From the book Thinking Physics:
Suppose the moon had a negative charge. Then it would exert a repelling force on electrons near it. But the gravitational force of the moon exerts an attracting force on the electron. Suppose the electron is one mile above the lunar surface and the attraction exactly balances the repulsion, so the electron floats.
Next, suppose the same electron was two miles above the moon. At the greater distance
c) the gravity would still balance the electrostatic force, so the electron would float
If dust could float, due to an electrostatic charge, one inch above the lunar surface, it could float at any height and so would float right off the moon! In fact, it is impossible to suspend or levitate an object by any combination of STATIC electric, gravitational or magnetic force fields because each obeys the inverse square law.
I don't understand, how does the inverse square law justifies this impossibility?