I agree with J . W. Chamberlain (October 1978 EOS, pp. 900–903) that evidence that no other civilization has followed our present course and survived should have important policy implications. Where we disagree is in the need for an expensive 100-year program to learn this. The evidence to this effect is now available. Furthermore, even the evidence Chamberlain proposes to collect is unlikely to have an impact on policy decisions.
An extrapolation of current rapid growth trends in population, GNP and technology for a couple of thousand years would indicate the necessity of constructing space stations (probably populated) to capture a significant percentage of the sun's total energy output. Such a situation would create an easily discernible infrared source. Since we can see no such sources, no civilization must have followed our course much past our present position, indicating our present path is not viable.