BAROMETER1639: Galileo Galilei challenge

the “emptiness resistance

Water cannot be pumped under vacuum to a height

greater than 10.2 m

Blaise Pascal's Barrel Experiment

Rouen France C. 1640

From El Museo Popular Published Madrid 1889

https://www.bing.com/images/blob?bcid=SHMxbOJphuYAew

Evangelista Torricelli (1643)

He was a student of Galileo. He replace water with

mercury, a fluid about 13 times denser than water.

Barometer: Greek word "baros" = weight

the air in the atmosphere has a weight equal to the

weight of a water column of 34 feet (10 meters).

mercury column = 760 mm of Hg = 760 torr

We live in a "sea of air" that exerts a pressure

analogous to the pressure of water on submerged

objects.

Project Gutenberg of Canada ebook #403

BAROMETERTorricelli's type experiment in Pisa in 1644

the height of the mercury column is always fixed at

760 mm regardless the shape of the container.

“We live submerged at the bottom of an ocean of the

element air, which by unquestioned experiments is

known to have weight.”

https://catalogue.museogalileo.it/gallery/Torricellian

Experiment.html

Blaise Pascal Paris 1647

Tested the hypothesis of Torricelli and confirmed

(with experiments) that the atmosphere is indeed

responsible for the height of the column of mercury

Unit of pressure pascal (Pa): Pa = 1 N/m2

a fluid about 13 times denser than water

https://www.britannica.com/biography/Blaise-Pascal

Barometer principle

At equal surface area, the mass of the column of

water (10.3 m) is the same that of mercury metal

(760 mm Hg).

The same observation was made by using alcohol

instead of water.

The ratio: "weight of the atmosphere / surface" is a

value equivalent to that of the liquid inside the tube.

https://scied.ucar.edu/sites/default/files/images/lon

g-content-page/torricelli.jpg

BAROMETERAir Pressure measurement (1648)

Florin Périer carried out atmospheric pressure

measurements at different heights at Puy de Dôme

(France).

The column of mercury fell and rose progressively of

about three inches as the ascent and descent were

made.

The Torricelli – Pascal hypothesis is verified.

https://scied.ucar.edu/sites/default/files/images/lon

g-content-page/torricelli.jpg

Equivalent weight of the atmosphere

roughly 1 kg/cm2

Force corresponding to the mass of 1 m2 of air

at the earth surface

f = ma f = mg→

f = (10340 kg) x (9.81 m/s2) = 1.013x105 N

since pressure = Pa = N/m2

pressure = 101.3 kPa

https://chem.libretexts.org/Courses/Valley_City_Stat

e_University/Chem_115/Chapter_7%3A_States_of_

Matter/7.2%3A_Pressure

U-tube pressure gauge

The difference in level in the tube corresponds to the

different pressure between the two openings

∆P in in mm of Hg

https://www.hydraulicspneumatics.com/

BAROMETERRobert Boyle setup (1660)

Used to find the relation between the pressure and

the volume of a gas

V P= constant

https://kaiserscience.wordpress.com/tag/gas-laws/

The ideal gas law