Hello All, I like to think that I have a decent background in physics and related material, but I confuse myself quite easily on, well, everything. I guess I think about it too much, really. So feel free to give complex answers and I will do my best to follow along accordingly. Anyways, here is my current dilemma at hand: I picture an astronaut travelling home at near-light speeds to Earth from a distant star. Through relativistic principles, let's say that the astronaut experiences only 2 years of travel, while the Earth and its observers experience 4 years pass by. According to the theory of relativity, how exactly does his viewpoint compare to an observer on Earth watching him fly home? Does length contraction fit in anywhere to either perspective, since the viewpoints are from the start and finish points? Will the astronaut witness: a) time moving very fast on Earth, such that 4 Earth years of activity go by while he only experiences 2 years of aging (and thus Earth will witness the astronaut moving very slowly) or b) the length between him and Earth "shrink", such that he only travels 2 years' worth of distance (while an observer on Earth sees this length "elongate", thus appearing that the astronaut actually traveled 4 years' worth of distance) Essentially, how does relativity play spatial contraction vs. time dilation? Or will the astronaut undergo some combination of both? Does length/spatial contraction only work from a removed, outside perspective that does not lie along the path of the relativistic-moving object (in this case, the astronaut)? Please let me know if there's anything I can clear up to make the questions more clear. Thanks!