One of the main goals of astronomers is to understand the potential for life elsewhere in the universe. Despite extensive exploration, space agencies such as NASA have yet to find credible evidence of extraterrestrial life.
A recent article published in theAstrophysical Journal proposes a compelling hypothesis as to why advanced extraterrestrial civilizations might be difficult to detect. According to the study, if such civilizations exist, their energy needs may be relatively modest. This means they would not need to build huge facilities to collect stellar energy, which could be detected by our telescopes..
These structures, based on our technological trajectory, could include vast arrays of solar panels or orbiting megastructures designed to harness the majority of their parent star’s energy. Ravi Kopparapu, of NASA’s Goddard Space Flight Center and lead author of the paper, explained: “We found that even if our current population of about 8 billion were to grow to 30 billion with a high standard of living, and we used only solar energy, we would still use far less energy than all the sunlight that illuminates our planet..”
This study has significant implications for the Fermi paradoxwho wonders why, given the age and immensity of our galaxy, we have not yet encountered any alien civilizations. Kopparapu suggests that civilizations may not feel compelled to expand across the galaxy if they reach sustainable levels of population and energy use.. They could expand within their star system or into nearby star systems, but civilizations that span the galaxy may not exist.
Vincent Kofman, co-author of the article, added: “Large-scale facilities for harvesting stellar energy may be obsolete given technological advances. A society capable of placing massive facilities in space will likely turn to nuclear fusion or other more efficient methods of generating energy in space.”
The researchers used computer models and NASA satellite data to simulate an Earth-like planet with varying levels of silicon solar panel coverage. They found that detecting solar panels on a planet about 30 light-years away would require several hundred hours of observation with an advanced telescope like NASA’s proposed Habitable Worlds Observatory.. However, the energy needs for 30 billion humans with a high standard of living would require only about 8.9% coverage with solar panels.
The study hypothesizes that aliens would build solar panels out of silicon because of its abundance and efficiency. However, if other energy sources such as nuclear fusion were used, this would reduce the silicon’s technosignature, making the civilization even more difficult to detect..
The modest energy needs and potential technological advances of extraterrestrial civilizations may explain why we have not detected any technological signatures so far.
Image credits NASA/Jay Freidlander
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