Could You Please Turn Down The Thermodynamics?

(A woman enters the shop and proceeds to browse whilst talking nonstop, and at great length, about whatever enters her head for about forty minutes.)

Woman: “Gosh, it’s so hot in here!”

Me: “Well, I’m sorry about that. We don’t actually have the heating on, or I would turn it down.”

Woman: “It’s all these lights! Look at all these light bulbs. It’s ridiculous! Why don’t they just make light bulbs that don’t give off any heat?”

Me: “Physics?”