All living beings on Earth do not notice the pressure that the grand air shell of our planet exerts on them. The reason is that from birth they are accustomed to the effects of the atmosphere on them, and their organisms are biologically adapted to it.
Meanwhile, such a gaseous cloud actually has considerable weight. It is held by the gravity of the planet, so it does not disappear into boundless space, extending upward for a thousand kilometers. And this means that the air shell exerts pressure on everything located on the surface of the globe. How much is one atmosphere in Pascals? Scientists managed to express air pressure in numbers back in the 17th century.
Atmosphere pressure
In Regensburg in 1654, Otto von Guericke showed the spectacular experience to Emperor Ferdinand III and his learned brothers. The German physicist took two copper hollow hemispheres, small in size (about 35.6 cm in diameter). Then he pressed them tightly to each other, connecting them with a leather ring, and pumped out the air from the inside through the insertion tube and pump. After which it was impossible to separate the hemispheres. Moreover, sixteen horses tied to iron rings from two ends on each side of the formed sphere could not do this.
This experiment showed the world the effect on surrounding objects of pressure. It was this force that so squeezed both parts of the sphere. So, its value is truly impressive. Two years later, a wonderful experience was repeated in Magdeburg. Already 24 horses tried to break the sphere there, but with the same success. The indicated hemispheres used during the experiment went down in history under the name Magdeburg. They are still kept in the German museum.
One atmosphere in Pascals
How to calculate the pressure of the gaseous mantle of the planet? It would not be easier if the density of air and the height of the air envelope were known with accuracy. But in the XVII century, scientists could not yet know such things. However, they coped with this task perfectly. And this was first done by a student of Galileo - Italian Torricelli.
He took a meter-long glass tube and filled it with mercury, previously sealing one of the ends. And the open part was lowered into a vessel with the same substance. At the same time, part of the mercury from the tube rushed down. However, not all spilled out. And the height of the remaining column was about 760 mm. It was this experience that subsequently made it easy to calculate: how many Pascals in one atmosphere. This number is approximately 101 300 Pa. Such is the value of normal atmospheric pressure.
Explanation of Torricelli's Experience
Atmospheric pressure affects all earthly bodies. But it is imperceptible, because it is balanced by the action of air located in the objects themselves and living organisms. The experiment with the Magdeburg hemispheres eloquently showed what would happen if the gas did not have the ability to penetrate almost everywhere. In the resulting sphere, airless space was artificially created. As a result, it turned out to be unusually strong and inseparable, compressed from all sides by one atmosphere, in Pascals the pressure value of which, as we already know, is very significant.
These same laws are the basis for the operation of pumps. Liquid rushes into the resulting airless space. It rises until the existing air pressure and substances do not balance each other. And the height of the column depends on the density of the liquid.
Knowing this, Torricelli measured the pressure created by one atmosphere. In Pascal, he could not translate this value, of course. This was done later. Therefore, he measured it in millimeters of mercury. It is known that in such units atmospheric pressure is usually measured in our time.
How to translate the atmosphere in Pascal
The Frenchman Blaise Pascal (his portrait is a little higher), whose pressure units were named after learning about the Torricelli experiments, repeated similar experiments at different heights, using, in addition to mercury, water and other liquids. And this finally proved the presence and effect of atmospheric pressure on earthly bodies and substances, although there were many doubters in those days.
The following shows how to translate atmospheric pressure into Pascals and other units.
This value is not constant and depends on many indicators. First of all, from altitude. As Pascal proved, the higher you go to the top of the mountain, the less pressure you get. This is easily explained. After all, the depth of the air envelope decreases, as does its density. And already at an altitude of approximately 5.5 km, the pressure indicators are halved. And if you climb 11 km, then this value will decrease by four times.
In addition, atmospheric pressure depends on the weather. That's why this indicator is considered significant in its forecasts. For example, the higher the pressure in summer, the more likely it is that on this day the sun will please with its rays and there will be no precipitation.