Barometer
Nickname/Alias: Torricellian tube
Details:
Having shown how to create a vacuum, in 1644 Evangelista [invented by] Torricelli* went on to invent the first barometer. The standard mercury barometer measures atmospheric pressure. To achieve this, a glass tube, sealed at one end, is filled with mercury, and then inverted into a reservoir of mercury (later this took the form of the glass bulb at the lower end of the tube).
After inversion, thank to gravity the mercury level in the tube falls and leaves behind a vacuum at the top of the tube. When circumstances (such as a change in barometric pressure, or a rise/fall of the height above sea level of the tube) change, the local increase/decrease in atmospheric pressure shows as a rise/fall of the level of the mercury in the tube.
These readings are essential in the analysis of barometric pressure regarding the weather. High pressure is fair, low pressure stormy.
ONE LINER: The barometer
Bibliography:
- Barometer.http://inventors.about.com
Wikipedia (See node 2)
Multimedia:
Connections II #5 "Something for Nothing"]