To measure how many calories are in, say, a doughnut, here’s what to do: dehydrate the doughnut and place it in a cubicle submerged in a water bath. Then set the doughnut on fire (yes, really) and measure by how many degrees the water around it warms up. Multiply the temperature change by the amount of water in the container, the energy capacity of water (which is 1 calorie
