Hi all, I am taking a grade 12 physics course and we just covered special relativity theory however one thing troubles me; the twin paradox. The thought experiment proposes that a one twin travels to a distant star and back at a speed approaching that of light while the other twin remains on Earth. The twin on Earth should see his twin in the spaceship age slower, but wouldn't the twin on the ship think the same thing seeing Earth recede at high speed and then return. According to my textbook the answer is NO because the special theory of relativity applies only to inertial frames (in this case the Earth). The situation is not symmetrical since the spaceships velocity must change at the turn around point meaning it is a non-inertial reference frame. Here is my question; could the twin in the space ship not interpret the event as Earth moving away and then returning, from the frame of reference of the ship does Earth not appear to change its velocity at a turn around point making it non-inertial? Why is this thought experiment not symmetrical?