If, during a reversible Carnot cycle, a body absorbs heat 0, at temperature T, and releases heat C? 3 at temperature T 2, then the following equality must be observed:

THAT,

n<Г (21)

Measurement of thermal energy quantities

One of the most important thermal energy quantities is temperature. Temperature is a physical quantity that characterizes the degree of heating of a body or its thermal energy potential. Almost all technological processes and various properties of a substance depend on temperature.

Unlike such physical quantities as mass, length, etc., temperature is not an extensive (parametric), but an intensive (active) quantity. If a homogeneous body is divided in half, then its mass is also divided in half. Temperature, being an intensive quantity, does not have this property of additivity, i.e. For a system in thermal equilibrium, every part of the system has the same temperature. Therefore, it is not possible to create a temperature standard, just as standards of extensive quantities are created.

Temperature can only be measured indirectly, based on the temperature dependence of such physical properties of bodies that can be directly measured. These properties of bodies are called thermometric. These include length, density, volume, thermoelectric power, electrical resistance, etc. Substances characterized by thermometric properties are called thermometric. The instrument for measuring temperature is called a thermometer. To create a thermometer, you must have a temperature scale.

The temperature scale is a specific functional numerical relationship between temperature and the values ​​of the measured thermometric property. In this regard, it seems possible to construct temperature scales based on the choice of any thermometric property. At the same time, there is no general thermometric property that is linearly related to temperature changes and does not depend on other factors over a wide range of temperature measurements.

The first temperature scales appeared in the 18th century. To construct them, two reference points t 1 and t 2 were selected, representing the phase equilibrium temperatures of pure substances. The temperature difference t 2 - t 1 is called main temperature range. The German physicist Gabriel Daniel Fahrenheit (1715), the Swedish physicist Anders Celsius (1742) and the French physicist René Antoine Reaumur (1776) when constructing scales were based on the assumption of a linear relationship between temperature t and thermometric property, which was used as expansion of the volume of liquid V, i.e.

t = a + bV, (1)

Where A And b– constant coefficients.

Substituting V = V 1 at t = t 1 and V = V 2 at t = t 2 into this equation, after transformation we obtain the temperature scale equation:

In the Fahrenheit, Reaumur and Celsius scales, the melting point of ice t 1 corresponded to +32 0, 0 0 and 0 0, and the boiling point of water t 2 - 212 0, 80 0 and 100 0. The main interval t 2 - t 1 in these scales is divided respectively into N = 180, 80 and 100 equal parts, and the 1/N part of each interval is called the Fahrenheit degree - t 0 F, the Reaumur degree t 0 R and the Celsius degree t 0 C Thus, for scales constructed according to the said principle, a degree is not a unit of measurement, but represents a unit interval - a scale scale.

To convert temperature from one scale to another, use the following ratio:

(3)

Later it was found that the readings of thermometers with different thermometric substances (mercury, alcohol, etc.), using the same thermometric property and a uniform degree scale, coincide only at reference points, and at other points the readings diverge. The latter is especially noticeable when measuring temperatures whose values ​​are located far from the main interval.

This circumstance is explained by the fact that the relationship between temperature and thermometric property is actually nonlinear and this nonlinearity is different for different thermometric substances. In particular, the nonlinearity between temperature and change in liquid volume is explained by the fact that the temperature coefficient of volumetric expansion of the liquid itself changes with temperature and this change is different for different droplet liquids.

Based on the described principle, you can build any number of scales that differ significantly from each other. Such scales are called conventional, and the scales of these scales are called conventional degrees.

The problem of creating a temperature scale independent of the thermometric properties of substances was solved in 1848 by Kelvin, and the scale he proposed was called thermodynamic. Unlike conventional temperature scales, the thermodynamic temperature scale is absolute.

Thermodynamic temperature scale based on the use of the second law of thermodynamics. In accordance with this law, the efficiency h of a heat engine operating according to the reverse Carnot cycle is determined only by the temperature of the heater T n and the refrigerator T x and does not depend on the properties of the working substance:

(4)

where Q n and Q x are, respectively, the amount of heat received by the working substance from the heater and given to the refrigerator.

Kelvin proposed to use the equality to determine temperature

Therefore, by using one object as a heater and another as a refrigerator and running a Carnot cycle between them, it is possible to determine the temperature ratio of the objects by measuring the ratio of heat taken from one object and given to the other. The resulting temperature scale does not depend on the properties of the working substance and is called the absolute temperature scale. In order for the absolute temperature to have a certain value, it was proposed to take the difference in thermodynamic temperatures between the boiling points of water T kv and the melting points of ice T tl equal to 100 0. The adoption of such a difference pursued the goal of maintaining the continuity of the numerical value of the thermodynamic temperature scale from the centigrade Celsius temperature scale. T.O., denoting the amount of heat received from the heater (boiling water) and given to the refrigerator (melting ice), respectively, through Q kv and Q tl, and taking T kv - T tl = 100, we obtain:

And (6)

For any temperature T of the heater, with a constant value of T tl of the refrigerator and the amount of heat Q t given to it by the working substance of the Carnot machine, we will have:

(7)

Equation (6) is the equation centigrade thermodynamic temperature scale and shows that the temperature value T on this scale is linearly related to the amount of heat Q received by the working substance of a heat engine when it performs a Carnot cycle, and, as a consequence, does not depend on the properties of the thermodynamic substance. One degree of thermodynamic temperature is taken to be the difference between the body temperature and the melting temperature of ice at which the work performed in the reverse Carnot cycle is equal to 1/100 of the work done in the Carnot cycle between the boiling point of water and the melting temperature of ice (provided that in both cycles the amount of heat given off to the refrigerator is the same).

From the definition of efficiency it follows that when maximum value h=1 must be equal to zero T x. This lowest temperature was called absolute zero by Kelvin. Temperature on the thermodynamic scale is designated “K”.

The thermodynamic temperature scale, based on two reference points, has insufficient measurement accuracy. It is practically difficult to reproduce the temperatures of these points, because they depend on pressure, as well as on the salt content in the water. Therefore, Kelvin and Mendeleev expressed the idea of ​​the feasibility of constructing a thermodynamic temperature scale based on one reference point.

The Advisory Committee on Thermometry of the International Committee of Weights and Measures in 1954 adopted a recommendation to move to the definition of a thermodynamic scale using a single reference point - the triple point of water (the equilibrium point of water in the solid, liquid and gaseous phases), which is easily reproduced in special vessels with an error no more than 0.0001 K. The temperature of this point is taken to be 273.16 K, i.e. higher than the melting temperature of ice by 0.01 K. This number was chosen so that the temperature values ​​​​on the new scale practically do not differ from the old Celsius scale with two reference points. The second reference point is absolute zero, which is practically not realized, but has a strictly fixed position.

In 1967, the XIII General Assembly of Weights and Measures clarified the definition of the unit of thermodynamic temperature as follows: “ Kelvin– 1/273.16 part of the thermodynamic temperature of the triple point of water.” Thermodynamic temperature can also be expressed in degrees Celsius:

t = T– 273.15 K (8)

Currently, the International Practical Temperature Scale MPSHT-68 is recommended for use. The unit of temperature is Kelvin (K). The temperature determined on this scale is called thermodynamic T(For example, T= 300 K).

It is also possible to use temperature t on the Celsius scale, defined by the expression

t = T - 273,15. (2)

This temperature is expressed in degrees Celsius °C (for example, t = 20 °C). Kelvin and degrees Celsius have the same magnitude and are both equal to 1/100 of the difference between the boiling and freezing points of water at atmospheric pressure.

The Kelvin and Celsius scales differ only in the reference point: the zero in the Kelvin scale is shifted down by 273.15 K compared to the Celsius scale. Temperature on the Celsius scale can be negative t < 0 °С, тогда как термодинамическая температура всег­да положительнаT> 0. As the thermodynamic temperature approaches zero ( T > 0) inside the body, the molecules gradually slow down their vibrational motion near the equilibrium state, and when T= 0 it stops.

The peculiar “guardians” of temperature scales are the constant temperatures of phase equilibrium between two or three phases of a substance: boiling and solidification temperatures, triple point temperatures. These temperature values ​​are called reference points. The values ​​of the main reference points of MPShT-68 are given in table. 1.

Table1. Main reference points MPShT-68

Fahrenheit temperature scales are still quite often used abroad ( t, °F) and Rankine (T, °R). They are expressed as follows in terms of Celsius and Kelvin temperatures, respectively:

t°C = (t° F - 32)/1,8; (3)

T = T° R / 1,8 . (4)

4. Temperature measurement methods

Temperature is a measure of the kinetic energy of the molecules that make up a body. The kinetic energy of the molecules that make up the body cannot be measured. Therefore, to measure temperature, indirect methods are used, in which the dependence of some properties of a substance on temperature is used and the change in temperature is judged by changes in these properties. Such properties are the volume of the substance, saturated vapor pressure, electrical resistance, thermoelectromotive force, thermal radiation, etc.

Glass liquid thermometers. The operating principle of glass liquid thermometers is based on the thermal expansion of liquids. In order for the change in the volume of liquid with a change in temperature to be clearly visible, usually a tube with a thin channel - a capillary - is adjacent to the volume of liquid enclosed in the reservoir. The free surface of the liquid is located in this capillary, as a result of which small temperature changes in the volume of the liquid cause a large, clearly observable movement of the free surface of the meniscus in the capillary. At known temperatures t 1 And t 2 two positions of the meniscus are determined, after which the distance between them is divided into equal segments, equal in number t 1 - t 2 . The thermometer is calibrated in this way, and only after these divisions are marked on the scale can it be used for measurement.

Glass thermometers can be used to measure temperatures in the range from -200 to +750 °C, but usually up to temperatures not exceeding 150-200 °C. To fill them, depending on the range of measured temperatures, various, usually tinted, liquids are used: mercury, toluene, ethanol etc.

Disadvantages of liquid thermometers: relatively large size, the need to visually determine the temperature and the inability to represent the readings in the form of an electrical signal.

Resistance thermometers. Resistance thermometers use the property of changing the electrical resistance of metals when its temperature changes. Resistance thermometers are used to measure a wide range of temperatures. The platinum resistance thermometer is a reference instrument for measuring temperatures in the range from 13.81 to 903.89 K. The design of the platinum resistance thermometer is shown in Fig. 2. Platinum wire with a diameter of 0.05-0.10 mm, twisted into a spiral, is laid on a helicoid-shaped quartz frame. Leads made of platinum wire are soldered to the ends of the spiral. The entire device is placed in a protective quartz tube. The resistance of a platinum thermometer is usually measured using a potentiometric method (the schematic diagram is shown in Fig. 3).

Rice. 2. Platinum resistance thermometer: a - sensitive part, b - thermometer head; 1 - protective quartz tube; 2 - quartz frame; 3 - spiral made of platinum wire; 4 - platinum leads; 5 - contact screws; 6 - insulating gasket

Instead of platinum, other metals or semiconductor materials can be used in resistance thermometers. The main disadvantage of resistance thermometers is the rather large dimensions of the sensitive part.

Rice. 3. Schematic diagram of measuring the resistance of a platinum thermometer:

1 - potentiometer

Thermoelectric thermometers. Thermoelectric thermometers (thermocouples) are widely used both in laboratory practice and in industrial production. This is due to their unique properties.

A thermocouple is two dissimilar metal conductors (wires of different metals) that make up a common electrical circuit. If the temperatures of the connections (junctions) of the conductors t 1 And t 2 are not the same, then thermoEMF arises and electric current flows through the circuit. The reason for the occurrence of thermoEMF is the different density of free electrons in different metals at the same temperature. The greater the temperature difference between the junctions, the greater the thermoEMF. The thermoEMF value is used to judge the temperature difference between the junctions.

The thermocouple electrodes are wire with a diameter of 0.1-3.2 mm. The following thermocouples are used: platinum-rhodium-platinum (from 0 to 1300 °C), platinum-rhodium (from 300 to 1600 °C), tungsten-rhenium (from 0 to 2200 °C), chromel-alumel (from -200 to 1000 °C), chromel -copel (from -50 to 600 °C), copper-copel (from -200 to 100 °C) and others.

When measuring temperature, one junction of the thermocouple circuit, the so-called cold junction, is located at 0 ° C (in melting ice in a Dewar flask), and the other - the hot junction - is in the environment whose temperature needs to be measured. ThermoEMF tables for thermocouples have been compiled specifically for this case. If for some reason it is not possible to place the cold junction in an environment with a temperature of 0 °C and it is at room temperature (for example, at 20 °C), then in this case the resulting thermoEMF corresponds to the temperature difference between the hot and cold junctions and when determining the temperature it is necessary correct for the cold junction. To do this, it is necessary to add the measured thermoEMF with the thermoEMF corresponding to the temperature of the cold junction (20 °C), and from the resulting value determine the temperature using tables.

According to the connection diagram, thermocouples with one and two cold junctions are distinguished.

Fig.4. Types of thermocouples: 1 – hot junction; 2 – cold junction

The circuit diagram of a thermocouple with one cold junction is shown in Fig. 4, a. The entire circuit is made of two dissimilar conductors. A millivoltmeter is included in the circuit to measure thermoEMF.

A circuit with two cold junctions is shown in Fig. 4.6. The difference between this circuit and the first one is that copper wires are introduced into the thermocouple circuit. Copper wires are shown as a solid line. This scheme is usually used in practice due to the fact that the measuring device may be located at a considerable distance from the place where the temperature is measured.

A significant advantage of thermocouples and resistance thermometers is that they convert the measured temperature values ​​into an electrical signal. This makes it possible to transmit a signal over long distances, and also use it as a control signal in automatic regulation and control systems.

Infrared thermometers. Infrared thermometers contain a highly sensitive sensor that converts the energy of infrared (thermal) radiation from the surface of an object into an electrical signal. This information is then converted into temperature data that is displayed digitally on the display. The quantitative relationship between the intensity of thermal radiation of a surface and its temperature is established by the Stefan-Boltzmann law for thermal radiation. The temperature measurement range of such a device is from -50 o C to 1500 o C.

An infrared thermometer allows you to measure surface temperature in a non-contact manner and over a considerable distance. This makes it especially convenient in cases where other methods of temperature measurement are unsuitable. For example, if you need to measure the temperature of a moving object, a live surface, or a hard-to-reach surface. The device is usually made in the form of a pistol. A laser pointer is used to select a temperature measurement point on the surface.

Temperature scales

The temperature scale is a specific functional numerical relationship between temperature and the values ​​of the measured thermometric property. In this regard, it seems possible to construct a temperature scale based on the choice of any thermometric property. At the same time, there is not a single thermometric property that varies linearly with

changes in temperature and does not depend on other factors over a wide range of temperature measurements. The first scales appeared in the 18th century. To construct them, two reference points were selected t 1 And t 2, representing the phase equilibrium temperatures of pure substances. Temperature difference t 1 –t 2 called the main temperature range.

Fahrenheit (1715), Reaumur (1776) and Celsius (1742) when constructing scales were based on the assumption of a linear relationship between temperature t and thermometric property, which was used as expansion of the volume of liquid V(formula 14.27) /8/

t=a+bV,(14.27)

Where A And b- constant coefficients.

Substituting into equation (14.27) V=V 1 at t=t 1 And V=V 2 at t=t 2, after transformations we obtain equation (14.28) of the temperature scale /8/

In the Fahrenheit, Reaumur and Celsius scales, the melting point of ice t 1 corresponded to +32, 0 and 0 °, and the boiling point of water t 2 - 212, 80 and 100°. Main interval t 2 –t 1 in these scales it is divided accordingly into N= 180, 80 and 100 equal parts, and 1/N part of each interval is called a degree Fahrenheit - t° F, degree Reaumur – t° R and degrees Celsius - t °С. Thus, for scales constructed according to the specified principle, the degree is not a unit of measurement, but represents a unit interval - the scale of the scale.

To convert temperature from one specified scale to another, use relation (14.29)

t°С= 1.25° R=-(5/9)( - 32), (14.29)

Later it was found that the readings of thermometers with different thermometric substances (for example, mercury, alcohol, etc.), using the same thermometric property and a uniform degree scale, coincide only at reference points, and at other points the readings diverge. The latter is especially noticeable when measuring temperatures whose values ​​are located far from the main interval.

This circumstance is explained by the fact that the relationship between temperature and thermometric property is actually nonlinear and this nonlinearity is different for different thermometric substances. In particular, in the case under consideration, the nonlinearity between temperature and change in liquid volume is explained by the fact that the temperature coefficient of volumetric expansion of the liquid itself varies with temperature and this change is different for different droplet liquids.

Based on the described construction principle, any number of temperature scales can be obtained, differing significantly from each other. Such scales are called conventional, and the scales of these scales are called conventional degrees. The problem of creating a temperature scale independent of the thermometric properties of substances was solved in 1848 by Kelvin, and the scale he proposed was called thermodynamic. Unlike conventional temperature scales, the thermodynamic temperature scale is absolute.

Thermodynamic temperature scale based on the use of the second law of thermodynamics. In accordance with this law, the efficiency coefficient of a heat engine operating at reversible cycle Carnot, determined only by heater temperatures T N and refrigerator T X and does not depend on the properties of the working substance, thus the efficiency is calculated using formula (14.30) /8/

(14.30)

Where Q N And Q X- respectively, the amount of heat received by the working substance from the heater and given to the refrigerator.

Kelvin proposed to use equality (14.31) /8/ to determine temperature

T N /T X = Q N /Q X , (14.31)

Therefore, by using one object as a heater and another as a refrigerator and running a Carnot cycle between them, it is possible to determine the temperature ratio of the objects by measuring the ratio of heat taken from one object and given to the other. The resulting temperature scale does not depend on the properties of the working (thermometric) substance and is called the absolute temperature scale. In order for the absolute temperature (and not just the ratio) to have a certain value, it was proposed to take the difference in thermodynamic temperatures between the boiling points of water T HF and melting ice T TL equal to 100°. The adoption of such a value of the difference pursued the goal of maintaining continuity numerical expression thermodynamic temperature scale from the centigrade Celsius temperature scale. Thus, denoting the amount of heat received from the heater (boiling water) and given to the refrigerator (melting ice), respectively, by Q HF And Q TL and accepting T KV – T TL ==100, using (14.31), we obtain equality (14.32) and (14.33)

(14.32)

(14.33)

For any temperature T heater at a constant temperature value T TL refrigerator and amount of heat Q TL, given to it by the working substance of the Carnot machine, we will have the equality (14.34) /8/

(14.34)

Expression (14.34) is the equation centigrade thermodynamic temperature scale and shows that the temperature value T on this scale is linearly related to the amount of heat Q, obtained by the working substance of a heat engine when it performs a Carnot cycle, and, as a consequence, does not depend on the properties of the thermometric substance. One degree of thermodynamic temperature is taken to be the difference between the body temperature and the melting temperature of ice at which the work performed in the reversible Carnot cycle is equal to 1/100 of the work done in the Carnot cycle between the boiling point of water and the melting temperature of ice (provided that in both cycles the amount of heat given off to the refrigerator is the same). From expression (14.30) it follows that at the maximum value it should be equal to zero T X. This lowest temperature was called absolute zero by Kelvin. Temperature on the thermodynamic scale is denoted by T K. If in the expression describing the Gay-Lussac gas law: (where Ro - pressure at t=0 °С; is the temperature coefficient of pressure), substitute the temperature value equal to - , then the gas pressure P t will become equal to zero. It is natural to assume that the temperature at which the maximum minimum gas pressure is ensured is itself the minimum possible, and is taken as zero on the absolute Kelvin scale. Therefore, the absolute temperature is .

From the Boyle-Mariotte law it is known that for gases the temperature coefficient of pressure a is equal to the temperature coefficient of volumetric expansion. It was experimentally found that for all gases at pressures tending to zero, in the temperature range 0-100 °C, the temperature coefficient of volumetric expansion = 1/273.15.

Thus, the zero absolute temperature value corresponds to °C. The ice melting temperature on an absolute scale will be That==273.15 K. Any temperature on the absolute Kelvin scale can be defined as (Where t temperature in °C). It should be noted that one degree Kelvin (1 K) corresponds to one degree Celsius (1 °C), since both scales are based on the same reference points. The thermodynamic temperature scale, based on two reference points (the melting temperature of ice and the boiling point of water), had insufficient measurement accuracy. It is practically difficult to reproduce the temperatures of these points, since they depend on changes in pressure, as well as on minor impurities in the water. Kelvin and, independently of him, D.I. Mendeleev expressed considerations about the advisability of constructing a thermodynamic temperature scale based on one reference point. The Advisory Committee on Thermometry of the International Committee of Weights and Measures in 1954 adopted a recommendation to move to the definition of a thermodynamic scale using one reference point - the triple point of water (the equilibrium point of water in the solid, liquid and gaseous phases), which is easily reproduced in special vessels with with an error of no more than 0.0001 K. The temperature of this point is taken to be 273.16 K, i.e. higher than the temperature of the ice melting point by 0.01 K. This number was chosen so that the temperature values ​​​​on the new scale practically do not differ from the old Celsius scale with two reference points. The second reference point is absolute zero, which is not realized experimentally, but has a strictly fixed position. In 1967, the XIII General Conference on Weights and Measures clarified the definition of the unit of thermodynamic temperature as follows: "Kelvin-1/273.16 part of the thermodynamic temperature of the triple point of water." Thermodynamic temperature can also be expressed in degrees Celsius: t= T- 273.15 K. The use of the second law of thermodynamics, proposed by Kelvin for the purpose of establishing the concept of temperature and constructing an absolute thermodynamic temperature scale, independent of the properties of the thermometric substance, is of great theoretical and fundamental importance. However, the implementation of this scale using a heat engine operating on a reversible Carnot cycle as a thermometer is practically impossible.

Thermodynamic temperature is equivalent to the gas-thermal temperature used in the equations describing the ideal gas laws. The gas-thermal temperature scale is built on the basis of a gas thermometer, in which a gas with properties approaching those of ideal gas. Thus, the gas thermometer is a practical means of reproducing the thermodynamic temperature scale. Gas thermometers come in three types: constant volume, constant pressure and constant temperature. Usually a gas thermometer of constant volume is used (Figure 14.127), in which the change in gas temperature is proportional to the change in pressure. A gas thermometer consists of a cylinder 1 and connecting tube 2, filled through the valve 3 hydrogen, helium or nitrogen (for high temperatures). Connecting tube 2 connected to the handset 4 two-pipe pressure gauge, which has a tube 5 can be moved up or down thanks to the flexible connecting hose 6. When the temperature changes, the volume of the system filled with gas changes, and to bring it to its original value, the tube 5 move vertically until the mercury level in the tube 4 does not coincide with the axis X-X. In this case, the column of mercury in the tube 5, measured from level X-X, will correspond to gas pressure R in a cylinder.

Figure 14.127 – Gas thermometer diagram

Typically measured temperature T determined relative to some reference point, for example, relative to the temperature of the triple point of water T0, at which the gas pressure in the cylinder will be Ro. The desired temperature is calculated using formula (14.35)

(14.35)

Gas thermometers are used in the range ~ 2- 1300 K. The error of gas thermometers is in the range of 3-10-3 - 2-10-2 K depending on the measured temperature. Achieving such a high measurement accuracy is a complex task that requires taking into account numerous factors: deviations of the properties of a real gas from an ideal one, the presence of impurities in the gas, sorption and desorption of gas by the walls of the cylinder, diffusion of gas through the walls, change in the volume of the cylinder from temperature, temperature distribution along the connecting tube.

Due to the high labor intensity of working with gas thermometers, attempts were made to find more simple methods reproduction of the thermodynamic temperature scale.

Based on research carried out in various countries at the VII General Conference on Weights and Measures in 1927, it was decided to replace the thermodynamic scale "practical" temperature scale and call her international temperature scale. This scale was consistent with the centigrade thermodynamic scale as closely as the level of knowledge at that time allowed.

To construct the international temperature scale, six reproducible reference points were selected, the temperature values ​​of which on the thermodynamic scale were carefully measured in various countries using gas thermometers and the most reliable results were accepted. Using reference points, reference instruments are calibrated to reproduce the international temperature scale. In the intervals between reference points, temperature values ​​are calculated using the proposed interpolation formulas, which establish a connection between the readings of reference instruments and temperature on the international scale. In 1948, 1960 and 1968 A number of clarifications and additions were made to the provisions on the international temperature scale, since, based on improved measurement methods, differences were discovered between this scale and the thermodynamic scale, especially in the region of high temperatures, and also due to the need to extend the temperature scale to lower temperatures. Currently, an improved scale adopted at the XIII Conference on Weights and Measures, called the “international practical temperature scale 1968” (MPTP-68), is in effect. The term "practical" indicates that this temperature scale is not generally the same as the thermodynamic scale. MPTSH-68 temperatures are provided with an index ( T 68 or t 68).

MPTS-68 is based on 11 main reference points shown in Table 9. Along with the main ones, there are 27 secondary reference points, covering the temperature range from 13.956 to 3660 K (from - 259.194 to 3387 ° C). The numerical temperatures given in Table 14.4 correspond to the thermodynamic scale and were determined using gas thermometers.

A platinum resistance thermal converter is used as a reference thermometer in the temperature range from 13.81 to 903.89 K (630.74 °C - the solidification point of antimony - a secondary reference point). This interval is divided into five subintervals, for each of which interpolation formulas are defined in the form of polynomials up to the fourth degree. In the temperature range from 903.89 to 1337.58 K, a reference platinum-platinum-rhodium thermoelectric thermometer is used. The interpolation formula connecting the thermoelectromotive force with temperature is here a polynomial of the second degree.

For temperatures above 1337.58 K (1064.43°C), MPTS-68 is reproduced using a quasi-monochromatic thermometer using Planck's radiation law.

Table 14.4 - Main reference points MPTSH-68

Content:

Introduction

Temperature and thermometers - history of occurrence

Temperature scales and their types

1. Fahrenheit

   Reaumur scale

   Celsius

   Kelvin scale

Absolute zero temperatures

The influence of temperature conditions on life on Earth

Conclusions

Thermometers and temperature. History of origin.

What is temperature

Before we start talking about temperature sensors, you should understand what they are.temperature from a physics point of view . Why does the human body feel a change in temperature, why do we say that today it is warm or just hot, and the next day it is cool, or even cold.

The term temperature comes from the Latin word temperatura, which means normal condition or proper offset. As a physical quantity, temperature characterizes the internal energy of a substance, the degree of mobility of molecules, and the kinetic energy of particles in a state of thermodynamic equilibrium.

As an example, consider air, whose molecules and atoms move chaotically. When the speed of movement of these particles increases, then the air temperature is said to be high, the air is warm or even hot. On a cold day, for example, the speed of movement of air particles is low, which feels like pleasant coolness or even “dog cold.” Please note that the speed of movement of air particles does not depend in any way on the speed of the wind! This is a completely different speed.

This is what concerns air, molecules can move freely in it, but what is the situation in liquid and solid bodies? In them, thermal motion of molecules also exists, although to a lesser extent than in air. But its change is quite noticeable, which determines the temperature of liquids and solids.

Molecules continue to move even at the melting temperature of ice, as well as at negative temperatures. For example, the speed of a hydrogen molecule at zero temperature is 1950 m/sec. Every second, a thousand billion molecular collisions occur in 16 cm^3 of air. As the temperature increases, the mobility of molecules increases, and the number of collisions accordingly increases.

However, it should be noted thattemperature Andwarm the essence is not the same thing. A simple example: a regular gas stove in the kitchen has large and small burners that burn the same gas. The combustion temperature of the gas is the same, so the temperature of the burners themselves is also the same. But the same volume of water, for example a kettle or a bucket, will boil faster on a large burner than on a small one. This happens because a larger burner produces more heat, burning more gas per unit time, or has more power.

The first thermometers

Before the invention of such an ordinary and simple measuring device for our everyday life as a thermometer, thermal state people could judge only by their immediate sensations: warm or cool, hot or cold.

The word “temperature” arose a long time ago - the molecular kinetic theory did not yet exist. It was believed that bodies contained a certain matter called “caloric,” and that warm bodies contained more of it than cold bodies. Temperature, thus, characterized the mixture of caloric and the substance of the body itself, and the higher the temperature, the stronger this mixture. This is where the measurement of the strength of alcoholic beverages in degrees comes from.

The history of thermodynamics began when Galileo Galilei created the first instrument for observing changes in temperature in 1592, calling it a thermoscope. The thermoscope was a small glass ball with a soldered glass tube. The ball was heated and the end of the tube was dipped into water. When the ball cooled, the pressure in it decreased, and the water in the tube, under the influence of atmospheric pressure, rose to a certain height. As the weather warmed, the water level in the tubes dropped. The disadvantage of the device was that it could only be used to judge relative degree heating or cooling the body, since it did not yet have a scale.

Later, Florentine scientists improved Galileo's thermoscope by adding a scale of beads and pumping out the air from the balloon.

Then thermometers filled with water appeared - but the liquid froze and the thermometers burst. Therefore, instead of water, they began to use wine alcohol, and then Galileo Evangelista’s student Torricelli came up with the idea of ​​filling a thermometer with mercury and alcohol and sealing it so that atmospheric pressure did not affect the readings. The device was turned upside down, 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. This 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 taking the melting point of ice and the boiling point of water as two extreme points.

Temperature scales

Humanity learned to measure temperature approximately 400 years ago. But the first instruments resembling today's thermometers appeared only in the 18th 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 used today, others gradually fell out of use.

Temperature scales are systems of temperature values ​​that can be compared with each other. Since temperature is not a quantity that can 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 recorded, corresponding to the transition temperatures of the selected thermometric substance into 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 origin. The interval between them is divided by a certain amount equal segments that are unit. The unit of temperature measurement is universally accepted as one degree. temperature scale device

The most popular and widely used temperature scales in the world are the Celsius and Fahrenheit scales.

Let's look at the available scales in order and try to compare them from the point of view of ease of use and practical usefulness. There are four most famous scales:

Fahrenheit

Reaumur scale

Celsius,

Kelvin scale

Fahrenheit

In many reference books, including Russian Wikipedia, Daniel Gabriel Fahrenheit is mentioned as a German physicist. However, according to the Encyclopedia Britannica, he was a Dutch physicist born in Poland in Gdansk on May 24, 1686. Fahrenheit himself made scientific instruments and in 1709 invented the alcohol thermometer, and in 1714 the mercury thermometer.

In 1724, Fahrenheit became a member of the Royal Society of London and presented it with his temperature scale. The scale was constructed based on three reference points. In the original version (which was later changed), he took the temperature of the brine solution (ice, water and ammonium chloride in a ratio of 1:1:1) as the zero point. The temperature of this solution stabilized at 0 °F (-17.78 °C). The second point of 32°F was the melting point of ice, i.e. temperature of a mixture of ice and water in a ratio of 1:1 (0 °C). The third point is normal temperature human body, to which he attributed 96 °F.

Why were such strange, non-round numbers chosen? According to one story, Fahrenheit initially chose the lowest temperature measured in his scale as the zero of his scale. hometown Gdansk in the winter of 1708/1709. Later, when it became necessary to make this temperature well reproducible, he used to reproduce it brine. One explanation for the inaccuracy of the temperature obtained is that Fahrenheit did not have the ability to make a good brine solution to obtain an accurate eutectic equilibrium composition of ammonium chloride (that is, he may have dissolved several salts, and not completely).

Another interesting story is connected with Fahrenheit’s letter to his friend Hermann Boerhaave. According to the letter, his scale was created based on the work of astronomer Olof Römer, with whom Fahrenheit had previously communicated. In the Roemer scale, saline solution freezes at zero degrees, water at 7.5 degrees, human body temperature is taken to be 22.5 degrees and water boils at 60 degrees (there is an opinion that this is analogous to 60 seconds in an hour). Fahrenheit multiplied each number by four to remove the fractional part. At the same time, the melting point of ice turned out to be 30 degrees, and the human temperature was 90 degrees. He went further and moved the scale so that the ice point was 32 degrees, and the human body temperature was 96 degrees. Thus, it became possible to break the interval between these two points, which amounted to 64 degrees, simply by repeatedly dividing the interval in half. (64 is 2 to the sixth power).

When I measured the boiling point of water with my calibrated thermometers, the Fahrenheit value was about 212 °F. Subsequently, the scientists decided to redefine the scale slightly, assigning an exact value to two well-reproducible reference points: the melting point of ice at 32 °F and the boiling point of water at 212 °F. At the same time, the normal human temperature on this scale after new, more accurate measurements turned out to be about 98 °F, and not 96 °F.

Reaumur scale

French naturalist René Antoine Ferchault de Reaumur was born on February 28, 1683 in La Rochelle into the family of a notary. He was educated at the Jesuit school in Poitiers. From 1699 he studied law and mathematics at the University of Bourget. In 1703 he continued his studies of mathematics and physics in Paris. After René published his first three works in mathematics in 1708, he was accepted as a member of the Paris Academy of Sciences.

Reaumur's scientific works are quite varied. He studied mathematics, chemical technology, botany, physics and zoology. But in the last two subjects he succeeded more, therefore, his main works were devoted to these topics.

In 1730, Reaumur described the alcohol thermometer he had invented, the scale of which was determined by the boiling and freezing points of water. 1 degree Réaumur is equal to 1/80 of the temperature interval between the melting point of ice (0 °R) and the boiling point of water (80 °R

Having soldered a thin tube to a round flask, Reaumur poured alcohol into it, purified as far as possible from water and dissolved gases. In his memoir, he notes that his liquid contained no more than 5 percent water.

The tube was not sealed - Reaumur only plugged it with turpentine-based putty.

In fact, Reaumur had only one reference point: the melting temperature of ice. And he determined the value of a degree not by dividing some temperature range by the number 80 that came from nowhere. In fact, he decided to take as one degree a change in temperature at which the volume of alcohol increases or decreases by 1/1000. Thus, Reaumur's thermometer can be considered essentially a large pycnometer, or more precisely, a primitive prototype of this physicochemical device.

Beginning in 1734, Reaumur published reports on measurements of air temperatures using the device he proposed for five years in various areas, from the central regions of France to the Indian port of Pondicherry, but later abandoned thermometry.

Nowadays, the Reaumur scale has fallen out of use.

Celsius

Anders Celsius (November 27, 1701 – April 25, 1744) was a Swedish astronomer, geologist and meteorologist (at that time geology and meteorology were considered part of astronomy). Professor of astronomy at Uppsala University (1730-1744).

Together with the French astronomer Pierre Louis Moreau, de Maupertuis participated in an expedition to measure a 1-degree segment of the meridian in Lapland (then part of Sweden). A similar expedition was organized to the equator, in what is now Ecuador. A comparison of the results confirmed Newton's assumption that the Earth is an ellipsoid, flattened at the poles.

1742 proposed the Celsius scale, in which the temperature of the triple point of water (this temperature practically coincides with the melting point of ice at normal pressure) was taken as 100, and the boiling point of water as 0. (Initially, Celsius took the melting temperature of ice as 100°, and the boiling temperature of water as 0°. And only in the year of Celsius’s death, his contemporary Carl Linnaeus “turned” this scale). Thus, the melting point of ice was taken as zero on the Celsius scale, and the boiling point of water at standard atmospheric pressure as 100°. This scale is linear in the range 0-100° and continues linearly in the region below 0° and above 100°.

The Celsius scale turned out to be more rational than the Fahrenheit scale and the Reaumur scale, and is now used everywhere.

Kelvin scale

Kelvin William (1824-1907) - an outstanding English physicist, one of the founders of thermodynamics and the molecular kinetic theory of gases.

Kelvin introduced the absolute temperature scale in 1848 and gave one of the formulations of the second law of thermodynamics in the form of the impossibility of completely converting heat into work. He calculated the size of molecules based on measuring the surface energy of the liquid.

The English scientist W. Kelvin introduced the absolute temperature scale. Zero temperature on the Kelvin scale corresponds to absolute zero, and the unit of temperature on this scale is equal to a degree on the Celsius scale, so absolute temperature T is related to temperature on the Celsius scale by the formula:

The SI unit of absolute temperature is called the kelvin (abbreviated K). Therefore, one degree on the Celsius scale is equal to one degree on the Kelvin scale: 1 °C = 1 K.

The temperature values ​​that the Fahrenheit and Celsius scales give us can be easily converted to each other. When converting “in your head” Fahrenheit values ​​into degrees Celsius, you need to reduce the original figure by 32 units and multiply by 5/9. Vice versa (from the Celsius to Fahrenheit scale) - multiply the original value by 9/5 and add 32. For comparison: the temperature of absolute zero in Celsius is 273.15 °, in Fahrenheit - 459.67 °.

Temperature measurement

Temperature measurement is based on the dependence of some physical quantity (for example, volume) on temperature. This dependence is used in the temperature scale of a thermometer - a device used to measure temperature.

Absolute zero temperatures

Any measurement requires the presence of a reference point. Temperature is no exception. For the Fahrenheit scale, this zero mark is the temperature of the snow mixed with table salt, for the Celsius scale – the freezing point of water. But there is a special temperature reference point - absolute zero.

For many years, researchers have been advancing towards absolute zero temperature. As is known, a temperature equal to absolute zero characterizes the ground state of a system of many particles - a state with the lowest possible energy, at which atoms and molecules perform so-called “zero” vibrations. Thus, deep cooling close to absolute zero (absolute zero itself is believed to be unattainable in practice) opens up unlimited possibilities for studying the properties of matter.

Absolute zero is theoretically the lowest possible temperature. Near this temperature, the energy of the substance becomes minimal. It is often also called “zero on the Kelvin scale.” Absolute zero is approximately -273°C or -460°F. All substances - gases, liquids, solids - are made up of molecules, and temperature determines the speed of movement of these molecules. The higher the temperature, the higher the speed of the molecules and the more volume they need to move (that is, substances expand). The lower the temperature, the slower they move, and as the temperature drops, the energy of the molecules eventually decreases so much that they stop moving altogether. In other words, any substance, when frozen, becomes solid. Although physicists have already achieved temperatures that differ from absolute zero by only a millionth of a degree, absolute zero itself is unattainable. The branch of science and technology that studies the unusual behavior of materials or substances near absolute zero is called cryogenic technology.

The pursuit of absolute zero essentially faces the same problems as . To reach the speed of light requires an infinite amount of energy, and reaching absolute zero requires the extraction of an infinite amount of heat. Both of these processes are impossible.

Despite the fact that we have not yet achieved the actual state of absolute zero, we are very close to it (although “very” in this case is a very loose concept; like a nursery rhyme: two, three, four, four and a half, four on a string, four by a hair's breadth, five). The coldest temperature ever recorded on Earth was recorded in Antarctica in 1983, at -89.15 degrees Celsius (184K).

Why do we need absolute zero temperatures?

Absolute zero temperature is a theoretical concept; it is impossible to achieve it in practice, even in scientific laboratories with the most sophisticated equipment. But scientists manage to cool the substance to very low temperatures, which are close to absolute zero.

At such temperatures substances acquire amazing properties, which they cannot have under normal circumstances. Mercury, which is called "living silver" because it is in a state close to liquid, becomes solid at this temperature - to the point that it can be used to drive nails. Some metals become brittle, like glass. Rubber becomes just as hard and brittle. If you hit a rubber object with a hammer at a temperature close to absolute zero, it will break like glass.

This change in properties is also associated with the nature of heat. The higher the temperature physical body, the more intense and chaotic the molecules move. As the temperature decreases, the movement becomes less intense and the structure becomes more orderly.

It's very important, especially from a scientific point of view, that materials behave crazy at extremely low temperatures.

So gas becomes liquid, and liquid solid body. The ultimate level of order is the crystal structure. At ultra-low temperatures, even substances that normally remain amorphous, such as rubber, acquire it.

Interesting phenomena also occur with metals. The atoms of the crystal lattice vibrate with less amplitude, electron scattering decreases, and therefore electrical resistance decreases. The metal acquires superconductivity, practical application which seems very tempting, although difficult to achieve.

At very low temperatures, many materials become superfluids, meaning they can have no viscosity at all, stack in ultra-thin layers, and even defy gravity to achieve a minimum of energy. Also, at low temperatures, many materials become superconducting, meaning there is no electrical resistance. Superconductors are able to respond to external magnetic fields in such a way as to completely cancel them inside the metal. As a result, you can combine cold temperature and a magnet and get something like levitation.

Why is there absolute zero, but not absolute maximum?

Let's look at the other extreme. If temperature is simply a measure of energy, then we can simply imagine atoms getting closer and closer to the speed of light. This can't go on forever, can it?

The short answer is: we don't know. It's possible that there literally is such a thing as infinite temperature, but if there is an absolute limit, the young universe provides some pretty interesting clues as to what it is. The highest temperature ever known (at least in our universe) probably occurred during what is known as Planck's time. It was a moment 10^-43 seconds after the Big Bang when gravity separated from quantum mechanics and physics became exactly what it is now. The temperature at that time was approximately 10^32 K. This is a septillion times hotter than the inside of our Sun.

Again, we're not at all sure if this is the hottest temperature it could be. Since we don't even have a large model of the universe at Planck's time, we're not even sure the universe boiled to such a state. In any case, we are many times closer to absolute zero than to absolute heat.

How life on Earth depends on temperature and climate conditions

Even in ancient times, our ancestors knew about the dependence of well-being and all life processes on weather and other natural phenomena. First written evidenceO influence of natural and climatic phenomena on healthhumans have been known since ancient times. In India 4000 years ago they talked about plants acquiring medicinal properties from the rays of the sun, thunderstorms and rain. Tibetan medicine still associates diseases with certain combinations of meteorological factors. The ancient Greek medical scientist Hippocrates (460-377 BC) in his “Aphorisms” wrote, in particular, that human bodies behave differently in relation to the time of year: some are located closer to summer, others - to winter, and diseases progress differently (good or bad) at different times of the year, in different countries and living conditions.

Basics scientific direction in medicine, the influence of climatic factors on human health originated in the 17th century. In Russia, the study of the influence of climate, seasons and weather on humans began with the foundation Russian Academy sciences in St. Petersburg (1725). In development theoretical foundations This science was played by outstanding domestic scientists I.M. Sechenov, I.P. Pavlov and others. At the beginning of the 21st century, it was proven that an outbreak of West Nile fever in the Volgograd and Astrakhan regions was associated with an abnormally warm winter. The heat of 2010 led to an unprecedented increase in this disease - 480 cases in the Volgograd, Rostov, Voronezh and Astrakhan regions. There is also a gradual advance of tick-borne encephalitis to the north, which has been proven by the work of Prof. N.K. Tokarevich (St. Petersburg Institute of Microbiology and Epidemiology named after Pasteur) in the Arkhangelsk region, and this phenomenon is also associated with climate change.

Climate has direct and indirect effects on humans

The direct influence is very diverse and is due to the direct effect of climatic factors on the human body and, above all, on the conditions of its heat exchange with the environment: on the blood supply to the skin, respiratory, cardiovascular and sweating systems.

The human body, as a rule, is influenced not by one isolated factor, but by their combination, and the main effect is not ordinary fluctuations in climatic conditions, but mainly their sudden changes. For any living organism, certain rhythms of vital activity of various frequencies have been established.

Some functions of the human body are characterized by changes in seasons. This applies to body temperature, metabolic rate, circulatory system, composition of blood cells and tissues. So, in the summer there is a redistribution of blood from the internal organs to the skin, therefore blood pressure lower in summer than in winter.

Climatic factors affecting humans

Most of the physical factors of the external environment, in interaction with which the human body has evolved, are of an electromagnetic nature. It is well known that the air near fast-flowing water is refreshing and invigorating: it contains many negative ions. For the same reason, people find the air clean and refreshing after a thunderstorm. On the contrary, the air in cramped rooms with an abundance of various types electromagnetic devices saturated with positive ions. Even a relatively short stay in such a room leads to lethargy, drowsiness, dizziness and headaches. A similar picture is observed in windy weather, on dusty and humid days. Experts in the field of environmental medicine believe that negative ions have a positive effect on human health, while positive ions have a negative effect.

Ultraviolet radiation

Among the climatic factors, a large biological significance has a short-wave part of the solar spectrum - ultraviolet radiation(UVR) (wavelength 295–400 nm).

Ultraviolet radiation is a prerequisite for normal human life. It destroys microorganisms on the skin, prevents rickets, normalizes mineral metabolism, and increases the body's resistance to infectious diseases and other diseases. Special observations have found that children who received enough ultraviolet radiation are ten times less susceptible to colds than children who did not receive enough ultraviolet radiation. With a lack of ultraviolet irradiation, the phosphorus-calcium metabolism, the body’s sensitivity to infectious diseases and colds increases, and functional disorders central nervous system, some chronic diseases worsen, general physiological activity decreases, and, consequently, human performance. Children are especially sensitive to “light starvation”, in whom it leads to the development of vitamin D deficiency (rickets).

Temperature

Thermal conditions are the most important condition for the existence of living organisms, since all physiological processes in them are possible under certain conditions.

Solar radiation turns into an exogenous heat source located outside the body in all cases when it falls on the body and is absorbed by it. Strength and nature of impact solar radiation depend on geographical location and are important factors determining the climate of the region. Climate determines the presence and abundance of plant and animal species in a given area. The range of temperatures existing in the Universe is equal to thousands of degrees.

In comparison, the limits within which life can exist are very narrow - about 300°C, from -200°C to +100°C. In fact, most species and most activity are confined to a narrower range of temperatures. As a rule, these temperatures at which the normal structure and functioning of proteins are possible: from 0 to +50°C.

Temperature is one of the important abiotic factors affecting everything physiological functions all living organisms. The temperature on the earth's surface depends on the geographic latitude and altitude above sea level, as well as the time of year. For a person in light clothing, the comfortable air temperature will be + 19...20°C, without clothes - + 28...31°C.

When temperature parameters change, the human body develops specific reactions to adapt to each factor, that is, it adapts.

The temperature factor is characterized by pronounced seasonal and daily fluctuations. In a number of regions of the Earth, this effect of the factor has an important signaling value in regulating the timing of the activity of organisms, ensuring their daily and seasonal modes of life.

When characterizing the temperature factor, it is very important to take into account its extreme indicators, the duration of their action, and repeatability. Temperature changes in habitats that go beyond the tolerance of organisms lead to their mass death. The importance of temperature lies in the fact that it changes the rate of physicochemical processes in cells, which affect the entire life activity of organisms.

How does adaptation to temperature changes occur?

The main cold and heat receptors of the skin provide thermoregulation of the body. Under different temperature influences, signals to the central nervous system do not come from individual receptors, but from entire areas of the skin, the so-called receptor fields, the sizes of which are not constant and depend on body temperature and the environment.

Body temperature, to a greater or lesser extent, affects the entire body (all organs and systems). The relationship between the temperature of the external environment and body temperature determines the nature of the activity of the thermoregulation system.

The ambient temperature is advantageously lower than body temperature. As a result, heat is constantly exchanged between the environment and the human body due to its release from the surface of the body and through the respiratory tract into the surrounding space. This process is commonly called heat transfer. The formation of heat in the human body as a result of oxidative processes is called heat generation. At rest and with normal health, the amount of heat generation is equal to the amount of heat transfer. In hot or cold climates, when physical activity body, diseases, stress, etc. The level of heat generation and heat transfer may vary.

How does adaptation to low temperatures occur?

The conditions under which the human body adapts to cold can be different (for example, working in unheated rooms, refrigeration units, outdoors in winter). Moreover, the effect of cold is not constant, but alternating with what is normal for the human body temperature conditions. Adaptation in such conditions is not clearly expressed. In the first days, in response to low temperatures, heat generation increases uneconomically; heat transfer is not yet sufficiently limited. After adaptation, heat generation processes become more intense, and heat transfer decreases.

Otherwise, adaptation to living conditions in northern latitudes occurs, where a person is affected not only by low temperatures, but also by the lighting regime and level of solar radiation characteristic of these latitudes.

What happens in the human body during cooling.

Due to irritation of cold receptors, reflex reactions that regulate heat conservation change: they narrow blood vessels skin, which reduces the body’s heat transfer by a third. It is important that the processes of heat generation and heat transfer are balanced. The predominance of heat transfer over heat generation leads to a decrease in body temperature and disruption of body functions. At a body temperature of 35°C, mental disturbances are observed. A further decrease in temperature slows down blood circulation and metabolism, and at temperatures below 25°C breathing stops.

One of the factors of intensification energy processes is lipid metabolism. For example, polar explorers, whose metabolism slows down in low air temperatures, take into account the need to compensate for energy costs. Their diets are high energy value(calorie content). Residents of northern regions have a more intense metabolism. The bulk of their diet consists of proteins and fats. Therefore, the content of fatty acids in their blood is increased, and the sugar level is slightly decreased.

People adapting to the humid, cold climate and oxygen deficiency of the North also have increased gas exchange, high content serum cholesterol and mineralization of skeletal bones, a thicker layer of subcutaneous fat (functioning as a heat insulator).

However, not all people in to the same degree capable of adaptation. In particular, for some people in the North, protective mechanisms and adaptive restructuring of the body can cause maladaptation - a whole series pathological changes called “polar disease”. One of the most important factors, ensuring human adaptation to the conditions of the Far North, is the body’s need for ascorbic acid (vitamin C), which increases the body’s resistance to various types of infections.

Adaptation to impact high temperature.

Tropical conditions can have an impact harmful influence on the human body. Negative effects may be the result of harsh environmental factors such as ultraviolet radiation, extreme heat, sudden temperature changes and tropical storms. In weather-sensitive people, exposure to tropical environmental conditions increases the risk of acute illnesses, including coronary disease heart disease, asthma attacks and kidney stones. Negative effects may be exacerbated by sudden changes in climate, such as when traveling by air.

High temperature can affect the human body in artificial and natural conditions. In the first case, we mean working in rooms with high temperatures, alternating with staying in conditions of a comfortable temperature.

The high temperature of the environment excites thermal receptors, the impulses of which include reflex reactions aimed at increasing heat transfer. At the same time, the blood vessels of the skin expand, the movement of blood through the vessels accelerates, and the thermal conductivity of peripheral tissues increases 5-6 times. If this is not enough to maintain thermal equilibrium, the skin temperature rises and reflex sweating begins - the most effective way heat transfer ( greatest number sweat glands on the skin of the hands, face, armpits). The indigenous people of the South have a lower average body weight than the inhabitants of the North, subcutaneous fat not very developed. Morphological and physiological characteristics are especially pronounced in populations living in conditions of high temperature and lack of moisture (in deserts and semi-deserts, areas adjacent to them). For example, the natives of Central Africa, South India and other regions with hot, dry climates have long, thin limbs and low body weight.

Intense sweating during a person's stay in a hot climate leads to a decrease in the amount of water in the body. To compensate for the loss of water, you need to increase your consumption. The local population is more adapted to these conditions than people who came from the temperate zone. Aboriginals have two to three times less daily requirement in water, as well as in proteins and fats, as they have a high energy potential and increase thirst. Since as a result of intense sweating in the blood plasma the content of ascorbic acid and other water-soluble vitamins, the diets of the local population are dominated by carbohydrates, which increase the body’s endurance, and vitamins, which make it possible to perform heavy work. physical work for a long time.

What factors determine the perception of temperature?

Wind enhances the temperature sensation most sensitively. With strong winds, cold days seem even colder, and hot days seem even hotter. Humidity also affects the body's perception of temperature. With high humidity, the air temperature seems lower than in reality, and with low humidity, the opposite is true.

The perception of temperature is individual. Some people like cold, frosty winters, while others like warm and dry winters. This depends on the physiological and psychological characteristics of a person, as well as the emotional perception of the climate in which he spent his childhood.

Natural and climatic conditions and health

Human health largely depends on weather conditions. For example, in winter people get colds more often, pulmonary diseases, flu, sore throat.

Diseases associated with weather conditions primarily include overheating and hypothermia. Overheating and heat strokes occur in summer in hot, windless weather. Flu, colds, catarrhs respiratory tract, as a rule, occur in the autumn-winter period of the year. Some physical factors (atmospheric pressure, humidity, air movements, oxygen concentration, degree of disturbance magnetic field land, the level of air pollution) have not only direct impact on the human body. Separately or in combination, they can aggravate the course of existing diseases and prepare certain conditions for the proliferation of pathogens infectious diseases. So, in cold period Every year, due to extreme weather variability, cardiovascular diseases worsen - hypertension, angina pectoris, myocardial infarction. Intestinal infections ( typhoid fever, dysentery) affect people in the hot season. In children under one year old, the largest number of pneumonias is recorded in January - April.

In people with disorders of nervous function autonomic system or chronic diseases, adaptation to changing weather factors is difficult. Some patients are so sensitive to weather changes that they can serve as a kind of biological barometers, accurately predicting the weather several times in advance. Research conducted by the Siberian Branch of the Academy of Medical Sciences of the Russian Federation showed that 60–65% of those suffering from cardiovascular diseases are sensitive to fluctuations in weather factors, especially in spring and autumn, with significant fluctuations in atmospheric pressure, air temperature and changes in the Earth’s geomagnetic field. When air fronts invade, causing contrasting changes in weather, crises are more often observed during hypertension, the condition of patients with cerebral atherosclerosis is worsening, and cardiovascular accidents are increasing.

In the era of urbanization and industrialization, people spend most of their lives indoors. How longer body isolated from external climatic factors and is in comfortable or subcomfortable microclimate conditions of the room, the more its adaptive reactions to constantly changing weather parameters are reduced, including the weakening of thermoregulation processes. As a result, the dynamic balance between the human body and the external environment is disrupted, complications arise in people with cardiovascular pathology- crises, myocardial infarction, cerebral strokes. Therefore, it is necessary to organize a modern medical weather forecast as a method of preventing cardiovascular accidents.

Almost every person, having reached a certain age, experienced another stress or recovered from an illness, suddenly begins to feel the dependence of his condition and mood on changing environmental factors. In this case, the conclusion is usually drawn that the weather affects health. At the same time, other people, who have remarkable health and great confidence in their strengths and capabilities, cannot imagine how such insignificant factors from their point of view as atmospheric pressure, geomagnetic disturbances, and gravitational anomalies in the solar system can affect a person. Moreover, the group of opponents of the influence of geophysical factors on humans often includes physicists and geophysicists.

The main arguments of skeptics are rather controversial physical calculations of the energetic significance of the Earth's electromagnetic field, as well as changes in its gravitational field under the influence of the gravitational forces of the Sun and planets solar system. It is said that in cities industrial electromagnetic fields are many times more powerful, and the value of the change in the gravitational field, which is a figure with eight zeros after the decimal point, does not have any physical meaning. Geophysicists, for example, have such an alternative point of view on the influence of solar, geophysical and weather factors on human health.

Climate change as a threat to global health

The Intergovernmental Panel on Climate Change report confirmed the existence large quantity evidence on the impact of global climate on human health. Climate variability and change lead to death and illness from natural disasters such as heat waves, floods and droughts. In addition, many serious illnesses extremely sensitive to changes in temperature and precipitation patterns. These diseases include vector-borne diseases such as malaria and dengue, as well as malnutrition and diarrhea, which are other leading causes of death. Climate change is also contributing to the rising global burden of disease, a trend that is expected to worsen in the future.

The impact of climate change on human health is not uniform across the world. Populations in developing countries, especially small island states, arid and high-altitude areas, and densely populated coastal areas are considered to be particularly vulnerable.

Fortunately, many of these health hazards can be avoided through existing health programs and interventions. Concerted action to strengthen the core elements of health systems and promote healthy development pathways can improve population health now while also reducing vulnerability to climate change in the future.

Conclusions

Being an integral component of the Earth's biosphere, man is a particle of the surrounding world, deeply dependent on the course of external processes. And therefore, only the harmony of the internal processes of the body with the rhythms of the external environment, nature, and space can be a solid basis for the stable functioning of the human body, that is, the basis for its health and well-being.

Today it has become clear that it is natural processes that give our body the ability to withstand numerous extreme factors. A social activities a person becomes the same powerful stressing element if its rhythms do not obey biosphere and cosmic fluctuations, and, especially when a massive long-term attempt is made to subordinate a person’s vital activity, his biological clock, artificial social rhythms.

Changes in climate and weather conditions do not have the same effect on the well-being of different people. In a healthy person, when there is a change in climate or weather, the physiological processes in the body are timely adjusted to the changed environmental conditions. As a result, it intensifies defensive reaction, And healthy people practically do not feel the negative influence of the weather. In a sick person, adaptive reactions are weakened, so the body loses the ability to quickly adapt. The influence of natural and climatic conditions on human well-being is also associated with age and individual susceptibility of the body.