see ▁Elect romagnet ic ▁mass ). ▁Event ually ▁Plan ck ▁( 1 9 0 7 ) ▁derived ▁the ▁mass - energy - equ ival ence ▁in ▁general ▁within ▁the ▁framework ▁of ▁special ▁relativ ity , ▁including ▁the ▁binding ▁forces ▁within ▁matter . ▁He ▁acknowled ged ▁the ▁priority ▁of ▁Ein stein ' s ▁ 1 9 0 5 ▁work ▁on ▁, ▁but ▁Plan ck ▁jud ged ▁his ▁own ▁approach ▁as ▁more ▁general ▁than ▁Ein stein ' s . ▁ ▁Exper iments ▁by ▁F ize au ▁and ▁S agn ac ▁As ▁was ▁explained ▁above , ▁already ▁in ▁ 1 8 9 5 ▁Lor ent z ▁succeeded ▁in ▁der iving ▁F res nel ' s ▁drag ging ▁coefficient ▁( to ▁first ▁order ▁of ▁v / c ) ▁and ▁the ▁F ize au ▁experiment ▁by ▁using ▁the ▁elect romagnet ic ▁theory ▁and ▁the ▁concept ▁of ▁local ▁time . ▁After ▁first ▁attempts ▁by ▁Jakob ▁La ub ▁( 1 9 0 7 ) ▁to ▁create ▁a ▁relativ istic ▁" opt ics ▁of ▁moving ▁bodies ", ▁it ▁was ▁Max ▁von ▁La ue ▁( 1 9 0 7 ) ▁who ▁derived ▁the ▁coefficient ▁for ▁terms ▁of ▁all ▁orders ▁by ▁using ▁the ▁col ine ar ▁case ▁of ▁the ▁relativ istic ▁velocity ▁addition ▁law . ▁In ▁addition , ▁La ue ' s ▁calculation ▁was ▁much ▁simpler ▁than ▁the ▁complicated ▁methods ▁used ▁by ▁Lor ent z . ▁ ▁In ▁ 1 9 1 1 ▁La ue ▁also ▁discussed ▁a ▁situation ▁where ▁on ▁a ▁platform ▁a ▁beam ▁of ▁light ▁is ▁split ▁and ▁the ▁two ▁be