Hello , I'm not great at maths but this morning I have attempted to add some values to my question in case it was not understood .
1. Clock at relative rest
H = ~399723277m
Tick rate = 1.3 light seconds per tick
What's this H thing?
I get that it's a distance of some kind. Light, travelling at 299 792 458 m/s would take 1.3333 seconds to travel distance H.
2. Clock in relative motion
H= 299792458m
Light would take 1 second to travel that distance.
Angular path distance the light travels
d=~399723277m
Is this a light clock?
Let's assume it is. Then let's make H =299792458 m the distance between two mirrors that are stationary (on a spaceship, say). Somebody watches that spaceship fly past at speed v, and the light follows a "slanted" path as it travels between the mirrors. Then d is the "slanted" path distance, which you call "angular path distance".
So, in the spaceship rest frame, the light takes 1 second to travel between the mirrors - call that one "tick" on the spaceship, or one "spaceship tick".
In the "outside" frame, the light takes 1.333 seconds to travel between the mirrors - call that one "Earth tick".
The fact that it takes different times in the two frames is due to the assumption that the
speed of light is
the same in both frames - a fundamental assumption of Einstein's special theory of relativity.
It follows that "outside" observers say that the spaceship clock is running "slow", because 1 spaceship tick equates to 1.333 Earth ticks.
With a bit more analysis, we can determine that the speed of this spaceship, relative to the Earth, must be 0.66 c, where c is the speed of light.
---
So, that's all fine. Now what?