All living beings on Earth do not notice the pressure exerted on them by the grandiose air shell of our planet. The reason is that they are accustomed from birth to exposure to the atmosphere, and their organisms are biologically adapted to it.
Meanwhile, such a gaseous cloud actually has a considerable weight. It is held by the gravity of the planet, thanks to which it does not evaporate into endless space, stretching upwards 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.
Atmospheric pressure
In Regensburg in 1654, Otto von Guericke gave Emperor Ferdinand III and his fellow scientists a spectacular experience. The German physicist took two hollow copper hemispheres, small in size (about 35.6 cm in diameter). Thenhe pressed them tightly against each other, connecting them with a leather ring, and pumped out the air from the inside by means of an insert tube and a pump. After that, the hemispheres could not be separated. Moreover, sixteen horses tied to iron rings at both ends on each side of the resulting sphere could not do it.
This experiment demonstrated to the world the effects of pressure on surrounding objects. It was this force that squeezed both parts of the sphere so much. So, its size is truly impressive. Two years later, the remarkable experience was repeated in Magdeburg. There already 24 horses tried to break the sphere, but with the same success. These hemispheres used during the experiment went down in history under the name of Magdeburg. They are still kept in the German Museum.
One atmosphere in Pascals
How to calculate the pressure of the planet's gaseous mantle? Nothing would be easier if the density of the air and the height of the air shell were known with accuracy. But in the 17th century, scientists could not yet know such things. However, they did an excellent job. And this was first done by a student of Galileo - the Italian Torricelli.
He took a meter-long glass tube and filled it with mercury after soldering one of the ends. And he lowered the open part 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 are in one atmosphere. This number is approximatelyis 101,300 Pa. This is the value of normal atmospheric pressure.
Explanation of Torricelli's experiment
The pressure of the atmosphere affects all terrestrial bodies. But it is imperceptible, because it is balanced by the action of air, which is 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. An airless space was artificially created in the resulting sphere. As a result, it turned out to be unusually strong and inseparable, squeezed from all sides by one atmosphere, in Pascals, the pressure value of which, as we already know, is very significant.
The same laws underlie pumps. Liquid rushes into the formed airless space. It rises until the existing air pressure and substances 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. Of course, he still could not translate this value into Pascals. This was done later. Therefore, he measured it in millimeters of mercury. It is known that atmospheric pressure is usually measured in similar units in our time.
How to convert atmospheres to Pascals
The Frenchman Blaise Pascal (his portrait is a little higher), whose name the pressure units are named after, having learned about Torricelli's 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 terrestrial bodies and substances, although there were many doubters in those days.
The following shows how to convert pressure in atmospheres to Pascals and other units.
This value is not constant and depends on many indicators. First of all, from the height above sea level. As Pascal proved, the higher you climb to the top of the mountain, the less pressure becomes. This is easily explained. After all, the depth of the air shell decreases, as does its density. And already at an altitude of approximately equal to 5.5 km, the pressure indicators are halved. And if you climb 11 km, then this value will decrease by four times.
In addition, the atmospheric pressure depends on the weather. That is 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.
