Ann Druyan's brainwaves ride Voyager into interstellar space

On a June afternoon in 1977, a 27-year-old woman lay on a hospital table in New York while machines converted the electrical firing of her brain into sound. Her name was Ann Druyan. Two days earlier, she had agreed by telephone to marry Carl Sagan, the astronomer who had recruited her as creative director of an audacious project: assembling a message to the cosmos that would ride aboard two spacecraft headed for the outer planets and beyond. That compressed minute of her brainwaves—captured while her thoughts drifted across Earth's history, across continents and civilizations, across the man she had just promised to marry—was pressed into gold-plated copper and bolted to the side of Voyager 1 and Voyager 2. It is now more than 25 billion kilometres from Earth, still travelling.

The team had less than six weeks. Sagan, working with astronomer Frank Drake, writer Timothy Ferris, artist Jon Lomberg, and Druyan, faced a launch window that would not move. They argued over what humanity should sound like from the inside, what music might survive a billion years, what images could be encoded into an audio groove so that a civilization with no shared reference could reconstruct them. The folklorist Alan Lomax, working from New York, selected most of the field recordings. The result was a 12-inch phonographic disc carrying 115 encoded images, greetings in 55 languages, and a curated tour of terrestrial sound: a Georgian men's chorus, Blind Willie Johnson, Bach's Brandenburg Concerto, Mozart, Louis Armstrong, Chuck Berry's Johnny B. Goode, honkyoku shakuhachi, the sound of a kiss, a mother speaking to her newborn, thunder, surf, a chimpanzee, and a humpback whale. Between the label and the grooves, Ferris had etched a phrase directly by hand: "To the makers of music – all worlds, all times."

The idea to include Druyan's brainwaves was hers. She had asked Sagan whether a civilization a billion years from now could conceivably read her thoughts from an EEG recording. He did not know. He suggested they try anyway. She booked a laboratory at Bellevue Hospital where a technician captured an electroencephalogram, an electrocardiogram, eye movement, and other bodily signals across a single hour. She went in with a script, trying to hold a mental itinerary of Earth's history in her head—the movement of continents, the rise of civilizations, the invention of writing. Her thoughts drifted. Years later, writing in the epilogue to Sagan's Billions and Billions, she described entering the laboratory hooked to a computer that turned the data from her brain and heart into sound. She said her feelings as a 27-year-old woman, madly fallen in love, were on that record, and that the permanence of it, on a timescale of a hundred million years, was the part she found hard to be afraid of.

An EEG measures voltage differences between electrodes placed on the scalp—typically in the range of microvolts, oscillating at a few cycles to a few dozen cycles per second. It records the aggregate behaviour of large populations of neurons, not thoughts. To fit an hour of signal onto a record with finite groove length, the recording was heavily compressed. What plays back is a burst of crackle and pulse with no intelligible content in it at all. There is no way to extract Druyan's actual thoughts from the disc. The signal is too coarse, and it was never a transcript to begin with. What survives is the fact of a nervous system, doing what nervous systems do, on a particular afternoon in June 1977. We know what that minute meant only because Druyan later told us.

Voyager 1 crossed into interstellar space in 2012 and is currently the most distant human-made object. NASA's mission tracker puts it past 25 billion kilometres, closing on a threshold it will cross in November 2026, when it becomes the first object built by humans to sit a full light-day from Earth. Voyager 2 crossed the heliopause in 2018 and trails behind. Both spacecraft are still transmitting on plutonium-238 radioisotope generators whose output falls a little each year, and NASA has been shutting down instruments to conserve the shrinking power budget. The spacecraft themselves will eventually fall silent. The records will not. Gold-plated copper, in the near-vacuum of interstellar space, has no obvious mechanism of decay on any timescale that matters to human civilization. Micrometeoroid strikes will pit the surface over millions of years, but the information will remain readable for a very long time. The object was designed to outlive not only the spacecraft but plausibly the civilization that made it.

There is no way to verify that any of it will be found. The nearest star to Voyager 1's current trajectory is a red dwarf called Gliese 445, and the spacecraft will pass within about 1.6 light-years of it in roughly 40,000 years. Neither is a close approach in any meaningful sense. The odds of interception are effectively zero across any period a human being would care about. The record is not really an experiment. It is a gesture whose meaning is fixed on the sending end. The committee could have stopped at greetings, music, and images. The decision to include a physiological recording reflects a specific intuition Sagan and Druyan held about what a message to another mind should contain. Language would probably be unreadable. Music might be unrecognisable as music. But the electrical activity of a working brain is a physical signature that any technologically capable civilization would, in principle, be able to identify as the output of a nervous system. Most of what went onto the record was chosen to represent humanity in the aggregate: many languages, many musics, many faces. The brainwave is the exception. It is one specific 27-year-old woman on one specific afternoon in June 1977, thinking about one specific man she had agreed to marry two days earlier. Sagan and Druyan married in 1981 and stayed together until his death in 1996. The personal layer inside the record was known to the team at the time but not widely publicized until decades later. What is up there, exactly, is a 12-inch gold-plated copper disc carrying Bach, whale song, thunder, greetings in Akkadian and Mandarin and Wu, the sound of a kiss, a mother and child, a line scratched by hand to the makers of music in all worlds and all times, and—encoded near the end—the compressed electrical activity of a young woman's brain during the hour she was thinking about the man she had just agreed to marry. It is currently moving away from the Sun at roughly 61,000 kilometres per hour. It will keep going long after the transmitter goes dark, long after the last engineer who worked on Voyager is gone, and long after the Cornell office where the arguments happened is no longer standing. Somewhere out past the heliopause, in the dark between stars, a minute of a June afternoon in 1977 is still travelling.