Who measured atmospheric pressure for the first time. Measurement of atmospheric pressure. Torricelli's Experience - Knowledge Hypermarket. Atmospheric pressure changes with altitude

Atmospheric pressure is one of the most important climatic characteristics influencing the person. It promotes the formation of cyclones and anticyclones, provokes the development of cardiovascular diseases in humans. Evidence that air has weight was obtained in the 17th century, since then the process of studying its fluctuations has been one of the central for forecasters.

What is atmosphere

The word "atmosphere" is of Greek origin, literally translated as "steam" and "ball". This is a shell of gas 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 in 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 necessary for a person oxygen, weather indicators depend on it. The boundaries of the atmosphere are very conditional. 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, which are adhered to by NASA, this gas envelope ends at an altitude of about 100 kilometers.

It arose as a result of volcanic eruptions and the evaporation of substances in space 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 idea 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. This is where the story of discovery begins atmospheric pressure.

This phenomenon was studied by Galileo's student, the Italian physicist and mathematician Evangelista Torricelli. With the help of experiments on a heavier element, mercury, several 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 matter 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 rose in the gardens of Florence. It was he who discovered for humanity what atmospheric pressure is and how it affects human life. the tube was named after him "Torricellian void".

Why and as a result of what atmospheric pressure is created

One of the key tools in meteorology is the study of the movement and movement of air masses. This allows you to get an idea of ​​what creates atmospheric pressure. After it was proved that air has weight, it became clear that it, like any other body on the planet, is subject to gravity. This is what causes the occurrence of 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 a 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 the air heats up, it becomes lighter and rises up, while the cooled air masses descend, creating a constant, continuous movement. Each of these flows has a different atmospheric pressure, which provokes the appearance of winds on the surface of our planet.

Influence on the weather

Atmospheric pressure is one of the key terms in meteorology. Weather on Earth is formed due to the impact of cyclones and anticyclones, which are formed under the influence of pressure drops in the gas envelope of the planet. Anticyclones are characterized by high rates (up to 800 mm Hg and above) and low speed of movement, 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 rapidly falls, reaching 560 mm of mercury.

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

Standard indicators

Average in ideal conditions the level of 760 mm Hg is considered. The pressure level changes with altitude: in lowlands or areas located 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 every kilometer.

Reduced atmospheric pressure

It decreases with increasing altitude due to distance from the Earth's surface. In the first case, this process is explained by a decrease in the effect 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 along the sides, and the pressure evens out.

The tropics are considered traditional territories with lower atmospheric pressure. Low pressure is always observed in equatorial territories. However, zones with a high and low index are distributed unevenly 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 due to the fact that the air above a cold surface becomes cold and dense, its mass increases, therefore, it is more strongly attracted to the surface by gravity. He sinks, and the space above him fills with warmer air masses, as a result of which atmospheric pressure is created with an increased level.

Influence on a person

Normal indicators typical for the area of ​​residence of a person should not have any effect on his well-being. At the same time, atmospheric pressure and life on Earth are inextricably linked. Its change - an 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, attacks of unreasonable headache, and decreased efficiency.

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

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

The atmosphere surrounding the globe exerts pressure on the surface of the earth and on all objects above the earth. In a quiescent 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 cm 2.

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 pressure of mercury in the tube is created only by the weight of the column of mercury in the tube. Thus, the atmospheric pressure is equal to the pressure of the column of mercury in the tube and the height of this column depends on the atmospheric pressure of the surrounding air: the higher the atmospheric pressure, the higher the column of mercury 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 mm Hg (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 that produces a vertical column of mercury with a height of 780 mm.

Observing day after day the height of the mercury column in the tube, Torricelli found that this height changes, and changes in atmospheric pressure are somehow related to changes in weather. Having attached 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 ("liquid-free"), which does not use mercury, and the pressure is measured using a metal spring. In practice, before taking readings, lightly tap the glass of the instrument with your finger to overcome friction in the linkage.

Based on the Torricelli tube, station cup barometer, which is the main instrument for measuring atmospheric pressure on meteorological stations currently. It consists of a barometric tube with a diameter of about 8 mm and a length of about 80 cm, 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 to observe the meniscus of the mercury column.

At the same atmospheric pressure, the height of the mercury column depends on the temperature and the acceleration of gravity, which varies somewhat depending on the latitude and altitude above sea level. To exclude 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 gravity at sea level at a latitude of 45 ° and, by introducing an instrumental correction, the pressure at the station is obtained.

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

1 mb = 1 hPa; 1 mm Hg = 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, maps of isobars at sea level are built. To do this, atmospheric pressure is plotted on a geographical map, measured at meteorological stations and reduced to sea level. 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 at the center are called baric minima or cyclones.

The atmospheric pressure at every point on the earth's surface does not remain constant. Sometimes the pressure changes very quickly over time, sometimes it remains almost unchanged for a long time. V daily course pressure, two highs and two lows are found. The maximums are noted at about 10 and 22 hours local time, the minimums are around 4 and 16 hours. The annual pressure variation strongly depends on the physical and geographical conditions. This move is more noticeable over the continents than over the oceans.

This pressure is called atmospheric pressure. How big is it?

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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 pushes against the earth's surface is called atmospheric pressure. A column of air from the Earth's surface 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 pressure of mercury in the tube is created only by the weight of the column of mercury in the tube. Thus, the atmospheric pressure is equal to the pressure of the column of mercury in the tube and the height of this column depends on the atmospheric pressure of the surrounding air: the higher the atmospheric pressure, the higher the column of mercury 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 (from the Greek grapho - I write) are used.

If we attach a scale to a tube, like the one that Torricelli used in his experiment, 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 rarefaction is created inside the boxes (the pressure in them is less than atmospheric) 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 transferred to the arrow, which moves along the scale (the scale marks the divisions and the value of atmospheric pressure). When the atmospheric pressure rises, the box shrinks, when it decreases, it expands, these vibrations act on the spring, which is connected to the arrow. The arrow shows 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 changes in weather 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 the movement of a paper tape, on which a grid of pressure values ​​and days of the week is applied. From such tapes, you can determine how the atmospheric pressure has changed during any week. Atmospheric pressure is measured in millimeters of mercury (mmHg).

4. Why is the atmospheric pressure different in different places?

On the earth's surface, atmospheric pressure varies from place to place and over time. Particularly important are the weather-defining 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 reduced 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?

With altitude, atmospheric pressure drops. This is due to two reasons. First, the higher we are, the lower the height of the column of air 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 a lower mass and weight.

If we imagine a column of air from the Earth's surface 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 a parallel of 45 ° at a temperature of 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 (mmHg).

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

For weather analysis, 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, which are called isotherms (lines of the same temperature) and isobars (lines of equal pressure). This method allows you to find out the position of areas of high and low pressure, areas of high and low temperature.

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

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

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

In fig. 2 sign the height of the column of mercury in the tube if the atmospheric pressure is known to be 760 mm Hg. Art.

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

In the morning hours, the surface of land and sea practically does not heat up sunbeams.

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

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

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

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

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

2. The pressure of the atmosphere changes with height

Under the same air heating conditions, 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 constantly live. 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 population of one million, 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. Actual capital, political, economic and Cultural Center countries - the city of La Paz. Here are the executive and legislative branches of Bolivia, the parliament building, the residence of the president and the ministry. The city was founded in 1548 by the Spanish conquistador Alonso Mendoza and named in honor of the reconciliation of the Spanish conquerors, who have 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.

Write the missing words in the definition.

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

Lines connecting points with the same values ​​of atmospheric pressure are called isobars.

Pathfinder School

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