What is a barometer

A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis.

Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from different places, and matching the atmospheric pressure to indicate  the corresponding altitude via an instrument dial, while a barometer is kept stationary and measures subtle pressure changes caused by weather. The main exception is a ship at sea, which can use a barometer because their elevation does not change. The presence of weather systems, aircraft altimeters may need to be adjusted as they fly between regions of varying normalized atmospheric pressure.

Although Evangelista Torricelli is universally credited with inventing the barometer in 1643,historical documentation also suggests Gasparo Berti, an Italian mathematician and astronomer,unintentionally built a water barometer sometime between 1640 and 1643. French scientist and philosopher René Descartes described the design of an experiment to determine atmospheric pressure as early as 1631, but there is no evidence that he built a working barometer at that time.