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# Barometer

The Barometer is an instrument used for measuring atmospheric pressure. The word is derived from the Greek terms "boras", meaning weight, and "metron" meaning measure.[1]

Created in the late 1600's, this instrument has had a substantial impact upon meteorologists, as well as the lives of everyday people. Since the first model was created many upgrades have been made allowing scientists to further understand the way atmospheric pressure works. They have made landmark discoveries about weather patterns and as technology develops, hope to continue learning more about the mysteries of weather. Overall, the barometer proves to be a very useful instrument, and one that has surely helped humans understand God's creation better.

## History

The invention of the barometer actually came about as an experiment used to create a vacuum. Although Toricelli is credited with the invention, Gasparo Berti also had a hand in creating the barometer. Evangelista Torricelli, the Italian mathematician and scientist attempted to prove that air had weight.[2] He challenged the traditional beliefs of the Aristotelians stating that air did not have lateral weight. Many great minds of the seventeenth century, including Galileo, accepting the assumption that air had no weight. Toricelli hypothesized that air did have weight and that other forces acted upon the water within the barometer. He thought the barometer could be used as an instrument because it essentially worked in the same manner as a balance. Toricelli was the first to view the experiment in this way and therefore, became known as the creator. However, historical documentations shows that Gasparo Berti actually built the barometer between 1649 and 1643. [3]

Image of an Aneroid Barometer

## Types

Barometers come in three distinct kinds making things easier for those in search of one. Each different barometer is designed for a specific purpose allowing its user to measure first and foremost, atmospheric pressure.

• Water-Based Barometer-This type of barometer has an enclosed body and is made of a glass. A spout enters the container below the water level, while the other end remains above the water level in contact with the atmosphere. [4] Another name for this instrument is the "Goether Thermometer". As the pressure drops, the water level within the instrument rises, but when pressure is increased the water level decreases. [5]
• Mercury Barometer-Consists of a glass tube 84cm or taller, with one open end and another filled with mercury. A vacuum is created in the tube due to the heavy weight of the mercury. The weight of the mercury column balances out atmospheric force affecting the reservoir. When the atmospheric pressure is high, the mercury level increases up the column, however, as the atmospheric level decreases, so also does the mercury level. After observing, Torcellini noted that, "We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight." In other words, he recognized before anyone that the change in height of the mercury was due to the change in pressure in the atmosphere. Numerous upgrades have been made to this barometer in the past few years. These changes included the siphon, wheel, cistern, and Fortin. Each change and addition allowed the user to read the instrument easier, as well as make it more sensitive. After the European Union directive issued on June 5, 2007, mercury was no longer able to be sold. This caused the production of new mercury barometers to come to a halt in Europe. [6]
• Aneroid Barometer-Aneroid Barometer-The Aneroid Barometer, derived from the root word aneroid, meaning no water, differs from traditional barometers. It is constructed out of metal and contain a very small amount of air. As air pressure increases, the walls of the barometer contract and pull closer together. A needle adorns the face of the barometer accompanied by a scale which allows users to measure pressure accurately. [7]

## Current Uses

Image of the barometer and its function

Through all the add-ons and improvements made to the barometer, its main purpose remains the same: measuring atmospheric pressure. By using the processes of air, mercury, and water, the barometer helps determine any change in weather. This makes the instrument appealing to forecasters and meteorologists who can use the barometer to detect any high pressure systems, frontal boundaries, and surface troughs. Forecasters commonly measure pressure changes within the atmosphere, enabling them to warn others of any slight or significant change set to take place. In order to do so, meteorologists look for high or low pressure systems which gather around regions and form weather patterns. Next, they view the speed of the system and its duration in a certain area. This, in accordance to the use of the barometer help give them an accurate idea of the upcoming weather. [8]

## References

1. Brief History of the Barometer Unknown Author, Accessed 1/17/11
2. The Invention of the Barometer Julian Rubin, Last updated: January 2011
3. Barometer Author Unknown, Accessed 2/4/11
4. Types of Barometer Author Unknown, Accessed 2/14/11
5. Barometer Author Unknown, Last Updated 2007
6. Barometer Author Unknown, Accessed 2/15/11
7. The Aneroid Barometer Published by the Bureau of Meteorology, Accessed 2/15/11
8. Barometer History and Uses Ray B. Spencer, Last Updated October, 2, 2009