Teleparallelism

Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Teleparallelism (also called distant parallelism and teleparallel gravity), was an attempt by Einstein to unify electromagnetism and gravity. The idea is to use a geometry with a pseudo-Riemannian metric of signature (3,1), vanishing curvature, and non-vanishing torsion, and to use tetrads, rather than the metric, as basic variables. Nowadays, people study teleparallelism purely as a theory of gravity without trying to unify it with electromagnetism.