Some Thoughts on Fermi's Paradox

The Drake equation, developed in the 1960s by the astronomer Frank Drake, laid the foundation for the scientific search for extraterrestrial life. This equation provides a way to estimate the number of intelligent, communicating civilizations in the Milky Way galaxy by combining all the prerequisites for the existence of such civilizations.

The remarkable thing about the Drake equation is that even seemingly conservative values for its various factors tend to predict a galaxy overflowing with life and intelligence, with tens, hundreds or even thousands of extraterrestrial civilizations. (Try it out and see for yourself.) Yet, indisputably, the observational evidence does not match that expectation. We know of no convincing evidence that there are any other intelligent species in the cosmos.

This is Fermi’s paradox, named after the physicist Enrico Fermi who is said to have first posed it, and it cries out for an explanation. Some people have proposed that intelligent life is much harder to develop than we think, and we are indeed the only sentient species in the galaxy. Others hypothesize that intelligent life arises frequently, but tends to destroy itself through resource exhaustion or planetary war just as quickly.

Personally, I doubt that either of these are the case. We now know that planetary systems are abundant in our galaxy. The geologically rapid appearance of life on Earth, dating back to within a few hundred million years after the world had cooled enough to make it possible, suggests that on a planetary scale life is not so hard to come by. And once life exists, intelligence seems like a fairly obvious adaptation – a “Good Trick”, as Daniel Dennett puts it, one that has utility in a wide variety of contexts and would be likely for evolution to stumble upon eventually. Perhaps some intelligent species destroy themselves, but surely not all of them do; there must be at least a few who are intelligent enough to recognize their danger and avert it. Both these hypotheses seem unlikely to me on statistical grounds. But then, why have we not detected signals from other intelligent life? I’ll survey a few explanations that seem at least possible:

The “we came first” hypothesis. No matter how many intelligent species there are, one must come first. It may be that, by some astonishing stroke of luck, humanity is the first. Or, a slightly weaker alternative: we are not the first but one of the first, and other civilizations have not existed long enough for their signals to traverse the vast distances of interstellar space to reach us.

I am well aware that many other hypotheses which granted humanity a special or privileged place in the grand scheme of things have been disproven. This explanation might seem to be another suspiciously anthropocentric speculation. Especially, given the vast periods of cosmic time that elapsed prior to our appearance and the exponentially rapid development of high technology and culture in our own species as compared to geological time, it might seem that there have been ample opportunities for others to precede us. However, that need not be the case. There could, for instance, be some previously undiscovered property of the universe that only makes the existence of complex, intelligent life feasible after a certain point in time, and so our appearance as one of the first sentient species would be no coincidence.

The smoke-signal hypothesis. Imagine that at some point in the distant past, before European contact and the age of colonialism, a native civilization in the Americas or the Pacific islands wondered if they were the only human society in the world, or if there might be other, more advanced civilizations across the vast and uncharted oceans that surrounded them. Imagine that this society was accustomed to communicating over great distances with smoke signals, and assumed that a more advanced society would do the same thing, only on a larger scale. Accordingly, they dispatch watchers to the peak of a nearby mountain to search the horizon for vast columns of smoke that these hypothetical societies might be using to signal across oceans. Finding none, the watchers return and report that as far as they can tell, their civilization is alone in the cosmos.

This analogy may apply to our own situation. We are searching the sky for radio waves and other forms of electromagnetic radiation, assuming that this is how a more advanced species would communicate. However, it may be that there are advanced civilizations using something else far superior, something which we do not even know about yet, and that these civilizations have no pressing interest in making contact with a species at such a primitive stage of development that they do not know about this other means.

The zoo hypothesis. One suggestion I find particularly ironic is that there are advanced civilizations that are well aware of our existence, but are deliberately choosing to conceal themselves from us so as not to panic a species at an insufficient level of intellectual development to handle such a discovery wisely. We could imagine this as something like the “Prime Directive” of Star Trek, the rule that forbids advanced spacefaring civilizations from disrupting the normal course of development of those that have not yet attained this technological level. Less charitably, we could interpret it in the way the term “zoo hypothesis” implies – to them, we are like animals in a zoo, living out our lives placidly with no clue that we are being gawked at by watchers on the other side of the one-way glass.

The infeasibility hypothesis. Futurists often predict that technology will increase without limit. The astronomer Nikolai Kardashev, for example, proposed a three-point scale for species able to harness all the power available in a single planet, star, or galaxy respectively. A Type III Kardashev civilization would be advanced beyond imagining, and even a Type II would be vastly superior to anything humanity can currently hope to match. However, perhaps the error is in assuming that this is an inevitable or even possible progression. Perhaps it is just too hard to become the kind of planet-shaping society many futurists envision. The laws of physics may not allow it: perhaps the materials that can possibly be created are too weak, the energy we can usefully collect too small. If that is the case, technology levels equal to or slightly above that which is currently possessed by humanity may be the limit dictated by the cosmos, and interstellar communication and travel may never occur because it is impossible to engage in the kind of engineering that such an endeavor would require.

The missed signal hypothesis. Intelligent aliens do exist, they are trying to make contact, and they are transmitting the right kind of signal – but we’re not listening. Programs such as SETI have been mocked by politicians as frivolous wastes of money (meanwhile, those same politicians almost always vote for the development of powerful new destructive weapons systems), and at the moment depend largely on private sources of funding. As a result, there are large sections of the sky whose radio coverage is poor or nonexistent, and there is no way of knowing until we look if there are signals arriving from those regions that we are missing. The cosmos could be awash in intelligent signals that we, in our inward-looking myopia, have completely failed to see.

About Adam Lee

Adam Lee is an atheist writer and speaker living in New York City. His new novel, Broken Ring, is available in paperback and e-book. Read his full bio, or follow him on Twitter.

  • Jim Baerg

    I lean far over to the view that technological civilizations develope rather rarely. Something like 1 per galaxy in several billion years. A type II civilization would be quite conspicuous, & it’s hard to see how humans can not get to that point if we don’t wreak ourselves.

    See:
    http://members.aol.com/howiecombs/alone.htm
    for a good elaboration of the argument.

    As for why the development of high tech civilization would be rare, see the book _Rare Earth_ http://www.amazon.com/Rare-Earth-Complex-Uncommon-Universe/dp/0387987010

    One might also speculate about whether it takes a rare bit of good luck for a scientific/industrial revolution to occur even once there is intelligent life. Was it a matter of luck that it occurred 1st in Europe or is it lucky that it occurred anywhere on earth?

  • Jim Baerg

    I lean far over to the view that technological civilizations develope rather rarely. Something like 1 per galaxy in several billion years. A type II civilization would be quite conspicuous, & it’s hard to see how humans can not get to that point if we don’t wreak ourselves.

    See:
    http://members.aol.com/howiecombs/alone.htm
    for a good elaboration of the argument.

    As for why the development of high tech civilization would be rare, see the book _Rare Earth_ http://www.amazon.com/Rare-Earth-Complex-Uncommon-Universe/dp/0387987010

    One might also speculate about whether it takes a rare bit of good luck for a scientific/industrial revolution to occur even once there is intelligent life. Was it a matter of luck that it occurred 1st in Europe or is it lucky that it occurred anywhere on earth?

  • Gary J. Bivin

    My personal hypothesis is that, while intelligence may be fairly common in the universe, technological civilizations may be much more rare.

    Most intelligent species may not be equipped physically or mentally to manipulate their environment to the degree that homo sapiens is: dolphins and whales, for example, are quite intelligent but limited by nature in technoligical ability. And many or most intelligent species, even though they have technological ability, may limit their activities in order to maintain balanced and healthy environments — something we may be forced to do ourselves in the not-too-distant future.

    Such species, even though they might build simple or even advanced cultures, would be undetectable at a distance. Interplanetary or interstellar civilizations may be a rarity rather than a natural development of intelligence, and may have limited lifespans.

    My guess? At any one time, there may only one or two industrial civilizations in a galaxy, and long periods may pass when there are no such civilizations at all. The average distance between any two existing at the same time would be on the order of the size of the galaxy itself — several hundred thousand light years. It’s little wonder that we haven’t detected any signals.

  • Gary J. Bivin

    My personal hypothesis is that, while intelligence may be fairly common in the universe, technological civilizations may be much more rare.

    Most intelligent species may not be equipped physically or mentally to manipulate their environment to the degree that homo sapiens is: dolphins and whales, for example, are quite intelligent but limited by nature in technoligical ability. And many or most intelligent species, even though they have technological ability, may limit their activities in order to maintain balanced and healthy environments — something we may be forced to do ourselves in the not-too-distant future.

    Such species, even though they might build simple or even advanced cultures, would be undetectable at a distance. Interplanetary or interstellar civilizations may be a rarity rather than a natural development of intelligence, and may have limited lifespans.

    My guess? At any one time, there may only one or two industrial civilizations in a galaxy, and long periods may pass when there are no such civilizations at all. The average distance between any two existing at the same time would be on the order of the size of the galaxy itself — several hundred thousand light years. It’s little wonder that we haven’t detected any signals.

  • http://www.blacksunjournal.com BlackSun

    Like Gary J. Bivin said, I would surmise that technological civilizations might arise often but for whatever reason most have a limited lifespan. Even if our civilization managed to last 10,000 years at present levels of development, that is an eye-blink in eternity. So calculating not only distance, but time as a separator makes the likelihood of contact very low.

    But who knows?

  • http://www.blacksunjournal.com BlackSun

    Like Gary J. Bivin said, I would surmise that technological civilizations might arise often but for whatever reason most have a limited lifespan. Even if our civilization managed to last 10,000 years at present levels of development, that is an eye-blink in eternity. So calculating not only distance, but time as a separator makes the likelihood of contact very low.

    But who knows?

  • law & disorder

    I was quite intrigued by the smoke signal hypothesis! It’s certainly the most humble of them all; given the fact that humanity’s development has been one humbling realization after another, it would seem to fit the trend.

    Relying on radio transmission to communicate across the interstellar divide would be just about as inadequate as sending smoke signals across an ocean. We will undoubtably find radio too cumbersome by the time we visit the moons of Jupiter, let alone should we become a true spacefaring civilization. Perhaps civilizations emit only a centuries-long ‘flash’ of radio signals before moving onto some unimagined mode of communication; this idea parallels the “march toward self-destruction” hypothesis, except it replaces the end of civilization with nothing more than the end of radio transmissions. I find the latter to be at least as possible as the former, particularly when one considers the potential for faster means of communication already being hinted at by quantum entanglement.

  • law & disorder

    I was quite intrigued by the smoke signal hypothesis! It’s certainly the most humble of them all; given the fact that humanity’s development has been one humbling realization after another, it would seem to fit the trend.

    Relying on radio transmission to communicate across the interstellar divide would be just about as inadequate as sending smoke signals across an ocean. We will undoubtably find radio too cumbersome by the time we visit the moons of Jupiter, let alone should we become a true spacefaring civilization. Perhaps civilizations emit only a centuries-long ‘flash’ of radio signals before moving onto some unimagined mode of communication; this idea parallels the “march toward self-destruction” hypothesis, except it replaces the end of civilization with nothing more than the end of radio transmissions. I find the latter to be at least as possible as the former, particularly when one considers the potential for faster means of communication already being hinted at by quantum entanglement.

  • David Ellis

    Actually, I think you’ve gotten Fermi’s Paradox a bit wrong. Though the Fermi Paradox and the Drake Equation are related issues and are often discussed together they aren’t the same thing. Unlike the Drake equation, Fermi Paradox isnt so much about how many civilizations are out there(one can plug reasonable numbers into the Drake equation that yield no other civilizations in our galaxy—and neatly solving Fermi’s Paradox in the process).

    Rather, Fermi’s Paradox is about the question of how long it would take for even one interstellar civilization to have colonized the entire galaxy once it has the technology to do so. He figured, even assuming very slow interstellar travel times and a thousand years or more before each newly colonized system was sending out vessels of its own that it would take, at most, a few tens or hundreds of millions of years for the entire galaxy to be filled by a single species.

    And so, since a few hundred million years is just an eyeblink on astronomical timescales, if there is even a single other intelligent species in our galaxy he asked “why arent they already here”?

  • David Ellis

    Actually, I think you’ve gotten Fermi’s Paradox a bit wrong. Though the Fermi Paradox and the Drake Equation are related issues and are often discussed together they aren’t the same thing. Unlike the Drake equation, Fermi Paradox isnt so much about how many civilizations are out there(one can plug reasonable numbers into the Drake equation that yield no other civilizations in our galaxy—and neatly solving Fermi’s Paradox in the process).

    Rather, Fermi’s Paradox is about the question of how long it would take for even one interstellar civilization to have colonized the entire galaxy once it has the technology to do so. He figured, even assuming very slow interstellar travel times and a thousand years or more before each newly colonized system was sending out vessels of its own that it would take, at most, a few tens or hundreds of millions of years for the entire galaxy to be filled by a single species.

    And so, since a few hundred million years is just an eyeblink on astronomical timescales, if there is even a single other intelligent species in our galaxy he asked “why arent they already here”?

  • David Ellis

    To me, one of the most interesting versions of the Fermi Paradox involves Von Neumann Probes.

    A von neuman probe is, according to wikipedia, “a self-replicating spacecraft designed to investigate its target system and transmit information about it back to its system of origin”. The probe manufactures copies of itself using material found in the new star system and then sends them out to both explore the new solar system and others to move outward to other solar systems in a relentless wave of exploration—sending data back to its creators all the while. It does not seem unreasonable that a species only a few hundred years more advanced than us in technology would be able to send out von neumann probes.

    This seems a likely way to explore the galaxy at minimal expense. And, even assuming the probes have a very slow speed for an interstellar vessel (less than one percent of light speed) there would be von neumann probes in every star system in the galaxy in what is, on a cosmic timescale, a very short time.

  • David Ellis

    To me, one of the most interesting versions of the Fermi Paradox involves Von Neumann Probes.

    A von neuman probe is, according to wikipedia, “a self-replicating spacecraft designed to investigate its target system and transmit information about it back to its system of origin”. The probe manufactures copies of itself using material found in the new star system and then sends them out to both explore the new solar system and others to move outward to other solar systems in a relentless wave of exploration—sending data back to its creators all the while. It does not seem unreasonable that a species only a few hundred years more advanced than us in technology would be able to send out von neumann probes.

    This seems a likely way to explore the galaxy at minimal expense. And, even assuming the probes have a very slow speed for an interstellar vessel (less than one percent of light speed) there would be von neumann probes in every star system in the galaxy in what is, on a cosmic timescale, a very short time.

  • mithraman

    Well, if there’s no aliens I guess there must be something wrong with the equation. I’m too busy to worry about that these days anyway. Like for instance, I’ve got to get rid of some large pod-like objects that mysteriously appeared in my cellar.

  • mithraman

    Well, if there’s no aliens I guess there must be something wrong with the equation. I’m too busy to worry about that these days anyway. Like for instance, I’ve got to get rid of some large pod-like objects that mysteriously appeared in my cellar.

  • tommy

    In my opinion I feel it is a mix of our distance from the galactic center (where there are much older star systems and possibly older and more advanced civilizations) and probably our current ignorance in more advanced forms of communication. Most of our science is still extremely new and I feel it has a long way to go before we could hope to pick up a signal from an advanced civilization.

  • Alex Weaver

    Given that the speed of light, and hence radio waves, is finite, it’s entirely possible that they simply haven’t gotten here yet. How wide is the galaxy again?

  • Alex Weaver

    Given that the speed of light, and hence radio waves, is finite, it’s entirely possible that they simply haven’t gotten here yet. How wide is the galaxy again?

  • http://patwhalenaustin.rr.com Pat Whalen

    I wouldn’t rule out “we are one of the first”.

    The universe is about 15 billion years old. For much of that time it couldn’t have supported life as we know it. Initially it was pure plasma, then hydrogen developed. Then stars formed from the hydrogen, some of which eventually went super nova producing heavier elements.

    Our own solar system is about five billion years old, a third of the time the universe has existed. In that 5 billion years it seems life developed about as fast as it could have. So considering all that it is not impossible that we are one of the first.

    The other question is how motivated are we to explore other stars? When the European’s set out to explore there was a perceived economic benefit. With any imaginable technology there is no economic benefit from exploring near by stars. Also without a vast increase in life span (which may or may not be possible) explorers traveling to these stars would never live to arrive. It would certainly take the shine off of being a great explorer if your only descendants will finally reach the destination.

  • Jeff T.

    I also recommend reading _Rare Earth_. Not only does this book go into good detail explaining Permi’s Paradox, it goes even further by predicting that our species will probably not create Starfleet Academy (obviously in a much more academic vein manner)—

    My own belief is that our lifespans are much to short to allow for space exploration/colonization and that we as a race will live and die on this planet. At least I lived on it before it was totally ruined by idiots and religious zealots. I guess I can thank the FSM for being so kind to me.

  • Jeff T.

    I also recommend reading _Rare Earth_. Not only does this book go into good detail explaining Permi’s Paradox, it goes even further by predicting that our species will probably not create Starfleet Academy (obviously in a much more academic vein manner)—

    My own belief is that our lifespans are much to short to allow for space exploration/colonization and that we as a race will live and die on this planet. At least I lived on it before it was totally ruined by idiots and religious zealots. I guess I can thank the FSM for being so kind to me.

  • http://none John Nernoff III M.D.

    The other consideration is aiming at the right point if you are intent on finding other “intelligent” “life.” Given a civilization wanting to reach out, if it were on the other side of our galaxy, there would be some 200 billion stars to choose as targets. Each one would require many millions of light years of communication time. I just don’t see any entity being facile enough to pick our solar system as a worthy goal. Moreover what’s “intelligent” really mean? Maybe the dinosaurs (extant for a large factor of time compared to the paltry existence of humans)were somehow intelligent and used long obliterated means of communication with extra-terrestrials. What’s “life”? It’s hard to formulate a comprehensive defintition of it. Maybe, out there, there is “kife” or “prife” — some weird (to us) combination of molecules and forces with can “study” us or other objects in the universe, of which activity we could never be aware since we wouldn’t know where to look for such phenomena. There’s just too much distance, too much time and too many combinations of forces and matter to make clear exactly what we are dealing with in our speculations and trials to detect what’s out there.

  • Jim Baerg

    Re: tommy’s comment about distance from galactic center.

    The galactic center is actually a rather hostile place for life. Out here is the galactic boondocks we can expect stars to exist for billions of years without close approaches that would disrupt planetary orbits. In the more crowded reaches of the galactic center a potentially life bearing planet would be likely to have its orbit changed to something that goes to close or far from its star by a close passage of another star, in the billions of years it would take for complex life to develop.

    Going a lot farther out the concentration of elements heavier than helium goes down so in the galactic fringes, planets large enought to hold atmospheres get less likely.

    IIRC these points were covered in _Rare Earth_

  • http://www.anexerciseinfutility.blogspot.com Tommykey

    Very interesting post. I like discussions like these.

    Another possibility is what I would call the “Maybe They Don’t Give a Crap” hypothesis. That is, there could be intelligent life on another planet in our galaxy capable of interstellar travel but they decided it wasn’t worth it and gave it up.

    My analogy for that from human history would be China under the Ming Dynasty in the early 15th century. A fleet of Chinese treasure junks embarked on several expeditions throughout the Indian Ocean, one reaching as far as the east coast of Africa. But after the last voyage in 1433, the ships were destroyed and no more voyages were permitted. For various reasons, the Ming court decided the voyages were too expensive and lacked any practical value.

  • http://superhappyjen.blogspot.com superhappyjen

    And once life exists, intelligence seems like a fairly obvious adaptation

    It seems, but then why aren’t there more intelligent races on our own planet? Intelligence is a good trick, but that doesn’t mean it HAS to evolve.

  • Jim Baerg

    Hi Tommykey:

    The trouble with the “Don’t Give a Crap” Hypothesis is that if there is only one exception the whole galaxy still gets settled.
    The Ming Chinese retreated from sea voyaging, but then a few Portuguese & Spaniards started long distance ocean trips & then other Europeans imitated them. The fact that one culture abandoned sea voyaging didn’t make other cultures do the same.

  • http://infidel753.blogspot.com Infidel753

    I’ve read Rare Earth and found it highly convincing. It’s a must-read for anyone interested in this subject. Our solar system is a freak case in certain respects which are relevant to the development of multicellular life.

    I think the truth is to be found in an elaboration of what you call the “we came first” hypothesis. Technological progress is much faster than biological evolution, and is continually accelerating. Assuming that the problem of the speed-of-light limit can be overcome, it seems plausible that the first technological civilization to appear will spread out and fully “colonize” (or exploit in whatever way is relevant to its technological level) the galaxy in which it developed, or even the entire universe, in less time than it takes for the second technological civilization to appear. This will pre-empt the development of any other such civilizations, just as the spread of humanity over the entire Earth has already pre-empted the evolution of any other similarly-intelligent species.

    If this view of things is correct, then we must be the first technological civilization in the universe. If we hadn’t been the first, we wouldn’t exist at all, because whichever civilization was first would have taken over Earth (along with the rest of the universe), probably hundreds of millions of years ago, and pre-empted our evolution.

  • RiddleOfSteel

    Infidel753 wrote:
    If this view of things is correct, then we must be the first technological civilization in the universe. If we hadn’t been the first, we wouldn’t exist at all, because whichever civilization was first would have taken over Earth (along with the rest of the universe), probably hundreds of millions of years ago, and pre-empted our evolution.

    That’s an interesting idea. Something to consider though, is once a given civilization reaches the capability of interstellar travel to encounter other life forms, the members of that civilization may no longer be governed by a quest for material gain, procreation, or other notions of conquest or base emotion that we currently view as common. So it could be the case that even now, an alien civilization has already “spread out” across parts of the universe, but maybe it’s members have attained a level of wisdom and knowledge that they do not interfere with us, or maybe don’t care much about us one way or the other. Actually if they have wisdom, maybe the aliens should wipe us out while they can:)

    If I had to read our future, I see humans in our current state as a kind of intermediate form. I think machines will eventually take over. We will have in effect made our replacements. Kind of like impotent gods, we may be just a footnote in history. I don’t necessarily envision conflict as portrayed in the Terminator movies, where humans are engaged in a battle for survival against machines. Rather intelligent machines will go out and explore the universe – similar to how machines already do this for us. Humans are just too weak and ill suited for space travel. And we die. I think it would be some kind of machine, possibly fused with some remnant of humanity, that would achieve the ability to move across the universe and encounter other civilizations or developing live forms. Hence my earlier suggestion that a civilization which has attained the capability to move across the universe may not have the motivation to disrupt or destroy, or instill it’s matrix on other forms of life.

  • RiddleOfSteel

    Infidel753 wrote:
    If this view of things is correct, then we must be the first technological civilization in the universe. If we hadn’t been the first, we wouldn’t exist at all, because whichever civilization was first would have taken over Earth (along with the rest of the universe), probably hundreds of millions of years ago, and pre-empted our evolution.

    That’s an interesting idea. Something to consider though, is once a given civilization reaches the capability of interstellar travel to encounter other life forms, the members of that civilization may no longer be governed by a quest for material gain, procreation, or other notions of conquest or base emotion that we currently view as common. So it could be the case that even now, an alien civilization has already “spread out” across parts of the universe, but maybe it’s members have attained a level of wisdom and knowledge that they do not interfere with us, or maybe don’t care much about us one way or the other. Actually if they have wisdom, maybe the aliens should wipe us out while they can:)

    If I had to read our future, I see humans in our current state as a kind of intermediate form. I think machines will eventually take over. We will have in effect made our replacements. Kind of like impotent gods, we may be just a footnote in history. I don’t necessarily envision conflict as portrayed in the Terminator movies, where humans are engaged in a battle for survival against machines. Rather intelligent machines will go out and explore the universe – similar to how machines already do this for us. Humans are just too weak and ill suited for space travel. And we die. I think it would be some kind of machine, possibly fused with some remnant of humanity, that would achieve the ability to move across the universe and encounter other civilizations or developing live forms. Hence my earlier suggestion that a civilization which has attained the capability to move across the universe may not have the motivation to disrupt or destroy, or instill it’s matrix on other forms of life.

  • http://anexerciseinfutility.blogspot.com Tommykey

    Thanks for your comments Jim.

    Well, then maybe humans will be the equivalents of the Portuguese, while the aliens on Planet X somewhere end up being surpassed by us.

  • http://anexerciseinfutility.blogspot.com Tommykey

    Thanks for your comments Jim.

    Well, then maybe humans will be the equivalents of the Portuguese, while the aliens on Planet X somewhere end up being surpassed by us.

  • http://elliptica.blogspot.com Lynet

    It seems to me that the hardest factor in the Drake equation to put a figure to is the question of how often life will evolve if conditions allow it. Abiogenesis is so badly understood at the moment that I would have thought it would be impossible to tell. So surely another possibility is that there are fewer alien life forms than we think because life just happens to be very unlikely?

  • http://elliptica.blogspot.com Lynet

    It seems to me that the hardest factor in the Drake equation to put a figure to is the question of how often life will evolve if conditions allow it. Abiogenesis is so badly understood at the moment that I would have thought it would be impossible to tell. So surely another possibility is that there are fewer alien life forms than we think because life just happens to be very unlikely?

  • http://badnewsbible.blogspot.com XanderG

    Though I feel you are right about the sudden appearance of life indicating a high possiblity of life in the universe, I feel that intelligent life will be far less common. Life appeared roughly 4,000 million years ago, but modern humans did not appear until 100,000 years ago, and civilisation did not appear until around 10,000 years ago.

    You can see there is a massive gap where there is no ‘intelligent’ life. It also seems that are civilisation rests upon the brief stable climate and only within this window of stable temperatures could an agricultural revolution take place, and civilization begin. Of course different types of civilizations could form on other planets, but I think there are a lot of obstacles to the development of an advanced species that can communicate across the universe or galaxy.

  • http://badnewsbible.blogspot.com XanderG

    Though I feel you are right about the sudden appearance of life indicating a high possiblity of life in the universe, I feel that intelligent life will be far less common. Life appeared roughly 4,000 million years ago, but modern humans did not appear until 100,000 years ago, and civilisation did not appear until around 10,000 years ago.

    You can see there is a massive gap where there is no ‘intelligent’ life. It also seems that are civilisation rests upon the brief stable climate and only within this window of stable temperatures could an agricultural revolution take place, and civilization begin. Of course different types of civilizations could form on other planets, but I think there are a lot of obstacles to the development of an advanced species that can communicate across the universe or galaxy.

  • Jim

    I can’t help but think of a bit of wisdom from Calvin and Hobbes. “I think the surest sign that intelligent life exists in the universe is that none of it has tried to contact us yet”

  • http://www.anexerciseinfutility.blogspot.com Tommykey

    The geography and climate on other planets capable of supporting life is an important factor too. A planet might have higher forms of marine life, but if it has only a few small land areas instead of the continents we have, then the conditions will not exist for land based life forms capable of evolving into intelligent beings capable of space flight. Also, does the planet possess the necessary raw materials in abundance?

  • http://www.anexerciseinfutility.blogspot.com Tommykey

    The geography and climate on other planets capable of supporting life is an important factor too. A planet might have higher forms of marine life, but if it has only a few small land areas instead of the continents we have, then the conditions will not exist for land based life forms capable of evolving into intelligent beings capable of space flight. Also, does the planet possess the necessary raw materials in abundance?

  • aweb

    It’s important to remember that projects like SETI aren’t loooking for intentional signals meant to communicate with other planets, they’re looking for anything that looks to be “unnatural”. On Earth, we have been transmitting radio signals to outer space for more than a century, and the first ones would be, I imagine, almost undetectable once in space. There’s no reason to think any planetary civilization would be spending time sending intentional signals all over the galaxy. If we ever hear anything, it definitely won’t be aninterplanetary hello.

    Also, it seems unlikely that the “light-speed problem” will ever be solved, which makes the whole colonization problem pretty insurmountable. Hundreds of years in hostile environments where if anything goes wrong, everyone dies (i.e., a space flight to a nearby planet)? Humans can’t even muster up the enthusiasm for a 2 year trip to Mars. Exploring space with space probes seems like the only possible way to proceed, and even then, the timescales are such that there are no short-term gains. And engineering a probe that can harvest raw materials and self-replicate? That seems apocalyptically dangerous, even if it may be plausible to imagine. Maybe the “dark matter” providing so much gravity for the universe is a self-replicating probe gone horribly wrong.

  • http://grendelkhan.livejournal.com grendelkhan

    There’s also the “babe in the woods” hypothesis, where “noisy”–emitting a great deal of EM radiation–civilizations are quickly dispatched by Von Neumann machines set in motion aeons ago by extremely xenophobic aliens. See Greg Bear’s The Forge of God for a good example.

    And, of course, there’s the hypothesis that intelligent life may be relatively common, but that it invariably causes its own extinction, whether by nuclear holocaust, by nanotech gray goo, or by some other technological catastrophe which has to do with a device which we’ve yet to envision.

    These are more like interesting plot devices for SF stories than serious hypotheses, but they sure are fun to ponder.

  • Chas

    I would like to make an analogy. When we were babies we were not even aware of our own body parts let alone of the ENTIRE universe that existed. We have not even explored many parts of the earth let alone the universe. What are we thinking. Do you really think that an advanced culture would use radio waves to communicate??? PLEAZEEE. Let’s not give ourselves so much credit. We don’t know jack. My guess is that there are thousands of advanced civilizations out there. We just don’t know how to receive the information yet.

    Plus, do we even WANT to know. We can not even get along with our own species. What makes us think that bringing in a new one with much more advanced technologies is going to make it better??? I HOPE we don’t find other civilizations with technologies that we don’t understand. We can not control what we have now. Lets learn to observe before we start running toward a path we don’t know it leads to.

  • Caos de le Mente

    Perhaps there is another solution…one that we may think about and but few will openly ponder. Simply, we are alone (see the book “50 Answers to Fermi’s Paradox”). That being said, what does this mean? Perhaps there is a Creator…as Martin Reese said in his book “Just 6 Numbers”, it is as though this universe was designed to support Human life. We may dance around the issue of a Supreme Being creating life, but this appears to be a huge piece of evidence to support that idea. Simply, given the age of our galaxy, the relatively young age of our sun, and the alledged ease that life can evolve, we should have seen plenty of evidence of life – including intellegent life – somewhere. Not all civilizations on our planet are pacifist, non-expansionist, and homebody enough not to thrust thier civilizations into new lands and worlds. Even the simplist of life forms do this. Extrapolated on a cosmological scale, if life is common, and intellegence is a natural by-product of evolution, they should be everywhere. Thier not because they don’t exist…period. That is a profound thought. Why? Because if we are alone, without a Creator to guide us we are doomed. We have proven horrible stewards of our world. I firmly believe that Enrico Fermi hit on the ultimate answer to the idea of Creator – we are unique because it was willed, we were created – and for a purpose.

  • bassmanpete

    it is as though this universe was designed to support Human life.

    Typical human arrogance! There are plenty of other life forms on the planet and most of them have been around a lot longer than we have. Also, apart from this ‘Pale Blue Dot’, the rest of the Universe doesn’t appear to be very conducive to humans or anything else without some form of life support system.

  • bassmanpete

    it is as though this universe was designed to support Human life.

    Typical human arrogance! There are plenty of other life forms on the planet and most of them have been around a lot longer than we have. Also, apart from this ‘Pale Blue Dot’, the rest of the Universe doesn’t appear to be very conducive to humans or anything else without some form of life support system.

  • Andrew Foster

    For those of you that want a counterargument to the ideas proposed in Rare Earth, you may want to peruse Evolving The Alien by Jack Cohen and Ian Stewart(Cohen is a reproductive biologist and Stewart a mathematician) .The Rare Earth hypothesis gets something of a good beating in this book and I found Cohen and Stewart’s further ideas on alien intelligences very interesting.

  • Andrew Foster

    For those of you that want a counterargument to the ideas proposed in Rare Earth, you may want to peruse Evolving The Alien by Jack Cohen and Ian Stewart(Cohen is a reproductive biologist and Stewart a mathematician) .The Rare Earth hypothesis gets something of a good beating in this book and I found Cohen and Stewart’s further ideas on alien intelligences very interesting.

  • http://verwide.net/blog/ Moody834

    My guess? Vorlons and Shadows. Or Xeelee… Yeah, definitely Xeelee.

    Seriously, FWIW, it seems likely to me that we are “among the first”. It makes us special, but not in a really rewarding way that would support any egotism about it; it was a crap shoot, blind ‘luck’, — so what? In the end, it does not seem likely that we’ll be around to see the eventual swelling up of our sol, because even if our descendants are around they won’t be us (though whoever is around will certainly have want of the ability to get off the earth, eh?). The insular Chinese (mentioned in other comments above) would probably have started exploring again — and with great gusto — had their known world looked to become inhospitable to life.


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