The foundations of modern temperature measurement were laid in 1592 by Galileo Galilei. His glass measuring device was a glass sphere, from which a tube partially filled with water extended from below. The open end of the narrow tube was also submerged in water. If the air in the balloon was cooled, the water in the glass tube rose upward. Such a thermometer could, due to the compression or expansion of air, show the change in temperature, but could not measure the absolute temperature.
Further designs were also based on Galileo's idea, although they used other transmission media. Scientists of the Florentine Academy del Cimento developed the first alcohol thermometer in 1641, and a mercury thermometer in 1657. They used in this case the different expansion of these substances with varying temperature. In a traditional medical thermometer, the so-called maximum thermometer, the expansion of a liquid indicates the maximum temperature over a period of time. In digital medical thermometers, which have recently become widespread, temperature is measured by a sensor whose electrical resistance changes with temperature.
Various scales
The first accurate temperature measurement was carried out in 1714 by the physicist Gabriel Daniel Fahrenheit from Danzig (present-day Gdansk), creating a thermometer with a graduated scale. He took the temperature of a mixture of water and ice with ammonia as zero. In this case, the freezing point of pure water is 32 °, and its boiling point is 212 °. In 1742, the Anders Celsius temperature scale appeared, in which the freezing point of water was taken as 0 °, and its boiling point as 100 °.
- Around 230 BC: Philo of Byzantine discovered that air expands when heated.
- 1624: Jesuit Jean Leurechon used the word "thermometer" for the first time.
- 1731: Peter Van Muschenbrook constructs the first pyrometer for non-contact temperature measurement.
What is warmth? Degrees and temperature
Everyone knows what warmth is. It is known that particles in gases, liquids and solids are in continuous motion and this motion is perceived as heat. The energy of motion of particles, averaged over their huge number, determines the temperature.
The theory of heat did not appear immediately. For a very long time they could not understand what heat is, nor what is the difference between temperature and heat. Many physicists have associated heat with the movement of molecules. So, in particular, Lomonosov thought. But turning general reasoning into rigorous science was not easy.
The story of how they learned to measure temperature is interesting and unusual. Thermometers were invented many years before people knew what they were measuring.
Temperature is associated with very undefined concepts of warmth and cold, which were located in the creation of a person somewhere near smell, taste. From time immemorial, man knew that when two bodies are in close contact, then a thermal equilibrium is established between them. A hand immersed in water turns out to be heated (or cooled) to the same degree as water. There are streams of heat everywhere in nature. In this natural scientists have long seen the manifestation of the great laws of nature.
Ancient scholars and scholars of the Middle Ages compared the properties of attraction and repulsion with heat and cold. Ancient physicians were the first to need a comparative and, moreover, quite accurate scale of body warmth. They noticed a long time ago that a person's health is somehow related to the warmth of his body and that medications can change this quality. The drugs were assigned a cooling or warming effect and the degree of this effect was determined by degrees. The drugs were mixed with each other, and the mixtures had different degrees. "Mixture" in Latin - "temperature" (temperature).
The history of the creation and development of the thermometer
Galileo
None of Galileo's contemporaries could compare with him in his ability to see great laws in simple phenomena. He was one of the first to write about the mechanical nature of heat.
Galileo published a book called "EL saggiatore" (scales for weighing gold), in which he sets out in great detail his views on the nature of physical phenomena. In it, he talks, in particular, about the heating of solids by friction and gives other proofs of the mechanical nature of heat. However, he did not know that mechanically it is possible to heat not only solids, but also liquids or even gases. Galileo was also hampered by the lack of numerical data on heat.
Galileo approached the study of thermal phenomena from the same positions; first of all, he took up how to measure body temperature. The thermometers that Galileo made (about 1597) consisted of a glass ball filled with air; a tube partially filled with water extended from the bottom of the ball, which ended in a vessel also filled with water. The height of the column depended on both temperature and atmospheric pressure, and it was impossible to measure with such a thermometer with any accuracy. Under Galileo, the very idea that air could press on the earth seemed wild enough. Therefore, Galileo's thermometer measured a rather uncertain value, but even such a thermometer made it possible to compare the temperature of different bodies at the same time and in the same place.
Even then, with the help of a still imperfect thermometer, the doctor and anatomist Sanctorius from the University of Padua began to measure the temperature of the human body. For this, he himself, not knowing about Galileo, built a similar thermometer.
Otto von Guerick
The history of the thermometer owes much to one of the most amazing people of the 18th century - Otto von Guericke. He made the first barometer. Similar to Galileo's device. But with a very long tube. Unlike Galileo's device, air was evacuated from Garicke's barometer, so that water filled not only the long tube, but also part of the ball. The barometer was attached to the outside wall of the house, and the air pressure was marked on a scale pointed to by a wooden man floating in a glass ball. Guericke was the first to systematically measure atmospheric pressure and tried to discover the relationship between pressure changes and weather.
Garike also built a relatively good thermometer. It consisted of a brass ball filled with air and a U-shaped tube filled with alcohol. There was a point on his thermometer in the middle of the scale, near which the pointer stopped at the first frost - this point was chosen by Garike as the beginning of the scale. It is clear that such a choice was naive, but still Garike took the first step.
Newton
Let us also mention Newton's work "On the scale of degrees of heat and cold", published in 1701, which describes a 12-degree scale. He placed zero in the same place where we are placing it now - at the freezing point of water, and 12 degrees corresponded to the temperature of a healthy person.
Amontan built a fully sealed thermometer, making it finally completely independent of atmospheric pressure.
The first modern thermometer was described in 1724 by Daniel Fahrenheit, a glass blower from Holland. Different Fahrenheit thermometers could be compared with each other by comparing their readings at different "pivot" points on the scale. Therefore, they became famous for their accuracy. This scale is still in use in England and the United States.
Modern scale Celsius was proposed in 1742. The Swedish physicist did not like negative temperatures, and he found it necessary to turn the old scale and place zero at the boiling point of water, and 100 degrees at its freezing point. But the "inverted scale" did not gain popularity and was very soon "turned" back.
Before the revolution in Russia, the Reaumur scale was adopted (the water point was 0, and the boiling point was 80) - Reaumur thermometers hung on the streets and in all houses. Only in the thirties were they replaced by Celsius thermometers.
What is heat? Thermal equilibrium
By the early 19th century, the thermometer had become a very common device. But for a long time there was no consensus about what the thermometer measures.
Having learned to measure temperature, physicists have not made much progress in understanding what heat is. The concept of "heat" and "temperature" was even more difficult to separate. When a body is heated, its temperature rises. When heat flows from one body to another, the temperature of one body drops and the other rises.
Concept "Thermal equilibrium" very common in heat theory. It is easiest to understand what thermal equilibrium is in the case of a monatomic gas. If the gas in the vessel behaves in such a way that the temperature is the same at all points of the vessel - naturally, the temperature of the vessel walls is also always the same - then the gas is in thermal equilibrium. This means that in such a gas heat does not flow from one part of the vessel to another, neither the pressure nor the chemical composition changes in it, and, in general, from the point of view of classical thermal phenomena, nothing happens in the gas.
Heat always flows so that the temperature is equalized, so that the system goes into a state of thermal equilibrium. The transition to a state of thermal equilibrium can be a complex and rather lengthy process.
Temperature scale. Absolute temperature scale
Temperature scale
In all devices that were invented in the 18th century, temperature measurement was reduced to measuring the length of a column of water, alcohol or mercury. Thermometers worked only in a limited temperature range. The substances filling them froze and boiled, and these thermometers could not measure very low or very high temperatures.
The Celsius scale accurately established the position of two points - 0 and 100 degrees, the distance between which on the scale was divided into equal parts. But the role of each division remained undefined. It was also necessary to understand what happens in the body when the mercury in the thermometer rises by one degree. The easiest way would be to assume that the energy of the body increases by the same amount. This value, referred to a unit of body mass, is called the specific heat capacity.
Absolute temperature scale
The unit of temperature arose by accident - we put the number 100 at the boiling point of water. This act had important consequences: a new gas constant R = 8.3157 joule / degree appeared in the Clapeyron-Clausius law. Such a number arose only because the value of the degree was introduced a very long time ago and all the changes that occur with gases were attributed out of habit to a rather randomly selected temperature scale. It would be more convenient now to change the definition of the degree and "tie" it to the equation of ideal gases. To do this, you just need to reduce the value of the degree by 8.3157 times and assume that the temperature is in such an "ideal gas" scale:
Lord Kelvin's discovery
The question of the meaning of temperature became interested in Thomson (later Lord Kelvin), who in 1848 discovered that a simple but very important conclusion can be drawn from Carnot's theorem. Kelvin noticed that if the work of the Carnot cycle depends only on the temperatures of the heater and the refrigerator, then this makes it possible to establish a new temperature scale that does not depend on the properties of the working fluid.
The Carnot cycle, if it can be carried out between two bodies, allows you to determine the ratio of the temperatures of these two bodies. The temperature scale determined in this way is called absolute temperature scale. In order for the absolute temperature itself to have a certain value, it is necessary to choose some number for one point of the new absolute scale: one numerical value of the temperature must be set arbitrarily. After that, all other values are determined in principle using a Karnot cycle.
Unfortunately, with all the beauty of the theoretical construction of the Kelvin scale, it is very difficult to implement the Carnot cycle in practice. It is difficult to implement a reversible loop, it is difficult to get rid of waste.
Real temperature scale
For many years, two points were chosen for the temperature scale - the melting point of ice and the boiling point of water - and the distance between them was divided into 100 parts, each of which was considered a degree. Such a scale with two reference points has been accepted all over the world.
But this scale had, however, a big drawback from the point of view of measurement accuracy. For her, it was necessary to be able to accurately reproduce both the conditions for melting ice and the conditions for boiling water. It was easier to get by with one reference point, such as the melting point of ice, and measure temperature against the ratio of pressures associated with the ratio of temperatures by the equation of state.
The so-called triple point of water - the temperature at which all three of its phases are carried out in equilibrium: steam - water - ice, is now chosen as a reference reference point. The transition to such a scale went almost unnoticed. Such a reform was carried out in 1954, and now the question of at what temperature ice melts at normal pressure must be answered "at approximately 0".
International temperature scale
A scale with one pivot point is easy to agree with the Kelvin-Mendeleev scale based on Carnot's theorem. The thermodynamic scale does not change if all temperature values are multiplied by the same number. The choice of the pivot point removes this ambiguity.
The thermodynamic scale can only be used in specialized, well-equipped laboratories. Ordinary laboratories use a scale called MPTSh68 (International Practical Temperature Scale, adopted in 1968). In this scale, the boiling point of water is exactly 100 degrees, in addition, there are other reference points to which a certain temperature value is also assigned.
Low temperatures
Interest in obtaining low temperatures arose not only from practical considerations. Physicists have long been interested in the question of whether gases, such as air, oxygen, and hydrogen, can be transformed into a liquid. The beginning of this story dates back to 1877.
In 1877, mining engineer Kayete drops liquid acetylene in a laboratory vessel, in which a leak suddenly opened. The sudden drop in pressure caused fog to form. Almost on the same days, Pictet from Geneva reported a sequential, cascade decrease in various gases, which ended in the production of liquid oxygen at a temperature of -140 degrees Celsius and a pressure of 320 atmospheres.
We must also mention Dewart. Which in 1898 received liquid hydrogen, lowering the temperature to about 129 K. Finally, in 1908, Kamerlingh Onnes in Holland received liquid helium. The temperature that he reached was only 1 degree different from absolute zero.
In 1939, P.L. Kapitsa proved the great efficiency of liquefaction machines, in which gas works with the help of a turbine. Since then, turboexpanders have become widespread. He also proposed the design of an efficient installation for liquefying helium.
Bibliography
Edelman V.S. "Near absolute zero." 1-M., 1987.
Detlaf AA, Yavorskiy BN, "Course of Physics". -M., 1989.
Trofimova T.I. "Course of Physics". 1-M., 1990.
Smorodinsky Ya.A. "Temperature". - M., 1987.
Text taken from the site: www.xreferat.ru
Modern man has long been accustomed to the fact that he is surrounded by useful and "smart" devices. But not everyone realizes how long and often difficult the path of these things through the thickness of centuries was. Take, for example, the familiar medical thermometer, or colloquially a thermometer. It seems that there is nothing more simple and everyday, but in fact he crossed the threshold of our house not so long ago.
First prototypes
The first thermometer - more precisely, an air thermoscope - was completely different from the modern one. It was created in 1597 by one of the titans of the Renaissance, the Italian scientist Galileo Galilei. However, he is not the direct author of the development: Galileo put into practice the ideas of Heron of Alexandria, who has already described a similar device - however, not for measuring the degrees of heat, but for raising water by heating.
To a glass ball the size of a chicken egg, the scientist soldered a thin glass tube. Warming the ball with his hands (and, consequently, the air in it) and turning it over, he immersed the free end of the tube in a vessel with tinted water or wine. As soon as the ball cooled down, the volume of air contained in it decreased, and water, taking its place, rose through the tube. Unlike the modern thermometer, Galileo's device expanded air, not mercury. In addition, it was really just a prototype without a specific measurement scale.
Almost simultaneously with Galileo, not yet knowing about his invention, professor of the University of Padua S. Santorio, a doctor, anatomist and physiologist, created his own device with which he measured the temperature of the human body. In those days, it was believed that the air exhaled by a person comes directly from the heart and carries "vital warmth." It was her that Santorio tried to measure in order to comprehend one of the main secrets of the life of the organism.
His device was quite bulky and also consisted of a ball, but already filled with liquid, as well as a winding barrel with graduations applied to it. The person breathed into the thermometer, or took it in his mouth, or warmed it with his hands (depending on the purpose of the experiment). As a result, Santorio became the first doctor who learned that our body has a constant normal temperature, and assessed its deviation from the norm as a painful condition.
The advent of the classic thermometer
In 1657, Galileo's thermoscope was improved by Florentine scientists. They equipped the device with a bead scale and evacuated air from the reservoir (ball) and tube. This made it possible not only qualitatively, but also quantitatively to compare the temperatures of bodies. Subsequently, the thermoscope was changed: it was turned upside down with a ball, and alcohol was poured into the tube instead of water and the vessel was removed. But since alcohol boils quickly at high temperatures, it was only suitable for measuring cold. And they began to “charge” the thermometer with mercury.
A single scale of degrees, so familiar to us today, did not exist in those days. The famous Fahrenheit and Reaumur proposed their own measurement options, but the decisive word (and subsequently the most extensive application) turned out to be beyond the 100-degree scale developed by the Swedish physicist and astronomer Andersen Celsius. True, at first this system worked "upside down": 0 degrees corresponded to the boiling point of water, and 100 degrees - to the point of ice melting. Subsequently, the scale was turned upside down: according to some information, by the inventor himself, according to others - by the successor of Celsius M. Stroemer, and who believes that it was edited by Karl Linnaeus in 1745. It is in this form that this scale has taken root and has come down to our days.
In addition, at the court of Ferdinand II, the emperor of the Holy Roman Empire, who was known not only as the patron of the arts, but also was the author of a number of physical devices, funny thermometers were created, similar to small frogs. They were executed so subtly and skillfully that they aroused the admiration of contemporaries. These thermometers were designed to measure the temperature of a person's body and were easily attached to the skin with a plaster. The "frogs" cavity was partially filled with liquid, on the surface of which colored balls of various densities floated. When the liquid warmed up, its volume increased slightly, and the density decreased accordingly. And then some of the balls sank to the bottom of the device.
Mercury thermometer in our time
In medical practice, thermometry began to be used much later than in technology. Back in 1861, the German physician Karl Gerhard considered "temperature measurement too complex a procedure to be put into practice and used frequently." One way or another, his prognosis did not prevent the mercury thermometer from taking an honorable place in the arsenal of every general practitioner and almost any home medicine cabinet.
A mercury thermometer is a streamlined glass tube with a capillary containing 2 grams of mercury. These thermometers work due to the fact that during heating and cooling, mercury evenly expands and contracts. Due to these properties, it is also used in barometers and other research instruments. Mercury thermometers have the highest temperature determination accuracy (error no more than 0.1 degrees).
If you follow the rules of use and storage, then such a thermometer will serve you for many years. In addition, it can be bought inexpensively at any pharmacy - except for the EU countries, which have recently been banned due to the high toxicity of liquid metal. Of the minuses of mercury thermometers, in addition to their poisonous filling, it should be noted that the temperature is measured for a long time - about 10 minutes for the most accurate result.
A thermometer must always be at hand, since an increased body temperature is the first sign of an inflammatory process in the body. However, many modern people misuse the information given by the thermometer. It is important to understand that an increase in temperature is NOT the cause of inflammation, but a manifestation of the protective functions of the immune system. Therefore, the temperature below 38 degrees does not need to be brought down with the help of medication - this is a rather stupid way to interfere with recovery. But the temperature is below normal, on the contrary, suggests that the body does not have enough strength to fight on its own.
He arranged something like a thermobaroscope (thermoscope). Galileo studied at this time Heron of Alexandria, who already described a similar device, but not for measuring the degrees of heat, but for raising water by heating. The thermoscope was a small glass ball with a glass tube soldered to it. The ball was slightly heated and the end of the tube was dipped into a vessel with water. After some time, the air in the ball cooled down, its pressure decreased, and the water, under the influence of atmospheric pressure, rose in the tube up to a certain height. Subsequently, with warming, the air pressure in the ball increased and the water level in the tube decreased while cooling, while the water in it rose. With the help of a thermoscope, it was possible to judge only about the change in the degree of heating of the body: it did not show numerical values of temperature, since it did not have a scale. In addition, the water level in the tube depended not only on temperature, but also on atmospheric pressure. In 1657, Galileo's thermoscope was improved by Florentine scientists. They equipped the device with a bead scale and evacuated air from the reservoir (ball) and tube. This made it possible not only qualitatively, but also quantitatively to compare the temperatures of bodies. Subsequently, the thermoscope was changed: it was turned upside down with a ball, and alcohol was poured into the tube instead of water and the vessel was removed. The operation of this device was based on the expansion of measures; the temperatures of the hottest summer day and the coldest winter day were taken as "constant" points. The invention of the thermometer is also credited to Lord Bacon, Robert Fludd, Sanctorius, Scarpi, Cornelius Drebbel ( Cornelius drebbel), Porte and Salomon de Caus, who wrote later and partly had a personal relationship with Galileo. All these thermometers were air and consisted of a vessel with a tube containing air separated from the atmosphere by a column of water; they changed their readings both from temperature changes and from changes in atmospheric pressure.
Mercury medical thermometer
Liquid thermometers are described for the first time in the Saggi di naturale esperienze fatte nell'Accademia del Cimento, where they are spoken of as objects long made by skillful artisans called Confia, who heat glass on a blown fire and make amazing and very delicate products made of it. First, these thermometers were filled with water, and they burst when it froze; they began to use wine alcohol for this in 1654, according to the idea of the Grand Duke of Tuscan Ferdinand II. Florentine thermometers are not only depicted in the Saggi, but have been preserved in several copies to this day in the Galilean Museum in Florence; their preparation is described in detail.
At first, the master had to make divisions on the tube, considering its relative dimensions and the dimensions of the ball: the divisions were applied with molten enamel on a tube heated on a lamp, every tenth was indicated by a white dot, and others by black. Usually, 50 divisions were made in such a way that when the snow melted, the alcohol did not fall below 10, and in the sun did not rise above 40. Good craftsmen made such thermometers so successfully that they all showed the same temperature value under the same conditions, but this did not it was possible to achieve if the tube was divided into 100 or 300 parts in order to obtain greater accuracy. The thermometers were filled by heating the ball and lowering the end of the tube into alcohol, and finishing the filling using a glass funnel with a thinly drawn end that freely fit into a rather wide tube. After adjusting the amount of liquid, the opening of the tube was sealed with sealing wax, called "hermetic". From this it is clear that these thermometers were large and could serve to determine the air temperature, but they were still inconvenient for other, more diverse experiments, and the degrees of different thermometers were not comparable with each other.
The Swedish physicist Celsius finally established both constant points of melting ice and boiling water in 1742, but initially he set 0 ° at the boiling point, and 100 ° at the freezing point, and took the opposite designation only on the advice of M. Störmer. The surviving examples of Fahrenheit thermometers are distinguished by their meticulous workmanship. However, the “inverted” scale turned out to be more convenient, on which the ice melting temperatures were designated 0 C and the boiling point 100 C. This thermometer was first used by the Swedish scientists botanist K. Linnaeus and astronomer M. Stremer. This thermometer is widely used.
See article on how to remove spilled mercury from a broken thermometer. DemercurizationMechanical thermometers
Mechanical thermometer
Window Mechanical Thermometer
Thermometers of this type operate on the same principle as liquid thermometers, but a metal spiral or bimetal tape is usually used as a sensor.
Electric thermometers
Medical Electric Thermometer
The principle of operation of electric thermometers is based on a change in the resistance of a conductor when the ambient temperature changes.
Electric thermometers of a wider range are based on thermocouples (contact between metals with different electronegativity creates a contact potential difference depending on temperature).
Home weather station
The most accurate and stable over time are resistance thermometers based on platinum wire or platinum sputtered on ceramics. The most widely used are PT100 (resistance at 0 ° C - 100Ω) PT1000 (resistance at 0 ° C - 1000Ω) (IEC751). The temperature dependence is almost linear and obeys a quadratic law at positive temperatures and a 4-degree equation at negative temperatures (the corresponding constants are very small, and in the first approximation this dependence can be considered linear). Temperature range -200 - +850 ° C.
Hence, the resistance at T° C, resistance at 0 ° C, and constants (for platinum resistance) -
Optical thermometers
Optical thermometers allow you to record temperature due to the change in the luminosity level, spectrum and other parameters (see Fiber-optic temperature measurement) when the temperature changes. For example, infrared body temperature meters.
Infrared thermometers
An infrared thermometer allows you to measure temperature without direct human contact. In some countries, there has long been a tendency to abandon mercury thermometers in favor of infrared thermometers, not only in medical institutions, but also at the household level.
An infrared thermometer has a number of undeniable advantages, namely:
- safety of use (even with serious mechanical damage, nothing threatens health)
- higher measurement accuracy
- minimum time for the procedure (measurement is carried out within 0.5 seconds)
- possibility of group data collection
Technical thermometers
Technical liquid thermometers are used at enterprises in agriculture, petrochemical, chemical, mining and metallurgical industries, mechanical engineering, housing and communal services, transport, construction, medicine, in a word, in all spheres of life.
There are the following types of technical thermometers:
- technical liquid thermometers TTZH-M;
- bimetallic thermometers TB, TBT, TBI;
- agricultural thermometers TS-7-M1;
- maximum thermometers SP-83 M;
- low-degree thermometers for special cameras SP-100;
- special vibration-resistant thermometers SP-V;
- thermometers mercury electrocontact TPK;
- laboratory thermometers TLS;
- thermometers for petroleum products TN;
- thermometers for testing petroleum products TIN1, TIN2, TIN3, TIN4.
Before the invention of such an ordinary and simple measuring device for our everyday life, people could judge about a thermal state only by their direct sensations: warm or cool, hot or cold.
The history of thermodynamics began when, in 1592, he created the first device for observing changes in temperature, called it a thermoscope. The thermoscope was a small ball with a soldered glass tube. The ball was heated and the end of the tube was dipped into water. When the ball cooled down, the pressure in it decreased, and the water in the tube, under the influence of atmospheric pressure, rose to a certain height upward.
With warming, the water level in the tubes went down. The disadvantage of the device was that it could only be used to judge the relative degree of heating or cooling of the body, since it did not yet have a scale.
Later, Florentine scientists improved Galileo's thermoscope by adding a bead scale to it and pumping air out of the ball.
In the 17th century, the aerial thermoscope was transformed into an alcoholic one by the Florentine scientist Torricelli. The device was turned upside down with a ball, the vessel with water was removed, and alcohol was poured into the tube. The operation of the device was based on the expansion of alcohol when heated, - now the readings did not depend on atmospheric pressure. It was one of the first liquid thermometers.
At that time, the readings of the instruments were not yet consistent with each other, since no specific system was taken into account when calibrating the scales. In 1694, Carlo Renaldini proposed to take the temperature of melting ice and the boiling point of water as the two extreme points.
In 1714 D.G. Fahrenheit made a mercury thermometer. On the scale, he marked three fixed points: the lower, 32 ° F - the freezing point of the saline solution, 96 ° - the human body temperature, the upper 212 ° F - the boiling point of water. The Fahrenheit thermometer was used in English-speaking countries until the 70s of the 20th century, and it is still used in the United States.
Another scale was proposed by the French scientist Réaumur in 1730. He experimented with an alcohol thermometer and came to the conclusion that the scale can be constructed in accordance with the thermal expansion of alcohol. Having established that the alcohol used by him, mixed with water in a 5: 1 ratio, expands in a ratio of 1000: 1080 when the temperature changes from the freezing point to the boiling point of water, the scientist suggested using a scale from 0 to 80 degrees. Taking for 0 ° the temperature of ice melting, and for 80 ° the boiling point of water at normal atmospheric pressure.
In 1742, the Swedish scientist Andres Celsius proposed a scale for a mercury thermometer, in which the interval between the extreme points was divided by 100 degrees. At the same time, at first, the boiling point of water was designated as 0 °, and the melting temperature of ice was designated as 100 °. However, in this form, the scale turned out to be not very convenient, and later the astronomer M. Stremer and the botanist K. Linnaeus decided to change the extreme points in places.
M.V. Lomonosov proposed a liquid thermometer with a scale of 150 divisions from the melting point of ice to the boiling point of water. I.G. Lambert was responsible for the creation of an air thermometer with a scale of 375 °, where one degree was taken to be one thousandth of the expansion of the volume of air. There have also been attempts to create a thermometer based on the expansion of solids. So in 1747 the Dutchman P. Muschenbrug used the expansion of the bar to measure the melting temperature of a number of metals.
By the end of the 18th century, the number of different temperature scales increased significantly. According to Lambert's "Pilometrics" at that time, there were 19 of them. The temperature scales discussed above are distinguished by the fact that the reference point for them was chosen arbitrarily.
In 1848, the English physicist William Thomson (Lord Kelvin) proved the possibility of creating an absolute temperature scale, the zero of which does not depend on the properties of water or the substance filling. The reference point in the "Kelvin scale" was the value of absolute zero: −273.15 ° C. At this temperature, the thermal movement of molecules stops. Consequently, further cooling of bodies becomes impossible.
This is the basic history of the emergence of the thermometer and thermometric scales. Today, thermometers with a Celsius scale, Fahrenheit (in the USA), and also with a Kelvin scale are used in scientific research. Currently, temperature is measured using instruments whose operation is based on the various thermometric properties of liquids, gases and solids. And if in the 18th century there was a real "boom" of discoveries in the field of temperature measurement systems, then from the last century a new era of discoveries began in the field of temperature measurement methods.
Today there are many devices used in industry, in everyday life, in scientific research - expansion thermometers and manometric thermometers, thermoelectric and resistance thermometers, as well as pyrometric thermometers that allow you to measure temperature in a non-contact way.
