Well, because he looked around himself and he saw all these fabulous physicists that created quantum mechanics and modern physics, and they were all in their 20s and early 30s when they did so.
아마 본인과 주변의  훌륭한 물리학자들을 돌아봤겠죠. 양자역학과 현대 물리학을 창시한 과학자들을요. 그 일을 해냈을 때 그들이 모두  20대 이거나 30대 초반이었거든요.