Who invented the barometer?

Dear Tom,
Who invented the barometer?

Steven Allividor,
Chicago

Dear Steven,
It happened 375 years ago. Evangelista Torricelli, a student of Galileo, invented the mercury barometer in 1643. And surprisingly, it was amazingly similar to the mercury barometers in use today.

Using a glass tube 36 inches long, open at one end and closed at the other, Torricelli removed air from the tube and immersed the open end in a dish of mercury. He used mercury rather than water because water could evaporate. Moreover, because of its great mass and density, mercury rarely rose above 31 inches in the tube. Water, however, would rise 408 inches (34 feet).

Torricelli measured the distance in inches that the mercury in his barometer rose and then used that measurement to indicate the atmosphere’s pressure.