SETI, or the Search for Extraterrestrial Intelligence, aims to find signs of life beyond Earth, focusing on the technology that advanced alien civilizations might create. When no signals, or technosignatures, are found in a survey, scientists can use that information to understand how far they could have detected such signals. Many of these technosignatures require greater power than our current technology can produce. Recently, SETI researchers examined how far various Earth technosignatures — like radio signals, atmospheric signatures, and optical signals — can be detected using today’s instruments. This study is one of the first to compare these different techniques side by side.
Sheikh et al. explored how distant Earth’s technosignatures could be detected with today’s instruments in a study called ‘Earth detecting Earth.’ Image credit: Breakthrough Listen Initiative.
Scientists in SETI look for proof of advanced civilizations by identifying signals or patterns that can’t be explained naturally. These signals, known as technosignatures, can take many forms.
Radio telescopes are the main tool used in these searches.
Optical telescopes are also employed to detect laser pulses that may indicate communication or movement.
Another method includes studying exoplanet atmospheres to find chemical signs that hint at life or technology.
While advanced concepts like Dyson spheres are fascinating, they weren’t included in this recent study.
Dr. Macy Huston, an astronomer at UC Berkeley, said, “Our aim was to ground SETI by focusing on what we can detect today from Earth.”
She added, “We shouldn’t assume other civilizations will be just like ours. Understanding our technology helps shape SETI searches.”
The team discovered that the most detectable technosignature from Earth is radio signals, like those from the old Arecibo Observatory, visible from up to 12,000 light-years away.
Atmospheric technosignatures, such as nitrogen dioxide emissions, have become easier to detect due to advancements in telescopes like the James Webb Space Telescope.
“With new tech like the Habitable Worlds Observatory, we could see atmospheres from as far as 5.7 light-years, near Proxima Centauri,” said the researchers.
The closer one gets to Earth, the more human-made signals are detectable, including city lights, lasers, and satellites, providing a clear picture of our technological impact.
Dr. Sofia Sheikh from the SETI Institute highlighted, “This research lets us view Earth through a cosmic lens: how does our planet appear to the rest of the galaxy?”
She noted that while we can’t know the exact answer, we can speculate on how other planets might be perceived based on pollution levels.
Future advancements in telescopes could improve detection of new technosignatures, including different pollution markers.
“Repeating studies like this as technology evolves can give us deeper insights into the search for extraterrestrial life,” the researchers concluded.
The findings are published in the Astronomical Journal.
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Sofia Z. Sheikh et al. 2025. Earth Detecting Earth: At What Distance Could Earth’s Constellation of Technosignatures Be Detected with Present-day Technology? AJ 169, 118; doi: 10.3847/1538-3881/ada3c7
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Earth,Exoplanet,Extraterrestrial civilization,Extraterrestrial intelligence,Extraterrestrial life,Milky Way,Radio signal,SETI,Technosignature
