The book presents seven fundamental concepts in spacetime physics mostly by following Hermann Minkowski's revolutionary ideas summarized in his 1908 lecture "Space and Time." These concepts are:  spacetime, inertial and accelerated motion in spacetime physics, the origin and nature of inertia in spacetime physics, relativistic mass, gravitation, gravitational waves, and black holes. They have been selected because they appear to be causing most misconceptions and confusion in spacetime physics. This second edition has been revised to include additional clarifications, more detailed elaboration of the arguments and also new material published in the interim.