I am an engineering researcher at the
University of California-Santa Barbara. Thank you
for your question “Does gravity prevent Earth from
flying away from the Sun OR flying into the Sun?”
The answer to your question is that gravity does
prevent the Earth from flying away from the sun.
The Earth travels through space at a very, very
fast speed. Several hundred years ago, a very
famous scientist named Sir Isaac Newton taught us
that an object moving at a certain speed will
continue at that speed in a straight line unless
some other force acts on the object. So this means
that, if there was no gravity between the earth
and the sun, and the Earth was traveling at its
current speed, then the Earth would shoot off into
space in a straight line. But since there is
always gravity, the earth is kept in a nice stable
orbit around the sun. The situation is the same as
if you take a string with a small weight attached
to the end of the string, and then you swing
string over your head in a circle like a
helicopter. In this case, you would be the sun,
the weight would be the earth, and the string
would be “gravity.” If, while you were swinging
the weight, you suddenly let go of the rope, then
the weight would fly off away from you into space.
This concept is illustrated in the link to an
image I have included below.
However, if the Earth were not moving at a very
fast velocity through space, and instead was just
standing still, then the sun’s gravity would pull
the Earth toward the sun, and the whole Earth
would be burned up by the sun (oh no!). But
thankfully, Earth is traveling very fast, and the
sun’s gravitational force directly balances Earths
velocity through space and keeps our planet in a
nice stable orbit.
I hope this helps with your question!
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