The identical twins Speedo and Goslo join a migration from the Earth to Planet X, which is 20.0 light-years away in a reference frame in which both planets are at rest. The twins, of the same age, depart at the same time on different spacecraft. Speedo's craft travels steadily at 0.905c, Goslo's at 0.680c. Calculate the age difference between the twins after Goslo's spacecraft lands on Planet X. Which twin is the older? Goslo is older by years.

The identical twins Speedo and Goslo join a migration from the Earth to Planet X, which is 20.0 light-years away in a reference frame in which both planets are at rest. The twins, of the same age, depart at the same time on different spacecraft. Speedo's craft travels steadily at 0.905c, Goslo's at 0.680c. Calculate the age difference between the twins after Goslo's spacecraft lands on Planet X. Which twin is the older? Goslo is older by years.