Even if aliens exist in our galaxy, they are probably about 33,000 light-years away: Researchers
The possibility of finding extraterrestrial civilizations may be more remote than previously thought, according to new research presented at the EPSC–DPS2025 Joint Meeting. A study suggests that the nearest technologically advanced species in the Milky Way could be located as far as 33,000 light-years from Earth, as per Euro Planet.
The findings, presented by Dr. Manuel Scherf and Professor Helmut Lammer of the Austrian Academy of Sciences, indicate that the odds of finding life similar to our own are slim. Their research factored in the specific planetary conditions necessary for advanced life to evolve, including plate tectonics and a finely balanced nitrogen-oxygen atmosphere. “Extraterrestrial intelligences – ETIs – in our galaxy are probably pretty rare,” says Scherf, suggesting that the conditions for fostering a long-lasting, technological civilization are exceptionally specific.
The study points to a planet's atmospheric composition as a key factor. Planets require a delicate balance of carbon dioxide to sustain photosynthesis and prevent a runaway greenhouse effect. Plate tectonics plays a crucial role in this process by regulating atmospheric CO2 levels. However, as CO2 is gradually locked away in rocks, a planet's ability to support life eventually wanes. “At some point, enough carbon dioxide will be drawn from the atmosphere so that photosynthesis will stop working,” Scherf noted. “For the Earth, that’s expected to happen in about 200 million to roughly one billion years.”
Furthermore, the research highlights the critical role of oxygen. The study notes that a habitable world would need at least an 18% oxygen concentration to support both complex animal life and the development of metallurgy, a prerequisite for a technological society. By combining these factors with the time it takes for technological life to evolve, the researchers concluded that any co-existing civilizations would have to be incredibly long-lived. For even one other civilization to be active in the galaxy at the same time as ours, it would need to have survived for at least 280,000 years. If ten civilizations were to exist concurrently, their average lifespan would need to be over 10 million years.
This implies that any alien intelligence we encounter would likely be far older than humanity. These calculations led to the estimate that the nearest technological civilization could be 33,000 light-years away, potentially on the opposite side of the Milky Way from us. Despite the pessimistic outlook, Dr. Scherf emphasized the continued importance of the Search for Extraterrestrial Intelligence (SETI). “Although ETIs might be rare, there is only one way to really find out, and that is by searching for it,” he said, noting that a successful search would represent one of the most significant scientific discoveries in history.
These new findings offer a potential explanation for the cosmic silence that has long puzzled scientists, a question famously known as the Fermi Paradox. As per Space.com, the paradox, named after physicist Enrico Fermi, highlights the contradiction between the high probability of extraterrestrial life existing in a vast and ancient universe and the lack of any observable evidence. While billions of potentially habitable planets exist, humanity has not yet detected any signs of a technological civilization.
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