Mathematician and student of Galileo who explained the experiment
Vincenzo Viviani
Performed the first experiment under his direction
Blaise Pascal and Florin Périer
Showed in 1648 that pressure falls with altitude, by carrying a barometer up the Puy de Dôme
Plate 044
1643
Florence, Grand Duchy of Tuscany
No photograph is shown for this exhibition. The museum displays an image only where it can show the object honestly.
About this date
The mercury experiment is attributed to Evangelista Torricelli in Florence in 1643, performed with Vincenzo Viviani.
About credit
Torricelli is credited with the explanation that air has weight and pushes on the mercury. The term “barometer” came later.
Chapter II
The world before
Life before the Barometer
Many thinkers believed that “nature abhors a vacuum.” Suction pumps could lift water only so far, and no one could explain why.
II
The human achievement
How it came about
Torricelli filled a tube with mercury, inverted it, and saw the column drop to about 76 cm, leaving an empty space at the top. He concluded that the air’s weight held the column up.
III
Understanding the invention
How it works
The Barometer, explained in two steps.
01
Step 01 of 02
Air pushes down
The atmosphere presses on the mercury in the dish and pushes the liquid up the tube.
Air pushes down
Pressure changes
IV
The transformation
What changed for humanity
Weather
Falling pressure signals storms, making forecasts possible.
Physics
Led to studies of gases and vacuums.
It proved that a vacuum can exist and that the atmosphere has weight, and it gave weather forecasters a key instrument.
V
Before and after
Life before and after The Barometer
Before
Nature “abhors” a vacuum.
After
Air has weight and pushes.
On larger screens, drag the divider (or use the arrow keys) to give more room to the world before or after.
In 1648 Pascal’s brother-in-law Florin Périer carried two barometers up the Puy de Dôme and found the mercury fell as he climbed, confirming that pressure drops with height.
Where accounts differ, this museum follows the documented record and says so.