The Heat Limit

Are the earth's cities getting too crowded, spreading their swarming fringes over the suburban countryside? Are highways too jammed, streams too polluted? Is the world's population explosion threatening to smother India and China under a near-solid mass of humanity? Pessimists who are wrought up about such present-day conditions, says British Physicist John H. Frem-1m, have seen nothing yet. Fremlin has sturdy faith that man's ingenuity will be equal to his ever-growing need for food. But this is just the trouble. Eventually, he says, the earth will be so packed with human bodies that the heat they give off will put a final limit on their increase.

The earth's present population, says Fremlin in the New Scientist, is about 3 billion, and is now doubling every 37 years. For the next 260 years, this increase can be taken care of by exterminating land wildlife, by intensive use of all crop space, by elimination of meat eating, and by the efficient harvesting of sea food. If marine wildlife is replaced by photosynthetic plankton, the earth's population can keep feeding itself while doubling three more times, until it reaches about 3,000 billion in A.D. 2334. Five times as many people can be taken care of by putting up vast satellite mirrors to reflect sunlight onto the polar areas, warming the whole earth to equatorial productiveness.

For still more population increases, says Dr. Fremlin, food can be synthesized out of energy, mineral matter and waste products. Human cadavers can be homogenized for use as food, and the earth's population can rise to one million billion, with two people living on each square meter of ground.

But then a serious problem will develop. The earth will be so thickly covered with layers of people and machinery that it will generate enormous heat. Some 60 million billion people, living 120 to the square meter in air-conditioned 2,000-story buildings, will keep the earth's skin glowing orange-red.

This ultimate limit will be reached in less than 1,000 years, says Dr. Fremlin, whose tongue is only halfway in his cheek. He sees no obstacle to man's attainment of a dreadful level of existence where even his movements will be rationed because motion generates heat. "We are free to choose," he says, "at what population density we want to call a halt, somewhere between the .000,006 people per square meter of the present and the 120 per square meter of the heat limit. If we do not choose, we shall eventually reach that limit."

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