Apple #356: The Football's Shape

Today I went with a friend to the Pro Football Hall of Fame.


The entrance to the Pro Football Hall of Fame. And yes, that's a football-shaped dome on top. It looks really cool on the inside. I'd like one just like it in my living room.
(Photo from Destination 360)


I was expecting that much of what I'd see would be enjoyable only to football fanatics, the sort of people who could debate at length which team would win: the 1972 Miami Dolphins, the 1976 Pittsburgh Steelers, or the 1986 Chicago Bears; or perhaps who was the be defensive player, Dick Butkus or Carl Eller. Not so. In fact, the only reason I can provide you with these details is because I learned about these teams and players from having been to the Pro Football Hall of Fame.

They did an excellent job of describing individual players and their achievements, the history of teams extinct and extant, key games in the history of football, and spectacular or even boneheaded plays. There were jerseys that had been worn by players from the past and present, there were shoes, there was even the cast of a barefoot placekicker's foot. I learned a great deal -- something your Apple Lady always enjoys -- and I had a good time. I recommend making the trip.



This is the Hall of Fame room, sort of the centerpiece of the whole museum. The bronze busts were actually kind of cool to look at, to see who I recognized, and whether I thought they looked lifelike or not. There's also a multimedia system that goes along with this where you can look up individual players or teams or positions and see who's got a bust on the wall and learn more about them. For example, here's the list of Hall of Famers by college. See other lists by mousing over HALL OF FAMERS at the left of the top banner.
(Photo from the Pro Football Hall of Fame)


One thing I was hoping to learn which they did not discuss, however, was why the football is shaped the way it is. I guessed that the football got its shape from the ball used in rugby, but I wanted to find out for certain.

• The short answer is, I was right. The ball used in American football is based on the ball that was used in rugby.

• The earliest football games -- I should probably call them precursors to football as we know it today -- were played at Ivy League colleges in the 1860s and 1870s. The sport they played was mostly based on rugby's rules, but it was also a unique brand of American rugged play that allowed for "roundhouses and uppercuts" before and after the ball was snapped.

• Harvard's three-game match against Yale in 1875 is generally considered the first American football game. Most of the rules were still rugby-like, though.

 

 
Program from the Harvard-Yale football games in 1875. That ball sure looks round.
(Image from Snipview)

• It wasn't until 1880 when Walter Camp from Yale proposed that there ought to be a line of scrimmage where the ball would be placed when it was last downed, and that the ball must be advanced 5 yards in 3 plays or else the team with possession had to give it over to the other team. That's really when football as we know it was born.

• It's important to know that our football is a descendant of rugby because that means that the first footballs were actually rugby balls.

• So the question then becomes, why were rugby balls shaped like that? Answer: they were actually pig bladders.

• That's right, rugby balls were made by inflating the bladders of freshly dead pigs. The shape of the ball was determined by the size and shape of the pig's bladder.

A rugby ball from the 1880s or 1890s. When this was sold as an antique, it was described as being "melon-shaped." The description says it was quite small, and rugby balls from that time tended to be small and to vary in shape because they depended on the size of the pig's bladder inside. Which would suggest that this one does have a pig's bladder inside.
(Photo from the Busacca Gallery)

• Two enterprising boot and shoemakers who had shops near the Rugby school hand-stitched the rugby balls from pigs' bladders. The bladders were sometimes inflated by use of a clay pipe and sometimes directly by the mouth. Ew.

• The pig's bladders were inserted into a leather case, which was then tightened closed around the bladder with laces.

• By the 1860s, rugby-ball-makers were using leather instead of pig bladders for the rugby ball's innards.

• Over the years, the rugby ball became more oval in shape because that made it easier to carry. It also went through lots of changes in the materials used so that today, a rugby ball is made mostly of synthetic materials -- plastic, polyurethane, polyester, latex, and glue.

• The American football came on the scene after the rugby balls were made of leather, but still in basically the pig-bladder shape. They, too, had a leather bladder that was inflated inside a leather casing that was then tightened using laces.

 

Football from the 1890s. It's not quite as rounded as the early rugby ball, but it's not as oval as footballs are today.
(Photo from The 1890s Weekend at Mansfield (PA) University)

• Today, the American football is still made in essentially the same way, with a bladder on the inside that is inflated within an outer casing.

 

The basics of a football's construction today.
(Diagram from How Products Are Made)

• And, by the way, that's why people refer to a football as "the pigskin," even though it is not and never was made from pig skin. Because the rugby ball used to be.

• The particular shape of a football is referred to as a prolate spheroid. That means the ball is round-ish, or based on the concept of round, but with a polar diameter longer than its equatorial diameter (taller than it is wide).

• Except the football is even an exception to this, because with a true prolate spheroid, the longer ends would be rounded. But a football has pointy ends.

• Here's one last fact about the football: with most balls that are round, one can predict relatively easily where they will bounce. With a football, however, the only time a football will bounce straight back up vertically is if it lands exactly on one of its points. But because of its odd shape, the rotation of the football can change dramatically after it has bounced -- even if it has landed exactly on one of its pointy ends -- so it is very difficult to predict where it is going to go once it has hit the ground.

• More often than not, one physicist has stated, a football will bounce away from the person who has dropped it.

• Which is how you get this kind of thing (41 seconds into this):

For more about the physics of football, The Physics of Football: Discover the Science of Bone-Crunching Hits, Soaring Field Goals, and Awe-Inspiring Passes, by football fan and physicist Timothy Gay.


Sources
Pro Football Hall of Fame
Bruce K. Stewart, American Football, November 1995
How Products Are Made, Volume 3, The Football
Anthony Mann, The Rugby Ball, Manchester Guardian, November 1998
Sean Fagan, RL 1908, Rugby Balls
RugbyFootballHistory.com, The Ball
Mary Bellis, History of Football, About.com: Inventors
Pete Grathoff, "The Football," The Kansas City Star, September 1, 2008