Why don’t we encounter extraterrestrial life? Is it the Great Filter?

6 mins read

According to some theories, the reason we haven’t encountered extraterrestrial life is because these civilizations disappeared.

Scientists have different ideas about why we have yet to encounter extraterrestrial life – civilizations founded by aliens. Some of the leading researchers propose the Great Filter, based on the idea that large extraterrestrial civilizations may have already ‘disappeared’.

According to the latest thesis put forward by scientists, alien civilizations may have existed at a time unknown to humanity… The term “may have existed” is used because it is claimed that they were destroyed before we met them and it may be our turn to be destroyed. Threats such as nuclear war, climate change or pandemics could spell the end of humanity before we discover other sentient life.

Thus, the loop argument, the explanation that scientists have put forward for why extraterrestrials have not been found despite all this searching, may find support.

So what is this argument? The argument was actually put forward in 1996. The idea of the Great Filter, written by economist Robin Hanson, suggests that the reason there is no life beyond Earth is that civilization has hit a ceiling, an upper threshold beyond which it self-destructs. Dr. Jonathan Jiang, an astrophysicist at the California Institute of Technology, also makes this argument.


In fact, scientists who support this argument, including Dr. Jiang, argue that with major scientific breakthroughs such as the exploration of space, we are getting closer and closer to the ceiling called the Great Filter. “Where are they?” Hanson asked his colleagues in 1950. Shouldn’t the “vast universe be teeming with aliens by now”? “Overflowing” aside, there doesn’t seem to be anyone out there but us…

Based on this, some scientists are positive that we have not found life in space. According to this view, if we do find life close to our own, or more backward but widespread, it could mean that there is a barrier to the emergence of advanced civilizations. Perhaps civilizations are being destroyed by the wild nature of space; perhaps, as they develop, they consume their environment, their resources, or they consume themselves and their planet through warfare. At this point, Dr. Jiang puts the critical question on the table:

“Is there some kind of Great Filter awaiting every civilization that embarks on the journey of technological development, and if so, has humanity yet to face this ultimate handover ceremony? An optimistic viewpoint points to our continued existence despite the fact that we first developed the ability to self-destruct in 1945. However, the last 77 years (only an average human lifespan in the developed world) have been filled with many ‘near-extinction’ moments, so caution is warranted.”

Dr. Jiang and his team point to identifying the qualities in ourselves that could bring about the end of humanity as the key to moving beyond the Great Filter, and thereby pre-emptively neutralizing a catastrophe.

Dr. Jiang, director of California Institute of Technology’s Jet Propulsion Laboratory working for NASA, was named one of the top 20 climate scientists in the world in 2020 and has received 7 different awards and decorations from NASA in the past 17 years. Dr. Jiang’s latest paper is “Breaking through the Great Filter: Extraterrestrial Life and the Future of Humanity in the Universe”.


However, Dr. Jiang and his like-minded colleagues put forward this argument not only to start a debate, but also to spark a brainstorm. “If extraterrestrials crossed paths with us, they would probably think that the human species is very stupid because we have wars, we fight with each other, we act like children. We also have dozens of problems like climate change. From an alien’s point of view, it’s hard to understand why we are proud of our species.”

However, there are of course scientists who do not embrace the Great Filter. These researchers emphasize that humanity is still at the very beginning of its exploration of the universe. Dr. Seth Shostak, a senior astronomer at the Extraterrestrial Intelligence Research Institute, which is leading the search for life beyond Earth, says the following about the idea of the Great Filter:

“Their argument is very simple: ‘We don’t see any aliens, so something must have happened to them.’ If we think we’re the only game in town, if we think we’re the only intelligent species within hundreds of thousands of light-years, then we’re some kind of miracle. I don’t accept that idea. Science says that if you think you’re special, you probably aren’t.”

Sources: The Times, hanson.gmu.edu, arxiv.org, Is Humanity Doomed? Insights from Astrobiology (Seth D. Baum, February 2010)


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