One of the major tropes of science fiction is the Alien. Recall Lummox, the Rull; the People; Tweel; and so on. These alien folk have served admirably as metaphors for various aspects of humanity or human societies; but as one mainstream critic supposedly noted with surprise, in SF a trip to Mars is not only a metaphor for the human condition, but is also supposed to represent on some deep level an actual trip to Mars. If this is so, then we have a problem.
Where are the aliens?
Aliens qua alien
Of course, by alien life we do not really mean a layer of lichen floating on the torpid seas of some far-off world. That would be Way Kool, but it sure ain't why we're looking.
When Fermi famously asked the question, "Where are they?" he didn’t mean where are the mud worms of Yuts'ga? By all accounts, they aren't going anywhere. But according to incantations – I mean, calculations – there has been plenty of time for Others to make it here. So why haven't they shown up? Where are the flying saucers, or at least the messages from Mars?
The basic incantation is something called the Drake Equation, which is disguised to look like a real equation, perhaps in the hope that no one will notice that most of the terms in it are not even remotely measurable. The equation runs:
N is the number of civilizations in our galaxy with which communication might be possible;
R* is the average rate of star formation per year in our galaxy
fp is the fraction of those stars that have planets
ne is the average number of planets that can potentially support life per star that has planets
fℓ is the fraction of the above that actually develop life at some point
fi is the fraction of the above that develop intelligent life
fc is the fraction of civilizations that develop a technology that releases detectable signs of their existence into space
L is the length of time such civilizations release detectable signals into space
The fraction of stars with planets is looking good. We've already detected a fair number of exoplanets. However, most of those planets are Hot Jupiters whirling like centrifuges way too close to their home-stars. This does not bode well for ne. Of course, that’s an artifact of the detection method, which is biased toward large planets and proximity to their stars. It wouldn’t know Mars from a hole in the ground. Nor is the on-going failure of SETI encouraging fℓ and other factors. But it only has to cry Bingo! once.
There are three basic answers to Fermi's Paradox:
I. They’re not there
II. They're there, but not here
III. They're here, but we don't know it
Let’s look at these in detail.
I. They’re not there.
1. We're it. Unique in the universe.
What a waste! All that great big honkin' universe out there and we're all there is? But, why should there be anyone else in the universe, regardless of its size? How many dandelion seeds are scattered to make a single dandelion? How many stone chips litter the workshop to make one statue? Why should it not take a universe to make a world? If the mass of the universe were much less, it would have expanded into vichyssoise long ago. If it were much greater, it would have collapsed back on itself before anything could get started. This is how big a universe must be to make galaxies, stars and petunias, whether one world or a gazillion be inhabited.
2. We're first. We are the "elder race" of the universe.
Well, someone had to be first. Why not us? Life is hard and maybe the start-up costs are too high. As far as we can tell, life only happened once here on earth. If it's so easy and automatic, why did it not happen here twice, perhaps in different deep sea thermal vents?
Hydrogen, helium, and lithium are easy to come by, but life seems to need some heavier elements, like carbon and oxygen or silicon and chlorine, and that requires several generations of stars, not only to forge the elements, but for supernovae to spread them across vast distances and gravity concentrate them in planets.
Besides, out there is also back then. All those gazillions of distant galaxies? Those were gazillions of years ago. Any signals coming from them would have had to have been sent when the universe was young, before any life-soup had cooked up. The universe might be teeming with species right now busily putting out daytime soap operas and other indications of intelligence; but we don't hear the universe right now. We hear the universe that was way back then.
3. We're last. They were there, but not anymore.
C'est le vive. That L factor in the Drake equation is really, really short.
- They wiped themselves out in wars of annihilation.
- The plague got 'em.
- Famine got 'em
- The glaciers got 'em.
- The von Neumans got 'em (and are coming our way).
- They all became dependent on government handouts and then the government went bankrupt.
- They mucked up their environment a bit too much and choked on their own pollution.
- They genetically modified themselves and screwed up, bad.
- They downloaded themselves into computers and there was this power bump…
- They adopted an existentialist, materialist philosophy, saw no reason for going on, and drank the Kool-Aid.
II. They're out there, but not here.
4. Their Cambria never exploded. They got to prokaryotes but prokaryotes are unlikely ever to make interstellar contact. To step up to eukaryotes, with their highly structured cellular composition, competing prokaryotes would have to combine into a single entity. This requires
a) cooperation in a “network of mutual dependencies,”b) the emergence of a functional unit comprising all individuals involved in the network, andc) the development of a boundary to bar or expel stragglers.
This results in a higher-level of competing replicators. This is more than “descent with modification” and may be a correspondingly more rare process.
5. They’re all wet. They never got out of the water to see the stars.
No one will try to contact us if they have no idea there is any 'us' to contact. Life may need water chemistry to originate, but it needs dry land to get good telescopic views of the rest of the universe. Technology seems to have started with Fire, and it’s hard to conceive of fish discovering fire. But this only matters if there is land onto which to crawl. Water worlds need not apply.
6. They were never mooned. No one else has a moon/planet ratio large enough to create tidal pool escalators onto the land. That may not be the only way for fish to transition to amphibians, but it is the way it seems to have happened here. Nowhere else we know of is there a sufficiently-sized planet with such a relatively large moon. It required, so theory says, a Mars-sized body striking the proto-earth in just the right way to slice off a moon-sized divot into the proper orbit. Of all the unlikely things that led to life on Earth, this may have been the unlikeliest, and there is no term in the Drake Equation for it.
7. They’re sessile. Aliens are plants and fungi and don't get around much.
Don't expect the flying saucers to land, lower a ramp, and weeds or mold to start growing down the ramp to meet us. Waiting dignitaries won't wait that long. Plants and fungi don’t move, they grow, and you can't grow your way from α-Centauri to here. Fungi probably won't build powerful radios, either. In fact, sessiles are unlikely even to be sentient. After all, what’s the point of sensation if you can’t do anything about it? If grass senses thirst, it can’t exactly pull up roots, pack up the wagon, and set off for the other side of the fence, where it is proverbially greener. All it can do is dry up, wither, and wait for rain. So, there is nothing upon which Darwinian selection can operate.
8. They’ve got brains, but not a brain. The aliens are of two minds about things because their two brain hemispheres never knitted into one. More broadly, their sundry sensory inputs are not melded into a single ymago. Thus, they lack imagination and hence memory, so they cannot “see” a petunia that was present even moments ago.
9. They don’t have much to say. The aliens get along fine with imagination. Like every other animal species on Earth, they can learn and remember in response to sensation. They have personalities, can use tools, can sometimes even make tools. But in the past billion years or so, none have come up with disco or daytime soaps, let alone art, speculative philosophy, systems of mathematics, or physics. These require intellect, the capacity to abstract [lit. “pull out”] universals from particulars. They can grasp this petunia and that petunia and the other petunia; but they do not grasp “petunia.” Hence, they lack language.
10 The Endless Sumer. Aliens achieved Sumerian-level civilization and never broke out. Velocity needs no cause; inertia is the norm. It's change that requires a mover. Once there was a breakthrough to civilization, the aliens chilled. Looking back on the Eden that was their pre-intellective, pre-civilizational existence and comparing it to the Vale of Tears in which they ate by the sweat of their brows [or brow-equivant], the aliens figured why take any more chances? The same goes for other rest-points along the way. For example:
- Humanism triumphs. The aliens are excellent artists and literary critics. But they are not ham radio operators and do not form amateur rocket clubs
- Bureaucracies triumph and new technology is not covered by any of the procedures.
- God-kings triumph. The aliens spend their lives preparing the king for his afterlife. If you’re good, he’ll save you a spot.
- Oligarchies triumph. Everything is geared toward the maintenance of power. New technology may shift the power balance. Can’t have that.
- Democracies triumph. They got to their moon, then quit and spent the money on themselves.
11. They're not into science. The aliens never cared about the natural world. They tinker, but rules of thumb can get your technology only so far. Further development requires a serious study of nature qua nature. There are many reasons why the aliens do not develop a natural science.
- They're not curious. Most Terran cultures were markedly incurious about the natural world, even while they devised many practical and useful rules of thumb. [e.g., If you beat the drums during a solar eclipse, the sun will eventually return. What if you don’t beat the drums? Why take such a crazy chance? You may sense the limitations of such an approach.]
- Circular reasoning. The hypnotizing circular motion of the heavens convinced them that the world is a series of repetitive cycles. Everything that has happened will happen again. Natural laws are transient.
- They believe there is no God, so chaos and unreason are at the root of everything. Natural laws are illusions or coincidences.
- They believe there is a host of competing and contradictory gods. Natural laws represent temporary compromises among these gods.
- They believe there are dryads in the trees, nymphs in the springs, and the stars are alive, divine, and influential in daily life. If nature has minds of her own, she must be placated, not studied.
- They worship the phallus. This interferes with thinking straight.
- They believe there is a creator God, but he is not rational. Therefore, the created world is not rationally ordered.
- They believe there is a creator God, but he does not act through nature. Apparent natural laws are simply “the habits of God.” He might change his mind.
12. They are stoopid. Sure, the world is ordered, but they do not believe their reasoning powers are competent to grasp it.
13. Aristotle? Who he? They never invented a systematic science of nature. They collect curious facts about nature but that’s it. But a curio cabinet doesn’t lead to interstellar contact.
14. They’re empiricists. Newton’s laws never occurred to them because they’ve never seen an astronomical situation consisting of only two bodies. The same goes for perfect vacuums, frictionless surfaces, new species, etc. Believing only in what they can sense, they never mathematized their natural science.
15. They’re chemists. Their scientific interests led them into chemistry (and biology) and not physics. They popped off some chemical rockets, but they have no radios or anything like them. Interstellar communication by lighting off flares is not likely to be very effective.
16. They all went fiber-op. They’re out there. But they gave up on E/M broadcasts. We'll never hear from them unless they run cable out our way.
17. They stink. They communicate by odor or other means unsuited to long-distance transmission. It’s hard to read sign language from α-Centauri, even if they have very big hands.
18. It’s a really long way to Tipperary. The distances between intelligent species are too daunting. The senders will be long gone by the time the receivers get the message. So why bother?
19. Missed call. They did send a message; and it reached Earth already, but the Devonian fishes lacked proper receivers.
20. Wrong way, Corrigan. They developed interstellar travel, but they went the other direction.
21. They're en route. We live at just that cusp between the launch of their interstellar probe and/or radio signals and their arrival here.
III. They're here, but we don't know it
22. We're quarantined. They don't come or talk to us because we have cooties.
23. We're quarantined. They don't come or talk to us because they have cooties.
24. We're boring. They made it here but don't come or talk to us because they don't find us interesting. They detected our TV shows and fled in horror.
25. They’re boring. They're here but don't come or talk to us because they have nothing to say.
26. They're quiet. They're here but observing only.
27. They're incognito. They're here but disguised as humans.
28. They're really incognito. They're here but disguised as cats.
28. They're really really incognito. They're here but hiding in plain sight as Real Housewives.
29. They're practical jokesters. They're here but they only contact people driving on deserted country roads whom they probe and release.
30. They're gods. They were here. Long ago. And they over-awed the natives, who called them gods.
31. We missed them. They were here. Long ago. Dinosaurs ate them. Then they smashed all the dinosaurs with a comet.
32. They were here, recently. ICE rounded them up, put them in detention camps, then deported them on buses as illegals. They were last seen in the Oort Cloud fiddling with some comets.
33. They love us. They're here, but they don't want to interfere with our natural development.
34 They hate us. They're here, but they don't want to interfere with our natural development.
More careful study may fine tune this taxonomy. Faithful Readers will naturally try to subvert each and every one of these scenarios. Perhaps aliens who operate by instinct alone may indeed contact us; or a ship piloted by fungi may land Real Soon Now. An alien living in secret on Earth may even run for President of the US of A and, depending on one’s taste in aliens, either win or almost win. Perhaps there is a loophole by which aliens limited to the water may yet develop an astronomy and learn of the stars and try to contact putative beings who live there.
Of course, that makes the Fermi Paradox even more difficult to explain.