I was just thinking about the case,
The whole cenario is in space there was an space craft it is attached to a mirror say 1.5 *108 m below the space craft by many taut rods. Space craft is moving horizontally with high constant velocity. A person in space craft throws a ray of light to the attached mirror, velocity of light is 3*108 m/sec. So time taken by ray of light to come back at initial position is 1sec.
There was another observer w.r.t him ray of light follows a v-shaped path where the edge of v-shaped path is 1.5*108 m below so each part of path must be greater then 1.5*108 m this mean overall distance is increased ! So time taken also increased!
Both person start as well as stop their stop watch simultaneously.
But it read different time period how?
What is happening here?