barometeri

A barometer is an instrument used to measure atmospheric pressure. Atmospheric pressure is the weight of the air in the Earth's atmosphere pressing down on the surface. Barometers are crucial in meteorology for weather forecasting. Changes in atmospheric pressure are often indicators of upcoming weather changes. A falling barometer typically suggests worsening weather, such as rain or storms, while a rising barometer often indicates improving or settled weather conditions.

There are two main types of barometers: mercury barometers and aneroid barometers. The mercury barometer, invented by Evangelista Torricelli in the 17th century, consists of a glass tube sealed at one end and filled with mercury. This tube is then inverted into a reservoir of mercury. The atmospheric pressure pushes down on the mercury in the reservoir, supporting a column of mercury in the tube. The height of this mercury column is a direct measure of the atmospheric pressure.

Aneroid barometers are more common for everyday use and do not contain mercury. They use a small, flexible, sealed metal box called an aneroid cell. This cell is evacuated of air, so that changes in external atmospheric pressure cause the cell to expand or contract. These small movements are amplified by a system of levers and springs, which move a needle on a dial calibrated to show pressure readings. Both types of barometers are essential tools for understanding and predicting weather patterns.