The story of the Apollo 10 astronauts hearing weird “spacey music” while orbiting above the far side of the moon has been bouncing around the Web the past week. In case you haven’t heard, back in May 1969, when the Apollo 10 crew performed a dress rehearsal for the upcoming Apollo 11 moon landing, they were surprised to hear strange sounds in their headsets during the hour they orbited around the lunar backside.
Apollo’s weird “moon music” was radio interference
Lunar module pilot Gene Cernan described it as “outer-space-type-music”. I hear a harsh whine, but in different versions of the voice transcripts there’s an occasional softer “whooshing” noise in the background. The sound begins when astronauts Tom Stafford and Gene Cernan, in the lunar module, separate from John Young in the orbiting command module during a trial separation and docking run of the two spacecraft.
Now we know that what they heard was interference between the radios in the two craft. The Apollo flights took place in the days of analog VHF (Very High Frequency) radios. Signals from each radio mix with one another under the right circumstances to produce tones in the range of human hearing. Folks familiar with the technical side of radio wave transmission call it ‘heterodyning’. Apollo 11 astronaut Michael Collins heard it, too when Neil Armstrong and Buzz Aldrin departed the command module to land on the moon.
Although the full report on the incident has been publicly available since 1973 at the National Archives, NASA got around to digitizing the transcript and uploading it in 2012. Last Sunday, the space music story broke on the cable channel Discovery as part of their “NASA’s Unexplained Files” series. I’ve included their video as well. It uses special visual and audio effects and a slightly disturbing soundtrack to conjure an air of the unexplained. Just remember, it’s TV. In the end, the creators provide the prosaic explanation.
“NASA’s Unexplained Files” take on the spacey music
No doubt about it the astronauts’ ears stood up when they heard it, and the sound probably seemed all the more strange because they were around the lunar far side, where the spacecraft is temporarily out of communication from Earth. When you envision the far side, just remember it’s not dark. The far side goes through phases identical but opposite those we see on the nearside. But because the moon rotates around the Earth in the same time it takes to turn on its axis, we’re stuck with seeing only one side. It’s likely the astronauts were in full sunlight during their maneuvers.
So why didn’t the astronauts talk about the sounds? Why did we have to wait a few years to read about it? In the video/audio you can hear them ask each other whether they should bring it up. The reason they didn’t probably had much to do with the “right stuff” attitude at the time. Anything that might jeopardize an astronaut’s chance for a moon or other future mission — including talk about hearing weird noises — was kept quiet. Pressure was intense at the time to be as fit as possible both mentally and physically.
Still, an interesting aside in the grand story of humankind’s first visit to another world.