Astronauts from Apollo 10 and Apollo 11 reported hearing eerie “space music” while orbiting the Moon, despite space being a vacuum where sound cannot travel. The Apollo 10 crew—Thomas Stafford, John Young, and Eugene Cernan—first heard the strange whistling noise in May 1969 while on the Moon’s far side. Months later, Apollo 11 astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins experienced the same phenomenon. NASA later explained that the sounds were likely caused by interference between the lunar and command modules’ VHF radios. Collins noted in his book that had he not been warned, the noise would have been terrifying. The recordings remained buried in NASA’s archives for decades.