Fundamental physical constants

The fundamental physical constants of the Standard Model and their possible change on the cosmological time scale are discussed. The Grand Unification of the strong, electromagnetic and weak interactions implies a relation between the time varying fine structure constant $\alpha$ and the QCD scale $\Lambda_c$. The astrophysically measured change of about $10^{-15}$/year in $\alpha$ causes a change of at least $10^{-15}$/year in $\Lambda_c$. The quantum optics experiment at MPQ Münich to test the time variation of $\Lambda_c$ is discussed.