Phenomenological scaling laws relating the observed galactic dimensions tothe microscopic fundamental scales

It is shown that the order of magnitude of the characteristic observed radi i of typical galaxies can be inferred from the microscopic fundamental scal es through a phenomenological scaling law. Further scaling relations are de rived, which show that such a connection can equivalently be obtained eithe r by considering the nucleons as the elementary constituents of a galaxy, o r, as more common, by considering stars as its granular components.