A Brief-ish History of SETI. Part VIII: Paradox? What Paradox? - Universe Today

This illustration shows a hypothetical distant planet inhabited by a technological civilization, with “city lights” visible on the darkened surface. Credit: NASA/JPL-Caltech/Lizbeth B. De La Torre

Welcome back to our continuing series, a Brief-ish History of SETI. In our previous installments, we examined the origins of the Search for Extraterrestrial Intelligence (SETI) and the earliest experiments. We then looked at the first modern SETI project (Project Ozma) and what is arguably the most foundational principle in the search (The Drake Equation). Then we examined big ideas about how advanced extraterrestrial civilizations (ETC) would look and what technologies they would come to rely on.

This was followed by a look at the first attempt at Messaging Extraterrestrial Intelligence (METI), the Arecibo Message, and what is considered the best candidate for an ET signal to date (the WOW! Signal). Then we looked at the Pioneer Plaques and the Voyager Golden Records, humanity's first attempts to send "messages in a bottle" that might be found by ETCs someday. We then considered two additional principles that are foundational to SETI: the Fermi Paradox and the Great Filter.

Last, we examined how communicating with ETCs might be subject to "brief windows" due to species mortality or technological transcendence. Today, we will consider how scientists in recent years have come to question many of the principles and assumptions inherent in SETI. We will also examine modern attempts to revitalize the field using the most advanced technologies and methods to date.

*Artist's impression of the Arecibo array and radio antennas worldwide detecting the Lorimer Burst. Credit: Danielle Futselaar*

Not a Paradox

Since it was first proposed, the Fermi Paradox has inspired more than 50 proposed resolutions. At the same time, it has inspired criticism from scientists who question the many assumptions upon which it is based. For instance, the Paradox assumes that extraterrestrials should have already emerged, that technological advancement is the norm among intelligent species, and that intelligent life is subject to exponential growth. But perhaps the sharpest criticism concerns the fatalism inherent in the original proposal.

These arguments were summarized brilliantly by data analyst, author, and astronomer Robert Gray, who is perhaps best known for his book The Elusive Wow: Searching for Extraterrestrial Intelligence. In his 2016 essay, "The Fermi Paradox is Neither Fermi's Nor a Paradox," he criticized two problems with how the Paradox was framed. First, he argued that the Paradox did not originate with Fermi's question, but with Michael Hart:

Enrico Fermi, however, never published anything on this topic. On the one occasion he is known to have mentioned it, he asked “where is everybody?”—apparently suggesting that we don’t see extraterrestrials on Earth because interstellar travel may not be feasible, but not suggesting that intelligent extraterrestrial life does not exist, or suggesting its absence is paradoxical.

Second, he addressed another issue scientists have raised repeatedly: that the disparity between the assumed prevalence of life in our Universe and the lack of evidence for it does not constitute a paradox - but rather a conundrum. What's more, Gray indicated that Hart himself selected the term for publication and used only single quotations "as an apology for using a short, convenient two-word label for a large and indistinct field of conjecture."

Above all, he recommended adopting a new perspective that clarified the origins of the ideas behind the Paradox. As he said, this was important because:

[T]he Fermi Paradox is seen by some as an authoritative objection to searching for evidence of extraterrestrial intelligence—cited in the U. S. Congress as a reason for killing NASA’s SETI program on one occasion—but evidence indicates that it misrepresents Fermi’s views, misappropriates his authority, deprives the actual authors of credit, and is not a valid paradox.

*Enrico Fermi, whose famous question remains foundational to SETI. Credit: Nuclear Heritage Foundation*

In truth, Fermi's Paradox, defined not by the question but by the statement "we don't hear from them, so they don't exist," is properly known as the Hart-Tipler Conjecture. A more accurate description would be Fermi's Question, which addresses the disparity between the assumption abundance of intelligent life in our Universe and the lack of contact with it. This conundrum supports no conclusions, only speculation based on a sample of one - humanity.

As David Brin said in his 1983 essay, "The 'Great Silence': the Controversy Concerning Extraterrestrial Intelligent Life": "Few important subjects are so data-poor, so subject to unwarranted and biased extrapolations - and so caught up in mankind's ultimate destiny - as is this one."

Interestingly, modern...