A 30-year-old astronaut goes off on a long term mission in a spacecraft that travels at speeds close to that of light. The mission lasts exactly 20 years as measured on Earth. Biologically speaking, the astronaut's age would be
A) more than 50 years.
B) exactly 50 years.
C) less than 50 years.
D) exactly 30 years.
E) exactly 25 years.

Question

Quizplus · Accepted Answer

According to the theory of relativity, time dilation occurs at high speeds close to that of light. This means that time passes more slowly for the astronaut relative to Earth. For a 20-year mission on Earth, the astronaut's biological age would be less than 50 years as measured by Earth because time dilation would cause them to age more slowly during the mission.

A 30-Year-Old Astronaut Goes Off on a Long Term Mission