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The Fermi paradox revisited
I am still thinking about Nick Bostrom's stimulating essay (and Robin Hanson's precursor essay). Nick of course is worried about finding signs of alien life, which would suggest that life has arisen many times, leading to the question "where are they?" and the fear that life dies out pretty easily. For Nick it is cheerier, from our point of view at least, to think it is very hard for life to get underway in the first place.
In pondering the Fermi question, I often wonder if I am not simply missing the party, so to speak. Most people already *do* think they see signs of an alien presence of some kind, of course defining that concept broadly to include The Gods. So how can we say we don't see "them"? Maybe I, the agnotheist, don't see "them" (Him?) but surely most other people think they do.
Doesn't that make the Fermi paradox go away in a snap? No one cites Blind Boy Blake and screams "He doesn't see them!".
Another way of putting it is to say we don't take David Hume's Dialogues on Natural Religion seriously enough. We really have just one data point, so who can say what "they" look like, or what kind of "display" they would have made for us?
Alternatively, I am struck by the tension between the Fermi paradox with the "We are probably living in a simulation" claim. Both are popular with the same group of people because they are nerdy ways of making you believe something weird; in reality the two conundrums don't fit together. If you take the simulation option seriously, you again see the creators all around you, albeit in disguised or cloaked form. Of course you had to use Bayesian inferential reasoning to see them, but what's wrong with that? Better than a telescope, some would say. And since most people believe in God, the creators might even consider their artwork to be already "signed." (I'll note rapidly in passing that the arguments against the simulation hypothesis also strike at the Fermi worries, but establishing that would take lots of work.)
Either way, it seems we see "them," or ought to think we see them, even if that turns out to be a visual mistake of sorts.
Addendum: I liked Michael Goodfellow's point:
After that first species gets control, it makes all the rules. If it shells over all the stars, no other life can even develop, since all the planets are frozen solid. If it wants to let biological evolution continue, it can do that, by avoiding stars with fertile planets. It can prevent any other technology from arising (by monitoring all the planets where life is evolving.) It can guide or change any life that it does find.
This may seem horrible to you -- little robots putting all the stars out! Spreading like a weed and killing or preventing any new life from developing. But you're looking at it the wrong way...The first species out there gets to decide the future, for every species that follows. For lack of any other evidence, let's hope it's us.
Splendid, but I part company at the last sentence. There is some other evidence (of the Bayesian sort) and I think the most logical assumption is -- whether you believe in God or space aliens -- to think of ourselves as their product, one way or another.
Or to put it yet another way, what's the principle of individuation here? Isn't "seeing us" and "seeing them" more or less the same thing?
Hail David Hume!
Posted by Tyler Cowen on May 8, 2008 at 06:40 AM in Science | Permalink
Comments
Goodfellow's point is only valid for high values of "control." In other words, it's circular; he's essentially saying, "After that first species gets sufficient control to make all the rules, it makes all the rules."
But why would we expect one species to accumulate that much control? If you substitute "nationality" for "species," it's clear that no nation has ever achieved that level of control over the world. The galaxy might be different, but why?
Posted by: Tom T. at May 8, 2008 8:08:59 AM
"This may seem horrible to you -- little robots putting all the stars out! Spreading like a weed and killing or preventing any new life from developing."
This version was covered in disturbing fashion in Barnes' "Enrico Fermi and the Dead Cat", with a nice twist.
Posted by: Bernard Guerrero at May 8, 2008 8:22:27 AM
We have met the Other, and he is us? I am uncertain whether Walt Kelly would be proud.
Posted by: Cyrus at May 8, 2008 8:57:04 AM
Easy theory to test.
Build a partial dome around our earth, build it in space, make is a 300 meter diameter mirror. Then do spectral analysis of observed point planet sources.
If we cannot detect moss growing somewhere, then we can narrow down some associated Fermi constant of detectability.
Posted by: Matt at May 8, 2008 9:07:35 AM
Tom,
I think the difference is that every nationality that the world has produced has been in constant contact with at least some other nationality. This has allowed technology to disseminate from nationality to nationality. Once one species gets out there moving from star to star (if this is even possible) it will be encountering species that have been on completely different development tracks. The only thing that comes close in the history of the Earth would be something like the period from the 1400's to the 1900's when the European powers developed technology that allowed them to move across the ocean and directly interfere with the affairs of cultures and nationalities that were several hops farther away on the dissemination ladder than had ever happened before. I would say that there are a lot of examples from that time where some nationalities got to set all the rules for at least a little while.
The experience of imperialism is missing a lot of the non-symmetries that a cross star systems meeting might include; thousands or tens of thousands of years difference in technology, orders of difference in brain mass, orders of difference in thought speed, etc.
Posted by: Lucas at May 8, 2008 9:21:35 AM
What I don't understand is the obsession with one single Great Filter. Its all about how improbable something is, such that it requires a long enough time period to roll the dice a sufficient number of times to get life that you end up with only one planet with life in the observable universe. But, lets call that improbability X. Then you could just as easily have 5 filters - five Semi-Great filters (steps) each 1/5 as improbable as the One Great Filter that he discusses. If you have to overcome all 5 in order to communicate, but all of them are tough - maybe not exactly equally - then you could easily not have any life form having overcome all 5 but several having overcome one or more.
He named a bunch - life from the right conditions, prokaryote to eukaryote, single cell to multi-cell, and so on, and then any future ones.
Why think that any one of those is drastically more improbable than the others and constitutes THE great filter? It seems more likely to me that each of them is improbable and maybe correlated with how long the step took, maybe not (it is probabilities we are talking about).
In this scenario:
(a) Finding past life on Mars does not mean that THE great filter is ahead of us. Perhaps they surmounted one hurdle but then failed to surmount the second. Maybe there are even 5 planets in the observable universe that surmounted one; maybe one of them is still going (us) or maybe even two.
(b) There may be trouble ahead, there may not. We managed to surmount several obstacles, we may or may not surmount any future ones. Other planets may have life at any one of these stages; and in a billion years maybe one of us will finally surmount the obstacle that allows us to communicate - maybe we're close.
(c) Non-observable universes and time frames prevent us from knowing exactly how often life has been able to reach out aliens - it may be happening now in an unobservable place, it may have happened many billions of years ago. Hence, I don't think we can do the exact numbers to know how improbable each event must be, and hence we can't conclude whether we have already surpassed them all (and hence should have no fear of a future Filter) or that we must not have, and there must be a Filter ahead if life was found on Mars.
(d) There is also the possibility that there are multiple possible dangers that could destroy the system at each Filter-step; not just a possibility-hurdle that must be overcome. If this is true, then one of the dangers could destroy the life form entirely, while another could just throw it back to the last stage, and so on. This would change the probabilities, so that it would be (even) more likely to find life forms having overcome one or more but not all 5.
I like the living in a sim article too, although I thought the second page was meandering away from it a bit; too much speculation.
Posted by: liberty at May 8, 2008 10:18:29 AM
As for the sim idea actually, I feel like the idea that this is a virtual reality, experienced exactly the same as if it were real, is fun but silly naval gazing: what difference does it make?
If we experience it the same then we experience it the same. If God is a computer nerd from 3500 AD, then thats "God". Maybe if you are 100% certain that science as currently understood and evolution is all there is, then this speculation would make a difference, but for those of us who don't know, it seems like just another God hypothesis without any real implications.
Posted by: liberty at May 8, 2008 10:24:24 AM
I echo what "liberty" said regarding multiple Great Filters. I think that it is also important to consider that many of the Filters may act as crucibles for the species that survive them. Without Filter N, the strains that will not survive Filter N+1 will outcompete and eradicate the strains that will survive Filter N+1.
There is also the larval metaphor in that a very unlikely series of events needs to occur to develop a strain that will survive a critical Filter. For example, there is conjecture that the contemporary strain of life on Earth began on Mars. Perhaps there was a strain that developed on Earth that could not have survived one of the past Filters while the Mars strain did.
Of course, it is also possible that some may act as reverse crucibles, in that they will kill off the strains of life that would have survived the next Filter.
Posted by: Rimfax at May 8, 2008 11:07:56 AM
Also, as a metaphor, consider cancer. Any one of the mutations that lead to a given cancer are not that uncommon, but you require several before you actually have a tumor - and then one or more after that for it to become metastatic.
Similarly, the potential intelligent life requires several steps to become intelligent (a tumor) and one or more after that to become metastatic.
Posted by: liberty at May 8, 2008 11:53:17 AM
The author seems to assume that we know much more about how other life would behave, especially intelligent life, and that we know our physical constraints (e.g. the final Theory of Everything, in some rough fashion). This kind of speculation is inherently limited by the unknown unknowns, it seems to me.
Why not instead assume that Earth is left as a nature park by various intelligent species, and that we can't see them because they live behind Dyson spheres or some such. Maybe all the dark matter in the universe is composed of suns and planetary systems trapped behind Dyson spheres, because there are so many intelligent beings out there. No need to worry about neutrino masses or other WIMPs if that's true.
It also shouldn't surprise us that sufficiently advanced beings aren't using radio waves to communicate. Lots of things can absorb or modify them on the interstellar level. Intelligent aliens may very well have the ability to communicate through the wrapped up, super small dimensions of string theory, or perhaps even by something that transmits outside our brane entirely, allowing instantaneous transmission across any distance (and effectively limited time travel).
This article assumes we would know and understand alien life if we saw it. But ants don't really understand cars or computers - they probably consider them part of the natural world if they consider them at all. We may be roughly analogous to a post Singularity set of intelligent, star-faring beings.
Posted by: Sisyphus at May 8, 2008 12:45:19 PM
even if we are worthy of notice now, we haven't been worthy of notice for long at all. if the universe is effectively infinite (a silly assumption because of the logical problems it causes), it may just be taking other intelligent life a while to get around even noticing us (why assume we're worthy of notice at this stage? we're not much beyond talking dogs), let alone deciding to say hello. (the assumption that we can tell whether there's something out there is absurd -- we've been in this game for what, 50 years?)
Posted by: dj superflat at May 8, 2008 12:53:35 PM
I have also found that people who believe (or find it interesting) in the existence of non-human intelligence "out-there" and people who believe that we will one day live in a simulation (or we are already living in one) tend to be the same people.
Moreover, people who believe in these speculations seem to be quite rational. Or claim to be.
Why this co-ocurrence of uber-rationality/belief in alien life/belief in the world as a simulation? Another question: why is this "condition" more prevalent in men than in women?
Tyler: I need answers! ;)
Posted by: londenio at May 8, 2008 1:15:47 PM
Blind Blake. You are conflating him with Blind Boy Fuller.
Posted by: ionides at May 8, 2008 2:26:51 PM
Of course the problem with the great filter being in the past is the doomsday argument. If the great filter is in the past, then, by definition, we can look forward to a long and prosperous future (millions of years). As Bostram says this implies billions and billions of future humans will exist. But then isn't it strange we should be part of the first few billion humans to exist in that case? The great filter in the past theory requires not only making our planet being special (the only one where life survived), but also our current time being special (the start of humanity), a bit too much to hope for don't you think? Isn't is much more likely that the great filter is in the future, then we are simply one of the multiple attempts to pass that failed?
Posted by: ChrisA at May 8, 2008 2:47:45 PM
Maybe the problem is that civilizations lose interest in space exploration before they overcome all the hurdles. After all, the assumption that there is a Great Filter is built on the notion that since humanity has explored much of the earth, all civilizations must want to explore space.
But Princeton astrophysist Richard Gott has a different idea, based on the Copernican Prinicple, which he explained recently:
"The Copernican answer to Enrico Fermi's famous question -- Where are the extraterrestrials? -- is that a significant fraction must be sitting on their home planets.''
It might seem hard to imagine that humans would invent rockets and then never use them to settle other worlds, but Dr. Gott notes that past civilizations, notably China, abandoned exploration. He also notes that humans have been going into space for only 46 years -- a worrisomely low number when using Copernican logic to forecast the human spaceflight program's longevity.
Since there's a 50 percent chance that we're already in the second half of the space program's total lifespan, Dr. Gott figures there is a 50 percent chance it will not last more than another 46 years. Maybe the reason civilizations don't get around to colonizing other planets is that there's a narrow window when they have the tools, population and will to do so, and the window usually closes on them. ''In 1970 everyone figured we'd have humans on Mars by now, but we haven't taken the opportunity,'' Dr. Gott says.
Posted by: SteveM at May 8, 2008 3:11:53 PM
1. Sufficiently advanced civilizations probably become utterly dependent on pervasive low-latency communications protocols, such that their members need to permanently remain within a fraction of a light-second's distance from one another. Think Facebook and mobile phones on steroids, or this-century future technologies like smart dust and augmented reality.
2. Sufficiently advanced civilizations probably have very high energy consumption needs, which (barring some new weird science) can only be satisfied by remaining in the immediate vicinity of a star. Much of this energy consumption is probably related to computing.
More speculatively (borrowing some ideas from Greg Egan's fiction):
3. If such a thing is in fact physically possible, sufficiently advanced civilizations probably upload themselves into non-organic media ("become AI") and thereby cease to live in the physical universe, but rather live within virtual worlds of their own devising. Much like it is easier to make movies using CGI to paint pixels onto a frame of film rather than than building a large physical model and filming it with a camera, it will become far easier to "paint" nerve endings with sensations rather than to build a physical world out of atoms and live in it.
4. Uploaded beings will probably live accelerated lives: they will have a much higher clock speed, because electronic or photonic devices run much faster than the chemical reactions that power an organic brain.
Accelerated beings will probably have little desire to wander the physical universe, because a few months' journey to Mars will become the subjective equivalent of several million years. In fact, they will have a far sharper dependence on low-latency communication protocols: due to speed-of-light issues, their entire civilizations may be constrained to exist within a sphere of a few hundred meters in radius or less. Their civilizations may also have short life spans: an epic rise and fall of many millennia of subjective time may take place within a few days of real time.
Although life starts out in organic form, perhaps sufficiently intelligent life inevitably bootstraps itself into some entirely different form. We might be like a fetus floating alone inside a womb and wondering, where is everybody?
Posted by: at May 8, 2008 3:15:40 PM
PS,
Even if we constrained our hypothesizing about advanced life forms to those that would continue to live at normal clock speed within our physical universe (non-accelerated, non-uploaded), they might still take forms that we cannot detect or recongize.
A sufficiently advanced living being might not necessarily be in compact, contiguous organic form: it could transform itself into a "steganographic" life form consisting of a network of diffuse nodes, communicating among themselves using encrypted spread-spectrum communications indistinguishable from background noise, with redundancy and error correction to ensure its integrity and survival. Such beings could conceivably exist on Earth or within the solar system right now, undetected. However, this scenario seems rather less likely than the "exodus from the slow physical universe" scenario.
Posted by: at May 8, 2008 3:18:26 PM
If you read Hanson's paper there is no suggestion that only *one* step along the path to life is drastically improbable:
The Great Silence implies that one or more of these steps are very improbable
[...]
To these roughly nine biological hard steps we might add two other discrete (random but not trial and error) type steps: an initial step of getting the right sort of planet around the right sort of star, and a final step of humanity either succeeding or destroying itself soon. Together, these eleven steps could explain the Great Filter [...] Of course the Great Filter need not be distributed evenly among these steps - just how much of the filter rests in the last step is the ominous question that motivates our analysis.
Posted by: Elisa at May 8, 2008 3:34:51 PM
What ethical principals do you assume these would come up with? My inclination is to see life as common, intelligence rare, and other intelligence as a source of fascination, perhaps suitable to enhancing progress for discovery and exploratory purposes. A universe less alone as a result, but one to keep tabs on in case they exceed your own.
Posted by: Lord at May 8, 2008 6:20:58 PM
Is it possible that intelligence is not a survival trait that lets us capture more prey, but a sexually selected feature like the peacock's tail?
The dinosaurs did not evolve intelligence sufficient for technology, despite being a successful class for a loooong time.
-dk
Posted by: Dick King at May 8, 2008 8:31:41 PM
I can't see what theism has to do with Fermi at all. Maybe I'm blind.
No name at 3:15: Even if all those points are true, if a civilization cared at all about the far future, it would want to send out probes to, if nothing else, gather negentropy that would otherwise have been uselessly dumped into space (by turning off the stars, building Dyson spheres and storing antimatter, or something else).
Sisyphus: Maybe all the dark matter in the universe is composed of suns and planetary systems trapped behind Dyson spheres, because there are so many intelligent beings out there. No need to worry about neutrino masses or other WIMPs if that's true.
Then why would so many stars be left un-sphered? Anyway, there's observed evidence for non-baryonic dark matter.
Posted by: Nick Tarleton at May 8, 2008 8:48:39 PM
I should have taken the blue pill...
Posted by: Neo at May 9, 2008 1:50:33 AM
The "Great Silence" is taken to be evidence for lack of intelligent life because, so goes the argument, even if nearly all advanced civilizations were non-expansionist, it would only take one to "break the silence". However, we can't discount the likelihood that there is some transformation that all advanced civilizations go through which causes them to be silent. Not most or nearly all, but literally all.
Consider that about 10,000 years ago, all living humans were hunter-gatherers. Today, very few are, and in a few decades the only ones left will be in quarantined preserves like North Sentinel Island, cut off from all contact with the rest of humanity. Today, you are only a hunter-gatherer if every single one of your ancestors was. When people make the transition to agriculture and technology, they don't go back.
Consider the billion or so people living in the "First World" (US + Canada, Europe, Japan, Australia, etc). Not a single one of them would adopt a hunter-gatherer lifestyle. Even the most notorious Luddite of modern times, the Unabomber, lived in his log cabin at a level of technology and comfort higher than that enjoyed by the original European settlers of the American plains; even he chose to go back in time less than 150 years, not 10,000 years.
Likewise, even if there were a billion civilizations in our galaxy (a far too high estimate by many orders of magnitude), it is certainly possible that not a single one would continue the non-silent, expansionist way of life of their distant ancestors. We might not be able to fathom the reasons why, any more than hunter-gatherers can fathom civilization except through the distorted lens of cargo-cult mysticism, but that doesn't mean we can rule out such a possibility. And if any obstreperous one-in-a-billion would-be expansionists even existed, well then, much like some would-be hunter-gatherer dropout from civilization moving into a national park game preserve, they might be politely told by the neighbors to desist.
Why haven't all the stars in the galaxy been turned into Dyson spheres? I don't know... why hasn't every square inch of dry land on Earth been turned into farms? We simply can't fathom the purposes and motivations of truly advanced, possibly post-Singularity civilizations.
The "Great Silence" is evidence of... silence, not evidence of absence.
Posted by: at May 9, 2008 4:40:55 AM
On the other hand, Patrick Moore did point if we did encounter an alien species with interstellar capabilities then they should be relatively peaceful because the technology and energy required for interstellar travel are such that they could easily be converted into super-destructive weapons and the species would have snuffed themselves out long ago. After all, how long would the Earth last if terrorists nutcases got their hands on the ability to make anti-matter bombs?
Posted by: Gil at May 9, 2008 8:52:53 AM
People ignore the most simple solution to the Fermi paradox. Maybe the distances involved are too great.
The most powerful radio signals ever made on our planet are only about 1% louder than background noise by the time they reach the nearest star. Just twelve stars away, an advanced civilization could be transmitting a million watt radio signal in all directions, and from here is is one millionth as loud as the radio signal from my wireless mouse.
There could be a million planets in our universe right now communicating as loudly as they possibly can, and our most sensative radio telescopes would never be able to pick one out from the typical background noise of the universe.
As far as actually traveling the distance, the answer is similarly obvious. Maybe the trip is impossible. Ever wonder why there are no polar bears at the South pole?
Posted by: Dave at May 9, 2008 1:51:09 PM
"seeing us"
"seeing them"
the same thing?
...
Sweet Caroline
wah wah wah
Hume or Diamond?
Posted by: oops at May 9, 2008 2:33:13 PM
Why haven't all the stars in the galaxy been turned into Dyson spheres?
It's not that *all* have not been, it's that *none*, at lest in our immediate galactic neighborhood, have been.
Posted by: nick at May 9, 2008 8:54:35 PM
