ABSTRACT
General relativity brought in a huge conceptual change regarding the nature of gravitation. It introduced a sophisticated model for possible space-times, required it to be dynamical and provided a specific equation determining spacetimes appropriate in various physical contexts. Within this model, the motion of test bodies under Newtonian gravitational force is understood as geodesics of corresponding space-time. This forms the basis for the solar system tests of general relativity. As we saw in the discussion of wave motion in geometrical optics approximation, light too responds to gravity following light-like geodesics. Apart from these test bodies implications, general relativity impacts compact stars and their stability, strongly suggests new types of objects called black holes, points to the possibility of a ‘singular’ beginning for an expanding universe and makes a brand new prediction of gravitational waves. This chapter is arranged according to these different implications of the theory.
