[ExI] SETI for Post Singularity Civ

John Clark johnkclark at gmail.com
Sun Jan 18 16:55:14 UTC 2015

On Sun, Jan 18, 2015 at 5:50 AM, Anders Sandberg <anders at aleph.se> wrote:

> Consider a spherical M brain of radius R and heat production P per
> volume. If it just cools by blackbody radiation [...]

But why make that assumption? I think a large brain would have a active
cooling system, and Helium-2 might be a good fluid to use to get the job
done. Helium liquefies at 4.2 K but when it gets below 2.17 K it turns into
a superfluid, Helium-2, that has zero viscosity, provided that the pipe the
helium is flowing through does not have a diameter smaller than 10^-9
meters. Liquid Helium superfluid is also by far the best conductor of heat
known, it conducts heat so fast (many times faster than the speed of sound)
that there are no hot spots in it and thus no bubbles, all of the Helium
superfluid is at the same temperature and so vaporization only takes place
at the surface.

 John K Clark
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