Chicken6,
I was intending to refer to the window ope situation, hence my original question about openeing the windo. As soon as you do, it ceases to be a closed system. Quite evidently if you strapped a rocket to the a/c and shot it into space (with the window closed and the a/c pressurised) the whole would act as one. If the windows is open, I feel that the situation changes (apart from a. the geese suffocating b. their blood boils and c. they have nothing to fly in). Seriously, even in the atmosphere I think the situation is different.
I agree with the physicist, it's a bit sad to be dealing with this topic.
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Another day in paradise