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calories in the mole planet to support the Earth’s current population for 30 billion years). Normally, when organic matter decomposes, it releases much of that energy as heat. But throughout the majority of the planet’s interior, the pressure would be over 100 megapascals, which is high enough to kill all bacteria and sterilize the mole remains — leaving no microorganismsto break down the mole tissue.
    Closer to the surface, where the pressure would be lower, there would be another obstacle to decomposition — the interior of a mole planet would be low in oxygen. Without oxygen, the usual decomposition couldn’t happen, and the only bacteria that would be able to break down the moles would be those that don’t require oxygen. While inefficient, this anaerobic decompositioncan unlock quite a bit of heat. If continued unchecked, it would heat the planet to a boil.
    But the decomposition would be self-limiting. Few bacteria can survive at temperatures above about 60°C, so as the temperature went up, the bacteria would die off, and the decomposition would slow. Th roughout the planet, the mole bodies would gradually break down into kerogen, a mush of organic matterthat would — if the planet were hotter — eventually form oil.
    Th e outer surface of the planet would radiate heat into space and freeze. Because the moles form a literal fur coat, when frozen they would insulate the interior of the planet and slow the loss of heat to space. However, the flow of heat in the liquid interior would be dominated by convection. Plumes of hot meat and bubbles of trappedgases like methane — along with the air from the lungs of the deceased moles — would periodically rise through the mole crust and erupt volcanically from the surface, a geyser of death blasting mole bodies free of the planet.
    Eventually, after centuries or millennia of turmoil, the planet would calm and cool enough that it would begin to freeze all the way through. Th e deep interior would be undersuch high pressure that as it cooled, the water would crystallize out into exotic forms of ice such as ice III and ice V, and eventually ice II and ice IX. 4
    All told, this is a pretty bleak picture. Fortunately, there’s a better approach.
    I don’t have any reliable numbers for global mole population (or small mammal biomass in general), but we’ll take a shot in the dark and estimate thatthere are at least a few dozen mice, rats, voles, and other small mammals for every human.
    Th ere might be a billion habitable planets in our galaxy. If we colonized them, we’d certainly bring mice and rats with us. If just one in a hundred were populated with small mammals in numbers similar to Earth’s, after a few million years — not long, in evolutionary time — the total number that have everlived would surpass Avogadro’s number.
    If you want a mole of moles, build a spaceship.

    1 “One mole” is close to the number of atoms in a gram of hydrogen. It’s also, by chance, a decent ballpark guess for the number of grains of sand on Earth.
    2 http://en.wikipedia.org/wiki/File:Condylura.jpg
    3 Th at’s a neat coincidence I’ve never noticed before — a cubic mile happens to be almost exactly4/3π cubic kilometers, so a sphere with a radius of X kilometers has the same volume as a cube that’s X miles on each side.
    4 No relation.

Hair Dryer
    Q. What would happen if a hair dryer with continuous power were turned on and put in an airtight 1 × 1 × 1-meter box?
—Dry Paratroopa
    A. A typical hair dryer draws 1875 watts of power.
    All 1875 watts have to go somewhere. No matter what happens inside the box, if it’s using 1875 watts of power, eventually there will be 1875 watts of heat flowing out.
    Th is is trueof any device that uses power, which is a handy thing to know. For example, people worry about leaving disconnected chargers plugged into the wall for fear that they’re draining power. Are they right? Heat flow analysis provides a simple rule of