Will gravitational waves confirm Einstein’s General Relativity?

Even if Einstein’s General Relativity achieved a great success and overcame lots of experimental tests, it also showed some shortcomings and flaws which today advise theorists to ask if it is the definitive theory of gravity. In this proceeding paper it is shown that, if advanced projects on the detection of Gravitational Waves (GWs) will improve their sensitivity, allowing to perform a GWs astronomy, accurate angular and frequency dependent response functions of interferometers for GWs arising from various Theories of Gravity, i.e. General Relativity and Extended Theories of Gravity, will be the ultimate test for General Relativity. This proceeding paper is also a short review of the Essay which won Honorable Mention at the 2009 Gravity Research Foundation Awards. Recently, the data analysis of interferometric GWs detectors has been started (for the current status of GWs interferometers see [1]) and the scientific community hopes in a first direct detection of GWs in next years. Detectors for GWs will be important for a better knowledge of the Universe and either to confirm or rule out the physical consistency of General Relativity or of any other theory of gravitation [2, 3, 4, 5, 6, 7]. In fact, in the context of Extended Theories of Gravity, some differences between General Relativity and the others theories can be pointed out starting by the linearized theory of gravity [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]. In this tapestry, detectors for GWs are, in principle, sensitive to a hypothetical scalar component of gravitational radiation appearing in extended theories of gravity too, i.e. theories like scalartensor gravity [4, 8, 9, 10, 12], bi-metric theory [5], high order theories [2, 3, 6, 7], Brans-Dicke theory [13] and string theory [14]. Reasons of extending General Relativity arise from the fact that, even if Einstein’s Theory [15] achieved a great success (see for example the opinion of