In this lecture Prof Susskind outlines the general structure of the course and the desire to teach the basics of modern cosmology. We will discuss what do we know now? We start with the basic big bang theory. Discuss the three possible versions of it from two different points of view, and then resolve to match them. We study cosmology from the perspective of geometry. This lecture discusses the idea of expanding space, and the concepts behind Hubble’s law. In this lecture we derive Hubble’s law from simple laws of cosmology. We begin with the idea of space. One-dimensional space. Not Space-time, just space. Good old x axis. We also discuss the metric of space.