The determination of a precise value for the gravitational constant (G) proved a frustrating, but fruitful, exercise for scientists since the constant was first described by English physicist Sir Isaac Newton (1642-1727) in his influential 1687 work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy). In many ways as enigmatic as mathematicians' search for a proof to Fermat's last theorem (proved only in the last decade of the twentieth century), the determination of an exact value of the gravitational constant has eluded physicists for more than 300 years. The quest for "G" provides a continuing challenge to the experimental ingenuity of physicists and often spurs new generations of physicists to recapture the inventiveness and delicacy of measurement first embodied in the elegant experiments conducted by English physicist Henry Cavendish (1731-1810).
In Principia Newton put forth a grand synthesis of theory regarding the physical universe. According to Newtonian theory, the universe was bound together by the mutual gravitational attraction of its constituent particles. With regard to gravity, Newton formulated that the gravitational attraction between two bodies was directly proportional to the masses, and inversely proportional to the square of the distance between the masses. Accordingly, if one doubled a mass, one would double the gravitational attraction; if one doubled the distance between masses, one would reduce the gravitational attraction to one-fourth of its former value. What was missing from Newton's formulation, however, was a value for a gravitational constant that would accurately translate these fundamental qualitative relationships into experimentally verifiable numbers. more