|MadSci Network: Science History|
We often assume that people who lived before the advent of the steam engine or electricity were pretty primitive. Not so; our ancestors were often pretty ingeneous, and so it was with refrigeration. Israel, where most of the Bible was written tends to be in a warm climate. However, according to http://www.avbtab.org/rc/wine/anrefrig.htm Mount Hermon is snow capped throughout the year. A number of sources indicate that ice was harvested in China in 1000 BC. Another reference, http://www.history-magazine.com/refrig.html indicates that Greeks, Romans, and Hebrews placed large amounts of snow into storage pits, covering the snow with insulating material so it was available as needed. So, the first way that the ancients could cool their drinks was by harvesting ice and snow either from the tops of mountains almost year round, or from colder climates. My grandmother had an ice box in her kitchen where the ice man would deposit blocks of ice which he carried around in a wagon. I thought her ice box was neat; her house is less than 100 years old so we are not really talking ancient technology. It had a door on the outside for access so the ice man didn't need to bother her. It is interesting to note that we measure cooling capacity relative to the amount of cooling produced by a certain amount of ice. At http://www.maritime.org/fleetsub/refrig/chap4.htm we find that one ton of refrigeration is the amount of cooling produced by melting one ton of ice over 24 hours. The second method of cooling things was by evaporative cooling. Boy Scouts would often have a cover saturated with water around their canteen. As the water evaporates, it cools the contents of the canteen perhaps by 20 to 40 degrees. Egyptians apparently would put earthen jars on their roofs to allow them to cool during the night. If the jars were not glazed, water could seep through the jar and evaporate, cooling the contents. Of course, evaporative cooling works best in a climate with low humidity, like in a desert. Another factor that can be used for cooling is radiation. A clear sky at night presents a heat sink with an absolute temperature of 2 degrees above absolute zero. When something is exposed to the night sky, it tends to cool down by radiation. As a result, puddles can freeze over, even though the air temperature has not dropped below the freezing temperature of water. Wells and caves are shielded from the cyclic heating of daylight. As a result, they have been used for cooling foods for a long time. A deep well can benefit from radiation cooling. Root cellars are one example of artificial caves that maintain a low enough temperature to help preserve foods. http://www.shef.ac.uk/assem/issue6/Kelly_web.htm is a web site that suggests that certain wells found in Greece were apparently used as refrigerators. Apparently Cleopatra enjoyed ice in her wine, and when the Bible refers to cool or cold cups of water, those in Israel had some knowledge of how to get one. Thanks for a very interesting question.
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