▁phen omena ▁propag ate ▁through ▁that ▁medium , ▁which ▁suggested ▁that ▁it ▁should ▁be ▁possible ▁to ▁experiment ally ▁determine ▁motion ▁relative ▁to ▁the ▁a ether . ▁ ▁The ▁failure ▁of ▁any ▁known ▁experiment ▁to ▁detect ▁motion ▁through ▁the ▁a ether ▁led ▁Hend rik ▁Lor ent z , ▁starting ▁in ▁ 1 8 9 2 , ▁to ▁develop ▁a ▁theory ▁of ▁elect rod ynam ics ▁based ▁on ▁an ▁imm obile ▁l umin ifer ous ▁a ether ▁( about ▁whose ▁material ▁constitution ▁Lor ent z ▁didn ' t ▁spec ulate ), ▁physical ▁length ▁contra ction , ▁and ▁a ▁" local ▁time " ▁in ▁which ▁Max well ' s ▁equations ▁retain ▁their ▁form ▁in ▁all ▁in ert ial ▁frames ▁of ▁reference . ▁Working ▁with ▁Lor ent z ' s ▁a ether ▁theory , ▁Henri ▁Po inc ar é , ▁having ▁earlier ▁proposed ▁the ▁" rel ativity ▁principle " ▁as ▁a ▁general ▁law ▁of ▁nature ▁( including ▁elect rod ynam ics ▁and ▁grav itation ), ▁used ▁this ▁principle ▁in ▁ 1 9 0 5 ▁to ▁correct ▁Lor ent z ' s ▁pre lim inary ▁transformation ▁formulas , ▁resulting ▁in ▁an ▁exact ▁set ▁of ▁equations ▁that ▁are ▁now ▁called ▁the ▁Lor ent z ▁transformations . ▁A ▁little ▁later ▁in ▁the ▁same ▁year ▁Albert ▁Ein stein ▁published ▁his ▁original ▁paper ▁on ▁special ▁relativ ity ▁in ▁which , ▁again ▁based ▁on ▁the ▁relativ ity ▁principle , ▁he ▁independently ▁derived ▁and ▁rad ically ▁re inter pre ted ▁the ▁Lor ent z ▁transformations ▁by ▁changing ▁the ▁fundamental ▁definitions ▁of ▁space ▁and ▁time