▁( 1 8 9 5 ). ▁In ▁ 1 9 0 1 ▁a ▁philosoph ical ▁model ▁was ▁developed ▁by ▁Men y h ért ▁Pal á gy i , ▁in ▁which ▁space ▁and ▁time ▁were ▁only ▁two ▁sides ▁of ▁some ▁sort ▁of ▁" sp ac etime ". ▁He ▁used ▁time ▁as ▁an ▁imag inary ▁fourth ▁dimension , ▁which ▁he ▁gave ▁the ▁form ▁ ▁( where ▁, ▁i . e . ▁imag inary ▁number ). ▁However , ▁Pal agy i ' s ▁time ▁coordinate ▁is ▁not ▁connected ▁to ▁the ▁speed ▁of ▁light . ▁He ▁also ▁rejected ▁any ▁connection ▁with ▁the ▁existing ▁constru ctions ▁of ▁n - dimensional ▁spaces ▁and ▁non - E uclidean ▁geometry , ▁so ▁his ▁philosoph ical ▁model ▁be ars ▁only ▁little ▁res embl ance ▁with ▁spac etime ▁physics , ▁as ▁it ▁was ▁later ▁developed ▁by ▁M ink owski . ▁ ▁Light ▁const ancy ▁and ▁the ▁principle ▁of ▁relative ▁motion ▁ ▁In ▁the ▁second ▁half ▁of ▁the ▁ 1 9 th ▁century ▁there ▁were ▁many ▁attempts ▁to ▁develop ▁a ▁world wide ▁clock ▁network ▁synchron ized ▁by ▁elect rical ▁signals . ▁For ▁that ▁ende avor , ▁the ▁finite ▁propag ation ▁speed ▁of ▁light ▁had ▁to ▁be ▁considered , ▁because ▁synchron ization ▁signals ▁could ▁travel ▁no ▁faster ▁than ▁the ▁speed ▁of ▁light . ▁So ▁Henri ▁Po inc ar é ▁( 1 8 9 8 ) ▁in ▁his ▁paper ▁The ▁Me asure ▁of ▁Time ▁drew ▁some ▁important ▁consequences ▁of ▁this ▁process ▁and ▁explained ▁that ▁astronom ers , ▁in ▁determ ining ▁the ▁speed ▁of ▁light , ▁simply