stein ' s ▁paper ▁includes ▁a ▁fundamental ▁new ▁definition ▁of ▁space ▁and ▁time ▁( all ▁time ▁and ▁space ▁coordinates ▁in ▁all ▁reference ▁frames ▁are ▁on ▁an ▁equal ▁foot ing , ▁so ▁there ▁is ▁no ▁physical ▁basis ▁for ▁distingu ishing ▁" true " ▁from ▁" app ar ent " ▁time ) ▁and ▁makes ▁the ▁a ether ▁an ▁unnecessary ▁concept , ▁at ▁least ▁in ▁regard ▁to ▁in ert ial ▁motion . ▁Ein stein ▁identified ▁two ▁fundamental ▁principles , ▁the ▁principle ▁of ▁relativ ity ▁and ▁the ▁principle ▁of ▁the ▁const ancy ▁of ▁light ▁( light ▁principle ), ▁which ▁served ▁as ▁the ▁ax iom atic ▁basis ▁of ▁his ▁theory . ▁To ▁better ▁understand ▁Ein stein ' s ▁step , ▁a ▁summary ▁of ▁the ▁situation ▁before ▁ 1 9 0 5 , ▁as ▁it ▁was ▁described ▁above , ▁shall ▁be ▁given ▁( it ▁must ▁be ▁remarked ▁that ▁Ein stein ▁was ▁familiar ▁with ▁the ▁ 1 8 9 5 ▁theory ▁of ▁Lor ent z , ▁and ▁Science ▁and ▁Hyp oth esis ▁by ▁Po inc ar é , ▁but ▁not ▁their ▁papers ▁of ▁ 1 9 0 4 - 1 9 0 5 ): ▁ ▁a ) ▁Max well ' s ▁elect rod ynam ics , ▁as ▁presented ▁by ▁Lor ent z ▁in ▁ 1 8 9 5 , ▁was ▁the ▁most ▁successful ▁theory ▁at ▁this ▁time . ▁Here , ▁the ▁speed ▁of ▁light ▁is ▁constant ▁in ▁all ▁directions ▁in ▁the ▁station ary ▁a ether ▁and ▁completely ▁independent ▁of ▁the ▁velocity ▁of ▁the ▁source ; ▁b ) ▁The ▁in ability