I'm trying to understand why a superdeformed nucleus may be represented as bulging perpendicular to the axis of rotation, and I'm guessing this is akin to why the Earth does so too. I've gone through secondary school and 3 years of University to have professors/teachers snigger every time they hear the word centrifugal force. But whenever I look up the explanation for bulging, centrifugal force is always mentioned. I honestly can't recall a situation where I've had to consider anything called a centrifugal force and I can't with any confidence even say what such a force even is. If I were to guess, in the non-inertial rotating frame of reference it's a force that appears to exist due to the Coriolis effect - throw a ball and it will seem to move from its original trajectory, as if a force was being applied. However to a stationary observer outside the rotating frame we of course just see the ball being thrown in a straight line - no force is being applied to anything. Is there any way to understand why the Earth bulges at the equator due to its rotational motion, without having to delve in to the concept of centrifugal forces?