  Astrophysical indications that the fine structure constant has undergone a
small time variation during the cosmological evolution are discussed within the
framework of the standard model of the electroweak and strong interactions and
of grand unification. A variation of the electromagnetic coupling constant
could either be generated by a corresponding time variation of the unified
coupling constant or by a time variation of the unification scale, or by both.
The various possibilities, differing substantially in their implications for
the variation of how energy physics parameters like the nuclear mass scale, are
discussed. The case in which the variation is caused by a time variation of the
unification scale is of special interest. It is supported in addition by recent
hints towards a time change of the proton- electron mass ratio.
