While most pitchers control their throws by putting in a touch of spin, knuckleball pitchers spin the ball as little as possible. The result is a slower-moving pitch that zig-zags erratically from left to right—the likes of which can throw off even the most experienced batters, Jennifer Ouellette reports for Gizmodo.

What causes a knuckleball to move?

A knuckleball or knuckler is a baseball pitch thrown to minimize the spin of the ball in flight, causing an erratic, unpredictable motion. The air flow over a seam of the ball causes the ball to change from laminar to turbulent flow.

Is a knuckleball bad for your arm?

Because the pitch travels at 60 mph to maybe 80 mph, throwing that "softly" puts far less stress on an arm than throwing 90 mph or above. So the knuckleball can be very effective. It can resurrect pitchers' careers. It can keep guys in the majors who might otherwise have been out of baseball years earlier.