Football, Physics, and Symmetry

September 16, 2019

When people talk about the physics of American
football, they normally mention force, torque, and so on… Like how the energy from two
linemen colliding is enough to power a 60W light bulb for over a minute, or is equivalent
to an average person falling two stories off of a building! But there’s another aspect of physics in football
that isn’t talked about as much – symmetry! You might think symmetry is just for butterflies
and rorschach tests, but it’s all over the place in football: there’s translational symmetry
when teams keep the same formations as they move up or down the field, and rotational
symmetry when they switch sides after a touchdown. Even the ball has axial symmetry so it can
spin smoothly through the air. But why is symmetry useful in the first place?
Symmetry makes things easier, or at least more efficient; it gives you a guide: “same
scenario, same action.” That means you don’t have to reinvent the wheel all the time: to
draw a straight line, you just keep drawing in the same direction. For a circle, keep
curving the same amount. So when football players practice a play over
and over, the patterns of football become so ingrained in their reflexes they can act
without thinking. Psychologists call this “habit formation”; we call it “symmetry in
time”! And when players line up on the field the same way at the thirty, or forty, or fifty
yard lines, that’s “symmetry in space”. Even physics itself is symmetric – ever
heard of Newton’s law: “a body in motion tends to stay in motion”? That’s just nature saying
“keep doing the same thing.” What’s more, Newton’s laws of motion are the same now as
they were yesterday, and they’ll be the same again tomorrow! Doesn’t that make life easy? Ultimately, symmetry is what allows both science
AND football to function – if the laws of the universe (or the rules of football) changed
from day to day, we wouldn’t be able to repeat experiments, make predictions, or know what
plays to practice. So when you reach for yet another handful
of chips while watching the next football game, know that millions across the country
are doing exactly the same, in perfect symmetry.

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