He was 23 years old at the time. (But he was already doing important work on QM, like the introduction of the density matrix earlier that year. https://en.wiki

He was 23 years old at the time. (But he was already doing important work on QM, like the introduction of the density matrix earlier that year. https://en.wikipedia.org/wiki/Mathematical_Foundations_of_Quantum_Mechanics https://en.wikipedia.org/wiki/Mathematical_Foundations_of_Qu... would be published five years later.)