If you had a huge 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 of a land It is actually slightly compressed on the poles, like someone pressing both hands on the top and bottom of a ball. As a result, the equator – where Ecuador sits – stands out. Instead of a full sphere, the Earth is “flat,” meaning that it is shaped like a slightly flattened sphere.
In fact, “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. So why don’t the Earth and other planets and moons rotate perfectly?
The obstacle is something called Centrifugal forceKane told Live Science, or the apparent external force experienced by a rotating object.
A spinning planet experiences centrifugal force. You can see it in action, too: If you’re spinning in a chair or on your feet, you should feel out of your center. Your arms or legs will probably lunge. Or, if you’re sitting on a merry-go-round, “there’s a little bit of extra force acting on you in that vortex, and so you feel like you’re pulled to the side,” said Kane.
As 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. If you look at a global picture of any of the gas giants, you’ll notice that they’re slightly powdery and medium bulges. The shape of these planets is more obvious because they are the fastest orbiting planets in the world Solar SystemKen said. 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. The dwarf planet 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 very quickly (one full revolution at a time four hoursIt’s “like an egg,” said Kane.
Originally published on Live Science.