Inventor: Evangelista Torricelli

The barometer came about in 1643 while Torricelli was experimenting with vacuums. He originally had a 34-foot tube filled with water, but he soon switched to mercury at the suggestion of his associate Galileo Galilei. Since mercury was denser, only a 3-foot tube was required to produce the same effects. The tube was left with a little air, inverted, and placed in a cistern of mercury. The outside pressure on the mercury in the cistern controlled the volume of the air.

The barometer is used for measuring pressure, which has a number of different applications. Weather forecasters use rapidly falling pressure to predict an oncoming storm whereas rising pressure typically indicates fair weather. Modified barometers are used by scuba divers to indicate depth and on airplanes to indicate altitude. Sea-level pressure is usually measured at 14.7 lb/in² or 1 atmosphere.

*Picture from Encarta Encyclopedia

Sources:

Bellis, M. (2003). Inventors from About.com. Available December 9, 2003, from About, Inc. <http://inventors.about.com/>

• This website has a useful timeline of inventions and many articles about the various inventions, their evolution, and their inventors.

"Barometer." FactMonster. (2003). Retrieved December 29, 2003, from The Columbia Electronic Encyclopedia. <http://www.factmonster.com>

• FactMonster.com is an online encyclopedia with detailed articles on a variety of topics.