According to a common version, the German naturalist was going to fix an important mark on his scale at the level of normal human body temperature. However, his wife was running a fever at the time, making 100°F equivalent to 37.8°C today. We checked how plausible this legend is.
The Fahrenheit scale is one of the main temperature scales, which is used in a number of countries around the world, particularly in the USA. This is what the portal reports about the history of its appearance newtonov.ru, helping schoolchildren study physics: “In his Fahrenheit scale, he used not two, but three main reference points. The freezing temperature of a mixture of ice, water and ammonia was taken as zero, which, according to one version, corresponded to the temperature of the coldest day of the winter of 1709. The second point is the freezing point of water. She took the mark at 32°. And the third point, at 100°, was supposed to be the temperature of a healthy person. But either people were hotter 300 years ago, or Fahrenheit measured something wrong.
In general, 100 °F is not the temperature of a healthy person, but of the sick person himself. There is a version according to which Fahrenheit took the temperature of his wife as the standard for the temperature of a healthy person. But at that time she was ill, and what happened happened.”
Similar information can also be found on resources such as 1001fact.ru, skio.ru, mirokdetok, and in many other sources. But on the website of the Canadian state research university Lakehead approvedthat the researcher’s wife was healthy and, accordingly, the measurement showed 96° on his new scale. The portal says the same thing. sizes.com.
If you use online calculator to convert degrees Fahrenheit to the more familiar degrees Celsius, we get the following result:
100 °F = 37.777… °C
That is, indeed, if the version with body temperature as a motive is true, then the standard for Fahrenheit should have been a not entirely healthy person. But let's take a closer look at the history of his invention.
Daniel Gabriel Fahrenheit was born in 1686 in Danzig (present-day Gdansk) into a German family. From a young age he showed an interest in natural science experiments, and later, when he had settled in the Netherlands, he made a thermometer and a barometer. At first he used alcohol as a thermoscopic liquid, but around 1714 he replaced alcohol with mercury, which achieved much greater measurement accuracy. Finally, in 1724, he proposed a fundamentally new scale, which would become the standard in English-speaking countries for meteorological, industrial and medical purposes for the next two and a half centuries. To convert temperature on this scale to degrees Celsius and back, the following formulas are used:
Many people who encounter them for the first time complain about the inconvenience of such a transformation. However, few of these people know that the Celsius scale was proposed 18 years later, in 1742, meaning the questions in this case should not be addressed to Fahrenheit.
So what do we know today about the three calibration points of the Fahrenheit scale?
Thinking about a suitable marking for his future thermometer, Fahrenheit in 1708 visited the elderly Danish astronomer Ole Roemer (not to be confused with Reaumur), who developed his own scale. It should be noted that Römer's boiling point of water was 60 degrees, the temperature of a very cold winter in Denmark was taken as zero, water froze at 7.5 degrees, and normal body temperature was 22.5 degrees. Many years later, in a letter to another physicist, Fahrenheit will tell about this visit: “I found him [Roemer] early in the morning, he placed thermometers in water with ice. Later he placed them in water at body temperature. After he marked these two points on all the thermometers, he added half the distance between the points below the ice point and divided the resulting segment into 22.5 equal parts, starting from zero. 7.5 degrees at the ice point and 22.5 at body temperature. I used this graduation until 1717, with the only difference that I divided each degree into four more parts. <…> This graduation is very inconvenient because of the fractions, so I decided to change the scale and use 96 instead of 22.5 or 90, since then I have been using it.”
Thus, as we see, Fahrenheit took the development of Ole Roemer as the basis for his scale, but for convenience he multiplied some (but not all, as we will see later) numbers by 4. Moreover, already in the description of the Dane’s scale a certain “body temperature” is mentioned. However, this does not provide a precise answer to the question of calibration points. In his publications of 1724 Fahrenheit writes that his scale uses three: the lowest possible temperature of a mixture of ice, water and ammonia or even sea salt (0 °F), the melting temperature of ice (32 °F) and body temperature (96 °F). However, this is not a completely correct message. How note modern scientists, in the first case you can get +5 °F or even –8 °F (in the case of sea salt), that is, this is not even the same value, not to mention the discrepancy with zero. Perhaps you're right legend that the position of the column during the abnormally cold winter of 1708–1709 in Danzig (and not in Denmark) was taken as zero.
In addition, after Fahrenheit's death, his scale changed slightly. In 1776, a commission of the Royal Society of London headed by Henry Cavendish made a decision calibrate the scale so that water freezes at exactly 32 °F and boils, respectively, at 212 °F (a distance of 180 degrees is a round number, especially for degrees). So today's "normal body temperature" is not 96°F as in Fahrenheit (it would now be 35.56°C), but 97.88°F (armpit) and 98.6°F (mouth).
Yes, and finally, about the wife of Daniel Fahrenheit. Alas, carried away by his experiments, in his entire life he never didn't get married. The curious legend turned out to be a fiction.
Not true
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