Curious cook Harold McGree is spending the day answering interesting kitchen questions on the New York Times's Diner's Journal blog. So far, he's deemed carrot tops safe to eat but reserved judgment on cheese with the mold trimmed off. On a more pleasant note, he explains why salt and pepper are our "basic" spices. And in the realm of kitchen thermodynamics, McGee analyzes the effects of heat on oil in pans and rimmed baking sheets.