Answer:

relativity

AnswerCrossword Clue
RELATIVITYSubject of 15 Across's third 1905 article
RELATIVITYScientific theory formulated in 1905.
RELATIVITYHistoric theory in physics.
RELATIVITYFamous theory.
RELATIVITYTheory in physics.
RELATIVITYConcern of the physicists.
RELATIVITYTheory of 1905.
RELATIVITYEinstein's famous theory