In 1967, astronomers thought they had finally heard from the neighbors. They intercepted a signal so regular and precise it seemed impossible for it to be natural.
But the excitement didn’t last. Turns out, the “message” wasn’t an artificial broadcast—it was a pulsar, a rapidly spinning neutron star acting like a cosmic metronome.
An alien figure. Image credits: James Bat Barrera/Pexels
Now, a team of scientists is revisiting that “false alarm” with a fresh perspective. Their new research suggests that a “hello” from the stars doesn’t need to sound like a human radio station. Instead, aliens might be sending carefully timed flashes of light, much like the rhythmic pulsing of fireflies.
The study doesn’t claim we’ve found ET yet. Instead, it challenges our very definition of intelligence and what it means to be “detectable” in a silent universe.
“Taking non-human communication into account is essential if we want to broaden our intuition and understanding about what alien communication could look like, and what a theory of life ought to explain,” Estelle Janin, one of the study’s authors and a doctoral candidate at Arizona State University, said.
Life can speak in many ways
The biggest hurdle in the Search for Extraterrestrial Intelligence (SETI) is our own bias. For decades, we’ve focused on radio signals because humans spent the 20th century leaking radio waves into space. We assumed everyone else would do the same.
But on Earth, that phase is already ending, and after mere decades, which is nothing on a cosmic scale. As we move toward fiber optics and focused satellite beams, our planet is becoming more “radio quiet.” If we only look for radio waves, we might only catch civilizations during a tiny, blink-and-you-miss-it window of their technological history.
To escape this trap, the researchers looked at how life communicates on Earth—outside of the human bubble. They landed on fireflies. These insects use brief, repeating flashes to find mates. These aren’t complex “messages” in a linguistic sense, but they are highly structured, energy-efficient, and evolve to stand out against a noisy background.
“We can start from what life on Earth demonstrably does—not restricted to humans—and ask which aspects might reflect more universal, generalizable regularities, based on evolution and selection,” Janin said.
The researchers treated this idea as a model rather than a literal claim. They explored whether an alien civilization evolves signals that are optimized to be noticeable, energy-efficient, and distinct from natural noise—without needing to “say” anything?
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Testing the firefly flashes model
To test this “cosmic firefly” theory, the team built computer models that mimic how biological flash patterns evolve over generations. They then dropped these artificial “alien” signals into a realistic data set of 158 real pulsars.
The goal was to see if a signal could be noticeable and energy-efficient without needing to “say” anything complex. The results were telling. The artificial signals were more energy-efficient than 99% of the natural pulsar background.
Against this pulsar background, the researchers inserted artificial alien signals designed using firefly-inspired rules. These signals were built from simple on–off flashes and were shaped by two competing pressures: standing out from the background (dissimilarity) and using as little energy as possible.
The results were striking. “The artificial signal cost was lower than 84.30 percent of the background and was lower than 99.78 percent of the pulsar background. This suggests that pulsars in the background population do not exhibit evidence of their signals being artificial in origin,” the study authors note.
In other words, a life-driven signal does not need to be powerful or complicated. Its structure alone can hint at evolution and selection, which are hallmarks of life. More importantly, the team found that signals do not need to be decipherable or meaningful in a human sense. They only need to show patterns that are unlikely to arise from known astrophysical processes.
A Stranger Universe
By grounding SETI in the broader biology of Earth, rather than in human communication habits, the search for aliens becomes less biased and more flexible.
This approach could influence how astronomers design future surveys, especially as telescopes become better at detecting faint optical signals and time-based patterns.
However, the work has clear limitations. The researchers did not find any real alien signals, and the idea remains a thought experiment. Pulsars were used as stand-ins for natural background noise, not as suspects themselves.
Plus, the models also simplify many aspects of biology, evolution, and technology. Real alien civilizations, if they exist, could behave in ways far stranger than even fireflies. Still, the research work serves as an important reminder that the universe may not be silent, but we may simply be listening in the wrong way.
The study is published in the journal arXiv.