In this chapter we saw how the general theory of relativity has changed our thinking about the nature of space and time.

We then saw how the ideas of space-time carry over to a theory of gravitation - general relativity. The interpretation of gravitational fields is that they alter the geometry of space-time, causing it to behave like that on a curved surface. The starting point for general relativity is the principle of equivalence, which tells us that inertial and gravitational masses are the same..

We saw that there are several effects of general relativity that can be tested. These include the advancement of the periastron of orbiting bodies, the bending of electromagnetic radiation, gravitational redshift and time dilation, and gravitational radiation.

We also saw how the gravitational redshift leads to a concept of black holes, objects from which nothing can escape.