The Myth of the 500-Foot Home Run

The conventional wisdom debunked.
Oct. 4 1997 3:30 AM

The Myth of the 500-Foot Home Run

Do men always exaggerate the length of their long balls?


On June 24, fans at Seattle's Kingdome witnessed one of the most dramatic pitcher-hitter confrontations since Walter Johnson faced Babe Ruth. On the mound, the Mariner's Big Unit, 6'-10" Randy Johnson, the tallest man ever to play in the majors, and the most proficient strikeout pitcher in history. At the plate, Oakland's Mark McGwire, the best and strongest home-run hitter since Ruth.


Although Johnson whiffed McGwire twice on the way to a record-breaking total of 19 strikeouts, McGwire hit what was estimated as the longest home run in at least a decade. He got all of a 97-mph fastball, and launched it at 105 mph in the general direction of Canada.

On the radio, Mariner announcer Dave Niehaus marveled, "A high fly ball, belted, and I mean belted, deep to left field, into the upper deck! My, oh my, what a shot by Mark McGwire! That is probably the longest home run ever hit here. ... It will be interesting to see how far that ball will be guesstimated. ... We have often wondered if McGwire got ahold of a Randy Johnson fastball how far he could hit it, and I think we just saw it."

Shortly after, Niehaus gave the estimated distance: "538 feet--unbelievable, absolutely unbelievable. The longest home run ever hit here in Seattle ... the longest home run I think I have ever seen hit." Not only that, it seems to be the longest ball hit since 1988, when the distance of major-league home runs was first estimated on a wide scale. Sports pages and broadcasters across the country are still heralding McGwire's homer as one of the great feats in slugging history.

But there's a catch: The 538-feet figure, announced by the Mariners about 40 seconds after the ball landed, was an overstatement worthy of P.T. Barnum. According to three physicists who have worked independently and have written extensively on the science of baseball, the human limit for hitting a baseball at sea level, under normal temperatures and with no wind, is somewhere between 450 feet and 470 feet.

Curious that anyone could hit a ball 538 feet in an indoor park near sea level, I called the Mariners to see how they devised such a spectacular number. The team repeatedly refused to explain how they arrived at the figure or to allow me to speak to whoever made the estimate. Mariners PR Director Dave Aust stresses that the figure is "a guesstimate." "We don't really believe in the process," Aust says, distancing the team from the McGwire number.

That "process" has evolved over time. In 1988, IBM established the "Tale of the Tape" program, devising a system by which home-run distances could be estimated. Sponsorship of the Major League Baseball-licensed program was assumed by telecom giant MCI in 1992 and redubbed the "MCI Home Run Program." The program's Web site lists the 10 longest home runs of the year and provides a searchable database of the home runs of the previous two years.

"We do not measure the home runs," says MCI spokesman Cal Jackson. The distances are estimated by the individual clubs and then provided to MCI. "We act as a warehouse for the numbers that Major League Baseball sends us."


U nsatisfied with the 538-feet number, I did my own figuring. I consulted the 1976 Kingdome blueprints, a more recent laser-survey diagram of the stadium, and the Seattle Times game story, and visited the park twice. Here are the facts: McGwire's homer landed in the eighth row of the left side of section 240 in the second deck--439 feet (measured horizontally) from home plate and 59 feet above the playing field.

How much further could the ball have gone? Based on a review of the trajectory charts in The Physics of Baseball and Keep Your Eye on the Ball: The Science and Folklore of Baseball, conversations with University of Puget Sound physicist Andrew Rex, and correspondence with aerospace engineer and baseball researcher Roger Hawks, I determined that the McGwire home run would have traveled about 474 feet. A mighty home run, yes, but still 64 feet short of the length claimed.



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