People vanish all the time, and we usually find out what happened to them eventually. Usually, not always. Jimmy Hoffa and Amelia Earhart are the most famous unsolved missing persons cases in the modern era. But there are many others who left us with far more questions than answers. Here are six you may not be familiar with.

Percy Fawcett

Colonel Percy Fawcett was a British citizen who became a worldwide adventurer. He is thought to be one of the inspirations for the character of Indiana Jones. On several expeditions to South America, Fawcett became intrigued by the legends of a lost city, which he called Z. Over time he became obsessed with the idea of setting up a commune in the lost city where he own son would be a deity. In 1925, he led an ill-equipped expedition into the Mateo Grosso jungle in Brazil. None of the group was ever seen again. There are many possible explanations: death by illness, wild animals, or hostile tribes, or they may have just become hopelessly lost. Some theorize they were abducted by aliens or ended up in an underground kingdom. Some believe Fawcett lived out his life in an isolated tribe.

Glen and Bessie Hyde

Glen Hyde and Bessie Haley were married in 1928. For their honeymoon, they set off in a homemade boat on the Colorado River. Bessie was to be the first woman to ride the Grand Canyon. Their boat was found about a month later, but the Hydes were never seen again. Some think that they capsized in the rapids and drowned, but no trace of their bodies were found. Others believe that Bessie killed Glen and started her life over elsewhere.

Judge Crater

Joseph Force Crater was a justice on the New York state Supreme Court and was associated with organized crime. It was suspected that he was appointed to the court due to his involvement with the corrupt Tammany Hall Democratic organization. He left his wife at their summer home in Maine on August 3rd, 1930 to go to New York City on business. He was last seen at a restaurant on August 9th. Judge Crater hailed a taxi and was never seen again. The taxi was never traced. A search began on August 25th, when Crater did not show up for work. Some think that Crater fled the country to avoid trouble with authorities or the mob. His wife Stella insisted that he must have been murdered, but no conclusion was ever reached.

Ettore Majorana

Ettore Majorana was an Italian theoretical physicist who worked with both Werner Heisenberg and Neils Bohr. Majorana began to develop a theory of neutrino masses while still in his twenties. Around 1933, he began suffering from illness and became a recluse. In 1937, Majorana was appointed a full professor at the University of Naples just a few months before his disappearance. He was only 31 years old in 1938 when he vanished during a boat trip from Palermo to Naples. Suicide, murder, and voluntary disappearance are all possibilities, but no one knows for sure.

Lloyd L. Gaines

Lloyd L. Gaines applied for admission to the University of Missouri's law school in 1935, but was rejected because he was black, and the state's laws did not support integrated education. With the help of the NAACP, Gaines appealed his rejection all the way to the US Supreme Court. The case, heard in 1938, was the first ever to address educational opportunities for African-Americans. The Court found for Gaines, and ordered Missouri to admit him or find a comparable law school within the state in which to place him. The state hastily put together a "separate but equal" law school in St. Louis. Gaines and his team from the NAACP were prepared to argue that the new school was anything but comparable to the University, but Gaines did not show up for the court hearing. He was last seen on March 19, 1939 in Chicago. He had told some people at the fraternity house where he was staying that he was going out to buy stamps. No trace has ever been found. Gaines was granted a posthumous honorary law degree from the University of Missouri in 2006.

Sean Flynn

Sean Flynn was the son of actor Errol Flynn, and a photojournalist who covered the war in Vietnam. He and another photojournalist, Dana Stone, were captured by communist fighters in Cambodia and were never seen again. At least one source says Flynn was executed after a year in captivity. He was declared dead in 1984.

In researching this article, I found many other stories that you may soon see in a followup.