Gravity is an attractive force between
objects. The strength of the attraction
depends on how close the objects are to each
other, and how big the objects are. So, objects
that are close to each other or large attract each
other more than objects that are far apart or
The reason we don’t float away from the earth
is that the earth is both large and close. So, if
you jump, the force of gravity pulls you down.
However, if you were able to jump incredibly high
(or if you were in a rocket ship) you could get
far enough from the earth that the attractive
force pulling you back would be too weak, and you
would continue into space.
The atmosphere doesn’t prevent us from floating
away, but it does allow us to live. The atmosphere
is gas trapped near the earth by gravity, just
like we are. We need the atmosphere to live,
because it supplies us the air we breathe, and
helps keep the earth at a good temperature for
life. Without the atmosphere, not only would we
not be able to breathe, but the average
temperature of the earth would drop to below the
freezing point of water and most life on earth
would quickly die.
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