Based on the two postulates that the speed of light is constant and the laws of physics apply equally to all inertial reference frames , the theory predicts strange effects such as time dilation , length contraction and simultaneity of events varies according to viewers 基于兩個論點,即光速不變及物理定律可應用于任何慣性系統(tǒng),狹義相對論預測了時間變慢長度收縮及同時事件是因觀察者而異等奇怪現(xiàn)象。