Who was the first scientist to measure atmospheric pressure? As a result, atmospheric pressure is created. History of the discovery of atmospheric pressure. Other ways to measure atmospheric pressure

Atmosphere surrounding Earth, exerts pressure on the surface of the earth and on all objects located above the ground. 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 cm 2.

Atmospheric pressure was measured for the first time 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 the mercury in the tube is created only by the weight of the mercury column in the tube. Thus, 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 higher 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 mm mercury(mm Hg) at a temperature of 0°C. If the atmospheric pressure is, for example, 780 mm Hg. Art., this means that the air produces the same pressure as that produced by a vertical column of mercury 780 mm high.

Observing the height of the mercury column in the tube day after day, Torricelli discovered that this height was changing, and changes in atmospheric pressure were somehow related to changes in weather. By attaching a vertical scale next to the tube, Torricelli obtained a simple device for measuring atmospheric pressure - a barometer. Later, pressure was measured using an aneroid ("liquidless") barometer, which does not use mercury, and the pressure is measured using a metal spring. In practice, before taking readings, you need to lightly tap your finger on the glass of the device to overcome friction in the lever transmission.

Based on a Torricelli tube station cup barometer, which is the main instrument for measuring atmospheric pressure at meteorological stations nowadays. 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 section 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. To exclude the dependence of the height of the mercury column in the barometer on these parameters, the measured height is reduced 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 international system units (SI system) the basic 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 pressure field. The pressure field can be visually represented using surfaces at all points of which the pressure is the same. Such surfaces are called isobaric. To obtain a visual representation of the pressure distribution on the earth's surface, isobar maps are constructed at sea level. To do this on geographical map show atmospheric pressure measured at meteorological stations and normalized to sea level. Then points with the same pressure are connected by smooth curved lines. Areas of closed isobars with high blood pressure in the center are called pressure maxima or anticyclones, and areas of closed isobars with low blood pressure in the center are called baric lows or cyclones.

Atmospheric pressure at every point on the earth's surface does not remain constant. Sometimes the pressure changes very quickly over time, but sometimes it remains almost unchanged for quite a long time. IN diurnal course pressure there are two maxima and two minima. Maximums are observed around 10 and 22 hours local time, minimums around 4 and 16 hours. The annual variation of pressure strongly depends on physical and geographical conditions. This move is more noticeable over continents than over oceans.

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• Participant: Vertushkin Ivan Aleksandrovich
• Head: Elena Anatolyevna Vinogradova

Introduction

It's raining outside the window today. After the rain, the air temperature decreased, humidity increased and atmospheric pressure decreased. Atmospheric pressure is one of the main factors determining the state of weather and climate, so knowledge of atmospheric pressure is necessary in weather forecasting. Big practical significance has the ability to measure atmospheric pressure. And it can be measured with special barometer devices. In liquid barometers, as the weather changes, the liquid column decreases or increases.

Knowledge of atmospheric pressure is necessary in medicine, in technological processes, human life and all living organisms. There is a direct connection between changes in atmospheric pressure and changes in weather. An increase or decrease in atmospheric pressure can be a sign of weather changes and affect a person’s well-being.

Description of three interrelated physical phenomena from Everyday life:

• Relationship between weather and atmospheric pressure.
• Phenomena underlying the operation of instruments for measuring atmospheric pressure.

Relevance of the work

The relevance of the chosen topic is that at all times people, thanks to their observations of animal behavior, could predict weather changes, natural disasters, and avoid human casualties.

The influence of atmospheric pressure on our body is inevitable; sudden changes in atmospheric pressure affect a person’s well-being, and weather-dependent people especially suffer. Of course, we cannot reduce the influence of atmospheric pressure on human health, but we can help our own body. The ability to measure atmospheric pressure, knowledge of folk signs, use of homemade devices.

Goal of the work: find out what role atmospheric pressure plays in human daily life.

Tasks:

• Study the history of atmospheric pressure measurement.
• Determine whether there is a connection between weather and atmospheric pressure.
• Study the types of instruments designed to measure atmospheric pressure, made by man.
• Study the physical phenomena underlying the operation of instruments for measuring atmospheric pressure.
• Dependence of liquid pressure on the height of the liquid column in liquid barometers.

Research methods

• Literature analysis.
• Summarizing the information received.
• Observations.

Field of study: Atmosphere pressure

Hypothesis: Atmospheric pressure is important for humans .

Significance of the work: the material of this work can be used in lessons and in extracurricular activities, in the lives of my classmates, students of our school, all lovers of nature research.

Work plan

I. Theoretical part (information collection):

1. Review and analysis of literature.
2. Internet resources.

II. Practical part:

• observations;
• collecting weather information.

III. Final part:

1. Conclusions.
2. Presentation of work.

History of atmospheric pressure measurement

We live at the bottom of a huge air ocean called the atmosphere. All changes that occur in the atmosphere certainly have an impact on a person, on his health, lifestyle, because... man is an integral part of nature. Each of the factors that determine the weather: atmospheric pressure, temperature, humidity, ozone and oxygen content in the air, radioactivity, magnetic storms etc. has a direct or indirect effect on human well-being and health. Let's focus on atmospheric pressure.

Atmosphere pressure- this is the pressure of the atmosphere on all objects in it and the Earth's surface.

In 1640, the Grand Duke of Tuscany decided to build a fountain on the terrace of his palace and ordered water to be supplied from a nearby lake using a suction pump. The invited Florentine craftsmen said that this was impossible because the water had to be sucked up to a height of more than 32 feet (more than 10 meters). They could not explain why the water is not absorbed to such a height. The Duke asked the great scientist of Italy to look into it Galileo Galilei. Although the scientist was already old and sick and could not engage in experiments, he nevertheless suggested that the solution to the problem lay in the area of ​​​​determining the weight of air and its pressure on the water surface of the lake. Galileo's student Evangelista Torricelli took up the task of resolving this issue. To test his teacher's hypothesis, he conducted his famous experiment. A glass tube 1 m long, sealed at one end, was completely filled with mercury, and tightly closing the open end of the tube, turned it over with this end into a cup with mercury. Some of the mercury poured out of the tube, some remained. An airless space formed above the mercury. The atmosphere presses on the mercury in the cup, the mercury in the tube also presses on the mercury in the cup, since equilibrium has been established, these pressures are equal. To calculate the pressure of mercury in a tube means to calculate the pressure of the atmosphere. If atmospheric pressure increases or decreases, the column of mercury in the tube increases or decreases accordingly. This is how the unit of measurement of atmospheric pressure appeared - mm. rt. Art. – millimeter of mercury. While observing the level of mercury in the tube, Torricelli noticed that the level was changing, which meant that it was not constant and depended on changes in the weather. If the pressure rises, the weather will be good: cold in winter, hot in summer. If the pressure drops sharply, it means that cloudiness and saturation of air with moisture are expected. A Torricelli tube with a ruler attached represents the first instrument for measuring atmospheric pressure - a mercury barometer. (Annex 1)

Other scientists also created barometers: Robert Hooke, Robert Boyle, Emil Marriott. Water barometers were designed by the French scientist Blaise Pascal and the German burgomaster of the city of Magdeburg, Otto von Guericke. The height of such a barometer was more than 10 meters.

Different units are used to measure pressure: mm of mercury, physical atmospheres, in the SI system – Pascals.

Relationship between weather and atmospheric pressure

In Jules Verne's novel “The Fifteen-Year-Old Captain,” I was interested in the description of how to understand barometer readings.

“Captain Gul, a good meteorologist, taught him to understand the barometer readings. We will briefly tell you how to use this wonderful device.

1. When, after a long period of good weather, the barometer begins to fall sharply and continuously sure sign rain. However, if good weather stood for a very long time, the mercury column can drop for two or three days, and only after that any noticeable changes will occur in the atmosphere. In such cases, the more time passed between the beginning of the mercury fall and the beginning of the rains, the longer it will stand rainy weather.
2. On the contrary, if during a long period of rain the barometer begins to rise slowly but continuously, the onset of good weather can be confidently predicted. And good weather will remain the longer, the more time has passed between the beginning of the mercury rise and the first clear day.
3. In both cases, a change in weather that occurs immediately after the rise or fall of the mercury column persists for a very short time.
4. If the barometer rises slowly but continuously for two or three days or longer, this portends good weather, even if it has been raining non-stop all these days, and vice versa. But if the barometer rises slowly on rainy days, and immediately begins to fall when good weather comes, the good weather will not last long, and vice versa
5. In spring and autumn, a sharp drop in the barometer foreshadows windy weather. In summer, in extreme heat, it predicts a thunderstorm. In winter, especially after prolonged frosts, a rapid drop in the mercury column indicates an upcoming change in wind direction, accompanied by thaw and rain. On the contrary, an increase in mercury during prolonged frosts foretells snowfall.
6. Frequent fluctuations in the level of the mercury column, sometimes rising, sometimes falling, should in no case be considered as a sign of the approach of a long period; period of dry or rainy weather. Only a gradual and slow fall or rise in the mercury heralds the onset of a long period of stable weather.
7. When, at the end of autumn, after a long period of wind and rain, the barometer begins to rise, this heralds a north wind at the onset of frost.

Here are the general conclusions that can be drawn from the readings of this valuable device. Dick Sand was an excellent judge of the barometer's predictions and was convinced many times how correct they were. Every day he consulted his barometer so as not to be taken by surprise by changes in the weather.”

I made observations of weather changes and atmospheric pressure. And I became convinced that this dependence exists.

Instruments for measuring atmospheric pressure

For scientific and everyday purposes, you need to be able to measure atmospheric pressure. For this there are special devices – barometers. Normal atmospheric pressure is the pressure at sea level at a temperature of 15 °C. It is equal to 760 mm Hg. Art. We know that when the altitude changes by 12 meters, the atmospheric pressure changes by 1 mmHg. Art. Moreover, with increasing altitude, atmospheric pressure decreases, and with decreasing altitude, it increases.

The modern barometer is made liquidless. It's called an aneroid barometer. Metal barometers are less accurate, but not as bulky or fragile.

- a very sensitive device. For example, when climbing to the top floor of a nine-story building, due to differences in atmospheric pressure at different altitudes, we will find a decrease in atmospheric pressure by 2-3 mm Hg. Art.

A barometer can be used to determine the flight altitude of an aircraft. This barometer is called a barometric altimeter or altimeter. The idea of ​​Pascal's experiment formed the basis for the design of the altimeter. It determines the altitude above sea level by changes in atmospheric pressure.

When observing the weather in meteorology, if it is necessary to record fluctuations in atmospheric pressure over a certain period of time, they use a recorder - barograph.

(Storm Glass) (stormglass, Dutch. storm- "storm" and glass- “glass”) is a chemical or crystalline barometer consisting of a glass flask or ampoule filled with an alcohol solution in which camphor, ammonia and potassium nitrate are dissolved in certain proportions.

This chemical barometer was actively used during his sea voyages by the English hydrographer and meteorologist, Vice Admiral Robert Fitzroy, who carefully described the behavior of the barometer; this description is still used today. Therefore, stormglass is also called the "Fitzroy Barometer". From 1831–36, Fitzroy led the oceanographic expedition on HMS Beagle, which included Charles Darwin.

The barometer works as follows. The flask is hermetically sealed, but, nevertheless, the birth and disappearance of crystals constantly occurs in it. Depending on upcoming weather changes, crystals form in the liquid various shapes. Stormglass is so sensitive that it can predict sudden change weather 10 minutes before. The principle of operation has never received a complete scientific explanation. The barometer works better when located near a window, especially in reinforced concrete houses; probably in this case the barometer is not so shielded.

Baroscope– a device for monitoring changes in atmospheric pressure. You can make a baroscope with your own hands. To make a baroscope, the following equipment is required: A glass jar with a volume of 0.5 liters.

1. A piece of film from a balloon.
2. Rubber ring.
3. Lightweight straw arrow.
4. Wire for fastening the arrow.
5. Vertical scale.
6. Device body.

Dependence of liquid pressure on the height of the liquid column in liquid barometers

When atmospheric pressure changes in liquid barometers, the height of the liquid column (water or mercury) changes: when the pressure decreases, it decreases, when the pressure increases, it increases. This means that there is a dependence of the height of the liquid column on atmospheric pressure. But the liquid itself presses on the bottom and walls of the vessel.

The French scientist B. Pascal in the middle of the 17th century empirically established a law called Pascal's law:

Pressure in a liquid or gas is transmitted equally in all directions and does not depend on the orientation of the area on which it acts.

To illustrate Pascal's law, the figure shows a small rectangular prism immersed in a liquid. If we assume that the density of the prism material is equal to the density of the liquid, then the prism must be in a state of indifferent equilibrium in the liquid. This means that the pressure forces acting on the edge of the prism must be balanced. This will only happen if the pressures, i.e. the forces acting per unit surface area of ​​each face, are the same: p 1 = p 2 = p 3 = p.

The pressure of the liquid on the bottom or side walls of the vessel depends on the height of the liquid column. Pressure force on the bottom of a cylindrical vessel of height h and base area S equal to the weight of a column of liquid mg, Where m = ρ ghS is the mass of the liquid in the vessel, ρ is the density of the liquid. Therefore p = ρ ghS / S

Same pressure at depth h in accordance with Pascal's law, the liquid also affects the side walls of the vessel. Liquid column pressure ρ gh called hydrostatic pressure.

Many devices that we encounter in life use the laws of liquid and gas pressure: communicating vessels, water supply, hydraulic press, sluices, fountains, artesian well, etc.

Conclusion

Atmospheric pressure is measured in order to more likely predict possible weather changes. There is a direct connection between pressure changes and weather changes. An increase or decrease in atmospheric pressure with some probability can serve as a sign of weather changes. You need to know: if the pressure drops, then cloudy, rainy weather is expected, but if it rises, dry weather is expected, with cold weather in winter. If the pressure drops very sharply, serious bad weather is possible: a storm, heavy thunderstorm or a storm.

Even in ancient times, doctors wrote about the influence of weather on the human body. In Tibetan medicine there is a mention: “joint pain increases during rainy times and during big winds" The famous alchemist and physician Paracelsus noted: “He who has studied the winds, lightning and weather knows the origin of diseases.”

In order for a person to be comfortable, the atmospheric pressure must be equal to 760 mm. rt. Art. If the atmospheric pressure deviates even by 10 mm in one direction or another, a person feels uncomfortable and this can affect his health. Adverse phenomena are observed during the period of changes in atmospheric pressure - increase (compression) and especially its decrease (decompression) to normal. The slower the change in pressure occurs, the better and without adverse consequences the human body adapts to it.

Atmospheric pressure is the force with which the air around us presses on earth's surface. The first person to measure it was Galileo Galilei's student Evangelista Torricelli. In 1643, together with his colleague Vincenzo Viviani, he conducted a simple experiment.

Torricelli experience

How was he able to determine atmospheric pressure? Taking a meter-long tube sealed at one end, Torricelli poured mercury into it, closed the hole with his finger and, turning it over, lowered it into a bowl also filled with mercury. At the same time, some of the mercury poured out of the tube. The mercury stopped at 760 mm. from the surface level of the mercury in the bowl.

It is interesting that the result of the experiment did not depend on the diameter, inclination or even shape of the tube - the mercury always stopped at the same level. However, if the weather suddenly changed (and the atmospheric pressure fell or increased), the mercury column fell or rose a few millimeters.

Since then, atmospheric pressure has been measured in millimeters of mercury, and pressure is 760 mm. rt. Art. is considered equal to 1 atmosphere and is called normal pressure. This is how the first barometer was created - a device for measuring atmospheric pressure.

Other ways to measure atmospheric pressure

Mercury is not the only liquid that can be used to measure atmospheric pressure. Many scientists in different time they built water barometers, but since water is much lighter than mercury, their tubes rose to a height of up to 10 m. In addition, water turned into ice already at 0 ° C, which created certain inconveniences.

Modern mercury barometers use Torricelli's principle, but are somewhat more complicated. For example, a siphon barometer is a long glass tube bent into a siphon and filled with mercury. The long end of the tube is sealed, the short end is open. A small weight floats on the open surface of mercury, balanced by a counterweight. When atmospheric pressure changes, the mercury moves, dragging the float with it, which, in turn, sets in motion the counterweight connected to the arrow.

Mercury barometers are used in stationary laboratories and at meteorological stations. They are very accurate, but rather bulky, so at home or field conditions atmospheric pressure is measured using a liquid-free barometer or aneroid barometer.

How does an aneroid barometer work?

In a liquid-free barometer, fluctuations in atmospheric pressure are sensed by a small round metal box with rarefied air inside. The aneroid box has a thin corrugated membrane wall, which is pulled back by a small spring. The membrane bends outward when atmospheric pressure drops and presses inward when it rises. These movements cause deviations of the arrow moving along a special scale. The scale of the aneroid barometer is aligned with the mercury barometer, but it is still considered less precision instrument, since over time the spring and membrane lose their elasticity.