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# Atmospheric pressure. Torricelli and Pascal

## What is atmospheric pressure, how do we observe it and how do we measure it?

Online atmospheric pressure simulations will allow us to better understand what atmospheric pressure is, how it is produced and how it can be measured.

Atmospheric pressure is the force per unit area exerted by the air that forms the atmosphere on the earth’s surface. It is a fundamental phenomenon in the atmosphere and plays a crucial role in various aspects of our daily lives and natural processes.

The SI unit of pressure is the pascal (Pa), named after Blaise Pascal. One pascal is equal to a force of one newton per square meter (N/m²). Other units of measurement are the bar (bar, equivalent to 100,000 Pa), the millimeter of mercury (mmHg), which is based on the experiment performed by Evangelista Torricelli in the 17th century, or the atmosphere (equivalent to 760 mmHg or 1.013 bar).

Atmospheric pressure varies with altitude, since the amount of air over a given area decreases as we move away from the earth’s surface. The higher the altitude, the lower the atmospheric pressure. Atmospheric pressure also influences climate and the formation of weather systems. Changes in atmospheric pressure can indicate the arrival of cold or warm fronts, and areas of high and low pressure are responsible for wind patterns and atmospheric currents.

Barometers are instruments used to measure atmospheric pressure. There are different types, such as the mercury barometer and the aneroid barometer. In addition, weather stations and satellites also collect atmospheric pressure data for weather analysis and prediction.

## Concept of Pressure

In this simulation it is possible to observe how the pressure that an object exerts on its base changes when the weight of the object or its contact surface changes.

## Torricelli’s experiment

The first person to measure atmospheric pressure was the Italian scientist Torricelli. He drags the mercury tube into the vessel and checks what happens to its level depending on the atmospheric pressure of the planet.