Science! One Way To Deflate a Football Without Even Touching It

This D’Qwell Jackson interception prompted the Colts to question whether the Patriots were using an underinflated ball or not.
This D’Qwell Jackson interception prompted the Colts to question whether the Patriots were using an underinflated ball or not. –The Boston Globe

Get Patriots game stats and the inside scoop on the season with The Boston Globe's Point After newsletter delivered for free to your inbox.

The Patriots did not necessarily have to alter or deflate the football in order to beat the system and play the AFC Championship Game with footballs that were easier to grip and catch.

Martin Schmaltz, a Professor of Physics at Boston University. —Boston University

Martin Schmaltz, a Professor of Physics at Boston University, explained the truths and myths of Deflategate to, and helped outline a theory where the Patriots could have easily passed the NFL’s pregame tests with the same footballs that failed to meet the league’s mandated standards at halftime.

“One complication with the pressure units that we usually use, in this case PSI (Pressure per Square Inch) is that we are measuring the pressure above the atmospheric pressure,’’ Schmaltz said. “Air at a fixed volume- and I assume the size of a football stays pretty much the same whether it has a PSI of 13 or 11- if the size stays the same, and you change the temperature of the air, the pressure inside the football changes as well.’’


The key question, as outlined by Schmaltz, is where the balls were tested prior to the game. If the balls were tested indoors, where the temperature was likely above the 50 degree temperature outdoors Sunday, then the pressure inside the ball would drop once the ball is moved outdoors and begins to cool off.

“If they had inflated the balls inside the building and put it to the minimum amount, and then brought it outside to temperatures that were about 30 degrees lower, that would drop the PSI by between 1 and 2,’’ Schmaltz explained.

According to Schmaltz, once the temperature of the air inside the ball drops to the temperature of the air outside the ball, the PSI would be changed. Schmaltz estimated that it would take no more than 30 minutes for the temperature of the air inside the ball to acclimate to the temperature of the air outside.

“After the game, if you take the ball inside to a commissioner’s office or another warm place, the air in the ball would warm up again and the PSI would go back up,’’ said Schmaltz.

If the balls were inflated, stored, and tested outside in 50 degree weather, there’s no explanation for how the PSI could drop so significantly. Schmaltz also debunks Tom Brady’s claim that Rob Gronkowski can deflate a football by spiking it. According to Schmaltz, the wear and tear of the football game will have minimal impact on the air pressure inside the football.


Taking Schmaltz’s expertise and applying it to the weather situation from Sunday, we were able to outline how the Patriots could have altered the PSI of the football if they were able to submit the balls for testing without exposing them to the open air for a significant amount of time.

If the Patriots inflated, stored, and/or tested the balls by filling them to 12.5 PSI in a 70 degree environment, the PSI of the balls would drop by about 1 after half an hour outside in a 50 degree environment, according to Schmaltz.

However, the NFL found that 11 of the Patriots 12 balls were “underinflated by about 2 pounds each.’’ In order for a ball to register a 10.5 PSI in a 50 degree environment but register a 12.5 PSI in the testing environment, the ball would have to have been inflated, stored, and/or tested in a 91 degree environment.

Schmaltz reasons that “about 2 pounds’’ means that the balls were likely somewhere in the 1.6-2 PSI below standard range. In that case, the balls would have to have been inflated, stored, and/or tested in an environment that was at least 82 degrees.

Of course, this all assumes that the Patriots’ balls registered the minimum 12.5 PSI when they were tested by the NFL. It also assumes that the NFL doesn’t mandate the balls be left outside in the open air for a half hour or so to get an accurate reading on the PSI of the ball at game temperature.

It’s not obvious to think the Patriots would keep their footballs in a heated environment to help beat the test and make their footballs a little bit easier to throw and catch. But if Bill Belichick is as diabolical as some people say he is, and the Patriots’ organization is fully committed to bending any rule they can to achieve a competitive advantage, then it’s possible.


Looking over the NFL rules on the ball, there’s nothing in the rule book stating what temperature the balls have to be tested at. That’s one of the loopholes the NFL will need to address when it reviews Deflategate and adapts to prevent it in future seasons.

New reports have stated the Colts first suspected the Patriots were using underinflated footballs in Week 11, when the teams played indoors in Indianapolis. That suggests, as many people suspect, that the Patriots have gotten away with bending these rules before.

In the event that they haven’t, however, and that the AFC Championship Game was an isolated incident, the Patriots may have exploited the rule and softened the football using good old-fashioned science.

Loading Comments...