posted January 10, 2013 09:43 AM Here is a link to Einsteins article 'On the electrodynamics of moving bodies' <a href="http://www.fourmilab.ch/etexts/einstein/specrel/www/">http://www.fourmilab.ch/etexts/einstein/specrel/www/</a> Would anyone please explain this to me (from &3): 'If we place x'=x-vt, it is clear that a point at rest in the system k must have a system of values x', y, z, independent of time.