A mother and her son share the same birthday. Then say a mother is 24 years old when her son was born. Then when she was 50 (her birthday, and his) she went on an intergalactic flight and a return trip all at constant speed at (12 / 13) c. She returns back to find that her son and her are the same age. What age is that? How far away did she go? that is 1/2 the distance travelled. So i know that t2 - t1 = gamma (t2' - t1') but i'm a little confused on where do i go from here.