Fun science project: make a barometer!

Have you ever heard of atmospheric pressure? Atmospheric pressure is the pressure in the air, and it varies depending on where you are on Earth. As you go higher into the sky where the air is thinner, the pressure decreases. Air pressure is measured using a device called a barometer. Here’s how you can make one at home.

Materials

• Scissors
• 1 birthday balloon
• 1 glass jar (Mason jar)
• 1 rubber band
• 1 straw
• Tape
• 1 sheet of paper
• Pencil

Assembly

Here’s how to put your barometer together:

1. Cut out the end of the balloon (the part you blow into).
2. Stretch the large piece of balloon over the opening of the jar and pull it tight.
3. Use the rubber band to secure the balloon to the jar.
4. Cut the straw to a length of about four inches and cut one end into a point.
5. Tape the straw horizontally to the balloon. It should stick out by an inch or two, and the pointed end should be on the outside.
6. Stick the sheet of paper to the wall in front of the point of the straw.
7. Draw a horizontal line on the sheet at the same height as the straw.

Explanation

The line you’ve just drawn will tell you whether the air pressure is high or low. When the air pressure rises, the straw will rise above the line. When the pressure falls, the tip of the straw will fall.

Typically, the pressure is high when the sun is shining outside. When the air pressure is low, you’ll probably see clouds or rain.

In the United States, atmospheric pressure is usually measured in millibars (mb). The normal value, at sea level, is 1013 mb.