Barometer - History of Barometer


Evangelista Torricelli is the inventor of the barometer, which is a device that can measure air pressure. He made the first barometer in Florence, Italy, in 1644. His invention has many modern uses, but barometers are especially important for weather monitoring and prediction. Oncoming storms cause fast drops in air pressure, so barometer readings provide essential warnings for ships at sea.

  • Most scientists of his day thought that air had no weight, but Evangelista Torricelli suspected that it did. He worked with tubes filled with mercury (a liquid metal that we now know is dangerous). He found that if he sealed the tubes at one end, the mercury would fall away from the sealed end, but stop at the same level every time. He believed that this showed that there was pressure from the air balancing with the weight of the mercury.
  • A complete theory of how the barometer worked was developed by the French scientist Blaise Pascal. He realized that if air had vertical weight, the pressure would be lower at higher altitudes. In 1646, he asked a relative to carry a barometer up a mountain, and record the mercury height as he went. Sure enough, the mercury level dropped as his relative climbed higher. This proved that air pressure is caused by the vertical weight of air.
  • The first altimeters for airplanes were basically barometers. They determined altitude by measuring the change in air pressure with height.
  • Barometric pressure is higher on sunny days, and low on stormy days. Measuring the change in air pressure that comes along with storm systems is a vital part of weather prediction.
  • New types of barometers have been developed over time, including electronic ones that are fractions of a millimeter in size. These are small enough to be installed in cell phones!

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