Scratch That One

Have you ever been watching a major league baseball game and wondered why the catcher gives so many balls back to the umpire, who then throws it out? Every time a pitch is thrown in the dirt, the catcher turns and hands the ball over to the home plate umpire. More often than not, after a brief examination, the umpire will then roll the ball back to the home team’s dugout where an eager ball boy scoops it up and officially retires it from the game. If you haven’t ever noticed this, watch a game this weekend. It’s more noticeable if you actually go to the ballpark because television cameras usually focus on whatever the announcers are discussing between pitches rather than the minutiae of the game. The reason is so that the pitcher cannot gain an advantage with a scuffed or scratched ball.

Back in the good ol’ days, some pitchers would actually take razors, tacks, sandpaper, or anything else they could smuggle out to the mound to scrape and scuff the baseball. Why? It’s basically simple physics.

If you’re looking for an interesting book to read and you are not bored by the finer points of either baseball or scientific study, I recommend Robert K. Adair’s text, The Physics of Baseball. Here, he described the possible result of pitching with an illegally modified ball that has been scuffed on one side:

Scarring or scuffing the ball can produce asymmetric forces on the ball that result in aberrant trajectories. Since it is probably impractical to scuff or scrape the surface of the ball so that the imperfection has as dominant an effect as the stitching, it might seem that such modifications cannot be very important, and that is largely the case for casual throws. But the highly skilled pitcher can throw the ball so that the effect of the stitches is symmetric, but if the ball is scuffed on one axis – and not on the other – unbalanced forces can be realized, which act only in one direction…Properly thrown, the scuffed left-hand side of the ball could induce low-resistance turbulence in the air passing by while the air will pass the smooth right-hand side in high-resistance smooth flow and the ball will veer to the left – toward the scuffed area! Since a deviation of a fraction of an inch can change a home run into a pop fly or a double-play ground ball, the controlled deviations a skilled pitcher can induce by disfiguring the ball are important (p. 40-41).

So, since Major League Baseball has cracked down on illegally modifying a baseball, the only hope for a pitcher who wishes to pitch with the advantages of a scuffed ball is for the scuff to come during regular game play, which is why so many baseballs are thrown out by the umpire – that, and there is enough money to go through 50-60 balls a game.