Spears: Physicists step up with pop fly theory

A look at Alan Nathan and his “collision experiments”...

“A baseball is a funny object. If a baseball were the same size and weight, but perfectly smooth, then its aerodynamics would be very different and would be much easier to characterize,” Nathan says.

The stitches not only stick up, but they do so in a non-symmetrical way. “It’s a funny, figure-eight sort of thing.”

In plain English, air doesn’t like to slide over the ball’s surface. There’s friction. But air slides more easily over other air, even if the two air masses are going in different directions. Each stitch creates a tiny swirl of air near the ball’s surface, which makes the ball pass through the surrounding air more smoothly. But the stitches aren’t spread evenly around the ball. Throwing with a seam angled one way or another causes more stitches to do their efficiency-boosting work on one side than on another.