I found an old story (4 Oct 04) about Jack Tatum's involvement in one of the NFL's most famous plays. If any of you are physics majors you may find it interesting.
Pigskin physics and the Immaculate Reception
New book takes a look at the science of the game, and tackles the mystery of the Immaculate Reception
Monday, October 04, 2004
By Byron Spice, Pittsburgh Post-Gazette
Donald Stetzer, Post-GazetteThis photograph of the Dec. 23, 1972 Steelers-Raiders game was altered for publication to diagram the collision of Oakland's Jack Tatum and Pittsburgh's Frenchy Fuqua (left) as Terry Bradshaw's pass headed for Fuqua. In the collision, the ball was deflected back toward Franco Harris, far right, who caught it at the X then headed for the end zone.
Click photo for larger image.
Could physics help settle the 32-year-old controversy regarding the Immaculate Reception?
Timothy Gay can't say for sure. But the more the University of Nebraska-Lincoln physicist thinks about it, the more he suspects it might.
The trajectory of the ball that landed in the hands of Franco Harris that frozen December day might provide a hint as to whether it bounced off Steeler Frenchy Fuqua or Oakland Raider Jack Tatum ---- the key factor determining if Harris' catch was fair.
"In principle, you could reconstruct it," Gay said in an interview last week. "But it's gotta be pretty tough to do."
If anyone would know what was possible, it would be Gay. He's developed a reputation as the leading authority on the science of football, thanks to his one-minute physics lessons that have played on stadium video screens during Cornhuskers home games since 1999 and television segments he produced for NFL Films.
And Gay, 51, has studied the Immaculate Reception in great detail. In a new book, "Football Physics: The Science of the Game," published by Rodale Inc., Gay dissects it in the opening chapter.
Gay doesn't claim to have solved any mysteries in the chapter, provocatively titled "The Steelers Get Lucky," but relates the tale of that Dec. 23, 1972, playoff game because it illustrates many principles of physics.
"It is just a classic play in football."
With 26 seconds left to play and the Steelers trailing by a point, Terry Bradshaw scrambles on fourth down, then desperately rifles the ball to Fuqua, his running back. The ball arrives at the same time as Tatum, the Raider free safety who breaks up the play and sends Fuqua flying. The deflected ball, however, flies backward and into the hands of Harris, who runs untouched into the end zone for the winning touchdown.
Harris' catch was ruled fair, on the assumption that it bounced off Tatum. But if the ball actually hit Fuqua, the catch would have been illegal under NFL rules at the time.
It's an oft-told tale, but Gay focuses on the physical principles at play. The primary reason that the game turned into a defensive battle was because large swaths of the artificial turf at Three Rivers Stadium were frozen. That, he said, illustrates the impact of frictional forces, or the lack of them.
The pass itself displayed the effects of angular momentum and impulse. That it even made it to Fuqua's vicinity owed something to Bradshaw's throwing technique, Gay said.
"Bradshaw had a really unique way of throwing" ---- holding the ball at its back and placing his index finger on its tip, he said. Thanks to that finger, "he's got a more effective push on the back of the ball than some quarterbacks who throw it more to the side," he added.
The Pittsburgh SteelersFranco Harris heading into the end zone for the winning score.
"Bradshaw had the ability to really rocket the ball," but the technique also was the reason his passes were often less than beautiful spirals and not always easy to catch.
Tatum's hit on Fuqua, on the other hand, was an example of the conservation of momentum, one of the fundamental laws of physics. Momentum, what Newton called "the quantity of motion," is calculated by multiplying a body's mass times its speed.
The conservation law holds that when two bodies ---- players, in this case ---- interact, the sum of their momenta will not change. Put another way, one player gains exactly as much momentum as is lost by the player that strikes him.
It's like the toy called Einstein's balls ---- five metal balls in a row suspended by strings. When one metal ball is lifted and allowed to swing back against the others, its momentum is delivered as an impulse that sends the ball on the other end of the row swinging.
"Jack Tatum was an incredible tackler," Gay said. "He always showed perfect form." Once he got Fuqua in his sights, he built up his speed and plowed right through the running back. "Tatum delivers all of his momentum to Fuqua," so effectively that he was left standing and (temporarily) smiling as Fuqua went flying.
A mystery for the ages
No good film exists to show which player might have deflected Bradshaw's bullet. Tatum insists he never touched the ball. Fuqua has vowed never to reveal who did.
Gay didn't analyze the play with any expectation of solving that mystery, though as a longtime fan of the Raiders, he wouldn't mind turning up evidence to support Tatum's claim. He also grew up in western Ohio, rooting against the Steelers while cheering for the Cincinnati Bengals. Still, the evidence seemed just too scant.
But last week, he wondered if perhaps the ball's trajectory might offer a clue.
"Somebody's momentum was transferred to the ball," he explained.
In his own laboratory, Gay routinely analyzes atomic collisions by studying the trajectories of the subatomic particles they generate. In the same way, it might be possible to analyze the flight of the ball in relation to the momenta of Tatum and Fuqua.
"It's the sort of thing people do when reconstructing automobile accidents," he said. The Tatum/Fuqua collision analysis might make a good student project, he added.
Even if his book doesn't challenge any of the mythology surrounding the Immaculate Reception, Gay said it did allow him to expand upon his earlier explanations of football physics in more detail and clarity than is possible during a football time-out.
Books already exist about the physics of baseball, soccer and golf. "I wondered why hasn't anyone written a book about the science of football," he said. "It seemed to me that was odd because there's every bit as much physics in football as in baseball."
In fact, the physics of football is far more complicated than that of baseball because of the larger, more aerodynamically complex ball. The flight of the ball is a particularly intriguing one for many physicists, he said. "Someone said this isn't rocket science, it's a lot more difficult than rocket science."
Gay recalled how one faculty meeting came to a halt for an hour while the physicists argued about the trick that some players perform after a touchdown ---- spinning the ball on its side, making it stand up on end.
"Why does it stand up?...It's not a trivial thing."
One thing physics can't do is predict which team might prevail. "Physics puts constraints on the game," he explained. "But it can't say anything about heart or instinct."
http://www.post-gazette.com/pg/04278/389980.stm
