Recent "the sky is falling" news stories have dealt with the
fall from orbit of the Mir Space Station rather than NEO
impacts. The press and public are clearly interested in the risk
of falling objects, but sometimes risks are perceived in ways
that are quite different from the hazard as calculated
numerically. The following is a very rough estimate of risks, in
"order of magnitude" terms only. It is intended to be
illustrative, but certainly not precise. By risk I mean the
chance or probability that any individual will be killed as a
result of either a spacecraft atmospheric entry or the impact of
a NEO. Let's start with the risk of death as a result of being
struck by a piece of Mir on the assumption that the fragments
could land anywhere on Earth. Suppose 1000 large metal fragments
survive to hit the ground, and that if you are within 1 meter of
the impact point you will be killed. Thus 1000 square meters are
at risk, out of a total surface area of the Earth of about 100
trillion (10**14) square meters (no