Whither ET?

George Dvorsky with Charlie Kam, Conference Chairman of TV07

George Dvorsky is the Deputy-Editor of Betterhumans, co-founder and president of the Toronto Transhumanist Association, and the producer of the award-winning Sentient Developments blog and podcast. He served as conference chair for Transvision 2004 conference in Toronto, the World Transhumanist Association’s annual conference, and is the co-director of the Institute for Ethics and Emerging Technologies Cyborg Buddha project. He has discussed through print and broadcast media the subjects of bioethics, on topics ranging from disability rights to athletics enhancement.

At Transvision 2007 he gave a presentation entitled “Whither ET? What the Failing Search for Extraterrestrial Intelligence Tells Us About Humanity’s Future.” The talk addressed the problem of the Fermi Paradox, the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for or contact with ETs.

The following article by George Dvorsky is partly adapted from his Transvision 2007 presentation and has been reproduced here with permission from the author. The original text can be found at Sentient Developments.

The Fermi Paradox: Back with a vengeance

This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity’s future.”

The Fermi Paradox is alive and well.

As our sciences mature, and as the search for extraterrestrial intelligence continues to fail, the Great Silence becomes louder than ever. The seemingly empty cosmos is screaming out to us that something is askew.

Our isolation in the Universe has in no small way shaped and defined the human condition. It is such an indelible part of our reality that it is often taken for granted or rationalized to extremes.

To deal with the cognitive dissonance created by the Great Silence, we have resorted to good old fashioned human arrogance, anthropocentrism, and worse, an inter-galactic inferiority complex. We make excuses and rationalizations like, ‘we are the first,’ ‘we are all alone,’ or, ‘why would any advanced civilization want to bother with us backward humans?’

Under closer scrutiny, however, these excuses don’t hold. Our sciences are steadily maturing and we are discovering more and more that our isolation in the cosmos and the dearth of observable artificial phenomenon is in direct violation of our expectations, and by consequence, our own anticipated future as a space-faring species.

Indeed, one of the greatest philosophical and scientific challenges that currently confronts humanity is the unsolved question of the existence of extraterrestrial intelligences (ETI’s).

We have yet to see any evidence for their existence. It does not appear that ETI’s have come through our solar system; we see no signs of their activities in space; we have yet to receive any kind of communication from them.

Adding to the Great Silence is the realization that they should have been here by now — the problem known as the Fermi Paradox.

The Fermi Paradox
The Fermi Paradox is the contradictory and counter-intuitive observation that we have yet to see any evidence for the existence of ETI’s. The size and age of the Universe suggests that many technologically advanced ETI’s ought to exist. However, this hypothesis seems inconsistent with the lack of observational evidence to support it.

Largely ignored in 1950 when physicist Enrico Fermi famously asked, “Where is everybody,” and virtually dismissed at the seminal SETI conference in 1971, the conundrum was given new momentum by Michael Hart in 1975[1] (which is why it is sometimes referred to as the Fermi-Hart Paradox).

Today, 35 years after it was reinvigorated by Hart, it is a hotly contested and relevant topic — a trend that will undoubtedly continue as our sciences, technologies and future visions develop.

Back with a vengeance
A number of inter-disciplinal breakthroughs and insights have contributed to the Fermi Paradox gaining credence as an unsolved scientific problem. Here are some reasons why[2]:

Improved quantification and conceptualization of our cosmological environment
The scale of our cosmological environment is coming into focus. Our Universe contains about 10^11 to 10^12 galaxies, giving rise to a total of 10^22 to 10^24 stars[3]. And this is what exists right now; there have been a billion trillion stars in our past Universe. [4]

The Milky Way itself, which is considered a giant as far as galaxies go, contains as many as 400 billion stars and has a diameter of 100,000 light years.[5]

Improved understanding of planet formation, composition and the presence of habitable zones
The Universe formed 13.7 billion years ago. The Milky Way Galaxy formed a mere 200 million years later, making our Galaxy nearly as old as the Universe itself. Work by Charles Lineweaver has shown that planets also began forming a very long time ago; he places estimates of Earth-like planets forming 9 billion years ago (Gyr).

According to Lineweaver, the median age of planets in the Galaxy is 6.4+/0.7 Gyr which is significantly more than the Earth’s age. An average terrestrial planet in the Galaxy is 1.6 Gyr older than the Earth. It is estimated that three quarters of earth-like planets in the Galactic habitable zone are older than the Earth.

We have a growing conception of where habitation could be sustained in the Galaxy. The requirements are a host star that formed between 4 to 8 Gyr ago, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, an environment free of sterilization events (namely super novae), and an annular region between 7 and 9 kiloparsecs from the galactic center that widens with time. [6]

The discovery of extrasolar planets
Over 240 extrasolar planets have been discovered as of May 1, 2007[7]. Most of these 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.

Somewhat shockingly, the first Earth-like planet was discovered earlier this year orbiting the red star Gilese 581; it is 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.[8]

Confirmation of the rapid origination of life on Earth
The Earth formed 4.6 Gyr ago and rocks began to appear 3.9 Gyr ago. Life emerged quickly thereafter 3 Gyr ago. Some estimates show that life emerged in as little as 600 million years after the formation of rocks.[9]

Growing legitimacy of panspermia theories
There is a very good chance that we inhabit a highly compromised and fertile Galaxy in which ‘life seeds’ are strewn about. The Earth itself has been a potentially infectious agent for nearly 3 billion years.

Evidence has emerged that some grains of material in our solar system came from beyond our solar system. Recent experiments show 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.[10]

Discovery of extremophiles
Simple life is much more resilient to environmental stress than previously imagined. Biological diversity is probably much larger than conventionally assumed.

Developing conception of a biophilic Universe in which the cosmological parameters for the existence of life appear finely tuned
As scientists delve deeper and deeper into the unsolved mysteries of the Universe, they are discovering that a number of cosmological parameters are excruciatingly specific. So specific, in fact, that any minor alteration to key parameters would throw the entire Universe off kilter and result in a system completely unfriendly to life. The parameters of the Universe that are in place are so specific as to almost suggest that spawning life is in fact what the Universe is supposed to do. [11]

Cosmological uniformitarianism implies that that anthropic observation need not be and cannot be specific to human observers, but rather to any observer in general; in other words, the Universe can support the presence of any kind of observer, whether they be here on Earth or on the other side of the cosmos.

Confirmation of the early potential for intelligent life
My own calculations have shown that intelligence could have first emerged in the Universe as long as 4.5 Gyr ago — a finding that is consistent with other estimates, including those of Lineweaver and David Grinspoon.[12]

Refinement of evolutionary biology, computer science and systems theories
Evolution shows progressive trends towards increasing complexity and in the direction of increasing fitness. There has also been the growing acceptance of Neo-Darwinism.

Advances in computer science have reshaped our conception of what is possible from an informational and digital perspective. There is the growing acceptance of systems theories which take emergent properties and complexity into account. Game theory and the rise of rational intelligence add another level to this dynamic mix.

Development of sociobiological observations as they pertain to the rapid evolution of intelligent life and the apparent radical potential for advanced intelligence
Exponential change. Moore’s Law. Kurzweil’s Law of Accelerating Returns. Steady advances in information technologies. Artificial intelligence. Neuroscience. Cybernetics, and so on.

And then there is the theoretic potential for a technological Singularity, digital minds, artificial superintelligence, molecular nanotechnology, and other radical possibilities. There is also emerging speculation about the feasibility of interstellar travel, colonization and communication.

In other words….
There are more stars in the Universe than we can possibly fathom. Any conception of ‘rare,’ ‘not enough time’ or ‘far away’ has to be set against the inability of human psychology to grasp such vast cosmological scales and quantities. The Universe and the Milky Way are extremely old, our galaxy has been able to produce rocky planets for quite some time now, and our earth is a relative new-comer to the galaxy.

The composition of our solar system and the Earth itself may not be as rare as some astronomers and astrobiologists believe. These discoveries are a serious blow to the Rare Earth Hypothesis – the idea that the genesis, development and proliferation of life is an extremely special event[13]. It’s also a blow to Brandon Carter’s anthropic argument which takes a very human-centric approach to understanding cosmology, suggesting that our existence as observers imposes the sort of Universe that only we can observe.

Finally, the Universe appears capable of spawning radically advanced intelligence – the kind of advanced intelligence that transhumanists speculate about, namely post-Singularity, post-biological machine minds. Given intelligent life’s ability to overcome scarcity, and its tendency to colonize new habitats, it seems likely that any advanced civilization would seek out new resources and colonize first their star system, and then surrounding star systems. Indeed, estimates place the time to colonize the Galaxy anywhere from one million to 100 million years.[14]

The fact that our Galaxy appears unperturbed is hard to explain. We should be living in a Galaxy that is saturated with intelligence and highly organized. Thus, it may be assumed that intelligent life is rare, or, given our seemingly biophilic Universe, our assumptions about the general behaviour of intelligent civilizations are flawed.

A paradox is a paradox for a reason: it means there’s something wrong in our thinking.

So, where is everybody?


The Fermi Paradox: Advanced civilizations do not…

This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity’s future.”

As I stated in my previous article, “The Fermi Paradox: Back with a vengeance”:

The fact that our Galaxy appears unperturbed is hard to explain. We should be living in a Galaxy that is saturated with intelligence and highly organized. Thus, it may be assumed that intelligent life is rare, or, given our seemingly biophilic Universe, our assumptions about the general behaviour of intelligent civilizations are flawed.

A paradox is a paradox for a reason: it means there’s something wrong in our thinking.

So, let’s try to figure out what’s going on. Given the Great Silence, and knowing what we may be capable of in the future, we can start to make some fairly confident assumptions about the developmental characteristics of advanced civilizations.

But rather than describe the possible developmental trajectories of extraterrestrial intelligences (ETI’s) (a topic I’ll cover in my next article), I’m going to dismiss some commonly held assumptions about the nature of advanced ETI’s – and by consequence some assumptions about our very own future.

Advanced civilizations do not…

…advertise their presence to the local community or engage in active efforts to contact

As SETI is discovering (but is in denial about), space is not brimming with easily detectable radio signals. SETI’s work during the past 40 years indicates that the quest to detect signals will not be easy.

This problem is not as simple as it sounds. A common apology is that we’ve only recently started our search and we have only scratched the surface. The trouble, however, is that it would be no problem for an ETI to communicate with us if they wanted to.

To do this all they would need to do is seed the Galaxy with Bracewell probes (a self-replicating communications beacon). This scenario was explored in Carl Sagan’s Contact in which a Bracewell probe was lying in wait about 26 light years from Earth in the Vega system. The probe was activated by our radio signals, causing it to direct powerful radio signals at Earth – signals that would not be overlooked.

We know that no such object exists in our solar system or within a radius of about 25 to 50 light years. Our radio activity should have most certainly activated any probe lying dormant in our local vicinity by know. It is also reasonable to assume that if ETI’s embarked on such a communications mission that every solar system would likely have its own Bracewell probe.

Which in turn raises a more troubling question: if ETI’s could construct and distribute probes in this way, why haven’t they gone the extra mile and spread other types of self-replicating devices such as uplift or colonization probes?

…engage in any kind of megascale engineering or stellar re-engineering that is immediately obvious to us within our light cone

All stellar phenomenon that we have observed to this point in time appears ‘natural’ and unmodified. We see no clusters of perfectly aligned stars, nor do we signs of Kardashev III civilizations utilizing the energy output of the entire Milky Way.

As for our light cone, the Milky Way is 100,000 light years in diameter; given the possibility that our Galaxy has been able to support intelligent life for about 4.5 billion years, a 100 million year time lag (at its worst) is not severe enough to cause observational problems (except for distant Galaxies).

…colonize the Galaxy

Our Galaxy remains uncolonized despite the theoretical potential for advanced ETI’s to do so – namely the time and the technology. All that would be required is a self-replicating Von Neumann probe that proliferates outward at an exponential rate. Technologies required to build such a spacecraft would include artificial intelligence, molecular assembling nanotechnology, and an advanced propulsion scheme like anti-matter rockets, beamed energy, or interstellar ram-jets.

The reason for non-colonization is not obvious (hence the Fermi Paradox). In addition to technological feasibility there is the issue of economic and sociological imperatives for colonization.

…sterilize the Galaxy

Finally, some good news. We know the Galaxy is not sterile because we exist here on Earth.

Like the colonization potential, the prospect for an advanced ETI to sterilize the Galaxy exists through the use of berserker probes (a term attributed to Fred Saberhagen). These probes could steer NEO’s at planets, unleash nanotechnological phages, or toast planets with directed beams of highly concentrated light.

And like the Bracewell scenario, if a beserker was lying dormant in our solar system it should have destroyed us by now. If sterilization is the goal, there is no good reason for it to wait – particularly as our own civilization hurtles towards a Singularity transition.

Reasons for unleashing fleets of berserkers can be conceived, including xenophobic sociological imperatives or a malign artificial superintelligence (pdf). And all it would take is one civilization to do it. But as Robert Freitas has stated, “The present observational record can only support the much more restricted conclusion that no rapacious galactic civilisations are currently loose in the Galaxy.”

…uplift or interact with pre-Singularity intelligences and biospheres

As a civilization that has been left to fend for itself, we have to assume that we, like any other civilization out there, goes it alone. No one is coming to help us. The Great Silence will continue.

Moreover, our presence on Earth and our civilizational development can be explained by naturalistic phenomena. Our existence and ongoing progress has been devoid of extraterrestrial interventions. If we’re going to survive the Singularity, or any other existential risks for that matter, it will have to be of our own devices.

…re-engineer the cosmos

A number of prominent futurists, a list that includes Ray Kurzweil and Hans Moravec, have speculated that the destiny of advanced intelligence is to re-work the cosmos itself. This has been imagined as an ‘intelligence explosion’ as advanced life expands outward into the cosmos like a bubble. The entire Galaxy would be re-organized with much of its matter converted into computronium. Eventually, it is thought that the laws of the Universe will be re-tuned to meet the needs of advanced civilizations.

Unfortunately, we do not appear to inhabit a Universe that even remotely resembles this model. The cosmos appears natural and unperturbed.

This is reminiscent of the God problem and the presence of evil. We live in a Universe that is hostile, indifferent and pointless. If advanced ETI’s had the capacity to re-engineer the Universe such that it was safer, more meaningful and paradisical they would have done so by now. By virtue of the fact that we observe such a dangerous Universe we should probably conclude that such a project is not an option.

In the final part of this series I will make an effort to explain why advanced civilizations don’t do these things and what they might be doing instead.


The Fermi Paradox: Possible solutions and next steps

This article is partly adapted from my TransVision 2007 presentation, “Whither ET? What the failing search for extraterrestrial intelligence tells us about humanity’s future.”

In my previous two articles I attempted to re-affirm the Fermi Paradox (FP) and circumscribe some of the possible interstellar activities and developmental aspects of advanced extraterrestrial intelligences (ETI’s).

In this article I will offer two broad solutions to the FP: 1) unavoidable self-destruction and 2) localized non-migratory existence.

It is not my intention at this time to provide a complete list of possible reconciliations, nor am I claiming to have found any kind of special answer; I just wish to explore these two particular possibilities.

At the conclusion of this article I offer some suggestions to help us move forward as we work to solve the observational problem that is the Great Silence.

Self-Destruction and the Great Filter

This is the most likely and philosophically satisfying answer to the Fermi Paradox – although hardly the most desirable.

Looking at ourselves as a typical example of a pre-Singularity civilization, what do we find? We find a species already in possession of apocalyptic technologies and on the verge of developing an entirely new generation of lethal weapons. In short order we will be required to manage an assortment of apocalyptic technologies; it will be akin to spinning plates. There are only so many that can be managed before one of them falls – and one is all that is needed to end the story.

Examples of pending existential risks include the ongoing threat of nuclear holocaust, a nanotechnological disaster, poorly programmed artificial superintelligence (ie Singularity as extinction event), catastrophic pandemic, and so on.

A counter-argument is often made that self-inflicted catastrophism could never be exclusive to all civilizations. How is it, ask critics, that all civilizations cannot escape such a fate? Robin Hanson attempted to answer this question by proposing the Great Filter hypothesis – the suggestion that a developmental stage exists for all life which is insurmountable. The question then: is the Great Filter behind us, or does it await us in our future?

I would argue, based on much of the data I presented earlier, that the Rare Earth hypothesis has to be rejected. Moreover, a healthy application of the self-sampling assumption strongly indicates that the filter is ahead of us should it exist. The Galaxy is likely brimming with life, including complex life.

As for as the search for extraterrestrial life is concerned, Hanson argues that the detection of ETI’s would be bad. This would indicate, given our observation of an unperturbed, uncolonized galaxy, that the Great Filter is indeed still ahead of us.

Another disturbing data point as a self-sampling species is that we here on earth have come to possess apocalyptic technologies long before we have developed the capacity to live off-planet or live in self-contained biospheres. All our eggs are in one basket and they will continue to remain that way into the foreseeable future.

And then there’s the disturbing Doomsday Argument which suggests that we’re closer to the end than the beginning of human civilization.

Perhaps the most common and smug solution to the Fermi Paradox is the suggestion that we are the first. It is frequently used because it is said to best satisfy Occam’s Razor. But while it may be the simplest solution, it defies our sense of probability and disregards the central lesson of the Copernican Principle – the idea that we are not unique, and very likely a typical example.

Earlier I presented a picture of a biophilic Universe. If this issue is to be settled by a battle between Occam’s Razor and the Copernican principle, on this matter I’ll take Copernicus any day.

Interestingly, the longer we survive as a species without extraterrestrial contact, the more we can assume that we have passed the Great Filter.

Localized non-migratory digital existence

Now, the prospect of human extinction is quite obviously mere speculation. As Morpheus proclaimed in the Matrix: “We are still here!” Consequently, there are some non-extinction scenarios that I would like to explore.

The past 40 years of scientific progress has forced a re-evaluation of humanity’s potential. We appear to be headed for a transformation that takes us away from biological existence and towards a postbiological, or digital existence. Our future visions must take this into account. As Milan Cirkovic and Robert Bradbury have noted, we need to adopt a digital perspective (pdf).

Why leave the local system when everything can be accomplished at home? Localized existence may hold promise for all the aspirations that an advanced intelligence could conceivably conjure.

Specifically, advanced intelligences may engage in computational megaprojects and live virtual reality existences. It would be an existential phase transitioning into virtual space such that interstellar colonization would never emerge as a feasible option or experiment.

For example, advanced ETI’s may construct Jupiter (pdf) and Matrioshka Brains. A Jupiter Brain would utilize all the matter of entire planet for the purpose of computation, while a Matrioshka Brain (a kind of Dyson sphere) would utilizes the energy output of its parent star.

Determining an upper bound for computational power is difficult, but a number of thinkers have given it a shot. Eric Drexler has outlined a design for a system the size of a sugar cube that would perform 10^21 instructions per second. Robert Bradbury gives a rough estimate of 10^42 operations per second for a computer with a mass on order of a large planet. Seth Lloyd calculates an upper bound for a 1 kg computer of 5*10^50 logical operations per second carried out on ~10^31 bits – this would likely be done on a quantum computer or computers built of out of nuclear matter or plasma [see this article and this article for more information].

More radically, John Barrow has demonstrated that, under a very strict set of cosmological conditions, indefinite information processing (pdf) can exist in an ever-expanding universe.

This type of computational power is astounding and defies human comprehension. It’s like imagining a universe within a universe — and that may be precisely be how it’s used.

What would a future civilization do with all this power?

A civilization’s transition into high-speed digital mode may come about as natural consequence of its development. The switch from an analog civilization to a digital one – one in which the clock-speed would be accelerated to billions if not trillions of times faster than before – would preclude the desire to interact with the outside world.

Megascale computers may be used to support uploaded civilizations. It may prove to be the existential substrate of choice – one in which the potential for self-destruction is greatly mitigated.

Advanced civilizations may also use this computer power to run simulations for reasons of scientific research, running ancestor simulations or for entertainment (pdf) purposes. Simulations may also be run as a part of some sort of ethical or sociological necessity.

Another possibility is the Hedonistic Imperative, a term attributed to David Pearce. Given that virtually every religion has fantasized about an afterlife of bliss and an end to suffering, paradise engineering may come to represent the optimal end-state for intelligent life. Ultimately, societies will always be comprised of conscious individuals. The optimization of subjective experience may take precedence over colonial ambitions.

This tendency may be part of a broader, more ‘existential’ focus on life. Civilizational achievement may not be measured by the rate of imperialistic expanse or by how much energy it can consume, but in how individuals relate to themselves and their place in the Universe. This quest for introspective enlightenment may be characterized by efforts to optimize the mode of conscious experience.

What about long term survival?

In regards to long-term survival, Vernor Vinge has predicted that post-Singularity intelligences will build local secondary systems to ensure the near-immortality of the infocomplex. These could exist in off-planet repositories. Shields composed of nanotechnology and femtotechnology could deal with the issue of gamma ray bursters and other cosmological threats.

As for the local star, it could be given added life through stellar-engineering projects in which the crucially low elements are re-introduced. Eventually, however, migration to a younger star would be necessary.

There may also be unknown reasons for this type of existence. But what is certain is that wide-scale colonization is not in the cards.

Moving Forward

Admittedly, these two broad solutions — self-destruction and non-migration scenarios — are unsatisfactory. The notion that not even one civilization can escape self-destruction is difficult to believe. Moreover, localized digital existence and the proliferation of colonization waves are not either/or scenarios; one can imagine a civilization embarking on both paths.

As we move forward in attempting to solve the FP we need to apply much stricter methodologies to the problem.

Solutions to the FP must avoid the trappings of sociological analyses, which often present non-exclusive scenarios. Answers like the ‘zoo hypothesis,’ ‘non-interference,’ or ‘they wouldn’t find us interesting,’ tend to be projections of the human psyche and our own modern-day realities. Moreover, these sorts of solutions, while they may account for some of the actions of advanced civilizations, cannot account for all.

Instead, a more rigid and sweeping methodological frame needs to be applied– one which takes cosmological determinism and sociological uniformitarianism into account. In other words, we need to be concerned with cosmological limits and the pressure of physical and resource constraints.

This is what is Nick Bostrom refers to as the strong convergence hypothesis — the idea that all sufficiently advanced civilizations converge towards the same optimal state. This is a hypothesized developmental tendency akin to a Dawkinsian fitness peak — the suggestion that identical environmental stressors, limitations and attractors will compel intelligences to settle around optimal existential modes. This theory does not favour the diversification of intelligence – at least not outside of a very strict set of living parameters.

The trick will be to predict what these deterministic constraints are. One can imagine factors such as limited resources, access to energy, computational requirements (including heat dissipation, error correction, and latency problems) and self-preservational modes (i.e. political and social orientations that eliminate the possibility of self-destruction).

A side benefit of this exercise is that it doubles as a foresight activity. The better we become at predicting the make-up of advanced ETI’s, the better we will be at predicting our own future.

Consequently, our very own survival may depend on it.



[1] Hart, M. H. “An Explanation for the Absence of Extraterrestrial Life on Earth,” Quarterly Journal of the Royal Astronomical Society, 16, 128-135 (1975).


[2] This list, which is not intended to be a complete re-affirmation of the Fermi Paradox, was inspired and partly adapted from: Ćirković , Milan M. and Bradbury, Robert J. “Galactic Gradients, Postbiological Evolution and the Apparent Failure of SETI”, New Astronomy, vol. 11, pp. 628-639 (2006).


[3] “How many stars are there in the Universe?” European Space Agency, Space Scientist, February 23, 2004: http://www.esa.int/esaSC/SEM75BS1VED_index_0.html.


[4] Hanson, R. 1999, “Great Filter,” (preprint at http://hanson.berkeley.edu/greatfilter.html).


[5] See Harvey Mudd and S. E. Levine: “Mass of the Milky Way and Dwarf Spheroidal Stream Membership.”


[6] Gonzalez, G., Brownlee, D., and Ward, P. 2001, The Galactic Habitable Zone: Galactic Chemical Evolution,Icarus 152, 185-200; Lineweaver, Charles H., Fenner , Yeshe, and Gibson, Brad K. 2004, “The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way.”; M. Noble , Z. E. Musielak , and M. Cuntz: 2002, “Orbital Stability of Terrestrial Planets inside the Habitable Zones of Extrasolar Planetary Systems”


[7] “A Rush of New Planets,” Astrobiology Magazine: Jun 02, 2007: http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=2351


[8] “All Wet? Astronomers Claim Discovery of Earth-like Planet,” Scientific American, April 24, 2007: http://www.sciam.com/article.cfm?articleID=25A261F0-E7F2-99DF-313249A4883E6A86&chanID=sa007


[9] See Stephen J. Mojzsis: http://spot.colorado.edu/~mojzsis/


[10] Raulin-Cerceau, F., Maurel, M.-C., and Schneider, J. 1998, “From panspermia to bioastronomy, the evolution of the hypothesis of universal life,” Orig. Life Evol. Biosph. 28, 597; “Encore: Great Debates Part VI,” Astrobiology Magazine, Aug 19, 2002: http://www.astrobio.net/news/article254.html


[11] The Wikipedia entry on the Fine Tuning argument has some good links and references: http://en.wikipedia.org/wiki/Fine-tuned_universe


[12] Dvorsky, George: 2006, “When Did Intelligent Life First Emerge in the Universe?” http://sentientdevelopments.blogspot.com/2006/06/when-did-intelligence-first-emerge-in.html;


[13] Ward, P. D. and Brownlee, D. 2000, Rare Earth: Why Complex Life Is Uncommon in the Universe (Springer, New York). Lineweaver, Charles H., Fenner , Yeshe, and Gibson, Brad K. 2004; Grinspoon, David, Lonely Planets, Ecco; 1st edition (November 4, 2003).


[14] Ćirković , Milan M., 2003: “On the Importance of SETI for Transhumanism.” As it pertains to reframing the Fermi Paradox, Ćirković recommends Lytkin, Finney, and Alepko (1995; for Tsiolkovsky), Jones (1985; for Fermi), Viewing (1975), and Hart (1975), (Tipler 1980), Boyce (1979).


Related Articles: Survival of the Diverse: Martine Rothblatt proposes the engineering of Beme Neural Architecture in creating digital copies of human consciousness.

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