What If? 2: Additional Serious Scientific Answers to Absurd Hypothetical Questions (What If?, #2)

by Randall Munroe

It might seem strange that a metal that’s cool to the touch in small amounts would be so hot when collected together in a big ball, but this is just a consequence of scale. Since volume grows faster than surface area, larger objects produce more heat per unit of surface area, so they have to get hotter to radiate it away. Really big objects can get extremely hot from even a tiny amount of heat production per unit of volume. Even the core of the Sun, where nuclear fusion happens, would be pretty cold if you could somehow isolate a piece of it. A cup of solar core material2 produces about 60 milliwatts of thermal energy. By volume, that’s about the same heat production rate as the body of a lizard, and less than that of a human. In a sense, you’re hotter than the Sun—there’s just not as much of you.