And it turns out the second solution, with negative energy, was when the theory is telling you, hey, there are particles and there are anti-particles, and the negative energy when properly interpreted will describe anti-particles.

结果,后来证明,第二个根,也就是能量为负的那个根,正是理论的关键,世界上既有粒子,也有反粒子,负能量就是用来解释反粒子的

耶鲁公开课 - 基础物理课程节选

So always amazing to us how we go into the problem, our eye or mind can see one class of solutions, but the math will tell you sometimes there are new solutions and you've got to respect it and understand and interpret the unwanted solutions, and this is a simple example where you can follow what the meaning of the second solution is.

解决问题的方式总能让人惊喜不已,我们的眼睛或思想可以看见一类解,但数学有时会告诉你还有新的解,你不能忽视它,而是解释这些不期而至的解,这只是一个简单的例子,由此你可以理解第二个解的意义

耶鲁公开课 - 基础物理课程节选

But the mathematicians told Dirac, "You cannot ignore the negative energy solution because it tells you there's a second solution and you cannot throw them out."

但数学家们告诉狄拉克,你不能忽略负的能量,因为数学告诉我有两个根,你不能随便丢掉

耶鲁公开课 - 基础物理课程节选