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J. Perelman
"Entertaining physics". Book 2.
Chapter 7. Thermal phenomena

WHAT KIND OF HEAT WE ARE ABLE TO ENDURE?

People are much tougher in relation to heat than usually thought: he is able to endure in the South the temperature is significantly higher than what we in the temperate zone believe barely tolerable. Summer in Central Australia is often observed temperature 46° in the shade; there was even mentioned temperature 55" in the shadow (Celsius). At the crossing of the Red sea to the Persian Gulf, the temperature in the ship's premises reaches 50° and above, despite continuous ventilation.

The highest temperature observed in nature on earth, did not exceed 57°. The temperature of this set in the so-called "Death Valley" in California. The heat in Central Asia - the hottest place our Union is not above 50°.

Marked now the temperature was measured in the shade. Explain by the way, why meteorologists are interested in the temperature it is in the shade and not in the sun. The fact that temperature measures only the thermometer, placed in the shade. A thermometer placed in the sun can heat up its rays is much higher than the surrounding air, and his testimony does not characterize the thermal state of the air environment. So it makes no sense, speaking of hot weather, to refer to the reading of the thermometer exposed to the sun.

Performed experiments to determine the highest temperature which can sustain the human body. Was that at a very gradual heating of the body in our dry air is capable of withstanding not only the temperature of boiling water (100°), but sometimes even higher, up to 160°C, as demonstrated English physics Blagden, Centre who for the sake of experience hours in the oven bakery. "You can cook eggs and fry the steak in the air, in which people remain without harm to themselves," remarks on this issue Tyndale.

What accounts for such endurance? The fact that our body does not actually accept this temperature and maintains the temperature close to normal. He struggles with heated through copious sweat; evaporation of sweat absorbs a significant amount of heat from the layer of air, which is directly adjacent to the skin, and that sufficiently lowers its temperature. The only prerequisites are that the body is not in contact directly with the source of heat and that the air was dry.

Those who have been in our Central Asia, he noticed, no doubt, as relatively easy to carry out there the heat at 37 degrees Celsius. 24-degree heat in Leningrad tolerated much worse. The reason, of course, in air humidity in Leningrad and dry it in Central Asia, where the rain is extremely rare*.

* Interestingly, there my pocket hygrometer twice in the month of June showed zero humidity (13 and 16 June 1930).

Entertaining physics J. Perelman

 




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