The Golden Record was never meant for this planet. Yet it has remained an object of curiosity on Earth, even after decades of hurtling through the void of outer space.

In fact, the Golden Record has had something of a revival lately. For years, there’s been talk of making a modern, internet-crowdsourced follow-up to the original 1977 version. The original record plays a prominent role in the new young-adult novel, See You in the Cosmos, by Jack Cheng. And a recent Kickstarter campaign to reissue the record on vinyl raised nearly $1.4 million, seven times more than its fundraising goal. Last fall, around the time that Kickstarter campaign launched, I found myself revisiting the record’s tracks.

In doing so, I stumbled upon a mystery.

* * *

In the late summer of 1977, NASA launched twin spacecrafts—Voyager 1 and Voyager 2—as part of a mission to better understand Jupiter, Saturn, and the outer solar system. As a bonus: Each probe carried a gold-plated copper phonograph that contained sounds and images from Earth. The idea was to send something into the universe that demonstrated humanity’s wish to join a “community of galactic civilizations,” as President Jimmy Carter put it at the time, and to express good will to intelligent life elsewhere. It was also meant as a cosmic postcard, of sorts, a way of sharing the experience of living on Earth with intelligent life elsewhere.

The record, curated by a team led by the astrophysicist Carl Sagan, featured the music of Beethoven, Chuck Berry, Kesarbai Kerkar, and Blind Willie Johnson, and various folk music from around the world. Images, placed electronically on the phonograph, included photographs of a mother nursing her baby; a woman with a microscope; an astronaut in space; highway traffic in Ithaca, New York; the pages of an open book; a violin with sheet music; men laying bricks to build a house in Africa; a woman eating grapes at a supermarket; and a number of diagrams and illustrations of concepts like continental drift and vertebrate evolution. There were also audio clips depicting scenes of life on Earth—the sounds of rushing wind and the roar of ocean tides, whale songs, elephants trumpeting, human footsteps and human laughter.

It occurred to me last fall that I’d never actually heard the laughter track—and that I wanted to. What sort of laugh did the record’s producers select as a depiction of our species? And whose laugh was it? It could have been a chuckle, a snort, a guffaw, a snicker. It could have been anything from the irresistible staccato of a baby giggling to a the deep-throated mwahaha of a Hollywood villain. But my idle curiosity led me to more and more questions, and those questions turned into a months-long investigation into the origins of the Golden Record.

The cover of the Golden Record features instructions on how to play it and illustrations depicting how it was made. In the upper left-hand corner, the record itself is depicted with a stylus is in the correct position for anyone who wants to play the record from the beginning. (NASA)

The contents of the record have been debated for decades—among its creators, certainly, but also among Golden Record enthusiasts. The project posed an impossible cultural and technological challenge to begin with: How do you carve an entire planet into the grooves of a single record—a record that’s also lightweight enough to piggyback  onto a 1970s space probe—all while capturing the richness of the human experience? Oh, and by the way, please make the whole thing potentially comprehensible to the alien civilization that might discover it 100 million years from now.

The team that conceived of the project first envisioned it as a record to be played at the conventional 33 and one-third revolutions per minute, with music on one side and non-musical information like photographs on the other. Eventually, they settled on 16 and two-thirds revolutions per minute—which meant a slightly lower quality sound, but not terribly so. The slower speed also meant they’d have 90 minutes available for music rather than the original 27 minutes.

The 12-minute audio essay that included the sounds of waves, elephants, and laughter was meant to capture the auditory experience of life on our planet. Those sounds were organized as a montage echoing the evolution of life on Earth—beginning with a “giddy whirl of tones reflecting the motions of the Sun’s planets in their orbits,” as the record’s creative director, Ann Druyan, put it in her 1978 essay about the project. Those ethereal notes gave way to sounds of an earthquake, thunder, mud pots, wind and rain, crickets and frogs, hyenas, birds, chimpanzees, and eventually humans. The first appearance of a human in this montage is the sound of footsteps, then laughter. That laugh is the first human utterance in this representation of the evolution of our species. This is fitting.

“Laughter is ancient,” says Robert Provine, the author of Laughter: A Scientific Investigation. “Laughing, like crying, is a human instinct. It’s not under conscious control. Whereas crying is a solicitation of caregiving, laughter is the signal of play. It is the sound of play, literally.”

Laughter is one of humanity’s most joyful peculiarities. Infants typically laugh long before they can speak. Laughter transcends differences in language entirely, yet remains a deeply important element of cultural and social interaction. Humans aren’t the only creatures that laugh—a chimpanzee’s laugh sounds like a dog panting; a rat laughs in ultrasonic chirps—but the rhythm and cadence of human laughter is unique to us. Humans also know, without really realizing, exactly what laughter sounds like. It’s a signal of play that we know immediately when we hear it, characterized by short bursts of sounds that last about one-fifteenth of a second and repeat in intervals each fifth of a second, Provine told me.

Selecting the right laughter for the Golden Record would have been less fraught, presumably, than selecting which language to feature on the record. Indeed, the language question created all sorts of difficulties. Sagan had suggested a day or two of recording at the United Nations headquarters in New York City, where delegates from each member nation might record a “hello” in their native language. “I had hoped that something like half of the voices could be male and half female, in order to reflect the distribution of sexes on the planet Earth,” he wrote in Murmurs of Earth, a book about the project published in 1978. “I was told that this was quite difficult on entirely other grounds. Virtually all the chiefs of delegations were male, and it was unlikely that they would delegate the privilege of saying ‘hello’ to the stars to anyone else.”

And so laughter, for all its complexities on Earth, was simpler to represent than language on the Golden Record. Except, when you listen to the “Footsteps, Heartbeat, Laughter” track of the “Sounds of Earth” audio that’s on the Voyager website—or to the version uploaded by NASA to Soundcloud—you won't actually hear any laughter. What happened to it? And whose voice is supposed to be there? I started to ask around.

“You are right that on the Voyager website there is a 30-second clip of a heartbeat and footsteps but not laughter,” a staffer at NASA’s Jet Propulsion Laboratory told me in an email when I asked what had happened. “Indeed, the NASA Soundcloud also has the same clip.” But there was a version of the recording where you could clearly hear the laughter, the staffer told me, on a website hosted by the Massachusetts Institute of Technology. NASA couldn’t verify the authenticity of that recording, but it was a start.

I listened, and there it was. The laughter is secondary to the heartbeat and footsteps. It starts low then tapers off into a light cackle. It sounds genuine, like the person is truly delighted by something. It only lasts a few seconds.

The laughter was there—but was this version of the Golden Record legitimate? My attempts to contact the website’s maker yielded little. The audio on the site originally came from the Library of Congress, I was told, but Library of Congress staffers couldn’t tell me for sure whether it was the same as the copy they had. (Nor did the Library of Congress have any additional information on the identity of the laugher.) Eventually, an archivist at the JPL was able to send me a sound file containing all 21 tracks from “The Sounds of Earth.” This was the official recording, but much better quality than what NASA had put online. It sounded just like the version on the MIT site—the crunch of footsteps, a steady heartbeat, and then the welling up of laughter. (Start around the 6:10 mark to skip right to the laughter in the audio-player embedded below.)

But that still didn’t solve my original question of whose laughter was on the record, or the question of why it had disappeared from the other official recordings. I couldn’t find anybody who could answer either question.

Not NASA, not the Library of Congress, not the Carl Sagan Institute at Cornell, where Sagan was a professor, and not NASA’s Jet Propulsion Laboratory. “JPL-Caltech was not involved in the creation of the audio recordings on the Voyager Golden Record,” a spokesperson there told me, “and has no knowledge of the identities of the persons recorded or those who did the recording.”

The official book about the Golden Record, Murmurs of Earth, contains a trove of fascinating background about the making of the record—including the painstaking process of gathering audio for the Sounds of Earth section—but there’s nothing in it about whose laugh is featured. I tried to arrange a time to speak with Ann Druyan, the producer and filmmaker who spearheaded audio collection for that portion of the record, but I couldn’t reach her. (Druyan and Sagan worked closely on the project, and later married.)

So I started contacting people listed in the “acknowledgements” section of Murmurs to see if anyone could remember. Nothing.

“I wish I could help you... but I don’t know,” wrote Lise Menn, a linguist and professor at the University of  Colorado who is listed in the book as having provided audio for the mother-and-child track. “I’m not even sure whose voice is on the mother-and-baby segment, although it may have been from [the linguist Margaret] Bullowa’s files—I was her assistant. If Dr. Druyan doesn’t know, I think we’re at a dead end.”

Fall turned to winter, winter to spring, spring to summer. It seemed that my mystery would remain unsolved. Meanwhile, the Golden Record was gliding ever farther into space, receding from our planet at 35,000 miles per hour. The two Voyager probes are now nearly 14 billion miles and 11 billion miles away from Earth, respectively. “Out there, our concepts of velocity become provincial,” Timothy Ferris, one of the record’s producers, wrote 10 years ago, anticipating the moment at which the space probe Voyager would tip across the threshold to interstellar space. That finally happened in 2014. At the time, Ferris described Voyager as a toy boat on a dark sea of stars swirling in “gigantic orbits around the center of the Milky Way galaxy.” He isn’t the first to evoke maritime comparisons. In 1986, the astronomer William Gutsch described Voyager as “a bottle cast by its creators, adrift on a cosmic ocean.” The Golden Record was a message in that bottle.

The people who made the record believed that, in the vacuum of space, it could remain in working condition for a billion years. The capsules protecting the records were configured in such a way, Sagan once wrote, that “all of the pictorial information, human and cetacean greetings, and ‘The Sounds of Earth’... will survive essentially forever.”

“If I had to guess, I’d say it’s as fresh and new as the day it was placed aboard the spacecraft,” David Doody, an engineer on the Voyager mission at NASA’s Jet Propulsion Laboratory told me a few years ago. “It’s been stored in a vacuum more perfect than any attainable on Earth, and protected from dust and cosmic rays by an aluminum metal case.”

Out there in space, the record swims onward through the stars. Back here on Earth, despite people’s enduring fondness for the project, little bits of context are vanishing. The answers to my questions about the laughter on the Golden Record seemed destined to be lost to time.

Then, two days ago, I received an unexpected message from someone at the Jet Propulsion Laboratory. “I met Ann Druyan today,” the lab’s Elizabeth Landau told me, “and she told me that the laughter on the Golden Record is Carl Sagan’s!”

I made half a dozen phone calls and sent out a flurry of emails—to the Golden Record’s producers, to NASA, to Druyan, to Sagan and Druyan’s children—all in an attempt to corroborate the account I’d received.

Carl Sagan stands with models of planets in 1981. (Eduardo Castaneda / Library of Congress)

Was the laughter indeed Sagan’s? It certainly seemed plausible, but I had to be sure. Finally, I reached Sasha Sagan, the daughter of Carl Sagan and Ann Druyan.

“I just double checked with my mom to be absolutely sure, and yes, it is indeed my dad’s laugh!” Sagan wrote. “She said that laugh was the very first impression she ever had of my dad when she heard it upon entering Nora Ephron’s apartment [where they first met] in 1974, and included it in the Voyager sound essay because she wanted it to live on forever.”

The Golden Record has always been a love letter to humanity, and a love letter to the cosmos, but it’s also quite clearly a love letter between Druyan and Sagan, too. Druyan has said as much in past interviews when she’s described the afternoon she spent meditating at Bellevue Hospital. She went there to have electrodes attached to her body so a machine could register the pattern of electrical impulses in her brain and nervous system. The data from that session was etched onto the Golden Record, the idea being that some future, alien civilization might be able to convert EEG data back into comprehensible thoughts.

“This was two days after Carl and I declared our love for each other,” Druyan said in a radio interview years ago, “and so part of what I was thinking in this meditation was about the wonder of love, and of being in love. And to know it’s on those two spacecrafts... Now, whenever I’m down, I’m thinking, still they move, 35,000 miles an hour, leaving our solar system for the great wide open sea of interstellar space.”

It’s a cosmically romantic story. And if it sounds too good to be true, the Golden Record producer Timothy Ferris told me, that’s because he suspects it might be. “This is news to me,” he told me. He remembers Sagan’s laugh clearly, he said. “It doesn’t sound like what’s on that track. He had a great laugh. He had a good sense of humor.”

I wrote back to Druyan’s daughter to see what she thought. Was there even a chance Druyan was mistaken? Human memory is fallible, Druyan acknowledged in response via Sasha Sagan. It’s been 40 years since they made the Golden Record, and more than 20 years since Sagan died in 1996. But Druyan is quite certain about Sagan’s laughter and its place in the universe. “It’s highly unusual, virtually unique,” she said in an email via her daughter. “I chose it because of its exceptional lack of inhibition and because it was Carl’s.”

This morning, I went back and listened to the NASA file on SoundCloud and realized something else: It turns out the laughter is there, only it’s barely perceptible. Without hearing the better-quality version of the recording first, it’s next to impossible to register. “I've heard how bad the online versions are,” Ferris told me. It’s not clear why the version on NASA’s SoundCloud is so low-quality compared with the pristine audio in its archives.

The laughter is so faint. It’s mostly lost in the static. Billions of miles away, though, the original Golden Record is out there, still in mint condition. Which means Sagan’s laughter—if it is indeed his—may yet be heard in some faraway galaxy, by some species we cannot imagine. But that’s a mystery for another time.