Signals from Extraterrestrial Civilizations May Have Reached Earth but Went Unnoticed

Recent research conducted by scientists at the École Polytechnique Fédérale de Lausanne (EPFL) suggests that signals from extraterrestrial civilizations could have reached Earth but remained undetected due to our technological limitations and vast distances. The likelihood of detecting such signals increases only during searches spanning thousands of light-years.

This information was reported by SciTechDaily, which provides detailed coverage of scientific research findings. For many years, astronomers have been attempting to detect signs of extraterrestrial civilizations, specifically searching for radio signals, optical flares, or infrared emissions. These searches have been ongoing since the first SETI experiment in 1960, yet no confirmed signals have been found to date.

The lack of results is often explained by the fact that only a small portion of our galaxy has been explored. However, there is another possibility: signals may have already reached Earth but remained unnoticed. Technosignatures refer to any signs of technology originating from extraterrestrial sources, such as artificial radio transmissions, laser pulses, or excess heat generated by large structures.

For a signal to be detected, it must reach Earth, and the instruments must be capable of recognizing it. If a signal is too weak, too brief, transmitted at an unexpected wavelength, or lost in background noise, it may go unnoticed. This implies that such signals could have been passing by Earth for decades without detection.

Theoretical physicist Claudio Grimaldi modeled the implications of missed signals for current searches. He used a statistical model to estimate how many signals might have crossed Earth since 1960, creating a realistic chance for their detection today, as well as the distances from which they could have originated.

The study considers signals as emissions from distant technological civilizations in the Milky Way. These signals propagate at the speed of light and can exist from a few days to thousands of years. Earth is considered 'contacted' when a signal passes through its vicinity, but it is only recorded when it is strong enough.

The analysis revealed that for a high probability of detecting signals from hundreds or even thousands of light-years away, a significant number of signals must have already passed by Earth. In some models, this number exceeds the number of potentially habitable planets in that region, which appears unrealistic.

The probability of detection increases only when searching at significantly greater distances. If technosignatures exist for extended periods and are distributed throughout the galaxy, signals from several thousand light-years away could be noticeable. However, even in this case, the expected number of such signals at any given moment remains very low.

The authors of the study believe that the absence of discoveries in the past does not mean that a swift finding is impossible. If signals do exist, they are likely to be rare, distant, or long-lasting. This indicates that searches must be conducted over long periods and across vast regions of the galaxy, rather than waiting for a quick signal nearby Earth.