Cosmological models - in which universe do we live

A general discussion of the present state of cosmological models is introduced with a brief presentation of the expanding universe theory, the red shift and Hubble's Law. Hubble's Constant lies between 30 and 105 km/sec/Mpc, and a value of 55 km/sec/Mpc is assumed in this article. The arguments for the big bang and steady state theories are presented and the reasons for the present acceptance of the former given. Friedmann models are briefly discussed and 'universe density', rho, and 'space curvature',k, and the 'cosmological constant', Λ, are presented. These are shown on the Stabell-Refsdal diagram and the density parameter, sigma0, and the retardation parameter, q0, are related to Hubble's Constant. These parameters are then discussed and their values restricted such that the part of the Stabell-Refsdal diagram which is of interest may be defined. (JIW)