One of the great philosophical mysteries of our age is, in the words ascribed to Enrico Fermi (AKA, “the pope of physics”): “Where is Everybody?” [3] (This is known as Fermi’s Paradox, though he didn’t originate it, nor is it really a ‘paradox’. It’s still a Fermi-grade question, though.)
Humans have been watching the skies for millennia, and in the past century have looked ever wider and deeper into the universe, not to mention into physics and the biology. Everything we know indicates that there could very well be life and even technological civilizations everywhere in the vast universe. But we have never seen evidence of life beyond Earth.
Where is everybody?
Coming up with answers to Fermi’s question is a great scientific parlor game.
In 2002, Stephen Webb describes 50 answers [2], and in his 2015 update he gives 75 (!) [3]. The “solutions” listed by Webb range from “they are already here”, through “they are so strange we don’t recognize that they are there”, as well as the possibility that life really is very, very rare.
Along the way, he points out many uncertainties in our estimates of how likely the development of life and “intelligent” life may be (e.g., we have only our own planet to extrapolate from), as well as unknowable hypotheses about the possible psychology or politics of putative non-human civilizations (e.g., just because we want to talk to everyone doesn’t mean anyone wants to talk to us).
There are also disturbing warnings that “civilizations” are likely to self-destruct before escaping their home planet, or, even worse, may be snuffed out in the nest by predators or catastrophes. (With this in mind, blasting our electromagnetic presence in all directions might not have been a healthy life style choice.)
Webb’s compendium of “solutions” is fun to read, but the game is hardly over.
At the 2017 Habitable Worlds workshop, S. Alan Stern proposes yet another solution to the Fermi Paradox: most life evolves in “interior water ocean worlds”, i.e., in oceans under thick ice covers [1].
There are several such worlds in our own solar system, and at times in the past the Earth itself flirted with such conditions, covered over with a kilometer of ice.
Stern notes that these worlds appear to be highly conducive to the development of life. The ice cap protects and stabilizes the ocean environment, providing a nest for fragile life to develop over long, evolutionary periods of time. Thus, however likely life is to develop, ice worlds are prime candidates for successful evolution.
However, Stern also makes the interesting inference that life that evolved under a deep ice cap would have no direct view of the universe. The protective shield overhead would also block out most evidence of other stars and planets. An emerging civilization under the ice would not know about the universe, at least until technology develops that detects (indirectly) the space above the ice. Even then, intelligent beings might have difficulty imagining life that does not live under ice, so they might not think to look for signals from us or send signals we could detect.
Stern also argues that life adapted to an ice-covered ocean would find space travel difficult, at least compared to species adapted to the surface under a gaseous atmosphere. In addition to the technical challenge of penetrating many kilometers of rock hard ice, life-support would be necessary to support a dense, liquid environment.
He combines these arguments to answer the “Where is everybody?” question: if much life develops in ice covered oceans, and any civilizations in such environments unlikely to know or care about the wider universe, then this explains why we haven’t heard from them.
This is an interesting idea to think about. It is certainly useful to break out of the parochial idea that an Earthlike planet is the only or ideal locus for life or “civilization”. In fact, we know that life on Earth has just barely survived at least five major extinction events, and an ice world might well be a safer crèche.
I’ll also note that his comment that life on such a planet “either cannot communicate or are simply not aware that other worlds exist” works both ways. It is difficult for us to detect such inhabitants, and we haven’t be looking until recently. In our own solar system, there are several ice worlds, but we still have no idea if they are inhabited or not.
On the other hand, several aspects of Stern’s argument are less convincing to me.
An ice-covered ocean world might be a favorable site for life to start, but it might also be a closed system that is quickly exhausted. Experience on Earth certainly indicates that a closed “ark” will rapidly be overgrown, clogged, and die out. It is likely that only some ice worlds will be sufficiently “active” or open enough for life to persist. But who knows until we actually check.
I have to say that I find the arguments about the supposed psychology of native to ice worlds highly speculative, to say the least. It is true that life on Earth can directly sense the solar system and wider universe, and there are plausible arguments that this knowledge has strongly influenced the development of what we call intelligence. But it is very difficult to guess the implications of not having an open sky.
I also think that, should a technological civilization develop under an icecap, it will surely develop undertanding of the outside universe. They’ll surely learn about gravity, and when they learn to detect and manipulate electromagnetism, they’ll soon notice a lot of interesting stuff coming in through their icy roof. For that matter, no matter how difficult space travel might be, wouldn’t they deploy robot explorers and harvesters on the outer side of the ice. And from that perch, who would not look up and see other worlds?
In short, I’ll buy the idea that ice worlds are good places for life to develop, though they may not be great places to sustain life for billions of years. But I reserve judgement on questions of how the lack of a sky might influence the development of “civilizations”.
In this article, Stern describes yet one more case for why there could be some extraterrestrial civilizations that we have not seen or heard. But this clearly isn’t “the answer”. He joins the roster of all the dozens of other hypotheses (Indeed, Webb has a solution called “Cloudy Skies Are Common” ([3], p. 183), which probably subsumes Stern’s solution as a sub case.).
On the other hand, this thesis is yet more reason why icy ocean worlds are really interesting and really need to be explored.. There very well could be life under the ice, and we really should find out what we can.
We have several such worlds close at hand in our solar system that we could visit and actually see what is down under the ice. (Europa! Eceladus! Titan!)
Let’s go, already!
- S. Alan Stern, An Answer to Fermi’s Paradox in the Prevalence of Ocean Worlds?, in Habitable Worlds 2017: A System Science Workshop. 2017: Laramie, Wyoming. https://www.hou.usra.edu/meetings/habitableworlds2017/pdf/4006.pdf
- Stephen Webb, If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, New York, Copernicus Books In Association With Praxis Pub, 2002.
- Stephen Webb, If the Universe Is Teeming with Aliens … WHERE IS EVERYBODY? Seventy-Five Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life, New York, Springer, 2015.
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