Photograph by Andrew Greto
Those friendly folks on the weather broadcasts often talk about how high- and low-pressure systems affect the daily forecast. This simple gizmo lets kids observe changes in air (or barometric) pressure and make some weather predictions of their own.
- Cut off the neck of a deflated balloon.
- Stretch the rest of the balloon over the mouth of a large jar. Pull it perfectly flat and taut and secure it with two or more rubber bands.
- Fold the end of one straw and insert it into another. Secure them with tape. Cut a tab and flatten one end as shown.
- At the opposite end, insert a paper arrow, cut so that its straight part fits snugly into the straw.
- Secure the straw's tab to the balloon with a dab of white glue. Tape it in place until the glue dries.
Set the barometer against a wall, out of direct sun, where it won't be disturbed. Place a chalkboard or a sheet of paper behind it. Mark a line where the arrow is level, then mark a few lines above and below it. Add labels as shown.
How It Works
The air pressure inside the jar stays constant, while the outer barometric pressure changes.
When barometric pressure falls, the higher pressure inside the jar makes the balloon bulge and the arrow drop. Unsettled weather is approaching.
When barometric pressure rises, the lower pressure inside the jar causes the balloon to sink and the arrow to rise. Fair weather is on its way!
Originally published in the June/July 2013 issue of FamilyFun magazine.