SETI Project Narrows Search To Final 100 Signals

For more than two decades, the SETI@home project has been quietly humming away in the background of millions of personal computers, all in pursuit of one of humanity’s most tantalizing questions: Are we alone in the universe? Now, after sifting through mountains of data and narrowing the field, researchers at the University of California, Berkeley, have reached the final stages of this monumental search. The project has zeroed in on just 100 unexplained radio signals—each a possible whisper from the cosmos, each a puzzle piece in the sprawling search for extraterrestrial intelligence.

According to two landmark papers published in 2025 in The Astronomical Journal, this culmination is the result of years of relentless data gathering, algorithmic refinement, and global collaboration. The first paper focuses on the nuts and bolts: how SETI@home collected and processed its vast dataset, while the second dives into the analysis and findings, laying out how researchers painstakingly whittled down billions of candidate detections to a mere hundred signals worthy of further scrutiny.

“Until about 2016, we didn’t really know what we were going to do with these detections that we’d accumulated,” said David Anderson, computer scientist at UC Berkeley and co-founder of SETI@home, as quoted by The Astronomical Journal. “We hadn’t figured out how to do the whole second part of the analysis.” That crucial second part—the deep dive into the torrent of radio data beamed in from the Arecibo Observatory—has finally been completed, thanks to a combination of new algorithms and the tireless efforts of both scientists and citizen volunteers.

The story of SETI@home is as much about people as it is about technology. Launched in 1999, the project transformed ordinary home computers into a distributed scientific instrument, harnessing their idle processing power to comb through data for signs of intelligent life. Over its lifespan, SETI@home processed nearly 12 billion candidate signals, each a fleeting blip of energy at a particular frequency, each demanding attention. For years, the signals piled up faster than they could be analyzed, a mountain of cosmic haystacks in which to search for the proverbial needle.

Eric Korpela, a Berkeley astronomer and longtime SETI@home collaborator, put it succinctly: “There’s no way that you can do a full investigation of every possible signal that you detect, because doing that still requires a person and eyeballs.” It’s a sentiment echoed by many in the field, highlighting both the promise and the limitations of even the most advanced distributed computing projects.

To tackle the deluge, the SETI@home team developed sophisticated filtering systems to weed out signals from satellites, radar, and other Earth-based interference. These new algorithms, detailed in the 2025 papers, allowed the researchers to systematically flag and reject signals that could be confidently attributed to human sources. What remained—those 100 enigmatic signals—are now the focus of intense scrutiny.

But the search didn’t stop at Berkeley. Since July 2025, the final 100 signals have been re-examined using China’s Five-hundred-meter Aperture Spherical Telescope, better known as FAST. After the Arecibo Observatory’s collapse in 2020, FAST stands as the world’s only facility capable of following up on these kinds of observations. According to SETI scientists, this next phase is critical: each signal is being analyzed with even greater sensitivity, and while most are likely the result of human-made interference, the possibility of an alien origin—however remote—remains too important to ignore.

“If we don’t find ET, what we can say is that we have established a new sensitivity level. If there were a signal above a certain power, we would have found it,” Anderson emphasized in The Astronomical Journal. The project now represents the most sensitive narrowband search across large portions of the sky ever attempted, setting a new benchmark for future efforts to detect extraterrestrial technologies. Transparency and reproducibility are front and center: both papers make available open datasets and refined code, inviting other researchers to continue the search independently.

Yet, for all its technical triumphs, the SETI@home saga is tinged with a sense of bittersweet accomplishment. “We are, without doubt, the most sensitive narrowband search of large portions of the sky, so we had the best chance of finding something,” Korpela reflected. “So yeah, there’s a little disappointment that we didn’t see anything.” Anderson, too, acknowledges that the project’s early limitations—especially in data handling, shaped by the computing power available in 1999—may have led to missed opportunities. “We have to do a better job of measuring what we’re excluding,” he said. “Are we throwing out the baby with the bath water? I don’t think we know for most SETI searches… In a world where I had the money, I would reanalyze it the right way. And we did make some mistakes. These were conscious choices because of how fast computers were in 1999.”

That lingering uncertainty—the sense that something extraordinary could still be hiding in the data—fuels both scientific rigor and imagination. As Anderson put it, “There’s still the potential that ET is in that data and we missed it just by a hair.” This humility and openness to discovery are hallmarks of the SETI community, which continues to push the boundaries of what’s possible in radio astronomy and signal analysis.

The SETI@home experience also underscores the power of global collaboration and citizen science. Millions of volunteers around the world donated their computer time and their curiosity, helping to advance the search for life beyond Earth. The project’s legacy is a testament to what can be achieved when people come together in pursuit of a shared cosmic question.

But what if, someday, we do detect a genuine extraterrestrial signal? How would we even begin to communicate? Here, recent research offers a fascinating twist. Scientists from Monash University and RMIT University in Australia have discovered that honeybees—creatures evolutionarily distant from humans—can perform simple math, order items by quantity, and distinguish odd from even numbers. Their findings, published after a decade of experiments, suggest that math might not just be a human construct but a universal language of intelligence.

“The ability to add and subtract by 1 shows that the six-legged creatures can represent all natural numbers,” the study reports. If bees can grasp mathematical concepts, perhaps extraterrestrial intelligence—no matter how alien—might share this cognitive trait. This insight could profoundly shape how scientists attempt to craft messages for potential alien civilizations, favoring math as a bridge across the vast gulf of evolutionary difference.

In a universe of some 200 sextillion stars, the odds are good that we are not alone. The SETI@home project, with its final 100 signals and its legacy of innovation, transparency, and hope, stands as a monument to our species’ curiosity and persistence. As new technologies and telescopes come online, and as machine learning opens up fresh avenues for data review, the search for cosmic company will continue—one signal, one question, one possibility at a time.

Whatever the outcome, the story of SETI@home reminds us that the quest to understand our place in the universe is far from over. The next chapter could be just a click—or a cosmic signal—away.