can even measure the rate at which free energy (perhaps from a Vegemite sandwich) flows as it is transformed into talking energy, running energy, and, eventually, heat energy, with entropy increasing at each step. The average human takes in about 2,500 calories each day, about 10.5 million joules (a measure of work or energy; a calorie represents about 4,184 joules). Divide this by the 86,400 seconds in a day, and an individual mobilizes about 120 joules every second. This is the “power rating” of a human being: 120 watts, just slightly greater than the power rating of many traditional
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