"Sam Wormley" wrote in message ...
Rick Sobie wrote:

Lets suppose, that the moon, was a Dyson sphere, and its power unit failed,
and its orbit began to decay, then it would hit the earth.


Ref: http://scienceworld.wolfram.com/physics/Gravity.html
Ref: Hartle, "Gravity: An Introduction to Einstein's General Relativity", Addison
Wesley (2003)

"A few properties of the gravitational interaction that help explain when
gravity is important can already be seen from the gravitational force law

F_grav = G m_1 m_2 / r_12^2

o Gravity is a universal interaction in Newtonian theory between all mass, and,
since E = mc^2, in relativistic gravity between all forms of energy.

o Gravity is unscreened. There are no negative gravitational charges to cancel
positive ones, and therefore it is not possible to shield (screen) the gravitational
interaction. Gravity is always attractive.


Excuse me?

Tell me how gravity is an attractive force, when mass bends space-time
like a rubber sheet with a ball bearing on it. That is the common explanation of GR.

Is that what you mean by attractive gravity? That mass on one side of the universe,
50 billion light years across, can affect mass on the other side,
when the universe is only 15 billion years old?

http://www.americanantigravity.com/hutchison.html

this is gravity ...
http://www.members.shaw.ca/rsobie/Time_travel.txt

If your explanation was correct, Ranger 5 would not have missed the moon by 450 miles
and the Beagle 2 would have landed.


o Gravity is a long-range interaction. The Newtonian force law ia a 1/r^2
interaction. There is no length scale that sets a range for gravitational
interactions as there is for the strong and weak interactions.

o Gravity is the weakest of the four fundamental interactions acting between
individual elementary particles at accessible energy scales. The ratio of
the gravitational attraction to the electromagnetic repulsion between two
protons separated by a distance r is

F_grav G m_p^2 / r^2 G m_p^2
-------- = -------------------- = ------------- ~ 10^-36
F_elec e^2 / (4 pi e_0 r^2) (e^2/4pi e_0)

where m_p is the mass of the proton and e is its charge.

These four facts explain a great deal about the role gravity plays in physical
phenomena. They explain, for example, why, although it is the weakest force,
gravity governs the organization of the universe on the largest distance
scales of astrophysics and cosmology. These distance scales are far beyond
the subatomic ranges of the strong and the weak interactions. Electromagnetic
interactions COULD be long range were there any large-scale objects with net
electric charge. But the universe is electrically neutral, and electromagnetic
forces are so much stronger than gravitational forces that any large-scale net
charge is quickly neutralized. Gravity is left to govern the structure of the
universe on the largest scales.