History
Evangelista Torricelli
The first barometer is thought to have been built sometime in
the early1600’s by Gasparo Berti. However, it
was a student of Galileo's by the
name of Evangelista Torricelli who invented
the first barometer containing
mercury. (Middleton, 1964).
It was Torricelli who applied the concepts of a
vacuum to his ideas about
measuring air pressure (Middleton, 1964).
The most efficient vacuum pump however, could not raise water above 33 feet
(Williams, 1999, p. 49). Toriricelli was aware that air contained weight; he
decided that a raised piston reduced the pressure inside a water pump, allowing
the weight of air pushing on the surface of the water to force it
upward and fill the vacuum (Williams, 1999, p. 49). He
then tested his theory by filling a four-foot glass tune with mercury and
inverted it into a dish of mercury (Williams, 1999, p. 49-50). Rene Descartes
applied the first scale to a Torricelli tube and used it to measure atmospheric
pressure differences (Williams, 1999, p. 50). It was Robert Boyle who gave the
barometer its name (Williams, 1999, p. 50).
the early1600’s by Gasparo Berti. However, it
was a student of Galileo's by the
name of Evangelista Torricelli who invented
the first barometer containing
mercury. (Middleton, 1964).
It was Torricelli who applied the concepts of a
vacuum to his ideas about
measuring air pressure (Middleton, 1964).
The most efficient vacuum pump however, could not raise water above 33 feet
(Williams, 1999, p. 49). Toriricelli was aware that air contained weight; he
decided that a raised piston reduced the pressure inside a water pump, allowing
the weight of air pushing on the surface of the water to force it
upward and fill the vacuum (Williams, 1999, p. 49). He
then tested his theory by filling a four-foot glass tune with mercury and
inverted it into a dish of mercury (Williams, 1999, p. 49-50). Rene Descartes
applied the first scale to a Torricelli tube and used it to measure atmospheric
pressure differences (Williams, 1999, p. 50). It was Robert Boyle who gave the
barometer its name (Williams, 1999, p. 50).
What Does it all Mean???
What does it mean when a barometer is rising or falling? A "rising" barometer indicates increasing air pressure; a
"falling" barometer indicates decreasing air pressure. An interesting point
regarding air pressure is that it is different at different points on the planet
and it changes over time.
"falling" barometer indicates decreasing air pressure. An interesting point
regarding air pressure is that it is different at different points on the planet
and it changes over time.