Weather Station, part 1: Barometer

Now that the boys have learned about how much force air pressure can exert, we will be studying how air pressure affects weather. To do this, we made a homemade barometer, an instrument that measures the change in air pressure.

To make one, you will need a round balloon, wide-mouthed glass jar, rubber band, plastic drinking straw, tape and an index card.

Cut the neck off the balloon. Stretch the balloon around the jar, pulling the end of the balloon off to the side so the surface is flat. Wrap the rubber band around the balloon and jar to keep the balloon from slipping.

Cut one end of the straw to form a point. With a small piece of tape, attach the other end of the straw to the center of the balloon. You have made a barometer!

Tape the index card to the wall next to the barometer. The straw should come to about the center of the straw. Make a mark where the straw points, and write the date next to the mark. Compare where the mark is to where the straw points on other days.  Does it change?

What does the changes mean?

Greater air pressure will make the straw rise as the balloon pushes downward. If the air pressure is consistently rising over several days, you can predict that a high-pressure system is on the way, bringing fair skies.