▁specified ▁his ▁clock ▁synchron ization ▁method ▁and ▁explained ▁the ▁possibility ▁of ▁a ▁" new ▁method " ▁or ▁" new ▁mechan ics ", ▁in ▁which ▁no ▁velocity ▁can ▁sur pass ▁that ▁of ▁light ▁for ▁all ▁obser vers . ▁However , ▁he ▁crit ically ▁noted ▁that ▁the ▁Rel ativity ▁Princi ple , ▁Newton ' s ▁action ▁and ▁reaction , ▁the ▁conservation ▁of ▁mass , ▁and ▁the ▁conservation ▁of ▁energy ▁are ▁not ▁fully ▁established ▁and ▁are ▁even ▁threatened ▁by ▁some ▁experiments . ▁ ▁Also ▁Emil ▁C ohn ▁( 1 9 0 4 ) ▁continued ▁to ▁develop ▁his ▁alternative ▁model ▁( as ▁described ▁above ), ▁and ▁while ▁comparing ▁his ▁theory ▁with ▁that ▁of ▁Lor ent z , ▁he ▁discovered ▁some ▁important ▁physical ▁interpret ations ▁of ▁the ▁Lor ent z ▁transformations . ▁He ▁illustrated ▁( like ▁Joseph ▁L arm or ▁in ▁the ▁same ▁year ) ▁this ▁transformation ▁by ▁using ▁ro ds ▁and ▁clock s : ▁If ▁they ▁are ▁at ▁rest ▁in ▁the ▁a ether , ▁they ▁indicate ▁the ▁true ▁length ▁and ▁time , ▁and ▁if ▁they ▁are ▁moving , ▁they ▁indicate ▁contract ed ▁and ▁dil ated ▁values . ▁Like ▁Po inc ar é , ▁C ohn ▁defined ▁local ▁time ▁as ▁the ▁time ▁that ▁is ▁based ▁on ▁the ▁assumption ▁of ▁is otrop ic ▁propag ation ▁of ▁light . ▁Con tr ary ▁to ▁Lor ent z ▁and ▁Po inc ar é ▁it ▁was ▁noticed ▁by ▁C ohn , ▁that ▁within ▁Lor ent z ' s ▁theory ▁the ▁separation ▁of ▁" real " ▁and ▁" app ar ent " ▁coordinates ▁is