Biomechanics: More Info

How does a curveball work?

Ask any batter and they will confirm that the curveball is one of the hardest pitches to hit. Its twists, turns and power have left both batters and physicists fascinated. That's because a curveball can curve as much as 17-and-a-half inches from a straight line.

Although batters who have faced repeated curveballs are convinced the ball can curve right before the plate, physicists, with years of research behind them, argue this phenomenon is simply not possible.

Scientists have looked at the characteristics of a curveball and have found a number of different reasons why it curves the way it does. What they've found is that the actual construction of the ball, with its 216 stitches of red cotton, has a lot to do with how the ball spins.

Upon closer observation, discoveries have also been made on how air forms around the ball and stitches. Physicists have noticed that when a curveball is thrown with a backspin, the top of the ball is moving in the same direction as the air around it while the bottom of the ball is moving in the completely opposite direction as the air. It's this difference in air movement that causes the ball to curve and ultimately break in a manner that can fool a batter.

Physicists conclude that a baseball cannot begin to curve right before the plate because the power of the curveball is with it from the time of release. It cannot begin to curve or have more or less power at any given point of its flight. Physicists suggest that it's probably the position of the batter that makes it appear as if the ball is curving directly before the plate.