Simultaneity

Simultaneity refers to two events happening at the same time from a particular perspective. In everyday life, we often assume things are simultaneous if they occur at the same moment according to our clocks. However, in physics—especially Einstein's theory of relativity—simultaneity depends on the observer’s motion. Different observers moving at different speeds may disagree about whether events happened at the same time. This means that simultaneity is relative, not absolute, and depends on the frame of reference of the observer.