http://arxiv.org/abs/1602.04674
"Around 1936, Einstein wrote to his close friend Max Born telling him that, together with Nathan Rosen, he had arrived at the interesting result that gravitational waves did not exist, though they had been assumed a certainty to the first approximation. He finally had found a mistake in his 1936 paper with Rosen and believed that gravitational waves do exist. However, in 1938, Einstein again obtained the result that there could be no gravitational waves!"

http://www.huffingtonpost.com/christ...b_9214794.html
"What is less well known is that Einstein struggled mightily with the theory of gravitational waves. The fact that Einstein was a genius but nevertheless mortal is, by now, somewhat known. After all, it took him five tries to get the field equations of General Relativity right."

Typical empirical approach isn't it? Unlike special relativity, general relativity was not, to use Einstein's words, "built up logically from a small number of fundamental assumptions". Rather, it was "a purely empirical enterprise" - Einstein and his mathematical friends changed and fudged equations countless times until "a classified catalogue" was compiled in which known in advance results and pet assumptions (such as the Mercury's precession, the equivalence principle, gravitational time dilation) coexisted in an apparently consistent manner:

https://www.marxists.org/reference/a...ative/ap03.htm
Albert Einstein: "From a systematic theoretical point of view, we may imagine the process of evolution of an empirical science to be a continuous process of induction. Theories are evolved and are expressed in short compass as statements of a large number of individual observations in the form of empirical laws, from which the general laws can be ascertained by comparison.. Regarded in this way, the development of a science bears some resemblance to the compilation of a classified catalogue. It is, as it were, a purely empirical enterprise. But this point of view by no means embraces the whole of the actual process ; for it slurs over the important part played by intuition and deductive thought in the development of an exact science. As soon as a science has emerged from its initial stages, theoretical advances are no longer achieved merely by a process of arrangement. Guided by empirical data, the investigator rather develops a system of thought which, in general, is built up logically from a small number of fundamental assumptions, the so-called axioms."

Since general relativity is an empirical model, it can predict anything - e..g. both existence and non-existence of gravitational waves. Or both static and expanding universe. Or both constant and variable speed of light. Anything!

Pentcho Valev