Where is Everybody? (Part II)

“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb

It’s one of the biggest conundrums in the Universe, known as the Fermi Paradox: if the Universe is so conducive to life, and if there are so many opportunities for it within our galaxy alone, why isn’t there any evidence (outside of the History Channel) of extraterrestrial life?

Image credit: Peter Essick, via National Geographic.

Image credit: Peter Essick, via National Geographic.

Moreover, why haven’t we been visited by some extraterrestrial intelligence? After all, given the fact that our Universe is nearly 14 billion years old, while our galaxy itself is only a hundred-thousand light years from end-to-end, shouldn’t all of the potentially habitable planets have been visited, and colonized, by now?

A couple of years ago, I went through the estimates — both conservatively and liberally — of how rare or common intelligent life in the Universe is. But what I wanted to focus on, today, are the difficulties in even intelligently speaking about this question. First off, let’s start with the good news.

Image credit: Justine of http://justinedoublelungs.blogspot.com/.

Image credit: Justine of http://justinedoublelungs.blogspot.com/.

The good news is, we’re here. That means we have at least one example in the Universe where things worked out in favor of intelligent life. As far as we can tell, this means the following things have happened:

  • A star was born with a planet that orbits it at the right distance for it to be potentially habitable.
  • That planet had the right mix of elements on it — particularly carbon, nitrogen, oxygen, hydrogen and phosphorus — in order to create life-as-we-know-it.
  • Life actually begun, at some point. This means, at the very least, a self-replicating complex molecule encoded with information that isn’t necessarily fixed from one iteration to the next, found a way to replicate itself. (The “information-encoded” clause distinguishes DNA/RNA-based life from, say, a non-living crystal.)
  • Life succeeded for a long enough time that it evolved not only beyond this simple, primitive state, but into complex, multi-cellular, highly differentiated organisms.
  • At least one of these organisms developed what we consider “intelligence” to be, and used it to learn about — and in some ways, master and manipulate — their environment.
  • Eventually, before going extinct, these organisms — and it’s the great hope our our civilization — managed to leave their own world, and set out to explore, and possibly colonize and/or inhabit some of the other ones in our galaxy.

Now, there’s no doubt that all but the last step, above, has already happened here on Earth. And there are huge contingents of our society striving to achieve that last one, which — despite everything — I’m still extremely optimistic about our chances of successfully accomplishing.

Illustration credit: NASA.

Illustration credit: NASA.

But the big question is this: how common should this occurrence actually be? Should there really be tens-of-thousands of civilizations just like (or even more advanced than) us out there right now, in our galaxy alone? Or are we the only ones like us, in the entire history of the observable Universe, who’ve ever existed?

Of course, we don’t know. But the fact of the matter is this: we have no right to expect that just because it happened once, here, that any of these steps are at all common!

Thankfully, we do have some evidence to tell us that some of the things that happened are, in fact, common.

Image credit: Wally Pacholka, via National Geographic.

Image credit: Wally Pacholka, via National Geographic.

The stars, for example. We know there are somewhere between about 200 billion and 400 billion stars in our galaxy. The vast majority of them — about 95% — live as long or longer than our Sun, meaning that they do have, at least potentially, plenty of time for evolution to take place.

We’ve also measured the metallicity of these stars, or how abundant heavy elements (i.e., not Hydrogen or Helium) are, and we find that our Sun is pretty run-of-the-mill. In other words, the heavy elements that we need for life on Earth are common and abundant all throughout our galaxy. In fact, the largest star thus far discovered in our galaxy, VY Canis Majoris (below), was found to have all the atoms and molecules — including phosphorous — in the outermost layers of its atmosphere!

Image credit: NASA / ESA und R. Humphreys (University of Minnesota).

Image credit: NASA / ESA und R. Humphreys (University of Minnesota).

And we’ve also learned, through our exoplanet hunts, that perhaps as many as 20% of the stars in our galaxy have planets within their habitable zones.

In other words, we’re quite confident that, within our galaxy alone, there are literally billions of stars with rocky planets orbiting at the right distance for life to exist, and they’re loaded up with the right kinds and amounts of elements to possibly give rise to life.

Which is amazing! But, it’s not everything. For example, we don’t know how hard it is for life to actually begin. We’d like to think that it’s easy — after all, the laws of physics and chemistry are the same everywhere in the Universe — so that life would exist in many different places. But it’s possible that to take that leap — from non-life to life — is actually an extraordinarily rare process.

The fact that life appeared at least 3.8 billion years ago on Earth is the only evidence we have, at this point, of life existing anywhere in the Universe. While we don’t think the conditions on Earth were all that rare or special, it is possible that the emergence of life here was rare and special. We’ll continue to search for life on Earth that doesn’t share a universal common ancestor with other known forms of life (because evidence that it happened here twice independently would be amazing), and for life — both past and present — on other worlds, as well as continuing to make life-from-non-life in the lab. But until we succeed somewhere, we won’t have any real quantitative idea of how rare or common life in the Universe actually is.

Image credit: © 2002, ReefNews, Inc.

Image credit: © 2002, ReefNews, Inc.

The development part is another great unknown. For nearly 3 billion years, life on Earth was no more complex than single-celled, asexually reproducing organisms. Yes, this includes some extraordinary one-celled creatures, like corals and sponges, but still single-celled organisms, nonetheless. But at some point, evolution permitted complex, highly differentiated, multicellular animals to arise.

Is that a commonplace occurrence in the Universe? Or is that an extraordinary rarity? Again, we have no quantitative information except this one instance here on Earth. Until we do, we’re really just playing a guess-timation game.

Image credit: Leonard Eisenberg, 2008.

Image credit: Leonard Eisenberg, 2008.

Finally, here we are! The most intelligent species — as far as we know — ever to exist! Even given the existence of life and the evolution of highly complex, highly differentiated creatures, how likely or rare is the evolution of a human-level of intelligence? Our brain-to-body-size ratio dwarfs that of our nearest competitor, the dolphin, by nearly a factor of two, and the next-nearest great ape by a factor of about three. A chimpanzee society might not have the intelligence to understand or explore the Universe, but we certainly are capable!

How rare is this level of intelligence? As far as we know, we’re the only species to attain it in the history of Earth, and we have no idea how common this is in the Universe. It could be extremely common, or we could be the only ones.

Image credit: Wikimedia Commons / Lucianomendez.

Image credit: Wikimedia Commons / Lucianomendez.

And finally, what about spacefaring civilizations? What about the colonization of other worlds? The fact that we haven’t either contacted or been contacted by another species very likely tells us that all of these things haven’t happened abundantly in our galaxy, but how rare or common is it?

The evidence, at this point, points to, at best, not that common. (And, at worst, we might be the first-and-only, and even that’s only if we can get our act together!)

Image credit: Original source unknown, retrieved from Brian Shiro at AstronautForHire.

Image credit: Original source unknown, retrieved from Brian Shiro at Astronaut For Hire.

But the fact of the matter is, I’ve never thought of the Fermi paradox as very much of a paradox. It’s not at all hard to imagine that the answer to, “Where is everybody?” is that there isn’t anybody else.

But there could be, and so we have to look. Either way, what is here is remarkable, and I want to know everything I can about it.

If the answer turns out to be that there isn’t anyone else, it’s up to humanity to change that. And if there is somebody else… well, I want to know! Don’t you?


  1. #1 Aroough
    March 29, 2013

    I really enjoy reading your posts. You are a very good teacher and I frequently find your writings nicely thought-provoking. Thanks for the work.

  2. #2 dargndorp
    March 29, 2013

    Two steps of life as we are seem highly unprobable to me, judging purely from the inordinate amount of time it took to get there – the first is the arising of multicellular life, the second being the evolution of a species that has developed sufficient intelligence to kickstart a process where cultural evolution outpaces biological evolution.

  3. #3 Wow
    March 29, 2013

    Well, yes.

    less likely but so long was allowed it was bound to happen.

  4. #4 MandoZink
    Louisville, KY
    March 29, 2013

    One idea that I never see discussed is that there may certain particular conditions which highly support the chance of abiogenesis elsewhere, but are not present here. We may be extremely lucky that it eventually happened on this planet. Imagine other advanced civilizations looking at Earth and deciding it’s not very likely life would ever start here..

  5. #5 Cosmonut
    March 29, 2013

    My guess (and its just a guess), is that the two bottleneck points are:
    - Evolution of high intelligence
    - Interstellar travel

    IMO, the last one is the biggie.
    I really can’t see why a species would set out to “colonize the galaxy”. They might want to leave their planetary system if the star is in danger of dying, but that happens only very rarely.

  6. #6 Kevin
    March 29, 2013

    Seems to me one of the lessons of science is we are not special. Other than that to many unquantified variables. But you have narrowed it down to between 1 and a few million possible intelligent life forms.

  7. #7 Russell
    March 29, 2013

    Interesting issue, there are three main possibilities that are had to distinguish from at the moment, but firstly I want to point out that usually the “paradox” is phrased wrongly that gets people on the wrong foot before they even start. The correct question is “why has evolution been allowed to proceed without outside interference for a billion+ years on an ordinary planet on an ordinary star. If aliens were going to have visited earth it would probabilistically have been hundreds of millions of years ago, and we wouldn’t be here.

    A potentially strong argument against space faring life isn’t to do with difficulty, but works in reverse, just one space faring race could have colonized the entire galaxy by now, arguing against it being likely.

    Even so, here are the three main possibilities
    1. Intelligent space faring life is incredibly rare
    2. Once life gets the capability to explore, it loses the desire (e.g. cyberheaven etc)
    3. Enforced non-interference, e.g.
    http://en.wikipedia.org/wiki/Zoo_hypothesis like things where advanced life stops less advanced life from interfering with other advanced life.

    Purely statistically 2,3 seem more likely than 1, however its hard to take that too seriously

    (4. oh yes we live in a simulation, not sure that helps …)

    Going forward, measuring atmospheres of exoplanets will help a bit, if say we measure atmospheres of 10,000 potentially habitable planets and find no oxygen, then we know that is definitely a sticking point. If we find oxygen e.g. at least simple life, but not necessarily space faring, then the only way to distinguish between 2,3 is to actually explore.

    There are lots of other possible explanations put forward, ones that aren’t similar to these however are illogical or wrong because of statistical/ civilization expansion speed arguments.

  8. #8 Christopher
    March 29, 2013

    There are of course two longstanding observations…one has been mentioned already. This one, for any of a myriad set of reasons, the people out there are withholding their presence on purpose. This presupposes a pretty good singular civilizing structure in the galaxy or cosmos though.

    The second observation is actually Carl Sagan’s. The difficulty is not with life but with the self destructive tendencies of highly advanced civilizations because a balanced climb to the necessary sophistication is very difficult and civilizations tend to disappear rather quickly. The jury is certainly still out with us, but we have been in a series of brinksmanships since the nineteen-forties. In this regard the civilizations rise and fall rather quickly and can be many but still only a few at a time anywhere in the galaxy and rare elsewhere too.

    But I rather like the speculation that by the time you could actually range far afield and visit elsewhere you also outgrow all need and desire to do so. As some of our SF speculators explain, these people may be so self contained that rather like black holes, very little leaks out that indicates coherence as we might recognize it.

    Still as Seti searches, where’s all the radio?

    Or maybe it really is a conspiracy of silence by our own that keeps us struggling with this question.

  9. #9 GB
    March 30, 2013

    I don’t know that life is common (of course) but even if it is common given the distances involved I think it quite likely that we just can’t detect it.

    So there is no paradox. There is irony perhaps…it’s everywhere but we can’t ever detect it :)

  10. #10 Steve Morris
    March 30, 2013

    I can’t buy into the idea that there are alien civilizations out there but they don’t want to explore the galaxy, or they have laws that don’t allow contact with us. In billions of years, statistically someone would have said hello.

    The most plausible conclusion seems to be that we are unique or very rare. In that case, there must be something that prevents space-faring civilizations coming into existence. Either it’s something in our future or in our past.

    It could be that we are likely to self-destruct before we colonize space, but again that doesn’t seem statistically plausible. The most likely explanation for me is that the sticking point is in our past and that we have already overcome it. Looking at the evolution diagram above, it looks like life got started pretty early in Earth’s history, so that bit was easy, but then the move to complex multi-cellular life took billions of years. Perhaps that’s the step that is really difficult.

  11. #11 Alan L.
    March 30, 2013

    This solar system alone has one life supporting planet and one near miss that once had water in abundance and vulcanism to add a dynamic to the atmosphere.

    Using our solar system as a typical example, rather than as an extreme outlier, I would guess that at least 80% of F, G and K class stars could have Earth or Mars type planets with abundant water and atmospheres that could support life, even if they’re Mars or Earth sized Ganymedes tidally locked to supersized Jupiters in the life optimum zone.

    The only logical conclusion, therefore, that the really clever could permit themselves to reach within the framework of the currently accepted scientific paradigm, while at the same time avoiding what Professor Michio Kaku has described as the ‘third rail’ of science, is that:

    Interstellar travel (in a practical sense) is not now and never will be possible;

    And that, therefore:

    There is no point in speculating on other possibilities.

  12. #12 Steve Morris
    March 30, 2013

    Alan L, in 73,000 years, Voyager 1 will have travelled a distance of 4.2 light years – enough to reach the nearest star (if it was pointed in the right direction). So your conclusion that interstellar travel will never be possible is disproved by empirical evidence.

  13. #13 Wow
    March 30, 2013

    ” In billions of years, statistically someone would have said hello.”

    If you travelled to a new star every day of your life and travelled there within the same day as you left, how many stars would you visit in 1 billion years?

    And 1 billion years ago, what evidence would exist? Cyanobacteria don’t have webcams.

    In reality, to the external world, any traveller would take some years to move between the stars even if from their POV it took no time at all.

    That puts a huge crimp on how far someone can explore the universe.

  14. #14 Sinisa Lazarek
    March 30, 2013

    @ Wow
    “That puts a huge crimp on how far someone can explore the universe.”

    unless you’re Q :)

  15. #15 zeuxis
    March 30, 2013

    There are other areas of the galaxy where stars are much closer together than our region.

    If it is more common for advanced civilizations to die out than to survive, perhaps we should be looking for that rather than for an existing civilization.

    In other words, if a civilization had destroyed itself technologically, by means of nuclear radiation or some other method, wouldn’t that be an observable phenomenon from a distance? I mean, what would we need to do to see a planet or system with a radiation signature that is clearly not natural?

  16. #16 Sinisa Lazarek
    March 30, 2013

    But what if they didn’t destroy themselves by nuclear weapons. Also, nuclear radiation coming from a planet hundreds of lightyears IMO is just lost in background noise.

    next gen optical telescopes might be able to “zoom” in on planets. And second way which costs little but can maybe provide clues, again IMO is what SETI used to do.

  17. #17 Sinisa Lazarek
    March 30, 2013

    There’s something else also to note. Intelligent life, even highly intelligent life doesn’t mean industrial revolution and all that follows it. We can see examples of that in our history. Industrial revolution had all the elements to happen cca. 2000 years ago. We have records of steam machines from Alexandria. But they remained just curiosities. There just wasn’t that “eureka” moment. There are still parts of the world today that live more or less like they did 5000 – 10000 years ago. So in principal I argue that it’s very much possible to have alien civilizations that could just function fine without ever thinking of leaving their planet.

    Also very much possible, and this is much more worrying, it might as well turn out that there can’t be space exploration as we imagine it today. Am talking about relativity of course. Maybe there is no way around it. Maybe all you get is one way tripm if even that. I hope that isn’t the case, but is just as valid argument.

  18. #18 Jesters
    March 30, 2013

    after all, the laws of physics and chemistry are the same everywhere in the Universe- this statement is ridiculous. Our laws a of physics and chemistry are based upon “our” observations. We have no concept of how physics and chemistry may have been developed on other planets, or their true properties. We can only “assume” that these laws are universal based upon our experts. To blanket the entire “universe” with these rules is ridiculous and vain. If intelligent life exists out there then who are we to say that “our” science is the most complete model of the universe. We have no idea how other advanced “species” might percieve their findings and that they are the same as ours. Scientific observations are objective. We must accept this idea and not presume that we are the ” highest authority” on the subject of how the entire universe works. We are but one small entity in the universe. To assume that we are the end all, be all of science is ridiculous

  19. #19 Wow
    March 30, 2013

    “We have no concept of how physics and chemistry may have been developed on other planets”

    Yes we do.

    They are exactly the same laws of physics as ours.

    If we assume that they are different, then why the hell do stars still form and blow up like they do with the physics we know from our locality?

    If the physics can change arbitrarily, then why aren’t distant galaxies made of custard?

    The distant universe acts exactly like they obey the same laws.

    Do you have any evidence to show what the physics is like elsewhere that demonstrates it is not?

  20. #20 Steve Morris
    March 30, 2013

    “That puts a huge crimp on how far someone can explore the universe.”
    I’m not talking about someone. I’m talking about a Type III civilization.

  21. #21 Sinisa Lazarek
    March 30, 2013

    @ Steve
    “I’m talking about a Type III civilization.”

    even so, everyone is governed by same laws of nature.

  22. #22 GB
    March 30, 2013

    If every planet in the universe (except the others in our solar system) currently had life as intelligent as those lifeforms on Earth are we sure that we would be able to detect it using current technology?

  23. #23 Wow
    March 30, 2013

    If they were 500 light years away, they’d not be sending anything we’d be detecting for maybe another 400 years…

  24. #24 Wow
    March 30, 2013

    “I’m not talking about someone. I’m talking about a Type III civilization.”

    So they’d use Donner and Blitzen to give them a lift, right?

  25. #25 Alan L.
    March 30, 2013

    @ Steve Morris

    You missed the part that I’ve bolded for your benefit below:

    Interstellar travel (in a practical sense) is not now and never will be possible;

  26. #26 Bill
    March 31, 2013

    if a civilization had destroyed itself technologically, by means of nuclear radiation or some other method, wouldn’t that be an observable phenomenon from a distance?”

    Maybe we have seen it but not recognized it. I do recall reading, writing now this blog, about unexplained flash(es) in space

  27. #27 Bill
    March 31, 2013

    Sorry for the auto-correct :(

    I do recall reading, in this blog, about unexplained flash(es) in space

  28. #28 G
    March 31, 2013

    Re. Cosmonut @ #5: “I really can’t see why a species would set out to “colonize the galaxy”. They might want to leave their planetary system if the star is in danger of dying, but that happens only very rarely.”

    Rarely? Surely you jest! 100% of stars die, thus 100% of scientifically-capable intelligent land-dwelling species will realize that their stars will also die.

    The prospect of the extinction of all life on one’s home planet is a powerful and sufficient incentive for interstellar travel. If you don’t think so, go kill yourself right now. If you got offended at that suggestion, you’ve proved my point. Sorry to guinea-pig you without asking first, but the point needs to be made unequivocally, that any land-dwelling and scientifically-capable intelligent species with an individual and collective survival instinct will eventually reach the point where it desires to spread to other star systems before its home star explodes or otherwise dies.

    The bottom-line question on the cosmic Darwin test is, who actually makes it? I originally called this issue “cosmic selection” but found that term was already used by Eric Chaisson at Tufts, so I’m calling it “natural selection on the cosmic scale.”

    There is nothing about interstellar travel that violates our present scientific understandings. In theory it is not impossible to construct a colony ship sufficient to support a genetically viable population of Earth life over a many-generational voyage at relatively slow speeds, e.g. a small single-digit percentage of c.

    The problems are technical: 1) Reliable means of propulsion that will function for perhaps thousands of years. 2) Reliable means of life-support that will do likewise. 3) Accurate means of assessing the likelihood of deadly microbes on any planet found suitable for colonization. 4) Means of constructing habitats and life-support infrastructure on a new planet. Assuming we don’t darwinize ourselves via climate change or a missed meteorite or biological warfare (nukes are passe: bugs are the real deal), we have more than sufficient time to experiment until we have solutions to all four of those issues.

    There is another critical issue, 5) whether we can curb our instinctual drives toward reckless reproduction, conspicuous consumption, domination of others, and desire for emotional drama, sufficiently for the colony ship to survive the journey. This is the issue of social evolution. Bluntly, we must evolve socially or we will become one more of many failed species.

    As for why we haven’t run into the mythical Grays as they take the inevitable similar steps out of their home system and to other stars: how easy would it be for us to detect objects of the type I just described, as they streak through our galaxy? Not so easy, no, not at all. And who says the Grays, or the Greens, Blues, and Purples, use the same means of communication that we use? For while science is uniform throughout the universe, technology is most likely diverse. And we don’t have the last word on the science either, as new developments in physics may lead to new means of communication.

    Re. Jesters at #18: I see that Wow put that nonsense to rest in the subsequent post, but I’ll stick my neck out and give the nonsense a name: pseudoscientific post-modernist bullsh–. And I’ll go just a little further:

    Envision this. The children of every scientifically-capable and land-dwelling intelligent species throughout our galaxy, and throughout the entire universe, learn the very same laws of classical physics as Earthlings learn. When you sat in that classroom in secondary school and learned that material, you participated in a ritual that is truly universal. Every similar species must necessarily discover the laws of classical physics in order to make technological progress beyond a crude level. Whether they go on from there in the same sequence that we have, with Einsteinian relativity coming next, and the quantum theory coming thereafter, is anybody’s guess. Perhaps some civilizations go straight from their Newton to their equivalent of someone who has yet to be born on Earth, whose theories may substantially change our own paradigms.

    But they all had their Newton, singular or plural.

    And personally, I find that deeply meaningful, aesthetically beautiful, and very much exciting.

  29. #29 Wow
    March 31, 2013

    “Rarely? Surely you jest! 100% of stars die, thus 100% of scientifically-capable intelligent land-dwelling species will realize that their stars will also die.”

    About every 10 billion years.

    I’d call that a rare event, seeing as something I do less than once a year would be called “rare”.

  30. #30 Wow
    March 31, 2013

    The need to colonise expands with the rate of population needs and the rate of a species once it reaches a high level of self determination is not much more than replacement, except for very new colonists.

    Taking 100 years to get to a nearby useful planet without genocide of its current inhabitants means the expansion doesn’t go very fast.

    Unless what you want to do IS basically expand and use up every resource as Agent Smith attributed to a virus. And humans.

    But if they were to do that, then the War of the Worlds type invasion is inevitable and we can’t do a damn thing.

    Which would work for them until they found a race with the same idea and goals and the technology to act on them.

  31. #31 G
    March 31, 2013

    Re. Wow at #29: If I’m not mistaken, we have about 2-1/2 billion years to go, not ten billion, before our Sun goes red giant, and between now and then it will expand to the point where the oceans boil.

    Eventually each of us will die (and the “upload your mind to a computer” meme is just another form of reincarnation belief, personally I’d rather come back as a cat).

    If you expected to die within the year, would you call that “a rare event” or would you seek to prolong your life? “Later” is “now,” just a little further away on the time dimension. Every “later” inevitably becomes a “now.”

    If the Sun were going to blow next week, and the mythical Grays landed a spaceship in your back yard tomorrow, would you ask them to take you as a passenger, or would you stick around and endure a death that was probably horrifically cruel?

    There is no escaping this, not at all: every land-dwelling species that is scientifically capable and has an individual and collective survival instinct, will eventually confront this issue and seek to go to the stars as an alternative to extinction.

    This also leads to the moral imperative that we, here and now, take such steps as are needed to preserve the right of our distant descendants to choose their outcome for themselves. We do not have a right to squander resources and crash ecosystems and revert humanity to a state from which space travel becomes impossible due to lack of concentrated energy sources or raw materials. We are obligated to give our distant descendants the capacity to pass the cosmic Darwin test. Operationally this translates to living sustainably, supporting progress in science and technology, supporting universal science education, and supporting space exploration.

    Re. Wow at #30: Yes, population growth could theoretically drive the need to colonize other planets in one’s own star system, colonize interplanetary space, and eventually go to the stars. Except for one problem. Any _rate_ of growth is exponential growth. And exponential growth eventually goes into overshoot and collapse.

    Sustainability, which necessarily includes zero population growth beyond a sustainable level, is a mandatory pre-requisite for having the resource surpluses needed to muster the technology to go interplanetary and interstellar.

    The other two prerequisites for going interplanetary and eventually interstellar are b) an absence of regional and global warfare for the length of time needed to complete the task, and c) a society that recognizes and protects the right to freedom of scientific inquiry.

    Those three things will also prove to be universal. Any civilization that manages to go interstellar will necessarily have achieved sustainability, peace, and freedom of scientific inquiry, as the prerequisites for that stage of development. This does not mean that the mythic Grays or Blues or Purples will be benign, only that they cannot be malevolent in ways that preclude those three conditions.

    Know what I find really frustrating? All the “no we can’t, no we won’t, no we shouldn’t” arguements against space exploration and migration, that typically come from the obscurantist anti-science crowd. I can’t help but envision them sitting around the campfire in ancient Africa, telling their fellow tribemates that it really isn’t worthwhile, good, or necessary for any of them to migrate beyond the mountains and the seas. You can see where that would have gotten us by now, and, plus one decent sized meteorite, where it could have gotten us.

    BTW, in case it wasn’t clear, I’m on your side re. Jesters. ‘Twas Jesters who was engaged in “pseudoscientific postmodernist BS”, not yourself. You did a good job shooting down his hot-air balloon.

  32. #32 Wow
    March 31, 2013

    “If I’m not mistaken, we have about 2-1/2 billion years to go”

    Yeah, but that’s still pretty infrequent. There’s no huge rush to invent space travel for quite a long time. Its far more likely we’d get smacked out of existence with a space rock and end that way than the sun goes boom.

    In deep time, evolution is liable to kill us all off. Just like it did for the Allosaur.

  33. #33 Wow
    March 31, 2013

    “Any _rate_ of growth is exponential growth.”

    Replacement isn’t. And much of the world is trying to stop exponential growth. And it’s likely not to change either, if we’d managed to produce space colonies. There’s better things to do than bring up babies continuously.

  34. #34 G.
    California USA
    March 31, 2013

    Re. Wow at #32:

    A spacefaring civilization can take steps to protect itself from space rocks: this problem can be solved entirely from within present science and technology, all it takes is the will to devote the needed resources. What we can’t protect against are supervolcanos and caldera events. (Though presumably we could maintain stored food supplies sufficient to get over the global impact on agriculture; this is a “resilience” strategy rather than a “prevention” strategy.) Beyond that, are gamma ray bursters and nearby supernovae and possibly wandering black holes, also wholly beyond our control. I take all of those as further incentives for “Mars and the stars.”

    I think your “frequent/infrequent” arguement is fundamentally mistaken. Consider a natural human death at older age, for example 70 years: that’s a 1-in-70-year event. Now consider a death during childhood, example at 7 years: that’s a 1-in-7-year event. Yet which of those two deaths do we consider the more tragic, and make the more heroic efforts against? Infant and child mortality used to be so common (more-frequent) that a high birth rate was needed to ensure replacement.

    In any case, death is a singular event for each individual, and extinction is a singular event for each species, which is the basis of my arguement that “frequency” is irrelevant. All other factors equal, you will seek to preserve your own life as long as you are conscious, and the honors accorded to altruistic self-sacrifice further make the point. Multiply that by the scale of humanity, and the drive for space migration is an inevitable conclusion. The fact that the vast majority of humans give this no thought today, is not surprising. But now that we know that space travel of any kind is possible, and we have numerous such narratives in the culture via fiction, any truly existential threat to our species will bring it back to mind each time.

    Re. #33: “Replacement isn’t” what? Isn’t exponential growth?

    That’s obvious enough, and of course any given space colony will also have sustainable population limits. There will be times and places where high birth rates are viable (e.g. in the growth phase of a colony on a new planet), and times and places where ZPG is essential (e.g. as a new planet reaches carrying capacity).

    For any given human, it’s more or less a matter of “luck” (subjective outlook on events beyond one’s control) whether they live at a time when high birth rates or low birth rates are needed. That “luck” works in both directions, as the individual preferences for having many, few, one, or no children, interact with the needs of the society on their planet during their life. And for those who wish more or fewer children than their local norms encourage, absent new methods of propulsion beyond current physics, it won’t be possible to hop a flight to a planet in another star system where one’s own preference matches the present local need.

    Though, the idea of desired family size as incentive for individuals to choose to migrate among star systems, could be interesting to work out in fiction (we can assume FTL travel as a plot device;-). Hmm…

  35. #35 Wow
    April 1, 2013

    “A spacefaring civilization can take steps to protect itself from space rocks”

    irrelevant, G, to my point.

    I was defending the extinction times. Solar extinction is a rare event to anyone who needs to survive it, even species.

    Asteroid hit is something a species may have to worry about removing them. I.e. something we ourselves have to worry about far more than the sun going boom.

    A much less rare event.

    When it comes to getting off this planet, the asteroid strike is a much more urgent reason.

  36. #36 Wow
    April 1, 2013

    “Re. #33: “Replacement isn’t” what? Isn’t exponential growth? ”


    “That’s obvious enough”

    Then you shouldn’t have claimed any replacement was exponential growth.

  37. #37 Angel Gabriel
    This conversation never happened
    April 1, 2013

    Why won’t you talk to me?
    Talk to me!


    Sorry, this conversation never happened.

  38. #38 Ryan
    St. Paul
    April 1, 2013

    I think the Drake formula is a great starting point, but there MUST be variables that are not included. For example, using the earth as a model, you can add a sufficiently sized moon, a large Jupiter-sized planet with a strong electromagneto-sphere, presence of an asteroid belt, etc. Plus, any life must not have been destroyed by a cataclysmic event. So, yes, there are BILLION of stars, but the funnel narrows quickly.

    Additionally, the goal is to find life that is functionally useful. For example, life beyond a certain distance (say 100+ light years) would likely be impossible to communicate with. Imagine how much civilization would change in the 200+ years it would take to send and receive a message! It just would not be useful.

    So, the real question is “Is there life in the universe that is close enough to have an impact on society?” The answer, unfortunately, sounds like a resounding “no” (but we should keep looking!)

  39. #39 Sean T
    April 1, 2013

    Based on our own experience, maybe we already have the answer to why other intelligent species have not gotten into contact. To reach the point where contact is possible, an advanced technology is required. Advanced technology requires an efficient energy source. Efficient energy sources have negative environmental impacts. Perhaps other civilizations either rendered their environments uninhabitable through their use of energy or they had the wisdom to realize that continued use of these energy sources would lead to their own extinction and reverted to a pre-technological existence. Either way, they would be unable to contact us.

  40. #40 Sinisa Lazarek
    April 1, 2013

    @ Sean T

    “Efficient energy sources have negative environmental impacts”
    - what would be the negative impact of cold fusion on the enviroment?

  41. #41 Wow
    April 1, 2013

    Well, apart from not being possible…

    Sodding freezing…

    Seriously, it didn’t work. Sean is talking about the venues of power production we currently have that get most attention at the moment.

    Nuclear, obvious problem, known right from the start.
    Coal, Gas and Oil have a problem we’ve really only recently (last fifty years or so) known about.

  42. #42 Keith M Ellis
    Kansas City, MO
    April 1, 2013

    In my opinion, the weakness is somewhere in the advanced-technology-to-space-travel-to-colonizing transitions. I think we have good reasons to believe that this represents an escalation of increasingly unlikely events.

    I can imagine, say, intelligent life arising and achieving space-faring technology once every twenty-thousand years somewhere in our galaxy, on average. But only a few of those will even dabble in interstellar travel. And, of those, only a few will attempt to colonize. And, of those, surely we can’t expect almost any of them to succeed over a long enough term to be noticed by another such civilization? That is, I don’t have too much trouble imaging that the Earth has been visited by aliens sometime in the last 250 million years. I do have trouble believing that there’d be any evidence of such a visit.

  43. #43 Sinisa Lazarek
    April 2, 2013

    @ Wow

    I was under the impression that Sean was talking about technologically advanced civilization (not only us). Surely we are not talking about coal powered space ships or diesel for that matter.
    And I wouldn’t call us advanced in the first place, as far as space exploration goes. I mean we invented stick and rope airplane 100 years ago.
    If we can’t even imagine other means of energy production other than fossil fuel burning then ok.. that’s our problem. But I wouldn’t call that a rule for all other planets and possible species.

  44. #44 Sinisa Lazarek
    April 2, 2013

    p.s. it might very well be that cold fusion is a dud.. it was just a first thing to pop in my head. But in general I can’t agree that an efficient energy source is by default negative on enviroment.

  45. #45 Wow
    April 2, 2013

    “I was under the impression that Sean was talking about technologically advanced civilization (not only us).”

    You missed this bit, SL:

    “Based on our own experience,…”

    It still applies to the rest of his statements in that post.

  46. #46 Sean T
    April 2, 2013

    Wow and SL,

    Precisely. We haven’t yet found any energy source that doesn’t have negative environmental impact. Maybe someday we will. However, even more generally, the hallmark of an intelligent, technologically advanced civilization is its ability to modify its environment. Perhaps such environmental modifications lead inexorably to extinction of the species unless they are able to forsee this and revert to a pre-technological state. In either case, they cannot contact us.

  47. #47 Sinisa Lazarek
    April 2, 2013

    @ Sean and Wow,

    sorry if I misunderstood you. Here is my dilemma. If we are talking about interstellar travel, there are 2 different things to address. One is power source, second is propulsion source. Those 2 needn’t be same thing. And more than likely won’t be. Even today there are many ideas on propulsion.. some theoretical, some practical.. on non thermo-chemical propulsion.

    If we are talking about power source for the planet, this again needn’t be negative for the planet. Solar power isn’t, geo-thermal, wind, tidal.. etc. Yes, most of them today are in infancy, but even today, the means are there. Now what’s wrong with an earth like planet that has strong winds i.e. Life could evolve, civilizations could evolve, but due to high winds all their power is wind based. They regard fossil fuels as inefficient. They can cause their breeze is 200km/h wind.

    Even if we stick to “today’s” means. Personally, I don’t think it will be that long (50-100 years) before we start mining asteroids. Yes, it is negative impact on asteroid field, but not for any planet or ecosystem (granted if there’s no ecosystem on asteroids).

    I of course agree that fossil fuels have negative impact, even nuclear power because of radioactivity. But those are not the only ones.

    And if we try to think what might be out there, we need to be rooted in physics, biology etc.. but we can’t be too much rooted in what exists on earth as far as fuel and how much or little there is of it.

  48. #48 Wow
    April 2, 2013

    None of those solutions for travel mean that we drop the speed limit of light, though, so rather moot with respect to the question of the thread “where is everybody?”. We have no reason to believe that they ought to be here by now.

    But the dirtiest nuclear power for interstellar travel doesn’t impact on the earth after it leaves close orbit, so the distinction isn’t germane to Sean’s contention.

    We have to have enough power to make the society independent of the necessity of work for long enough to develop interstellar travel. And we aren’t showing up intelligence as being of any damn use in making that switch without screwing things up and causing an (effective, from the Drake equation perspective) end of civilisation.

    We can hope that other intelligence won’t bollix things up so bad, but they will almost definitely go through the “burn things for energy” state and most of our improvements have been finding more efficient ways to burn things.

    Whether the institutional demand to remain on pre-stone-age technology ideas is parochial for intelligence able to civilise or whether it’s just a failing of the specific evolution of the hominid brain can be questioned.

  49. #49 Sinisa Lazarek
    April 2, 2013

    @ Wow
    “None of those solutions for travel mean that we drop the speed limit of light”

    of course not. My only comment to Sean was in regard to energy source.

    As for practical means of travel, unless we discover some new physics i.e. mach effects, negative mass (exotic particles etc.) we are looking at generation ships at best (I leave earth, my grand grand children reach the destination).

    It might well be this is the way of Universe. In that case, I see rather violent colonizations for any species. Imagine spending 4 generations in order to reach a suitable planet for colonization only to discover it’s already populated. If the species on the ship is of similar mindset as us, and they notice that the species on the planet is inferior, they won’t just say…ok we’ll move along for 4 generations more. More likely they will put them in a zoo or keep as pets and colonize the planet. From this perspective, I wouldn’t like to meet any E.T’s close to earth for a good while.

  50. #50 Wow
    April 2, 2013

    From the POV of the rest of the world, even near-light-speed travel is light speed only travel, and even though YOU get there in your lifetime, it was a one-way trip.

    It would reduce the anger a bit.

    But maybe that’s why the ID4 aliens were so cheesed off?

    It would be really expensive to lift war gear up out of your gravity well and drop it (safely) in another, so any colonists would be poorly armed and left with mostly throwing rocks as a recourse, and one that would either be ineffective at conquest or ruin the planet for use, so I’d still say that a hostile take over would require some plotnium to make happen.

    This does mean that the most likely colonisation will be to something no more than a few hundred years away by travel, few thousand tops, so that the destination will have no moral quandry living on the surface by the time you get there.

    If we do meet others, it will likely be when either we colonise other planets near someone’s home or planets near us get colonised and we are looking at mostly unlived but liveable by us planets.

    I doubt an alien civilisation will do any different. Space invaders is really expensive for the invaders and there’s a lot more utility in just not trying and moving on to the next.

  51. #51 ray
    April 2, 2013

    You state:
    For nearly 3 billion years, life on Earth was no more complex than single-celled, asexually reproducing organisms. Yes, this includes some extraordinary one-celled creatures, like corals and sponges, but still single-celled organisms, nonetheless.
    Not that it affects your story, but for accuracies sake, neither corals nor sponges are single-celled.

  52. #52 David OHara
    April 3, 2013

    The supposed paradox is easy to resolve for yourself using an excel spreadsheet. Put in the age of the universe, the number of stars. a reasonable fraction of stars that contain planets, a reasonable fraction of those that contain single celled life, a reasonable fraction that produce multicelled life, a reasonable fraction that contain complex life, a reasonable fraction that produce intelligent life etc, etc. You get a reasonable density of intelligent civilizations in the galaxy. THEN, comes the kicker. You put in a lifetime for a civilization. Considering the age of the universe, this lifetime dominates everything else in determining the average distance between civilizations. You can vary any other paramater all you want but this “civilization lifetime” dominates everything.
    The interesting question is what this “civilization lifetime” means.

  53. #53 Ted Berner
    April 3, 2013

    I might be wasting my time if Ethan doesn’t read this, but here goes…

    Why would an alien civilization, thousands or even millions more advanced use radio waves for communication? Transmitting in that way might be great for planetary use or to make a call to the moon… but for interplanetary communications, radio waves suck. It’s apparent they suck even now, to us, though it’s the best way we got to communicate.

    Why not Quantum Entanglement used for communications? If you can find a way to transmit FASTER than the speed of light, wouldn’t it be a no-brainer to capitalize on that benefit?

    If this is the case… we’re going to be listening to quasars and other cosmic static forever…

  54. #54 Richard585
    April 3, 2013

    We should be worshiping our oversized Moon and our asteroid belt with Jupiter’s closeness. I think these bodies at just the right distances fueled the fast erosion required to produce a primordal soup and periodic mass and minor extinctions allowing us to evolve. This may be why intelligent life might be a singularity in the universe.

  55. #55 Terrence Connolly
    April 3, 2013

    Great topic. A few added perspectives:

    My understanding is SETI has investigated an area within a radius of a mere 100 light years, leaving the vast balance of hundreds of thousands of light years in the Milky Way still to be explored. Just because we developed radio communications first is also no reason to expect other intelligences will do the same or still be using it. Or even that they would be remotely interested in us.

    So for all we know, there may even be many civilizations in the galaxy within their own 100 – 200 light year bubbles, just waiting to discover each other. There also may have been many such civilizations that are already in the dustbin of the galaxy’s eons, and many such in the future centuries of our galaxy.

    Our sun’s mundane location in the relative backwater of the galaxy, combined with humanity’s rather recent development is a perfectly logical reason why no else one has found us yet. If we want to be found that is…

    Most likely any other intelligence out there is at least thousands if not millions of years ahead of us in technology as well as their own evolution. Their unimaginably sophisticated technology paired with that unknown ET evolutionary history means there is no reason not to expect that they will be much longer lived than the puny century a human gets to live. Why expect then that this incredibly advanced alien species that lives for who knows how much longer than us would have any issue with dealing with the vast interstellar distances necessary for colonizing small sectors of the galaxy?

    The same thoughts for their AI technology, which is a very likely way for even ourselves to explore. Humans will send AI to the stars first, just like we are doing now on Mars.

    For all we know, the other side of our galaxy is literally teeming with ET’s, but our side of the Milky Way is much quieter for some unknown reason. If that were the case, we would most likely think we are the lone form of intelligence in the galaxy. Not to mention the billions of other galaxies. Intelligence could be common throughout our universe.

    Or not and we are alone, but I think we need to think long and hard before ruling other intelligence out.

  56. #56 George
    April 3, 2013

    Our technological civilization in the cosmological timescale is in its infancy. We as humans just started to get a sense of understanding of our solar neighborhood and the vastness of our universe. At this time any statements about intelligent life in other realms of the universe and our effort to communicate with them are speculative with our limited technology and may be even dangerous.
    The evolution of our species and all species in this planet earth has been based on the survival of the fittest. If life in other areas of the universe have followed the same path to intelligence, and are still around, most probably they developed a very unique civilization to survive and set colonies beyond their own planet.
    I hope that our own species which developed by trial and error based on the survival of the fittest develops the intelligence required to survive for a long time in this planet of ours and learns on how to travel and prosper in other worlds and under different environmental conditions.

  57. #57 Kedeus1970
    April 3, 2013

    I think one of the big variables that I never see discussed is whether life, given enough time, invariably arises out of a particular, fixed set of circumstances, or whether it instead requires specific changes to those conditions to occur in a specific order. The primordial soup argument seems to be that making life is like making toast – if you have the right materials (bread, toaster) push the button and wait long enough, voila, you have toast. But maybe life is more like chocolate cake – you need the right ingredients and conditions, added in the right order. You can’t bake and then add the eggs, or put the frosting on first. So life might require more than just a planet with conditions like earth 3.5 billion years ago; it might require a planet that had a similar history and sequence of geologic, climatic and environmental change. So while Earth-like planets may be common, Earth-like planets that have similar things happen to them in a similar order (eg, collisions with other objects, atmospheric changes, volcanic eruptions, development of a moon, etc.). If life is like chocolate cake, it might be way, way more rare than if it is like toast.

  58. #58 Kedeus1970
    April 3, 2013

    #46 Sean T – You wrote “Perhaps such environmental modifications lead inexorably to extinction of the species unless they are able to forsee this and revert to a pre-technological state.” Setting aside the irony of you typing that thought on a computer, consider that a “pre-technological state” has not averted the extinction of 99% of the species ever lived on this planet, and such a state would not save us or any other intelligent species from extinction. Technology possibly will be our undoing, but on the other hand it is our only possible means of avoiding extinction – by world hopping, at least until the entire universe dies its cold death. Without it, our time here on Earth is limited; either we will perish as the sun ages, or sooner due to some other climactic extinction event.

  59. #59 Ted Berner
    Earth, give or take
    April 3, 2013

    I’ve been tempted to quickly rule out intelligence on Earth on numerous occasions…

  60. #60 Sean T
    April 3, 2013

    Ted Berner,

    You are misinformed, as I understand it, you can’t use quantum entanglement to send faster than light messages. Entanglement just means that there is a correlation between two sets of measurements done at different and potentially widely separated locations. This correlations cannot be detected without ordinary communciation of the measurement results, so ordinary communication must still be involved to use quantum entanglement as a means of communication.

    You determine the state of a particle by measuring, but you don’t control the outcome of that measurement. That is, assuming that a message code exists, for example, in a sequence of photon helicities, it’s still not possible to send a message that way. The helicity of a photon is determined when it’s measured, but an experimenter has no control over whether a particular photon will be measured as having a left or right helicity. Thus, a non-random string of helicities is impossible. Entanglement just means that the random string of helicities measured at one location will be reproduced at another location. To see that entanglement has occurred, it is necessary to compare random strings to see that they are identical. This requires ordinary, c or slower, communication.

  61. #61 Tom Moriarty
    Colorado, USA
    April 3, 2013

    You started out this post with the quote…

    “If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb

    But I don’t think you mention that that is the title of an excellent book by Webb. In the book Webb discusses 50 possible explanations for the question. They range from “We are alone in the universe” to “They are already here among us”

    I highly recommend this book. It is on my top 10 list.

  62. #62 Wow
    April 3, 2013

    “Why would an alien civilization, thousands or even millions more advanced use radio waves for communication?”

    For the same reason we do: it travels a long way.

    “If you can find a way to transmit FASTER than the speed of light, wouldn’t it be a no-brainer to capitalize on that benefit?”

    Entangled particles, even if it could transfer FTL messages would still require that one of the particles be moved at less-than-light-speed to the place where you want to talk to.

    And once you’d used it once, for one single bit of information (whether binary or analogue), it would no longer be entangled, requiring a new particle be moved over.

    Even if it worked, it wouldn’t!

  63. #63 Ted Berner
    April 4, 2013

    Finally, the answers I was looking for. Thanks!

  64. #64 Wow
    April 4, 2013

    It’s a problem with woo-like treatments of “cutting edge” science (as in “not part of the school curriculum”) that got you, Ted.

    I.e. the way all these healing crystals use “quantum” to “explain” how they make you feel better.

    So some barnpot with some buzzword bingo list gave you a poor idea of what the science was and left you with a silly idea.

    Unfortunately, it is an idea that looks a lot like the woomancer ideas and they aren’t really here to find out science, but to promote their Google Gallileo credentials (and complain that they’re being oppressed because nobody thinks their ideas are worth a plugged nickel).

    Hence responses will tend to be abrupt and short, since effort is not rewarded.

    If you ask questions and get blunt answers that you (because you live in your own head and know why you asked, whereas everyone else has to guess) think are unwarranted, ignore the tone and look to the content.

    It saves everyone time and effort this way.

  65. #65 Name Withheld
    April 4, 2013

    Of course there is life on other planets. HOW DO YOU THINK WE GOT HERE? That’s the only way life got onto this planet – it CAME FROM ANOTHER PLANET. Your notion of “life arising from non-organic matter” was the alchemy of last century. Once you realize that life on earth came from another planet, you’ll be a step farther down the road.

  66. #66 Wow
    April 5, 2013

    So if life here came from another planet because that’s the only way, how did life get on that planet to get here?

  67. #67 Sinisa Lazarek
    April 5, 2013

    wait for it.. he’s checking ufo/ancient aliens forums for an answer to that particular question :D

  68. #68 Wow
    April 5, 2013

    Actually, I think it’s just another “All the scientists are wrong” blabbler.

  69. #69 Steve Morris
    April 5, 2013

    Reasonable assumption 1: There are many planets in the galaxy capable of supporting life, in principle.
    Reasonable assumption 2: We actually have no idea how hard it is for intelligent life to evolve on a planet.
    Reasonable assumption 3: If intelligent life evolves, it will either leave its host planet and colonize the galaxy or it will become extinct.

    Deduction: Since no galactic civilizations are observed, I conclude that either A) it is incredibly difficult for intelligent life to evolve, or B) intelligent life becomes extinct very easily.

    In other words, the Great Filter, but in case A optimistic and in case B pessimistic.

  70. #70 Wow
    April 5, 2013

    “If intelligent life evolves, it will either leave its host planet and colonize the galaxy or it will become extinct.”

    The period between “life evolves” and “leaves the planet” can be pretty damn big. The gap between leaving the planet and colonising the galaxy is even bigger.

  71. #71 Wow
    April 5, 2013

    We have at least three divergent evolution paths to intelligence here on earth. It seems intelligence is a valid path to survival as a species.

    We have evidence of some life-like forms on the earth only some million years after its formation, therefore it seems some form of life is pretty easy to manage.

    It took 4 billion years, near enough, to evolve complex macro scale life capable of supporting a species where intelligence would be a survival trait.

    So from the evidence of one, it seems all you really need is billions of years to get intelligent life. Whether any planet remains stable enough for billions of years is most likely the limiting factor for the abundance of intelligent life.

  72. #72 Steve Morris
    April 5, 2013

    wow , if your sample size is one, the error bars in how long it takes to evolve intelligent life is pretty large. If it took 4 billion years on Earth, it might take ten billion typically. Or it might take 1 billion.

    On the other hand, once intelligent life has evolved, things move much more quickly. From Stone Age to Space Age – a few thousand years. From Space Age to colonising a galaxy 100,000 light years in diameter – perhaps 100 million years at most. The migration across the galaxy is orders of magnitude faster than evolving intelligent life.

  73. #73 Wow
    April 5, 2013

    “wow , if your sample size is one, the error bars in how long it takes to evolve intelligent life is pretty large.”

    Yup, indeed it does.

    Problem for your statement is that I’ve already told you we have a sample of three.

    “If it took 4 billion years on Earth, it might take ten billion typically. Or it might take 1 billion.”

    Again, true. However, how does this support your assertion before: “A) it is incredibly difficult for intelligent life to evolve”?

    It may take a long time for it to become a viable strategy to spend so much biological effort in carting round an intelligence with the rest of the vitally necessary meatsack, but we have three examples now of high intelligence from three different branches of evolution, one of which isn’t a chordate, not even bilaterally symmetrical (which is even earlier in evolutionary history)!

    “From Stone Age to Space Age – a few thousand years.”


    “From Space Age to colonising a galaxy 100,000 light years in diameter – perhaps 100 million years at most.”

    Nope, we have ZERO evidence for that and a huge amount of evidence that this would be impossible without FTL travel, likewise nowhere in evidence.

  74. #74 Birger Johansson
    April 5, 2013

    Assuming “strong” AI supersedes organic intelligence the long travel time of interstellar travel becomes tractable.
    And since we have seen no evidence of self-replicating von Neumann machines, I must reluctantly assume we are the first technological civilisation in the Local Group, at least.

  75. #75 Wow
    April 5, 2013

    “Assuming “strong” AI supersedes organic intelligence the long travel time of interstellar travel becomes tractable.”

    Well, rather mooting the “where is everybody?” query, since the answer is “they’re traveling”.

  76. #76 Steve Morris
    April 6, 2013

    wow, we really don’t have 3 independent examples of the evolution of intelligent life.

    My estimate of 100 million years to colonize a galaxy assumes that FTL travel is impossible. 100 million years is a long time to travel 100,000 light years, especially if you’re a super-advanced von neumann machine.

  77. #77 Wow
    April 6, 2013

    Yes we do.


    Three very different branches of evolution with a hell of a long way to go back before they have a common ancestor, each having worked their niche with extremely high intelligence.

    “100 million years is a long time to travel 100,000 light years”

    So that gets you between two stars. Not much of a colonisation.

    You have to travel to one star. Colonise. Travel to a second. Colonise. Travel to a third… Travel to the 104,203,221,004th star. Colonise.

    Each traverse requiring ~10 years at light speed.

    Though it isn’t necessary to go linearly, unless your intent is to colonise every planet, there’s no damn reason to do so.

  78. #78 Steve Morris
    April 6, 2013

    These are not 3 independent data points. And who would colonise a galaxy one star at a time?

  79. #79 Wow
    April 6, 2013

    Yes, they are three independent data points.

    Unless you’re a YEC and all three were created a few thousand years ago with their intelligence as-is.

    And who would colonise a galaxy one star at a time? Anyone who had to colonise the stars.

  80. #80 Steve Morris
    April 7, 2013

    The octopus, dolphin and humans all evolved on the same planet from a common ancestor. That ancestor was already a highly evolved organism. It was multi-cellular, it was an animal not a plant, it had sense organs, etc, etc.

    wow, how do you do your weekly shopping? Travel to the supermarket, buy bread, return home. Travel to the supermarket, buy milk, return home. Travel to the supermarket, buy cheese, return home.

  81. #81 Wow
    April 7, 2013

    “The octopus, dolphin and humans all evolved on the same planet from a common ancestor. ”

    Steve, look up genetics and evolution, your complaint here is meaningless.

    Three very different clades achieved an intelligent version.

    You have to go back 600million years to find the common-est ancestor possible and evolution had 600 million years to explore the changes possible in an evolving system.

    They are definitely three independent examples.

    You are refusing them because you want your assertions to be correct.

  82. #82 Wow
    April 7, 2013

    PS note that we have no evidence against intelligence from intermediates from the 600mya ancestor to these three today, nor any that may turn up in the next 600 million years.

    Intelligence seems to be a viable survival strategy.

  83. #83 Sinisa Lazarek
    April 7, 2013

    “For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much — the wheel, New York, wars and so on — whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man — for precisely the same reasons.”
    D.A. – THGG


  84. #84 Wow
    April 7, 2013

    Of course, the mice were really in charge, so we weren’t free to play about in the oceans.

    Indeed the whole idea of coming out of the trees was a bad idea all along.

    Until we invented digital watches…

  85. #85 Sinisa Lazarek
    April 7, 2013

    There’s the answer to “where’s everybody?”. The highway got canceled, and now nobody wants to play with us anymore :)
    That, and being “mostly” harmless :D

  86. #86 Steve Morris
    April 8, 2013

    wow, please don’t patronise me by telling me to “look up evolution”.

  87. #87 Wow
    April 8, 2013

    Steve, you are deserving of condescension when you claim as you did.

  88. #88 SLC
    April 11, 2013

    Our brain-to-body-size ratio dwarfs that of our nearest competitor, the dolphin, by nearly a factor of two, and the next-nearest great ape by a factor of about three.

    If we’re talking about the bottlenose dolphin, it’s my information that it’s about 7/5. The bottlenose dolphin has an encephalization factor of about 5 while the average human has an encephalization factor of about 7. The bottlenose dolphin encephalization factor lies somewhere between Homo Ergaster and Homo Erectus.

    I have posted the following on Panda’s Thumb several years ago but it, perhaps, is worth repeating here. There is a good case to be made that larger brain size may have a selection advantage. The Cretaceous dinosaurs had higher encephalization factors then did their Jurassic ancestors while today’s mammals have a higher encephalization factor then the mammals of 50 million years ago. Encephalization is a necessary condition for intelligence. It is, however, not a sufficient condition as Homo Neanderthalis had about the same encephalization factor as modern humans and Homo Heidelbergensis wasn’t far behind. Organization of the brain is also important. The Sapiens and Neanderthals had different brain organization.

  89. #89 Wow
    April 11, 2013

    Dolphins don’t have to use a huge amount of brain matter to work out how to stand up on two feet.

  90. #90 Bill
    May 4, 2013

    Estimating the likelihood of intelligent life seems a statisticians game and I’m not a statistician. However, I feel intuitively that two important factors were left out of the post.
    1. what is the relative age of life (variable L) relative to the age of earth (variable E)? It seems to me that the larger the result of L/E the larger the probability that earth like planets have tendency to produce life. The Earth is 4.6 billion and life started 3.6 billion. It seems life started very quickly.

    2. What is the likelihood that life came into existence multiple times on earth? It seems much more likely that life started and failed multiple times on earth rather the it being the result of one unimaginably fortuitous event that managed to, even more fortuitously, survive a precarious environment. If this is true, doesn’t this virtually prove that the earth (and planets like it) are much more likely to produce life then not?

  91. #91 Yekai Wang
    June 6, 2013

    I completely agree with Bill that life started and failed many times on Earth and it took this long to reach where we are now. So in my opinion a civilization as advanced as us may be less than a dozen. The dinosaurs were wiped out by asteroids and we been lucky enough to not have been hit by any as devastating as before.
    The issue of space exploration is always dependent on the economy of said nation. A country struggling with it’s economy is less likely to fund space exploration and to make breakthroughs in space exploration, we need to allocate the funds to invent new and more efficient technology. However, o reach the point where contact is possible, we need advanced technology. Advanced technology requires an efficient energy source and there is only so much on a planet. Maybe other civilizations realized their impending doom and reverted back to a pre-technology era. Or when a society reaches this point, people would fight against each other as their survival instincts kick in, leading to the civilization’s self-destruction. Either way, the civilization will fall and be unable to contact us.