As a result, atmospheric pressure is created. The history of the discovery of atmospheric pressure. Atmospheric pressure Why and as a result of which atmospheric pressure is created

The atmosphere surrounding the globe exerts pressure on the surface of the earth and on all objects above the earth. In a resting atmosphere, the pressure at any point is equal to the weight of the overlying column of air extending to the outer periphery of the atmosphere and having a cross section of 1 cm2.

Atmospheric pressure was first measured by an Italian scientist Evangelista Torricelli in 1644. The device is a U-shaped tube about 1 m long, sealed at one end and filled with mercury. Since there is no air in the upper part of the tube, the mercury pressure in the tube is created only by the weight of the mercury column in the tube. Thus, the atmospheric pressure is equal to the pressure of the mercury column in the tube and the height of this column depends on the atmospheric pressure of the surrounding air: the greater the atmospheric pressure, the higher the mercury column in the tube and, therefore, the height of this column can be used to measure atmospheric pressure.

Normal atmospheric pressure (at sea level) is 760 mmHg (mm Hg) at 0°C. If the pressure of the atmosphere, for example, 780 mm Hg. Art., this means that the air produces the same pressure as a vertical column of mercury with a height of 780 mm.

Watching day after day the height of the mercury column in the tube, Torricelli discovered that this height changes, and changes in atmospheric pressure are somehow connected with changes in the weather. Attaching a vertical scale next to the tube, Torricelli received a simple device for measuring atmospheric pressure - a barometer. Later they began to measure pressure using an aneroid barometer ("liquidless"), which does not use mercury, and the pressure is measured using a metal spring. In practice, before taking readings, it is necessary to lightly tap the glass of the instrument with a finger to overcome friction in the leverage.

Made on the basis of the Torricelli tube station cup barometer, which is the main instrument for measuring atmospheric pressure at meteorological stations at present. It consists of a barometric tube about 8 mm in diameter and about 80 cm long, lowered with its free end into a barometric cup. The entire barometric tube is enclosed in a brass frame, in the upper part of which a vertical cut is made for observing the meniscus of the mercury column.

At the same atmospheric pressure, the height of the mercury column depends on temperature and the acceleration of free fall, which varies somewhat depending on latitude and height above sea level. To eliminate the dependence of the height of the mercury column in the barometer on these parameters, the measured height is brought to a temperature of 0°C and the acceleration of free fall at sea level at a latitude of 45°, and, by introducing an instrumental correction, the station pressure is obtained.

In accordance with the international system of units (SI system), the main unit for measuring atmospheric pressure is the hectopascal (hPa), however, in the service of a number of organizations it is allowed to use the old units: millibar (mb) and millimeter of mercury (mm Hg).

1 mb = 1 hPa; 1 mmHg = 1.333224 hPa

The spatial distribution of atmospheric pressure is called baric field. The baric field can be visualized using surfaces, at all points of which the pressure is the same. Such surfaces are called isobaric. To obtain a visual representation of the distribution of pressure on the earth's surface, isobar maps are built at sea level. To do this, atmospheric pressure measured at meteorological stations and reduced to sea level is applied to a geographical map. Then points with the same pressure are connected by smooth curved lines. Areas of closed isobars with increased pressure in the center are called baric maxima or anticyclones, and areas of closed isobars with reduced pressure in the center are called baric minima or cyclones.

Atmospheric pressure at every point on the earth's surface does not remain constant. Sometimes the pressure changes in time very quickly, sometimes it remains almost unchanged for quite a long time. In the diurnal course of pressure, two maxima and two minima are found. The maximums are observed at about 10:00 and 22:00 local time, the minimums are at about 4:00 and 16:00. The annual course of pressure strongly depends on physical and geographical conditions. Over the continents, this move is more noticeable than over the oceans.

We will answer the following questions.

1. What is called atmospheric pressure?

Air has weight and presses on the earth's surface and objects on it. The force with which air presses on the earth's surface is called atmospheric pressure. A column of air from the surface of the Earth to the upper boundary of the atmosphere presses on the earth's surface with a force equal to approximately 1.033 kg/cm2. In technology, this value is taken as a unit of pressure and is called 1 atmosphere.

2. Who and how first measured atmospheric pressure?

Atmospheric pressure was first measured by the Italian scientist Evangelista Torricelli in 1644. The device is a U-shaped tube about 1 m long, sealed at one end and filled with mercury. Since there is no air in the upper part of the tube, the mercury pressure in the tube is created only by the weight of the mercury column in the tube. Thus, the atmospheric pressure is equal to the pressure of the mercury column in the tube and the height of this column depends on the atmospheric pressure of the surrounding air: the greater the atmospheric pressure, the higher the mercury column in the tube and, therefore, the height of this column can be used to measure atmospheric pressure.

3. What instruments are used to measure atmospheric pressure?

To measure atmospheric pressure, a mercury barometer, an aneroid barometer and a barograph are used (from Greek grapho - I write).

If a scale is attached to a tube, similar to the one used by Torricelli in his experiment, then we get the simplest instrument for measuring atmospheric pressure - a mercury barometer.

The main part of the aneroid barometer are round corrugated metal boxes, which are interconnected; a vacuum is created inside the boxes (the pressure in them is less than atmospheric pressure), with an increase in atmospheric pressure, the boxes are compressed and pull the spring attached to them; the movement of the end of the spring through special devices will be transmitted to the arrow, which moves along the scale (divisions and the value of atmospheric pressure are marked on the scale). When atmospheric pressure rises, the box contracts, and when it decreases, it expands, these vibrations act on the spring, which is connected to the arrow. The arrow indicates the pressure value on the dial.

The aneroid barometer is one of the main instruments that meteorologists use to predict the weather for the coming days, since weather changes are associated with changes in atmospheric pressure.

A barograph is used to automatically and continuously record changes in atmospheric pressure. In addition to metal corrugated boxes, this device has a mechanism for moving a paper tape, on which a grid of pressure values ​​\u200b\u200band days of the week is applied. From such tapes, you can determine how atmospheric pressure changed during any week. Atmospheric pressure is measured in millimeters of mercury (mm Hg).

4. Why is atmospheric pressure different in different places?

On the earth's surface, atmospheric pressure varies from place to place and over time. Especially important are the weather-determining non-periodic changes in atmospheric pressure associated with the emergence, development and destruction of slowly moving areas of high pressure (anticyclones) and relatively fast moving huge eddies (cyclones), in which low pressure prevails. The colder the air, the higher its density. The density of the air above it depends on the heating of the underlying surface. If the air is dense, then its mass is greater, and therefore it presses harder on the surface.

5. How will atmospheric pressure change with altitude?

Atmospheric pressure decreases with height. This is due to two reasons. Firstly, the higher we are, the lower the height of the air column above us, and, therefore, less weight presses on us. Secondly, with height, the density of air decreases, it becomes more rarefied, that is, it contains fewer gas molecules, therefore it has less mass and weight.

If we imagine a column of air from the surface of the Earth to the upper layers of the atmosphere, then the weight of such an air column will be equal to the weight of a column of mercury 760 mm high. This pressure is called normal atmospheric pressure. This is the air pressure at the 45° parallel at 0°C at sea level. If the height of the column is more than 760 mm, then the pressure is increased, less - reduced. Atmospheric pressure is measured in millimeters of mercury (mm Hg).

6. In what ways do maps show the distribution of air temperature and atmospheric pressure near the earth's surface?

To analyze the weather, experts use maps on which the values ​​of meteorological quantities are plotted. When processing meteorological maps, meteorologists connect points with the same values ​​of air temperature and atmospheric pressure with lines called isotherms (lines of the same temperature) and isobars (lines of the same pressure). This method allows you to find out the position of areas of high and low pressure, areas of high and low temperatures.

1. What is atmospheric pressure. How atmospheric pressure was measured in the distant past.

Atmospheric pressure is the force with which a column of atmospheric air presses on the earth's surface.

On fig. 1 use arrows to show the direction and average pressure of the mercury column in the tube and the atmospheric air column on the surface of the mercury in the cup. (The cross-sectional area of ​​a tube containing mercury is 1 cm2.)

On fig. 2 sign the height of the mercury column in the tube, if it is known that the atmospheric pressure is 760 mm Hg. Art.

Fill in the missing words in the description of the change in atmospheric pressure over the sea and over land during the day.

In the morning, the surface of land and sea is practically not heated by the sun's rays.

During the night, the temperature of the near-ground and surface air layers almost cooled down, so there are no noticeable differences between the atmospheric pressure over land (Pc) and over the sea (Pm).

During the day, the surface of the land is intensely heated by the sun's rays and the earth's surface gives off heat to the surface layer of air, which becomes less dense.

Thus, over land, atmospheric pressure is higher. The surface of the water during the day is also heated by the sun's rays, but the heat is transferred to the deeper layers and "accumulates" in the water column. Consequently, the driving layer of air is less dense than the ground layer, it heats up, it is later. Relatively low atmospheric pressure is formed over the sea.

In the evening, as in the morning, the air temperature and atmospheric pressure over land and over the sea are almost the same.

At night, the earth's surface (land and sea) is not heated by the sun's rays.

The surface of the land cools than the surface of the sea, gives off its heat to the surface layer of air, its temperature decreases faster than the temperature of the surface layer of air. Consequently, the air over land is less dense than over the sea, and over land it is less dense than over the sea.

2. Atmospheric pressure changes with height

Under the same conditions of air heating, atmospheric pressure decreases with height.

Using the text of the textbook, determine the values ​​of atmospheric pressure in two settlements of the Earth.

The Tibetan Buddhist monastery Rongbuk (founded in 1902) is the highest place on Earth where people live permanently. The legendary monastery is located on the northern side of the Himalayas, at the foot of Everest at an altitude of 5029 m. Climbers pass through Rongbuk to the base camp, from where the conquest of the highest peak in the world, Mount Everest, begins. Monks come to the camp to pray for the daredevils and perform rituals.

If at the level of the World Ocean the atmospheric pressure is 760 mm Hg, then at the level of the Rongbuk Monastery it is 292 mm Hg.

In Bolivia (South America) at an altitude of 3660 m in the Andes is the city of La Paz with a million inhabitants, which is called the highest mountain capital in the world. The official capital of Bolivia is the small town of Sucre, where only the country's supreme court is located. The actual capital, political, economic and cultural center of the country is the city of La Paz. Here are the executive and legislative authorities of Bolivia, the parliament building, the residence of the president and ministries. The city was founded in 1548 by the Spanish conquistador Alonso Mendoza and named after the reconciliation of the Spanish conquerors who had long been at war with each other.

If at the level of the World Ocean the atmospheric pressure is 760 mm Hg. Art., then at the level of the city of La Paz 418 mm Hg. Art.

Fill in the missing words in the definition.

Lines connecting points with the same air temperature are called isotherms.

Lines connecting points of equal atmospheric pressure are called isobars.

Pathfinder School

Determine the atmospheric pressure in the geography classroom, on the first and last floors of the school building. (individually)

This pressure is called atmospheric. How big is it?

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Atmospheric pressure is one of the most important climatic characteristics that affect a person. It contributes to the formation of cyclones and anticyclones, provokes the development of cardiovascular diseases in people. Evidence that air has weight was obtained as early as the 17th century, since then the process of studying its vibrations has been one of the central ones for weather forecasters.

What is atmosphere

The word "atmosphere" is of Greek origin, literally it translates as "steam" and "ball". This is a gaseous shell around the planet, which rotates with it and forms a single whole cosmic body. It extends from the earth's crust, penetrating into the hydrosphere, and ends with the exosphere, gradually flowing into interplanetary space.

The atmosphere of the planet is its most important element, providing the possibility of life on Earth. It contains the oxygen necessary for a person, weather indicators depend on it. The boundaries of the atmosphere are very arbitrary. It is generally accepted that they begin at a distance of about 1000 kilometers from the earth's surface and then, at a distance of another 300 kilometers, smoothly pass into interplanetary space. According to the theories that NASA adheres to, this gaseous envelope ends at an altitude of about 100 kilometers.

It arose as a result of volcanic eruptions and the evaporation of substances in cosmic bodies that fell on the planet. Today it consists of nitrogen, oxygen, argon and other gases.

History of the discovery of atmospheric pressure

Until the 17th century, mankind did not think about whether air has mass. There was also no concept of what atmospheric pressure was. However, when the Duke of Tuscany decided to equip the famous Florentine gardens with fountains, his project failed miserably. The height of the water column did not exceed 10 meters, which contradicted all ideas about the laws of nature at that time. It is here that the story of the discovery of atmospheric pressure begins.

Galileo's student, the Italian physicist and mathematician Evangelista Torricelli, took up the study of this phenomenon. With the help of experiments on a heavier element, mercury, a few years later he was able to prove the presence of weight in air. He first created a vacuum in a laboratory and developed the first barometer. Torricelli imagined a glass tube filled with mercury, in which, under the influence of pressure, such an amount of substance remained that would equalize the pressure of the atmosphere. For mercury, the column height was 760 mm. For water - 10.3 meters, this is exactly the height to which the fountains in the gardens of Florence rose. It was he who discovered for mankind what atmospheric pressure is and how it affects human life. in the tube was named "Torricellian void" after him.

Why and as a result of which atmospheric pressure is created

One of the key tools of meteorology is the study of the movement and movement of air masses. Thanks to this, you can get an idea of ​​\u200b\u200bthe result of which atmospheric pressure is created. After it was proved that air has weight, it became clear that it, like any other body on the planet, is affected by the force of attraction. This is what causes pressure when the atmosphere is under the influence of gravity. Atmospheric pressure can fluctuate due to differences in air mass in different areas.

Where there is more air, it is higher. In rarefied space, a decrease in atmospheric pressure is observed. The reason for the change lies in its temperature. It is heated not from the rays of the Sun, but from the surface of the Earth. As it heats up, the air becomes lighter and rises, while the cooled air masses sink down, creating a constant, continuous movement. Each of these streams has a different atmospheric pressure, which provokes the appearance of winds on the surface of our planet.

Impact on the weather

Atmospheric pressure is one of the key terms in meteorology. The weather on Earth is formed due to the influence of cyclones and anticyclones, which are formed under the influence of pressure drops in the gaseous shell of the planet. Anticyclones are characterized by high rates (up to 800 mmHg and above) and low speed, while cyclones are areas with lower rates and high speed. Tornadoes, hurricanes, tornadoes are also formed due to sudden changes in atmospheric pressure - inside the tornado, it drops rapidly, reaching 560 mm of mercury.

The movement of air leads to a change in weather conditions. Winds that arise between areas with different pressure levels overtake cyclones and anticyclones, as a result of which atmospheric pressure is created, which forms certain weather conditions. These movements are rarely systematic and very difficult to predict. In areas where high and low atmospheric pressure collide, climatic conditions change.

Standard indicators

The average under ideal conditions is considered to be 760 mmHg. The pressure level changes with altitude: in lowlands or areas below sea level, the pressure will be higher, at an altitude where the air is rarefied, on the contrary, its indicators decrease by 1 mm of mercury with each kilometer.

Reduced atmospheric pressure

It decreases with increasing altitude due to the distance from the Earth's surface. In the first case, this process is explained by a decrease in the impact of gravitational forces.

Heating up from the Earth, the gases that make up the air expand, their mass becomes lighter, and they rise to higher ones. The movement occurs until the neighboring air masses are less dense, then the air spreads to the sides, and the pressure equalizes.

The tropics are considered traditional areas with lower atmospheric pressure. In the equatorial territories, low pressure is always observed. However, zones with an increased and decreased index are unevenly distributed over the Earth: in the same geographical latitude, there may be areas with different levels.

Increased atmospheric pressure

The highest level on Earth is observed at the South and North Poles. This is because the air above the cold surface becomes cold and dense, its mass increases, therefore, it is more strongly attracted to the surface by gravity. It descends, and the space above it is filled with warmer air masses, as a result of which atmospheric pressure is created with an increased level.

Impact on a person

Normal indicators, characteristic of the area where a person lives, should not have any effect on his well-being. At the same time, atmospheric pressure and life on Earth are inextricably linked. Its change - increase or decrease - can provoke the development of cardiovascular diseases in people with high blood pressure. A person may experience pain in the region of the heart, bouts of unreasonable headache, and reduced performance.

For people suffering from respiratory diseases, anticyclones that bring high blood pressure can become dangerous. The air descends and becomes denser, the concentration of harmful substances increases.

During fluctuations in atmospheric pressure, people's immunity decreases, the level of leukocytes in the blood, so it is not recommended to load the body physically or intellectually on such days.