westneat said:So I've played around with the physics a little bit. Turns out, I think NDT and Bill Nye are correct in their calculations.
Here is where I think some posters in this thread have messed up:
Say the ref's room is 75 degrees or 297K. And the halftime temp is 45 degrees or 280K. That gives us a ratio of 280/297 or .94. So the absolute temperature dropped by about 6%. This much everyone agrees with.
The balls have a gauge pressure of 12.5 PSI, and atmospheric pressure is (on average) 14.7 PSI. That gives the balls an absolute PSI of about 27.2. Take out the 6% due to the temperature drop, and we have a new absolute ball pressure of 25.6, or a difference of 1.6 PSI. This is the figure that people on SOSH have been quoting as correct. But it's not, because we still have to convert the ball's absolute pressure back to gauge pressure.
We can't simply subtract 14.7, because the atmospheric pressure has ALSO dropped due to the temperature change. The new atmospheric pressure will be 13.8. Subtract that from 25.6 and you get the ball's new guage pressure of 11.8. So we can only explain a change of .7 PSI due to temperature alone, which is exactly the numbers Bill and NDT quoted.
Except that the atmospheric temperature in the gauge room would still be 75 degrees.
The pigskin would still be cold (thermal mass) and is also an insulator of unknown quality.