If you had a giant tape measure that started at the center of the Earth and went to the highest peak on our planet, you wouldn’t look at Mount Everest. Instead, it will be the tallest mountain on the other side of the world: Chimborazo in Ecuador.
Chimborazo wins in this case because the ground is actually slightly compressed at the poles, like someone pressing both hands on the top and bottom of a ball. As a result, the equator – where Ecuador is located – is protruding. Instead of a full sphere, the Earth is ‘flat’, meaning 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. Why don’t the Earth and other planets and moons rotate perfectly?
The drawback is something called centrifugal force, Kane told Live Science, or the apparent external force experienced by a spinning object.
And if you’re spinning in a chair or on your feet, you should feel out of your center. And maybe your arms or legs will lunge. “There’s a little bit of extra force acting on you in that whirlpool, so you feel like you’re pulled to the side,” Kane said.
Because the planets and moons rotate, the centrifugal force causes them to swell at the equator. The effect can be very subtle, but good examples are Jupiter and Saturn. And if you look at a global picture of any of the gas giants, you’ll notice that they’re slightly crushed 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. It is located in the Kuiper Belt, a region of icy bodies outside the orbit of Neptune. 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.
Source: Live Science