Question

A set of twins, Andrea and Courtney, are initially 10 years old. While Courtney remains on Earth, Andrea rides on a spaceship which travels away from Earth at a speed of 0.50 c for five years (as measured by Courtney), then immediately turns around and comes back at 0.50c . When Andrea returns, Courtney is 20 years old. How old is Andrea upon her return?

Answer 1

she is 20 at least I think not entirely sure about that!

Explanation:

if Courtney is here on earth while her twin Andrea is in space she ages by the same rate just it's a little bit different. no one knows how long Andrea has slept for or how long she was up there for.