Many people have a strong emotional attachment to the idea that there are extraterrestrial intelligences (ET) out there, along with a modest science basis for hope.

A matter of faith

It’s a matter of faith, more than science. Here at Mind Matters News, we have covered many hypotheses as to why we have never encountered ET. There is a science wager afoot, started this year, between astrobiologist Dirk Schulze-Makuch and planetary scientist Ian Crawford that ET will be spotted within 15 years.

Where the science part comes in

A reasonable case can be made that, in a universe of the size of ours, there should be other habitable planets, life, and some intelligent life. Fortunately, the current search for exoplanets allows us to test that idea. Some recent finds, like exoplanet TOI 700d, are quite interesting. Certainly, the search is no longer ridiculed, the way it once was.

That said, the emotional overlay — the fear of being absolutely alone forever — means that many hypotheses will continue to be offered, if only because they hold out hope.

Maybe ET was here long before us and died out?

One idea, unpacked last month at Salon, is that the ingredients for life were available in the universe long before there was life on Earth, perhaps from about 380,000 years after the Big Bang. Harvard astrophysicist Avi Loeb, known for edgy theories, told Salon that

“I would say one hundred million years after the Big Bang, there were pockets of enriched material that could have led to planets and life as we know it, potentially,” Loeb said.

Carlyn Zwarenstein, “Shortly after the Big Bang, conditions were perfect for life. Did aliens emerge long before us?,” Salon, June 15, 2024

But what about temperature? Well, he notes, the universe was smaller and warmer back then:

“In the early universe, that temperature requirement could have been met when the universe was just fifteen million years old,” Loeb said. “And that would allow liquid water to exist, or [an adequate temperature could be achieved] when it was about seventy-five million years old or so, when liquid methane or ethane would have existed just like in Titan.”

“It’s just the temperature of the entire universe because it’s filled with the radiation background, or the cosmic microwave background […] so you don’t need the object to be close to a star to attain this temperature. It would have been everywhere.”

Zwarenstein, “Emerge long before us?,”

Loeb’s not alone in this one. A recent open access paper in Philosophy and Cosmology introduces the idea of cryptoterrestrials, technologically advanced civilizations on Earth, perhaps from earlier geological eras, that are the origin unidentified aerial phenomena (UAPs), formerly called UFOs. The authors offer a number of possibilities:

This paper has made the case for taking seriously the CTH as a potential explanation for UAP, while noting that it probably ranks lower than other hypotheses, such as the extraterrestrial explanation, although such calculations are hard to quantify. To be precise, the material above actually contains four different CTHs. All would involve entities existing in stealth during recent human history – and possibly even before the emergence of Homo sapiens in some cases, such as CTH 2 – but differ in the nature of the beings in question.

1. CTH1: Human cryptoterrestrials. A technologically advanced ancient human civilization that was largely destroyed long ago (e.g., by flood), but continued to exist in remnant form.

2. CTH2: Hominid or theropod cryptoterrestrials. A technologically advanced non-human civilization consisting of some terrestrial animal which evolved to live in stealth (e.g., underground), perhaps a hominid, or alternatively a species much more distantly related to us (e.g., descendants of unknown, intelligent dinosaurs).

3. CTH3: Former extraterrestrial or extratempestrial cryptoterrestrials. Extraterrestrial aliens or our intertemporal descendants who “arrived” on Earth from elsewhere in the cosmos or from the human future, respectively, and concealed themselves in stealth.

4. CTH4: Magical Cryptoterrestrials. Entities which are less like homegrown aliens and more like earthbound angels, relating to the world inhabited by humans in ways that (at least from our present perspective) are less technological than magical, who are known in European languages by names like fairies, elves, nymphs, etc.

Lomas, Tim; Case, Brendan; Masters; Michael M. (2024). The cryptoterrestrial hypothesis: A case for scientific openness to a subterranean earthly explanation for Unidentified Anomalous Phenomena. Philosophy and Cosmology. Volume 33. https://doi.org/

The authors are two sociologists from Harvard’s Human Flourishing Program and a biological anthropologist. They are probably right to worry that their ideas won’t be taken seriously by planetary scientists.

The most boundless space of all

Here’s my perspective as a skeptical observer who tries to be sympathetic (because it would indeed be terrible to believe that we are truly All Alone in an Unfathomable Void): Happily, there is a space more boundless than the physical universe — and that space is the human imagination. The team’s ideas are best explored in good science fiction, where actual science concepts are used to develop an admittedly fictional idea: For example, a film based on the idea that ET once ruled but went extinct before, or with, the dinosaurs would have the advantage of up-to-date paleontology knowledge and special effects.

What never grows old is the belief that They are out there — one foot in faith, one in science, and a great future in imagination.