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# Measure the Effectiveness of Homemade Barometers in Predicting Weather

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Source:
Author: Janice VanCleave

Category: Earth Science—Meteorology

Project Idea by: Emily Frazier

The atmosphere is the blanket of gas surrounding a celestial body. Atmospheric pressure is the measure of the pressure that the atmosphere exerts on surfaces. Since Earth's atmosphere is composed of a mixture of gases commonly called air, atmospheric pressure is often called air pressure. Atmospheric pressure is measured with an instrument called a barometer; thus, atmospheric pressure is also called barometric pressure.

Changes in atmospheric pressure can be used to predict weather (the condition of the atmosphere). An increase in pressure is an indication of upcoming fair weather, and a decrease in pressure is an indication of upcoming stormy weather. A project question might be, "How effective are homemade barometers in predicting weather?"

Design and construct a barometer. One type of homemade barometer can be made by covering the open end of a can with plastic wrap and securing it with a rubber band. Then glue the end of a 4-inch (10-cm) piece of straw to the center of the plastic. When the atmospheric pressure is high, it pushes against the plastic covering, causing it to curve into the can. This makes the free end of the straw point up. When the pressure is low, the plastic puffs up and the straw points down.

Use your homemade barometer to measure the atmospheric pressure at different times of the day each day for 1 or more weeks. Using the daily barometric measurements, predict upcoming weather. Record the prediction from national weather reported on TV, on the radio, or in a newspaper. Compare these predictions with the ones you make from your barometer measurements. Also record the actual weather for each predicted period.

Independent Variable: Barometric measurements

Dependent Variable: Weather predictions

Controlled Variables: Time of measurements, location of measurements

Control: Barometric measurements from TV, radio, or newspaper

### Other Questions to Explore

1. How do atmospheric pressure changes affect cloud formation
2. What effect do atmospheric pressure changes have on wind speed? Direction?