The theory of relativity was first studied by an italian Olinto de Pretto. But he didnt have the political backing that Einstein had.
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Links to credible sources like Wikipedia?
And if that's not nuff 
Yes, yes, yes! https://www.youtube.com/watch?v=y6lxJAqVjkY
Perihelion of Mercury. Clearly explained by Paul, who assumed a finite speed of gravity. Einstein copied his maths. Nice one, Albert.