If one perceive the universe as a matrix, there are lines everywhere and therefore a tennis ball can never NOT be on the line, as there will always be a line where it may be.
如果一个人认为宇宙是一个矩阵，而矩阵里面到处都是线，因此，网球永远都不会不在线上，所以只要球能到哪，那里总是会有一条线。
A ball will always be 'in', whereas 'out', relatively speaking,
所以球总是会在“线内”、而在“线外”是相对而言的，
Einstein talks his way to victory at a Grand Slam Final
爱因斯坦在大满贯决赛时谈他获胜的方式