25 October 2016

Evangelista Torricelli – inventor of the barometer

Physicist's name lives on in scientific terminology

Evangelista Torricelli: a portrait by Lorenzo Lippi, shortly before he died
Evangelista Torricelli: a portrait by
Lorenzo Lippi, shortly before he died
The inventor of the barometer, Evangelista Torricelli, died on this day in 1647 in Florence at the age of just 39.

A disciple of Galileo, Torricelli made many mathematical and scientific advances during his short life and had an asteroid and a crater on the moon named after him.

Torricelli was born into a poor family from Faenza in the province of Ravenna.

He was given a basic education in Faenza and then sent to a Jesuit college to study Mathematics and Philosophy.

He studied science under the Benedictine monk, Benedetto Castelli, a professor of Mathematics at the Collegio della Sapienza, now known as the Sapienza University of Rome, who had been a student of Galileo Galilei.

Torricelli also became an admirer of Galileo and, after the great scientist’s Dialogues of the New Science were published, Torricelli wrote to him telling him he had read it with ‘delight’.

Galileo was condemned by the Vatican in 1633 for his beliefs and held prisoner at his villa in Arcetri. For the last three months of Galileo’s life, Torricelli worked for him there as his secretary and assistant.

Early barometers based on Torricelli's findings
Early barometers based on
Torricelli's findings
After Galileo’s death the Grand Duke Ferdinand II de Medici asked Torricelli to succeed Galileo as Chair of Mathematics at the University of Pisa.

In this role Torricelli solved some of the great mathematical problems of the day and described his observations in his book, Opera Geometrica. His work contributed to the eventual development of integral calculus.

Torricelli was also interested in optics and designed and built telescopes and microscopes.

But his most important invention was the mercury barometer, which he produced after he had discovered the principle of the barometer while trying to find a solution to the limitations of the suction pump in forcing water upwards.

He designed a kind of vacuum pump using mercury. He filled a metre-long glass tube, closed at one end, with mercury and inverted the tube so that the open end rested on the bottom of a vessel containing more mercury.  The mercury in the tube fell until it reached the point at which the weight of the mercury in the tube was balanced against the pressure exerted by air on the mercury in the vessel, leaving a vacuum at the top of the tube.

The statue of Torricelli in Faenza
The statue of Torricelli in Faenza
Torricelli noted that the height of the mercury in the column varied from day to day, which he concluded was due to changes in atmospheric pressure. In 1644, he turned these discoveries into the first instrument to measure atmospheric pressure.

Scientific terms such as the Torricellian tube and Torricellian vacuum are named after the scientist, as is the torr, a unit of pressure in vacuum measurements. Torricelli’s Law refers to the speed of a fluid flowing out of an opening and Torricelli’s Trumpet relates to mathematical discoveries he made about infinity.

Torricelli died in Florence ten days after his 39th birthday and was buried at the Basilica of San Lorenzo.

Several Italian submarines have been named after Torricelli in honour of his work.

Travel tip:

A statue of Torricelli was erected in 1868 in Faenza, the city where he was born and educated, in recognition of all he had done to advance science during his short lifetime. The white marble statue can be found in the park of San Francesco in Corso Giuseppe Garibaldi.

An example of faience majolica-ware
An example of faience majolica-ware
Travel tip:

Faenza is in the Emilia-Romagna region, about 50 kilometres south east of Bologna. The city is famous for the manufacture of a type of decorative majolica-ware known as faience. It is also home to the International Museum of Ceramics, which has examples of ceramics from ancient times, the Middle Ages and the 18th and 19th centuries as well as displaying work by important contemporary artists. The museum is in Viale Baccarini in Faenza. For more information visit www.micfaenza.org.

More reading:

(Picture of faience plate by Rosco CC BY-SA 2.5)


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