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, at the end of the mission, the astronaut's age would be
A) exactly 30 years.
B) more than 50 years.
C) exactly 25 years.
D) less than 50 years.
E) exactly 50 years.

Question

Quizplus · Accepted Answer

Due to the effects of time dilation under the theory of relativity, time passes more slowly for objects moving at speeds close to the speed of light compared to those at rest. Therefore, the astronaut would age less than 20 years during the mission, making their biological age less than 50 years upon return.

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