# Comment on time-variation of fundamental constants arXiv (Cornell University). Published: 2002-08-13. Preprint. 47 citations. ## Authors - M. J. Duff: h-index 77; 20,807 citations; corresponding author ## Topics - Cosmology and Gravitation Theories - Black Holes and Theoretical Physics - Noncommutative and Quantum Gravity Theories --- # Comment on time-variation of fundamental constants ## Abstract The possible time variation of dimensionless fundamental constants of nature, such as the fine-structure constant α, is a legitimate subject of physical enquiry. By contrast, the time variation of dimensional constants, such as h, c, G, e, k. . . , which are merely human constructs whose number and values differ from one choice of units to the next, has no operational meaning. To illustrate this, we refute a recent claim of Davies et al that black holes can discriminate between two contending theories of varying α, one with varying c and the other with varying e. In Appendix A we respond to criticisms by P. Davies and two Nature referees. In Appendix B we respond to remarks by Magueijo and by T. Davis. In Appendix C we critique recent claims by Copi, A. Davis and Krauss to hav