Why does our earth look like a ball?

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Offline omid

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Why does our earth look like a ball?
« on: 30/01/2010 13:35:45 »
Yesterday omid's chemistry teacher told us that our earth is not exactly round but somewhere it looks like an egg?
what gives earth that shape???????????????????


Offline yor_on

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Why does our earth look like a ball?
« Reply #1 on: 30/01/2010 16:27:03 »
Earths shape 

It has to do with when it was rotating faster, as well as when it was hotter, and much more 'plastic' than it is today. It was then it got the form it has today. And that's also why it bulges more around the equator than the pole as the centrifugal force got most concentrated in the direction of the rotation. And it started around four and a half billion years ago, as smaller bits of matter in solar orbit came together gravitationally. their kinetic energy became heat as they collided 'melting' them together to later become our Earth.

The heavier materials in this molten soup sunk to the bottom (iron and nickel) with the lesser dense materials floating above. nowadays the exterior is cooler but the interior is still hot. also there are radioactive elements inside Earth that still releases energy, warming it up. That still leaves the question why it rotated in the first place :) Well, it seems that everything has a 'spin' to it? planets too. One answer might be that as the bits clumped together once, so long ago, they followed an (gravitationally) easiest path that also translated into a rotational energy as they hit together and the planet started to form.

And it should also have a lot to do with what's called 'tidal forces.' that transfer the 'angular momentum' which then will become the rotation we see. As everything started once (the universe) as a very hot cloud of gas that later collapsed into clumps of matter, then those clumps might have introduced those 'tidal forces' on each other, making them start to rotate. Just as the moon have an tidal influence on our oceans creating the tides,  influencing our rotation, the same way that Earth influence the moons rotation, slowing it down.

Ancient astronomy.

"Some Chinese astronomers thought the earth was a hemisphere-like globe sliced in half underneath a dome-shaped universe. Other Chinese thinkers believed the universe was shaped like an egg, with a sphere-shaped earth in the middle of the egg. In other words, they thought of the earth as the yolk."

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