Why is gravity strongest at the center of the Mass ?

On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert

G=EMC^2 Glazier wrote:
On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert

not sure what your driving at G, but i've been wondering.....

How does gravity change below the surface of the earth? In outer
space, a person is weightless or zero G's, on earth's surface gravity
is 1 G. I assume somewhere like 50 or 100 miles up, its like 1/2 G.
(1) say you dig a hole down toward the center of the earth and weigh
yourself 2,000 miles down. Do you weigh more or less? It seems you
would
weigh less as a good portion of earths mass is now above you and that
much less is below you.
(2) say you hollow out 1 mile diameter spherical cavity in the center
of the earth, would you float to the center of this cavity and be
suspended in "midair"? And, if so, would you again be weightless? and
would you be able to walk around "upside down" on the surface of this
hollowed out sphere?

"G=EMC^2 Glazier" wrote in message
...
On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert


If you think of gravity as radial lines emanating from the center of the
Earth, then a fixed amount of these imaginary lines will intersect a human
body, at any given point on the Earth's surface, giving your body a specific
weight, based on the components of your body and their combined atomic mass.
Since these lines are actually fanning out, 1000 miles above the surface
much less of them will intersect your body, thus reducing your body weight..
Conversely, if you could go 1000 miles below the surface, there would be
more lines intercepting your body than on the surface and thus increasing
your weight.

wrote:
G=EMC^2 Glazier wrote:
On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert

not sure what your driving at G, but i've been wondering.....

How does gravity change below the surface of the earth? In outer
space, a person is weightless or zero G's, on earth's surface gravity
is 1 G. I assume somewhere like 50 or 100 miles up, its like 1/2 G.


Gravity does no decrease that quickly, but with the inverse of the
square of the distance from the Earth's center. Those in space feel
weightless either because they are falling, or because they are
orbiting. When orbiting they feel weightless for the same reason a cat
you are swinging in a bucket feels nearly weightless at the top of the
swing.


(1) say you dig a hole down toward the center of the earth and weigh
yourself 2,000 miles down. Do you weigh more or less? It seems you
would
weigh less as a good portion of earths mass is now above you and that
much less is below you.


Yes, you would weigh less. But descending in mines near the Earth's
surface you weigh still more, because the density of the Earth's crust
is low compared to the density of the layers further down.


(2) say you hollow out 1 mile diameter spherical cavity in the center
of the earth, would you float to the center of this cavity and be
suspended in "midair"? And, if so, would you again be weightless? and
would you be able to walk around "upside down" on the surface of this
hollowed out sphere?


You should be weightless anywhere in the hollowed out sphere. There is
nothing to pull you to the center, and the gravity from all the layers
about you cancel each other out. There would be nothing to hold you to
the surface either.

Double-A

"Hagar" wrote in message
...

"G=EMC^2 Glazier" wrote in message
...
On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert


If you think of gravity as radial lines emanating from the center of the
Earth, then a fixed amount of these imaginary lines will intersect a human
body, at any given point on the Earth's surface, giving your body a specific
weight, based on the components of your body and their combined atomic mass.
Since these lines are actually fanning out, 1000 miles above the surface
much less of them will intersect your body, thus reducing your body weight..
Conversely, if you could go 1000 miles below the surface, there would be
more lines intercepting your body than on the surface and thus increasing
your weight.

Bert's wrong again, as usual. If the Earth were composed of a
uniform density material then he would have been correct, but
it is not.

The Earth's makeup is not uniform; there are distinct layers of
differing density and thickness. Since the gravitational
potential depends upon both mass and distance, a graph of the
acceleration due to gravity with respect to radial distance from
the center is not a simple smooth curve, and in fact it peaks at
about 1.08 g at a radius of about 3600 km (in what is refered
to as the D'' layer sandwiched between the Outer Core and the
Lower Mantle). There is a second, smaller peak of 1.01 g in the
Transistion Region just below the Upper Mantle around R = 5860km.

wrote in message
ups.com...

(2) say you hollow out 1 mile diameter spherical cavity in the center
of the earth, would you float to the center of this cavity and be
suspended in "midair"? And, if so, would you again be weightless? and
would you be able to walk around "upside down" on the surface of this
hollowed out sphere?

You'd float freely, but you wouldn't be drawn to the center.
Net gravitatinal force would be nil throughout the sphere.

wrote:
G=EMC^2 Glazier wrote:
On the Earth's surface gravity is the strongest. Strongest as
measured by objects not sitting on the earth's surface? Go figure Bert

not sure what your driving at G, but i've been wondering.....

How does gravity change below the surface of the earth? In outer
space, a person is weightless or zero G's, on earth's surface gravity
is 1 G. I assume somewhere like 50 or 100 miles up, its like 1/2 G.
(1) say you dig a hole down toward the center of the earth and weigh
yourself 2,000 miles down. Do you weigh more or less? It seems you
would
weigh less as a good portion of earths mass is now above you and that
much less is below you.

An answer from the art and science of surveying: Surveyors must be
careful of the 'local vertical' when shooting a bearing. Nearby masses
such as mountains, cliffs or even igneous intrusions underground can
throw off the 'vertical' by a statistically significant amount.

Yes, if you were to tunnel downward 2000 miles, the mass of the earth
above you would exert a gravitational pull in opposition to the mass
below you, and thereby decrease your weight (not mass, weight).


(2) say you hollow out 1 mile diameter spherical cavity in the center
of the earth, would you float to the center of this cavity and be
suspended in "midair"?

Yes, but it would most likely not be stable. Eventually the mass one
one side or the other would win and you would fall for half a mile
before you smacked into the inside of the sphere. Better make it 10
meters in diameter. :-) As a side note, I hear sprained wrists are an
occupational hazard in microgravity environments, because the astronaut
tends to push off too hard, until they get their 'space legs'.

... And, if so, would you again be weightless?

Essentially, yes.

... and
would you be able to walk around "upside down" on the surface of this
hollowed out sphere?

Not very easily. You'd be able to push off and fall across the 1 mile
sphere pretty easily. Probably just flexing your calf muscles would do
it.

Johnny I Poorly posted my thought. However you do have to measure the
gravity force from the center of the Sun to the Earth's center for it to
be accurate.,and not from surface to surface that seems more logical.
You would float at the exact center of the Earth. That is easy to
appreciate using Quantum gravity since its a particle force for
gravity.. Using again quantum gravity inside a hollow object you would
be attracted to the inner wall,for that is where the particles are.
Reality is gravity sees to it that objects are not hollow..by pulling
every thing to its center. We can thank electrons for pushing back so
we do not fall to the center. Bert PS The point of gravity balance
between Earth and Sun is inside the Sun. Earth and Sun about 8 thousand
miles from the Moon's center(I think) See oc I said pushing just for
you Go figure Bert

If you were inside the hollow ball and it was accelerating you would be
able to walk at the back part of the ball (elevator effect) If the ball
was spinning you would be pressed against the wall There is that Revere
Beach ride Ooops I just remembered its name It was called the
"Tornado" What a memory I have. Here you see both accelerating
motion,and curved(spin) motion equivalent to gravity. Thought just
jumped in Would a ruler the lies along the direction of the ride's
motion foreshorten? I say yes. Does the fact that pi is a an endless
fraction,and not say exactly Two times pi give us only an approximation
how many turns around the ride does say in 10,000 years. This could
answer a lot of stuff. Seems that tornado ride,and my little gyro stick
in my mind over all those years. They do relate. They both make you
think gravity Go figure Bert

Floating at Earth's center,but we can't leave out the rest of the
universe. Mach would hate us if we did. Bert