A tug from the earth
Imagine floating through the air, standing on the ceiling, or leaping
upstairs in one big bound! An astronaut traveling through space can do
all of these things. But on the earth, you can’t.
You can’t do these things on earth because a special kind of force tugs
on you and keeps your feet on the floor. This force is called gravity
[(grav]{.smallcaps} uh tee). Gravity is the pull that makes things slide
or fall or roll downward.
As long as you are on the earth, the tug of the earth’s gravity pulls on
you and everything else. When you let go of a ball, it falls to the
ground. When you jump, you come back down to the earth instead of flying
into the air.
A spaceship can travel beyond the reach of the earth’s gravity. So on a
space flight away from the earth, you’ll reach a place where there is no
gravity—the earth isn’t tugging on you at all.
What will happen then? You’ll float, unless you hang on! Anything you
\”drop” will float in the air when you let go of it. And if you jump,
you won’t come down—you’ll hit your head on the ceiling, instead.
This astronaut is too far from earth to feel the pull of gravity. So, on
a “walk” outside the spaceship, he floats instead of falling. The tube
is attached to the ship to keep him from floating away.
