Chapter 37, Problem 4Q

Figure 37-17 shows two clocks in stationary frame S' (they are synchronized in that frame) and one clock in moving frame S. Clocks C₁ and $C_1^{\text{'}}$ read zero when they pass each other. When clocks C₁ and $C_2^{\text{'}}$ pass each other, (a) which clock has the smaller reading and (b) which clock measures a proper time?

Figure 37-17 Question 4.