The formula: The expression of the lateral force, as a function of angular orientation, of a 65-mph knuckleball. When a ball is not spinning and the stitches are exposed on one side, the drag force on the smooth side of the ball is greater. – Nicholas J. Giordano, Purdue University, and Robert G. Watts and Eric Sawyer, Tulane University
The grip: Originally the pitch was thrown with at least one knuckle pressed against the ball. Kids may still throw in that way. Today's pros stunt rotation by holding it with the tips of fingers or digging the fingernails into the leather hide.
The unpredictability: Degrees of spin applied to 'normal pitches' – fastballs, curves, sliders, changeups and splitters – cause a relatively predictable break near the plate. In contrast, the lack of spin on a knuckleball can cause the ball to move several times.
The final location: A one-quarter rotation in the 60-foot 6-inch path from mound to home plate is ideal. A pitcher's mechanics are critical. The University of Texas showed that different "angular orientations" can result in up to 2.5 feet of horizontal displacement of the ball.
The movement: Lateral forces on the ball's exposed stitches cause oscillations, which influence trajectory. Kinesiologist Thomas Karakolis of the University of Waterloo compares the action to wind force on the wings of a plane: One side of the ball is pushed harder by the wind than the opposing side, causing it to move.