translation.en: So he imagined that the world had four dimensions of space, not three, and imagined that electromagnetism was warps and curves in that fourth dimension. Now here's the thing: when he wrote down the equations describing warps and curves in a universe with four space dimensions, not three, he found the old equations that Einstein had already derived in three dimensions -- those were for gravity -- but he found one more equation because of the one more dimension.
translation.zh: 所以他想象这个世界是由四个维度的空间组成，而不是三个， 并且电磁力的作用是在第四维度上 的“扭曲”而产生的。请注意这里： 当他在写方程式组来描述四度空间的“扭曲”， 不再是三度空间的时候， 他发现“爱因斯坦”以三度空间为模型构建的方程式组-- 就是用来描述重力的-- 因其添加了额外的一维空间而增加了一个方程式。