Baseball is a game of trajectories. And as Yogi Berra supposedly said, you can observe a lot just by watching. For example, at Yankee Stadium on May 29, I observed New York slugger Alex Rod­riguez hit a pitch by Cleveland Indians David Huff back up the middle and off the pitcher’s head. In fact, the ball hit Huff’s head so hard that it rolled nearly all the way to the right-field wall. The ball, that is, not Huff’s head. He collapsed in a heap and remained face down on the mound for several minutes. Huff eventually left on a stretcher. Home team fans who then watched the Yankees blow a six-run lead left in a huff.

Anyway, many in the crowd feared that Huff was seriously injured. Having observed physics teachers years earlier, however, I was guardedly optimistic—precisely because the ball had ricocheted so far and so fast. Had the ball rebounded from Huff’s dome only a few feet straight back toward home plate, I would have been concerned that the poor pitcher had become the second player in major league baseball history to be killed on the job. In that scenario, much of the ball’s energy of motion would have been imparted to the pitcher. But said energy appeared to have been expended on sending the ball skittering into the right-field corner, with only a small amount having been transferred to Huff’s head.

Indeed, after being checked out at nearby New York–Presbyterian Hospital, Huff returned to the scene of the bean, seemingly little the worse for wear, before the game was even over. He was helped in this effort by the fact that the 13–11 Indians win took an excruciating four hours and 22 minutes, which felt much longer for those of us near the event horizon.

(The only man killed playing major league baseball is Cleveland Indians shortstop Ray Chapman, who, after being struck in the temple by a pitch from Carl Mays of the Yankees in 1920, never regained consciousness. A scant 51 years later the powers-that-were made protective headgear mandatory.)

On the same afternoon as A-Rod’s double off Broca’s area, a far more serious injury was sustained by Kendry Morales, first baseman for a team somehow seriously referred to as the Los Angeles Angels of Anaheim. Morales hit a game-winning grand-slam home run in the bottom of the ninth, trotted around the bases, leapt onto home plate and shattered his left ankle. He’ll need surgery and could miss the rest of the season. Morales is still lucky compared with other world-class athletes that after similar injuries used to be taken out back and shot and more recently are euthanized by large-animal veterinarians.

That same evening Philadelphia Phillies pitcher Roy Halladay pitched the 20th perfect game in major league history, retiring all 27 Florida Marlins who futilely waved their tribute sticks, I mean bats, at him. The Philadelphia Inquirer’s Bill Lyon wrote that Halladay “made the ball dive, and he made it rise.”

Lyon is hitting .500. No pitcher throwing overhand can really make the ball rise, says University of New Hampshire psychology professor Kenneth Fuld, who has taught a course called Visual Perception. (New Hampshire was where I came closest to playing professional baseball, when I was given room and board for a week so I could be a ringer on the Dartmouth College math department softball team. Given sufficient initial conditions, those guys could tell you exactly where an opponent’s batted ball would land when, in keeping with math department tradition, they didn’t catch it.)

According to Fuld, whose son, Sam, is an outfielder on the Chicago Cubs’ 40-man roster, straight fastballs delivered overhand always drop slightly on their way to home plate. But the batter perceives the trajectory as level. An unusually fast pitch, which drops merely less than expected, will then appear to rise. It’s an illusion, like when you think your stationary train is moving because a train on the next track moves or when paying six bucks for a hot dog at Yankee Stadium doesn’t seem at all crazy, because you already shelled out $125 for your seat.