Thursday, December 10, 2009

Is it cold out?

Since it is beginning to be a more serious version of pre-winter, this  seems to be a good time to consider the subject of heat.  When the temperature drops to zero or below, we like to have a furnace that works.  We have a body temperature around 98.6 but we tend to lose that heat steadily and are only comfortable with a little assistance from clothing, blankets and some sort of fire or heating system.

Many people tend to keep their houses cooler in the winter than we do.  We keep the thermostat set at about 68 or 69°.  Even then, I am often wearing a sweater or fleece jacket over other clothes.  At times when I am chilled in the winter, I have been heartened by Robert Heinlein's statement in one of his novels that with all the heat we make with our wonderful bodies, all we have to do to be warm is to slow the loss of heat.  Just what a hat, mittens and a woolen scarf do.  Yet, when we cross-country ski or jog outside, we often produce enough heat that the body kicks into sweat to cool.

I think it is surprising that humans have managed to survive the 4 million years or so with such a narrow temperature range to work with.  If our core temperature drops below about 90°, we die.  If our core temperature rises to 110°, we die.  So, a 15 degree range is all we have to work with.  Absolute zero is -459 and the highest temperatures are way up there.  A web page at Cal Tech says the center of the sun is 27 million degrees.  Clearly, we operate on the cooler end of possible but we do need heat assistance.

I read in a book on biking that the optimum temperature for fairly active work is 55°.  Above that, we tend to spend some of our energy on keeping cool and not overheating.  I have heard that lumberjacks worked outside in temperatures of 20 below in shirt sleeves because they worked so hard.  The program said that such lumbermen tended to eat 12,000 calories a day because of their energy expenditure.

We used to have a 5th grade social studies unit on the question of why the countries of the temperate zones of the earth have advanced the most in technical and industrial development.  In Florida, Maryland or Hawaii, we have found temperatures around 90° difficult for maintaining high energy levels.  Just as I am accustomed to temperatures below zero, I realize that many places in our country and elsewhere on this planet have temperatures of 110° or higher.  Even in cool northern states, we install air conditioning in our houses if we can afford to. 

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