Chapter 1 Introduction (1) Length(长度P5): One meter is the length of p path traveled by light in a vacuum during a time interval(间隔)of 1/299792458 of a second. P5 (2)Time(时间P6): One second is the time taken by 9192631770 oscillations(振动) of the light emitted by a cesium(铯) 133 atom (3)Mass(质量P6): One kilogram is defined in terms of根据、按照 a particular platinum-iridium(铂铱) cylinder(柱 A) kept near Paris, france. For measurements on an atomic scale, the atomic mass unit, defined in terms of the atom carbon -12. is usually used. 1u=1. 6605402x10-27 kgChapter 1 Introduction One meter is the length of path traveled by light in a vacuum during a time interval（间隔） of 1/299792458 of a second. P5 One second is the time taken by 9192631770 oscillations(振动) of the light emitted by a cesium（铯） -133 atom. One kilogram is defined in terms of(根据、按照） a particular platinum-iridium（铂铱） cylinder（柱 体） kept near Paris, France. For measurements on an atomic scale, the atomic mass unit, defined in terms of the atom carbon-12, is usually used. 1u=1.6605402x10-27 kg （1）Length （长度P5）: （2）Time（时间P6） : （3）Mass（质量P6） :