At age 21,you set out for a star that is 50 light-years from Earth.How fast would your spaceship have to travel in order to reach that star when you are 61 years old? One light-year is the distance light travels in one year.
A)0.58c
B)0.68c
C)0.78c
D)0.88c
E)0.96c

Question

Quizplus · Accepted Answer

To reach a star 50 light-years away in 40 years (from age 21 to 61), the spaceship must travel at a speed of 50 light-years / 40 years = 1.25 light-years per year. However, this speed is not possible as it exceeds the speed of light. Instead, using the relativistic formula for time dilation, the spaceship must travel at approximately 0.78c to make the journey in the traveler's frame of reference.

At Age 21,you Set Out for a Star That Is