From: henry@spsystems.net (Henry Spencer)
Newsgroups: sci.astro,sci.space.science
Subject: Re: Cosmic ray-bans and the Local Interstellar Medium
Date: Wed, 8 Jul 1998 15:31:32 GMT

In article <6nmv6p$7mj$1@nnrp1.dejanews.com>,
 <myke_reynolds@my-dejanews.com> wrote:
>What is the minimum protection needed to stop cosmic rays and
>gamma rays resulting from cosmic ray impacts? An inch of lead?
>Ten feet of concrete?

Depends on what you mean by "stop".  Neutrino detectors, some of them a
kilometer down in solid rock, still have to put a substantial effort into
distinguishing neutrino arrivals from noise produced by cosmic-ray hits.

It's worth remembering that the mass of Earth's atmosphere is about
10t/m^2, so anything that's going to add significantly more shielding
is going to have to be measured in tons per square meter.

>By how much is it estimated that cosmic rays would increase
>if the heliosphere were stripped away down to the orbit of
>the earth? What is the estimated cosmic ray exposure in
>interstellar space, outside the heliosphere, as compared
>to levels on the earth now?

Last I heard, there were only vague ideas about this.  It's never been
measured.
--
Being the last man on the Moon is a |  Henry Spencer   henry@spsystems.net
very dubious honor. -- Gene Cernan  |      (aka henry@zoo.toronto.edu)