Simultaneity refers to the relationship between two events that occur at the same moment within a frame of reference. In physics, Newtonian mechanics assumes absolute time, in which simultaneity is universal, whereas Einstein’s relativity redefines it as dependent on the observer’s motion. Philosophers such as William James and Henri Bergson examined its subjective and temporal aspects, highlighting perception and continuity.
Bertrand Russell challenged the idea of a single, universal time, promoting the use of local temporal frameworks. Einstein himself emphasized the empirical foundation of simultaneity, connecting it to observable phenomena. These viewpoints illustrate simultaneity as both a physical concept and a philosophical challenge, influenced by context and perception.