The essence and significance of the Torricelli’s experiment for measuring atmospheric pressure


Torricelli’s experiment, proving its existence, was as simple as possible, but at the same time unique and entailed not only the proof of the theory of the atmosphere and its pressure, but also the invention of the barometer and the discovery of vacuum.

Since the earliest times of its existence, human minds have tried to comprehend the essence of the surrounding world, the laws of nature, the history of their own origin and destination in this Universe. This aspiration generated completely different pictures of the world in different eras and in different parts of the planet: the personification of natural elements with a divine principle, the idea of the struggle between darkness and light in Persian Zoroastrianism, the creation of the world and the apocalypse in Judaism, and much more.

Features and value of experience

However, the breakthrough made by the thinkers of ancient Greece is considered the real rudiment of the rational-scientific knowledge of the world. So, one of the most important concepts of Aristotle was the introduction of the concept of “emptiness”, complete emptiness – a space where nothing exists. The idea of ​​emptiness was a frightening phenomenon for the philosopher, however, in his opinion, and impossible in nature.

After all, the empirical data available to man at that time could not reveal the concept of absolute vacuum in any way, and the whole ordinary space is filled with air. For example, if you try to blow air out of a hollow tube, then its walls will shrink. That is, not only emptiness will not remain inside, but also the space itself. And the water in the pipes always rose behind the piston, preventing the formation of a void.

Torricelli’s achievements

Evangelista Torricelli is a scientist physicist and mathematician, a true enthusiast, the author of numerous works and discoveries. Italian, originally from Florence. He was close to Benedetto Castelli, who in turn was a friend and student of Galileo Galilei. Under the guidance of Castelli, he began to study mathematics. Subsequently, inspired by many of Galileo’s writings and drawing on the content of his many treatises, he developed his genius and became Galileo’s successor.

The idea that there can be no space in the world that is not filled with a liquid, solid or gaseous substance successfully survived until the New Age – the era of human thought and scientific achievements. It was then that people regained their faith in the possibility of practical and rational knowledge of the world. Torricelli’s experience, however, was not only the result of scientific research, but also an accident.

During the construction of fountains at the palace of one of the dukes of the famous Medici dynasty, it was noticed that the water actually rises through the pipes, filling the resulting void, but only up to a certain height, after which it stops moving. This fact could not but arouse interest in the homeland of the Renaissance.

For explanations, they turned to the well-known at that time (and even better known today) physicist and mathematician Galileo Galilei. However, he, not finding an acceptable answer in logic, decided to resort to the experimental path. The experiments were commissioned by two of his students – Viviani and Torricelli.

The second achieved interesting results.

The second achieved interesting results. Torricelli’s experience assumed placing a certain volume of mercury in a glass tube (it is heavier than water, therefore it shows more visual results with small volumes of the container) so that air does not get there. In this case, the upper end was sealed, and the open lower end was placed in a cup with mercury. It turned out that mercury also did not fill the entire space of the tube, leaving a certain amount of emptiness on top. However, this empirical knowledge did not immediately receive its theoretical basis.

Torricelli made many discoveries in mathematics, mechanics and physics. Among them:

  • developed the theme “method of indivisibles”;
  • discovered the so-called Torricelli point in the plane of the triangle;
  • described the principle of movement of the centers of gravity;
  • carried out numerous studies that laid the foundation for the principles of hydraulics;
  • inventor of microscopes, lenses for telescopes;
  • invented the mercury barometer;
  • proved the existence of atmospheric pressure;
  • opened the emptiness of Torricelli, or vacuum.

Torricelli lived an interesting life full of professional discoveries and died at home in Florence in 1647.

Explaining the experience Torricelli’s

Torricelli’s experience soon became known throughout enlightened Europe, whose scientists argued about the nature of such a phenomenon. Evangelista Torricelli himself gave an explanation for the fact. Since there was no air above the mercury in the glass tube closed at the top, he explained that the height of the mercury column is literally determined by the air pressure on the mercury in the cup, forcing it more and more to go into the glass tube.

For the first time, atmospheric pressure was discovered experimentally. Torricelli’s formula stated that this pressure corresponds to the height of the mercury column: P atm = P mercury. Further research was taken up by the Frenchman Blaise Pascal, who expressed in numbers the dependence of the height of the column on the severity of the air at a particular moment, thus giving mankind the opportunity to determine the atm. pressure.

The change in atmospheric pressure is due to the movement of air. It rises where there is more air, and decreases where the air leaves. And the main reason for the movement of air is its heating and cooling from the underlying surface.

Atmospheric pressure is constantly changing as air masses move over the Earth’s surface. The area of low pressure is called a cyclone, and high pressure is called an anticyclone.

Atmospheric pressure and its significance

Atmospheric pressure is an incredibly important and necessary value for humanity. Weather conditions depend on the indicators of this parameter: if the pressure increases, this portends good warm weather without precipitation, low humidity, if it decreases, the percentage of the weather deteriorating is high, it will be cloudy and the probability of precipitation is high.

Therefore, its indicators, which make it possible to predict the weather, are so important for workers in science and medicine, for pilots and polar explorers.

Science distinguishes five layers of the atmosphere: sling-, strato-, meso-, thermo-, exosphere. The farther from the ground, the less studied the layer. As the distance from the earth decreases, the temperature in the layers decreases, but further begins to increase as it approaches the sun.

The atmosphere is made of air. The scientist sought to prove that air exerts pressure on all objects that are under its influence, and on a person as well. And as the layers of air change, its density also changes, and, accordingly, the atmospheric pressure itself. Torricelli’s experience with this phenomenon revolutionized the world of science.

The essence of the scientist’s experience

Torricelli was inspired by his vision that others did not notice. He desperately believed in Galileo Galilei’s theory that air is weight and sought to reveal that it has a direct effect on objects. To prove his innocence in the 17th century, he set up an experiment.

To conduct the experiment, he took a glass tube, on one side it was sealed. Torricelli filled the tube (which later became known as the Torricelli tube) with mercury and, turning it over, dipped it into a bowl with mercury as well. Some of the substance flowed into the container, but most remained in the container.

What prevented all the substance from flowing into the container? The pressure of the atmosphere, which affected the mercury in the bowl itself, thereby creating a rebuff to the penetration of mercury from the tube.

Calculation of indicators

It turns out that atmospheric pressure is equal to the indicator that shows mercury in the column of the tube, because it is with this force that the atmosphere presses on the liquid in the container. That is why it is customary to measure atmospheric pressure in millimeters of mercury. This is where Torricelli’s experience was, in short. Thus, the following short formula was derived:

BP is equal to the pressure of the column of mercury in the tube.

patm = pmercury = ρgh = 13600 ⋅ 9.8 ⋅ 0.76 = 101293 (Pa)

The same experience stimulated the invention of a measuring device – the mercury barometer. Now there are more modern and safer instruments for measuring atmospheric pressure, since mercury vapors are extremely dangerous. New inventions are suitable for use without consequences for human health and without harm to the environment.

In the course of his experiment, the scientist unconsciously made another discovery. He discovered a vacuum that was originally called the Torricellian void. The part of the tube that was empty was the vacuum. Although many scientists are of the opinion that in fact it was not a vacuum, but mercury vapor.

Results of the experiment Torricelli’s

Summing up, the following achievements of this experiment can be highlighted:

  1. proof of the existence of atmospheric pressure;
  2. invention of the barometer;
  3. the opening of the “Torricellian void”, or vacuum.

The message about such an effective experience, which brought not one discovery, but three at once, undoubtedly divided the world of science into before and after.

All these data and devices, now modified, still bring daily benefits to humanity.

Identical experiences are still being conducted in the education system and in the classroom.


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