A barometer is used to measure the changes in air pressure. Air pressure varies across different parts of the Earth’s surface, and these differences cause winds. Air moves from an area of high pressure, or an anticyclone, to an area of low pressure, or a depression. Depressions are usually associated with worsening weather conditions and rain. In a mercury barometer the air pressure pushes down on the mercury, which is forced up the barometer to give an accurate reading.
Air pressure is greatest at sea level, where it amounts to 14.7 pounds a square inch. It is greatest there because that is the bottom of the atmosphere. At highest altitudes the pressure is less.
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Fact File: The higher we go the less air pressure there is. This is the reason that space suits and the cabins of high-flying planes are pressurized. They are designed to maintain the air pressure our bodies must have. |
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