Does having a spoon in the cup keep your coffee hot for longer? I was recently told that having a metal spoon in the coffee would heat the cup of coffee up, and that it would be hotter if I stirred because of the conductivity of the metal in the spoon. This seems counter intuitive because wouldn't the spoon radiate the heat out from the handle? He provided an answer I didn't quite understand (he's an engineer), but I have to check here. Is this true?

The spoon's conductivity would only heat the coffee if you were holding the spoon with a super-hot hand. Assuming the spoon (and your hand) are both cooler than the coffee, they will both conduct heat away from the liquid, causing the coffee to cool a teensy bit more quickly.

Stirring the liquid should logically only speed the process.

Believe it or not, a fellow nerd on physics.stackexchange.com conducted an experiment on this very issue and published the results, which confirm my hypothesis:

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