When I was perhaps 9 or 10 years old, I encountered someplace a few creepy little verses of poetry that, because of the “creepiness coefficient,” I hesitate to call a “nursery rhyme”. (Of course, many nursery rhymes and kids’ fables, in their original form, would make Quentin Tarantino look like Jane Austen.) The lines rather creep me out even today when I read or recite them:
Yesterday upon the stair,
I met a man who wasn’t there.
He wasn’t there again today;
I wish, I wish he’d go away!
At least in the popular imagination, this little doggerel could also describe the public’s fascination with the search for extra-terrestrial intelligence (SETI). By any rational estimate, the lack of evidence in favor of the existence of intelligence outside of planet Earth, combined with the stern application of Ockham’s Razor, would entail the most conservative conclusion: we simply do not know whether there is intelligence besides ourselves in the Galaxy. The physicist Enrico Fermi condensed this issue into a three-word question: Where is everybody? I propose that the reason the “little man” – green or otherwise – won’t go away, despite almost no evidence of his existence, is because Western culture, having largely ceased to believe in a god “out there,” converts its frustrated nostalgia for faith into a yearning for god-like intelligences “out there” to replace the gods we have discarded. Having alienated ourselves from belief in a god, we henceforth are more predisposed to believe in aliens.
The usual statistical argument for the likelihood of intelligent life elsewhere in the Milky Way Galaxy actually cuts both ways. You know the drill, of course, even if you have only watched a couple of episodes of Cosmos. In round numbers, the Milky Way is a disc 100 thousand light-years (ly) in diameter and 1,000 ly thick: a volume of about 7.8 trillion cubic ly (50,000 ly squared x pi x 1,000 ly) The Galaxy comprises, at a low-ball estimate, 100 billion stars. So each star occupies a space of about 78 cubic ly (7.8 trillion / 100 billion = 78 cubic light-years per star), which means the average distance between stars is 5.3 ly (78 cubic ly = 4/3 x pi x radius cubed … solve for radius ~ 2.65 ly … then the same distance to the next star centered on its ~ 2.65-ly-radius sphere … etc. … so total star-to-star distance= 2 x 2.65 ~ 5.3 ly from the center of a given 2.65-ly sphere to the center of an immediately adjacent neighboring sphere) … which tallies nicely with the sun being about 4 ly from its nearest neighbors, the dual Alpha / Proxima Centauri system. In other words, we live in a pretty average galactic neighborhood. But this is for all stars. I have read estimates of between 8 billion and 60 billion stars with planets capable of supporting any form of life. I repeat: those estimates are for any form of life from bacteria to Beethoven, from viruses to Vivaldi, from mildew to Mozart.
So let’s pick a number in the middle of that range – say, 34 billion stars – and re-run those numbers. That yields a space of 230 cubic ly per star, so that the average separation of stars with planets capable of supporting any form of life is 7.6 ly. As for intelligent life … given that we only have a “sample size” of 1 to work with, that’s anyone’s guess. Let’s suppose that, of those 34 billion stars capable of supporting any form of life, that 1/1000 of 1 percent, a proportion of .00001, are capable of eventually evolving an intelligent species. In that case, there would be only – “only” on the scale of the galaxy — 340,000 stars with planets capable of harboring intelligent life, each one occupying a space of 23 million cubic ly and an average separation of about 350 ly. But these are stars that have planets capable of supporting intelligent life, not that actually do support intelligent life. Let’s take another wild guess and say that 1/10 of 1 percent of those 340,000 stars have planets that actually support intelligent life, i.e., 340 stars with planets having life of some level or other of intelligence. That means each of those 340 stars occupies a volume of space comprising 23 billion cubic ly. This means that the average distance between worlds actually hosting intelligent life is 3,500 ly. This is still pretty close on a galactic scale: on the basis of those (admittedly and shamelessly seat-of-the-pants) estimates, intelligent species would be separated by distances of only roughly 1/30 the diameter of the Galaxy. Even under fairly pessimistic assumptions about the abundance of stars capable of supporting intelligent life, the conclusion is that, in terms of sheer distance and using the Milky Way galaxy as our yardstick, such civilizations need not be terribly distant from each other, on average.
Consequently, it would not be beyond the realm of possibility that, at some point during the 4 billion years required to evolve intelligence on Earth, (at least) one of those 340 intelligent species would have either discovered a way to modify the local spacetime metric so as to travel faster than light in the non-local reference frame — think some form of Star Trek-ian “warp drive” here — or, failing that, would have built “generation ships” that would leave their home planet and that would be piloted and navigated by successive crews (supplemented, no doubt, by hyper-sophisticated AIs, like the “Ships of the Law” in Greg Bear’s The Forge of God and Anvil of Stars) comprising the original occupants’ remote descendants. All that pertains to physically visiting other stars and star systems.
But if we relax that requirement and content ourselves with communicating instead using coded plain-vanilla electromagnetic signals, then some form of travel, physical or “virtual”, begins to seem not only possible but inevitable, given the time-frames involved. Human beings are capable of “virtual travel” now, and have been since about the middle of the last century. But I said earlier the statistical argument “cuts both ways”. That’s because Enrico Fermi’s disarmingly straightforward question intervenes. One more time … Where is everybody?Think of it this way: if alien civilizations are separated by only (again, “only” on the scale of the galaxy), say, a few thousand light-years, then within time scales imposed by the age of the galaxy (around 13 billion years) and the ages of stars therein and the time scales involved in the evolution of star systems and of life, it would be difficult to justify the conclusion that there has not been enough time for non-terrestrial life to evolve to the point of being able to communicate with, however accidentally — or perhaps even physically travel to — other intelligences … in other words, us. (You also have to remember that, in the above calculations, I am assuming that there are “only” 100 billion stars in our galaxy. While this number is realistic, the literature suggests that 100 billion may well be low. There may be 2 or 3 times that number of stars in our galaxy, and if so, the mean distance between stars, including stars that host intelligent life, would be significantly less. More stars in the same volume of space would mean that the Milky Way would be more “congested” than I assume.) Consider that in less than a hundred years, humans’ ability to transmit electromagnetic signals has evolved to the point that, to name just one example, the great radio telescope in Arecibo, Puerto Rico, can send signals that could be detected by intelligences roughly on a par with us – and receive signals from others, even if those signals were sent hundreds of thousands of years ago and were not even aimed at us. (Receiving electromagnetic signals transmitted, say, 250,000 years ago may seem fanciful. But we routinely receive such electromagnetic signals now, over distances orders of magnitude greater. These signals are usually referred to by the technical term … light.) Who knows? Maybe advanced civilizations are both stupendously rare and tend toward self-destruction after a time, i.e., “after a time” meaning “before the development of a technology permitting interplanetary / interstellar travel and colonization”. One of the coefficients of the classical Drake equation denotes how long a species survives before it self-destructs. (Nobody knows what the “shelf life” of an intelligent species is. Species homo sapiens sapiens has been around for, at most, 150,000 years – not counting earlier “models” that might arguably be termed “human”. That 150,000 years is less than one-thousandth of one percent of the life of the Milky Way Galaxy: 150,000 / 13 billion = .0000115. We arrived fashionably late to the Party.) The point of all this is not – repeat: not – that there is categorically no other intelligent life in the galaxy, but that the matter is still completely unsettled. The existence of ETI is still very much an open question.
At least, it is an open question as far as the science of SETI is concerned. But belief in extra-terrestrial intelligence in the popular culture has long ago transitioned from SETI to just ETI: the belief that the search part — the “S” in SETI – is pretty much over because … well … of course the last three letters “ETI” exist, because there is extra-terrestrial intelligence “out there”. Doesn’t the above statistical argument prove it? Of course, it does no such thing. And actual scientists – Carl Sagan, Neil DeGrasse Tyson, Seth Shostak (senior astronomer at the SETI Institute), UCLA galactic astronomer Andrea Ghez, et al. – say as much. In fact, Sagan coined the concise maxim that guides scientific SETI: Extraordinary claims require extraordinary evidence. (Sagan made this remark originally in the context of religious SETI: justifying his skepticism about alleged alien abductions by citing the lack of hard evidence.) Practitioners and devotees of the religion of SETI, as distinct from the science of SETI, would do well to have this maxim tattooed on the inner surface of their eyelids so they see it constantly. But how did SETI end up becoming a de facto incipient religion?
The short answer is that there is a cottage industry, especially in the United States, that is determined to systematically misinterpret and misapprehend virtually all major developments in science. (Similar misinterpretations and misapprehensions continue to attend relativity and quantum theory. Ditto evolution. The misinterpretations attending SETI stem from a desire to believe; those attending evolution, from a desire to not believe. But that is another rant for another time. Don’t get me started … ) SETI is just the latest such. We in the US are especially prone to this tendency because the United States is, by a country light-year, the most religious of any technologically advanced First World country. So the religious subculture of the US, at least certain segments thereof, is always looking for ways to bolster religious faith – some kind of religious faith, virtually any kind of religious faith – against what are often regarded as the insidious corruptions of secularity. (Never mind that, absent “the insidious corruptions of secularity” via the European Enlightenment, it probably would never occur to us to even ask about ETI, and we certainly would not have instruments capable of searching for it. But again, don’t get me started … ) So it is far from accidental that, if we step back and look at religious SETI from a distance, it begins to look suspiciously like conservative evangelical Christianity transposed into the key of Star Trek or Star Wars. To wit …
o The ETIs – “undocumented aliens” in the most radical sense – observe us from a distance … like the Christian God, indeed, any monotheistic god, and do so both with detachment and altruism, or at least with deistic neutrality
o The ETIs are powerful beyond all hope of merely human comprehension … rather like … well … again, just about any monotheistic deity – recalling Arthur C. Clarke’s assertion that the technology of any sufficiently advanced civilization would be indistinguishable from magic
o “They” may already walk among us, yet unrecognized as who “They” really are … rather as Christians say Jesus Christ did for roughly 33 years … except to a chosen few … again, rather like Christ is alleged to have done … see virtually any old episode of The X-Files for corroboration. Though he did not claim to be God — quite the contrary — Muhammad (pbuh) allegedly walked among his fellow Arabs initially unrecognized as God’s Final Prophet. Etc., etc., etc.
o “They” are periodically thought to abduct people in order to work “Their” inscrutable will upon them, and to return them to earth – usually, though not always – to bear testimony of “Their” existence to others not similarly privileged … rather like St. Paul on the Damascus Road or Betty and Barney Hill in upstate NH (who returned to an earthly life), and Elijah in the Hebrew Bible (who did not) – and by the way, let’s not forget the “Rapture”, shall we?
o One of the more unsettling purposes of “Their” experiments on human beings is alleged to be the inter-breeding of ETI-human hybrids … rather like Zeus’s rape of Danae, who gave birth to Perseus as a result, or the Christian equivalent of the Virgin Birth.
o At some unspecified time in the future, “They” will reveal themselves openly and publicly to humanity generally, privileged and unprivileged alike … rather like “the coming of the Son of Man,” which will be as “lightning [that] cometh out of the east, and shineth even unto the west” (Matthew 24:27, KJV) or the revelation of Shi’a Islam’s Twelfth Imam or the coming of the Person Jews would regard as the genuine Messiah.
o While “They” are generally benevolent, “They” are also capable of indiscriminate violence on an apocalyptic scale … so the movie Independence Day and the book of Revelation – to say nothing of much of the Christian Old Testament — unexpectedly sing from the same sheet of music here
o Some in religious SETI like Erich von Daniken believe that humans, not to put too fine a point on it, are just too dumb to design and build things like the Pyramids, Stonehenge, the Great Zimbabwe, Angkor Wat, Machu Picchu, the Nazca lines, etc., without help from ETIs … they are the Augustinians of religious SETI … (If the ETIs want to claim credit for, say, Stonehenge, they are welcome to do so, as long as they get the blame for Trump Tower. In fact, when I think of Trump himself, I am tempted to reevaluate my skepticism about the “they-already-walk-among-us” school of religious SETI.)
In the Pensees, Blaise Pascal wrote hauntingly in reference to the immensity of the cosmos: Le silence eternel de ces espaces infinis m’effraie (“The eternal silence of these infinite spaces terrifies me”). He is not alone in that regard. There are many human beings, even among the superficially religious, who either no longer believe in any god, or in a god who is so remote as to be of no personal relevance. Indeed, where are the gods? Many fear that, as J. R. R. Tolkien’s King Theoden of Rohan says in The Two Towers:
They have passed like rain on the mountain, like a wind in the meadow;
The days have gone down in the West behind the hills into shadow.
Then there are cranky, cantankerous old “contrarians” and avocational skeptics like me, who believe that contact with an extraterrestrial civilization, especially one far advanced beyond us, would be potentially catastrophic, if for no other reason than that it might give rise to fundamentalistic religious passion. Hey! What could possibly go wrong with that?
I close by again quoting Arthur C. Clarke Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying. The “little man” may be on the stairs. Or in the stars. Or neither. His presence and his absence are alike equally haunting. But even if he doesn’t exist, we will probably have to invent him.
James R. Cowles
Radio telescopes … European Southern Observatory (ESO) … Creative Commons Attribution 4.0 International
Milky Way galaxy … Nick Risinger … Public domain
Seth Shostak … B. D. Engler … Creative Commons Attribution 3.0 Unported
Andrea Ghez … UCLA Newsroom … Public domain
Stonehenge … Diego Delso, delso.photo … License CC-BY-SA