Before weather satellites and radar systems could precisely measure the weather, people depended on simple barometers to measure air (or barometric) pressure. Make a barometer to give you a heads-up about weather conditions.
- Plastic wrap
- Wide-mouthed jar or large plastic cup
- Large rubber band
- Lightweight drinking straw
- White cardboard
WHAT TO DO
Step 1: Cut a piece of plastic food wrap large enough to cover the top of the jar and fold it over, halfway down the sides. Pull on the sides of the plastic wrap for a drum-tight fit — to work, this project must have an airtight seal. Wrap the rubber band around the side of the jar to secure a tight fit.
Step 2: Place the straw on top of the plastic wrap so it rests horizontally on the surface with its end near the middle of the jar opening. Use a small piece of tape to secure in place.
Step 3: Stand the cardboard behind the jar and note the height of the straw. Draw horizontal lines in fine increments on the cardboard, above and below the height of the straw.
Step 4: Place the barometer in a location where there are no drastic temperature changes (e.g., not near a radiator or window). Note the position of the straw to see changes in the straw’s position, especially before and after a changing local weather condition. Graph the changes on the cardboard gauge behind the straw, for future reference.
HOW IT WORKS
Air pressure is pushing in every direction all around us. During dry and calm weather — a high atmospheric pressure condition — it presses against the top of the jar, making the other end of the straw rise.
Conversely, approaching wind and rainstorms are usually preceded by a low-pressure condition. The lowering straw level is an indicator of this.