설명Spacetime Diagrams of Mutual Time Dilation D.png
English: Events A and C are separated from event O by equal timelike intervals. From the unprimed frame, events A and B appear simultaneous, but more time has passed for the unprimed observer than has passed for the primed observer. From the primed frame, events C and D appear simultaneous, but more time has passed for the primed observer than has passed for the unprimed observer. Each observer measures the clocks of the other observer as running more slowly.