Cosmic Radiation

--- In spacesettlers@yahoogroups.com, "Arthur P. Smith"
wrote:
> victoriatangoman wrote:
>
> >Is the mass of the Earth even necessary or does the atmosphere do
> >the bulk of the job? How do we resolve the two conflicting
shielding
> >requirements from this debate?
> >
> Actually, the mass of the Earth makes things worse, due to radon
and
> other radioactive decay products from materials in the ground. For
the
> average person at sea level on Earth, exposure is 300
millirem/year,
> which comes from:
>
> (1) Radon in indoor air - 200 millirem/year (Radon is a gas that
comes
> from the decay of uranium and other heavy radiocative elements in
> Earth's crust)
> (2) Radioactive materials in our own bodies - primarily potassium-
40,
> also carbon-14: 40 millirem/year
> (3) Natural radiation from rocks and soil (direct radiation from
the U,
> Th, K-40 etc. in the ground) - 28 millirem/year
> (4) Cosmic rays - radiation from space - 26 millirem/year.
>
> Radiation exposure from cosmic rays doubles with every 6000 ft of
air
> (the "half-length" in air), so in Denver you get about 50
mrem/year from
> cosmic rays, and in a jet at 37,000 ft you get about 1500
mrem/year (but
> you don't stay up there all year).
>
> See - http://hps.org/publicinformation/radfactsheets/radfact25.html
>
> (1) and (3) together add up to over 8 times the exposure from
space
> radiation at sea level; if you could eliminate radon and ground
> radiation you'd be better off living at 18,000 ft than at sea
level, as
> far as radiation exposure is concerned.

This was extremely helpful to me. Thanks.

> By the way, the mass of air above us is pretty easy to calculate
from
> pressure - 15 lb/sq in, or 10^5 Newtons/sq m in metric - divide by
g
> (about 10) and you have 10,000 kg/sq meter of air above you.

Thanks again for the clarification. I thought of going this route
but was momentarily confused by the concept of 14.7 lb/sq.in as an
indicator of air pressure and didn't know how it related to air
density. Not wanting to delve into that when I was calculating the
numbers last night, I just worked it from another angle.

This would have been so much simpler.

Ignorance sucks. LOL. :-)

TangoMan