The English rock band Pink Floyd released the album Dark Side of the Moon in 1973. But four years earlier, in 1969, NASA astronauts on the Apollo 10 space mission heard what sounded like outer-space music -- from the dark side of the moon. And nearly 50 years later, those mysterious noises on Apollo 10 have become a trending topic on social media. In May of 1969, the Apollo 10 crew approached the far side of the moon. The three astronauts, Thomas Stafford, John Young, and Eugene Cernan, would have no contact with the Earth. But just as they approached the far side of the moon, the crew heard strange “music.” That music even sounds outer-spacey, doesn't it? Do you hear that, that whistling sound? Yeah. That was the conversation between astronauts Eugene Cernan and John Young after hearing the strange sounds. The story of the unusual space noises will appear on a television series called NASA’s Unexplained Files.