This story is over 5 years old.

The Wow! Signal Is The Strongest Candidate For an Alien Radio Transmission Yet

'Cosmos' didn't mention this mysterious radio signal in last night's episode, but it's still our best shot for an intergalactic chat sesh. For now.
A copy of the original Wow! signal printout. Image via The Ohio State University Radio Observatory and the North American AstroPhysical Observatory (NAAPO).

Every week, Becky Ferreira, your hostess with the cosmostest, hones in on the most important science and history topics the hit show Cosmos glosses over. Previously: What 'Cosmos' Left Out About Michael Faraday, Victorian England's Top Scientist.

Cosmos: A Spacetime Odyssey is really pulling out all the stops now that it's in the homestretch. Last night's installment, “The Immortals,” was the best episode of the reboot so far, in no small part because it was so Sagan-heavy. It even capped off with a passage from Pale Blue Dot, in which Sagan encourages his audience to continue reaching for a sustainable civilization on and off Earth. This is the kind of soaring, optimistic lyricism that made the original Cosmos the most widely watched PBS series in the world, and it was exciting to see it so unapologetically reprised last night.


Another major triumph of “The Immortals” was the evocative central conceit: the comparison of our own biological code—“written by nature and edited by evolution,” as Neil deGrasse Tyson put it—to the many permutations of the “Hero's Journey.” In other words, just as nature selects the fittest genes for each environment, humans select the best storytelling tropes for each culture. Stories, like species, reproduce and mutate over the ages, evolving new appendages and adaptations to survive the changing times.

The episode used the world's first confirmed author, the high Uruk priestess Enheduanna, as the poster girl for how ancient tales can germinate afresh many millennia after they were first penned (in Enheduanna's case, it's about 4,200 years and counting). Since this Cosmosnaut column is dedicated filling you in on the gems Cosmos leaves out, it would be remiss of me not to mention that Enheduanna wrote one of the greatest opening lines in literature: “peg my vulva.” The hymn gets even better from there. There's a reason we still know Enheduanna's name today—the woman knew how to write hooks that could (and did) edge out her competition.

From the Uruk segment, the episode segued into Tyson's speculation that life could be its own kind of narrative arc, that reproduces in a biological chain reaction across the galaxy and leads to cultural exchanges between alien worlds. Earth, for example, has been “radiating stories” for the past 70 years, which means that by now, hundreds of planets have been bathed in our radio-wave babbling. It raises the question: are we awash in the stories of extraterrestrial worlds too, but too primitive to decode them?


That is one of the most tantalizing possibilities ever conceived, though Tyson was right to stress that our pursuit of alien intelligence is still in its infancy. Even so, it was surprising that the show didn't mention the “Wow! Signal,” which is the heftiest crumb ever tossed to the Search for Extraterrestrial Intelligence (SETI). This idiosyncratic narrowband radio signal was picked up by the Big Ear telescope on August 15, 1977, and its origins have been puzzled over ever since.

Location of the Wow! signal on a star map. Image via Benjamin Crowell.

Perhaps the episode didn't want to touch the Wow! signal because its meaning is still murky, but it's worth pointing out why this radio burst sticks out from most of the junk SETI captures in its telescopes. Most importantly, the signal was resonating at 1420 MHz, right on the fabled hydrogen line. Astronomers have nicknamed this frequency “the waterhole,” both because hydrogen is the major component for water and because, as Skeptoid's Brian Dunning puts it, the line is “nature's gathering point on the radio spectrum, a blatantly obvious place for interstellar communities to meet and greet.”

In fact, the hydrogen line is considered such an obvious candidate for extraterrestrial transmissions that scientists have made it a “protected spectrum.” Only astronomical research is allowed to be conducted at this frequency, which is one of many reasons why it is extremely unlikely that the Wow! signal originated on Earth.

This, combined with the signal's shifts in intensity over the 72 seconds for which it was recorded, support the conclusion that the signal originated somewhere near the Chi Sagittarii star group. “If we ever do receive a deliberate alien transmission, Wow! was exactly what we'd hope and expect to find,” said Dunning on Skeptoid. The big problem? The signal has never been repeated, and if those aliens are anything like humans, punctuated silence is not exactly a strong point.

But perhaps anthropomorphizing aliens this way is the problem, and we should look for a different kind of story in the stars. SETI has brainstormed all kinds of other smoking guns that might suggest advanced intelligence. Maybe Dyson swarms have been erected around distant suns, which would alter their spectrums significantly from our perspective. Maybe we'll detect polluted skies, megastructures, or other abnormalities suggesting the presence of intelligent life. Frustratingly, all we can do is keep looking.

Tyson's speculation that alien transmissions may be bouncing off our dumb faces every day of our lives is not a new idea, but it feels fresh every time it's restated. We may never know if the Wow! Signal was a message from an alien species, or an outburst from a natural source that coincidentally hit the hydrogen line. But in 2012, at least we made sure to write back. In a joint project between the Arecibo Telescope and the National Geographic Channel, thousands of messages, including one from Stephen Colbert, were beamed to Chi Sagittarii.

The project might be quixotic, and we won't live to see the payoff for many hundreds of years (unless we hack our genes in time—fingers crossed). But if the thoughts of a Uruk priestess can survive for four millennia, it doesn't seem totally insane that two civilizations could exchange greetings over the course of a few centuries. Regardless, let's hope that the first aliens we make contact with are at least as bawdy as Enheduanna.