Gravitational Radiation.

Since there are several similarities between general relativity and classical electromagnetism, this leads one to ask whether gravitational waves, like electromagnetic waves, really do exist. Difficulties due to the covariant nature of general relativity arise in the definition of a gravitational wave. A question which may arise is whether the waves carry energy or whether a radiating source loses mass. No exact solutions to the field equations are available to answer this question so approximation methods are used. From these solutions, one finds that some sources do emit gravitational waves, but whether freely gravitating systems such as the solar system lose energy or not is a matter to be resolved. Modified author abstract