Relativity of the concept of Distance

[geordief]

I am going through this section of Einstein's Popular Exposition of Special Relativity

https://www.bartleby.com/173/10.html#txt1

"In the first place we require to determine the points Aand B of the embankment which are just being passed by the two points A'and B'     at a particular time t—judged from the embankment.

These points A and B of the embankment can be determined by applying the definition of time given in Section VIII. The distance between these points A and B is then measured by repeated application of the measuring-rod along the embankment"

and have two questions I seem to need help with

1)

What might  be a rigorous  set up of an experiment to show this scenario?(I am struggling  with synchronizing the passing of the 2 points wrt to the observer's FOR)

2) Suppose we have an object moving at a relativistic  speed wrt an observer....

This object emits a light signal which is both transmitted directly to the observer and is also reflected immediately **off another object which is at rest wrt the observer.

Which signal does the observer see first? Do they both arrive simultaneously except for the retransmission time involved in the reflection process?

**ie the spatial distance between the moving object and the reflecting object in the same FOR as the observer is vanishingly small.

Edited December 25, 2019 by geordief