Nocturnal ice making in early India and Iran In India before the invention of artificial refrigeration technology, ice making by nocturnal cooling was common. The apparatus consisted of a shallow ceramic tray with a thin layer of water, placed outdoors with a clear exposure to the night sky. The bottom and sides were insulated with a thick layer of hay. On a clear night the water would lose heat by radiation upwards. Provided the air was calm and not too far above freezing, heat gain from the surrounding air by <https://en.wikipedia.org/wiki/Convection> convection was low enough to allow the water to freeze. <https://en.wikipedia.org/wiki/Radiative_cooling#cite_note-icemaking_radiati ve-5> [5] A similar technique was used in Iran as well. <https://en.wikipedia.org/wiki/Radiative_cooling#cite_note-6> [6]
I confused the issue by insisting that the dish be a parabola. Nick Nicholas Thompson Emeritus Professor of Ethology and Psychology Clark University [email protected] <mailto:[email protected]> https://wordpress.clarku.edu/nthompson/
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