Originally Posted by Bjarne
Exactly which ruler, Bjarne?
If motion is absolute, then all observers are absolute. In an absolute motion scenario, the change of the "ruler" (whichever ruler you might be referring to) would be observable and measurable.
However, this is not what we observe. What we do observe is that all observers are local. In other words, we are unable to measure any change in our own "ruler". Instead, we observe that the "ruler" is changed in other motion frames (as in time dilation).