Maybe some one can help clear up a problem. According to Wikipedias article on time dilation “In the case that the observers are in relative uniform motion, and far away from any gravitational mass, the point of view of each will be that the other's (moving) clock is ticking at a slower rate than the local clock.” Which I can accept but this does not seem consistent with the “time slowing down for a space traveler” situation. If the space traveler is moving fast relative to the earth the people on earth will see that time is passing more slowly for traveler. The traveler will think that the time on the earth is moving more slowly. So what happens when he gets back to earth he’s been observing that earth time has been moving more slowly so he would be older that earth time would suggest. But also for the earth people the travelers time would have been passing more slowly so he should be younger. Which is a contradiction.