Dan Werthimer has spent more than four decades trying to eavesdrop on aliens.
A pioneering researcher in the field of astronomy known as SETI, or the search for extraterrestrial intelligence, Werthimer's work involves scanning the cosmos with huge, ground-based radio telescopes to look for strange or unexplained signals that may have originated from alien civilizations.
If it sounds a bit like looking for a needle in a haystack, that's because it sort of is.
In recent years, however, the search for extraterrestrial intelligence has become even more complicated. Increasing demands for mobile services and wireless internet have crowded the radio spectrum, creating interference that can skew data and add "noise" to scientific results.
"Earth is just getting more and more polluted," said Werthimer, chief technologist at the Berkeley SETI Research Center. "With some radio bands, it's already impossible to do SETI because they're so full of television transmitters, WiFI and cellphone bands."
As wireless technologies continue to grow, the problem will only get worse, Werthimer said, potentially jeopardizing one of the key ways that scientists have to search for intelligent life in the universe.
Werthimer was recently one of the authors of a pre-print study led by Chinese researchers that identified a radio signal that several news outlets mistakenly reported as having characteristics of an alien civilization. The signal was actually found to have been radio interference, Werthimer clarified.
Focused SETI research began in earnest in the 1980s, and was cemented in popular culture with the 1985 novel "Contact" by Carl Sagan, which was later adapted into a film in 1997 starring Jodie Foster.
At its heart, SETI research aims to answer the question: Are we alone in the universe? In the decades since scientists first started listening for alien signals, improvements in telescope technology and data processing have bolstered the search, Werthimer said.
"We used to listen to one channel, and now we're listening to 10 billion channels," he said. "The technology and science keeps improving."
Those leaps in technology, however, have come with their share of challenges. More satellites are being launched into low-Earth orbit than ever before as a result of falling launch costs and cheaper materials to build spacecraft. Society's growing reliance on wireless internet and GPS navigation also means more competition for radio frequencies.
"It's valuable spectrum and people want more and more of it for everyday activities," said Paul Horowitz, an emeritus professor of physics and electrical engineering at Harvard University and a prominent SETI researcher. "All that means is the radio spectrum is a mess these days."
For SETI scientists, having relatively clear and unobstructed channels to scan the cosmos is invaluable. Errant human interference not only creates more work for researchers to filter out, but can present itself as a falsely intriguing signal.
It's a conundrum that astronomers are all too familiar with, said Andrew Siemion, director of the Berkeley SETI Research Center and the Bernard M. Oliver Chair for SETI Research at the SETI Institute in Mountain View, California.
To avoid red herrings, scientists often rely on repeatability, which can involve studying the same target for extended periods to compare observations. Other times, researchers use what is known about human-caused interference to winnow down their results.
"At the same time that all these satellites are being launched, our knowledge about what's in space is also increasing," said Siemion, who is also a principal investigator for Breakthrough Listen, a 10-year, $100 million initiative to search for intelligent extraterrestrial life that was launched in 2015 by Stephen Hawking and Russian billionaire Yuri Milner.
He added that increased situational awareness in space makes it easier to identify satellites and other forms of human interference.
"It helps us know that we're not fooling ourselves by looking at a signal from a satellite and thinking that it's from a distant celestial source," Siemion said.
Advancements in machine learning are also making it faster and easier for scientists to filter interference out of their data, said Bruce Betts, chief scientist at The Planetary Society, which has been involved with SETI research since the organization was founded in 1980.
Betts said these improvements in processing should ensure that SETI research can continue in the years ahead.
"Even if you have more sources of interference, they're still going to follow certain frequency patterns and certain timing patterns," he said. "Adding hundreds of more satellites that all produce the same interference is really annoying, but you can develop systems to remove that."
As the field of SETI research has evolved, so too have other ideas for how to avoid interference in the future. Werthimer, Horowitz and others, for instance, are investigating ways to search for alien civilizations in the optical part of the spectrum.
Others have suggested installing a radio telescope on the far side of the moon, where it would be shielded from interference from Earth. While technically feasible, such a project would carry significant costs, Horowitz said.
"SETI has struggled with almost zero government support for the last few decades, so nobody is going to want to do that in a fiscally constrained time period," he added.
Yet in spite of technical and funding challenges, interest in SETI research has grown over time, according to Betts. Much of that can be attributed to the tantalizing possibility of finding intelligent life elsewhere in the universe, he said.
"More than most other discoveries, it would reframe a lot of our philosophical views of the universe," he said. "Yeah, it's a needle in the haystack, but if you find that needle, you’ve got one of the most profound discoveries in history."