The value of g will be zero at infinite distances from the earth's surface . We know that g = (GM) / R² [G = gravitational constant , M = mass of the Earth] Here , no matter how high the value of R , the smallest value of g can be found. Only if the value of R is infinitely positive , then the value of g will be zero. For the same reason gravitational and gravitational ball scales are considered infinite. Source: Advanced Physics , Chapter 4 , Newtonian Mechanics.