> >     The Romans used to make ice in the Sahara Desert area by
> >     using entirely natural cooling resources.

> dunno but i'd guess knowing you.

why thankyou :-)

> yes
> no idea how (though verry hot places also generally get verry cold)
> hmmm
> google time
> well thereya go
> minimum temperature is below freezing
>
> partial credit with use of google? ;->

Indeed.

Make pit in ground.
Make pit waterproof.
Partially fill with suitable quantity of water.
Expose to sky at nights.
Cover with best available insulating layer in daytime.
In time you get ice.

I've idly wondered about placing a parabolic mirror in an insulated longish
tube (see blue sky and stars story :-) ) and seeing if you got noticeable
focused coolth from deep space. The intervening atmosphere seems to mess
this up rather badly. Unlike high temperature photons from eg the sun coming
in, the outward physics works against you. A basic experiment with a
polystyrene insulated tube was inconclusive.

You can certainly cool something by radiation cooling if you "point" it  at
a cold area. Try sitting across a warm  room from an uncurtained window on a
cold day. Quite apart from convection.


        Russell McMahon

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