  In these lectures I discuss cosmological phase transitions with the goal of
establishing the possibility of observational consequences. I argue that the
{\em only} phase transition amenable of experimental study within the
foreseeable future is that predicted by QCD and discuss some of the potential
observational cosmological consequences associated with this phase
transition(s). I describe the experimental effort to study the QCD phase
transition(s) at RHIC and SPS and summarize some of the recent experimental
results. The possibility of novel phases of QCD in the core of pulsars is
discussed along with the suggested observational consequences. A brief review
of standard big bang cosmology as well as the astrophysics of compact stars
sets the stage for understanding the observational cosmological and
astrophysical consequences of phase transitions in the standard model.
