Invented by : Evangelista Torricelli
Invented in year : 1643
A Barometer is an instrument used to measure atmospheric pressure. It can measure the pressure exerted by the atmosphere by using water, air, or mercury. There are two common types of Barometer, these are the Aneroid Barometer And the Mercurial Barometer which was invented first. The classic Mercury Barometer is typically a glass tube about 3 feet high with one end open and the other end sealed. The tube is filled with mercury. This glass tube sits upside down in a container, called the reservoir, which also contains mercury. The mercury level in the glass tube falls, creating a vacuum at the top. Pressure tendency can forecast short term changes in the weather. The barometer works by balancing the weight of mercury in the glass tube against the atmospheric pressure just like a set of scales. If the weight of mercury is less than the atmospheric pressure, the mercury level in the glass tube rises. If the weight of mercury is more than the atmospheric pressure, the mercury level falls. Atmospheric pressure is basically the weight of air in the atmosphere above the reservoir, so the level of mercury continues to change until the weight of mercury in the glass tube is exactly equal to the weight of air above the reservoir. In areas of low pressure, air is rising away from the surface of the earth more quickly than it can be replaced by air flowing in from surrounding areas. This reduces the weight of air above the reservoir so the mercury level drops to a lower level. In contrast, in areas of high pressure, air is sinking toward the surface of the earth more quickly than it can flow out to surrounding areas. There is more air above the reservoir, so the weight of air is higher and the mercury rises to a higher level to balance things out. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems, and frontal boundaries.
The Invention
Evangelista Torricelli invented the first barometer. It was also known as the Torricelli's Tube. He was born October 15, 1608, in Faenza, Italy. He was a physicist and mathematician. It was Galileo that suggested Evangelista Torricelli use mercury in his vacuum experiments. Torricelli filled a four-foot long glass tube with mercury and inverted the tube into a dish. Some of the mercury did not escape from the tube and Torricelli observed the vacuum that was created. He became the first scientist to create a sustained vacuum and to discover the principle of a barometer. Torricelli realized that the variation of the height of the mercury from day to day was caused by changes in the atmospheric pressure. Torricelli built the first mercury barometer around 1644. Pump makers of the Grand Duke of Tuscany attempted to raise water to a height of forty feet or more, but found that thirty-two feet was the limit to which it would rise in the suction pump. Strange enough, Galileo, who knew all about the weight of the air, had recourse to the old theory that Nature Abhors a Vacuum, modifying the law by stating that the horror extended only to about thirty-two feet. Torricelli at once conceived the correct explanation. He tried the experiment with quicksilver, a liquid fourteen times as heavy as water, expecting the column which would counterbalance the air to be proportionally smaller. He filled a tube three feet long, and hermetically closed at one end, with mercury and set it vertically with the open end in a basin of mercury, taking care that no air-bubbles should get into the tube. The column of mercury invariably fell to about twenty-eight inches, leaving an empty space (Torricellian vacuum) above its level .
Role of Barometer in the Improvement Of Human Life
- Barometer became a commonly used instrument for weather predictions. This further helped in weather forecasting which helped farmers, geologists, scientists and people in general
- As barometers measure air pressure, they were also used for measuring altitude, or height above the ground, such as the height of a mountain, and they were often used to measure altitude aboard a hot air balloon.
- They are also used by miners in caves to determine the depth of a mine.
- The barometer is today one of the most important scientific instruments, while the Torricellian method of getting a very high vacuum is still often employed.
