ABSTRACT
Newton’s theory of the gravitational interaction constitutes a major landmark in the evolution of scientific thought in Europe. In his magnum opus, Principia Mathematica Philosophise Naturalis, Newton laid the foundations of Theoretical Mechanics and put forward his revolutionary ideas about the motion of masses under the influence of their mutual gravitational pull. Einstein’s deep insight into the nature of gravitational phenomena led him to formulate his Principle of Equivalence, whereupon he was further led to conclude that gravitation shows as changes in the geometry of space-time, the changes being linked to the distribution of mass and energy. The Equivalence Principle implies that gravitational effects can be traced to geometry in space-time. Geometry is expressed in terms of coordinates, of course, but the choice of them remains arbitrary. The chapter provides some of the possible sources of gravitational waves, along with their estimated amplitude on arrival in Earth, and their believed event rate.
