PBPF did you ever hear back from that Columbia Professor?

Fencer said:

@tom.kordis Why would a water bath be a good model for rain-filled air? I imagine the thermal conductivity of the two is very different.

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As I said above, I wasn't looking to create a model good enough to capture the temperature/pressure transients. Just the steady state end-points.

And then I wanted to check if I were justified in concluding that the shortest immersion time ball HAD reached steady state, which was the purpose of the multiple immersion time parameter. (This showed that it had done so.)

It ain't a perfect model, but that's not what I was trying for. This was a fairly typical screening test, simply to check end points & get a feeling for the time constants needed to capture the dynamics.

But, at the same time, it ain't that bad a model, either. Think about the thin layer of water on the outside of the ball. The experiment needs to get the temperature of that layer correct, and then everything inside that boundary will track correctly.

In the rain, the water on the outside of the ball is getting CONSTANTLY replaced with a new layer of cold water.

If one were to soak a cloth & wipe the outside of the ball, then the heat emanating from the ball will warm up that thin layer pretty quickly, and the dynamics would be wrong.

Immersion is a quick & dirty approximation of a "constantly replaced layer of cold water on the outside of the ball". When the ball is skidding across the grass, after an incomplete pass (Yes, I know that TB12 doesn't throw many of those!), or after a tackle, then it's a closer approximation.

If I were tasked to write a test protocol to examine this event accurately (capturing both steady state & transients), this is exactly the type of screening test I'd run first, just to figure out the data acquisition rate required.

In a final test, I'd get an immersion pump, a flow control valve, a shower head & I'd spray the balls from my cold bath.

But the tests ARE good enough to support the steady-state conclusions that I've stated.

Does that answer your question?

tom.kordis said:

One minute in 48°F water, blot dry with a towel, 9 minutes in a 50°F refrigerator

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Do we know what the likely temperature of the rain was? Any meteorologists around that could answer that?

Could there also have been some evaporative cooling given the wind? Or does the high humidity preclude that?

tom.kordis said:

Think about the thin layer of water on the outside of the ball. The experiment needs to get the temperature of that layer correct, and then everything inside that boundary will track correctly.

In the rain, the water on the outside of the ball is getting CONSTANTLY replaced with a new layer of cold water.

If one were to soak a cloth & wipe the outside of the ball, then the heat emanating from the ball will warm up that thin layer pretty quickly, and the dynamics would be wrong.

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I keep putting this out there as a minor x-factor and hoping a better head than mine will know what to do with it.

Brady is known for the velocity of his short passes. It seems the NFL record for such things is in the high 50's. I dont think its unfair to assume Brady's average throw is in the high 40's.

That means with every pass, a wet football is being spun with great velocity. And now that I think about it, I guess the rate at which the football spin might not have a linear (?) correlation with the velocity of the pass.

While I am told that evaporation effect can't lower the temperature of the football below air temperature (hard for me to get my head around this), it seems that you feel that it's important to know the temperature of this wet outside layer.

Either way, as the football is spun, that thin layer of water is going to evaporate. It just seems to me that might be important to take into consideration even if its a small detail.

Danger Zone said:

While I am told that evaporation effect can't lower the temperature of the football below air temperature

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I don't think that is correct. I believe the correct formulation is that evaporative cooling can't drop the temperature below the dew point. For Foxboro that evening the dew point looks to be in the very low 40's:

Graph at bottom of this page:

http://www.wunderground.com/history...reqdb.zip=02035&reqdb.magic=1&reqdb.wmo=99999

So I think the temperature after evaporation is somewhere between the air temp and the dew point - so perhaps mid-to-high 40's.

Note that the rain itself could be colder than this.

By the way, here is a very nice presentation (not sure if it has been posted here previously) showing the gauge/absolute mistake that many made initially:

https://www.khanacademy.org/science...ry/ideal-gas-laws/v/deflategate-ideal-gas-law

The Khan Academy by the way is a fantastic site for learning math (and some other things) from grade school level through college. Much better lectures than most teachers or college professors.

Dr Pain said:

Last I recall you had sent him the science and he was open to it.

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No,

He said he would look at the links I sent him which cast doubt on the across-the-board 2 psi drop claimed by Mort but he never got back

tom.kordis said:

Does that answer your question?

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If you're saying that you think you have good estimates for some effects, and bounds that aren't good estimates for others -- then yes.

Before we run formulae ad infinitum, remember that we do not KNOW the precise psi measurements before or after. Just "nth hand "reports". BB did say that we ASK the refs to set the balls at 12.5 but there is no record or even a comment by the refs as to what they actually set them at assuming they "set" anything when checking the Pats balls.

Then there's the issue of how accurate the pressure gauges are. They could be 4 figure precise for all I know or they could not even be 3 figure precise. I've read nothing on this. And how precise is a N figure gauge that has been used for time T? Nobody here knows.

Bottom line: the possible error bars and uncertainty of data overwhelm precise gas law calculations which should be simply trusted to indicate a range of psi drops yet trusted implicitly in their mandate that psi MUST drop with temperature.

PatsWickedPissah said:

Bottom line: the possible error bars and uncertainty of data overwhelm precise gas law calculations which should be simply trusted to indicate a range of psi drops yet trusted implicitly in their mandate that psi MUST drop with temperature.

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Excellent post.

And let me add even more uncertainty: how much air does gauging the ball release? How many times was a needle stuck into the football by an NFL employee, Kensil or for the intercepted ball, the Colts guys, before somebody wrote down the PSIs at half-time?

PatsWickedPissah said:

Then there's the issue of how accurate the pressure gauges are. They could be 4 figure precise for all I know or they could not even be 3 figure precise. I've read nothing on this. And how precise is a N figure gauge that has been used for time T? Nobody here knows.

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In the Peter King video where he shadowed refs pregame a few years back, it was clear that they used an analog gauge (dial-type) rather than digital, by my recollection. I don't have the link handy.

By appearances it was not even a gauge tailored for this use, as the analog scale went from zero to at least 50 or so psi. I would seriously doubt the precision in the tenths of psi digit.

What I am saying, if it is something like this, there is no way to clearly see if the needle is at (say) 12.3 rather than 12.4. It would just be a judgement call:



If it were analog but a tighter range, like this one, precision in the tenths digit would be possible but still not automatic (this one is calibrated for bar pressure rather than psi, but same idea).




Of course, this just speaks to precision. Accuracy could also be in question.

Kensil didn't even necessarily use the same type of gauge that the ref had used pregame.

tom.kordis said:

Jackson, I am not in the slightest "anti-education". I have spent over 30 years encouraging high school students to get as much & the best education possible.

The main thing that engineering students know how to do is "pass tests", because "passing tests" IS their job.
That AIN'T engineering.

Let's see your intellectual chops.
Please explain to me how the fact that a bunch of roughnecks, inspectors & accountants screwed the pooch on an oil platform proves that a bunch of wet-behind-the-ears engineering students are competent at running engineering tests.

If you are able to interpret what I wrote, you'll see that it says, in essence, that I want people who are well experienced in running tests involving the measurements of pressure & temperature ... to run some tests involving the measurements of pressure & temperature.

So, i'm not the slightest bit "anti-education".
I am very, very strongly "pro-experience".

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The true test of a scientist is whether they've liked "I ****ing love science" on Facebook.

SlowGettingUp said:

Do we know what the likely temperature of the rain was? Any meteorologists around that could answer that?

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Short answer: I don't know.

I've done some searching on the net for scientific articles that describe the formation of raindrops. Everything I've seen suggests that they form as tiny nucleation sites at very cold temperatures (less than 0°F), and then grow thru complex, not yet understood, processes.

From all this, i'd expect that they be significantly colder than the air (5°F to 10°F colder would be my guess). In my tests, I wanted to stay conservative, but still capture a bit of this effect, so I set my cold air to 50°F & the water bath to 48°F.

SlowGettingUp said:

Could there also have been some evaporative cooling given the wind? Or does the high humidity preclude that?

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Right. At 100% relative humidity, evaporation, & its cooling, goes to approximately zero.

But I believe that air in the midst of rain is at slightly less than 100% RH. A cloud or fog is at 100% RH, with water precipitating at all locations. It seems to make sense that the fact that you can see thru rainy air means that it is slightly less than 100% RH.

Maybe someone more knowledgeable on this could chime in.

So, for something the size of a football, evaporative cooling becomes negligible.

But not negligible for something the size of a raindrop falling at its terminal velocity, which is surprisingly slow at between 7 ft/sec for a drizzle & 30 ft/sec for large droplets (wiki).

Fencer said:

If you're saying that you think you have good estimates for some effects, and bounds that aren't good estimates for others -- then yes.

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Yes, that's both fair & correct.

And true for virtually all post facto experimental models, which tend to have imperfect knowledge of key factors.

And yet, we slog ahead ... doing our best ...

PatsWickedPissah said:

Before we run formulae ad infinitum, remember that we do not KNOW the precise psi measurements before or after. Just "nth hand "reports". BB did say that we ASK the refs to set the balls at 12.5 but there is no record or even a comment by the refs as to what they actually set them at assuming they "set" anything when checking the Pats balls.

Then there's the issue of how accurate the pressure gauges are. They could be 4 figure precise for all I know or they could not even be 3 figure precise. I've read nothing on this. And how precise is a N figure gauge that has been used for time T? Nobody here knows.

Bottom line: the possible error bars and uncertainty of data overwhelm precise gas law calculations which should be simply trusted to indicate a range of psi drops yet trusted implicitly in their mandate that psi MUST drop with temperature.

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I must respectfully disagree.

The key objective here is NOT convincing competent scientists & engineers. They already know or can figure it out.

The key objective is convincing amateurs: the NFL, lawyers, media hacks & the public.

The simple, correct statement that "pressure drops with temperature" is - IMO - useless. Even counterproductive.

It allows to stand (unchallenged, undisproven) the wrong statements, which have been made publicly by idiots, that "the pressure lapse rate is around 0.02 psi / °F" and its corollary "the temperature can only account for about a 0.5 psi drop". And its corollary "the Patriots must have cheated to account for the rest of the 1.5 psi drop." Or "in order for the balls to have been at that pressure, they must have been filled at 90°F."

A competent scientist/engineer/layperson who understands simple algebra realizes that all the statements above are false. But only after running the numbers.

It is only after you run the numbers that one realizes that the pressure drop reported is exactly what one would expect SOLELY due to the difference between the inflation temperature & the temperature of the balls after use at 50°F rainy conditions.

This is, I believe, the bottom line.
__

But the general public's eyes will glaze over at the sight of a little algebra.

The ONLY thing that will convince the unbiased public is objective experiments.

NOTHING will convince the biased public or media morons. They don't want to know the truth of the matter. Fortunately, these idiots are irrelevant. Except as targets for "pointing fingers & laughing".
__

I understand what you are saying about the unknowns in the initial conditions & in the measurements.

What I suggest is to stop focusing on the events of that game.

Instead, make the 800 lb gorilla be the experimental testing.

In this case, we CAN control/measure the start temps, start pressures and final temps, and then measure the final pressure. And, due to these experiments, we can assert with confidence, that the pressure lapse rate is around 0.06 psi/°F.

The Pressure Lapse Rate is The Key.

Amateurs thought that the PLR was 0.0 psi/°F.
Morons (aka, "people who publicly state wrong answers") claimed that it was 0.02 psi/°F.
Experts (and clever people who turn to experts for their information) know that it is (theoretically) 0.051 psi/°F.
Experts who have done the experiments know that it is closer to 0.06 psi/°F.

The above is unequivocal, unarguable, and depends not one iota on any NFL game ever played.

Once one knows this number accurately, then you can plug any plausible numbers for the initial temperatures, initial pressures & final temperature (including measurement errors) and determine immediately what the final pressure SHOULD HAVE BEEN.

Just as soon as a reasonable person sees that a ball inflated to 12.5 psi at 75°F SHOULD READ 11.0 psi at 50°F, the whole controversy evaporates.

Just My (Not So Humble) Opinion.

I have long ago stopped giving a fiddler's flying f### about any of this BS. Patriot haters and Patriot fans will not have their opinions changed one iota based upon this scientific, empirical investigation. It's a sham. I don't care what the finding of the Wells team is. This was nonsense from minute one and remains nonsense today. This league is a clown show run by the ultimate Clarabell the Clown.

Jackson 2 said:

Patriot haters and Patriot fans will not have their opinions changed one iota based upon this scientific, empirical investigation.

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The people for whom this statement is true are brain-dead idiots.

I do believe that the vast majority of people WILL change their opinion if they are shown the clear, convincing, numerical proof in a simple, competent experiment.

The only problem, right now, is getting a video of the experiment into the sporting news.

The sports media is not the slightest bit interested in bringing this stupid "controversy" to a stop. There have been a dozen people who, like me, have run that experiment. We've all gotten exactly the same result: The temp difference explains the entire pressure drop.

IF the league office brings out any ruling other than "the temperature change was responsible for the entire pressure drop", then the above simple experiment will magically become absolutely fascinating to the media. Because it'll give them someone else (the NFL office) to lynch.

They don't really care who they lynch.
As long as it's good & bloody.

tom.kordis said:

The people for whom this statement is true are brain-dead idiots.

I do believe that the vast majority of people WILL change their opinion if they are shown the clear, convincing, numerical proof in a simple, competent experiment.

The only problem, right now, is getting a video of the experiment into the sporting news.

The sports media is not the slightest bit interested in bringing this stupid "controversy" to a stop. There have been a dozen people who, like me, have run that experiment. We've all gotten exactly the same result: The temp difference explains the entire pressure drop.

IF the league office brings out any ruling other than "the temperature change was responsible for the entire pressure drop", then the above simple experiment will magically become absolutely fascinating to the media. Because it'll give them someone else (the NFL office) to lynch.

They don't really care who they lynch.
As long as it's good & bloody.

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I don't think people how often this kind of pressure change happens around them all the time.

For example, a couple of weeks ago, I was leaving an appointment and was carrying an empty 20 oz plastic water bottle in my hand. In the couple minutes it took to reach my car, the bottle looked like it had been partially crushed. The temperature was in the 20s outside and I was leaving a building where it was probably 70 degrees. I put the bottle in the cup holder and turn the heat on in the car. After driving for several minutes, I hear the plastic pop as the bottle returned to it's original shape.

No one secretly deflated the bottle while I was in the parking lot or reinflated it while I was driving. The temperature fluctuations affected the pressure inside the bottle. There's a big difference between a thin plastic bottle and an inflated air bladder with a leather covering, but the concept is the same.

Great visual example of the effects of temp on pressure. Kudos for recognizing the effect.

However, if you had run the experiment closer to the actual temp/pressure conditions, nothing would have been visible to the naked eye. Which is part of the problem.

"There's a big difference between a thin plastic bottle and an inflated air bladder with a leather covering, but the concept is the same."

You're not giving your model enough credit. They are not that different at all. Both the leather of the ball & the plastic of the bottle have a fairly high stiffness (i.e., high resistance to stretch due to changes in pressure). In math-speak, the ∆Volume/∆Pressure is fairly low for both the ball & the plastic bottle. But only if the pressure is always above 0 psig.!!

The real difference is that you started with atmospheric pressure (0 psig) in the bottle, whereas the football starts at +12.5 psig. A football, treated exactly the same as your bottle (p1 = 0 psig, t1 = 70°F, t2 = 20°F), would have behaved EXACTLY as your bottle did. Normal shape (but extremely "soft") at 70°F, flattened at 20°F, back to normal shape when warmed back up.

If, instead, you had pressurized the bottle to 12.5 psig @70°F (& assuming that it didn't pop), then brought it to 20°F for long enough to equilibrate, there would have been VERY LITTLE visible evidence of the change in pressure. The bottle would have looked pretty much the same. But the pressure inside would have been a little below 10 psig. It takes a pressure gauge to see the 2.5 psi drop in pressure.

Which it part of the problem. The low pressure cold balls LOOK just like the high pressure warm balls.

Which is exactly why the league & non-technical folks ASSUME (& assume wrongly) that the pressure of the cold balls should not change.

I wouldn't have thought of this unless you'd brought up your observation.
Thanks.