▁fict it ious ▁elect romagnet ic ▁momentum ▁as ▁well . ▁However , ▁he ▁arrived ▁at ▁a ▁radiation ▁par ado x ▁which ▁was ▁fully ▁explained ▁by ▁Ein stein ▁in ▁ 1 9 0 5 . ▁ ▁Walter ▁Kauf mann ▁( 1 9 0 1 – 1 9 0 3 ) ▁was ▁the ▁first ▁to ▁confirm ▁the ▁velocity ▁dependence ▁of ▁elect romagnet ic ▁mass ▁by ▁analyz ing ▁the ▁ratio ▁ ▁( where ▁ ▁is ▁the ▁charge ▁and ▁ ▁the ▁mass ) ▁of ▁c ath ode ▁ray s . ▁He ▁found ▁that ▁the ▁value ▁of ▁ ▁decre ased ▁with ▁the ▁speed , ▁showing ▁that , ▁assuming ▁the ▁charge ▁constant , ▁the ▁mass ▁of ▁the ▁electron ▁increased ▁with ▁the ▁speed . ▁He ▁also ▁believed ▁that ▁those ▁experiments ▁confirmed ▁the ▁assumption ▁of ▁Wien , ▁that ▁there ▁is ▁no ▁" real " ▁mechanical ▁mass , ▁but ▁only ▁the ▁" app ar ent " ▁elect romagnet ic ▁mass , ▁or ▁in ▁other ▁words , ▁the ▁mass ▁of ▁all ▁bodies ▁is ▁of ▁elect romagnet ic ▁origin . ▁ ▁Max ▁Abraham ▁( 1 9 0 2 – 1 9 0 4 ), ▁who ▁was ▁a ▁supp orter ▁of ▁the ▁elect romagnet ic ▁world ▁view , ▁quickly ▁offered ▁an ▁explanation ▁for ▁Kauf mann ' s ▁experiments ▁by ▁der iving ▁expressions ▁for ▁the ▁elect romagnet ic ▁mass . ▁T ogether ▁with ▁this ▁concept , ▁Abraham ▁introduced ▁( like ▁Po inc ar é ▁in ▁ 1 9 0 0 ) ▁the ▁notion ▁of ▁" E lect romagnet ic ▁M oment um " ▁which ▁is ▁proportional