THE NEWTONIAN GRAVITATIONAL CONSTANT - RECENT MEASUREMENTS AND RELATED STUDIES

Improvements in our knowledge of the absolute value of the Newtonian g ravitational constant, G, have come very slowly over the years. Most o ther constants of nature are known (and some even predictable) to part s per billion, or parts per million at worst. However, G stands myster iously alone, its history being that of a quantity which is extremely difficult to measure and which remains virtually isolated from the the oretical structure of the rest of physics. Several attempts aimed at c hanging this situation are now underway, but the most recent experimen tal results have once again produced conflicting values of G and, in s pite of some progress and much interest, there remains to date no univ ersally accepted way of predicting its absolute value. The review will assess the role of G in physics, examine the status of attempts to de rive its value and provide an overview of the experimental efforts tha t are directed at increasing the accuracy of its determination. Regard ing the latter, emphasis will be placed on describing the instrumentat ional aspects of the experimental work. Related topics that are also d iscussed include the search for temporal variation of G and recent inv estigations of possible anomalous gravitational effects that lie outsi de of presently accepted theories.