QUESTION:
What is the difference between the Earth's gravitational pull and
Jupiter's gravitational pull?

ANSWER from Edna DeVore on November 3, 1995:
Gravity is one of the four fundamental forces in nature.  All
objects which have mass have gravity.

As you stand upon the Earth, you stand upon a terrestrial or rocky planet
which has a very thin layer of gas we call the atmosphere.  You are
continuously pulled toward the Earth's center by the planet's gravity, and
you also pull upon the planet.  Being much smaller (less massive) than the
Earth, your body does not exert much gravitational force upon the planet. You
do not fall to the center of the Earth because the surface of the planet
stops you about 6,378 km (average radius) from the center. Your "weight" is
actually a measure of the Earth's gravitational pull upon your mass.  When
you stand upon a scale, gravity causes your mass to press down upon a spring,
and that is registered as your weight.  Let's imagine that you weigh 50 kg
(about 110 lbs.).

Jupiter is very different than the Earth:  it is a giant globe of gases which
may have a rocky core.  When you see a photograph of Jupiter, you are
actually looking at the top of its atmosphere; you are looking at clouds.
Now, if you took your scale from the Earth, and could stand upon it at
Jupiter's cloud tops, you would find that your weight was about 2.54 times as
much--the gravitational pull of Jupiter is 2.54 times greater than the pull
of gravity at the surface of the Earth.  If you are a 50kg person, you now
weigh 127 kg (279 lbs) even though your mass has not changed.  You are simply
being pulled on by a greater force of gravity because Jupiter is so much more
massive than the Earth.

There is another problem with "standing on Jupiter."  If you were to try to
"stand" on this apparent surface you would be 71,398 miles (at the equator)
from the center of Juipter---that's over 11 times larger in radius than the
Earth!  First, you would be pulled down through these clouds toward an ocean
of liquid hydrogen.  As you splash down in the ocean, things begin to heat up
and the pressure increases.  At the bottom of the ocean, you would sink into
a deep layer of liquid metalic hydrogen, and finally encounter a rocky core
(if one exists) at 12,000-18,000 km from the center.  Bump!  Long before
this, the high temperature and pressures could have crushed you and your
space craft!

In specific terms, the Earth's gravitational pull is 9.8 meters per second
per second.  If you drop a ball from your hand, it accelerates at that rate.
Jupiter's gravitational pull is 2.54 times as great.  You do the math!

For more information on Jupiter, look at NASA's Online from Jupiter:
http://quest.arc.nasa.gov/jupiter.html

Edna DeVore
FOSTER Project