In 1977, NASA launched the space probes Voyager 1 and Voyager 2 as part of a quest to explore the outer solar system and beyond. Attached to each spacecraft was a relic from the record store: a gold-plated LP filled with music and more.
The brainchild of astrophysicist Carl Sagan, these “Golden Records” remain one of mankind’s greatest attempts to communicate with extraterrestrials. The 12-inch discs contain “sounds and images selected to portray the diversity of life and culture on Earth,” according to NASA. If either spacecraft ever floats through E.T.’s backyard, this cosmic time capsule could tell his friends and colleagues everything they want to know about life on planet Earth.
Greetings From Earth
The Golden Record isn’t the first message humans have sent to alien civilizations. In the early 1970s, the space probes Pioneer 10 and 11 — later the first NASA craft to exit the solar system — launched with golden plaques depicting illustrations of a hydrogen atom, nude figures of a man and woman, and the location of Earth. Sagan, who helped with the Pioneer plaque project, described the illustrations as “a sort of message in a bottle, cast into the cosmic ocean, in case at some remote epoch in the future an extraterrestrial civilization were to come upon Pioneer 10 or 11 and wonder something about its origin.”
Also around this time, astronomers at the Arecibo Observatory in Puerto Rico used a radio telescope to broadcast a brief signal carrying information about DNA, numbers, and other basic elements of humanity.
A few years later, as NASA scientists worked on plans to launch Voyager 1 and 2, Sagan started thinking how to send a more sophisticated message. After all, the Voyager probes had a long journey ahead. They would examine the planets of Jupiter, Saturn, and Uranus — and then, eventually, they would float beyond the sun’s grasp. Why not take advantage of this long commute — and the unknown encounters it might bring — by stowing a new interstellar message aboard?
Music for the Cosmic Ocean
To create the record, Sagan put together a team of scientists, engineers, artists, writers, and producers. Among those he reached out to was Alan Lomax, one of America’s most respected ethnomusicologists at the time. In his letter, Sagan expressed his desire to send “music representative of all of humanity ... the best of humanity” into deep space. He further explained that the record could last a billion years: “Inclusion of the musical selections on the Voyager record ensures for them a kind of immortality which could not be achieved in any other way.”
Lomax eagerly agreed to help. He and the rest of Sagan’s team cast a wide net and selected a smorgasbord of world music, including panpipes from the Solomon Islands, folk music from Bulgaria, a selection of Australian aboriginal songs on didgeridoo, songs by pygmy girls in Zaire, polyrhythmic percussion from Senegal, a Navajo chant, and music of the shakuhachi (a traditional bamboo flute) from Japan.
The record also contained a selection of popular and classical Western music, including Chuck Berry’s “Johnny B. Goode,” Louis Armstrong’s “Melancholy Blues,” and several pieces by Beethoven and Bach.
In choosing the classical music pieces, the team sacrificed diversity to highlight the mathematical patterns of music. “[Aliens would] look for symmetries — repetitions, inversions, mirror images, and other self-similarities — within or between compositions,” Timothy Ferris, who helped produce the project, writes in The New Yorker. “We sought to facilitate the process by proffering Bach, whose works are full of symmetry.”
A Linguistic Buffet
Music wasn’t the only audio etched into the Golden Record. Sagan’s team archived sounds that they believed captured the essence of life on Earth: volcanoes bursting, thunder clapping, crickets chirping, dogs barking, sheep bleating, hearts beating. They dug up recordings of airplanes and trains and rockets, as well as the smack of a kiss, an EEG of brainwaves, and the cosmic chirp of a pulsar. There’s also a comical mix of whale song faded over the long-winded ramblings of a United Nations representative. (Ferris writes: “I’ll leave it to the extraterrestrials to decide which species they prefer.”)
Indeed, the Golden Record is not short on words: It contains a linguistic buffet of greetings in 55 languages. Some samples are ancient, with messages in Akkadian (the native language of the Mesopotamian empire) and Aramaic (the Syriac language spoken by Jesus). And there are dozens of samples of living languages, from Bengali and Dutch to Nepali and Welsh.
There's even a huge variety in the nature of the greetings. The English speaker (Sagan’s six-year-old son) says, “Hello from the children of Planet Earth,” while a person speaking the Amoy Chinese dialect asks the question, “Have you eaten yet?”
Pictures Worth a Thousand Words
The Golden Record is more than a simple LP, of course. It also contains more than 100 images.
Just as Sagan’s team wanted to capture the sounds of Earth, they also wanted to capture the sights of Earth, so they looked for ways to encode photos on the disc. (JPEGs and other digital formats did not exist at the time.) According to Cory Zapatka at The Verge, the team discovered that if they projected images onto a screen and recorded them with a camera, they could turn those signals into audio waves. “The reversal process — turning that image data back into images — is what any extraterrestrial (or curious human) would have to figure out how to do,” Zapatka writes.
Anyone smart enough to unlock these images will be treated to 115 photos of rush-hour traffic, sand dunes, snowflakes, trees with daffodils, dolphins, toads, trains, women breastfeeding, men running, the moon, Jane Goodall with chimps, and much more.
A How-To Manual
Sagan and his team knew it might be difficult for any extraterrestrial civilization to understand how to unlock these and other secrets buried within the Golden Record, so they made sure to include instructions.
On the record’s exterior is a circular drawing of the LP that shows how to work the stylus. In hopes that math and science transcends space and time, the team described the spin rate by laying out the formula in binary arithmetic. (Specifically, the units are expressed by 0.70 billionths of a second — “the time period associated with a fundamental transition of the hydrogen atom,” NASA says.)
In addition to these instructions, the Golden Record contains other etchings, including a depiction of the 14 neutron stars closest to Earth — essentially giving aliens a road map back to the record’s origins. And if any extraterrestrials are stuck wondering the age of the Golden Record, the answer to that question can be found in the composition of the disc: The cover of the record is electroplated with an ultra-pure sample of Uranium-238. This radioactive isotope has a half-life of 4.51 billion years, so extraterrestrials can use it to determine the record's age through radiometric dating.
As Sagan explained, “The spacecraft will be encountered and the record played only if there are advanced spacefaring civilizations in interstellar space. But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet."