1. Twins Abby and Billy separate. Abby travels at a uniform speed (except for the brief turn-around period) to a star 4.2 light years away and, upon returning, finds that she is 5.2 years younger than Bill. How fast was Abby traveling? By how much has Bill aged during the period Abby was traveling? 2. T'=2L/C T' = T_o=sqrt(1-v^2/c^2) deltaT = T' - T_o 3. So far I have found the time dialation using T'=2L/C => 2(4.2)/C = 2.8^-8 I tried using T' = T_o=sqrt(1-v^2/c^2) to find velocity, is that correct? I'm not sure what T_o is.