Hi! Suppose a spacecraft is going to travel 10 lightyears in the velocity of 0.9c (in the Earth reference frame). Obviously, the travel takes 10/0.9=11.1 years for an observer on the Earth. According to special relativity theory, the travellers measure the time to 3.5 years. But: When is the arrival to the point 10 lightyears away from the Earth detected, i.e we can "see" the spacecraft at this point on the Earth? Is it possible to do at the time 11.1 years from start, or do we have to wait 11.1 + 10 = 21.1 years? Thanks for input!