Barometer

A barometer is a scientific instrument used to measure atmospheric air pressure, and changes in its readings can help forecast short-term shifts in the weather. The Italian scientist Evangelista Torricelli is credited with inventing the barometer around 1643, building on earlier experiments including Giovanni Battista Baliani's 1630 siphon experiment and Gasparo Berti's rudimentary water barometer of the early 1640s; Torricelli's key contribution was recognizing that the weight of the atmosphere, rather than a force pulling the mercury upward, supports the column of mercury in the tube, making him the first to understand the barometer as a true measure of air pressure.