A barometer is a measurement device that measures the force being created by the atmosphere. Water, air, or mercury are the common ways it is measured.
Why is Pressure Important
Barometric pressure helps weather predictors determine what type of system is building. If the pressure is rising, typically a high pressure is enterring the area (or a storm is leaving), meaning that fairer weather is due. Conversely, falling pressure indicates that the pressure is lessening, often meaning that a low is moving into the area or that a high is leaving. This indicates that fair weather is leaving.
Who invented the barometer?
An Italian scientist named Evangelista Torricelli made the first barometer. Following an idea by another scientists named Galileo, Torricelli filled a glass tube with mercury (not a good idea!). While trying to study vacuums, Torricelli noticed that the mercury rose and fell due to changes in the atmosphere. Viola, the barometer was made.