The Physics of the Curveball

I received this interesting article from my father-in-law related to the physics of baseball from the August 13, 1883 edition of The New York Times. It reads:

THE CURVE BALL
From the Lancaster Penn. New Era Aug 11

Under the new method in base-ball many players have become adept at pitching what is styled the "curve" ball, delivering the ball toward the batter at what he regards the desired height but which, when nearing the home plate, through the power of a curve or twist given it by the pitcher, either drops or goes up or out from the plate, puzzling the batsman, and often preventing him from hitting the ball at all. Mr. Robert J. Houston made an offer of $10 to any person would accomplish a test experiment which he would give him. The challenge was accepted by Hofford, the Ironsides pitcher, and Mr. Houston, accompanied by a number of friends and Messrs. Hensel, of the Intelligencer, Pyott and Allen A. Gerr as judges repaired on Friday afternoon to the rear of the Lancaster cemetery to have the vexed question settled. The test prescribed was to pitch a ball on the opposite sides of three posts placed in a straight line, the one 25 feet from the first and the other 22 1/2 feet from the second; in other words, to pitch the ball on the left side of the first, the right side of the second, and left side of the third, describing a snake-like action and proving the existence of the curve. For a number of attempts Hofford failed to get the ball to curve from the second post to the proper side of the third, the ball frequently striking the second post. Finally he got it around to hit the third post, and with a few more efforts accomplished the task to the satisfaction of everybody present. Mr. Houston promptly handing over the reward.

Of course the question of just who invented the curveball has been the subject of some debate with the two most prominent figures being Candy Cummings, who claimed he thought of the idea in 1863 as a boy watching thrown clam shells curve, and Fred Goldsmith who made the first public demonstration of the curve on August 16, 1870 some 13 years before this article and using the same experiment. While it seems interesting at first that the question was still an open one over a decade after it had been shown, keep in mind that the question was still being debated in the 1930s and 40s and it wasn't until 1959 that Lyman Briggs, using wind tunnel experiments, showed scientifically that the ball curves and how far.

But what's interesting is that Briggs' experiments, and as discussed by Robert Adair in the book The Physics of Baseball, showed that a curve ball only deviates from the straight line drawn from the pitcher's release point to the point at which it crosses the plate by around 3.4 inches (when viewed from above) and all the while moves in a smooth arc. This is the reason that Hofford the pitcher had such difficulty in getting the ball to get around the second post. There simply isn't much margin for error in trying to throw a ball that is a shade under 2.9" in diameter. However, as seen from the pitcher's and batter's perspective the ball curves some 14 to 17 inches with half of the deflection coming in the last 15 feet or so. This is why Hofford, once he was able to traverse the second post, had an easier time with the third. Interestingly, as Adair says, "neither the smooth arc nor the break is an illusion but a different description of the same reality."