This book is about the 4-dimensional space-time of our universe. From nothing more than the spinor algebras, we derive the existence and nature of our space-time. We explain why our space-time is 4-dimensional, why is has the distance function it has, why we have two types of 2-dimensional angles in our 4-dimensional space-time, and why we find intrinsic curvature in our space-time. We also derive tensor calculus, general relativity, and Riemann geometry from the spinor algebras. We also see classical electromagnetism emerge alongside general relativity. This book is a very easy and clearly presented introduction to tensor calculus. It is suitable to be read prior to, during, or after a course on general relativity and is a necessary supplement to that course.