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FQXi FORUM
CATEGORY: Complexity
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TOPIC: The Fermi Paradox
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I'd be interested in hearing any proposed solutions to the Fermi Paradox. My experience has been that this is one of the Foundational Questions on which everyone you meet at a party has a ready answer, but the paradox turns out to be surprisingly resilient.
The general question runs like this: Our contemporary understanding of stellar evolution, planetary formation, biological evolution, and the like -- coupled with a time-tested respect for the Principle of Homogeneity -- suggests that, as intelligent, conscious, technological civilization has evolved on Earth, it should also have done so on other planets (at least) by now. In fact, it should have done so a huge number of times, even billions of years ago. So where are they?
The thing I like about the paradox is it tends to toss us between its horns. The quick, "realist" answer -- often delivered with a smirk -- is that there aren't any aliens. (Every serious person knows that.) But, take that route, and you wind up impaled on one horn: why not? Which part of our contemporary understanding of nature is so far off the mark?
It can't just be a matter of dismissing tales of alien abduction and the like; credible science, as it stands in 2007, has a hard time imagining how one planet could be absolutely unique in this respect. And astronomical data on other planetary systems keeps making it more of a stretch.
To the other horn, then. The equally popular response is that thinking we are alone in the galaxy is just plain hubris; aliens are a given. (Every open-minded person admits that.) But that lands us back at the initial question: so where are they? Is it really plausible that the Milky Way is teeming with advanced technological civilizations, as some reasonably sensible predictions say it should be -- and yet no observations to date have produced credible "footprints" of any of them?
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What do you mean by "credible 'footprints'"?
E.T. is unlikely to land his space ship just south of the White House... unless there is actually a danger of experiments involving collisions of heavy nuclei causing a black hole.
Even space travelers not limited by a Star Trek like non-interference directive would probably not want to contact a planet whose inhabitants have so much trouble getting along with each other and like "War of the Worlds" type movies.
Lawyers sometimes use the question "Is the evidence consistent with an hypothesis that..."
We don't have definite evidence of contact with space travelers, but we do have the type of evidence which would be "consistent" with a visit by them. Accounts of alien abductions may be dreams, etc., but they are consistent with the method E.T. scientists might use to directly study human "specimens" without making formal contact with a planet. Scientists would seek persons who could be taken to the lab without attracting attention and would use some type of drugs, hypnosis, etc. to limit the "specimen's" memory of the analysis. Such scientists would also attempt to avoid specimens who whose claims of abduction would be accepted.
the U.S. military has aircraft that are invisible to radar and is experimenting with technolgy to limit visual detection of troops or equipment. Interstellar travelers might possess some type of "cloaking" technology.
I'm not a disciple of Erich van Daniken, but he does have a valid point that histories of many peoples contain stories that could refer to contact with interstellar travelers. On the other hand the accounts may come from the imagination of an ancient Jules Verne or George Lucas. The accuracy of accounts of contact with E.T. would be limited by the experience and language of those providing the account. Keep in mind that residents of Mexico originally thought the Spanish might be gods and a horse and rider was the same animal.
The account most likely to indicate actual contact with space travelers comes from the Dogon people of West AFrica. They had knowledge of both Sirius A and Sirius B 5,000 years before earth had the technology to detect Sirius B.
http://www.crystalinks.com/sirius.html
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My favorite solution is as follows. At a certain point, civilizations consisting of biological being replace themselves by machines. I conjecture that this replacement stage happens around the time that civilizations start to xplore space. The reason for that is that it is much easier to explore space with machines.
If we wanted to build a base on the Moon or on Mars, it may well be worthwile to invest tens of billions of dollars to develop more intelligent machines. If they can do some simple tasks so that the first few phases of construction could be done entirely without sending people, we could save an enormous amount of money.
The same machines would be useless on Earth as no one would buy a machine that costs $10 billion just to do some simple construction work. But when we start to invest heavily in artificial intelligence technology we'll soon get to a point when machines become more intelligent that humans. Humans will then go extinct, because they become redundant obslete technology. If we are lucky the robots may keep some of out great great grand children in Zoos or as pets.
So, we should expect that advanced civilizations that are capable of interstellar space travel consist entirely of machines. Thgis means that there are a few more possibilities to resolve the Fermi Pardox:
1) Most machine civilizations are not interested in space travel
2) Machine civilizations are inherently unstable and self destruct.
3) Machine civilizations tend to degenerate from a high intelligence active state to a low intelligence passive state.
Some arguments for the above points:
1) It could be that the universe itself is a mathematical model (physical existence = mathamatical existence, as e.g. recently proposed by Tegmark). Then computer simulations in which you create some artificial reality to study something is to be preferred to just looking in the vast universe to find that thing.
2) Suppose that you are computer program. Then you want to have as much run time as possible, but so will everyone else. This then may lead to conflicts. Robots will fight each other and the whole civilization could go up in smoke.
3) Suppose that instead of the war predicted in 2) you get a form of peaceful coexistence or perhaps you end up with one intelligence claiming all of the CPU resources. The difference between machines and biological beings is that the former have a much larger degree of control over themselves. They can upload themselves to different machines etc. This freedom could be destructive in the same wy as drug addiction, obesity caused by overeating, plague our societies. If you are a robot you could taste delicicous food all they long, you can have sex all day long simply by uploading your program into the appropriate simulation machines.
So, you may get a civilization that uses a lot of energy just to mantain simulations of activities that we like to do. This then leads to the civilization becoming degenerated...
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It's a cool possibility--that biological civilization tends toward technological civilization (as it probably does) and that technological civilization might prefer to spend its time in virtual worlds, perhaps using them to study RW without touching it. (Check out "Out of Plato's Cave?" for a burgeoning instance of this in our own world--the Second Life Island.) I'd like to think this would be motivated by an ultimate form of environmentalism; a kind of Prime Directive applied to all of nature.
Something similar, actually, is posited in mathematician and hard SF writer Greg Egan’s book “Diaspora”; biological civilization tends toward a state he called “the Introdus,” in which minds are uploaded into a transmissible cyber format, the physical remains of civilization (and of organisms) becoming increasingly irrelevant as consciousness hops about from one technological carrier to another. I highly recommend his work, by the way, to anyone interested in conceptually-driven speculative science: it’s a lot like reading Daniel Dennett’s philosophical thought experiments, only in a sci-fi format.
Still, while such a scenario is conceivable, there’s no particular reason to think it’s happening. But even if it is—here’s the other horn of the paradox—it can’t realistically be happening to every technological civilization. Some of them must be in a state midway between biology and technology, or be massively technological but not yet fully incorporated into their VR, or have evolved in entirely different ways, for which trading exploration for VR would be unthinkable; and so on.
Sagan thought a conservative application of the Drake Equation yielded as many as one million (!) high-tech civilizations in the Milky Way alone. The numbers are just too high for them all to have fallen prey to the same evidence-erasing process . . . aren’t they?
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Let us consider some concepts related to Max Tegmark's "level 4 multiverse" concept, where all possible mathematical or computational structures exist, and those with appropriate complexity and structure can be thought of as universes. Of course this is not widely accepted but as an exercise, let us pursue what it says about the Fermi paradox. It leads to a curious connection between this paradox and the oft-noded property that our universe is seemingly fine-tuned for life.
Let's also take the evidence at face value: we see no aliens because there are no aliens. In the entire visible universe there is only one planet with intelligent life, our own. What does multiverse theory say about this odd fact?
If all possible universes exist then there will exist universes that are dense with intelligent life as well as ones like our own that are extremely sparse. Observers will exist who see both kinds of universes. At first it might be thought that since observers are far more numerous in life-dense universes, most will be of that kind, so our observations of sparseness are even harder to explain. It might even be considered to invalidate multiverse theory.
Of course if you think that, you ignore human ingenuity at rescuing failed theories. Instead, we will invoke a manifestation of Occam's Razor and say that certain universes are inherently of larger "measure" in the universe, namely those of simpler structure, which take less information to describe. We will leave the notion of measure vague except to say that all else equal, universes of higher measure are more likely to be experienced.
Now we have a hope of explaining the Fermi paradox, or at least characterizing it in multiverse terms. It must be that universes which are very sparse in life have significantly higher measure than those which are dense. Sparse universes must have simpler laws of physics and/or initial conditions, so that they can be described with less information than life-dense ones.
If we consider all possible universes and rank them by complexity, it seems plausible that extremely simple universes are not suitable candidates for intelligent life. We need a certain threshold of complexity and variety for life to form and evolve intelligence. As we move up the scale, we would first hit universes which allow life, but just barely. They would not be particularly hospitable to life and while it might form and even thrive to a limited degree, it would be extremely rare. And finally we would reach universes of substantial complexity and richness, some of which might be very good homes to life, where life and intelligence flourishes and is widespread and common.
This gives us the germ of an explanation, then: simpler universes would be of higher measure, and it is likely that the simplest universes which nevertheless allow life to form would just barely allow it to happen, so life would be sparse in such universes. However, it is not a full explanation because it leaves open the question of what increment of life-density is gained by adding a delta of universe-complexity. If going to a universe that is 1% more complex makes life 100% more common, our explanation fails, as we would then expect to see most life in dense universes, even taking measure into consideration. So in this context, the Fermi paradox can be understood as a prediction about the nature of certain mathematical systems, and of how complexity facilitates the formation of subsystems analogous to what we would call intelligent life.
As far as the connection to the fine tuning, it would go as follows. Go back to the ranking of universes by complexity, and focus on the ones that are just barely complex enough for life to form. As we noted, in such universes life would be rare. Its presence might well be a function of initial conditions, such that only certain special values would allow life. And among those conditions we might consider the various magic parameters which have been found to be fine-tuned to be beneficial. Universes with relatively simple laws which just barely support life, but where nevertheless life has attained a toe-hold, would commonly offer such seeming coincidences of various parameters and initial values that conspire to allow life to exist. This would then correspond to our observations.
Summing up, the level 4 multiverse concept, augmented with a notion of measure corresponding to complexity of physical laws, ties together the Fermi paradox and the fine-tuning. Both are seen as manifestations of the higher measure of uinverses which are just barely complex enough to allow intelligent life to form.
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Let me just add a more concise way of thinking of the connection between the Fermi paradox and the fine tuning. Fermi shows us the sparseness of life (at least, intelligent life) in physical space; the fine tuning demonstrates the sparseness in parameter space. The idea is that the sparseness in parameter space predicts the sparseness in physical space, because if you have to fine-tune parameters to get life at all in our little "island" of parameter space, it makes sense that life would just barely exist there.
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Great points, Hal—and of course we all bow before the mighty Amtrak Keg Mixer.
Even if a sparsely populated parameter space does correspond to a sparsely populated physical space, though, aren’t we still left trying to make an implausible claim—that the actual universe we live in is one of those sparsely populated ones? It seems to me that fine-tuning arguments at best may persuade us that sparsely populated universes (let’s call them SPU’s) are possible; they may even make a persuasive case that SPU’s are common. But we’d still left on one horn of the paradox: based on what we see around us, our universe really should not be one of those universes.
For example, the evidence of our own existence (one planet, one technological species), the mounting evidence of a trend toward tool-use in other species (now including birds), the existence of complex biological life in every niche on the planet (including various extremophiles), the evidence of Earth-like planets around other stars, and so forth . . . none of this suggests that we are living in a SPU. It seems to me we’d need some mechanistic explanation as to why life is so absurdly fecund here, why it popped up with evident ease as soon as the bombardment period ended, why evolution led in relatively short order to a space-faring, high-tech civilization once . . . and not on literally billions of other planets with roughly the same timescales and conditions. Even if SPU’s exist and are common, would this kind of data be found in one of them?
Reason McLuhan’s question of what constitutes a “credible footprint” for an alien civilization strikes me as a good one. The tradition of the Dogon makes for an interesting sidebar, but it’s ultimately not compelling; we want something that would pass a double-blind test, something as solid as the Mars meteorite ALH84001, had it panned out. It really should be there. (No sentient species on Mars would be uncertain as to whether Spirit and Opportunity constitute evidence of extraterrestrial life.) Shouldn’t it?
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It seems likely now that the evidence for other "earths" will eventually be overwhelming; and, so, it also seems likely that life is everywhere. That suggests to me that the resolution of the paradox is that we aren't searching correctly.
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We should consider the possibility of life radically different from that we see around us on earth.
http://www.bigear.org/vol1no2/life.htm
This paper points to a much larger definition of life and a much more expansive set of potential venues.
There are a lot of inherent assumptions in the paradox about how life might evolve which may or may not be true and lead to the assumption that other living entities could/would travel beyond their environment. You could look at our planet today and make an effective argument that until we solve all the problems here on earth we should not be investing in extraterrestrial endeavors as well.
Regards,
Elliot
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From our current knowledge of evolution on this Planet - it seems to be a reasonable assumption that life will spring up where ever it can - whenever the conditions are right. One of the tricky parts of the Drake equation in respect of real number plugging is the likelihood of 'intelligent' life arising.
I'm pulling numbers off the top of my head here - but they are relatively accurate to illustrate my point. The dinosaurs were around for 150+ million years, and if my rusty memory on the last paeleontological tv program I saw serves me - there was another epoch of creatures around for 100 million years before them. In comparison the mammal line has taken 65 million years to produce us.
This suggests to me that there is not a necessarily a natural attractor for intelligent life to always evolve otherwise surely the dinosaurs would have done it in the time they had.
We arose from conditions that took at least 2 major extinction events to generate - but why not a thousand..?
When we finally get powerful space telescope arrays in place - at conservative estimate it is likely that the first 1,000 planets we discover to contain life - will not actually contain native intelligent life. (I say 'native' here - because if we are subject to a 'prime directive' and there are plenty of space fairing aliens - it is likely that they will have colonised at least some of them.)
This could potentially give us quite a large playground to expand into - but I digress.
It may be that the physics of really long distance interstellar travel in one go - are just not there - or have not been discovered by even the most advanced aliens. The result being that it may only be feasible to travel to the nearest inhabitable solar system - set up shop there - before being ready to move on to the next viable solar system. Thereby an advanced race would only be able to progress relatively slowly in its quest to explore/colonise a Galaxy.
If there are various civilisations out there capable of pan galactic travel - I like to think we would be protected by a 'prime directive'. It's not unreasonable to assume that they would have had to undergo the same trials & tribulations as we are undergoing in our quest to reach out to the stars. They certainly would have to match us or better in interpersonal collaboration, communication and creativity to bring the math, science & technology to a level that would be required. Assuming there is enough resources out there to satisfy their needs - why bother with us. To them we are adolescents - and they are just waiting for us to mature to the right age before letting us in the club.
If there are millions of advanced races in one big Galactic Club (Federation?) maybe they are using cloaking technology to hide the regions of the Galaxy they inhabit. That would explain dark matter...
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I'm not a scientist but I am a big fan of this site. Keep up the quality!
Maybe the answer is "patience". We're only looking for a few decades. We're up to 322 knows exo-planets according to NASA's Planet Quest. At best, we've seen an exo-planet as a pixel (and even that wasn't 100% certain).
Imagine Europeans in the Middle Ages speculating if there was "life" across the sea. Why didn't they contact them? The answer then was that the inhabitants of the New World didn't have the technology to ring them up (nor did the Europeans!).
It doesn't look like we're about to be able to visit other star systems, so we hope to find "E.T." somewhere on the spectrum.
I still think it can happen. Were we to make contact tomorrow - or even in the next 50 years, history will record that we "found them" pretty darn fast.
The answer is to keep doing "all of the above" - the SETI Project, searching and studying exo-planets, NASA and European efforts and everything else.
A bit of patience - the toughest answer.
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I believe the answer may lie in alternative, computer based simulations (read: Matrix type thingy). It would be far cheaper and pragmatic to create a reliable machine based other-world to explore the cosmos, as opposed to zipping around the universe like Zaphod Beeblebrox.
Aliens, in any form intelligent enough to begin detailed exploration of the universe very likely realize this themselves.
http://michaelgr.com/2008/05/09/virtual-reality-could-explain-the-fermi-paradox/
http://www.jrmooneyham.com/ctctc.html#section7
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The solution to the paradox is easy. One horn can be immediately elliminated. The chances that alien life eleswhere in the universe does not exist are negligable. We are almost certainly 'not alone'.
The reason we have not seen any positive 'signs' of intelligent alien life forms is almost certainly due to the vast size of the universe. Even if our local neighbourhood, the Milky Way Galaxy, had dozens of Earth like planets supporting humanoid life forms that are at least as technologically advanced as us, we would be unlikely to detect them.
Witness out attempts at space exploration. If we use a scale where the Earth represents the Galaxy, then we have not yet stepped outside our own backyard in our space exploration. How many thousands of years will it be before a human will actually be able to travel to within an Earth orbit distance of our nearest star? Even for an alien civilization that is significantly more advanced than ours, the distances are formidable and searching even the local galaxy will be a very difficult task.
You might think that maybe alien races will develope time travel technology that will overcome the distance problem. The indications are that time travel will never be discovered. For if some civilisation, even billions of years in our future, anywhere in the universe, discovers the secret of time travel, then they will use that technology, to dominate all space and all time to expand their species and use all resources to their advantage. The fact that we are not already enslaved by some advanced alien lifeform as a resource, indicates that time travel will never be discovered anywhere in the universe at anytime in the future. I am of course assuming that any alien species will have the tendancy of all currently known life forms to replicate their own kind at the expense of everything else and take all available resources.
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