Book 7, Question 71
Why Do Barometers Help Forecast?
A barometer is a tool that measures air pressure. Air pressure goes up and down as weather systems move in and out. Watching the pressure rise or fall gives hints about what weather may be coming.
From the book
Page from A Million Whys Book 7
More fun facts
- The first barometer was made by Evangelista Torricelli in 1643.
- Torricelli first built a water barometer, but it needed a glass tube 60 feet long.
- Mercury is about 14 times heavier than water, so switching to mercury let him use a tube only about 35 inches long.
- Old weather sayings say a sudden fall of the barometer means high wind, and in hot weather it can mean thunder.
- Normal air pressure at sea level is 29.92 inches of mercury.
- You can make a simple barometer at home with a ruler, a glass, and a clear straw.
Sources: NOAA, NOAA, NOAA Ocean Service
Questions kids ask
Who invented the barometer?
Evangelista Torricelli, in 1643.
What does a falling barometer mean?
Falling pressure often means stormier or windier weather may be on the way.