As each day passes with no word from extraterrestrial intelligence, one has to wonder why, if alien life is so probable, have we not seen some sort of sign by now? This dilemma, commonly referred to as the Fermi paradox, may seem like a disheartening observation at first. However, it is a problem with many possible solutions, and the lack of extraterrestrial evidence on Earth does not mean that humans are the only intelligent beings in the universe.
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While out to lunch with his friends in 1950, acclaimed physicist Enrico Fermi made a simple remark that would spark fierce debates in the search for extraterrestrial intelligence (SETI) and messaging extraterrestrial intelligence (METI) for years to come; “Where is everybody?” Fermi was questioning why there is no evidence of intelligent extraterrestrial life on Earth, if the galaxy is supposedly riddled with civilizations. According to Physicist Herbert York, also present at this lunch, recounts that Fermi concocted some possible solutions to this so-called paradox himself; “[H]e went on to conclude that the reason that we hadn’t been visited might be that interstellar flight is impossible, or, if it is possible, always judged to be not worth the effort, or technological civilization doesn’t last long enough for it to happen.” Even after his sobering revelation, Fermi still believed in the possibility of intelligent extraterrestrial life and started devising solutions, as others continue to do to this day.
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One of the most popular theories is the “sustainability solution.” The sustainability solution focuses on the ability of another intelligent civilization to travel across the galaxy, and even colonize planets, based on the restriction of finite cost, energy, and resources. It argues that that intelligent life may not have the resources for interplanetary travel, or does not find it a practical use for the resources they do possess. To put this in perspective, consider that, according to the SETI Institute’s website, it would cost over $40 billion just for Earth to send a rocket to Alpha Centauri, the next star system over. A colonizing civilization would also need to bring enough people and resources to both settle on a planet and continue traveling into space. There is a very substantial time investment as well, because even if extraterrestrials had spacecrafts that traveled at the speed of light, it could still take hundreds of thousands of years to travel through the Milky Way. In their article “The Sustainability Solution to the Fermi Paradox,” Jacob D. Haqq-Misra and Seth D. Baum argue that, “[G]rowth in resource consumption must not exceed growth in resource production,” and compare a trek across the stars to the human trek across Earth. They point out that a civilization drops in number once all available resources are consumed, as was seen with the diminished population of Easter Island. Therefore, using resources and energy to travel to other planets may be viewed as unnecessary or wasteful by any capable civilizations.
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Another favoured solution to the Fermi paradox is the Great Filter hypothesis. This concept proposes that, at some point in a civilization’s development, there is a barrier that is difficult for life to overcome. This would suggest that there are far fewer intelligent extraterrestrial civilizations than previously hypothesized, or that our time of existence may not overlap with other civilizations. A filter in our past would indicate that the conditions to develop life are a lot less likely than we think. Perhaps we are one of the first civilizations, or even the first civilization. This could also be a result of the galaxy being too hostile harbour life in the past. Barriers in our past could be the jump from prokaryotic cells to eukaryotic cells, or the development from semi-intelligent life to intelligent life (i.e. evolving from chimps to humans). If the Great Filter is ahead of us, that could mean that life at our level of development, or even beyond us, exists, but is eventually demolished by an unknown factor. Possibilities include a regularly-occurring natural disaster, a technological advance that destroys humankind, and mutually assured destruction between extraplanetary civilizations. The philosopher Nick Bostrom points out that if discovering life on Mars would be very disheartening, as it limits the possibility of the Great Filter in our past, thereby increasing the likelihood of a future obstacle.
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The final solution to the Fermi Paradox that I will talk about is the possibility that our communication techniques are too primitive or different to contact other civilizations. From artifacts placed aboard spacecrafts, such as the Pioneer plaque or the Voyager plates, to radio signals, such as the Arecibo message designed by Carl Sagan, our abilities to communicate with extraterrestrial life could still be considered rudimentary. Even if another civilization was looking for our signals, they might not be able to pick them up. Or extraterrestrial intelligence could be sending signals to us, but we are missing them. Considering how much technological advancement we have made in the past century, a civilization that is only a couple hundred years older than us could have made inconceivable leaps in communications technology that are incompatible with radio signals.
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While the sustainability solution, the Great Filter hypothesis, and potential communication problems appear to be the most widely accepted solutions to the Fermi paradox, there are a number of other theories. For example, the Zoo Hypothesis supposes that more advanced civilizations are aware of Earth but have decided to observe instead of interfere or make contact. Other theories include the idea that aliens have already visited Earth, as evidenced by the thousands of UFO sightings every year, or that extraterrestrial life visited Earth at a point where humans had not developed yet, as we have only been around for 50,000 years; a relatively short time in the history of the universe. It is also theorized that the reason no one is sending out messages is because there are predatory civilizations that destroy any intelligent life, and we are too ignorant to stop. This is one of the reasons that both Stephen Hawking and Carl Sagan are wary of METI, and Sagan even described it as a “deeply unwise and immature” practice. And the final, rather disheartening solution, is that, perhaps, we truly are all alone in the universe.
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While the Fermi paradox may seem disheartening at first, there are many possible answers to the, both scientific and philosophical, question, “Where is everybody?” Solutions such as the sustainability problem, the Great Filter, and communication issues all explain why humankind has not come in contact with any extraterrestrial intelligence yet. And these are only three of many possibilities. Ultimately, there is a vast number of potential explanations, none of which have or can be proven correct until we are presented with concrete evidence. And perhaps extraterrestrial civilizations are reaching out, as seen in the 1977 “Wow!” signal or more recent strong signal from deep space discovered in 2016. In fact, the senior astronomer at the SETI institute, Dr. Seth Shostak believes, “[W]e will find a signal from intelligence within two dozen years. I’m very confident [life is out there]. Otherwise, Earth has won the lottery, and that seems too remarkable for me to believe.”
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Sources:
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https://arxiv.org/pdf/0906.0568.pdf
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http://www.wired.co.uk/article/fermi-paradox-alien-life-universe
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http://www.space.com/30043-seti-search-for-extraterrestrial-intelligence-infographic.html
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http://waitbutwhy.com/2014/05/fermi-paradox.html
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https://www.seti.org/seti-institute/project/details/whats-blocking-galactic-civilization
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