Lecture 4 on the Spatial-Time Dimension has been added. Lecture 4 argues that the geometry of the universe is not a three-dimensional non-Euclidean space as perceived by Einstein. Rather, it is a four-dimensional Euclidean space. The fourth dimension is called the Spatial-Time dimension that unifies space and time (i.e. a lightyear in distance is a year back in time. This lecture also summarizes the main tenants of The Theory of Time. Length 55:03