Guest post by Alec Rawls
Just fill the ball with warm humid indoor air, then when it temperature-equalizes with the 25°F cooler outdoor air on your AFC Championship playing field some of the water vapor in the ball will condense into water, leaving less air in the ball, solving the great mystery: how did the footballs used by the Championship winning New England Patriots show 12.5 psi of inflation pressure in the official pre-game check but only 10.5 psi when checked at halftime?
There is also a decrease in pressure due to the cooling of the molecules that remain gaseous. Those air molecules are not zipping around as fast as they were so they exert less outward pressure on the ball. But according to the ideal gas law, if there were no reduction in the number of gas molecules in the balls it would have taken a large drop in temperature, about 40°F, to cause the observed drop in air pressure. So says Boston College professor Martin Schmaltz:
In order for a ball to register a 10.5 PSI in a 50 degree environment [the temperature on the field at halftime] 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.
I verify Schmaltz’s calculations at the end of this post, and while I’m no expert in the field, I get the same answer he does.
It wouldn’t be hard to deliver balls to the pre-game pressure check with 91° air inside. Just inflate them in a 100° sauna shortly before testing, but the Patriots are adamant that they do not know why the air pressure in their balls was low at halftime and if they had inflated their game balls in a sauna they would certainly know it.
The Carnegie Mellon experiment
An experiment performed by a team at Carnegie Mellon provides empirical support for the Patriots’ claim to have done nothing unusual. The Carnegie experimentalists inflated a batch of footballs to 12.5 psi at a room temperature of 75°F, then let the balls equalize to a new ambient temperature of 50°F, resulting in an average pressure drop of 1.8 psi. (They also wet the leather balls to simulate the rainy conditions of the game, surmising that this might allow stretching that would reduce air pressure in the ball, but this seems likely to be a minor factor.) The Carnegie experiment is video-documented here:
So how to account for the difference between the Carnegie findings and the ideal gas law, which predicts that a much larger decrease in temperature would be needed to create the observed pressure drop? Barring experimental error, it seems that the difference would have to be explained by condensation. Gas was removed from the ball, not via an inflation needle but by conversion to liquid water. What do our blog-reading experts say? Is this the likely explanation?
The Carnegie group was not monitoring humidity (at least in the short video above), but if this is the explanation for their greater-than-ideal pressure drop then it could easily have happened to the Patriots the same way without anyone intentionally manipulating the inflation temperature or humidity. Still…
It must be common knowledge around the league that indoor inflation yields a softer game ball
The fact that the Colts’ balls did not show a similar pressure drop suggests that teams do know how to make these manipulations. Just as Patriots’ quarterback Tom Brady prefers to throw a less inflated ball, other quarterbacks
are known to prefer harder footballs.
If Colts quarterback Andrew Luck prefers a harder ball then all the Colts had to do is fill their balls pre-game with cool outdoor air. Ambient outdoor temperatures actually rose from pre-game to halftime so the temperature effect would have made their balls firmer. Also, moisture beyond what the cooler air could hold would never have made its way into the ball in the first place so wouldn’t there be any pressure-reducing condensation inside the ball either.
Players and equipment managers would surely have noticed over the decades how the conditions in which balls are inflated to regulation pressures affect ball firmness on the field. The basics are hard to miss. In cold conditions, inflate outdoors to get a firm ball, indoors to get a softer ball.
The existing pressure-test regimen, intentionally or not, leaves this room for teams to manipulate ball pressure to suit their preferences. The rule just says that air cannot be put into or removed from the ball after the pre-game pressure check. It does not regulate the conditions in which the balls are inflated going into the pre-game pressure check.
“Belichick rules”
If Coach Belichick had exploited this loophole to the max by inflating balls in the sauna then there would be a legitimate question whether this rule-bending constitutes cheating and there is plenty of history, both recent and ancient, to indicate that Belichick is eager to wring every advantage out of a loophole that he can. Where others may see exploiting loopholes as cheating, Belichick sees it as part of the game.
By the time he is done the NFL rule-book will contain at least a few “Belichick rules,” closing the loopholes he has so nicely pointed out, most recently by confusing the Baltimore Ravens about which Patriots players were eligible to receive passes. “It’s not something that anybody has ever done before,” complained Ravens coach John Harbaugh, “I’m sure the league is going to look at it and make some adjustments.”
Belichicks’ reward (besides a trip to the AFC Championship): he is now tied with Tom Landry for the most post-season coaching wins in league history, to which I say GO PATRIOTS! (That’s what you call “full disclosure.”)
But the full explanation in the present case seems to be that the Patriots filled their game balls with indoor air. If that is manipulation at all it must be utterly commonplace and well within the rules.
The biggest loser: Bill Nye, the phony-science guy
While real scientists keep acknowledging that the move from inside to outside can cause a substantial drop in football psi, Nye went on national television to proclaim that air must have been taken out of the balls with a needle. So that’s good anyway. Half the Northeast now knows that Bill Nye is an idiot.
Addendum: Gas law calculations
I was looking up how to calculate the expected pressure drop in a ball for a given temperature drop when I came across the claim from Boston College physicist Martin Schmaltz that, following the ideal gas law, temperature inside the balls would have had to be 91°F during the pre-game pressure check to account for the 2 psi drop in air pressure by halftime. In the exercise below I come up with a similar answer but I have no background in this stuff and am just following readily available information so don’t take my explication on authority (and please do note any inaccuracies in the comments).
When the number of gas molecules in a container is fixed (no gas escaping out through the bladder and no gas converting to liquid via condensation) then the ideal gas law simplifies to the general gas law, also called the combined gas law. Like the ideal law, the general law is said to be close to accurate so long as extreme pressures or temperatures are not involved. Mathematically, the general law just says that gas temperature, volume and pressure all vary in direct proportion to each other:
(P1V1)/T1 = (P2V2)/T2, where P1 is pressure at time 1, V1 is volume at time 1, and T1 is temperature at time 1.
In plain language, for the gas pressure in the Patriots’ footballs to drop by 7% the general gas law says that the temperature of the air in the balls must drop by 7% or the volume inside the ball must increase by 7% or there must be a combination of percentage changes in temperature and volume that add to 7.
The problem can be simplified further by assuming (as Professor Schmaltz does) that the volume of the space inside the football remains constant. (This won’t be fully accurate. When pressure in a ball drops the volume inside the ball will drop a small amount. This shrinking of the ball will make pressures higher in the low pressure state than they would be if the ball didn’t shrink so the constant-volume estimate of the temperature change required to account for the observed pressure drop will be a bit on the low side, unless the Carnegie experimentalists are correct and there is an offsetting increase in volume when the balls get wet.)
With fixed volume the general gas law becomes: P1/T1 = P2/T2
All of these numbers are known except for T1, the temperature of the air in the ball when it was first tested 2 hours before game-time. The known numbers just have to be converted from relative to absolute form.
First, the inflation pressures measurements are in pounds per square inch above atmospheric pressure, thus to get the full pressure inside a ball it is necessary to add atmospheric pressure (about 14.7 psi) to the measured psi.
Also, the gas law is based on degrees above absolute zero, which for Fahrenheit-sized degrees are “degrees Rankine,” which are Fahrenheit + 460. Solving for T1 in degrees Rankine:
T1 = (P1 x T2)/P2 = ((12.5 + 14.7) (50 + 460))/(10.5 + 14.7) = (27.2 x 510)/25.2 = 550.5°R = 90.5°F
Which rounds up to Professor Schmaltz’s 91°F.
Calculations for the Carnegie-Mellon experiment
In the Carnegie-Mellon experiment the expected post-equalization ball pressure, calculated just using the general gas law (where no gas is lost to condensation), is:
P2 = (P1 x T2)/T1 = [(12.5 + 14.7) x (50 + 460)]/(75 +460) = 25.9 psi
Subtract atmospheric pressure (14.7 psi) to get an expected pressure test reading of 11.2 psi, vs. actual experimental readings of 10.7 psi. The suggestion here is that the additional pressure drop found in the Carnegie experiment is a result of water vapor condensation.
If the Carnegie experimentalists were careful they would have compensated for the pressure drop that comes from energizing their pressure tester but game officials (who measured halftime pressure as 10.5 psi) might well not have taken this source of pressure loss into account. If they had the then the difference between their measured pressure drop of 2 psi and Carnegie’s measured drop of 1.8 psi might disappear.
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If all balls were inflated by a pump witha defective pressure gauge, that would explain thing, too. I’ve yet to read if anyone thought to test all the pump gauges…
It would be an interesting defective gage to only identify the Patriot’s footballs as being deflated. . . and reporting a normal pressure for all the Colt’s footballs.
The Patriots prepared their footballs, the Colt’s prepared their footballs. It’s more likely they used their own pumps and gauges than shared. The Pats like their footballs at a low pressure, the Colts like them high. Cool them down outside and I have no trouble with the ref’s gauge identifying only the Pats footballs as too low.
On the condesation issue, pulling out my trusty steam tables…
At saturation, 100Fsteam has a pressure of 0.9503 psig.
at 80Fthe pressure is 0.5073 psig
at 50Fthe pressure is 0.17803 psig
Partial pressure of moisture in air displaces the equivalent pressure of O2/N2, so a ball filled at 80F and 100% relative humidity would drop a little over 0.3 psi from condensation in addition to the pressure change of the non-condensables (no issue with that calculation) if it cooled to 50F. You could goose it a little more with warmer air, but the refs would probably notice the warmth of the ball at some point and (presumably) object.
If you assume room air at 72F and 50% relative humidity you get to roughly saturated conditions at 50F, so virtually no condensation.
In the end, humidity could contribute to a pressure drop, but wouldn’t be expected to unless the team is actively working to fill the ball with humid air.
Nicholas- It wasn’t the Colt player that detected the “soft” ball, it was the Colt equipment manager that he handed the ball to after an interception (and the Colts had been tipped about Pats use of “soft” balls by Ravens.
Jorge- The spin of an NFL forward pass would spread out any condensation inside the ball through centrifugal force, perhaps even evening out the natural imbalance of a hand sewn ball.
Smokey- A nine inning major league game uses far more than a couple of dozen balls. Even a single long inning with some foul-offs, pitches in the dirt, and a home run or two could go through a couple of dozen.
There is no centrifugal force.
I was born and raised in New England. The most interesting aspect of this case, to me, is the proclivity of fans to rabidly defend anything their team does, right or wrong. Belichick is a known cheater, yet the Patriots fans all stick by him and go to great lengths to try to rationalize his team’s unethical behavior. One of the many reasons why today’s NFL makes me puke.
How is Belichick a “known” cheater? Deflate-gate has now been determined to be only about 1 pound, which is explained by temperature fluctuation. In Spy-gate all he did was film during a game – the same thing 80,000 other people could have been doing as well. I would hardly call that cheating. I am also sure that all the other teams bend rules every bit as much as Pats, but are not called out because they lose. This leads me to say that the only thing all of this cheating hub-bub has actually proven is “Sour Grapes.”
Charlie, exactly it is all just cry babies who don’t like to see their team lose to the Patriots and I’m a Giants fan so I have nothing in this. The more I learn about Belichick the more impressed I am about his intelligence.
This has been a “rule following” problem in the past. Going forward there is such an easy remedy to this issue, unless the NFL and the Media and the Masses simply enjoy all the hub-bub (similar to the reason narcotics are kept illegal). The NFL already lets each team provide their own balls, so, very simply, just let each team provide their own desired air pressure in the balls, then everybody is happy, with no policing of pressure required. Is that too easy or does everyone just want to force others to follow more petty rules.
How the balls were inflated is as important as where. Let’s say that, being the NFL, they have a compressor for the balls. Let’s further assume that the compressor leaks ‘just a little’, like most compressors do. When you compress air, you heat it by adiabatic compression. You also concentrate moisture, but I’m not as inclined to buy into that one. Anyway, compressors are noisy, so people are inclined to unplug a leaking compressor. When you plug it back in, it will contain hot air when it finishes running. Mystery solved. No violation of the rules involved. Further, it is not even necessary for the Patriots to intentionally do this, although I’m guessing such knowledge as this is common in the NFL.
Rule 2 The Ball
Section 1
BALL DIMENSIONS
The Ball must be a “Wilson,” hand selected, bearing the signature of the Commissioner of the League, Roger Goodell. The ball shall be made up of an inflated (12 1/2 to 13 1/2 pounds) urethane bladder enclosed in a pebble grained, leather case (natural tan color) without corrugations of any kind. It shall have the form of a prolate spheroid and the size and weight
shall be: long axis, 11 to 11 1/4 inches; long circumference, 28 to 28 1/2 inches; short circumference, 21 to 21 1/4 inches; weight, 14 to 15 ounces.
The Referee shall be the sole judge as to whether all balls offered for play comply with these specifications. A pump is to be furnished by the home club, and the balls shall remain under the supervision of the Referee until they are delivered to the ball attendant just prior to the start of the game.
Section 2
BALL SUPPLY
Each team will make 12 primary balls available for testing by the Referee two hours and 15 minutes prior to the starting time of the game to meet League requirements. The home team will also make 12 backup balls available for testing in all stadiums. In addition, the visitors, at their discretion, may bring 12 backup balls to be tested by the Referee for games held in outdoor stadiums. For all games, eight new footballs, sealed in a special box and shipped by the manufacturer to the Referee, will be opened in the officials’ locker room two hours and 15 minutes prior to the starting time of the game.
These balls are to be specially marked by the Referee and used exclusively for the kicking game.
In the event a home team ball does not conform to specifications, or its supply is exhausted, the Referee shall secure a proper ball from the visitors and, failing that, use the best available ball. Any such circumstances must be reported to the Commissioner.
In case of rain or a wet, muddy, or slippery field, a playable ball shall be used at the request of the offensive team’s center. The Game Clock shall not stop for such action (unless undue delay occurs). Note: It is the responsibility of the home team to furnish playable balls at all times by attendants from either side of the playing field
Although the rule is explicit about the pressure requirement when the balls are submitted for Referee’s inspection, it doesn’t appear to speak to maintaining that standard throughout the game. If the Patriot’s cannot be shown to have deliberately interfered with the balls’ inflation after they were inspected there is no violation of the rule.
If they wanted to be really clever they could pick a pure single element gas that has a more dramatic temperature response curve than atmospheric air and use that to inflate their balls as the rule, somewhat clumsily, defines the inflation pressure it doesn’t seem to address what the inflating gas must be.
Unfortunately football is becoming virtually unwatchable due to the burgeoning growth of ever more arcane rules and penalties. What the game needs is a dramatic reduction in rules, not another large addition
Interesting analysis. So the balls could have been inflated with heated air prior to the ref’s inspection. Yikes!
The most damning evidence , however, that there was something amiss comes from the study of fumbles after the football rule was instituted. NE Patriots had a simply phenomenal decrease in fumbles following the imposition of the rule. Coincidence?
“If the Patriot’s cannot be shown to have deliberately interfered with the balls’ inflation after they were inspected there is no violation of the rule.”
Exactly, that is the brilliance in this.
The NFL has admitted that the initial PSI was not recorded. That would be an issue.
Maybe they should’ve surgically detached the pig first, or told it to hold it’s breath for the
duration of the game.
My ol man once went to an “American Football” game, I asked him what he thought,
he said the people inside the stadium were marginally dumber than those outside,
and the hot dogs were cold and tasted like they were made in a factory or something.
Regarding the pressure drop due to condensation: wouldn’t you have to take into account the latent heating of the air associated with the condensation? This would increase the internal temperature of the ball and perhaps offset some of the pressure drop due to the loss of water vapor.
Time for the other half of the Northeast to know how much an idiot is Bill Nye.
http://www.funnyordie.com/videos/3d0c94936c/bill-nye-addresses-deflategate
Leather stretches when wet.
The best way to break-in a new pair of hunting boots is to soak them a day or so in a tub of water. Then wear 2 pair of thick cotton socks at a time and wear until the boots until dry. You’ll need to change the socks often. When done your boots are ready for those 15 mile treks over rough mountainous terrain for the life of the soles. My Danners last about 3 soles. A day or so of wet feet sure beats blisters.
And, today’s headline is:
“WEEKEND: NFL officials will hold balls before Super Bowl…” 😉
Seahawks player fined for grabbing his balls!
Officials measure and hold everyone’s balls!
Super Bowl 50 is all about BALLS!
Watch the half time show for more!
What if we assume there was a nefarious intention to have an undetected under inflated game ball… most people are assuming that the balls would have had regular air in them… of course nobody wants to get caught doing this… and yes… someone above suggested helium… which makes me think… The valve and membrane of the football are not made to contain helium gas… so suppose a ball was partially filled with ten to twenty percent total ball volume of helium gas… then the ball was filled to 12.5 pounds overall pressure with regular air on top of the helium… maybe would the helium will leak out in the time after the balls are checked by game officials but before the game is played leaving an under inflated football without anyone having to let any of the air out… no need to use a sauna or anything exotic… perhaps just just party store helium… then after the game if anyone checks the air for consistency the regular air will be all that is left in the ball because the helium will have leaked out.
This is fairly chewing out of the media for falling all over each other for this story.
http://tanyarayfox.weebly.com/blog/how-the-nfl-made-a-fool-of-you-with-deflategate
Small excerpt:
You bought it hook, line and sinker because you’re under the delusion that your team is all clear eyes-full hearts and has somehow been victimized by this. It is one thing to buy into a perfectly timed PR stunt. It’s another thing entirely to fall into the ignorant space between conspiracy and reality that enables you to continuously denounce the NFL and its most successful franchise as cheaters and liars, yet still voraciously consume their product that they’ve pitted you against.