Return to my Astronomy/Space pages
Go to my home page
© Copyright 2000, Jim Loy
What if the Earth were a cube? Well we would have eight huge mountains over 1000 miles high, and... But wait. I could come up with more details. But these huge mountains would not last more than a few hours. They would collapse under their own enormous weight, and spread out horizontally into the low lands. This cube shaped Earth would soon be nearly spherical. Very large, relatively dense objects (planets, stars) cannot be anything but very close to spheres.
So how close is the Earth to being a sphere? Well it spins. And so it is slightly wider (by about 13 miles or 22 km) at the equator than from pole to pole. That makes it an "oblate spheroid." A spheroid is almost a sphere. "Oblate" means wider at the equator. "Prolate" would be wider at the poles. That situation can happen to a moon experiencing a strong tidal force.
The Earth is not a perfect mathematical spheroid either. It has mountains and valleys. The tallest mountain is about 7 miles high. On a 12 inch globe, that's about the thickness of a sheet of paper. So our tallest mountain is hardly noticeable, compared to the huge size of the earth. Even smaller objects (football stadiums, houses, plants, animals, the tides, etc.) are even less noticeable. "Oblate spheroid" is a pretty darned accurate description of the shape of the earth.
Addendum:
I received email complaining that I was going on an on about the earth being an oblate spheroid. Apparently that reader didn't think anyone should have any curiosity about this. The reason that I brought the subject up is that many books say that the earth is an oblate spheroid, without defining either "oblate" or "spheroid." Maybe I'm the only person who had some small amount of pleasure from the above article. But these are my pages, so that's good enough.