|Why the sun does not fall on the earth?
|Question Date: 2014-08-30|
The earth and the sun are about 93,000,000 miles
apart. If the earth did not orbit the sun and
became stationary (this can't happen, but if it
did) the sun and earth would attract each other
and the earth, being smaller, would fall into the
sun. Otherwise, it is because earth has a lot of
If the sun were to disappear, the earth would
fly away straight rather than continuing to circle
the sun. So, the earth has two main forces:
inertia, to keep moving straight, and the
gravity, to pull it to the sun. It moves in an
average of the two directions, as in this image,
and moves in a circle around the sun.
here to watch
Everything we see on earth involving gravity is
misleading when it comes to the solar system. You
see, everything on Earth---the air, the rocks
and you and I are attracted towards the CENTER of
A basic law of nature says that any two objects
of mass M and mass m are attracted
to each other with a force that is equal to the
product of the masses divided by the distance
between them squared, that is
So if we consider YOU and the Earth we can pretend
that the mass of Earth is concentrated at the
center... so the R is the radius of Earth (since
you are on the surface).
Now we can think about earth and Sun. The Earth
is indeed attracted to the SUN. IF WE COULD
STOP THE EARTH’S motion and then let go, indeed
the earth WOULD accelerate and fall into the
sun! The reason why it does not is because of
Newton’s first law of motion.
This first Newton’s law of motion says that
if a body is in motion, it remains in motion
unless acted upon by a force. So billions of
years ago, the cloud of gas and dust from which
the earth is made was in circular motion around
the sun, in other words, the protoearth
had a velocity INITIALLY that was tangential to
its current orbit. This inertia remains today
because there is no way the sun can remove the
energy directed TANGENTIAL to the sun-Earth line.
I realize this explanation may be confusing,
but do not feel bad about it, it took humanity
thousands of years to figure this out.
You might want to find a simple book on
NEWTON’S Laws, this book will help explain what I
have written above. These are very deep and
profound concepts, it takes some years to fully
understand this, but it is never too soon to start
The sun is so much bigger than the Earth that a
better question is "why does the Earth not fall
into the sun?"
The answer is something called
'momentum' - the property of moving objects
that causes them to continue moving. The Earth is
in orbit around the sun; without the sun's
gravity, the Earth would coast off into space, but
because the Earth is moving and is moving as fast
as it is, it can't just fall into the sun. So,
instead, it falls around the sun, i.e. an orbit.
The sun and the earth are both in space, where
gravity doesn't look quite the same as it does
here on earth. The gravity of a planet or sun is
to the middle of the planet -- we're on the
surface of the earth so everything falls down.
But in space there isn't an up or down!
When we say that the earth orbits around the sun,
that doesn't mean that it's above or below it, but
that it's going in a circle around it. The earth
is attracted to the sun and the sun to the earth,
but we're so far away that the gravity force that
attracts us isn't strong enough for the sun to
come close enough to actually fall on us (thank
Good question! All massive objects in our
universe are attracted to each other through a
force known as gravity. If gravity were the
only force acting between the sun and earth, the
two bodies would indeed collapse on one another.
Therefore, there must be other forces acting on
this system. Remember that the earth, and all the
other planets in our solar system, revolve around
the sun. Because the earth is in a rotational
orbit, there is another force acting on the
planet. This force is known as centrifugal
force. The direction of the centrifugal force
on the earth is opposite the direction of the
gravitational force (see the diagram below), so it
prevents the sun and earth form collapsing into
Centrifugal force acts on a rotating object in
a direction opposite the axis of rotation. Imagine
that you have a tennis ball tied to a string. If
you swing the tennis ball on the string around in
a circle, you would feel the ball tugging on the
string. That is the centrifugal force on the ball.
It is counteracted by tension in the string that
you are holding. In this example, the tension
force in the string is like the gravitational
force between the earth and the sun. The ball
doesn't get closer or farther from your hand. If
you suddenly cut the string, the ball would go
flying away, but that wont happen to the earth
because of the sun's gravity.
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