# Case of moving longitudinal light clock with no time dilation?

I refer here to the case of a light clock where each light pulse emitted travels forth and then reflected back between the two plates of the clock on the same axis as the direction of the moving clock:

Assuming you are using very short duration light pulses much shorter in duration than the time it takes them to travel to the opposite plate in the case where the clock was stationary, then when the clock is on the move and you register only the pulse moving in the same direction with the clock when it reaches the opposite plate, the result will be time dilation for the time recorded by this clock.

However my question is, if you register the time instead, only by using the reflected light pulse coming back to the initial plate, then will there be any time dilation effect?

• Certainly there will be time dilation, but you need to be careful in this case because it gets mixed up with length contraction and relativity-of-simultaneity effects. That's why pedagogically people usually start with the transverse light clock. Commented Aug 30, 2023 at 20:58
• My controversial take on the whole situation is that in the case of short duration light pulses and measuring the two-way path, the LLC operates under Galilean relativity and not SR. Commented Aug 31, 2023 at 18:10