Rick Sobie wrote:

"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....

You can test this a number of ways
o astronomical observation involving motions of heavenly bodies
o replicate Cavendish experiments
o slip on the ice
o jump off a cliff