Will Sullivan, Staff Writer
October 12, 2021
(Inside Science) -- Earth might look like a sphere, but it's actually an "oblate spheroid" -- the planet is slightly squished, making the circumference of the equator bigger than the circumference through the poles. Clouds, ocean currents, and long-range missiles all would behave differently if Earth were perfectly spherical.
This bulge exists because of a force created by Earth's rotation. As a result, a person on the equator is over 13 miles farther from Earth's center than a person on the North Pole is. That difference is more than double the distance between sea level and the top of Mount Everest, but on a planetary scale, this bulge is virtually imperceptible. Boyd Edwards, a physicist at Utah State University in Logan, said it's roughly equivalent to a single layer of duct tape around a spherical volleyball.
Earth is so close to being spherical that physicists sometimes will treat it as such in their models, said Edwards. But this simplification can cause significant errors when calculating motion on Earth's surface.
In a paper published in August in the American Journal of Physics, Edwards and his brother John Edwards, a computer scientist who also is at Utah State, demonstrate how Earth's spheroidal shape affects motion by envisioning an Earth that is completely smooth and covered in frictionless ice and asking what would happen if you shot a hockey puck across its surface...
