The Twin Paradox shows how time changes because of speed and mass. The faster someone or something moves or the more mass it has, then the slower time passes for them. This is shown by a pair of twins who are born at the same time. Let us name the first twin as T1 and the second twin as T2. We place T1 in a rocket, which travels at the speed of light, while the other twin stays back on the earth. On the return of T1, T2 finds out that his brother (T1) is younger than he is. As for T1, he finds out that his brother (T2)is older.