The air around the baby food jar was compressed. This compressed air pushed harder on the baby food jar and caused the balloon on top of it to move downward. That caused the toothpick tip to move up registering the high pressure. The toothpick went down registering low pressure. Instead of the large jar which we pushed and pulled on, the actual pressure of the atmosphere will act upon the baby food jar barometer.
Meteorologists use a scientific tool or instrument called a barometer.
Galileo experimented with tubes of water and air pressure, but it was his student Torricelli who invented the first barometer in 1644. A falling barometer indicates a pressure drip and stormy weather to come. A rising barometer indicates fair weather is approaching. Relate Activity and Concept Think of a metaphor to help explain why air molecules move from high to low areas of pressure. For example, picture a crowded bus and an empty bus.