Xie Feng pointed to the line between the two little figures on the blackboard: "This is the line in the four-dimensional space. In other words, we, who exist in three dimensions, are constantly moving forward along the timeline in four-dimensional space."
"As mentioned before, two-dimensional beings can only see the cross-sections of three-dimensional objects. Similarly, as three-dimensional beings, we can only see the cross-sections of four-dimensional space. This is why we cannot perceive the past or the future, but can only observe the world as it exists in the present moment. The great physicist Einstein once described the fourth dimension as time, thereby deriving the concept of 'spacetime.' We three-dimensional beings exist in a four-dimensional world, but our position in it is not high enough to see the world in its entirety."
