I think the volume of the air bladder could change quite a bit. Isn't it just made of rubber?yeah that's a constant volume process. i don't see how the volume would change much (excessive Gronk spiking!). anyway, scenario 2 (!) which i think is clearly what happened:
Belichick inflated them in a sauna, NFL tested in a meat locker:
P1: 12.5 psi
T1: 100 F
T2: 0 F
P2: 10.3 psi
there is is. there's that 2 psi. Belichick needs to use this to clear his good name.
Edit:
But I agree, it just don't look right.
not sure where inflation of a football falls (constant volume, isentropic, etc.) but for the sake of jockying around on a forum i figured constant volume was good enough. my thought was you could inflate that thing to 30 psi, and yeah you'd see some increase in volume, but a relatively negligible amount. especially when you consider we're really only talking about a range of +/- 2 psi.
*nerdy high-five*