Book 28, Question 4
Why does a curveball curve?
A curveball leaves the pitcher's hand spinning forward with a lot of topspin.
As the ball flies, the spinning surface drags air around with it, making the air pressure on the sides unequal. That pushes the ball down and sideways, so it dips before it reaches the batter. The ball is not magic: the spin changes the way air flows around it.