Albert Einstein's theory of general relativity describes the effect of gravitation on the shape of space and the flow of time. But for more than four decades after its publication, the theory remained largely a curiosity for scientists; however accurate it seemed, Einstein's mathematical code - repr[...]

Here, one of the world's leading astrophysicists provides the first comprehensive and logically structured overview of the many ideas and discoveries pertaining to the supermassive black hole at the galactic center known as Sagittarius A*. By far the closest galactic nucleus in the universe, Sagitta[...]