Comment on the Variation of Fundamental Constants
  It is argued by Duff that only the time variation of dimensionless constants of nature is a legitimate subject of enquiry, and that dimensional constants such as c, h-bar and G... are merely human constructs whose value has no operational meaning. We refute this claim and point out that such varying dimensional "constants" can have significant physical consequences for the universe that can be directly measured in experiments. Postulating that dimensional constants vary in time can significantly change the laws of physics. 
J.W. Moffat