Posted by on Jul 6, 2016 in Tell Me Why |

Who Invented the Barometer?

The barometer is an instrument for measuring atmospheric pressure. Evangelista Torricelli invented the barometer, also known as the ‘Torricelli’s Tube’. “This instrument is named from two Greek words, signifying two measures of weight, since by it a column of air is weighed against a column of mercury.”

Evangelista Torricelli was born on October 15, 1608, in Faenza, Italy and died on October 22, 1647 in Florence, Italy. He was a physicist and mathematician. In 1641, he moved to Florence to assist the astronomer Galileo.

It was Galileo who suggested to Evangelista Torricelli that to 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. Evangelista Torricelli 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.

The barometer arose from the need to solve a practical problem. Pump makers of the Grand Duke of Tuscany attempted to raise water to a height of 12 meters or more, but found that 10 meters was the limit with a suction pump (as recounted in Galileo’s Dialogue). Torricelli employed mercury, thirteen times more dense than water.

In 1643 he created a tube approximately one meter long, sealed at the top, filled it with mercury, and set it vertically into a basin of mercury. The column of mercury fell to about 76 cm, leaving a Torricellian vacuum above.

As we now know, the column’s height fluctuated with changing atmospheric pressure; this was the first barometer. The discovery of the principle of the barometer has perpetuated his fame (“Torricellian tube”, “Torricellian vacuum”).

The torr, a unit of pressure used in vacuum measurements, is named after him. “12 years before Torricelli’s observations, Descartes, the French philosopher, had made the same observation, although he does not appear to have turned it to any account.

Content for this question contributed by Edwinn Camaya, resident of Burlington, Boone County, Kentucky, USA