Saturday, January 24, 2015

PSIchic warfare

The way footballs apparently work in NFL games is that each team supplies the footballs that they’re going to use on offense, and is allowed to have scuffed them up as much or as little as they want. Officials test the pressure 2 hours before the game, at which point it has to be 12.5 to 13.5 PSI. That’s a fairly tight range of just 1 PSI.

But Tricon Sports demonstrated that a temperature change of 25 degrees will cause a change of 1.5 PSI in an NFL football. And because the air bladder in an NFL football is somewhat insulated, the temperature change (and corresponding PSI change) will not happen immediately.

So if you want to have the PSI on the low side (as Tom Brady prefers) and you want to have it drop further, inflate the ball with warmer air than the game environment. If you want to have the PSI on the high side (as Aaron Rodgers prefers) and you want to have it rise further, inflate the ball with colder air than the game environment. Since the locker room has everything from ice baths to saunas, different temperatures are easy to find.

So without any deliberate shenanigans, if you inflate the ball in a 70 degree equipment room and then take it out to a 20 degree stadium, expect a drop of 3 PSI. That’s a much larger change than the 2 PSI that everyone is screaming about with #deflategate, and it’s going to happen in plenty of games.

Requiring that the ball be filled with field-temperature air (not a current requirement) would result in less PSI change, though the temperature on the field can still easily change quite a lot over the 5+ hours between when the balls are checked and the end of the game. A game ball simply isn’t guaranteed to stay in a tight PSI range unless you keep adjusting it.

A real football isn’t a challenge to throw and catch because it’s inflated to a ridiculous air pressure, and underinflating it doesn’t turn it into a Nerf ball. The PSI standards are there because that makes the football behaves the way people want it to behave, and the allowed initial range recognizes that this is not precision machinery. Do people then get irrationally picky about the exact PSI or the way the balls are scuffed or the color of their shoelaces? Sure. But this isn’t like stealing your opponent’s playbook or replacing the other team’s Gatorade with vodka. This whole scandal seems more appropriate for Mythbusters than for CSI.

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