Which of the following correctly describes the situation when Jackie returns to Earth? (Ages in this problem refer to biological ages-that is,how much time has passed for each sister since she was born. )
A)It's the year 2050,and both twin sisters are 70 years old.
B)It's the year 2050.Gwen (who stayed home)is 70 years old,but Jackie is only a little older than her age of 20 when she left.
C)It's the year 2050.Gwen is 70 years old.Jackie is 19.
D)It's the year 2100.Gwen and Jackie are both 120 years old.
E)According to Gwen,Jackie returns to Earth in the year 2050,but according to Jackie,she returns in the year 2001.

Question

Quizplus · Accepted Answer

According to the problem, Jackie travels 10 light years away and back at a speed of 0.6 times the speed of light. From the perspective of Gwen on Earth, 30 years have passed (since 2050-2020=30), so she is 70 years old. Meanwhile, Jackie's biological clock has slowed down due to time dilation, meaning that she has aged less than Gwen. Using the time dilation formula, we can calculate that Jackie has aged approximately 2.5 years (10 years / sqrt(1 - 0.6^2) / 2), which means that she is only a little older than her original age of 20 when she left. Therefore, B is the correct choice.

Which of the Following Correctly Describes the Situation When Jackie