I know three scales: the Celsius scale, the Fahrenheit scale, and the Kelvin scale.From temperature – Wikipedia, I learn that there is still a Rankine and a Réaumur scale and a Rémer scale.The development of temperature scales is closely related to the development of physics, which in the 18th century was strongly focused on heat processes. Similar to units of length – think of elbows, inches, feet, … – different temperature scales were developed in the different kingdoms of Europe in parallel, the idea of standardizing such systems of units beyond the spheres of power of the rulers was not widespread at first. The aim has always been to calibrate the temperature scale using available natural processes.
The oldest scale was developed in 1701 by the Danish astronomer Ole Christensen R’mer (R’mer scale – Wikipedia), using the freezing point brine as a zero point and the one of boiling water as the upper fixed point, which he set at 60 R 60 subsections were probably inspired by the classification of the watch (?)).Daniel Gabriel Fahrenheit visited the city of Rimer and would thus be inspired by his temperature scale, which he published in 1714. Fahrenheit used the lowest temperature, which he could reach by means of a mixture of ice, water and salmiak, as the zero point of his scale. As the upper fixed point (96 F) he chose the human body temperature, as the middle point still the freezing point of water (32 F). The choice of numbers, which we find somewhat “crossed” for us, is, in my opinion, in the tradition of the English imperial units of length (see Anglo-American measurement system – Wikipedia) where one calculates less with decimal numbers, but gives parts of a length as a fraction.Since 12 is a number with a large number, scales are often divided as a multiple of 12 (96 = 8 * 12), whereby the freezing point of water is at 1/3 of the upper fixed point. Because Fahrenheit was active in the power of the English king, its scale also prevailed in the English Kingdom, including the United States. Since the upper fixed point is determined by the human body temperature, it is relatively obvious that the definition of this scale cannot be very precise. This led to the development of further temperature scales.
The next development came from the Frenchman Réaumur, who in 1730 defined a temperature scale based on the freezing point and boiling point of water at well-defined pressure and divided into 80 sections.The Réaumur scale – Wikipedia spread throughout France and all of Europe, but had weaknesses in accuracy.In 1741, the Swedish naturalist Anders Celsius developed the still common degrees Celsius – Wikipedia ,which only gradually became more and more popular.
With the advent of the steam engine, the interest of physical research in the thermodynamic processes in such machines and beyond increased.In the course of this, in 1824 William Thomson, 1st Lord Kelvin developed the Kelvin Wikipediascale, which as a zero point the Absolute Zero Point developed by the works in theoretical thermodynamics – Wikipedia the temperature and the classification of the Celsius scale.
Gradually, the different temperature scales (as well as length scales) were unified, some losing their meaning.The definition of the Fahrenheit scale was tied to the Celsius scale at the end of the 19th century: 32F = 0C, 212F = 100C. In 1948, the Celsius scale was redefined directly on the Kelvin scale, so that both Celsius and Fahrenheit scales are only direct translations of the Kelvin scale for everyday use in different countries.