The Italian scientist Evangelista Torricelli was born on 15 October 1608
in
Faenza. Torricelli studied for two years at the
Jesuit college at
Faenza, followed by two years of self-study. Because Torricelli showed
such great talents for the sciences, his uncle sent him to
Rome in
1626, where he became a scholar of the
abbot Benedetto Castelli.
Castelli, a student and friend of Galileo Galilei, taught the 18
year old Torricelli the work of the old master on the laws of motion.
Torricelli was secretary for Castelli from 1626 to 1632. During the next
nine years he became secretary for Monsignor Giovanni Ciampoli,
another friend of Galileo and governor of various cities in the
Marches and Umbria. Not much is known of this period; Torricelli may
have been secretary for several other people.
Inspired by Galileo's work, Torricelli wrote a treatise on mechanics
called De Motu ("Concerning Movement"), that dealt with the
movement of projectiles. Benedetto Castelli was highly
impressed, and sent the document with strong recommendations to Galileo
Galilei. Consequently, Galileo invited the young scholar. It was no
earlier than 1641, three months before Galileo's death that the two
scientists finally met. There is some speculation that Torricelli was
reluctant to visit Galileo, because of Galileo's problems with the
inquisition, but the death of Torricelli's mother also may have played
a role. However, after a sad letter from Galileo describing his poor
health and a possible sudden death, Torricelli left for Florence
instantly. He remained with Galileo until his death on January 8, 1642.
After Galileo's death, Ferdinando II de Medici requested that
Torricelli take over Galileo's position as mathematician to the
Grand Duke of Tuscany and reader in mathematics at Pisa
University. This was a highly respected and well paid position
that Torricelli kept until his death.
Torricelli's scientific contributions include many solutions to
mathematical problems, such as the finding of the area and the center of
gravity of a cycloid, properties of curves and
shapes, and a continuation of Galileo's work on the motion of
projectiles. Torricelli has sometimes been called the father of
hydrodynamics, due to his discovery of the law of efflux of a
liquid through a small aperture in the wall of a vessel (the
effluent velocity is equal to that of a droplet in a vacuum falling from
the top of the water level to the hole.) He was also a skilled lens
grinder, making lenses for telescopes and
microscopes. This was a significant source of income in the
last period of his life.
Despite all his achievements, Torricelli became most famous for his
invention of the barometer. Pump makers of the Grand Duke of Tuscany
observed that they could not raise water over great heights with their
traditional suction pumps. Earlier, Galileo had already
struggled with this observation stating that indeed nature abhors a
vacuum, but that the horror only extends to approximately thirty two
feet. Torricelli found the correct explanation; he filled a three feet
long tube with quicksilver (mercury), closed one end, and placed the
tube with the open end vertically in a basin of mercury. The level fell
to about twenty-eight inches of mercury, creating an empty space
(Torricellian vacuum). Torricelli observed that the height of the mercury level was
dependent on the surrounding air pressure, and thus created the first
barometer.
Torricelli died due to an unknown illness in Florence on 24 or 25
October, 1647. In honor of his work, a unit of measure (torr) is named
after him.