{"id":10313,"date":"2024-01-04T09:07:17","date_gmt":"2024-01-04T09:07:17","guid":{"rendered":"https:\/\/power2innovate.com\/after-all-of-this-time-searching-for-aliens-are-we-stuck-with-the-zoo-hypothesis\/"},"modified":"2024-01-04T09:07:17","modified_gmt":"2024-01-04T09:07:17","slug":"after-all-of-this-time-searching-for-aliens-are-we-stuck-with-the-zoo-hypothesis","status":"publish","type":"post","link":"https:\/\/power2innovate.com\/after-all-of-this-time-searching-for-aliens-are-we-stuck-with-the-zoo-hypothesis\/","title":{"rendered":"After all of this time searching for aliens, are we stuck with the zoo hypothesis?"},"content":{"rendered":"
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\n\n \n The Karl Jansky Very Large Array at night, with the Milky Way visible in the sky. Credit: NRAO\/AUI\/NSF; J. Hellerman \n <\/figcaption><\/figure>\n<\/p><\/div>\n<\/div>\n
In 1950, during a lunchtime conversation with colleagues at the Los Alamos National Laboratory, famed physicist Enrico Fermi asked the question that launched a hundred (or more) proposed resolutions. “Where is Everybody?”<\/p>\n\n <\/p>\n<\/section>\n
In short, given the age of the universe (13.8 billion years), the fact that the solar system has only existed for the past 4.5 billion years, and the fact that the ingredients for life are everywhere in abundance, why haven’t we found evidence of extraterrestrial intelligence by now? This came to be the basis of Fermi’s Paradox, which remains unresolved to this day.<\/p>\n
Interest in Fermi’s question has been piqued in recent years thanks to the sheer number of “potentially habitable” exoplanets discovered in distant star systems. Despite that, all attempts to find signs of technological activity (“technosignatures”) have come up empty. In a recent study, a team of astrobiologists considered the possible resolutions and concluded that only two possibilities exist. Either extraterrestrial civilizations (ETCs) are incredibly rare (or non-existent), or they are deliberately avoiding contact with us (aka, the “zoo hypothesis”).<\/p>\n
The paper, which was recently published in Nature Astronomy<\/i>, was the work of Ian A. Crawford and Dirk Schulze-Makuch. Crawford is a Professor of Planetary Science and Astrobiology at the School of Natural Sciences and the Center for Planetary Sciences at UCL\/Birbeck College, while Schulze-Makuch is a Professor of Planetary Habitability and Astrobiology at the Technical University of Berlin, the GFZ German Research Center for Geosciences, the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, and Washington State University.<\/p>\n
The big question<\/h2>\n
As we addressed in our series, “Beyond Fermi’s Paradox,” the paradox itself actually began with astronomer (and white nationalist) Michael Hart in 1975. In a paper titled “Explanation for the Absence of Extraterrestrials on Earth,” Hart argued that given the age of the universe and the relatively short time it would take for an advanced civilization to spread across the Milky Way galaxy (650,000 years, by Hart’s estimate), Earth should have been visited by an extraterrestrial civilization (ETC) by now.<\/p>\n
In 1980, mathematical physicist and cosmologist Frank J. Tipler built on and refined Hart’s arguments with his paper, “Extraterrestrial Intelligent Beings do not Exist.” Based on the Copernican Principle, which states that neither humanity nor Earth are in a privileged position to observe the universe. Accordingly, Tipler theorized that an ETC would be assisted by self-replicating robotic explorers (von Neumann probes) that would spread from system to system, facilitating the arrival of settlers later. By Tipler’s refined estimate, an ETC would be able to explore the entire galaxy in “less than 300 million years.”<\/p>\n
This came to be known as the Hart-Tipler Conjecture, which essentially states that the absence of evidence can only be explained by the absence of ETCs. In 1983, Carl Sagan and William Newman produced a rebuttal paper titled “The Solipsist Approach to Extraterrestrial Intelligence” (aka, “Sagan’s Response”) where they argued that “the absence of evidence is not the evidence of absence” and took the Hart-Tipler Conjecture to account for the many assumptions it made. They and countless other scientists have proposed potential resolutions for why we haven’t seen any ETCs yet.<\/p>\n
The great silence persists<\/h2>\n
Nevertheless, despite decades of observation and SETI surveys, there is still no definitive evidence that advanced extraterrestrial civilizations are out there. For the most part, these have consisted of radio SETI experiments that have observed distant stars and galaxies for indications of radio transmissions. However, other SETI experiments have focused on anomalous infrared (heat) signatures that could indicate the presence of a megastructure designed to enclose an entire star system\u2014otherwise known as a Dyson Sphere (or Dyson Structure).<\/p>\n
Alas, these searches have found no compelling evidence of technosignatures within our galaxy or beyond. According to Crawford and Schulze-Makuch, the “great silence” we perceive when we look out into the universe can only mean one of two things. First, there’s the possibility that the Hart-Tipler Conjecture is correct, and there are no advanced ETC out there. Similarly, it may be that intelligent life (or life in general) is rare in the universe due to the odds being stacked against its emergence or evolution (aka, the Great Filter).<\/p>\n
If neither of these scenarios is true, we are left with only one answer: The zoo hypothesis is correct and advanced civilizations are keeping their distance to avoid being detected. As Crawford told Universe Today via email:<\/p>\n
“There are only two possibilities; either ETI exists, or it does not. As several people have noted over the years, either answer would be astonishing, yet one must be true. All we know is that we see no evidence for ETI, despite the number of planets and the great age of the universe which would, naively, seem to imply that ETI should exist and perhaps be common. This is the FP. However, if ETI exists there are only two possibilities consistent with the fact that we don’t observe them.<\/p>\n
“Either we would never expect to observe them because space is so big, etc., [or] we don’t observe them because they have taken steps to ensure that we don’t ( this is the ZH).”<\/p>\n\n \n \n \n \n \n <\/p>\n