The earth is not perfectly spherical. It bulges a bit around the equator so a person standing at zero degrees latitude is about 13 miles farther from the center of the earth than one standing at a pole. (The author of this essay also bulges a bit around his equator but this is better discussed elsewhere.) The reason for this bulge is the outward “centrifugal force” caused by the rotation of the planet.
Centrifugal force from rotation causes loose unrestrained matter to fly outward from the center; indeed it is this force that enabled Dovid to sling a rock at high speed at Golias. The earth’s rotation similarly propels mass outward at low latitudes resulting in the equatorial bulge. The force is strong enough that a person weighing 150 pounds at the North Pole weighs about seven ounces less at the equator. (Hmm … maybe the author should move toEcuador!) The reason that the earth’s surface does not fly outward is that the centrifugal force is countered by the pull of gravity an inward-propelling force also known as the “centripetal force” (which means “toward the center”).
An old saying claims that “what goes up must come down” testifying to the universal presence of gravity. However we routinely use GPS navigators that receive signals from satellites that are 12600 miles above the earth yet don’t come down. The reason they stay up is that they continuously orbit the earth at a speed of around 8 700 miles per hour. This circular motion produces a centrifugal force that counters gravity’s centripetal force. Aerospace engineers (okay “rocket scientists”) carefully choose orbits that balance these forces to keep the satellites at a constant altitude.
This GPS technology is vital to modern life. It’s not just used in navigation; it’s also used to transmit accurate time signals to businesses such as banks which in turn use this information to securely send and receive data. Satellites are used for weather prediction environmental monitoring and a myriad of other applications. Our 21st-century lives would be very different without the balance of centripetal and centrifugal forces. To ask which force is “better” is a meaningless question since both are vital.
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