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The Limits to Growth model was based on the assumption
of exponential growth. Exponential growth increases surprisingly
rapidly compared with linear growth.
Arithmetic or Linear versus Exponential
Growth
An example of arithmetic growth is 1,
2, 3, 4, 5, and so on. Exponential growth
means a quantity increases by doubling: 2,
4, 8,16, 32, and so on.
A
Riddle
"A French riddle for children
illustrates another aspect of exponential
growth&emdash;the apparent suddenness with
which it approaches a fixed limit. Suppose
you own a pond on which a water lily is
growing. The lily plant doubles in size
each day. If the lily were allowed to grow
unchecked, it would completely cover the
pond in 30 days, choking off the other
forms of life in the water. For a long
time the lily plant seems small, and so
you decide not to worry about cutting it
back until it covers half the pond. On
what day will that be? On the twenty-ninth
day, of course. You have one day to save
your pond."
Source: Donella H. Meadows et al., The
Limits to Growth, Pan Books
Ltd, London and Sydney, 1972, p. 29.
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