A drop in barometric pressure means a storm is coming.
We tested the theory that increased (air) pressure will cause a rise in the water level by placing our hands in a pan of water. Exerting pressure on the water caused it to rise. We're hoping the same thing happens with our barometers!
- When you fitted the balloon over the glass, you captured air under a certain pressure. The balloon now indicates changes in the atmospheric pressure, that is, the pressure of the air around you. Higher air pressure pushes the balloon into the jar and makes the straw go up. Conversely, the air inside the jar expands against lower pressure and will bulge the balloon, moving the straw down. The straw makes it easier to see the motions of the balloon.
- As the straw moves up with higher air pressure, the days should be sunnier. As the straw lowers, the skies may be looking gray and you should expect cloudy or rainy weather on the way.