what is a barometer?

A barometer is an instrument for measuring atmospheric pressure. Atmospheric pressure (sometimes called barometric pressure) refers to how much the air above and around us weighs – that's right, air does weigh something!

Changes in atmospheric pressure, combined with observing changes in wind, humidity and temperature can be used to forecast weather patterns. Generally speaking, higher pressure can indicate fine weather and low pressure can indicate rain or storms.

Barometers are often combined with other instruments such as thermometers and hygrometers (to measure humidity) to form home weather stations.

Evangelista Torricelli – a student of Galileo – first proved that air pressure is subject to variations. He is widely credited with the invention of the first mercury barometer in 1643.

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