People love to think of history as a collection of established facts, but that’s far from reality. Even after decades or centuries of research, some of the biggest questions about the past still don’t have clear answers. Here are 15 things even history’s biggest nerds can’t agree on. Despite its connection to Pharaoh Khafre, some researchers believe the monument could be much older than traditionally accepted. The pioneering aviator disappeared over the Pacific in 1937, and no definitive explanation has ever been proven.