Abstract: In the study of special relativity, ‘simultaneous relativity’ is the most confusing and difficult to understand, and the fundamental reason lies in how to understand the essence of time and space. This article explains in detail through case studies that understanding time and space should be closely integrated with the movement of matter. Time and space are intrinsic properties of matter, and their properties can only be reflected in the motion and interconnected physical processes of matter.

Key words: the special theory of relativity, simultaneous relativity, spatiotemporal properties