In this lecture Prof Susskind discusses how the geometry of space gets measured. He presents the concept of “Big Omega” regarding the percentage of energy of different forms. Prof Susskind further reviews the FRW equations. He further discusses the era of cosmology where equation of state is mass dominated rather than radiation dominated. Prof Susskind discusses that Omega is the fraction of energy carried by the various components. We further discuss that the universe is flat, very big, very smooth and very homogeneous. Prof Susskind presents the idea that the primordial universe was not perfectly smooth. He further discusses the idea of primordial fluctuation when the Universe first became transparent, at the time of big bang. Prof Susskind discusses the process of gravitation’s inhomogeneity and its effect on mass clustering. He also discusses the conditional probability within the parameter space of various parameters having specific values. Prof Susskind further discusses that the cosmological constant is very small.