> >>     The Romans used to make ice in the Sahara Desert area by
> >>     using entirely natural cooling resources.
> >
> >It does get pretty cold at night out there.
>
> It's not the cold that does it, the earth barely goes below zero. It's the
> clear dark sky at the the radiation temperature of space (4K)


That's the trick.
The thermal input of the atmosphere has an opposing affect of course (or
we'd all die). Arguably this would work in daytime as well with a larger
than star-viewing black internal painted and now well insulated pipe.



        RM

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