一切物体都在不停地变化和运动着,这些变化和运动都是在一定的时间内进行的。为了定量描述具有广泛性和抽象性的时间,人们总是利用一些周期性的运动,并为了使时间测量准确统一,所选定的运动周期既要尽可能稳定,又要容易获得和复现。据此,本文就介绍秒的定义和变迁。 All objects are constantly changing and moving, these changes and movements are carried out within a certain period of time. In order to quantitatively describe the time of broadness and abstraction, people always make use of some periodic motions, and in order to make the time measurement accurately uniform, the selected motional cycle should be as stable as possible and easy to obtain and reproduce. Accordingly, this article introduces the definition and change of seconds.