Chapter 2, Problem 48E

You stand at the center of your 100 m spaceship and watch Anna’s identical ship pass at 0.6c. At $t=0$ on your wristwatch, Anna, at the center of her ship, is directly across from you and her wristwatch also reads 0.
(a) A friend on your ship, 24 m from you in a direction toward the tail of Anna’s passing ship, looks at a clock directly across from him on Anna’s ship. What does it read?
(b) Your friend now steps onto Anna’s ship. By this very act, he moves from a frame where Anna is one age to a frame where she is another. What is the difference in these ages? Explain. (Hint: Your friend moves to Anna’s frame, where the time is whatever the clock at the location reads.)
(c) Answer parts (a) and (b) for a friend 24 m from you but in a direction toward the front of Anna’s passing ship.
(d) What happens to the reading on a clock when you accelerate toward it? Away from it?