Air pressure can tell us what kind of weather to expect. A sudden drop
in pressure usually brings stormy weather while a rise means good weather.
Test this yourself with a barometer.
You will need:
Pencil
Scissors
Tape
Marking pen
Shoe box
Thread
Paper fastener
Thin wooden stick
Long piece of spaghetti
Flexible plastic bottle with cap
Directions:
Squeeze the air out of the bottle. Twist on the cap so that the bottle
stays flat.
Use the pencil to make a small hole in the side of the box and a hole in
each end. (Side hole should be halfway down the box)
Lay the flattened bottle in the box. Then push the stick through the holes
in the box ends. (Hold the bottle in place with crushed paper, if necessary.
Knot the thread around the spaghetti. Put the paper fastener tabs around
the spaghetti and through the hole in the box. (The spaghetti acts
as a pointer. It should hang level and move up and down easily.)
Gently pull the thread over the stick and tape it to the flattened bottle.
Draw a scale on the box. Mark the pointer's starting position with a dot.
Your barometer is now complete. The pointer moves up as air pressure rises
and down as air pressure falls. (Rising air pressure squeezes the bottle,
flattening it even more. This pulls on the thread and raises the pointer.
Falling air pressure lets the bottle expand slightly. The thread goes
slack and the pointer drops.)
Keep the barometer inside, out of the sun and away from direct heat.