Why is the Fire Hot?

One winter evening, when the innovative engineer R. Buckminster Fuller was drinking tea by the fireplace of Professor Hugh Kenner, three-year-old Lisa Kenner prolonged her bedtime farewell with the question: "Bucky, why is the fire hot?" Kenner writes: Some instinct told Lisa that he was the man to ask. His answer, as he took her on his lap, began, like most of his answers, some distance away from the question. "You remember, darling, when the tree was growing in the sunlight?" On arms like upgroping branches, his hands became clusters of leaves as he described their collecting the sunlight, processing its energies into sugars, drawing them down into a stocky trunk. "Then the men cut it down, and sawed it into logs. And what you see now" ---he pointed to the crackling hearth---"is the sunlight, unwinding from the log."