  Astrophysical indications that the fine structure constant is time dependent
are discussed in the framework of grand unification models. 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 case in which the time variation of the
electromagnetic coupling constant 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. Possible
implications for baryogenesis are discussed.
