Scientists measure Earth's cosmic detectability

Scientists measure Earth's cosmic detectability
by Clarence Oxford
Los Angeles CA (SPX) Feb 04, 2025

A team of researchers led by Dr. Sofia Sheikh from the SETI Institute, in collaboration with the Characterizing Atmospheric Technosignatures project and the Penn State Extraterrestrial Intelligence Center, investigated whether an extraterrestrial society with technology akin to ours might detect Earth and the evidence of humanity. They sought to identify which signals would be visible and how far those signals could travel.

Using theoretical modeling, this study is the first to assess a range of technosignatures as one unified collection. Findings indicate that among Earth's signals, radio transmissions stand out, specifically the planetary radar beams once transmitted by the Arecibo Observatory, which could be discerned from up to 12,000 light-years away.

Atmospheric technosignatures, such as nitrogen dioxide, have recently become more discernible thanks to advancements in tools like the James Webb Space Telescope and the upcoming Habitable Worlds Observatory (HWO). With HWO, scientists could spot these emissions from as far as 5.7 light-years, slightly beyond Proxima Centauri, our nearest stellar neighbor.

Drawing closer to Earth, observers would detect additional human-generated markers at once, including city lighting, laser activities, heat islands, and satellites, altogether painting a comprehensive picture of our planet's technological footprint.

"Our goal with this project was to bring SETI back 'down to Earth' for a moment and think about where we really are today with Earth's technosignatures and detection capabilities," said Macy Huston, co-author and postdoc at the University of California, Berkeley, Department of Astronomy. "In SETI, we should never assume other life and technology would be just like ours, but quantifying what 'ours' means can help put SETI searches into perspective."

"One of the most satisfying aspects of this work was getting to use SETI as a cosmic mirror: what does Earth look like to the rest of the galaxy? And how would our current impacts on our planet be perceived," said Sheikh. "While of course we cannot know the answer, this work allowed us to extrapolate and imagine what we might assume if we ever discover a planet, with, say, high concentrations of pollutants in its atmosphere."

SETI researchers seek out advanced alien civilizations by looking for technological traces, known as technosignatures, that nature alone cannot explain. Radio telescopes are commonly employed for these searches, while optical telescopes scan for laser pulses that might signal communication or propulsion systems. A further strategy involves analyzing the atmospheres of potentially habitable exoplanets to identify possible indicators of biological or industrial processes. The study did not consider hypothesized future technologies, like Dyson spheres, which far surpass current human capabilities.

By examining Earth's full spectrum of technosignatures, this work provides a template for gauging the detectability of technology on distant worlds and guiding subsequent efforts to find intelligent life beyond our own. As observational equipment and methods continue to evolve, so will our ability to detect emerging or previously overlooked technosignatures, including further signs of atmospheric pollution. Repeating studies of Earth's changing signature over time may yield continual insights and refine our methods of discovering extraterrestrial life.

Research Report:Earth Detecting Earth: At What Distance Could Earth's Constellation of Technosignatures Be Detected with Present-day Technology?