I've been stuck on this physics problem for several years now. I would be very grateful if someone could explain how to solve this problem. The farthest a human could travel from Earth in one lifetime theoretically is limited only by the acceleration a human can withstand, and the length of their life. Solving the problem below would answer this question, taking into account relativity. A spaceship starts at rest on Earth, ignoring gravity. The spaceship then accelerates, and from the perspective of the astronauts inside the spaceship, it appears to accelerate at a constant 9.8 m/s^2. After the astronauts on the spaceship get 100 years older, how far away will the spaceship be from the perspective of Earth?