*Written by OC Wanderer, author of Destiny Among the Stars, a LitRPG sci-fi series set in the real stellar neighborhood. Published October 28, 2026.* We have been listening for other civilizations by radio for 66 years, and the search went on [after Arecibo fell](https://ocwanderer.com/blog/why-did-we-stop-using-arecibo-telescope-and-what-did-we-lose). We left Arecibo broken, with no replacement under construction for the dish or its transmitter, and its listening moved to other telescopes. So what has all that listening heard? SETI, the search for extraterrestrial intelligence, is why I wanted to write *Destiny Among the Stars*. What would happen if there was life out there, and we could reach it, and we could communicate with it? Webb’s images made that question vivid for me. Its First Deep Field covers a patch of sky about the size of a grain of sand held at arm’s length and contains thousands of galaxies.<sup class="footnote-ref" data-footnote="true" id="fnref-1"><a class="footnote-link" href="#fn-1">1</a></sup> How could I look at that and not wonder whether any of them holds another civilization? Then come the questions that could turn that possibility into an adventure. [Could we even get out there?](https://ocwanderer.com/blog/why-cant-we-actually-build-the-alcubierre-drive) If we could, [could we find planets?](https://ocwanderer.com/blog/is-the-habitable-zone-actually-a-useful-concept-or-is-it-oversimplified) And if we found them, what if there was life on them, intelligent life? SETI is how that last question is being tested right now. SETI has yet to confirm a signal from another civilization. That leaves the question behind my book wonderfully open.<sup class="footnote-ref" data-footnote="true" id="fnref-2"><a class="footnote-link" href="#fn-2">2</a></sup> Some candidates looked extraordinary until astronomers tried to hear them again or traced them to Earth. Surveys can rule out particular broadcasts, but the searches counted in a 2018 estimate covered a tiny fraction of the possibilities. I want to know what that silence can really tell us. ## What happened to the Wow! signal and the other famous candidates? The searches look for a radio tone squeezed into a very narrow slice of frequency, because no known natural source in space makes one that narrow.<sup class="footnote-ref" data-footnote="true" id="fnref-3"><a class="footnote-link" href="#fn-3">3</a></sup> The trouble is that human transmitters make narrow tones all the time. How do you tell a distant civilization from the electronics around your own telescope? I group the checks into three questions. Does the tone belong to one spot in the sky, vanishing when the telescope turns away and returning when it turns back? Can we hear it again on another day, and at a second telescope if one is available? Can anything on or near Earth, from a satellite to a radar to observatory electronics, account for it? Those questions are what give an exciting sound a chance to become evidence.<sup class="footnote-ref" data-footnote="true" id="fnref-4"><a class="footnote-link" href="#fn-4">4</a></sup> Earthly interference joined the search almost as soon as it began. In 1960 Frank Drake used a radio dish in Green Bank, West Virginia, to listen to two Sun-like stars within twelve light-years of us, [Tau Ceti](https://ocwanderer.com/blog/is-tau-ceti-the-best-candidate-for-a-habitable-planet-in-the-solar-neighborhood) and Epsilon Eridani, from April to July. He called it Project Ozma. An early signal was a false alarm, probably aircraft radar: a reminder of why that Earth-source check matters. The search found no signs of extraterrestrial intelligence.<sup class="footnote-ref" data-footnote="true" id="fnref-5"><a class="footnote-link" href="#fn-5">5</a></sup> For 72 seconds, the Wow! signal gave astronomers something much harder to explain. On August 15, 1977, Ohio State University’s Big Ear telescope recorded a strong, narrow radio tone. Big Ear could not steer. It pointed at one strip of sky while Earth’s rotation carried its view along, so a fixed point among the stars took 72 seconds to cross its beam. The tone rose and fell over exactly that long, just as a source passing through the beam should. That is the part that makes this signal so compelling to me. The astronomer who found it on the printout a few days later wrote “Wow!” beside it.<sup class="footnote-ref" data-footnote="true" id="fnref-6"><a class="footnote-link" href="#fn-6">6</a></sup> Big Ear had two beams that swept the same patch of sky a few minutes apart, and only one of them caught the tone, so whatever made it was there for one pass and missing for the other. Big Ear kept scanning that strip for weeks and scanned it many more times a few years later, and other observatories have searched the same spot since. In 49 years the Wow! signal has never been detected again.<sup class="footnote-ref" data-footnote="true" id="fnref-7"><a class="footnote-link" href="#fn-7">7</a></sup> A genuine one-off transmission could leave us with the same frustrating puzzle: a promising sound and nothing to listen for again. I wonder how many interesting things a telescope might catch once, while the explanation stays out of reach. BLC1 offered another tantalizing possibility, this time in our own stellar neighborhood. In 2019 the Parkes telescope in Australia observed Proxima Centauri, the nearest star to the Sun and the star that [Proxima b](https://ocwanderer.com/blog/could-proxima-b-actually-be-habitable-or-is-that-just-wishful-thinking) orbits. Over six days the search software logged about 4.2 million narrow radio tones. One survived every filter and an inspection by eye: a tone that lasted for hours and was missing each time the telescope looked away. The team named it BLC1.<sup class="footnote-ref" data-footnote="true" id="fnref-8"><a class="footnote-link" href="#fn-8">8</a></sup> The clue that unraveled BLC1 was hiding elsewhere in the recordings. The team searched for similar tones and found dozens of lookalikes at other frequencies, and the lookalikes also appeared while the dish pointed away from the star, so they came from somewhere near the telescope. The lookalikes sat at regular frequency spacings that match the timing circuits, called clock oscillators, in ordinary electronics, and BLC1 fit the same pattern. The tone had looked as though it belonged to Proxima, yet its relatives pointed back to our own electronics. Parkes also found nothing at BLC1’s frequency when it returned in November 2020 and again in April and May 2021, leaving the repeat-observation question unanswered as well.<sup class="footnote-ref" data-footnote="true" id="fnref-9"><a class="footnote-link" href="#fn-9">9</a></sup> <!-- destiny-inline-image -->  ## What does a search that hears nothing rule out? Suppose someone out there has a powerful radar and points it straight at us. Would we hear it? A quiet search can answer a question that specific, because astronomers can work out what their telescope would have caught. A Breakthrough Listen survey published in 2017 gives us a useful example. It used the Green Bank Telescope, at the same West Virginia site where Ozma ran, to observe 692 nearby stars, all within about 160 light-years. Each star got three five-minute looks, fifteen minutes in all, with the telescope swinging to a different target in between so that anything that stayed present while it pointed away could be thrown out as interference.<sup class="footnote-ref" data-footnote="true" id="fnref-10"><a class="footnote-link" href="#fn-10">10</a></sup> Eleven detections made it through the software’s thresholds, each worth a closer look. All eleven matched known kinds of human radio interference when the astronomers examined them.<sup class="footnote-ref" data-footnote="true" id="fnref-11"><a class="footnote-link" href="#fn-11">11</a></sup> Fifteen minutes per star was enough to catch a strong transmitter. The survey’s authors worked out that it was sensitive enough to detect a transmitter like [Arecibo’s planetary radar](https://ocwanderer.com/blog/why-did-we-stop-using-arecibo-telescope-and-what-did-we-lose) from any of the 692 stars, if that transmitter were aimed at Earth and left running. The observations found no such broadcast during those brief visits, within the frequencies the survey covered. From that result the authors estimated that fewer than one star system in a thousand within that distance was broadcasting that way at the time.<sup class="footnote-ref" data-footnote="true" id="fnref-12"><a class="footnote-link" href="#fn-12">12</a></sup> Now imagine listening to the right star at the wrong moment. A transmitter switched off during that fifteen-minute visit would escape us, as would a beam pointed somewhere else. A quieter signal or one outside the survey’s frequency band would slip past too. The possibility that drew me to *Destiny Among the Stars*—life we could reach and communicate with—includes far more than civilizations sending that particular kind of beam toward Earth. ## How much have we searched so far? Pointing at the right star is only the beginning. We also need the right frequency, the right moment and enough sensitivity to hear across the distance. How do you measure progress when a signal could hide in all those ways? In 2018 three astronomers built a model of the search space: the whole sky, out to about 33,000 light-years, which is roughly the distance to the center of the Galaxy, across a wide span of radio frequencies. They used that model to add up the coverage of the large SETI programs through that year.<sup class="footnote-ref" data-footnote="true" id="fnref-13"><a class="footnote-link" href="#fn-13">13</a></sup> The total came to about six parts in a billion billion. If the search space were all the water in Earth’s oceans, the authors wrote, the searching done by 2018 would amount to about 8,000 liters, somewhere between a large hot tub and a small swimming pool. Imagine scooping that much seawater out of the oceans to look for fish. If the scoop comes up empty, how confident would you feel declaring the oceans empty too? That is why the comparison fascinates me: decades of patient listening can still leave an enormous amount of room for discovery.<sup class="footnote-ref" data-footnote="true" id="fnref-14"><a class="footnote-link" href="#fn-14">14</a></sup> The 692-star survey is one of the searches in that total. Its fifteen minutes per star in one band of frequencies amount to up to about 500 liters of the 8,000. The ocean image belongs to the 2018 estimate; searching has continued since, so it cannot serve as a measurement of today’s coverage.<sup class="footnote-ref" data-footnote="true" id="fnref-15"><a class="footnote-link" href="#fn-15">15</a></sup> ## So has SETI found anything, or is it just a long silence? Sixty-six years of listening have yet to give us a confirmed signal from another civilization. I find the scale of the remaining question thrilling: in the 2018 model, the searches amounted to somewhere between a large hot tub and a small swimming pool compared with Earth’s oceans. The 2018 tally showed how much remained to explore. Searching has grown since, and I would love to know how much of that ocean we have covered now. The question behind my book—could we reach intelligent life and talk to it?—is still a wonderful one to ask. What could that silence mean, and would anyone out there hear us? [The Fermi Paradox: Do We Want to Notice Another Civilization or Be Noticed?](https://ocwanderer.com/blog/the-fermi-paradox-has-dozens-of-solutions-which-ones-do-scientists-actually-take-seriously) > [!lore] If you want to follow a crew that goes out to look in person, [start *Destiny Among the Stars*](https://ocwanderer.com/storytime/story/destiny-among-the-stars). ## Endnotes 1. <span id="fn-1"></span> NASA, [“NASA’s Webb Delivers Deepest Infrared Image of Universe Yet,”](https://science.nasa.gov/missions/webb/nasas-webb-delivers-deepest-infrared-image-of-universe-yet/) July 12, 2022: the image covers a patch of sky “approximately the size of a grain of sand held at arm’s length” and shows the galaxy cluster SMACS 0723 “teeming with thousands of galaxies.” <a class="footnote-backref" href="#fnref-1" aria-label="Back to reference 1">↩</a> 2. <span id="fn-2"></span> SETI Institute, [“FAQ”](https://www.seti.org/about/faq): “No SETI search has yet received a confirmed, extraterrestrial signal.” Author calculation: Project Ozma began in April 1960 (note 5), and 2026 − 1960 = 66 years. <a class="footnote-backref" href="#fnref-2" aria-label="Back to reference 2">↩</a> 3. <span id="fn-3"></span> J. Emilio Enriquez et al., [“The Breakthrough Listen Search for Intelligent Life: 1.1–1.9 GHz Observations of 692 Nearby Stars,”](https://arxiv.org/abs/1709.03491) *Astrophysical Journal* 849 (2017): 104. The paper says a signal a few hertz wide is of interest because it is too narrow to arise naturally from known astrophysical sources. <a class="footnote-backref" href="#fnref-3" aria-label="Back to reference 3">↩</a> 4. <span id="fn-4"></span> Sofia Z. Sheikh et al., [“Analysis of the Breakthrough Listen Signal of Interest blc1 with a Technosignature Verification Framework,”](https://arxiv.org/abs/2111.06350) *Nature Astronomy* 5 (2021): 1153–1162. The paper sets out ten checks for a future signal of interest. The three tests in the text are my grouping of them: absence in off-source observations; re-observation of the target with the same and other instruments, plus a search of archival data; and comparison with catalogued interference, with the drift rates of human technology, and with similar signals at other frequencies. <a class="footnote-backref" href="#fnref-4" aria-label="Back to reference 4">↩</a> 5. <span id="fn-5"></span> SETI Institute, [“Project Ozma”](https://www.seti.org/research/seti-101/project-ozma/): April to July 1960, six hours a day, an 85-foot antenna tuned to the 1420 MHz line of hydrogen, Tau Ceti and Epsilon Eridani, and “an early false alarm probably caused by aircraft radar.” National Radio Astronomy Observatory, [“Project Ozma”](https://public.nrao.edu/gallery/project-ozma/): the 85-foot Howard E. Tatel telescope at Green Bank; no signs of extraterrestrial intelligence detected. The SETI Institute gives each star’s distance as approximately eleven light-years; [my Tau Ceti post](https://ocwanderer.com/blog/is-tau-ceti-the-best-candidate-for-a-habitable-planet-in-the-solar-neighborhood) uses NASA’s 11.9 light-years for that star, so the text says “within twelve.” <a class="footnote-backref" href="#fnref-5" aria-label="Back to reference 5">↩</a> 6. <span id="fn-6"></span> Jerry R. Ehman, [“The Big Ear Wow! Signal: Thirty Years Later,”](https://www.bigear.org/Wow30th/wow30th.htm) Ohio State University Radio Observatory, 2007. Ehman is the astronomer who marked the printout. The printout holds six readings of about 12 seconds each, 72 seconds in all, and they follow the telescope’s beam pattern to better than 99 percent. At its peak the signal was 30.5 ± 0.5 times stronger than the background noise, at 1420.4556 ± 0.005 MHz, in a band around 1420 MHz where transmitting is prohibited worldwide. A 2025 reanalysis of archival Ohio State records revises the frequency to 1420.726 ± 0.005 MHz and raises the peak strength: Abel Méndez et al., [“Arecibo Wow! II,”](https://arxiv.org/abs/2508.10657) arXiv preprint. <a class="footnote-backref" href="#fnref-6" aria-label="Back to reference 6">↩</a> 7. <span id="fn-7"></span> Ehman, [“Thirty Years Later”](https://www.bigear.org/Wow30th/wow30th.htm): the two beams should have shown the source twice within about five minutes, and the printout shows one detection; Big Ear stayed on the same strip of sky for about 60 more days and scanned it many times again a few years later without seeing the signal. Abel Méndez, Kevin Ortiz Ceballos, and Jorge I. Zuluaga, [“Arecibo Wow! I: An Astrophysical Explanation for the Wow! Signal,”](https://arxiv.org/abs/2408.08513) arXiv preprint, 2024: the source “has never been detected again despite numerous follow-up attempts.” That paper proposes a natural cause, a flare from a compact star briefly brightening a cold hydrogen cloud, and the proposal is unconfirmed. Author calculation: 2026 − 1977 = 49 years. <a class="footnote-backref" href="#fnref-7" aria-label="Back to reference 7">↩</a> 8. <span id="fn-8"></span> Shane Smith et al., [“A Radio Technosignature Search Towards Proxima Centauri Resulting in a Signal-of-Interest,”](https://arxiv.org/abs/2111.08007) *Nature Astronomy* 5 (2021): 1148–1152. Parkes (Murriyang) observed Proxima Centauri for 26 hours and 9 minutes between April 29 and May 4, 2019; the search found 4,172,702 hits and 5,160 events present in on-source pointings and absent from off-source ones; one event passed all rounds of filtering and visual inspection. BLC1 was detected at 982.002571 MHz. Sheikh et al. (note 4) give its duration as 5.03 hours on April 29, 2019. Author calculation: 4,172,702 ÷ 5,160 ≈ 809, so about one hit in 800 reached the second stage. <a class="footnote-backref" href="#fnref-8" aria-label="Back to reference 8">↩</a> 9. <span id="fn-9"></span> Sheikh et al. (note 4). The abstract reports “dozens” of instances of interference with similar morphologies and concludes that BLC1 is an electronically drifting intermodulation product of local, time-varying interferers, meaning two local electronic signals mixing to make a third. The device was never identified. Re-observations in November 2020 and from April 29 to May 3, 2021 detected nothing near BLC1’s frequency. Breakthrough Initiatives, [“Breakthrough Listen Releases Analysis of Previously Detected Signal,”](https://breakthroughinitiatives.org/news/33) October 25, 2021: “around 60 signals” shared many of the candidate’s characteristics and were also seen in their off-source observations, at frequency intervals that correspond to multiples of common oscillator frequencies. <a class="footnote-backref" href="#fnref-9" aria-label="Back to reference 9">↩</a> 10. <span id="fn-10"></span> Enriquez et al. (note 3): the Robert C. Byrd Green Bank Telescope; 692 primary targets observed from 1.1 to 1.9 GHz in three sets of five-minute observations interspersed with five-minute observations of secondary targets; all stars within 50 parsecs. Author calculation: 50 parsecs × 3.26 = 163 light-years; 3 × 5 minutes = 15 minutes per star. <a class="footnote-backref" href="#fnref-10" aria-label="Back to reference 10">↩</a> 11. <span id="fn-11"></span> Enriquez et al. (note 3): the search produced nearly 29 million hits; eleven events passed the thresholds, and detailed analysis found them consistent with known examples of human-made radio frequency interference. <a class="footnote-backref" href="#fnref-11" aria-label="Back to reference 11">↩</a> 12. <span id="fn-12"></span> Enriquez et al. (note 3): a planetary radar similar to Arecibo’s, transmitting continuously at Earth, would have been detectable from any star in the sample. The paper puts the Arecibo radar’s equivalent isotropic radiated power at 10¹³ watts and concludes that, at the time of the observations, none of the systems hosted high-duty-cycle transmitters of that power between 1.1 and 1.9 GHz, and that fewer than about 0.1 percent of stellar systems within 50 parsecs have one. Author calculation: 0.1 percent is 1 in 1,000. <a class="footnote-backref" href="#fnref-12" aria-label="Back to reference 12">↩</a> 13. <span id="fn-13"></span> Jason T. Wright, Shubham Kanodia, and Emily G. Lubar, [“How Much SETI Has Been Done? Finding Needles in the n-Dimensional Cosmic Haystack,”](https://arxiv.org/abs/1809.07252) *Astronomical Journal* 156 (2018): 260. Their model has eight dimensions: sensitivity, central frequency, three of distance and position, transmission bandwidth, time, and polarization. Its boundaries are the whole sky out to 10 kiloparsecs and frequencies from 10 MHz to 115 GHz. Author calculation: 10 kiloparsecs × 3,262 = about 32,600 light-years. <a class="footnote-backref" href="#fnref-13" aria-label="Back to reference 13">↩</a> 14. <span id="fn-14"></span> Wright, Kanodia, and Lubar (note 13), arXiv version: the searches sum to 6.0 × 10⁻¹⁸ of the model space; Earth’s oceans hold about 1.335 × 10²¹ liters, so the searching is equivalent to about 8,000 liters. Author check: 6.0 × 10⁻¹⁸ × 1.335 × 10²¹ = 8,010 liters, and 10⁻¹⁸ is one part in a billion billion. The fish image comes from Jill Tarter and colleagues’ 2010 estimate of one drinking glass of seawater, which the paper quotes and revises upward. The figure dates from 2018, and searching has continued: Breakthrough Listen’s system on the MeerKAT array in South Africa has processed beams on more than 1.2 million pointings since 2022, according to Daniel J. Czech et al., [“Breakthrough Listen’s Automated Commensal Technosignature Survey with MeerKAT,”](https://arxiv.org/abs/2607.23651) arXiv preprint, 2026. <a class="footnote-backref" href="#fnref-14" aria-label="Back to reference 14">↩</a> 15. <span id="fn-15"></span> Wright, Kanodia, and Lubar (note 13): the 692-star survey covers up to 3.8 × 10⁻¹⁹ of the model space. Author calculation: 3.8 × 10⁻¹⁹ × 1.335 × 10²¹ = 507 liters; 3.8 × 10⁻¹⁹ ÷ 6.0 × 10⁻¹⁸ = 0.063, about one sixteenth. <a class="footnote-backref" href="#fnref-15" aria-label="Back to reference 15">↩</a>