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


In the book "Journey abroad" American humorist mark TWAIN tells of a case of his Alpine travel - case, of course, fictional:

"Our troubles were over; so people could relax, and I finally was able to pay attention to the scientific side of the expedition. First of all, I wanted to determine by means of the barometer the height where we were, but, unfortunately, did not get any results. From my readings I knew not the thermometer, not the barometer should be boiled to obtain evidence. Which of the two, I didn't know and probably that is why I decided to boil both.

And still got no results. After seeing both tools, I saw that they were completely spoiled: the barometer was only one copper arrow, and the bulb of the thermometer dangling a ball of mercury...

I found another barometer; it was brand new and very good. Half an hour I boiled it in a pot of bean soup that was cooked with the chef. The result was unexpected: the tool has completely ceased to operate, but the soup has acquired such a strong taste barometer that the chef is a very smart person, changed its name in the list of foods. New dish has earned universal praise, so I ordered to cook every day soup barometer. Of course, the barometer was completely spoiled, but I don't particularly regret it. It's not helped me to determine the height of the terrain, so it is more I don't need".

"Research scientists" by Mark TWAIN.

Dropping the jokes, will try to answer the question: what really ought "to boil", a thermometer or barometer?

The thermometer; and here's why. From previous experience we have seen that the smaller the pressure of the water, the lower the temperature of its boiling point. As show in the mountains atmospheric pressure decreases, you must decrease and the temperature of boiling water. And indeed, there are the following boiling point of pure water at different pressures of the atmosphere:

boiling point,°C
pressure, mm
101 787,7
100 760
98 707
96 657,5
94 611
92 567
90 525,5
88 487
86 450

In Bern (Switzerland), where the average pressure of the atmosphere 713 mm, water in open vessels full swing already at a 97.5°, and on top of Mont Blanc, where the barometer shows 424 mm, boiling water has a temperature of only of 84.5°. With a show for every kilometer of the water boiling temperature drops to 3°C. Therefore, if we measure the temperature at which boiling water (in the words of mark TWAIN, "if we boil the thermometer"), then, once the appropriate table will be able to know the height of the space. This requires, of course; to have a predetermined table, what mark TWAIN "just" forgot.

Used for this purpose instruments - hipsterville is not less convenient to carry than a metal barometers, and give a much more accurate reading.

Of course, and can serve as a barometer to determine the height of the space, because it directly, without any "boiling", shows the pressure of the atmosphere: the higher we go, the pressure is less. But here is necessary or table showing how the reduced air pressure as the elevation above sea level, or knowledge of appropriate formulas. It all seemed to be mixed up in the head humorist and prompted him to cook soup barometer".

Entertaining physics J. Perelman


System Orphus


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