that control the nuclear arms themselves.

Much of our knowledge was thus gained by chance--a fact which should imbue
us with humility as we contemplate the remaining uncertainties (as well as
the certainties) about nuclear warfare. What we have learned enables us,
nonetheless, to see more clearly. We know, for instance, that some of the
earlier speculations about the after-effects of a global nuclear war were
as far-fetched as they were horrifying--such as the idea that the
worldwide accumulation of radioactive fallout would eliminate all life on
the planet, or that it might produce a train of monstrous genetic mutations
in all living things, making future life unrecognizable. And this
accumulation of knowledge which enables us to rule out the more fanciful
possibilities also allows us to reexamine, with some scientific rigor,
other phenomena which could seriously affect the global environment and the
populations of participant and nonparticipant countries alike.

This paper is an attempt to set in perspective some of the longer term
effects of nuclear war on the global environment, with emphasis on areas
and peoples distant from the actual targets of the weapons.



THE MECHANICS OF NUCLEAR EXPLOSIONS


In nuclear explosions, about 90 percent of the energy is released in less
than one millionth of a second. Most of this is in the form of the heat
and shock waves which produce the damage. It is this immediate and direct
explosive power which could devastate the urban centers in a major nuclear
war.