Question

There is a set of twins, one an

astronaut, the other works for mission control of NASA. The astronaut leaves on

a deep space trip traveling at 95% the speed of light. Upon returning the

astronauts clock has measured ten years, so the astronaut has aged 10

years. What is the time that the

earth-bound brother measures while his twin was on his exploration in space?

How old is he?

Answer 1

$t=\frac {t_0}{\sqrt{1-\frac{v^2}{c^2}}}=32$ years.