Mankind learned to measure temperature about 400 years ago. But the first devices reminiscent of current thermometers appeared only in the X V III century. The inventor of the first thermometer was the scientist Gabriel Fahrenheit. In total, several different temperature scales were invented in the world, some of them were more popular and are still in use, others were gradually phased out.
Temperature scales are systems of temperature values that can be compared with each other. Since the temperature does not apply to the values to be directly measured, its value is associated with a change in the temperature state of a substance (for example, water). On all temperature scales, as a rule, two points are fixed corresponding to the transition temperatures of the selected thermometric substance in different phases. These are the so-called reference points. Examples of reference points are the boiling point of water, the hardening point of gold, etc. One of the points is taken as the reference point. The interval between them is divided into a certain number of equal segments, which are single. One degree is universally accepted as one degree.
The most popular and most widely used temperature scales in the world are the Celsius and Fahrenheit scales. However, we will examine in order the available scales and try to compare them in terms of ease of use and practical benefit. The most famous scales are five:
1. The Fahrenheit scale was invented by Fahrenheit, a German scientist. On one of the cold winter days of 1709, the scientist’s mercury in the thermometer dropped to a very low temperature, which he proposed to take as zero on a new scale. Another reference point was the temperature of the human body. The freezing temperature of water on its scale became + 32 °, and the boiling point + 212 °. The Fahrenheit scale is not particularly thought out and convenient. Previously, it was widely used in English-speaking countries, now - almost exclusively in the United States.
2. According to the Reaumur scale, invented by the French scientist Rene de Reaumur in 1731, the freezing point is the lower reference point. The scale is based on the use of alcohol, which expands when heated, a thousandth of the volume of alcohol in the tank and tube at zero was taken as a degree. Now this scale is out of use.
3. According to the Celsius scale (proposed by the Swede Anders Celsius in 1742), the temperature of the mixture of ice and water (the temperature at which ice melts) is taken as zero, the other main point is the temperature at which water boils. It was decided to divide the interval between them into 100 parts, and one part was taken as a unit of measurement - degrees Celsius. This scale is more rational than the Fahrenheit scale and the Reaumur scale, and is now used everywhere.
4. The Kelvin scale was invented in 1848 by Lord Kelvin (English scientist W. Thomson). On it, the zero point corresponded to the lowest possible temperature at which the movement of the molecules of the substance ceases. This value was theoretically calculated when studying the properties of gases. On the Celsius scale, this value corresponds to approximately - 273 ° C, i.e. zero Celsius is 273 K. The unit of measurement for the new scale was one kelvin (originally called “Kelvin degree”).
5. The Rankin scale (after the name of the Scottish physicist W. Rankin) has the same principle as the Kelvin scale, and the dimension is the same as the Fahrenheit scale. This system is practically not widespread.
The temperatures that the Fahrenheit and Celsius scales give us can be easily converted into each other. When translating “in the mind” (that is, quickly, without using special tables), the Fahrenheit values in degrees Celsius need to be reduced by 32 units and multiplied by 5/9. On the contrary (from the Celsius to Fahrenheit scale) - multiply the initial value by 9/5 and add 32. For comparison: the absolute zero temperature in Celsius is 273.15 ° C, in Fahrenheit - 459.67 °.