Question

Consider the following events: The births and deaths of three people. We consider two inertial frames of reference S and S' with their axes aligned (always parallel).

S' moves along the +x-axis at a speed 0.98c with respect to S.

We think of S as an inertial system in which the Earth is at rest, and of S' as one in which a spaceship is at rest.

At t=t'=0, observers in S record the simultaneous births of the three people: Sam, born at the origin; Astrid, born at x=+10 ly; and Jena, born at the origin. Both Sam and Astrid are always at rest in S throughout their 70 year lifespan, according to observers in S.

Jena, on the other hand, is born and remains at the rest in the spaceship, which is at rest in S'. With respect to S', Jena also lives 70 years.

A) According to observers in S (at rest on Earth), how long does Jena live?

B) According to observers in S' (spaceship at rest), how long do Sam and Astrid live?

Answer 1