Twin A is at rest with respect to Twin B who is traveling close to c and after taking off for a bit Twin B turns and returns to earth. Now the thing that I am wondering is what does each twin observe during the whole trip. I might have it wrong and thats why I made this thread. Lets say that 1 year goes by for Twin B during the whole trip and 40 years goes by for Twin A during the whole trip. I assume that everything Twin B does during his 1 year will be observed by Twin A within the 40 years. And everything Twin A does during the 40 years will be observed by Twin B in a year. When Twin B leaves Twin A they both observe each other in slow motion, as Twin B turns the light still has to reach Twin A so when Twin A finally observes Twin B's turn he should observe Twin B almost instantly travel back to earth like the doppler effect. Twin B also observes Twin A's clock run faster then his own right? I'm not sure if everything I just said was accurate but I wonder when most of Twin A's 40 years observed by Twin B takes place, during the return trip?