From earthenware jug to fridge

As far back as Antiquity, people in hot countries have used the cooling properties of low-pressure areas to lower water temperature. An example are the slightly porous earthenware jugs which, when placed in a warm breeze, cool their contents.

The principle is simple: evaporating the film of water around the jug creates a slight low-pressure area large enough to cool the water. We have all felt a bicycle pump heat up when we use it or an aerosol can cool down when we empty it. Refrigerators work in much the same way, using a compressor to condense an expanded gas circulating in their tanks.

Using heat for cooling: how's that for a paradox showing just how stubbornly determined mankind is to master nature!