A scale covariant modification of Newton's second law is combined with Bohr's model of the atom. If we suppose that physical "constants" have varied in a way consistent with this theory, then it leads naturally to an explanation of the red shifts in the light from distant galaxies. The model is offered as an example of how not only the "constants," but also the equations themselves are suspect in any endeavor to find the true laws of physics. In the second part of the paper, some limits on the variability of "constants" based on data from the Oklo reactor are examined. It is found that limits which have been published in the technical literature are more imaginary than real.