The ball drops and soars unpredictably because it doesn’t spin. The lack of rapid spin turns the seams of the baseball into tiny airfoils—surfaces that create lift and drag when they fly through the air. As the air passes over the seams, tiny swirls are created, causing pockets of low pressure around the surface of the ball. As air rushes in to fill the pockets, the ball is pushed in different directions. If the ball rotates too much, the seams will present a more consistent surface to the wind, and the ball will likewise follow a smoother path.