What is it?
A barometer is a weather instrument used to measure atmospheric pressure. Atmospheric pressure can forecast short term changes in the weather. A barometer measures the change in pressure in the atmosphere which occurs when the weather changes. There are three main kinds of barometers, mercury barometers, water-based barometers and aneroid barometers.
- Decreasing (getting lower) barometric pressure indicates rainy and windy weather.
- Increasing (getting higher) barometric pressure indicates cold and dry weather.
How does it work?
Check out this website that explains how the three main types of barometers work!
Evangelista Torricelli invented the barometer in 1643. Rene Descartes described an experiment to determine atmospheric pressure as early as 1631, but there is no evidence that he built a working barometer at that time.
But you can make one!
Make a Barometer
Do you know what the air pressure is today? You can find out for yourself by measuring the air pressure on a barometer.
- small coffee can
- plastic wrap
- index card
- rubber band
- Cover the top of the can with plastic wrap. Use a rubber band to hold the plastic wrap in place. The cover should be taut making the can airtight.
- Place the straw horizontally on the plastic wrap so that two-thirds of the straw is on the can.
- Tape the straw to the middle of the plastic wrap.
- Tape the index card to the can behind the straw.
- Carefully record the location of the straw on the index card.
- After 15 minutes, record the new location of the straw on the index card.
- Continue checking and recording the straw location as often as desired.
- Be careful not to place your barometer near a window, as the barometer is sensitive to temperature as well as air pressure.
High pressure will make the plastic wrap cave in, and the straw go up. Low pressure will make the plastic wrap puff up, and the straw go down. Check your measurements with a real barometer.
What happens to your barometer when a big storm comes? Can you use your barometer to predict a storm?