What does a barometer measure?

A barometer measures atmospheric pressure, and this is accomplished by determining the height of a column of liquid, typically mercury or water, that is supported by that pressure. In a standard mercury barometer, the atmospheric pressure pushes down on the surface of the liquid in a reservoir, causing the mercury to rise in the tube. The height of the mercury column directly correlates to the pressure exerted by the atmosphere; hence, a greater atmospheric pressure results in a taller column of mercury.

Understanding this principle is essential because atmospheric pressure can vary with weather conditions and altitude, which can be important in fields like meteorology and aviation. The use of a barometer is foundational in understanding how atmospheric pressure impacts weather patterns and respiratory physiology, especially in regard to how pressure gradients influence gas exchange within the lungs.

The volume of gases, density of vapors, and temperature of gases are related concepts in respiratory care and atmospheric science but are not directly measured by a barometer. These factors can influence pressure and respiratory function, but they are distinct measurements from what a barometer specifically does.