* Wear gloves when handling mercury.
The first person to measure the magnitude of air pressure is Italian scientist Toricelli. He was filled with mercury (Hg) in a glass tube with one end blocked. And he stood upside down in a bowl of mercury. Then they found that mercury descended to a height of about 76 cm and stopped.
Even if the thickness or slope of the glass tube changes, the height of the mercury column does not change. This is because the pressure is equal to the air pressure acting on the surface of the mercury and the mercury column in the glass tube.
Atmospheric pressure on several planets
1atm is the standard air pressure measured at the earth’s beach. As you climb higher from the surface, the atmospheric pressure decreases. In outer space it is ‘0’.
The moon is ‘0’atm because there is no air.
Venus is known to have about 90 times the air pressure on Earth due to the thick atmosphere of carbon dioxide.
Mars has a thin atmospheric layer of carbon dioxide. The average air pressure is about 0.006 atmospheres. In winter, the carbon dioxide freezes, so the air pressure goes down.