Re: Not always joking, it seems

Daniel R. Reitman <dreitman@[EMAIL PROTECTED]
> wrote:
> "Keith F. Lynch" <kfl@[EMAIL PROTECTED]
> wrote:
>> Cite?  Neutrons are extremely penetrating.

> ITYM neutrinos.

No, I mean neutrons.  Neutrinos are far more penetrating.  Neutrons
can go through a few feet of concrete.  Neutrinos can go through a few
thousand light years of concrete.

Even after a few feet, neutrons don't reflect back the way they came.
In most materials, they're absorbed.  In some, they're slowed to
thermal velocities and scattered in random directions.

For something to be a mirror, it must be opaque, and it must be smooth
on the scale of whatever it's reflecting.  To microwaves, a brick wall
is smooth.  To visible light, a sheet of silvered glass is.  (Atoms of
the mirror are much smaller than a wavelength of light.)  To neutrons,
nothing is smooth, as solid matter consists of empty space with
occasional small lumps.

The only thing you can do that's anything remotely like what Willie
Mookie is suggesting is that if you put a thick layer of graphite
*above* your reactor, and cool it to close to absolute zero, neutrons
scattered by it will have such low velocities that they will all
end up falling straight down, back into the reactor.  Of course the
neutrons will heat the graphite, so you need to keep pumping heat out
of it.  And at such low temperatures, that requires plenty of energy.
Possibly more than the reactor can provide.
-- 
Keith F. Lynch - http://keithlynch.net/
Please see http://keithlynch.net/email.html
before emailing me.