Atmosphere (unit) facts for kids
The standard atmosphere (often shortened to atm) is a way to measure pressure, especially the pressure of air. Think of it as the normal air pressure you'd feel at sea level, which is the average height of the ocean's surface. Scientists and engineers used this unit for a long time to have a common reference point.
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What is Pressure?
Pressure is a force pushing on a surface. Imagine pushing your hand against a wall. The force you apply spread over the area of your hand is pressure. In the air, tiny air particles are always moving and bumping into things. This constant bumping creates air pressure.
Air Pressure Around Us
You might not feel it, but the air all around you is pushing on everything. This is called atmospheric pressure. It's why your ears might pop when you go up a mountain or fly in an airplane. The standard atmosphere unit was created to describe a specific amount of this air pressure.
The Standard Atmosphere Unit
The standard atmosphere (atm) was a very important unit. It helped scientists and engineers talk about pressure in a consistent way. It was defined as exactly 101,325 Pascals (Pa). A Pascal is another unit for measuring pressure.
Why Was It Defined?
Having a "standard" unit like the atm was useful for many reasons.
- Science experiments: It helped scientists compare results from different places.
- Engineering: Engineers could design machines or buildings knowing the typical air pressure they would face.
- Weather forecasting: Meteorologists use pressure to predict weather changes.
How Much is 101,325 Pascals?
To give you an idea, 101,325 Pascals is roughly the pressure exerted by a column of water about 10.3 meters (33.8 feet) high. Or, it's about the pressure of 1 kilogram (2.2 pounds) pressing down on every square centimeter (0.15 square inches) of surface.
Changes in Pressure Measurement
Over time, new ways to measure pressure became popular. Since 1982, the standard atmosphere unit has mostly been replaced by another unit called the bar.
What is a Bar?
A bar is a unit of pressure that is equal to exactly 100,000 Pascals (105 Pa). This makes it a bit simpler to work with in some calculations because it's a round number in Pascals.
Why the Change?
The change from atm to bar was part of a move towards using simpler, more standardized units in science. Even though the bar is now preferred, the use of both the standard atmosphere and the bar is generally discouraged in modern scientific work. Scientists often prefer to use Pascals directly, or other related units like kilopascals (kPa), which are 1,000 Pascals.
See also
In Spanish: Atmósfera (unidad) para niños
