Atmospheric Pressure
The section introduces the concept of atmospheric pressure, explaining that it is the weight of the air in the atmosphere acting on a surface. Atmospheric pressure increases as you descend toward sea level because there's more air above a surface. The pressure can be visualized as the force exerted by a long column of air above a specified area.
The significance of atmospheric pressure is demonstrated through practical applications, such as how a rubber sucker adheres to surfaces. When you press down a rubber sucker, most air escapes, creating a low-pressure area that atmospheric pressure then acts upon to keep the sucker in place.
The section emphasizes the magnitude of atmospheric pressure, noting that it can exert tremendous force, capable of crushing objects if not balanced by equal internal pressure. For instance, the pressure exerted by the air column over an area of 15 cm x 15 cm can equal the weight of a 225 kg object.
The history of atmospheric pressure demonstrations by Otto von Guericke is briefly mentioned, highlighting experiments that show the power of this invisible force.