Rịba ama amaokwu a dị n'okpuru ma zaa ajụjụ ahụ mgbe e mesịrị n'otu asụsụ ahụ dị ka amaokwu ahụ:  N'abalị ise n'ọnwa Jun, n'afọ 1905, Henri Poincaré wepụtara nchịkọta nke otu akwụkwọ nke mere ka a ghọtakwuo ihe ndị Lorentz dere. (Akwụkwọ a dị mkpirikpi nwere nsonaazụ nke ọrụ zuru oke nke a ga-ebipụta mgbe e mesịrị, na Jenụwarị 1906.) O gosipụtara na Lorentz's equations nke electrodynamics abụghị Lorentz-covariant n'ụzọ zuru ezu. Ya mere, ọ rụtụrụ aka na njirimara otu nke mgbanwe ahụ, wee dozie usoro Lorentz maka mgbanwe nke njupụta ụgwọ na njupụta nke ugbu a (nke nwere usoro mgbakwunye ọsọ ọsọ, nke ọ kọwapụtara na May n'akwụkwọ ozi nye Lorentz). Poincaré bụ onye mbụ jiri okwu ahụ bụ́ "Lorentz transformation" mee ihe, ọ bụkwa ya mere ka mgbanwe ndị ahụ nwee ọdịdị kwekọrọ ekwekọ ha ji eme ihe ruo taa. Ọ webatara ike ejikọtaghị eletrik (nke a na-akpọ "Poincaré stresses") iji hụ na nkwụsi ike nke elektrọn na ịkọwa mkpụkọ ogologo. O mekwara ihe osise nke Lorentz-invariant model of gravitation (gụnyere gravitational waves) site na ịgbasa ịdị irè nke Lorentz-invariance na ndị na-abụghị ọkụ eletrik. N'ikpeazụ, Poincaré (n'adabereghị na Einstein) rụchara nnukwu ọrụ nke akwụkwọ ya nke June (nke a na-akpọ "akwụkwọ Palermo", natara July 23, e bipụtara ya na Disemba 14, bipụtara na Jenụwarị 1906 ). O kwuru kpọmkwem banyere "ụkpụrụ relativity". O gosipụtara na mgbanwe ndị ahụ bụ nsonaazụ nke ụkpụrụ nke obere ihe ma mepụta njirimara nke nrụgide Poincaré. O gosiputara n'ụzọ zuru ezu njirimara otu nke mgbanwe ahụ, nke ọ kpọrọ otu Lorentz, o gosikwara na njikọta ahụ  Ajụjụ: N'agbanyeghị na e bipụtara ya ihe dị ka ọnwa asaa ka e bipụtasịrị ya, olee ụbọchị e nwetara akwụkwọ ozi Palermo ahụ?
July 23