Outer space is a near-perfect vacuum, so you can't hear shit out there. That doesn't mean there's nothing to hear, though. Since antiquity, astronomers and philosophers have been speculating that the universe is actually singing to us—that the harmony of all otherworldly matter is just a symphony we can't hear.

The sonic perception of the galaxy has evolved with us, in fits and starts. Pythagoras got the ball rolling in a particularly galaxy-brained moment. Plucking a monocord, he realized for the first time (of any person, apparently) that the length of an instrument's string was inversely proportional to the pitch it produced, and that intervals between harmonious sound frequencies adhere to mathematical calculations. This insight inspired Musica Universalis, his proposition that the sun, moon and planets emit a unique hum.

Over two millennia later, Johannes Kepler took that ball and ran with it. In Harmonices Mundi (1619), he traced the real physical harmonies of planetary motion, based on his calculations of the differences between the angular speed of the six known planets. He interpreted this according to the tastes of the time. Where Pythagoras heard the universe humming, echoing the instruments of the age, Kepler perceived a renaissance symphony. Its sweet harmonies were inaudible to the human ear, but could be heard by the soul. Fueled by the Christian idea that art was a humble imitation of God's creation, Kepler posited that all human music had been inspired by the intricate motions of the universe—its arrangements inspired ours.

Five hundred years later, after centuries of dormancy, Musica universalis is coming full circle. Having installed mechanical eyes and ears in outer space, modern astronomers and physicists are starting to discern what songs the universe actually sings. Armed with raw data, their own galaxy brains, and the musical tastes and tools of the time, they are finally capturing the universe's instruments and arrangements for everyone to hear. Call it Space Jams.

The Planets sing Radiohead

Propelled by a National Science Foundation grant, astronomer Greg Salvesen spent two years exploring the creative potential of sonifying astronomical data — making his code and music available at AstroSoM. His experimental compositions can convey something as abstract as the magnitude of supernovae discoveries in the late 20th century (set to a sparse rendition of "Champagne Supernova"). Another song arranges saxophones in accordance with a black hole going into outburst — one of the few phases in which the universe's spookiest lurkers can be detected. The music of the universe is harrowingly beautiful. More importantly, perhaps, it renders outer space accessible in new ways to the visually impaired.

Salvesen draws on colleagues' data to build compositions from scratch, but also supports other researchers' efforts to develop their universal music. One notable effort was "Milky Way Blues," a sonification by Mark Heyer of UMass-Amherst to which Salvesen contributed visuals. For this interstellar opus, Heyer shifted radio telescopic measurements of the Milky Way's atomic, molecular, and ionized gases onto a minor pentatonic scale. In "Milky Way Blues," a different instrument plays each gas phase, and longer notes represent emission intensity. The resulting feel is one of an alien in a porkpie hat let loose on an old Casio synth. Salvesen's accompanying data visualization harnesses color and line to show where the telescope was pointed. It grounds listeners by depicting the position of our sun throughout.

With no roadmap in place for this type of exploration, these cosmic artists chart their own sonic path through the universe, forging distinctive styles. Matt Russo's elegant and emotionally resonant work ranks among the most immediately recognizable. The astrophysicist and jazz guitarist sonifies Saturn's rings and synching planetary orbits to natural harmonies that would've tickled Kepler.

In one composition, Russo revealed an epic, dark joke lurking at the center of our lives by speeding up the orbits of the terrestrial planets (and select asteroids) by 8 billion-fold. Leaning into the musical pitches and rhythms, he found that were we to lap the sun at such a frantic pace, we'd radiate "True Love Waits," aka Radioheads most depressing song.

Though it wouldn't be untrue to say the universe forged all of our big-F Feelings, fundamentally she remains neutral about us. These sonifications are driven by data. Her music tilts melancholic.

The Occasional Banger

Only once has the universe delivered a banger.

In 2001, physicist John Cramer wrote a paper on the sound of the Big Bang based on temperature fluctuations from NASA. Two years later, a fifth grader from Pennsylvania asked him if it was possible to actually hear those sounds. Though Cramer's paper wasn't meant to be read literally, he didn't wave the kid off. Instead, he reinterpreted NASA's temperature fluctuations from 380,000 to 760,000 years after the Big Bang. As the expanding universe cooled, the wavelengths of sound stretched and became more basslike, dropping 100 septillion times below the range of human hearing, which Cramer boosted.

The physicist's gut-liquefying soundscape of this period suggests we've spent the last 14 billion years recovering from a catastrophic dubstep show. After the Planck mission delivered superior data a decade later, Cramer released even more tracks, this time with richer tones in higher frequencies. "BigBangSound100" is liable to inspire divine panic attacks in listeners, and may just stress-test your apartment's earthquake-readiness.

For those needing a comedown after that seismic tune, there's astrophysicist Mark Neyrinck's signature easy listening. The Ikerbasque Fellow at the University of the Basque Country in Bilbao has been investigating the changing state of matter over time, including an "initial" and "Gauss" transformation, in visual and sonified form. He discovered that while the images were strikingly dissimilar, his sonifications of the same data were nearly identical.

"This is important because it gives an easy way to infer something of what the primordial universe was like, even though the gravitational evolution of matter since then has been extensive and complex. Here, sound actually communicates information that the eye does not pick up…I didn't think, at the time, that it would be so boring that it would put people to sleep! But I noticed the white noise-like sound."

Neyrinck uploaded the "Gauss" file, renamed "Intergalactic Voyage" to a popular white noise website. Alongside "Babbling Brook" and "Box Fan," the astrophysicist's data-driven composition has become one of the app's most popular tracks, racking up more than 27,000 downloads and 31.4 years of playback. Neyrinck's track takes listeners on a joyride through space at 9 billion light-years per second. The "noise" they hear comes from hitting intergalactic speed bumps made of dark matter. Most app users don't know that, though. They're just happy to zonk out.

Black Hole Humdrum

Astronomical data sonification fascinates in part because it satisfies human needs – colors and pitches and timelines scaled to fit our lives. When LIGO's ultra-sensitive observatories detected ripples in the fabric of space-time in 2015, the discovery inverted that status quo. Gravitational waves arrived primed for the ear — no sonification necessary.

As two massive black holes dervished together, violently merging, they released the energy equivalent of a billion-trillion suns, and generated gravitational waves, expanding and contracting the fabric of spacetime as they race across the universe at the speed of light. Had a human witnessed this black hole merger up-close, their ear would have vibrated as if sensing a sound. When the echo reached Earth in the year 2015 after a billion-year journey, it arrived weakened but still as an audible "chirp," and at a frequency within the range of human hearing.

LIGO’s interferometers were ready and listening for the black holes' plaintive cry. As soon as the first chirp was detected, a nearly hundred-year-old proof from Einstein's general theory of relativity came to life in the real world, as sound.

Though Greg Salvesen is on hiatus from creating new material for AstroSoM, he finds gravitational waves particularly tempting fodder for sonification, given how they demonstrate astronomy's broader shift from the eye to the ear.

He envisions mapping the chirps as a function of time, "like the same thing that I did with the supernovae [sonification]," he says. "As time goes on, how many of these are being discovered, and how our ability to discover these is growing exponentially. You can really get a feel for that with sound. I think that's something that sound really has as an advantage: it's to give you a feeling for the passage of time…You experience song and music in the time domain." And this is just the beginning. "It's like, 'Holy crap, we're discovering these like crazy now,'" says Salvesen. "When they were first discovered, it seemed so hard then."

These universal sounds and arrangements are still a niche interest, but the art-science nexus is always a step ahead of the market. Post-human music has always been one of pop's great aspirations. If these tunes come to us as naturally as Keppler once predicted, one could see these sonic discoveries inspiring new popular genres, or at least being sampled by The Neptunes.

Either way, exploring the universe by ear is a given now. After hundreds of years of progress, it's a curious function of time that these space sounds validate our forebears, and substantiate Einstein's theories as an afterthought. Leave it to Our Mopey Void to come through on her own schedule, and not with a bang, but with a whimper. ♦