这样定义的坐标时好别扭，平直时空当然非常好，可是任意弯曲时空，两个相邻电磁波之间的“时间间隔”一般不是不变的呀，这样定义出来的“一秒”还有意义吗？我觉得最可靠的还是当时当地测量，用观者的固有时来定义坐标时。

我解释一下我为何这样定座标时. 参考 Landau 的 Classical field theory, Sec.88, p248 的这一段文字: The meaning of the world time in a constant gravitational field is that an interval of world time between events at a certain point in space coincides with the interval of world time between any other two events at any other point in space, if these events are respectively simultaneous with the first pair of events. But to the same interval of world time x^0 there correspond, at different points of space, different intervals of proper time tau.
我建议的座标时定义可以符合这个条件.

这种定义用在转盘上不知是否适合，放在圆心的电台与放在圆周上的电台时间不一样，圆心电台导致圆周上全局同时，而圆周上电台则没有全局同时。

时间空间如何弯曲？