The unpredictability of knuckleballs

I’ve always thought that when a pitcher throws a curve ball, the ball curves because of the direction of the spin placed on it. Why, then, does a knuckleball move so unpredictably, when a knuckleball has little or no spin on it? It’s almost baseball season, and I need an answer soon so I can enjoy the games without these nagging questions. — Padre Fanatic, University City

It seems to me any Padre fanatic would have more nagging questions than this. A whole roster full of nagging questions. The mysteries of the knuckleball are less troublesome. Every pitched ball curves or zigzags because of unequal areas of air turbulence around it. A curve ball, thrown with a tight, consistent spin, will follow a path that curves away from air turbulence created by the side of the ball spinning into (that is, in the direction opposite to) the onrushing air. A knuckleball is thrown, almost pushed, stiff-wristed, from between the fingertips, like squirting a grape out of its skin. The idea is to have the slowest rotation possible on the ball. The stitches on the ball create the air turbulence that governs how the knuckleball behaves. The ball presents a slightly different profile of stitches as it turns very slowly. Each new profile creates a new pattern of turbulence. Wind tunnel tests have shown that given the sinuous pattern of stitches on a baseball, the ideal knuckleball should make only a quarter turn between the mound and the plate to maximize the effect of the stitches and make the ball dance as unpredictably as the Padres’ upcoming season.