If you had a giant tape measure that started in the center of the Earth and went to the highest peak on our planet, you wouldn’t look at Mount Everest, instead, the highest mountain on the other side of the world would be Chimborazo in Ecuador, and Chimborazo wins in that case because the Earth is actually compressed Slightly at the poles, like someone pressing both hands on the top and bottom of the ball.
As a result, the equator – where Ecuador is located – stands out, and instead of a full sphere, the Earth is “flat”, meaning that it is shaped like a slightly flattened sphere.
“Actually, most planets and moons are not true spheroids; they are usually squashed one way or another,” said James Tuttle-Kane, a planetary scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California.
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Why don’t the Earth and other planets and moons rotate perfectly? The obstacle is something called centrifugal force, Kane told Live Science, or the apparent external force experienced by a rotating object.
And if you’re spinning on a chair or on your feet, you should feel out of position, and your arms or legs may lunge.
Or if you’re sitting on a roller coaster, Kane said, “There’s a little bit of extra force acting on you in that whirlpool, so you feel like you’re pulled to the side.” Because the planets and moons rotate, the centrifugal force causes them to swell at the equator.
The effect can be quite subtle, but good examples are Jupiter and Saturn, and if you look at a global picture of either gas giant, you’ll notice that they’re a little squishy with moderate bulges.
Kane said the shape of these erupting planets is more noticeable because they are the fastest orbiting planets in the solar system. The faster an object rotates, the greater the centrifugal force on it.
One extreme example of the effect of centrifugal force on an object is the dwarf planet Haumea, Kane said, located in the Kuiper Belt, a region of icy bodies outside Neptune’s orbit.
Haumea is about the size of the planet Pluto, but it rotates so fast (one complete revolution every four hours) that it is “almost like an egg,” Kane said.