|How does the Sun have a gravitational force?
Doesn't gravity depend on an atmosphere?|
Actually, gravitational force does not depend on
an atmosphere at all. All things that have mass
enact a gravitational force on all other things
with mass around them. Perhaps you are imagining
being out in open space and being able to float.
The reason that you can float in open space is
that you are sufficiently far away from big things
like the sun and the earth that would otherwise
pull you in. The gravitational force that is
exerted by an object like the sun or a planet (or
anything) decreases fast with distance. So as you
move far away, you can't feel the gravity pulling
you in anymore.
So in short, gravity exists by itself--even in
a vacuum. But on an interesting side note,
although gravity doesn't depend on the atmosphere,
the atmosphere does depend on gravity. Gravity is
actually the force that keeps gaseous molecules
close to the surface of planets and that's why
planets have atmospheres!
Not at all, the gravitational force between two
objects depends on the amount of mass both objects
have, and the distance between them. The larger
the masses, the larger the force, and the larger
the distance, the smaller the force. The Sun has a
mass of about 333,000 times the mass of the Earth!
So the Sun and the Earth both feel the same amount
of gravitational force pushing them toward each
other, but the Earth is affected way more by the
force than the Sun is, because the Earth has much
less mass. Atmosphere has nothing to do with it,
although if you're in space outside the Earth's
atmosphere, you're definitely farther from the
Earth than if you were on the ground, so you would
feel less gravitational force from the Earth.
No, gravity does not depend on an atmosphere.
Gravity creates atmospheres, by holding gas close
to the surface of planets (or stars), but
atmospheres are not needed for gravity. The movies
that you have seen that have things floating in
space until atmosphere is added are wrong (yes, I
have seen them).
Actually, gravity doesn't have anything to do
with the atmosphere. Everything in the universe
experiences a gravitational force from every other
thing in the universe. The force gets weaker as
you get farther away so we only usually feel the
force from the earth. This was first theorized by
Newton in the late 1600's and was proved by over a
hundred years later by Henry Cavendish. Cavendish
discovered that even two ordinary lumps of metal
attract each other (but only very slightly).
Click Here to return to the search form.
Copyright © 2015 The Regents of the University of California,
All Rights Reserved.