playitbackward asked: "Centripital Force, you're right, I always mix those up."
You were right the first way you said it. Centripetal force is what keeps earth's mass from flinging out in all directions. Centrifugal force, on the other hand, is the "fictitious force" of earth's inertia acting against the centripetal force of gravity. It's called "fictitious" because it doesn't result from physical interaction, but it is still a very real force, experienced in a rotating frame of reference (the earth's mass, people in a car going around a turn, etc). Since there's more inertial mass at the equator, centrifugal force is strongest there, causing the (slight) bulge in the equator. (I'm not a physics student -- but I believe this is correct)
The consensus seems to be that I was mixed in being right the first time. Centrifugal force is the “force” that causes the Earth to bulge, even though it isn’t necessarily a “force”, even though it is. Centripetal force is the force in the example I gave with the carnival ride, the force created when you swing around a ball on a string. I should have been paying closer attention, but I was spacing out (if you will, teeeeheeeheee). Thanks to all my vigilant readers who wrote in!
