Question

Why is the earth gravity cannt be controlled?

Answer 1

it can be control by some other way .

Newtons equation for the gravitational attraction between two objects is
Force=G∗(Mass of 1st object)∗(Mass of 2ndobject)distance between their centers of mass2Force=G∗(Mass of 1st object)∗(Mass of 2ndobject)distance between their centers of mass2

G in this equation is a constant.  It is equal to
G=6.674∗10−11Newtons∗mkg2G=6.674∗10−11Newtons∗mkg2

The difficulty with controlling gravity  is that it is a very weak force.  Experiments to  demonstrate its effects have to be absolutely massive or incredibly sensitive. 

To  demonstrate how small this force is, consider the attraction between two one kilogram objects that are one meter apart.  This force is is 0.000000000067 Newtons.  That is  mind-bogglingly small.  Bright sunlight falling on the apparatus would  make a bigger force.  It is practically un-measurable.  
 
Why let that stop you though?  Lets play with some numbers. 

Assume I want to cancel out Earth's gravitational field so I can free-float my  laboratory to space.  I take Newton's equation and divide away the mass of my lab.  That leaves the gravitational field around my lab as G times Earth's mass divided by the distance to the center of the earth  squared.
G∗6∗1024kilograms(6400 kilometers)2G∗6∗1024kilograms(6400 kilometers)2

I  can cancel out this field if I put another earth sized mass 6400 km  away in the direction opposite of earth, and float my lab into space.

I don't happen to have an earth sized mass, what else could I do?
I could put a quarter-earth mass object at 3200 kilometers, half as far away.