Chapter 27, Problem 47GP

Hill Two spaceships approach each other at speeds of 0.80c and 0.90c relative to the sun. When they are 5.0 × 10⁹ m apart, as measured in the sun’s reference frame, they each set their clocks to zero. By how much do their clocks differ at the instant they pass each other?

Hint: First find how long it takes the spaceships to pass in the sun’s reference frame.