From: "Paul F. Dietz" <email@example.com>
Subject: Re: von Braun (was Re: It's that time of year again...)
Date: Mon, 25 Dec 2000 01:09:56 -0600
"Michael R. Irwin" wrote:
> That partially solves part of the problem as you noted. Chemical and
> biological agents and 5 minute accuracy on a globe sized search area
> to go.
Global scale pinpointing in five minutes -- or even country
scale pinpointing in five minutes -- is not believable.
On a global scale, the detectors would have to be in
satellites. But the atmosphere is (vertically) about
30 absorption lengths thick for gamma photons (attenuating
unscattered photons by a factor of e^30, or about 10^13;
a 1 watt gamma source puts out roughly 10^13
photons/second.) So essentially nothing emitted at
the surface will make it to space.
Oh, and 30 absorption lengths of concrete would be
about 3 meters. For lead, about 2 feet.