With Bill Belichick and Tom Brady both issuing strong denials, we still have no idea how 11 of the 12 game balls the Patriots used in the AFC Championship game got deflated.
Is Brady lying? Was a rogue ball boy involved? Did the balls magically deflate by themselves?!
Since the scandal broke the morning after the game, Patriots fans have been passing around a theory that the balls naturally deflated because of the cold weather.
It’s one of the only theories that can completely absolve the team of any wrongdoing. It’s also full of holes.
While a decrease in temperature would lead to a decrease in air pressure, it wasn’t cold enough during the game to account for the type of underinflation that was measured in New England’s game balls. In addition, the Colts’ game balls would have been underinflated too if it was all about the weather, but they weren’t.
By rule, NFL footballs have to be inflated to between 12.5 and 13.5 pounds per square inch. Each team brings 12 balls to the game and uses its own on offence.
Brady said at his press conference that he prefers the air pressure to be 12.5 PSI, and Belichick backed that up by saying the team’s policy is to inflate their game balls in the “12.5-pound range.”
Two hours and 15 minutes before kickoff, the officials tested the Patriots’ balls with a pressure gauge and they were all legal. But when the officials tested the balls at halftime, 11 of the 12 Patriots balls were at least two PSI below the minimum limit of 12.5, according to ESPN’s Chris Mortensen.
New England’s game balls went from 12.5 PSI to 10.5 PSI in a matter of hours. Importantly, all 12 Indianapolis game balls were still within the legal range when they were tested at halftime, according to SI’s Peter King and other reports.
And there’s the first problem with this theory: If you assume the weather caused a pressure decrease of two PSI, Indy’s game balls would have failed the test too, even if they were inflated to the maximum limit of 13.5 PSI before the game. That’s not what happened. Indy’s game balls didn’t deflate like New England’s did.
But for the sake of argument, let’s just forget about that for a second and ask the key question: could the cold weather have caused the balls to deflate?
Let’s turn to the science, specifically Gay-Lussac’s Law on pressure and temperature.
A bunch of writers and science people, from the Christian Science Monitor to WCSH6 in Maine, have run the numbers to see how the change in temperature would have affected the air pressure. In short, pressure is proportional to the temperature. The equation looks like this:
P1/T1 = P2/T2
We know the air pressure of the ball before the game was 12.5 PSI.
We know that the temperature outside at kickoff was 52 degrees Fahrenheit, an unseasonably warm night in New England. If we assume the ball was inflated in the locker room at a room temperature of 70 degrees Fahrenheit, the ball would have undergone a 18-degree temperature change.
Is 18 degrees enough to account for a loss of two PSI?
When you do the maths (accounting for atmospheric pressure and converting units to kilopascals and Kelvin), that temperature difference can only account for about ~0.9 PSI of deflation. As Boston College physics professor Michael Naughton noted, a 20-degree temperature change could account for a one PSI decrease in air pressure. But for the ball to decrease naturally by two PSI, it would have to undergo a temperature change of 40 degrees.
On the night of the game the temperature never dipped below 48.9 degrees before the balls were tested at halftime. For temperature to account for air pressure change, the balls would have had to have been inflated in an 90-degree room.
In conclusion: It wasn’t cold enough for the balls to deflate as much as they did. And even if it was, it makes no sense that the Patriots balls deflated more than the Colts balls.
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