Louis de Broglie

Louis de Broglie (1892–1987) was a French aristocrat — a genuine prince — who was supposed to become a historian, and instead dropped one of the strangest, most beautiful ideas in all of physics into his PhD thesis. His big claim: if light waves can act like particles, then particles like electrons must also act like waves. His examiners had no idea what to do with it.

The enduring idea

De Broglie proposed that every moving object has a wavelength — a "matter wave" — tying the two halves of wave–particle duality together. For everyday things the wavelength is absurdly tiny, which is why you don't diffract when you walk through a doorway. But for electrons it is just big enough to matter, and a few years later experiments showed electrons really do interfere and diffract like waves. He'd guessed right about the deepest layer of reality.

When de Broglie handed in his 1924 doctoral thesis, the committee was baffled — the idea was gorgeous but sounded like poetry, not physics. So they quietly forwarded it to Albert Einstein for a second opinion. Einstein wrote back that the young prince had "lifted a corner of the great veil." That settled it. Five years later de Broglie won the Nobel Prize — one of the very few people ever to earn it essentially for their PhD.