From PETER GRAHAM
James Levy asks if there are any theoretical limits to the growth of
the human population on Earth (Letters, 13 June). In 1964 JH Fremlin (‘How
many people can the world support?’, New Scientist, 29 October 1964) showed
that there is an absolute limit to human population growth. This is the
number at which the heat produced by metabolism equals the amount of heat
that can be radiated off a sphere the size of the Earth – any increase and
the temperature will rise, since the Earth can no longer be cooled. He calculated
that this number was approximately 6×1016 individuals, or about 120 people
per square metre.
Of course, in order to reach this limit a number of technical problems
will have to be solved. This should be no problem, since the number of clever
people will increase exponentially as the population rises, and they should
have no trouble in solving these difficulties.
At the present rate of population growth, we should reach this ‘heat
limit’ in about 1000 years.
Peter Graham Radstock, Avon
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