I think the confusion is about unverified assumptions. The author assumed that the problem is about an open or a leaky space (perhaps thinking about the sound traveling across the quad in the summer vs winter), while the teacher meant some closed container (e.g., a pressure cooker). The teacher wins. 

One more... Integrate Spaced Repetition device (Ankiweb, Readwise, ...) into your reading/learning flow to mitigate the memory decay, esp as you expose yourself to more and more things.

And thank you for the number 9 - "do stuff in public"... In fact, this is what inspired this public comment. Haven't done this in eons.