Are fundamental constants really constant

All the existing experimental evidence points quite clearly to constant values of both e, the electronic charge, and G, the gravitational constant. However, it is highly instructive to gain some appreciation of the large amount of effort, both theoretical and experimental, that has been expended in examining this issue over the past 30 years. Despite the accumulating experimental evidence, it remains difficult to dismiss the relationships first pointed out by Dirac, and no doubt his stimulating paper of 1937 will provoke continuing theoretical attempts to link the phenomena of electricity, gravitation and cosmology.