Learn about Barometer
The barometer is an instrument for measuring atmospheric pressure. The pressure indicated can aid in predicting short term weather.
There are two main types of barometer in use, the mercury barometer, which can either be in the form of a "stick" or a "wheel", and the aneroid barometer, a later invention and most commonly available.
Italian Evangelista Torricelli, an associate of Galileo, is generally credited with inventing the mercury barometer in 1643. Galileo suggested to Evangelista Torricelli that he use mercury in his vacuum experiments.
A mercury barometer has a glass tube with a height of at least 84 cm, closed at one end, with an open mercury-filled reservoir at the base. The weight of the mercury creates a vacuum in the top of the tube. Mercury in the tube adjusts until the weight of the mercury column balances the atmospheric force exerted on the reservoir. more...