100 mystery sounds under review for signs of extraterrestrial life

After examining nearly 30 years of signals, researchers at the University of California, Berkeley, have identified 100 mysterious radio signals from deep space that they want to examine for signs of extraterrestrial life. And they couldn’t have done it without 11 years of volunteer work from millions of PC owners around the world.

What is SETI@home?

Even with today’s advanced computers, the world’s most complex data problems cannot be solved by a single machine. Instead, it is much more efficient to distribute tasks between several separate computers. However, for decades, the technology to manage even these distributed responsibilities was relegated to well-funded businesses and government institutions. But with the rise of personal computers (PCs), UC Berkeley researchers like David Gedye and David Anderson realized that the untapped pool of citizen scientists could be a vital asset. And what greater pool of data could one draw from than the immensity of interstellar space?

In 1999, the computer scientists teamed up with astronomers Eric Korpela and Dan Werthimer to launch SETI@home. The project relied on individuals downloading a client program onto their personal PCs, designed to analyze data passively collected by a 984-foot-wide radio telescope at the now-closed Arecibo Observatory in Puerto Rico. Even though Arecibo’s line of sight only encompassed about a third of the entire sky, it still included most of the stars in the Milky Way.

“We [were]“This is without a doubt the most sensitive narrowband search over large parts of the sky, so we had the best chance of finding something,” Korpela said in a recent UC Berkeley profile.

Before launching SETI@home, the project organizers estimated that they would receive around 50,000 volunteers. In just a few days, they exceeded 200,000 participants from more than 100 countries. By the program’s first anniversary, the SETI@home client had been downloaded to more than 2 million PCs.

In search of ET

The data itself was not collected by simply aiming Arecibo at a section of space and listening to the ET’s whispers. The Earth is constantly moving around the Sun, and the same is likely true for any source of extraterrestrial life. This required Korpela and his colleagues to design a protocol to mathematically reconfigure the frequency clips to account for Doppler drifts.

“We had to look at a whole range of possible drift rates – tens of thousands – just to make sure we had all the possibilities. That increases the computing power we need by 10,000 times,” Anderson said. “The fact that we had a million personal computers allowed us to do this. No other SETI radio project has been able to do this.”

By the time SETI@home officially ended in 2020, the team was looking at around 12 p.m. billion signals of interest. To browse these files, it was ultimately necessary to call on a supercomputer, in this case a facility at the Max Planck Institute for Gravitational Physics in Germany. From there, researchers could filter their suspects down to a few million signals, then rank them according to the likelihood of extraterrestrial origin after accounting for radio interference from sources such as orbiting satellites, television broadcasts and even kitchen microwaves.

Korpela and Werthimer ultimately chose about 100 final candidates worthy of additional examinations. Since July 2025, they have been using China’s Five Hundred Meter Aperture Spherical Telescope (FAST) to collect new data on these sections of the sky. The approach was detailed in two studies published last year in The astronomical journaland presents both the strengths of the project and where future efforts can improve their work.

“Some of our conclusions are that the project didn’t completely work the way we thought it would. And we have a long list of things that we would have done differently and that future sky survey projects should do differently,” Anderson explained. “[But] if we don’t find ET, what we can say is that we have established a new level of sensitivity. If there was a signal above a certain strength, we would have found it.

The power of crowdsourcing

However, Anderson and the others aren’t holding their breath. According to Korpela, Arecibo’s limited field of view and the absence of particularly striking radio signals so far mean that a sudden ET reveal is not yet likely.

“We’re a little disappointed that we didn’t see anything,” he said. “To survey greater distances, you need larger telescopes and longer observing times. It’s always better to be able to control the telescope for your project. We couldn’t control what the telescope was doing.”

Regardless, SETI@home is a testament to the power of both crowdsourcing and citizen science. Combined with all the advances in the PC since 1999, there is a chance that an heir to the project could finally find this extraordinary space signal that will alter history.

“I think the search for extraterrestrial intelligence continues to capture people’s imaginations,” Korpella said. “I think you could still get significantly more processing power than what was used for SETI@home and process more data with wider internet bandwidth.”

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