我刊从去年以来，已先后有数篇封面专题文章（包括本期）描述了空间、时间、速度、温度等物理量的精彩现象。物理量是用来量度我们这个大千世界的，是我们认识世界的重要工具。当物理量发生变化时，事物的性质也发生了惊人的变化，这些变化已在我们多期的封面专题文章中有深入 Since last year, I have published a number of cover feature articles (including this issue) that describe wonderful phenomena of physical quantities such as space, time, speed, and temperature. Physical quantity is used to measure our world. It is an important tool for us to understand the world. When the physical quantity changes, the nature of things has changed dramatically. These changes have been deepened in our multi-period cover article.