I'm surprised how often the Drake Equation is still mentioned when people discuss such things as the search for extra terrestrial intelligence (SETI), astrobiology and problems like the Fermi Paradox.
Fairly recent insights in such fields as cosmology, astrobiology and various future studies have changed our perception of the cosmos and the ways in which advanced life might develop.
Frank Drake's equation, which he developed back in 1961, leaves much to be desired in terms of what it's supposed to tell us about both the nature and predominance of extraterrestrial life in our Galaxy.
The Drake Equation
The Drake equation states that:
where:N is the number of civilizations in our galaxy with which we might hope to be able to communicate and:
R* is the average rate of star formation in our galaxyArbitrary at best
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 go on to develop life at some point
fi is the fraction of the above that actually go on to 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 integers that are plugged into this equation are often subject to wide interpretation and can differ significantly from scientist to scientist. Even the slightest change can result in vastly different answers. Part of the problem is that our understanding of cosmology and astrobiology is rapidly changing and there is often very little consensus among specialists as to what the variables might be.
Consequently, the Drake formula relies on 'stabs in the dark.' This makes it highly imprecise and unscientific. The margin of error is far beyond what should be considered acceptable or meaningful.
No accounting for cosmological development or time
Another major problem of the Drake Equation is that it does not account for two rather important variables: cosmological developmental phases and time (see Cirkovic, "The Temporal Aspect of the Drake Equation and SETI").
More specifically, it does not take into consideration such factors as the age of the Galaxy, the time at which intelligence first emerged, or the presence of physiochemical variables necessary for the presence of life (such as metallicity required to form planets). The equation assumes a sort of cosmological uniformity rather than a dynamic and ever changing universe.
For example, the equation asks us to guess the number of Earth-like planets, but it does not ask us when there were Earth-like planets. And intelligence itself may have been present as long as 2 to 4.5 billion years ago.
The Galaxy's extreme age and the potential for intelligence to have emerged at disparate points in time leaves an absurdly narrow window for detecting radio signals. The distances and time-scales in question are mind-boggingly vast. SETI, under its current model, is conducting an incredibly futile search.
Detecting ETI's
Which leads to the next problem, that of quantifying the number of radio emitting civilizations. I'm sure that back in the 1960's it made a lot of sense to think of radio capability as a fairly advanced and ubiquitous means of communication, and by consequence, an excellent way to detect the presence and frequency of extraterrestrial civilizations.
But time has proven this assumption wrong. Our radio window is quickly closing and it will only be a matter of time before Earth stops transmitting these types of signals -- at least unintentionally (active SETI is a proactive attempt to contact ETI's with radio signals).
Due to this revelation, the entire equation as a means to both classify and quantify certain types of civilizations becomes quite meaningless and arbitrary. At best, it's a way of searching for a very narrow class of civilizations under very specific and constrained conditions.
Rather, SETI should continue to redefine the ways in which ETI's could be detected. They should try to predict future means of communication (like quantum communication schemes) and ways to identify these signals. They should also look for artificial objects such as megascale engineering and artificial calling cards (see Arnold, "Transit Lightcurve Signatures of Artificial Objects").
The future of advanced intelligence
Although possibly outside the auspices of this discussion, the Drake Equation does not account for the presence of post-radio capable civilizations, particularly post-Singularity machine intelligences. This is a problem because of what these types of civilizations might be capable of.
The equation is used to determine the number of radio capable civilizations as they conduct their business on their home planet. Again, this is a vary narrow view of ETI's and the space of all possible advanced civilizational types. Moreover, it does not account for any migratory tendency that advanced civs may have.
The Drake Equation does not tell us about exponential civilizational growth on account of Von Neumann probe disbursement. It does not tell us where advanced ETI's may be dwelling or what they're up to (e.g. Are they outside the Galaxy? Do they live inside Jupiter Brains? Do they phase shift outside of what we regard as habitable space? etc.). This is a serious shortcoming because the answers to these questions should help us determine not just where we should be looking, but they can also provide us with insight as to the makeup of advanced intelligence life and our own potential trajectory.
In other words, post-Singularity ETI's may represent the most common mode of existence for late-stage civilizations. And that's who we should be looking for rather than radio transmitting civs.
Are we alone?
Michael Crichton once put out a very weak argument against the Drake Equation. He claimed that SETI was a religious endeavor because it was a search for imaginary entities. He is wrong, of course; we should most certainly search for data where we think we might find it. I believe, despite the low odds, that it is reasonable to assume that our search for life on other planets is warranted. Even a negative result can be meaningful.
Consequently, SETI should keep listening, but expect to hear nothing. If we should suddenly hear something from the depths of space, then we will have to seriously re-evaluate our assumptions.
At the same time we should find better ways to detect advanced life and tweak the Drake Equation in such a way as to account for the missing variables and factors I mentioned earlier.
Again, and more generally, we should probably adopt the contact pessimist's frame. Back in the 60's and 70's, when the contact optimists like Sagan, Shklovskii and Drake ruled the Earth, it was not uncommon to think that N in the equation fell somewhere between 10x6 to 10x9.
These days, in the post Tipler and Hart era of astrosociobiology, cosmologists and astrobiologists have to take such factors into consideration as Von Neumann probes, the Fermi Paradox, the Rare Earth Hypothesis, stronger variants of the anthropic principle and catastrophism.
Put another way, as we continue to search for advanced ETI's, and as we come to discover the absurdity of our isolation here on Earth, we may have no choice but to accept the hypothesis that advanced life does not venture out into space for whatever reason (the most likely being self-destruction).
Our other option is to cross our fingers and hope that something radical and completely unpredictable lies on the other side of the technological Singularity.
This is an amazing post — well written enough for me (a layman speculator) to slog through it. And the link to your previous entry, "When did Intelligent Life First Emerge," was equally informative.
ReplyDeleteI seem to recall Kurzweil writing about an as-yet-unconfirmable principle similar to the Second Law of Thermodynamics in which built-in barriers prevent ANY intelligent civ from achieving Singularity. That would be even more depressing than Fermi's Paradox. Can anyone confirm?
The idea of post-Singularity civs doing dimensional engineering could be the theoretical loophole to Fermi's. Unfortunately, like M-theory, it seems entirely speculative.
Even when I was a boy, first encountering the Drake Equation in...I believe it was Sagan's Cosmos (the illustrated book, not the film series, which I finally saw years later), I thought the equation was complete bullshit. At best it could never do more than cough up an INCREDIBLY rough estimate of the number of civilizations which become either spacefaring or actively interested in long-distance radio contact. And really...how likely is that?
ReplyDeleteI tend to agree with Charles Stross'/Michael Anissimov's idea that post-Singular civilizations do not travel due to bandwidth restrictions inherent in the speed of light. After all, once one has established a perfectly good computronium base to support a stable ultra-high-speed civilization of uploads/digital intelligence, what is the point of wasting matter which could be put to better use in Matrioshka brains, etc., by building space probes or even Von Neumann devices? What need would an Accelerated civilization have for "colonizing" nearby stars? Chances are, due to the VAST amount of perceptual time elapsed between the departure a VN seed device from Sol and it's arrival at, say, Tau Ceti, the "seed civilization" would be hopelessly out-of-date...untold billions of upgrades/versions behind the parent. What would be the point of the Solar parent civilization in contacting them? It would be like phoning back in time to talk to your Neanderthal ancestors.
If a post-Singular civilization has any interest in space, it can easily build massive telescopes to study the Galaxy/Universe around it without having to leave home. After all, we Human 1.0s have never left Earth, and even with our comparatively small optics and other EM-spectrum devices we've managed to observe (and deduce therefrom) a LOT. No doubt a post-Singular civilization would do the same.
The ONLY reasons I can see for a post-Singular civ launching an interstellar effort would be to 1) find a new star to help power them now that their original star is running out of steam; or 2) make a "backup" in case of disaster. But again, chances are a post-Singular civilization will never be 100% dependent on solar radiation to power themselves, and even if they initially are, it's a safe bet they'll sooner or later develop some newer and, probably, better means of powering themselves (sucking energy right out of the false vacuum, for instance).
Nonetheless, it's also strange to think of advanced digital civilizations having any interest whatsoever in contact organics or even other digital civilizations. Why? Because signal lag between two widely-separated stars makes "communication" impossible in all but the most rudimentary sense. We organic Humans find the task of communication over even as little as 20ly to be a daunting, unlikeable situations; imagine what a 20ly comm lag would be to a digital entity whose processor cycles a few million times per second?
Derek, you just blew my tiny mammal mind.
ReplyDeletethe drake equation was never intended to be mathematically accurate. Concieved during a time when the idea of believing in the possibility intelligent life elsewhere in the universe wasn't taken seriously, the drake equation served as a useful device for arguing that given the size and scale of the universe, the idea that life is unique to arth is unlikely.
ReplyDeletethanks for the post, George. Yes, of course DE is obsolete - Rob Bradbury and I tried to bring as many of the reasons in our New Ast. paper, and there are some more. However, the mainstream SETI community is unlikely to take these seriously enough at present. There is much of intellectual laziness and inertia there. And the things are not helped very much by many open-minded people who speculate too much on the rather nebulous alien sociology without previously learning all the necessary astrophysics and astrobiology, with some bits of evolutionary biology and comp. science... But we need to disseminate such ideas as widely as possible - so, thanks again for the good work.
ReplyDeletePerhaps advanced life has learned discretion.
ReplyDeleteGreat post, George, even if there's a few aspects where I disagree.
ReplyDeleteYou wrote, "The Galaxy's extreme age and the potential for intelligence to have emerged at disparate points in time leaves an absurdly narrow window for detecting radio signals."
This is a common criticism, and one I think is mistaken for a number of reasons. The kinds of signals SETI is searching for are intentional beacons meant to reach early technological societies. This is why SETI is focused on draining the so-called 'Water Hole', the relatively quiet slice of the electromagnetic spectrum between the radio spikes of H and HO. If there are other H20-based civilizations out there, the Water Hole is a reasonable and obvious place to exchange information.
In essence, we're checking the mailbox to see if someone's left us a letter -- a letter addressed to us using a specific radio frequency. The search for the letter has nothing to do with the technologies the sending civilization uses for their own communications. They would be using radio for our convenience, not theirs.
That said, the larger point you make is true. SETI orthodoxy has not honestly grappled with data received since the '60s. Sagan's dream of a chattering galactic civilization waiting for us to wake up and notice it is no longer credible. The shaggy dog stories the predominant SETI community has resorted to in order to avoid facing change may be impeding better work regarding ETI and a fuller understanding of our place in the universe.
One reason the Drake Equation has always seemed misguided to me is that a Bracewell-style program using von Neumann probes should provide us with ample evidence of ETI even if only one civilization in the universe achieves it. In my opinion, the lack of evidence of this sort is profoundly damning of the "optimistic" position. ETI may be extremely rare, or distant, or violatile, or all three. If so, we ought to be considering the possibility of initiating such a program for ourselves, before it's too late.
Nicely stated..
ReplyDeletewalt_williams@setv.org
Not directly related to Drake, but certainly of note concerning Fermi's and Von Neumann (from Wikipedia):
ReplyDelete"Another objection to the prevalence of Von Neumann probes is that civilizations of the type that could potentially create such devices may have inherently short lifetimes, and self-destruct before so advanced a stage is reached, through such events as biological or nuclear warfare, nanoterrorism, resource exhaustion, ecological catastrophe, pandemics due to antibiotic resistance, etcetera."
Which also speaks to that as-yet discovered physical law I brought up in an earlier comment...
Good post, I have to agree that the Drake Equation is obsolete. It really is kind of an intuitive thought dressed up in scientific terms.
ReplyDeleteThe galaxy is so big that its just impossible we are the only intelligent life, right? But the only real data we have is that life exists on one planet, certainly not enough data to base any serious statistical estimate on.
The 'real' odds of intelligent life developing may be so low that its quite normal for only one instance to exist in a galaxy.
http://www.space.com/adastra/070531_adastra_et_art.html
ReplyDeleteArt for E.T.'S Sake
By Stuart Atkinson
National Space Society
posted: 31 May 2007
06:18 am ET
For a long time there was an assumption in SETI circles that when Contact came it would be through the detection of an unambiguous radio signal, a clarion call from the depths of space that would be unmistakably alien. SETI scientists and enthusiasts alike maintained that an ET signal will be both simple and easy to identify as being extraterrestrial in nature. Now we realize it might not be that straightforward. ETs might be attempting communication via lasers, or holograms, or some other way we can't even imagine. We're looking for a needle in a haystack whilst wearing a blindfold and boxing gloves.
While the best case scenario would be for our first ET signal to be a Sputnik-like beeping from the depths of space, telling us how far we have to turn the galactic radio dial before we hear the clear tones of "Voice Of the Milky Way", it's more likely that the transmission will contain a LOT of information which will be hard to decode, especially if that information wasn't created and transmitted with the purpose of making contact, but 'leaked'. Earth leaks signals out into space all the time, and the radio ripples spreading away from us carry not only entertainment programs but documentary-style factual programs too. Wildlife documentaries, natural history features, gardening shows, cookery shows, sports events, all of them carrying a wealth of accurate information for any ETIs who stumble upon them.
Might alien civilizations be "leaking" too? If they are, then we should cross our fingers that there are ET equivalents of "National Geographic" specials heading towards us, packed with useful information, instead of their versions of "Big Brother". What a disaster that would be...
But what about programs concerning art? Art contains lots of confusing and conflicting signals. Art is subjective and very personal. And although many forms of art are self explanatory, realistic and easily interpreted, so-called modern art, with its geometrical patterns, chaotic curves, random patterns and psychedelic swirls and whorls of color, take some figuring out.
The odds against us stumbling across an ET episode of "Art Today" are ridiculously high, but not impossible. Perhaps a civilization might, after millennia spent refining its sciences, value art more highly, so highly they felt a desire to share their artistic achievements with the rest of the Galaxy, (and preserve them in the process too, of course). Such a civilization might broadcast the contents of their galleries, scattering them among the stars like confetti, distributing them like a cosmic form of "shareware"...
But one civilization's art could be mistaken by another for scientific images, graphical representations of scientific concepts, or illustrations from some advanced physics textbook, and vice versa. Would we recognize - and/or aesthetically appreciate - any incoming examples, whole or fragmented, of ET art? And it works both ways: what would an ETI make of Picasso's works, when only a very few of us here on Earth have a clue what they're meant to represent? And are we really sure that ETs will correctly interpret those pulsar maps on the sides of our Voyagers and Pioneers, or will they just think "Hmmm, interesting composition, but too abstract for me.."?
The nature of ET art will be dictated by their range of senses, their environment, their evolutionary path, psychology and physiology. Of course, they could create familiar-looking compositions and provide us with stunning landscapes and portraits of the living things they share their corner of the Galaxy with, but it's more likely that the art created by ETs might be so different to our own that it would be unrecognizable as art. What sort of art might a mechanical ET produce? Would they rejoice in perfect design, see beauty in purely functional forms and shapes, have only disdain for soft lines and subtle, soft colors?
Perhaps some ETs will be so advanced they might create art on a literally astronomical scale, manipulating astronomical objects or entire regions of space...
It seems to me that ETs centuries or even millennia ahead of us would have so much power and so much energy at their disposal that the lines between art and engineering would eventually become blurred. As their artists strove to produce bigger and better works, they would need increasingly larger "canvases" for their works. Think of the evolution of our own art. Once we painted on cave walls, then discovered canvases, and how to sculpt stone. We then moved on to illuminating the sides of buildings with lasers and carving faces in mountainsides. Where next? Laser sculptures in the sky? Sculptures in Earth orbit? Images projected onto the Moon?
Now put yourself in the shoes of an artist a thousand, ten thousand years ahead. What canvas is big enough for your ambitions and imagination...? How about deliberately crashing asteroids or comets into gas giants to create exotic and wonderful patterns in their clouds, to be enjoyed by millions watching the show from across your solar system..?
Perhaps alien artists are painting with the very light of the stars themselves. Look at those breathtaking pictures of planetary nebulae taken by the Hubble Space Telescope, with all their multi-colored, intricately-structured shells, veils and curtains of starfire swirling around them. By interfering with the stars lurking inside such a nebula, maybe by dumping material on their surfaces, alien artists might be able to change the density and "gusts" of the solar wind shaping it, and in so doing manipulate the shape of the nebula into patterns and forms of their choosing. Would advanced civilizations be able to create epic-scale light-and-gas sculptures in this way?
Think about it. How many times have you looked at a Hubble image and thought "That's a work of art..."?
Maybe you were right.
Two observations:
ReplyDeleteThere's no reason to assume that a post-Singularity civilisation should not also incluse a number of 'enthusiasts' willing to expend resources on self-replicating subsets of their civilisation.
And, on the biological front, the current 'Goldilocks' paradigm is simply wrong - even Earth isn't really within Sol's Habitable Zone.
Mike Judge's film "Idiocracy" is usually on late night because the adult language is dense. Nonetheless, it is worth seeing because the film uses humor to make a valid but politically-incorrect point about the rapid conversion of intelligence to a maladaptive trait. According to Judge, the coefficient L in Drake's equation is only about 1,100 years for Earth. A note added in proof to Cirkovic in Astrobiology 4, 225 (2004).
ReplyDeletethe drake equation was never intended to be mathematically accurate. Concieved during a time when the idea of believing in the possibility intelligent life elsewhere in the universe wasn't taken seriously, the drake equation served as a useful device for arguing that given the size and scale of the universe, the idea that life is unique to earth is unlikely.
ReplyDeleteI'd have to agree. Some people are taking DE too religiously. It was never meant to be pi people.
According to Judge, the coefficient L in Drake's equation is only about 1,100 years for Earth. A note added in proof to Cirkovic in Astrobiology 4, 225 (2004).
Can somebody please elaborate on that last line?
I believe that there is life elsewhere in the universe; if those organisms are intelligent, I don't know. I think the Drake Equation is flawed because it does not include all factors that affect the formation civilizations. In fact, we don't really know everything that could have an effect on the evolution of societies, or life itself, for that matter. For example, what about natural disasters? Or wars between alien species?
ReplyDeleteHi, All,
ReplyDeleteThe main problem with taking an infinite number, (the number of stars in the universe) and taking smaller and smaller partsd of it, is that any nuber derived is also infinite.
So the problem with Drakes is not how few extraterrestrial civilisations are there? but as there are an infinite number of them, how do we avoid falling over them all the time?
Derek, excellent write-up from a human 1.0 to a human 1.0 audience, it's logical, and acceptable. But I only wonder what a truly advanced civ might do, this is the part I'm having trouble with (ie. intrigued), I don't think we are in a position to deduce or induce the realm of possibilities.
ReplyDeleteLeonel
I think the most likely cause of post-singularity civilizations not being explorers is not self-destruction, but some form of omphaloskepsis or simply disinterest. Its likely that once a society understands all of physics and cosmology and biology that it finds such things unimportant for study. Just as most biologists are not interested in doing life-histories of every species on the planet (understanding the overarching principles being enough), a post-singularity civilization might not be interested in studying other intelligences. Singularitism suggests the elimination of culture, where societal motivations become so obvious to the overmind that free-will is irrelevant, courses of action and rules of behavior behave as mathematical constants rather than preferences. As such, such a society would have no interest in foreign relations.
ReplyDeleteas far as i can see the drake equation is seriously flawed, in my opinion the result should be divided by the age of universe - further the length of time that a civilization transmits might only be a couiple hundred years, and an advanced civilization will have squillions of toms of its ancestors hidden away as fuel, they will start to burn it not realizing the consequences
ReplyDelete