The mysterious disappearance (or not) of the physicist who discovered neutrons (or not).

In 1938, Ettore Majorana boarded a ship to Naples, and never got off at the other end. Since then people have been debating what happened to the physicist, and whether or not he had a larger part in the history of physics than he's given credit for.

Enrico Fermi, the brilliant physicist who developed the first nuclear reactor and won the Nobel prize for his explorations of radioactivity, might possibly have been eclipsed in his own time by one of his colleagues. Five years younger than Fermi, Ettore Majorana was a rising star in physics when he disappeared in 1938, at the age of 32. Rumors have been swirling around his disappearance since the moment he failed to step off the boat that he was spotted boarding in March - a boat set for Naples.

It's no surprise that Majorana was the center of such a mystery. During his life, he was famously enigmatic. There is evidence that he came up with the proof of the neutron before the official confirmation by James Chadwick, but did not publish his findings. Majorana, it is said, was sure that someone else would discover them and unlike almost everyone else in his profession he hated the spotlight. Fermi, though only slightly older, took it upon himself to mentor Majorana, including hounding him into publishing his paper about some particles, like photons, being their own antiparticles. This brought attention to Majorana; attention he responded to by working in near-complete isolation for years.

Majorana's disappearance caused a sensation and a search at the time, but there have been no real clues turned up since he was first reported missing. Majorana was shy, isolated, and occasionally depressed, and some people worried that he had committed suicide. Although it's possible, his family pointed out that he withdrew his entire savings account shortly before he took the trip. He was also, according to multiple sources, a devout Catholic, making suicide less likely for religious reasons. Some people say he left physics for the quiet life of the Church. Others believe that he had some ties to the mafia and was running from them - or murdered by them. The overall timing of the event is also suspicious. Europe, in 1938, was at the edge of a precipice. Physicists the world over would soon be engaged in one war effort or another. It's possible that Majorana was not interested in becoming part of that effort. Although at the time of his disappearance, no one had conceived that an atomic bomb was possible, some biographers have posited that Majorana was quietly a few steps ahead of everyone and wanted no part of what was to come.

Even the single concrete detail in the case, that Majorana stepped onto a certain boat on a certain day in March, is in dispute. Some believe he deliberately placed a decoy on the boat. Others think the boat trip was simply a fabrication of those he left behind, who naturally wanted some evidence to cling to.

Fermi, when discussing Majorana's disappearance, famously said, "Ettore was too intelligent. If he has decided to disappear, no-one will be able to find him." It looks like he may have been right.

Via Physics Central and the Cern Courier.