[ExI] Essential Upload Data (was: Subject: Boltzmann brains)

[John Clark]

On Fri, May 15, 2020 at 12:04 PM spike jones via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> >> At atmospheric pressure the boiling point of liquid argon is -186C,
>> and I think it would be a very bad idea to have large containers full of
>> brains pressurized at 30 atm. And liquid nitrogen cost about 30 cents a
>> liter but liquid argon costs $2.25 a liter.
>
>
>
> > *Regarding cost of argon vs nitrogen, that wouldn’t matter if the cycle
> is closed-loop: it doesn’t actually use up the material.  When we were
> fooling with it in the 80s, we had an open-loop system, but a full recovery
> re-condensation dual cycle is possible, as well as a hybrid system which
> uses liquid air as the heat sink for the argon condenser.*
>

That's way too many ways for things to go wrong, among other problems you'd
have to have a mechanical compressor, and you'd be at the mercy of the
electrical power grid. With liquid nitrogen refrigeration you have no
moving parts and brains would remain at -196C for several weeks even if you
did nothing and even with the power off, and after that maintenance would
not be complicated, all you'd have to do for maintenance is pour in some
more LN2 to top off the tank. The simpler the better if you want something
to keep working for a long time.

*> I can see big advantages to that.  The big disadvantage I can see is the
> risk of catastrophic loss of pressure, which would cause the temperature of
> the stored bio-material to drop quickly to -186C.  That would be a bad
> thing.*


It would be bad for the brains and bad for anybody standing nearby when the
pressure leak happened.

*> I may not have understood the reason why -135C came up to start with,*
>

The idea is above that temperature you get less cracking in frozen
biological tissue, however I don't see that as a major problem, but a
pressure leak or a malfunctioning compressor would be.

John K Clark
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