Atmospheric Pressure: Torricelli's Experiment and Barometers
The ocean of air above your head is pressing on you right now
Big Idea: Our planet is wrapped in a thick layer of air called the atmosphere. Air has weight, so this whole ocean of air presses down on everything below it. That squeeze is called atmospheric pressure, and near the sea it is about 100,000 Pa — roughly the weight of a small car spread over every square metre.
By the end you will be able to:
- explain why the air around us presses in every direction,
- describe Torricelli's experiment and why the mercury stops at about 760 mm,
- use the formula p = ρgh to turn a mercury column into pascals,
- tell a mercury barometer from an aneroid barometer,
- explain why pressure drops as you climb the mountains of Kyrgyzstan.