Chapter32 Relativity 32-3 The two postulates (P736-737) (1)The relativity postulate: the laws of physics are the same for observers in all inertial reference frames No frame is preferred.(相对性原理:物理规律对 所有的惯性系都是一样的,没有特例.P737) (2)The speed of light postulate: the speed of light in vacuum has the same value c=2.998x108m/s in all directions and in all inertial reference frames (34 速不变原理P737) Einsteins theory is based on the two postulates
(1)The relativity postulate: the laws of physics are the same for observers in all inertial reference frames. No frame is preferred.（相对性原理：物理规律对 所有的惯性系都是一样的，没有特例. P737） (2)The speed of light postulate: the speed of light in vacuum has the same value c=2.998x10 8m/s in all directions and in all inertial reference frames.（光 速不变原理 P737） Einstein’s theory is based on the two postulates. 32-3 The two postulates（P736-737）
Chapter32 Relativity 和光速不变紧密联系在一起的是:在某一惯性系 中同时发生的两个事件,在相对于此惯性系运动的另 惯性系中观察,并不一定是同时发生的 单 厢 她面始 说明同时具有相对性,时间的量度是相对的
说明同时具有相对性，时间的量度是相对的 . 和光速不变紧密联系在一起的是：在某一惯性系 中同时发生的两个事件，在相对于此惯性系运动的另 一惯性系中观察，并不一定是同时发生的
Chapter32 Relativity 32-4 Simultaneity(P737-739) Event An event is something that happens, to which an observer can assign (favE) three space coordinates and one time coordinate An event does not"belong to a particular inertial reference trame. anyone in any reference frame may detect it and assign space-time coordinates to it Different observers will assign different space-time coordinates to the same event
32-4 Simultaneity (P737-739) An event is something that happens, to which an observer can assign（指派） three space coordinates and one time coordinate. Event An event does not “belong” to a particular inertial reference frame. Anyone in any reference frame may detect it and assign space-time coordinates to it. Different observers will assign different space-time coordinates to the same event
Chapter32 Relativity Suppose an event is described by two observers, one in frame s(地面) and the other in frame s'(火 4), S' is moving with constant velocity v relative to s when a pulse of light leaves a light source in frame s
Suppose an event is described by two observers, one in frame S（地面） and the other in frame S’ （火 车），S’ is moving with constant velocity v relative to S. when a pulse of light leaves a light source in frame S’:
Chapter32 Relativity 厢 地面 始 事件1:车厢后壁接收器接收到光信号. 事件2:车厢前壁接收器接收到光信号
事件 1 ：车厢后壁接收器接收到光信号. 事件 2 ：车厢前壁接收器接收到光信号