What Does 60 Years of Silence Tell Us About the Search for Extraterrestrial Life?
Aliens have featured prominently in the news lately, encouraged by congressional hearings on Unidentified Anomalies Phenomena (UAPs), officially known as UFOs. But while the idea of aliens visiting Earth may be exciting, a better bet is the idea that aliens may exist on distant worlds. Habitable planets may exist, and it is already known that intelligent life has arisen on at least one world. But after 60 years of searching for evidence of extraterrestrial life “out there,” we have found none. So what does this tell us?
Strange as it may seem at first glance, the lack of evidence has something to teach us about the universe. Given the fact that no definitive technological radio signals from alien civilizations have been found, one cannot simply conclude that they do not exist. However, the fact that there has been silence for so long, despite decades of research, tells us something about the possibility that aliens exist, or at least that we might be able to detect them. This is the focus of a new study published in Acta Astronautica, which looks at the statistics of the search for alien civilizations to date.
The study uses Bayesian statistics to examine the probability of finding alien techno-signals. One of the key aspects of Bayesian statistics is that it assumes a focus on the likelihood of an outcome rather than the certainty of an outcome. This is the betting person’s view of the universe. In this case, there are two main assumptions: first, we know that intelligent life can evolve in the universe (at least if we assume that humans are intelligent), and second, we have not found any signals in 60 years.
To this the author adds a couple more assumptions: first, that intelligent civilizations arise at random times and in random places. In other words, Earth is not a unique place in the universe, and we are just as likely to find aliens there as anywhere else. Another is that if an alien civilization sends a signal into space, the signal could be omnidirectional, like the expansion of our radio signal spheres, or it could be directed randomly. For example, if most civilizations tend to send signals toward the center of the galaxy, it would be unlikely that we would be able to detect aliens 30,000 light years away from the galactic center.
These assumptions are quite reasonable, given what we know. At least, they are no more unreasonable than other assumptions. Based on the above, the author has found an upper bound for alien technosignatures. At best, there is a 95% probability that no more than five alien signals will be transmitted in the entire galaxy per century. In other words, there is only a 50/50 chance that Earth will discover a signal within the next 1,800 years. In other words, unless an alien civilization intentionally points a signal our way, the odds are not good that we will discover anything soon.
That does not mean we should not keep looking. But if we want evidence of alien life in the near future, it may be worth watching the congressional hearings on the UAP after all.
Source: What Does 60 Years of Silence Tell Us About the Search for Extraterrestrial Life?
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