Posted by The phrase “message from aliens” arrives with a Hollywood image attached: a voice, a countdown, somebody going pale in front of a console. What the search actually produces is stranger and a great deal duller – a line of characters on a paper printout, a smear on a frequency plot, a candidate number in a database. Two of those candidates became famous. One is still unexplained after nearly fifty years. The other looked almost perfect for a while and then came apart under examination, which is exactly what was supposed to happen to it.
Six Characters in Red Ink
On 15 August 1977 the Big Ear radio telescope at Ohio State University was doing what it did every night: nothing, mechanically, while the Earth turned underneath it. Big Ear had no dish you could steer. It was a flat reflector the size of a couple of football fields, built largely of aluminium and plywood on an old golf course, and it surveyed the sky by waiting for the sky to walk past it. Its output went to a line printer, one character per 12-second sample, and somebody read the paper days later.
That somebody was Jerry Ehman, a volunteer with no salary attached to the project. Running down the stack he hit the string 6EQUJ5, circled it in red pen, and wrote one word in the margin. Wow!
The characters encode intensity. The signal climbed, peaked at roughly thirty times the background noise, and fell away over 72 seconds – precisely how long a fixed point on the sky takes to drift through Big Ear’s beam. It was narrowband, sitting close to 1420 MHz, where neutral hydrogen radiates and where SETI researchers had long argued was the obvious place to listen. It came from the direction of Sagittarius. Everything about it looked like a source out there rather than one down here.
Except for one detail that still bothers people. Big Ear watched through two feed horns aimed at slightly different parts of the sky, so a real celestial source should have registered twice, minutes apart. The Wow! signal showed up in one horn only, and the recording system did not label which.
Why It Never Came Back
The obvious move was to look again. Ehman went back to that patch. Robert Gray spent years on it, with the META II array in Argentina and later the Very Large Array in New Mexico. Others pointed Green Bank at it. Nothing has ever appeared there again, at that frequency or any other.
Big Ear itself was demolished in 1998 so the golf course could expand, which is a genuinely absurd end for the instrument that produced the most cited candidate in the history of the field.
A 2017 proposal blamed a passing comet’s hydrogen cloud. Radio astronomers took it apart quickly: comets do not radiate in a narrow band like that, and nothing similar has been seen from any comet since. Ehman himself kept leaning toward a terrestrial transmission bounced off something in space, while admitting he could not demonstrate it. One detection, never repeated, is not evidence of a message from aliens. It is an anomaly with a good story.
The Candidate Called BLC1
Skip forward. Breakthrough Listen, launched in 2015 with a hundred million dollars behind it, bought observing time on Green Bank and on the Parkes telescope in New South Wales, and began working through nearby stars at a rate the old surveys could not have managed. In April and May 2019, Parkes – known by its Wiradjuri name Murriyang – spent about thirty hours on Proxima Centauri, mostly to watch the star flare.
The flare data got processed. A year later an undergraduate intern, Shane Smith, was combing the archive and found a narrow tone near 982 MHz. It drifted slowly in frequency, the way a transmitter on a moving object should. It appeared when the dish was on Proxima and vanished when the dish nodded away, and it sat in a band with no known satellite traffic. Internally it became Breakthrough Listen Candidate 1.
Word leaked to the press in December 2020, briefly making BLC1 the closest thing to a message from aliens anyone had on file. The team kept working anyway, and the results came out in Nature Astronomy in October 2021.
It was interference. Buried elsewhere in the same data the analysts found a family of look-alike signals with the same drift behaviour, spaced at intervals that pointed to the harmonics of common electronic oscillators – the kind of thing that sits inside consumer equipment. The drift direction was also wrong for a transmitter riding on a planet around Proxima. Somebody’s hardware, within a few hundred kilometres of the dish, had produced a nearly textbook fake.
That is the part worth sitting with. BLC1 is not an embarrassment. It is the only time the full verification machinery has ever been run at speed on a serious candidate, and the machinery worked.
What Has to Survive Before Anyone Says It Out Loud
The core test is embarrassingly simple: point away, then point back. A source fixed on the sky reappears. Local interference usually does not care where the telescope is aimed. After that come the drift-rate checks, since a transmitter on a rotating, orbiting planet imposes a specific Doppler signature, and anything that fails to move at all is suspiciously well behaved.
Then the candidate has to travel. Independent observatory, different receivers, different software, ideally a different continent. Radio astronomy has been fooled by its own equipment often enough to insist on this. Jocelyn Bell Burnell’s team half-jokingly filed their first pulsar as LGM-1 in 1967 before working out it was a neutron star. Parkes spent seventeen years chasing bursts called perytons before somebody noticed in 2015 that they came from opening the visitors’ centre microwave oven early.
There is a written protocol too, drafted in 1989 by the SETI committee of the International Academy of Astronautics and revised since. Verify before announcing, tell the astronomical community, publish the data, and – the clause that matters most – send no reply on behalf of humanity without international consultation. It carries no legal force whatsoever. Nobody has ever had to test it.
Three Minutes Aimed at Hercules
Listening is only half the subject. On 16 November 1974, at the ceremony marking Arecibo’s resurfaced 305-metre dish, Frank Drake and colleagues including Carl Sagan pushed a transmission out toward the globular cluster M13. It ran for under three minutes and carried 1,679 bits, a number chosen because it factors only as 23 by 73 – arrange the bits in a grid with those dimensions and a picture appears. The picture holds the numbers one to ten, the atomic numbers of the elements in DNA, a schematic of the double helix, a stick figure of a human, the population of Earth at the time, the Solar System, and the telescope doing the sending.
M13 is about 25,000 light-years away and will not be in that spot when the pulse arrives. Drake never pretended otherwise. Our own message to aliens was a demonstration of capability aimed at the people standing on the ground, and it worked as one. The dish that sent it collapsed in December 2020.
The Records That Are Still Moving
Pioneer 10 and Pioneer 11, launched in 1972 and 1973, each carry a gold-anodised aluminium plaque designed by Drake and Sagan and drawn by Linda Salzman Sagan: a man, a woman, the hyperfine transition of hydrogen as a unit of length, and a map of fourteen pulsars whose periods fix both our position and the launch date.
The Voyagers, launched in 1977, went further. Each carries a gold-plated copper phonograph record: 115 images, greetings in 55 languages, whale song, thunder, a kiss, and about ninety minutes of music running from Bach through Javanese gamelan to Chuck Berry and Blind Willie Johnson. Sagan chaired the committee that chose it all in under a year. Both craft are in interstellar space now, and neither will pass near another star for tens of thousands of years.
Nobody involved seriously expected anyone to play them. They are self-portraits. The audience was always us.
Should We Answer?
Deliberate transmission – METI, as opposed to passive SETI – is where the field stops being collegial. In 2017 and 2018 Douglas Vakoch’s METI International used the EISCAT antenna in Tromso to beam music and a tutorial toward Luyten’s Star, 12.4 light-years off, where a planet in the habitable zone is known. The signal arrives in 2030. A reply could not reach us before the early 2040s.
A 2015 statement signed by a long list of scientists and technologists argued that no such broadcast should go out until there has been a worldwide discussion, since we cannot estimate the risk of drawing attention. Stephen Hawking made the same point more bluntly. The counterargument runs that our radar and broadcast leakage has been spilling outward for decades anyway – though that is less reassuring than it sounds, because leakage is faint and smeared while a deliberate narrowband beam is louder by an enormous factor.
Nobody has the authority to decide. Anyone with a large enough transmitter can send whatever they like, and a few have.
The record stands at zero confirmed detections, one unrepeatable anomaly from 1977, and one candidate that taught the field how to police itself. A message from aliens, if it ever lands, will look unremarkable for months before it looks like history. If you want to watch the next candidate go through the checks – or argue about whether we should be answering at all – SETIworld is where that conversation lives.
