Albert Einstein's General Theory of Relativity was challenged and notconclusively proven for over 15 years - from when he first proposed itin 1908 until 1922, when examination of total Solar Eclipse proved thatgravity manifests itself through curvature of time space.
So, when do you decide that it is "conclusively proven"? What is your scientific criterion? :-)
BTW, General Relativity was introduced in 1915 in the presentation to the Prussian Academy of Sciences -- not in 1908.