Quantum Physics-Motivated Measurement and Interpretation of the Newtonian Gravitational Constant

Abstract

One of the most easily recognized yet quantitatively elusive constants in all of physics is the Newtonian gravitational constant, G. Because the gravitational force is so weak and it cannot be shielded, the determination of the absolute value of G is very difficult and its various measured values are in poor agreement. This situation has often led to suggestions that G might be varying or that some new type of quantum-based physics might be revealing itself. Certain experiments have been designed specifically to explore these possibilities, and various of them will be discussed here. Also, because the experiments aimed at re-determining G are typically done with high precision, it is often possible to reliably analyze the results of a particular experiment in novel ways to see if new limits can be placed on other gravitational effects (eg., shielding, mass equivalence, etc.). Some examples of that class of work will be considered here, as well. Lastly, and from a much broader perspective, thepresence of G in the expressions for the Planck mass, length and time, the implications of spatial and temporal variation arising in multi-dimensional theories, and its ubiquity in cosmological models suggest some interesting physical scenarios in which the laws of quantum mechanics are applicable. A temperature-dependent G is one example, and this and others will be explored.