how does a barometer work

A barometer works by measuring atmospheric pressure, which is the force exerted by the air on Earth's surface. There are two common types: mercury barometers and aneroid barometers. In a mercury barometer, a glass tube is filled with mercury and inverted into a mercury-filled basin. Atmospheric pressure pushes on the mercury in the basin, causing the mercury level inside the tube to rise or fall. The height of the mercury column balances the atmospheric pressure, so higher pressure raises the mercury level, and lower pressure lowers it. An aneroid barometer uses a sealed, flexible metal box that changes shape as the atmospheric pressure varies. These changes drive mechanical levers that move a needle on the dial, indicating the pressure. Barometers are used to track changes in atmospheric pressure, which helps forecast weather changes—rising pressure generally means fair weather, while falling pressure suggests rain or storms.