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Atmospheric Flight
Grades 5-8 Reading
Introduction
An airplane flying through the sky is a very exciting sight:
hearing the roar of the engines as it soars overhead; watching as it rolls
and turns across the sky; wondering how it is possible for such a large,
heavy object to appear lighter than air. Although there are a lot of things
that work together to get an airplane to fly, the most basic element needed
is air, specifically, molecules of air. To fly, the airplane must pass through
the air. Although the air is not visible, it is made up of millions of tiny
molecules that move and push against each other. These particles of air
take up space. These molecules have volume. They are also made up of matter
so they have mass, too. Air molecules can be squeezed into a tube where
they are tightly compressed together. They can also expand and spread out
across a wide area. They also have weight. Some molecules actually weigh
more than others. For example, scientists discovered some time ago that
hydrogen and helium are lightweight gas molecules while nitrogen and carbon
dioxide molecules are heavyweights. Because these molecules are made up
of matter, have volume and have mass, they can exert a tremendous amount
of pressure and force. You can feel the air pushing against you when the
wind blows. As you move through a room, you push against the air molecules,
moving them around. Knowing that air is not empty space, but actually made
up of "stuff" like air molecules, led to some very important discoveries.
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