Gilese 581 discovered for the first time....again

I'm finding it very strange that everyone's all a tizzy about the discovery of a potentially habitable planet, Gilese 581. This planet was discovered over three years ago. I remember this because it was an important consideration in the Fermi talk I delivered in Chicago the same year. Its discovery also motivated me to write about the Rare Earth Delusion. I'm not sure I understand all the sudden attention.

** ADDENDUM: 2010.10.05: Okay, everything is now illuminated: As my reader Richard Leis, Jr. points out, "The discovery of Gliese 581 c was announced in 2007. Last week's announcement was Gliese 581 g. C was initially considered a good candidate for potential life, but later calculations suggested it was actually outside the star's habitable zone. G is considered a better candidate because calculations place it more firmly within the habitable zone." **

Well, whatever. What's important to note is that (1) it reaffirms the notion that we (likely) live in a biophilic Universe and (2) its presence deepens the disturbing nature of the Fermi Paradox. As a potential data point that works to increase the value of n in the Drake Equation, it serves to reinforce the suggestion that, while we find ourselves in a Universe that is likely teeming with life, it's not one that's teeming in space-faring civilizations. Consequently, its discovery is not exactly good news.

Here's what I wrote back in April of 2007 when Gilese 581 was first discovered:

Wow, the blogosphere has been absolutely gushing these past few days over the news that an Earth-like planet may have been discovered in the 'hood. This planet may boast a moderate climate that could conceivably support life and is only 20 light years away.

Not surprisingly, this news has caused a number of pundits to fantasize about jumping into their rocketships and bidding adiós to our polluted, war-torn and diseased planet.

But not so fast, amigos. While many have misguidedly jumped on the bandwagon to the stars, a number of bloggers have gotten it right.

In his article, "'Don't Pack Your Bags Just Yet", Jamais Cascio notes that, "By the time we have the technology that would make a 20 light year trip even remotely plausible (the fastest space craft yet made would still take thousands of years to get there), we probably won't be all that interested in living in a watery gravity hole anyway. Nope -- give us some nice, massive gas giants to convert to computronium!"

Michael Anissimov points out that we have a human hospitable planet right here that we’ve barely even begun to use. He also argues that "even if we did need to leave the Earth, there is a tremendous amount of raw materials for space colonies right next door in the form of carbonaceous asteroids, which make up about 75% of known asteroids." Moreover, warns Anissimov, "we should think carefully before sending off colonists to far-away places without ensuring that they’re capable of protecting the fundamental freedoms of their citizens." Specifically, he worries that a blight may come back to haunt us (which also reminds me of the Honored Matres of the Dune series).

And as Tyler Cowen noted, "Are earth-like planets so common? That probably means lots more civilization-supporting planets than I had expected. But where are the alien visitors? As suggested by the Fermi paradox, we must revise our priors along several margins, one of which is the expected duration of an intelligent civilization."

Indeed, Cowen is on the right track. A primary argument used to reconcile the Fermi Paradox is the Rare Earth Hypothesis. This line of reasoning suggests that we haven't been visited by ETI's because life is far too rare in the cosmos.

But if we have discovered an Earth-like planet as little as 20 light years away, it's not unreasonable to suggest that our Galaxy must be absolutely teeming with life. This would seem to be a heavy blow to the REH.

So why is this bad news? It's bad news because our biophilic universe should be saturated with advanced intelligence by now...but it's not. The Fermi Paradox is very much in effect as a profound and disturbing unsolved mystery in astrosociobiology, philosophy and futurism.

Are all civilizations doomed before getting to the Singularity? Or is there something else at work here?

SETI on the lookout for artificial intelligence

Slowly but surely, SETI is starting to get the picture: If we're going to find life out there—and that's a big if—it's probably not going to be biological. Writing in Acta Astronautica, SETI's Seth Shostak says that the odds likely favour detecting machine intelligences rather than "biological" life.

Yay to SETI for finally figuring this out; shame on SETI for taking so long to acknowledge this. Marvin Minsky has been telling them to do so since the Byurakan SETI conference in 1971.

John Elliott, a SETI research veteran based at Leeds Metropolitan University, UK, agrees. "...having now looked for signals for 50 years, SETI is going through a process of realising the way our technology is advancing is probably a good indicator of how other civilisations—if they're out there—would've progressed. Certainly what we're looking at out there is an evolutionary moving target."

Both Shostak and Elliott admit that finding and decoding any eventual message from thinking machines may prove more difficult than in the "biological" case, but the idea does provide new directions to look. Shostak believes that artificially intelligent alien life would be likely to migrate to places where both matter and energy—the only things he says would be of interest to the machines—would be in plentiful supply. That means the SETI hunt may need to focus its attentions near hot, young stars or even near the centres of galaxies.

Personally, I find that last claim to be a bit dubious. While I agree that matter and energy will be important to an advanced machine-based civilization, close proximity to the Galaxy's centre poses a new set of problems, including an increased chance of running into gamma ray bursters and black holes, not to mention the problem of heat—which for a supercomputing civilization will be extremely problematic.

Moreover, SETI still needs to acknowledge that the odds of finding ETIs is close to nil. Instead, Shostak and company are droning on about how we'll likely find traces in about 25 years or so. Such an acknowledgement isn't likely going to happen; making a concession like that would likely mean they'd lose funding and have to close up shop.

So their search continues...

Source.

Sam Vaknin: The Ten Errors of Science Fiction

Global Politician columnist Sam Vaknin argues in a recent article that science fiction is guilty of ten specific mistakes when postulating the characteristics of advanced extraterrestrial life. Specifically, he contends that sci-fi writers consistently buy into fallacies about:

1. Life in the universe

2. The concept of structure
3. Communication and interaction
4. Location
5. Separateness
6. Transportation
7. Will and intention
8. Intelligence
9. Artificial vs. natural
10. Leadership

While the article certainly raises some food for thought, Vaknin's call for writers to think more 'outside of the box' is a bit of a stretch, if not condescending. Science fiction writers, for the most part, take great pains to weave a coherent narrative around novel imaginings of what ETIs might look like. Moreover, Vaknin is himself guilty of considerably hand-waving, arguing that ETIs may be existentially and qualitatively of a different sort than what we might expect, but at the same time he doesn't provide any substantive or compelling evidence for us to believe otherwise.

Sure, I agree that ETIs may be dramatically different than what we can imagine and that they may exist outside of expected paradigms, but until our exoscience matures we should probably err on the side of the self-sampling assumption and figure that the ignition and evolution of life tends to follow a similar path to the one taken on Earth. Now, I'm not suggesting that we refrain from hypothesizing about radically different existence-states; I'm just saying that these sorts of extraordinary claims (like alternative intelligences spawning different quantum realities) require the requisite evidence. It's far too easy to fantasize about some kind of energy-based hive-mind living in the core of asteroids, it's another thing to prove that such a thing could come about through the laws of physics [my example, not Vaknin's].

In the article, Vaknin also posits six basic explanations to the Fermi Paradox (and the apparent failure of SETI) that are not mutually exclusive:

1. That Aliens do not exist
2. That the technology they use is far too advanced to be detected by us and, the flip side of this hypothesis, that the technology we use is insufficiently advanced to be noticed by them
3. That we are looking for extraterrestrials at the wrong places
4. That the Aliens are life forms so different to us that we fail to recognize them as sentient beings or to communicate with them
5. That Aliens are trying to communicate with us but constantly fail due to a variety of hindrances, some structural and some circumstantial
6. That they are avoiding us because of our misconduct (example: the alleged destruction of the environment) or because of our traits (for instance, our innate belligerence) or because of ethical considerations

Very quickly, point number one is possible but grossly improbable, points two to five are essentially the same argument—that we don't yet know where, how and what to look for, and point six violates the non-exclusivity principle (explains some but not all ETI behavior). It's odd that Vaknin selected these particular six arguments. There are many, many potential resolutions to the FP with these not being particularly stronger than any other (though point #1 has a lot of traction among the Rare Earthers.). And where is the Great Filter argument, which is possibly the strongest of them all?

Nice try, Vaknin, but the Great Silence problem is more complex than what you've laid out.

Nick Bostrom on the Fermi Paradox [video]

IEET Chair Nick Bostrom discusses the Great Silence with Robert Lawrence Kuhn on Closer to the Truth. Nick and I are totally on the same wavelength here, including our agreement over the suggestion that the discovery of life in the solar system would be bad news.

Five reasons why Stephen Hawking—and everyone else—is wrong about alien threats

Stephen Hawking is arguing that humanity may be putting itself in mortal peril by actively trying to contact aliens (an approach that is referred to as Active SETI). I’ve got five reasons why he is wrong.

Hawking has said that, “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans.”

He’s basically arguing that extraterrestrial intelligences (ETIs), once alerted to our presence, may swoop in and indiscriminately take what they need from us—and possibly destroy us in the process; David Brin paraphrased Hawking’s argument by saying, “All living creatures inherently use resources to the limits of their ability, inventing new aims, desires and ambitions to suit their next level of power. If they wanted to use our solar system, for some super project, our complaints would be like an ant colony protesting the laying of a parking lot.”

It’s best to keep quiet, goes the thinking, lest we attract any undesirable alien elements.

A number of others have since chimed in and offered their two cents, writers like Robin Hanson,Julian Savulescu, and Paul Davies, along with Brin and many more. But what amazes me is thateveryone is getting it wrong.

Here’s the deal, people:

1. If aliens wanted to find us, they would have done so already

First, the Fermi Paradox reminds us that the Galaxy could have been colonized many times over by now. We’re late for the show.

Second, let’s stop for a moment and think about the nature of a civilization that has the capacity for interstellar travel. We’re talking about a civ that has (1) survived a technological Singularity event, (2) is in the possession of molecular-assembling nanotechnology andradically advanced artificial intelligence, and (3) has made the transition from biological to digital substrate (space-faring civs will not be biological—and spare me your antiquated Ring World scenarios).

Now that I’ve painted this picture for you, and under the assumption that ETIs are proactively searching for potentially dangerous or exploitable civilizations, what could possibly prevent them from finding us? Assuming this is important to them, their communications and telescopic technologies would likely be off the scale.Bracewell probes would likely pepper the Galaxy. And Hubble bubble limitations aside, they could use various spectroscopic and other techniques to identify not just life bearing planets, but civilization bearing planets (i.e. looking for specific post-industrial chemical compounds in the atmosphere, such as elevated levels of carbon dioxide).

Moreover, whether we like it or not, we have been ‘shouting out to the cosmos’ for quite some time now. Ever since the first radio signal beamed its way out into space we have made our presence known to anyone caring to listen to us within a radius of about 80 light years.

The cat’s out of the bag, folks.

2. If ETIs wanted to destroy us, they would have done so by now

I’ve already written about this and I suggest you read my article, “If aliens wanted to they would have destroyed us by now.”

But I’ll give you one example. Keeping the extreme age of the Galaxy in mind, and knowing that every single solar system in the Galaxy could have been seeded many times over by now with various types of self-replicating probes, it’s not unreasonable to suggest that a civilization hell-bent on looking out for threats could have planted a dormant berserker probe in our solar system. Such a probe would be waiting to be activated by a radio signal, an indication that a potentially dangerous pre-Singularity intelligence now resides in the ‘hood.

In other words, we should have been destroyed the moment our first radio signal made its way through the solar system.

But because we’re still here, and because we’re on the verge of graduating to post-Singularity status, it’s highly unlikely that we’ll be destroyed by an ETI. Either that or they’re waiting to see what kind of post-Singularity type emerges from human civilization. They may still choose to snuff us out the moment they’re not satisfied with whatever it is they see.

Regardless, our communication efforts, whether active or passive, will have no bearing on the outcome.

3. If aliens wanted our solar system’s resources, they would haven taken them by now

Again, given that we’re talking about a space-faring post-Singularity intelligence, it’s ridiculous to suggest that we have anything of material value for a civilization of this type. They only thing I can think of is the entire planet itself which they could convert into computronium (Jupiter brain)—but even that’s a stretch; we’re just a speck of dust.

If anything, they may want to tap into our sun’s energy output (e.g., they could build a Dyson Sphere or Matrioshka brain) or convert our gas giants into massive supercomputers.

It’s important to keep in mind that the only resource a post-Singularity machine intelligence could possibly want is one that furthers their ability to perform megascale levels of computation.

And it’s worth noting that, once again, our efforts to make contact will have no influence on this scenario. If they want our stuff they’ll just take it.

4. Human civilization has absolutely nothing to offer a post-Singularity intelligence

But what if it’s not our resources they want? Perhaps we have something of a technological or cultural nature that’s appealing.

Well, what could that possibly be? Hmm, think, think think….

What would a civilization that can crunch 10^42 operations per second want from us wily and resourceful humans….

Hmm, I’m thinking it’s iPads? Yeah, iPads. That must be it. Or possibly yogurt.

5. Extrapolating biological tendencies to a post-Singularity intelligence is asinine

There’s another argument out there that suggests we can’t know the behavior or motivational tendencies of ETI’s, therefore we need to tread very carefully. Fair enough. But where this argument goes too far is in the suggestion that advanced civs act in accordance to their biological ancestry.

For examples, humans may actually be nice relative to other civs who, instead of evolving from benign apes, evolved from nasty insects or predatory lizards.

I’m astounded by this argument. Developmental trends in human history have not been driven by atavistic psychological tendencies, but rather by such things as technological advancements, resource scarcity, economics, politics and many other factors. Yes, human psychology has undeniably played a role in our transition from jungle-dweller to civilizational species (traits like inquisitiveness and empathy), but those are low-level factors that ultimately take a back seat to the emergent realities of technological, demographic, economic and politico-societal development.

Moreover, advanced civilizations likely converge around specific survivalist fitness peaks that result in the homogenization of intelligence; there won’t be a lot of wiggle room in the space of all possible survivable post-Singularity modes. In other words, an insectoid post-Singularity SAI or singleton will almost certainly be identical to one derived from ape lineage.

Therefore, attempts to extrapolate ‘human nature’ or ‘ETI nature’ to the mind of its respective post-Singularity descendant is equally problematic. The psychology or goal structure of an SAI will be of a profoundly different quality than that of a biological mind that evolved through the processes of natural selection. While we may wish to impose certain values and tendencies onto an SAI, there’s no guarantee that a ‘mind’ of that capacity will retain even a semblance of its biological nature.

So there you have it.

Transmit messages into the cosmos. Or don’t. It doesn’t really matter because in all likelihood no one’s listening and no one really cares. And if I’m wrong, it still doesn’t matter—ETIs will find us and treat us according to their will.

Is geoengineering an existential risk?

Well, Milan M. Ćirković and Richard B. Cathcart think it's a distinct possibility. In fact, it may even (partly) explain the Great Silence. Check out the abstract to their article, "Geo-engineering Gone Awry: A New Partial Solution of Fermi's Paradox":

Technological civilizations arising on such planets will be, at some point of their histories or another, tempted to embark upon massive geo-engineering projects. If, for some reasons only very recently understood, large-scale geo-engineering is in fact much more dangerous than previously thought, the scenario in which at least some of the extraterrestrial civilizations in the Milky Way self destruct in this manner gains plausibility. In addition, we speculate on possible reasons, both physical and culturological, which could make such a threat even more pertinent on an average Galactic terrestrial planet than on Earth.

Be sure to read the entire article (PDF). Learn more about geoengineering. And be sure to read Jamais Cascio's article, "It's Time to Cool the Planet."

Drake: Use the Sun as a 'magnifying glass' to find ET

SETI founder Frank Drake wants to take the search for extraterrestrial intelligence to the next level by implementing a process called gravitational microlensing.

Microlensing is based on the gravitational lens effect: massive objects can bend the light of a bright background object. This can generate multiple distorted, magnified, and brightened images of the background source. More specifically, when a distant star or quasar gets sufficiently aligned with a massive compact foreground object, the bending of light due to its gravitational field leads to two distorted unresolved images resulting in an observable magnification. The time-scale of the transient brightening depends on the mass of the foreground object as well as on the relative proper motion between the background 'source' and the foreground 'lens' object.

In other words, Drake is essentially suggesting that we use our Sun as a 'giant magnifying glass' by positioning an observatory at a distance of around 500AU from it. Theoretically, the resultant microlense would be so powerful that we could see alien planets—and even their continents and oceans.

He contends that advanced extraterrestrial civs may have been doing this for millions of years already and we need to get with the program. Moreover, Drake says this isn't just a one-way system—gravitational lensing could be used to transmit signals to other worlds as well. Considering that our civilization's entire communications schema is about to go digital, he argues that this may be our best bet to communicate with our celestial neighbors.

Okay, now the bad news. The primary problem I have with Drake's suggestion, aside from the fact that it would take over a hundred years to set the crafts into position (which is more an issue of patience than a technical concern), is that the exercise would likely result in failure. Yes, such an observatory would undoubtedly help us discover more exoplanets—even those teeming with life. But it's unlikely that we'd receive any kind of communication by using it.

Among other things, the Fermi Paradox suggests that the timescales in question would not just allow for a civ to set-up and use gravitational microlensing, but to seed every solar system in the Galaxy with Bracewell probes. Sure, extraterrestrials could set microlenses up, but if they're capable of that feat then they're not too far from being able to send out swarms of self-replicating Bracewells.

Again, like I've harped on time and time again, if there are advanced civs out there, and they've wanted to communicate with us, they would have done so by now.

I'm not suggesting that we bail on Drake's project. Quite the contrary. Let's do it. Let's set up this microlense and see what we get. A negative data point can be just as useful as a positive one. And maybe it'll help us discover Dyson Spheres or other megastructures. In addition, the astrological benefits of such an observatory would be incalculable, so it wouldn't be a complete waste by any means.

We just need to temper the expectations of the contact optimists out there, of which Frank Drake is one.

John Hodgman pulls off Fermi Paradox schtick

I totally love geek humor -- and this TED Talk by John Hodgman has plenty of it, including a bit about the Fermi Paradox and the ultimate question, "Where is everybody?"

An Introduction

Casey Rae-Hunter is guest blogging this month.

Greetings, all.

It's my pleasure to be contributing to Sentient Developments through the month of October. Being asked to come aboard was not quite as much of a shock as, say, US President Barack Obama getting a wake-up call about winning the Nobel, but as an avid reader of SD, I'm nevertheless honored to chip in at one of the finest future-forward sites on the planet (and maybe beyond).

Now that the flattery's out of the way, allow me to introduce myself and some topics I'll be covering during my tenure.

I'm a 35-year old political communications professional from Washington, DC. The core of my work is in media policy, which puts me at the spear's tip of fascinating debates concerning Internet and broadcast issues, copyright, technology and law. I probably won't be blogging about many of those topics, but I figured a little context is appropriate in this getting-to-know you phase.

Here's an important caveat: while I have an abiding interest in science and technology, I have but a layman's background in each. So as I'm waxing philosophic about H+ or possible futures in cognitive development, remember that I do so as a observer, not an expert. One of the reasons that I gladly accepted George's invite to contribute is because I knew it would be an incredible learning experience. I encourage readers to correct me where I'm wrong and not to be shy about expanding my horizons on any given topic.

Speaking of "given topics," one that I plan to examine in some detail is that of neurodiversity. In August 2009, I was diagnosed with Asperger's Syndrome, confirming what my wife and I had long suspected. Part of my coming to terms with this new information was to begin publishing an adult-AS blog, Autistic in the District, which functions as an adjunct to my main site, The Contrarian Media — a daily publication featuring 11 active contributors who write on everything from paranormal investigation to politics. To be sure, I could have tossed in the occasional rumination on living with "high functioning autism," and no one would've been outraged. Yet I wanted to personalize my experiences in the form of a true web journal, which The Contrarian most assuredly is not. My wife also wanted to offer "aspie"-oriented book reviews and talk about the positive aspects of being a "neurotypical" spouse married to someone with AS. Because a lot of what's online is pretty negative in that regard.

I'm not gong to go into the litany of reasons I decided to "disclose to the world," but the predominant motive was to serve as a positive example for other adult aspies. It's important to remember that the condition is relatively new in terms of clinical understanding and observation, having only been part of standard Pervasive Developmental Disorder (PDD) diagnoses since 1992. That means that most of the current strategies vis-a-vis Asperger's focus on children and young adults. There's nothing wrong with this, but having grown up in an era when there was no "autistic spectrum" — just tragically non-communicative individuals whose condition was thought to be brought on by "refrigerator mothers" — I know there are a great many other adults with AS who might feel sympatico with my own aspie experiences. I'm also interested in contributing to the robust public debate about whether Asperger's and other PDDs are actually gifts, rather than afflictions.

So what does any of this have to do with cognitive destiny and/or design? That's what I hope to ponder during my October hitch. Of course, I may also do the occasional theoretical tap-dance around the Fermi Paradox and the intersection of Buddhism and neuroscience. Because this is Sentient Developments, after all!

But I don't want to spoil anything, so I'll leave it at that. Thanks again to my gracious digital host — I'll talk to you soon. . .

Casey Rae-Hunter is a writer, editor, musician, producer and self-proclaimed "lover of fine food and drink." He is the Communications Director of the Future of Music Coalition — a Washington, DC think tank that identifies, examines, interprets and translates issues at the intersection of music, law, technology and policy. He is also the founder and CEO of the Contrarian Media Group, which publishes The Contrarian and Autistic in the District — the latter a blog about Asperger's Syndrome.

New theory suggests that we may not be alone after all

Astrophysicist Brandon Carter's long-standing argument against finding intelligent extraterrestrial life has been roundly challenged by a team of Serbian researchers led by Milan Ćirković.

Carter's theory assumed set timescales for two processes: the life cycle of a star and the emergence of complex life. By statistically combining the two Carter concluded that complex life takes longer to emerge than the life-friendly duration of most stars -- with the implication being that intelligence is excruciatingly rare in the Galaxy and we may be alone.

Not satisfied with this conclusion, Ćirković and colleagues Branislav Vukotić and Ivana Dragićević are now disputing these assumptions. In their Astrobiology paper, "Galactic Punctuated Equilibrium: How to Undermine Carter's Anthropic Argument in Astrobiology," they contend that there is no reason to assume life evolves only gradually. They argue life could evolve in fits and starts - mirroring an evolutionary theory called punctuated equilibrium.

The abstract of their paper reads,

Our approach is based on relaxing hidden uniformitarian assumptions and considering instead a dynamical succession of evolutionary regimes governed by both global (Galaxy-wide) and local (planet- or planetary system–limited) regulation mechanisms. Notably, our increased understanding of the nature of supernovae, gamma-ray bursts, and strong coupling between the Solar System and the Galaxy, and the theories of “punctuated equilibria” and “macroevolutionary regimes” are in full accordance with the regulation-mechanism picture. The application of this particular strategy highlights the limits of application of Carter's argument and indicates that, in the real universe, its applicability conditions are not satisfied. We conclude that drawing far-reaching conclusions about the scarcity of extraterrestrial intelligence and the prospects of our efforts to detect it on the basis of this argument is unwarranted.

In plain English, the conditions in the Universe required for the emergence of intelligent life have only recently been established (in cosmological scales). Prior to 'recent times', universal mechanisms were in place to continually thwart the evolutionary development of intelligence, namely through gamma-ray bursts, super novae and other forms of nastiness. Occasional catastrophic events have been resetting the "astrobiological clock" of regions of the Galaxy causing biospheres to start over. "Earth may be rare in time, not in space," they say. They also note that the rate of evolution is intimately connected with a planet's environment, such as the kind of radiation its star emits.

This is why the authors reject a strict uniformitarian approach; the Universe is not the same now as it was in the past.

And importantly, given the possibility that the conditions for intelligence to emerge are now in place, we shouldn't give up hope about our chances of discovering extraterrestrial life.

Assessing solipsist solutions to the Fermi Paradox

Milan M. Cirkovic is guest blogging this week.

Thanks to George Dvorsky for inviting me to blog this week on Sentient Developments.

The title of this post refers to a classic 1983 paper of Sagan and Newman criticizing Tipler's skepticism toward SETI studies based on Fermi's Paradox (FP) and strengthened by the idea of colonization via von Neumann probes. Here, however, I would like to talk about solipsist solutions to FP in a different – and closer to the usual – meaning.

Solipsist solutions reject the premise of FP, namely that there are no extraterrestrial civilizations either on Earth or detectable through our observations in the Solar System and the Milky Way thus far. On the contrary, they usually suggest that extraterrestrials are or have been present in our vicinity, but that the reasons for their apparent absence lie more with our observations and their limitations than with the real state-of-affairs.

Of course, this has been for so long the province of lunatic fringe of science (either in older forms of occultism or more modern guise of ufology) but to neglect some of these ideas for that reason is giving the quacks too much power. Instead, we need to consider all the alternatives, and these clearly form well-defined, albeit often provably wrong or undeveloped ideas. Some of the solipsist hypotheses discussed at least half-seriously in the literature are the following (listed in rough order from less to more serious ones):

• Those who believe UFOs are of extraterrestrial intelligent origin quite clearly do not have any problem with FP (e.g. J. Allen Hynek; for a succinct historical review see Chapter 6 of Dick's magnificent “Biological Universe”). The weight of evidence obviously tells otherwise.
• The Ancient astronauts speculations of Agrest, von Daniken and others belong to this class as well.
• The zoo hypothesis of Ball and the related interdict hypothesis of Fogg suggest that there is a uniform cultural policy for advanced extraterrestrial civilizations to avoid any form of contact (including having visible manifestations) with the newcomers to the Galactic Club. The reasons behind such behavior may be those of ethics, prudence or practicality. In each case, these do not really offer testable predictions (if the extraterrestrial civilizations are sufficiently powerful, as suggested by the difference in ages of the Earth and the median of the set of earthlike planets) for which they have been criticized by Sagan, Webb and others. As a consequence, a 'leaky' interdict scenario is occasionally invoked to connect with the alleged extraterrestrial origin of UFOs, which is clearly problematic.
• The directed panspermia hypothesis of Crick and Orgel, proposed in 1973, supposes that the Earth has indeed been visited in a distant past with very obvious consequence – namely the existence of life on our planet! Those two famous biochemists proposed – partly tongue-in-cheek, but partly to point out the real problems with the then theories of biogenesis – that our planet has been intentionally seeded with microorganisms originating elsewhere. In other words, we are aliens ourselves! It is very hard to see how could ever hope to test the hypothesis of directed panspermia.
• The planetarium hypothesis of Stephen Baxter suggests that our astronomical observations do not represent reality, but a form of illusion, created by an advanced technological civilization capable of manipulating matter and energy on interstellar or Galactic scales.
• The simulation hypothesis of Nick Bostrom, although motivated by entirely different reasons and formulated in a way which seemingly has nothing to do with FP, offers a framework in which FP can be naturally explained. Bostrom offers a Bayesian argument why we might rationally think we live in a computer simulation of an advanced technological civilization inhabiting the "real" universe. This kind of argument has a long philosophical tradition, going back at least to Descartes' celebrated second Meditation, discussing the level of confidence we should have about our empirical knowledge. Novel points in Bostrom's presentation include the invocation of Moore's Law for suggesting that we might be technologically closer to the required level of computing sophistication than we usually think, as well as adding a Bayesian conditioning on the number (or sufficiently generalized "cost") of such "ancestor-simulations", as he dubs them. It is trivial to see how FP is answered under this hypothesis: extraterrestrial civilizations are likely to be simply beyond the scope of the simulation in the same manner as, for example, the present-day simulation of the internal structure of the Sun neglects the existence of other stars in the universe.

It is difficult to objectively assess the value of solipsist hypotheses as solutions to FP. Most of them are either untestable in principle, or testable only in consideration of very long temporal and spatial scales; they do not belong to the realm of science as it is conventionally understood.

In other words, they violate a sort of naive realism which underlies practically the entire scientific endeavor. Their proponents are likely to retort that the issue is sufficiently distinct from other scientific problems to justify greater divergence of epistemological attitudes – but this is rather hard to justify when one could still pay a smaller price. For instance, one could choose to abandon Copernicanism, like the Rare Earth theorists (although it might be particularly unpopular this year!) or – as I personally prefer – one might abandon gradualism (which has been thoroughly discredited in geo- and planetary sciences anyway) and end up with a sort of neocatastrophic hypothesis, like the phase-transition scenario.

Some of them, but not all, solipsist solutions violate the classical non-exclusivity (or “hardness”) requirement as well; in other words, they require an uncanny degree of cultural uniformity among the advanced technological civilizations. This is, for instance, obvious in zoo, interdict or planetarium scenarios, since they presume a large-scale cultural uniformity to maintain the isolation of either just us or any other Galactic newcomers, which is sufficiently improbable a priori.

This is not the case, however, with the simulation hypothesis, since the simulated reality is likely to be clearly designed and spatially and temporally limited. The directed panspermia has some additional problems – notably the absence of any further manifestations of our 'parent civilization', in spite of its immense age. If they became extinct in the meantime, what happened with other seeded planets (not to mention long-term astroengineering artifacts)? The Copernican reasoning suggests that we should expect evolution to occur faster at some places than on Earth (and, of course, slower at other sites as well); where are our interstellar siblings, then?

Usually, these hypotheses are mentioned (if at all) mostly for the sake of logical completeness, since they are in any case the council of despair. If and when all other avenues of research are exhausted, the conventional wisdom says, we could always turn toward these hypotheses. And, strangely enough, the conventional wisdom does seem on target here. Still, this neither means that they are all of equal value nor it should mislead us into thinking that they are necessarily improbable for the reason of desperation alone.

Bostrom's simulation hypothesis might, indeed, be quite probable, given some additional assumptions related to the increase in our computing power and decrease of information-processing cost. Directed panspermia could, in principle, get a strong boost if, for instance, the efforts of NASA and other human agencies aimed at preventing planetary contamination turn out to be unsuccessful. Finally, solipsist hypotheses need not worry about evolutionary contingency or generic probabilities of biogenesis or noogenesis, unlike practically all other proposed FP solutions.

Milan M. Cirkovic

The 'Rare Earth' delusion

In my experience, the most common solution given to the Fermi Paradox is the Rare Earth hypothesis -- the idea that life in the Galaxy is exceptionally rare and that planets like ours are freakishly uncommon. For many, this conveniently explains why we haven't been visited by little green men. Or more accurately, extraterrestrial machine intelligences.

I've always thought, however, that given cosmologically large numbers that this sort of thinking is symptomatic of our small minds and limited imaginations. It's easy for us to throw up our hands and sheepishly declare that we're somehow special. Such a conclusion, however, needs to be qualified against the data involved, and by the mounting evidence in support of the notion that ours appears to be a life-friendly universe.

What Do You Mean, 'Rare'?

Let's pause for a moment and look at the numbers.

Recent figures place the total number of stars in the Milky way at an astounding three trillion. I don't need to tell you that that is a huge number. But given how poor the human mind is at groking large figures I'm going to play with this number for a bit:

• 3 trillion fully expressed is 3,000,000,000,000 (12 zeros)
  
• As an exponent it can be expressed as 3 x 10¹²
• Re-phrased, it is 3 thousand billions, or 3 million millions

Which necessarily leads to this question: given such a ginormous figure, what does it mean to be rare?

Even if the Earth is a one in a million occurrence, that means there are still 3 million Earthlike planets in the Galaxy (assuming one Earthlike planet per star). Does that qualify as rare? Not in my books.

If, on the other hand, the Earth is a one in a billion occurrence, then there are only 3,000 Earths in the galaxy. That sounds a bit more rare to me -- but one in a billion!? Seriously?

We also have to remember that the 3 trillion stars only accounts for what exists right now in the Milky Way. There have been well over a billion trillion stars in our past Universe. As Charles Lineweaver has noted, planets began forming in our Galaxy as long as 9 billion years ago. We are relative newcomers to the Galaxy.

Our Biophilic Universe

But all this numerological speculation might be moot. We're overlooking the mounting evidence indicating that we live in a universe exceedingly friendly to life. What we see in the physical laws and condition of the universe runs contrary to the expectations of the Rare Earthers.

Indeed, we are discovering that the Galaxy is littered with planets. Scientists have already cataloged 321 extrasolar planets -- a number that increases by a factor of 60 with each passing year. Yes, many of these are are so-called "hot Jupiters," but the possibility that their satellites could be habitable cannot be ruled out. Many of these systems have stable circumstellar habitable zones.

And shockingly, the first Earthlike planet was discovered in 2007 orbiting the red star Gilese 581. It's only 20 light-years away, 1.5 times the diameter of Earth, is suspected to have water and an atmosphere, and its temperature fluctuates between 0 and 40 degrees Celsius.

If we are one in a billion, then, and considering that there are only 0.004 stars per cubic light-year, what are the odds that another Earthlike planet is a mere 20 light-years away?

Indeed, given all this evidence, the Rare Earthers are starting to come under attack. Leading the charge these days is Alan Boss who recently published, The Crowded Universe. Boss estimates that there may be billions of Earthlike planets in the Milky Way alone. "I make the argument throughout the book that we already know that Earths are likely to be incredibly common—every solar-type star probably has a few Earth-like planets, or something very close to it," says Boss. "To my mind, at least, if one has so many habitable worlds sitting around for five billion or 10 billion years, it's almost inevitable that something's going to start growing on the majority of them."

Life Abounds

And it gets worse for the Rare Earthers. They also have to contend with the conclusions of astrobiologists.

It's a myth, for example, that it took life a long time to get going on Earth. In reality it was quite the oppoite. Our planet formed over 4.6 billion years ago and rocks began to appear many millions of years later. Life emerged relatively quickly thereafter some 600 million years after the formation of rocks. It's almost as if life couldn't wait to get going once the conditions were right.

We also live in a highly fertile Galaxy that's friendly to extremophiles. The Panspermia hypothesis suggests that 'life seeds' have been strewn throughout the Galaxy; evidence exists that some grains of material on Earth have come from beyond our solar system.

Recent experiments have shown that microorganisms can survive dormancy for long periods of time and under space conditions. We also now know that rocks can travel from Mars to Earth and that simple life is much more resilient to environmental stress than previously imagined. Consequently, biological diversity is probably much larger than conventionally assumed.

Common Earth

My feeling is that the Rare Earth hypothesis is a passing scientific fad. There's simply too much evidence growing against it.

In fact, the only thing going for it is the Fermi Paradox. It's comforting to think that the Great Silence can be answered by the claim that we're exceptionally special. Rare Earth steers us away from other, more disturbing solutions --namely the Great Filter hypothesis.

But such is the nature of scientific inquiry. We're not always going to like what we find, even if it is the truth.

As for the Fermi Paradox, we'll have to look for answers elsewhere.

New theory may explain why radio SETI has failed

It's been nearly 50 years since scientists first started scanning the heavens for radio signals that would indicate the presence of intelligent extraterrestrial life. And in all those 50 years we haven't heard so much as a peep. The apparent failure of radio SETI thus far has provided much of the fuel that now powers the Fermi Paradox, the observation that we haven't encountered signs of ETI's when we probably should have by now.

But a new theory may explain part of the problem and why radio SETI has so far proved fruitless. Reginald Smith from the Bouchet-Franklin Institute in Rochester argues that there is a limit to how far a radio signal from ET can travel before it becomes too faint to hear. If true, this could have interesting ramifications for radio SETI and our expectations for the project.

In his article, "Broadcasting but not receiving: density dependence considerations for SETI signals,"Smith applies his idea to the Drake Equation and derives a minimum density of civilizations below which contact is improbable within a given volume of space. The calculation depends on factors such as the lifetime of a civilization and the distance that it might be possible to communicate via radio signals. His thesis has produced some interesting scenarios.

"Assuming the average communicating civilization has a lifetime of 1,000 years, ten times longer than Earth has been broadcasting, and has a signal horizon of 1,000 light-years, you need a minimum of over 300 communicating civilization in the galactic neighborhood to reach a minimum density," writes Smith.

Consequently, if there are less than 300 advanced civilizations in our galaxy, the chances are that they’ll never notice each other. And a figure of N being less than 300 is not out of the question given recent insights into cosmology, astrobiology and the rise of the Rare Earth Hypothesis.

Smith's theory has led some to suggest that the Fermi Paradox has been solved. But their thinking here is flawed.

Our (apparent) inability to detect radio signals does not wipe away other means for extraterrestrial communication (quantum communication schemes, Bracewell probes) or detection (Dysonian SETI, interstellar calling cards, etc.), nor does it answer the issue as to why the Galaxy hasn't been colonized by now (i.e. self-replicating Von Neuman colonization probes).

So, while Smith's theory may explain the failure of radio SETI, it doesn't erase the problem of the Great Silence.

Larger Milky Way has implications for the Drake Equation and the Great Silence -- or does it?

Apropos of Russell Blackford's recent posts about the Fermi Paradox, it should be mentioned that the Milky Way is 50% larger than previously thought. This will likely have implications to our appreciation of the Drake Equation and the Fermi Paradox.

What tipped cosmologists off was the discovery that our galaxy is spinning 15% faster than formerly assumed. The lead researcher on the project, Mark Reid of the Harvard-Smithsonian Center for Astrophysics in Cambridge, estimates that the Milky Way's spin is about 914,000 km/hour, significantly higher than the widely accepted value of 792,000 km/hour.

The only thing that could account for this increased spin rate was more mass -- a lot more mass. As a result of Reid's findings, our models now need to account for a galaxy that is 50% heavier, 15% wider and contains a mind-boggling 3 trillion stars! That is an astounding 750% increase from 400 billion.

You might want to pause for a moment and think about this.

This is remarkable news and the implications of these findings are going to take a while to sink in. My first reaction was to consider the implications to the Fermi Paradox. Does a significantly larger Milky Way accentuate or diminish the problem that is the Great Silence?

First off, it throws previous Drake Equation estimates out the window. Blogger Paul Hughes has already crunched some numbers and has come up with his own estimate: he believes there may be as many as 12 billion Earth-like planets in our galaxy capable of supporting liquid water and in turn carbon-based life as we know it (Hughes doesn't take the equation beyond that as he was inquiring into the number of potentially habitable planets).

But as many of my readers know, I'm not a great fan of the Drake Equation to begin with. It's in dire need of an upgrade and it completely fails to account for the cosmological development of the galaxy and other temporal aspects. That said, it's safe to assume that the probability of extraterrestrial life emerging in the Galaxy is now significantly higher than it was before -- both in the Galaxy's long history and now.

Second, the new and improved Milky Way throws off previous calculations as to how long it would take an advanced civilization to inhabit all four corners of the galaxy. An extraterrestrial migration wave would likely be comprised of self-replicating colonization probes that spread out across the galaxy at an exponentially increasing rate. Previous estimates placed complete Galaxy-wide colonization at a few million years. Given that we were wrong about the size of the Milky Way and the number of stars, we have to conclude that it would take longer to colonize the entire galaxy.

Just how much longer I'm not sure [sounds like a future project in the making], but given that we're talking about exponentially increasing migration rates I would have to think that we are not talking about an order of magnitude. And even if it does take significantly longer, we still have to take the extreme age of the Milky Way into consideration and the likelihood that intelligence may have emerged in the Galaxy as long as 4.5 billion years ago. The age of the Galaxy is still disproportionately longer than even the most pessimistic colonization rate estimates.

What does all this mean?

Well, nothing really. The Great Silence is obviously still in effect and something's still screwy with the Universe. A bigger Milky Way means that there's likely more intelligent life in the Galaxy than we had previously assumed, but that interstellar colonization and communication rates are slightly longer.

The Fermi Paradox lives on.

Guest Blogger: Russell Blackford: Where's my alien civilisation? Part 2.

Where were we?

This year we have Darwin's 200th birthday and the 150th anniversary of the publication of On the Origin of Species. It's a natural time for thoughts to turn to issues about the origins of life and the trajectory of biological evolution. It was in that context that I found myself, this week, thinking again about the Fermi paradox and the mysteries of the Drake equation, after some discussion of these over on Richard Dawkins' site. The discussion on Dawkins' site got a bit acrimonious, for some reason, but I'm sure we can avoid that here.

At the end of Part 1., I left the Fermi paradox with questions about the fate of technological civilisations. Do they self-destruct? Do they become unrecognisable to us? Or does the rate of technological progress flatten out, in which case we are not approaching a technological singularity – rather, we are somewhere on the steep part of a sigmoid curve.

Deeper into Drake's equation

I suspect that the evidence that we're on a sigmoid curve is pretty much illusory. E.g., the evidence from science fiction is probably just evidence of limits to our imaginative capacities. Still, it's not a scenario that can be ruled out (and it seems just as possible to me as the technological singularity scenario). It's certainly conceivable that at least some kinds of technological progress flatten out. At 1 per cent of the speed of light it would take us over 400 years to reach the nearest stars. We don't know how much longer to reach the nearest worlds that could easily be colonised. We tend to think that the problems will be solved in millions of years of future progress, but we may not be good at working out what problems can and cannot be solved, at least easily enough to be worth the effort, even over very long tracts of time.

That said, I'd prefer to look for an explanation deeper in the Drake equation, which uses several variables to calculate the number of technologically advanced species in our galaxy. The variables include the average rate of star formation, the fraction of stars that have planets, the fraction of planets that can potentially support life, the fraction of these that actually develop life, the fraction of these where intelligent life evolves, the fraction of these that develop civilisations that send detectable signs of themselves into space, and the length of time that such civilisations exist.

Some of the fractions that feed into the Drake equation may be very small indeed, so small as to make technologically advanced species, and the civilisations they create, incredibly rare. It's consistent with what we now know that the conditions required for life to form are extremely fortuitous and unusual. It may need very rare combinations of environmental factors. And even then, you can have life staying at levels of neurological complexity that don't lead to technology.

We know that life can stay at levels of intelligence well below our own pretty much indefinitely. If not for one or more catastrophic events at the end of the Cretaceous Period, including the bolide impact that caused the Chicxulub Crater, Earth might still be dominated by dinosaurs, which might not have developed any impressive levels of intelligence. They hadn't done so in the previous 150-odd million years, so there's no reason to think they would have in the past 65 million years.

We really need to know a lot more, and we soon reach a point where people are relying on nothing more than hunches. With that disclaimer, my hunch is that the evolution of a technological civilisation to our sort of level or beyond is a statistically improbable event. I.e., it is an event that takes place quite infrequently in an average galaxy. I can't be much more precise about what "quite infrequently" means, except to say that I wouldn't be at all surprised if human beings were the only species in our galaxy to have created technological civilisations.

There's a lot of things we'd need to know before we could say anything more confidently, or more precise, than that. E.g., we'd need a well-corroborated theory of the origin of life to give us an idea of how rare the conditions for it really are. We just don't have one. We have a well-corroborated theory of how life diversifies - neo-Darwinian evolutionary biology - but not of how it gets started. The best we have is an idea of what sort of theory would be a workable account of abiogenesis – some kind of theory of early kinds of self-replicating molecules that were able to develop into the building blocks for the kinds of life forms from which we, and the rest of contemporary life on Earth, all eventually diversified.

There are so many unknowns about all this that I think we're a long way from being able to deduce any pessimistic conclusions about humanity's future. Even if life itself is more common in the universe than appears so far, the evolution of human-level intelligence might be very rare indeed. Even if technological change ends up following a sigmoid curve, we don't know how to unpack the detail of that – it might mean that space travel at appreciable fractions of the speed of light is going to turn out more difficult than we commonly assume … but, for all that, our ability to transform our capacities may reach levels far beyond what is current. We can't predict the future, though we can forecast and consider various possibilities and scenarios.

Still waiting

Meanwhile, I'm still waiting for my alien civilisation. I'm also waiting for my jet car. If it doesn't turn up before I shuffle off this mortal coil, I don't know if that's a reason for pessimism or optimism.

Where has the damn thing gone?


Russell Blackford is an Australian philosopher. He has published extensively (novels, short stories, academic monographs and articles, and book reviews) and is editor-in-chief of The Journal of Evolution and Technology. His home blog is Metamagician and the Hellfire Club.

Guest Blogger: Russell Blackford: Where's my alien civilisation? Part 1.

Fermi's paradox

I'm sure my readers are familiar with Fermi's paradox. Some of you may even feel it's debated to death lately, but in this great memorial year (Darwin's 200th birthday, among other things) we'll be hearing a lot more about the origins of life and the trajectory of evolution. Fermi's paradox connects with all that, and I'll get to the connection in Part 2.

Here's a quick refresher. Enrico Fermi observed that there seems to be a contradiction between the fact that we have not encountered alien civilisations and facts about the scale of the universe (and, indeed, our own galaxy). The vastness of space, the enormous number of stars and planets, and the age of the stars all add up to a presumption that there should be plenty of life Out There, some of it much older than life on Earth. If there are intelligent beings in space that began with millions of years of head start over us, why don't they have technological civilisations far more advanced than our own? But if they do, why have we never encountered such things as alien space craft, probes, or radio signals?

Colonising the galaxy

Consider that the diameter of the galaxy is about 100,000 light years. Imagine for the sake of argument that there's a technological civilisation somewhere near the galactic centre. Then imagine that it has the capacity to send out space ships or self-replicating probes or similar devices at even 1 per cent of the speed of light. It could get a ship or a probe out to the galactic rim in something like five million years.

If the alien civilisation sends out a few ships every thousand years, they will soon mount up in numbers. Over a few million years, it could send out many thousands of ships. If the colonies founded by those ships themselves got in on the act and sent out ships of their own, and the colonies they founded sent out ships, we get ourselves an exponential increase.

It looks as if a sufficiently advanced and determined civilisation could colonise the galaxy, to a greater or lesser level of density, in "only" a few million years (a tiny amount of time in geological or astrophysical terms). Perhaps not all advanced technological civilisations have that ambition, but it would only take one that has the ambition plus a few million years' start on us, and the galaxy should be widely colonised by now – at least to some density level that we’d notice. Where are the space craft, the probes, the signals, maybe even the astrophysical engineering projects?

There seems to be good evidence that the galaxy doesn't contain even one civilisation that is old enough, advanced enough, and determined enough. So, why?

You might think that if the evolution of technological civilisations were a common event in the universe, there'd be at least one civilisation like this somewhere in the galaxy, with its billions of stars. Even if it started out on the distant rim, far away from us on the other side, that's just going to make it take a few million more years to reach us. So allow ten million years of head start – that's still nothing in the kind of timeframe we're talking about. If technological civilisations are commonplace, there should be some that are those millions of years ahead of us (and some will come along behind us, trailing by a few million years).

So, where are they?

Might it be that creating space craft that can travel reliably at even 1 per cent of the speed of light is harder than we assume? Or maybe advanced technological civilisations tend to destroy themselves? Or do they tend to stop expanding their populations, as human beings are doing? We're really guessing.

The most pessimistic solution is that they tend to destroy themselves. From the point of view of our own species, that solution would suggest that our self-destuction lies ahead. If we discover life elsewhere, then, it's bad news: the more common life is, the more common technological civilisations should be, and hence the more likely it is that the reason we don't see them is that they destroy themselves. QED.

But I don't think that's the best way to look at it. There are other possibilities. Perhaps technological civilisations tend to reach a technological singularity point, at which stage they are transformed so comprehensively and deeply that we wouldn't even recognise them. They might miniaturise themselves in some way that makes expansion into space pointless, or they might switch over to some kind of substrate that we would never recognise as a form of life (partly, no doubt, for their own convenience, but perhaps partly to avoid interfering with vulnerable civilisations at our level).

Another possibility – one that might bother my transhumanist friends almost as much as the self-destruction account – is that the rate of advance of technology does not accelerate to a singularity. I.e., the mathematical relationship between time and technological capacity may not be an exponential function . Perhaps it will turn out that we are now somewhere on the relatively steep part of a sigmoid curve. In that case, perhaps advanced technological civilisations never obtain the level of technological capacity that enables them to go out and colonise galaxies. Maybe there are hard limits to what is possible, or perhaps there are universal limits to desire. If this is the correct picture, transhumanists should be disappointed – what lies ahead for the human species may not be anywhere near as radical as they hope.

The sigmoid curve interpretation has a kind of intuitive rightness about it (which doesn't mean it's correct). First, when science fiction writers describe the future they tend to imagine reaching some higher technological level and things then going on without huge change for millions of years. But of course the content of science fiction might just be evidence of limits to our current imaginative capacities.

We might also be impressed by the now-embarrassing question, "Dude, where's my jet car?" It sometimes seems that, even as the power of computer hardware continues to follow Moore's Law, progress in what we can actually do with it seems to be slowing down. "Where's my robot maid?" If so, human technological potential may be limited, and we need to imagine the future of the world with bounded horizons. Not that that need lead to crippling pessimism – it would not demonstrate our inability to produce great advances in, say, health and life span. What is and is not possible may be different from what we intuit in advance.

I think, though, that there's another way to look at this. I'll be back in a few hours to go deeper into the Drake equation.


Russell Blackford is an Australian philosopher. He has published extensively (novels, short stories, academic monographs and articles, and book reviews) and is editor-in-chief of The Journal of Evolution and Technology. His home blog is Metamagician and the Hellfire Club.

Hawking: We must colonize space in order to survive (video)

A year ago on SentDev: The Drake Equation is obsolete

Just say no to N = N* fp ne fl fi fc fL.

Copyright Lynette Cook
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 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 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.

Arbitrary at best

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.