Mercury's orbit is easily predicted from Newton's laws, but the prediction is -- just a tiny little bit -- Wrong. http://en.wikipedia.org/wiki/Tests_of_general

Mercury's orbit is easily predicted from Newton's laws, but the prediction is -- just a tiny little bit -- Wrong. http://en.wikipedia.org/wiki/Tests_of_general_relativity#Perihelion_precession_of_Mercury http://en.wikipedia.org/wiki/Tests_of_general_relativity#Per... No one gets younger by traveling faster, but one of the ideas of the twin paradox is to set up a real situation where the changing perception of time by different observers adds up to a real effect that can be clearly seen to persist once the twins are back together, and are once again agreeing on their perception of time.