us to predict how tall the tallest mountain could ever be on any planet and our mount everest is actually not that far off the tallest mountain that out planet Earth’s mass could cope with. Any bigger and the forces would crush it back down to a manageable size. 🙂

      Great question!

      P.S. If you want to know even more i have attached a link to a great video on this.

    • Photo: Daniel Scully

      Daniel Scully answered on 15 Nov 2011:

      Well Peta’s hit it right on the head.

      The important thing is that gravity is the same in all directions, and the only shape which is the same in all directions (from the centre) is a sphere.

      So the world ends up a sphere… well… almost… it’s a little fat around the mid-section because it’s spinning, so there is an extra force making it larger there.

    • Photo: Andrew Cairns

      Andrew Cairns answered on 16 Nov 2011:

      I won’t try to answer what others have in such a great way! Great question my friend!

    • Photo: Hayley Smith

      Hayley Smith answered on 16 Nov 2011:

      Yeh – great question! As the above scientists have said, it’s all to do with gravity 🙂
      But then some asteroids and stuff are kind of potato shaped, so you might have expected them to be round too…? but that’s all to do with gravity too. The mass and size of the asteroid are not enough for gravity to take over and make it spherical so it just kind of stays potato shaped.

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