A barometer is an instrument used to measure atmospheric pressure. It helps determine whether air pressure is increasing, decreasing, or remaining stable. It operates by balancing atmospheric pressure with the pressure generated by a column of mercury in a closed tube.
When atmospheric pressure is high, the mercury column rises, indicating good weather. Conversely, when atmospheric pressure is low, the mercury column descends, which may indicate weather changes such as an approaching storm.
The barometer is a useful tool for predicting weather changes and is used in meteorology as well as maritime navigation.
