This system was, however, tremendously expensive, both in terms of natural and human resources, and raised the possibility of an accidental nuclear war.
Man-made threats such as nuclear war or nanotechnology are harder to predict than natural threats, due to the inherent methodological difficulties in the social sciences.
How come the nostalgia merchants haven't brought it back along with all the rest of the stuff from the 1980s, like leg-warmers and the threat of nuclear war.
