X-Message-Number: 3595
Date: Wed, 4 Jan 1995 22:20:27 -0500
From: "Keith F. Lynch" <>
Subject: Re: SCI.CRYONICS: Low Temperature Cryonics

> Molecules in an ice crystal may have vibrational rather than
> translational motion, but there is no reason for this to be true
> of a vitrified solid.

But it is true.

> Try looking at a window pane that is decades old -- the slow flow
> has visible effects.

No.  The reason why old windows tend to be thicker on the bottom than
the top is because the pane of glass was inadvertantly made that way,
due to poor quality control procedures in those days, and it was then
installed thick-side-down for stability.

> The very most conservative approach is the lowest possible
> temperature.

I don't agree.  The chemistry, evaporation, and translational motion
going on at liquid nitrogen temperatures is utterly negligible.  The
only thing lower temperatures gain you are additional cracking and
additional expense.  Cracking releases lots of heat over a small area,
possibly enough to scramble the clues that would otherwise allow
reconstruction of the "jigsaw puzzle".

Ignoring political and economic issues, and natural disasters, the
limiting factor in suspension time is radiation damage, which lower
temperatures won't prevent.  This limit is somewhere between a thousand
and a million years, depending on how repairable radiation damage turns
out to be, how radioactive the patient is, and how much radiation there
is from the surroundings.  (Patients can be made considerably less
radioactive by feeding them non-radioactive potassium for several weeks
before death, if anyone thinks it's worth it, and if the death isn't
without advance notice.)

> Only 3 elements have boiling points below that of liquid nitrogen
> (which boils at 77 degrees Kelvin) -- namely Neon (27 Kelvin),
> Hydrogen (20 Kelvin) and Helium (4.2 Kelvin).

True.  I checked for compounds with lower boiling points, and found to
my surprise that there aren't any (though carbon monoxide comes close).
It would also be possible to use the melting of a solid instead of the
boiling of a liquid, in the unlikely event that lower temperatures are
desired.  Another approach is to lower the pressure to get nitrogen to
boil at a lower temperature.

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