by Kirsten Howard

It probably isn’t going to sync up with The Wizard of Oz, but this recording of strange “music” heard by Apollo 10 astronauts Eugene Cernan, Thomas Stafford, and John Young on the dark side of the moon was kept classified by NASA for over 40 years. Listening to it, you can perhaps understand why.

The 1969 mission involved 31 turns around the moon and on one trip, when the men found themselves out of range of any type of Earth-based broadcast, the eerie music began—and didn’t stop for a full hour.

“You hear that? That whistling sound?” asks one of the men, tentatively, on the declassified recording. “That music even sounds outer-spacey, doesn’t it?”

“That sure is weird music,” replies another.

The strange sound is so inherently unnerving that you can see why it could disturb even the most professional space adventurer, which might explain why the Apollo 10 team debated even mentioning it to NASA when they returned home.

The recording is finally making it into the public consciousness due to a new documentary series being aired on the Science Channel called NASA’s Unexplained Files. While a NASA technician brushes off any talk of alien phenomena with a simple explanation of radio interference between the lunar module and the command module, Apollo 15 astronaut Al Worden admits that if he had heard the same music up there it would have "freaked" him out.

“The Apollo 10 crew was very used to the kind of noise that they should be hearing," Worden says in the new series. "Logic tells me that if there was something recorded on there, then there was something there."

There’s also the matter of why NASA kept it secret for four decades, but we’ll reserve the tinfoil hats on that one for now.

You can now listen to the Apollo 10 recording for yourself below. We want to believe!