Spin acting against the force of air, which acts as a force against the end of the ball just as gravity acts as force against the bottom of a spinning top. In o

Spin acting against the force of air, which acts as a force against the end of the ball just as gravity acts as force against the bottom of a spinning top. In other words, it should not tip over if thrown in a vacuum. We've known that spin prevents an object from tumbling thru the air since at least the invention of rifling (a little before the American Civil War). It's the tipping over that was unexplained.