Einstein's theory of gravity can be difficult to introduce at the undergraduate level, or for self-study. One way to ease its introduction is to construct intermediate theories between the previous successful theory of gravity, Newton's, and our modern theory, Einstein's general relativity. This textbook bridges the gap by merging Newtonian gravity and special relativity (by analogy with electricity and magnetism), a process that both builds intuition about general relativity, and indicates why it has the form that it does. This approach is used to motivate the structure of the full theory, as a nonlinear field equation governing a second rank tensor with geometric interpretation, and to understand its predictions by comparing it with the, often qualitatively correct, predictions of intermediate theories between Newton's and Einstein's. Suitable for a one-semester course at junior or senior level, this student-friendly approach builds on familiar undergraduate physics to illuminate the structure of general relativity.
