Earth - Moon System

If the Earth is Rare, We May Not Hear from ET

Article written: 8 Feb , 2010
Updated: 24 Dec , 2015

If civilization-forming intelligent life is rare in our Milky Way galaxy, chances are we won’t hear from ET before the Sun goes red giant, in about five billion years’ time; however, if we do hear from ET before then, we’ll have lots of nice chats before the Earth is sterilized.

That’s the conclusion from a recent study of Ward and Brownlee’s Rare Earth hypothesis by Duncan Forgan and Ken Rice, in which they made a toy galaxy, simulating the real one we live in, and ran it 30 times. In their toy galaxy, intelligent life formed on Earth-like planets only, just as it does in the Rare Earth hypothesis.

While the Forgan and Rice simulations are still limited and somewhat unrealistic, they give a better handle on SETI’s chances for success than either the Drake equation or Fermi’s “Where are they?”

“The Drake equation itself does suffer from some key weaknesses: it relies strongly on mean estimations of variables such as the star formation rate; it is unable to incorporate the effects of the physico-chemical history of the galaxy, or the time-dependence of its terms,” Forgan says, “Indeed, it is criticized for its polarizing effect on “contact optimists” and “contact pessimists”, who ascribe very different values to the parameters, and return values of the number of galactic civilizations who can communicate with Earth between a hundred-thousandth and a million (!)”

Building on the work of Vukotic and Cirkovic, Forgan developed a Monte Carlo-based simulation of our galaxy; as inputs, he used the best estimates of actual astrophysical parameters such as the star formation rate, initial mass function, a star’s time spent on the main sequence, likelihood of death from the skies, etc. For several key inputs however, “the model goes beyond relatively well-constrained parameters, and becomes hypothesis,” Forgan explains, “In essence, the method generates a Galaxy of a billion stars, each with their own stellar properties (mass, luminosity, location in the Galaxy, etc.) randomly selected from observed statistical distributions. Planetary systems are then generated for these stars in a similar manner, and life is allowed to evolve in these planets according to some hypothesis of origin. The end result is a mock Galaxy which is statistically representative of the Milky Way. To quantify random sampling errors, this process is repeated many times: this allows an estimation of the sample mean and sample standard deviation of the output variables obtained.”

Forgan simulated the Rare Earth hypothesis by allowing animal life – the only kind of life from which intelligent civilizations can arise – to form only if homeworld’s mass is between a half and two Earths, if homesun’s mass is between a half and 1.5 times our Sun’s, homeworld has at least one moon (for tides and axial stability), and if homesun has at least one planet of mass at least ten times that of Earth, in an outer orbit (to cut down on death from the skies due to asteroids and comets).

The good news for SETI is that a galaxy like ours should host hundreds of intelligent civilizations (though, somewhat surprisingly, there is no galactic goldilocks zone); the bad news is that during the time such a civilization could communicate with an ET – between when it becomes technologically advanced enough and when it is wiped out by homesun going red giant – there are, in most simulations, no other such civilizations (or if there are, they are too far away) … we, or ET, would be alone.

But it’s not all bad news; if we are not alone, then once contact is established, we will have many phone calls with ET.

To be sure, this is but a work-in-progress. “Numerical modeling of this type is generally a shadow of the entity it attempts to model, in this case the Milky Way and its constituent stars, planets and other objects,” Forgan and Rice say; several improvements are already being worked on.

Sources: “A numerical testbed for hypotheses of extraterrestrial life and intelligence” (Forgan D., 2009, International Journal of Astrobiology, 8, 121), and “Numerical Testing of The Rare Earth Hypothesis using Monte Carlo Realisation Techniques” (arXiv:1001:1680); this too will be published in IJA, likely in April.

, ,

55 Responses

  1. Hon. Salacious B. Crumb says

    Your quote says;

    “The Drake equation itself does suffer from some key weaknesses: it relies strongly on mean estimations of variables such as the star formation rate [SFR];”

    The only reason this was originally in the Drake equation is simply that planets need stars, and if the SFR is high, therefore there are more planets. IMO the complexity here is mostly in our understanding the stages of evolution of the SFR overtime in galaxies. Where the planet being formed are mostly after several generation of stars so the metal content (elements heavier than hydrogen and helium) of the galaxy is high enough so rocky Earth-like are able to form. Over time, the SFR decreases or declines in number because the hydrogen gas in the galaxy is being converted to stars becomes depleted. (I.e. Much of the gas left in elliptical galaxies has already been converted stars.)

    So although the quote given here by Duncan Forgan and Ken Rice is interesting, they and this article sort of misses out explaining the core reason why the parameter of SFR is important. While the “…mean estimations of variables such as the star formation rate” is used in the Drake equation, the star formation rate itself is quite variable depending on the epoch or evolutionary state of the galaxy too. So therefore, as an example, the formation of Earth-like planets capable of supporting life, say, between elliptical, irregular or spiral galaxies could be different even though the SFR is exactly the same!

  2. Jean Tate says

    Interesting comment, Hon. Salacious B. Crumb, but do keep in mind that Forgan and Rice tested only one realization of the Rare Earth hypothesis, and only for a galaxy resembling our Milky Way. As such, their simulations do include the estimated history of our galaxy’s star formation rate.

  3. gopher65 says

    I’ve seen articles recently that claim that life is less likely to evolve on planets that are less than ~2 Earth masses due to the inherent axial instability of such planets and the lack of ease of plate tectonics being maintained for a reasonable amount of time *cough*Venus*cough*.

    In fact, the articles are claiming that Earth itself might be a special case, where a low-mass planet was able to form life due to unusual circumstances (a large moon to stabilize the axis, etc).

    I wonder how this would have affected their simulation, if at all? Are higher mass planets less likely to form, more likely, or about the same?

  4. Molecular says

    I find it easier to go with the thought that for every star that shines in the night sky, there’s a distinct probability that, it too, has a solar system with planets, and on one of those planets (not necessarily Earth-sized), there’s a good chance that it has some form of life, be it intelligent, or not.

    We are wasting less time exploring the REAL Universe, rather than inputting values into a simulation, while lacking knowledge about how life can even come into to being.

    One can point in the direction that clearly indicates the prospects of a drinking fountain, or, dry up completely thinking that boulders act as sponges holding lakes. 🙂

  5. Member
    Aqua says

    IF Earth is the rarest and ONLY ‘advanced’ civilization in our galaxy.. there are still quite a few other galaxies out there! In which, faster than light inter-dimensional communication or travel may have been developed? Then the rarity of advanced lifeforms might make communications all that much more precious and sought after?

  6. Member
    Aqua says

    At least.. that’s what my ‘spirit guides’ tell me.

  7. There’s a big piece missing IMO, which is what happens to a civilization after it achieves interplanetary travel, and before its star dies out.

    While I do suspect that meaningful interstellar travel is impossible, long-term colonization is not technically impossible – hibernation + travel at even 1% the speed of light are not impossible.

    If you do the math on this hypothesis (assume 5000 years to make an interstellar hop, and 5000 years to boot a colony so it can spawn again), you’ll find out that the first species to achieve these technologies will populate the galaxy within an evolutionary blink of an eye.

    Which means the civilizations in the galaxy (which will be divergent from a common root) are not independent variables.

  8. oops, didn’t finish typing…

    So the bottom line from this is that the first species to achieve these technologies “wins”, though there are interesting variations on what happens next, still within the bounds of the hypothesis. (and it works even for slower travel time – even for 0.1% speed of light travel)

    What it doesn’t cover, and we have no way to imagine, is what happens after long period of technology. We’re obviously living in very interesting times – we only developed math and science 300 years ago. We can’t imagine what happens after 3000.

    If scientific discoveries continue at the current rate, then we might be teleporting across the galaxy. If basic scientific discovery dries up and we concentrate on technology, we’ll get close to the scenario described above. If technology advancement also dries up, well, we’ll even find other pursuits, or get really really bored, which is never a good thing when you have all that technology.

  9. SteveZodiac says

    The factors we needed to get where we are are so many I could almost (stress, almost) feel sympathy for the creationists.

    Slow burning G2 star
    Planets at all
    Goldilocks planet position
    Unusually large moon for Axial stabilising,
    Plate tectonics
    Inexplicably large amounts of water
    Iron core dynamo for radiation shield
    Jupiter keeping large rocks away
    several attempts over a billion years at decent oxygen levels

    and there are more I can’t think of ATM

  10. Lawrence B. Crowell says

    There are other factors as well. These include stellar systems of planets which can support a stable orbit of a planet in the “goldilocks zone.” A gas giant who’s orbit is less than 3AU from a G-class star would exert too great a perturbation on the orbit of a 1AU terrestrial planet. From extrasolar systems found so far the statistics on Lyapunov exponents (chaos time parameters of sorts) on extrasolar system data does not look very favorable. I wrote a paper on this and a version is in my book on the physics of interstellar probes. I estimate there are only around 1000 planets at all similar to Earth in the galaxy. As for intelligent life or civilizations that is some fraction of this. Given our duration on Earth is only 1:10^5 the duration of life here I suspect we might be lucky if there is one ETI currently, or within our past light cone of communication.

    Life might be fairly common in the universe. Some data does suggest that Mars has life, and there might be life in the sub-oceans of Jovian and Saturnian moons. Yet I would imagine that in these extreme conditions life is relatively basic, consisting of unicellular forms that manage to survive extremes, but are prevented from evolving into more complex life forms seen on Earth. The same might hold for planets which are hot, for extremophiles are known to exist deep in the Earth and emerge from hot volcanic vents. So for all we know there might be conditions, such as lofted in the atmosphere or in subterranean conditions on Venus, which support some basic form of life on hot planets.

    With my estimate of about 1000 bio-planets similar to Earth in the galaxy it turns out that one should exist within about 500 light years. This means in principle the Kepler probe should be able to detect it. We might be fortunate enough to find optico-chemical signatures of a bio-planet similar to Earth in this decade. Such a signature might include an oxygen atmosphere with traces of methane. This might be the best we can ever do. My book on star probes is motivated by the obvious desire to send a probe to a bio-planet if one is found within 25-50 light years, so we could get a laboratory and “field biological” picture of life there. The prospects are not really good for this though.

    I have doubts that our species will persist to the 5 billion years remaining for the sun. Our situation already looks alarming as it is, and we could well snuff ourselves out before long. Earth will go through some drastic changes, such as Pangea-II when the American and Asian plates eventually merge in 300 million years after squeezing out the Pacific plate. That will make life difficult, or most land area will likely be a harsh desert. And even with a recovery after then the increased solar irradiance will be 700 million years start to make things a bit too toasty for complex life. By 1.5 billion years Earth will start to look a whole lot like Venus. Even before then, the average mammalian species exists for only 3 million years, and hominid offshoots such as Homo neaderthalensis existed 350,000 years. Homo sapiens has been here for only 150,000 years, so we have not even matched Neaderthal’s record. Further, our recorded history is only 5000 years — a time blip on astronomical time scales. We have so far not proven our survivability on geological or astronomical time scales.


  11. I think requiring a large moon and other such mechanisms is over-doing it.

    I can see how some other civilization that grew on the “equatorial” ring of a gravitationally locked planet will argue that that’s the only way to evolve life, since a rotating planet will have extreme “day-night” cycle that will SURELY prevent any organism from developing.

    Or, a civilization in a super-Earth imagining that the levels of radiation we tolerate here will SURELY kill any complex life form, and so life can only develop on massive planets with soupy atmosphere.

    I like the wider definition of habitable, which is supporting the conditions for complex chemistries.

  12. Lawrence B. Crowell says

    Faster than light comunications and travel are very unlikely. This violates a whole lot of things. Maybe then again the problem is:


  13. Hehe LC… I can watch that clip endless times…

    The extra touch above and beyond the text is just so delicious…

  14. Member
    Aqua says

    LC… LOL! Been there, done that.. remember the ‘Meat Puppets’?

    A gold fish in a small bowl might think the laws of physics were very limited.. if he could think? Thing is, that gold fish is alive, and therefore possesses SPIRIT in a body, which is infinite…. so he doesn’t worry about how big his universe is.

  15. ND says

    Putting aside the violation of physics as we know it, I think a lot of people are assuming faster than light travel and communications will make large distances irrelevant. There might be limitations to it as well where FTL communications with other galaxies could take hundreds of years, as if communicating with systems in our galaxy. Also if there is FTL communications going on right now, we most likely cannot pick up on that. But then again the rather solid physics we understand make this a moot point.

    But, our wishes and desires of space travel wants FTL.

  16. mrdpearl says

    Well, as Carl Sagan said in his TV series Cosmos: “Somebody has got to be first”
    The mirth I find in discussing “other” life forms on “other” planets is that we are not certain how it all started here in the first place!

  17. Vedic says

    Arthur C. Clarke I think put it very well:

    “Either we are alone in this Universe or we’re not, and both possibilities are terrifying.”

  18. Drunk Vegan says

    “And even with a recovery after then the increased solar irradiance will be 700 million years start to make things a bit too toasty for complex life. By 1.5 billion years Earth will start to look a whole lot like Venus.”

    If we haven’t figured out how to successfully colonize and terraform other planets 700 million years from now, or at the very least, bump Earth’s orbit a bit to cool it down, or, heck, even re-engineer the sun – well, then of course we deserve to die.

    Of course it won’t be *humans* who are facing that dilemma in 700 million years, it will be a species descended from us, and probably heavily genetically engineered.

  19. Andy F says

    The Universe continues to throw shocks and surprises at us. Hence, I don’t think there is any reason for life, intelligent or otherwise, to exhibit attributes or requirements that our common sense dictates it should possess.

  20. Jean Tate says

    One thing to keep in mind: to what extent are the conditions for a Rare Earth inter-dependent?

    For example, in a planetary system around a star with solar metallicity, do the dynamics of formation lead to rather a lot of ~Earth mass planets+Luna mass moons+Jovian mass gas giants, all nicely spaced (goldilocks zone, screening, etc)? At the moment, there’s no observational basis to support any hypotheses.

    Fundamentally, however, all this work is based on a sample of one!

  21. Uncle Fred says

    I prefer to be somewhat more optimistic then this article suggests.

    LC mentioned the possibility that Earth similar planets may be extremely rare. Yet our sampling in this area is still non-existent. Despite the fact that we theoretically have the capabilities to detect earth sized planets (in their Goldie-locks zones) we have thus at best been able to verify only down to the super-earth size. Furthermore, these super-earths are all situated extremely close to their parent star.

    Could we be jumping the gun a little? Perhaps over the next few years, as more and more search techniques and teams can comfortably resolve these planets, we might have a basis for statistical analysis.

    Wouldn’t you agree?

    Kind Regards,


  22. Lawrence B. Crowell says

    Uncle Fred: The sample is admittedly biased. Close in jovians are easier to detect and tend to be found more readily. The Doppler shift periodicity is short and stronger. I did the analysis originally back in the 90s, and redid them for the book. Remarkably the statistics did not change that much, though upward some from about 300-bioplanet to 1000 or so, and this is with newer techniques as well. I frankly hope the stats edge up to several thousands or maybe 10,000. That would put a bioplanet within 100 lightyears of Earth with about a 50% probability.

    @Drunk Vegan, I have pretty serous doubts we are going to engage in such massive engineering feats. I have doubts about things like ring worlds or Dyson spheres, which BTW are not gravitationally stable.


  23. quack says

    fascinating subject! great comments! I have often mused it would be nice to come back in 1000 years only to see progress( or lack of) in my profession and see what humanity is up too! lol


  24. Torbjorn Larsson OM says

    Interesting as SETI is, and useful as Rare Earth simulations may be, it’s a daft idea and not really a hypothesis as I understand it; how would you test it?

    As always you want to start out with the most general situation and restrict as data and tests become available.

    All we need to get cellular life started seems to be a chemiosmotic gradient such as found around alkaline vents in acidic CO2 oceans. Or at least, that seems to be the most popular proto-biologic environment among biologists.

    Many worlds will fulfill that, and there are high hopes for exoplanet searches for biospheres. [Of which we unfortunately only can detect class I habitats, i.e. Earth analogs.]

    The problem for SETI is the requirement for multicellular life. It only evolved once over billions of years on Earth.

    I can’t even begin to imagine how tides and axial stability would affect either of those two processes (pro- to protobiology and mono- to multicellularity). [Besides, axial stability seems to be more common than not, looking at tidal lock in G stars habitable zones or Earth analog moons around super-Jupiters.]

    But as I understand it Ward and Brownlee had a religious agenda, where a rare Earth wasn’t a hypothesis to be tested but a desired outcome to parade around. I might be wrong, though.

  25. Chuck La Monica says

    An advanced ET civilization could be as close to Earth as the Alpha ‘C’ system and we will never hear them. The RF signal to noise ratio across all frequencies is comparable to the light output of ‘a lit candle compared to the surface brilliance of a star.’ An impossible detection challenge. In addition, a not likely deliberately aimed at earth multi-million watt transmission will be anttenuated to viturally nothing and lost in background RF noise at 4 plus light years. Concerning space travel, it is unlikely mankind will ever leave the influence of our sun for a multitude of reasons. I suspect the number one reason will be money. And I believe number two will be a ‘no sensible return on a multi-billion dollar and thousand-generation time investment.’ I’m convinced SETI is wasting their time and money. I doubt mankind will survive long enough to solve all the technical problems of colonizing someplace beyond two or so light years distance from mother earth.

  26. Torbjorn Larsson OM says

    several attempts over a billion years at decent oxygen levels

    Attempts for what? Oxygen is detrimental to pro- and protobiology both. (Less organics, highly poisonous.)

    Fortunately it isn’t an expected steady state probiology chemistry for thermodynamical reasons.

    all this work is based on a sample of one!

    Not quite. Likelihoods for both the pro-to-protobiology and the mono-to-multicellularity processes can be estimated by Earth record, since several attempts can be made over certain periods of time. The former is highly likely (as soon as the LHB provided enough volatiles, there’s a life record). The later is less likely (once during 3 Gy), but would then happen on most inhabited planets.

    [Biologists beg to differ of course, there’s more latitude in the contingency of evolution than the simple facts of cells can tell us; cellular machinery, communication et cetera may differ. But it is the best estimate we can make as of yet.]

  27. mike g says

    A.C. Clarke had an interesting explanation for “where are they” in the final of his “Rama” novels. It turned out civilizations were common but a galaxy spans a vast space in three dimensions and a vast amount of time in the fourth dimension. So, civilizations are not likely to cross paths during their brief existence.

    What I got from his perspective was that they would be brief because they really wasn’t much point to existence. I’ll say that in a later novel, he found a point to existenace and created himself an afterlife just like Heinlien and Pohl did in their later years.

  28. Jean Tate says

    Torbjorn Larsson OM, Ward and Brownlee did not have a religious agenda (and their work stands or falls on its scientific merits even if they did).

    One of the rather solid pieces of science in the hypothesis (whether due to Ward and Brownlee or not) is the consequences of ‘death from the skies’, and the role of Jupiter – in our solar system – in substantially reducing that risk from asteroid and comet impacts.

  29. Drunk Vegan says

    @Lawrence B. Crowell:

    I too am skeptical about ringworlds and Dyson spheres. But the prospects for terraforming, interstellar colonization, and orbit-shifting are quite a bit “easier.”

    Sure, we can’t do it now, but I have no doubt that if we survive for another 100 years, terraforming over a few centuries or millennia will be well within our capability.

    If we survive 1,000 years more, interstellar colonization will still be arduous and difficult, but perfectly viable given likely advances in propulsion, life support, genetic engineering, and possibly suspended animation.

    Given 10,000 years it should be relatively easy to move the planets in their orbits – we already know the technique that would be required (gravity tug), we’d simply have to employ it on a much more massive scale than we would with an asteroid.

    We’re talking about 700 million years of advancements before the sun starts to bake Earth… we can’t even imagine what we’ll be capable of at that point.

    I only hope that we survive long enough to spread.. our predator genes don’t exactly make peace an easy prospect.

  30. Lawrence B. Crowell says

    @Torbjorn Larsson OM: Rare Earth is a testable hypothesis. If we can perform a survey of extrasolar systems with an optical interferometric telescope we might get a data base of thousands of terrestrial type of planets. If there are only a few which are similar to Earth, or none at all then that supports the hypothesis.

    I believe it was G. Gonzalez who came up with the rare Earth hypothesis, and he did later come out as an inteligent design upholder.

    @Drunk Vegan: To be honest I think if there is anything which continues from our species off Earth it will be self-replicating nano-bots and probes. These might come to inhabit asteroids, using them for resources, and they might over time evolve to inhabit more of the solar system, develop greater levels of complexity and eventually migrate out into interstellar space.

    To be honest I think the odds favor a complete and utter collapse of civilization in the next 1-200 years. This collapse will be precipitated by resource depletion and a planetary eco-spasm or mass extinction we have “engineered.” Our species under those conditions may never organize complex societies as seen in our history, and further our species may fade out into extinction.


  31. Hon. Salacious B. Crumb says

    Why was my previous post here deleted?

  32. Hon. Salacious B. Crumb says

    Here it is again;

    Jean Tate said;

    “Interesting comment, Hon. Salacious B. Crumb, but do keep in mind that Forgan and Rice tested only one realization of the Rare Earth hypothesis, and only for a galaxy resembling our Milky Way. As such, their simulations do include the estimated history of our galaxy’s star formation rate.”

    Well yes and no. While it is true the star formation rate (SFR) and initial mass function (IMF) are highly variable over time, and the important difference to this new study, this was not my point.
    As I said; “This article sort of misses out explaining the core reason why the parameter of SFR is important.” All I’ve done is simply to explained why.
    An additional relevant point is that the star formation rate (SFR) and initial mass function (IMF), stochastic star formation (SSF), etc. have been used as parameters since the 1980s when astrophysicists were first investigating the formation of galaxies by computer simulations. Most of these ideas are these days are considered generalisations in computer simulation studies of galaxy formation – mostly with the increase of computing power in these simulations. It is interesting to see that Forgan and Rice freely admit their Rare Earth hypothesis needs;

    A more accurate Galactic model, taking into better account its chemical diversity, stellar clustering and the inner regions (specifically the central supermassive black hole and the hypervelocity stars orbiting it).

    Specifically, and to be more In how they use SFR and IMF is their simulations; The “Earth Criteria” for this “Rare Earth Hypothesis”, where the SFR is classed under “A star located in a critical region of the Galaxy – the “galactic habitable zone”.” As to the use of the initial mass function (IMF) parameter in the Rare Earth Hypothesis, they view ” stellar mass is a key condition” I.e. Mass distribution of stars limiting Earth-like planets to a small range of stellar masses. [Note: This is a rather superficial input into the simulation they have done IMO. However, based on the complexity of the problem it is quite understandable.]

  33. Uncle Fred says

    Thanks for the insightful reply LC. The human and optimistic side in me shares your hope that your (and others) current models will be fine-tuned in a more hopeful direction as more data becomes available.

    I do have a question for you:
    If there is indeed the likelihood of a Earth similar-habitable planet within 50-100 light years:

    1. What is the statistical likelyhood of us finding it based on current search techniques/funding etc.?

    2. How long do you estimate till one could be found (general reasoned guess is fine)?

    3. If we do find it, what can we decern from it using current, or near-term techologies/techniques?



  34. Lawrence B. Crowell says

    @ Chuck La Monica: The thing which puts the kibosh on electromagnetic communication across large interstellar distances is the Debye length. The interstellar medium is filled with gas, about 10 atoms per cubic meter (so it is not a lot), but where some of this is ionized. The result is that any electric field is lost in the dipole electric fields of ionized gas. So any EM field decreases over a length at a rate faster than 1/r^2. This is related to the skin depth of EM radiation in a conducting medium, and why submarines must communicate by very long wavelength EM fields. So looking through the plane of the galaxy with radio waves is a bit like looking through a partially opaque medium. For very powerful sources of radio emissions, such as the Crab pulsar, this attenuation is not that significant, but for the rather moderate or weak EM fields (100-1000 megawatt range) produced by technology these fields will drop to the noise limit within around 10 light years out. So if there are ETI on eps-Iridani listening in to the EM local universe I doubt they are now getting our news reports on the Gore-Bush campaign of 2000 shaping up back then. Unless some ETI send signals out in the terawatt power range or more their signals would simply be lost in the EM noise of the galaxy before reaching the extend of the galactic volume.

    In part the reason we will probably not move out into space is money. Money should properly be an energy-entropy measurement unit, not a game token in the sort of casino economy we have today. Within that perspective, a rational economic system and not the loony-bin game we currently have, the balance sheet for putting humans into space is very much in the red. There is not a whole lot out there for us to really live on, and we have to make everything required to sustain ourselves in space at a huge energy or money cost. Extending humanity into interstellar space is a many orders of magnitude greater problem. Already we see this with the cancellation of the return to the moon program, which had as its goal some permanent human (or more to the point American) presence on the moon at a multi-hundred billion dollar cost. I think the bell is tolling on our prospects for ever becoming a space faring species or civilization.


  35. Dark Gnat says

    Personally, I doubt civilization will be around in 100 years. We are draining resources, and are too greedy and warlike to migrate to a new energy system.

    My prediction is that governments will decide that it is easier to reduce demand on said resources, and the best way to do that is to lower the population. Forced abortions, deliberate neglect of the elderly and sick will be the first phase. Biological agents will be used to accomplish the second phase, which will be the elimination of those with certain traits that are percieved as weaker. It will likely be a common cold or flue used in a Darwinic way. Finally, masses of people will simply be exterminated via chemical biological agents, possibly including concentration camps, and yes that will include certain ethnic “undesireables”.

    The ones that are left will be in the best health, or the ones with the greatest wealth and power. To them, many of our problems will be solved: less war, less environmental destruction, etc, but I fear no one will understand the real cost until it’s too late.

    Either that, or machines will reach A.I., take over and nuke us.

    Point – even if there are Intelligent E.T.’s out there, why would they want to talk to us?

  36. Lawrence B. Crowell says

    @Dark Gnat: The problem with your scenario is that it will lead to mass-insanity and some sort of war. To be honest since 1995 I think we have gotten more signatures of this in the United States. Some of the GOPers are getting behind Sarah Palin. For an example of insanity she addressed the Tea Party Convention last week. Now these folks have their underwear all caught in a wedgie over the cost of Obama’s healthcare ideas. Sarah Palin called for a war on Iran. Wars don’t come cheap, and a war with Iran will be a far bigger committment of money, manpower, combat loses and resources than Bush’s Iraq and Afghanistan wars — morphing more into what is an Af-Pak war. So here are these T-P nutso’s cheering and raving over Sarah’s proposal, which will cost far more than any national health plan. I call this insanity, and Hitler was raised up in Germany over a comparatively minor economic problem and created instead a world war that crushed Germany in the end.

    Societies have gone into mass insanity before, where they raise up mad Kings, dictators, füherer’s and general war-mongerers. Germany in the 30s and 40s was the big example, and more recent cases of this have been Rwanda and Yugoslavia. As I see it the people of the US of A are flirting with much the same, and have been pretty seriously since 1995. That a political movement founded on “no or low taxation” can go into ecstatic frenzies over someone who calls for a war against Iran, a war which will be far more serious than the one’s we are in and which could turn the whole region from New Delhi to Gaza into a mass-war-zone, clearly indicates some sort of mass mental incoherence that is creeping into American society. If this sort of thing takes complete hold over the nation it has to be pointed out that we live in a world with thousands of nuclear warheads, and where we are reaching certain planetary limits. I give it half a chance the person who blows up the world will be a Republican waving an American flag in one hand and a bible in the other.

    We might avoid this disaster this decade, but given certain mass behavioral proclivities of our species this all looks like some sort of global Russian roulette game. Eventually humanity will probably drink the cool aid in a massed global Jim Jones episode.


  37. Mr. Man says

    I think Obama made a grave mistake cancelling constellation
    but that doesn’t mean that we will never extend into space. 100 years ago we were trying to figure out how an airplane (which at that point was more or less a piece of wood and paper attached to a motor), now we have advanced Jet engines and a space station in LEO. People always assume (wrongly) that current technology is as advanced as it will ever be. In regards to aviation Lord Kelvin seemed to have a similair pessimistic tone:

    “I have not the smallest molecule of faith in aerial navigation other than ballooning”

    Look around the sky today and it’ll be hard not to see a plane. My point is that we can move into space, eventually. The one plus side of Obama’s decision would be more time spent by NASA to develop greater technology for future manned missions. In regards to ETI I believe in their existence and quite frankly think the rare Earth hypothesis is narrow minded as it basically lists every factor that led to our own rise as essential for any intelligent life form. One of their factors that particularly bugs me is the status of a Jovian planet in the outer solar system as essential due to deflecting incoming astriods/comets. Jupiter may deflect astriods, but since it’s gravitational field throws astriods in the astriod-belt out of equilbrium, its sends other ones to us instead! Ward and Brownlee are surely smart, but I think that their hypothesis is wrong. Anyway we’ll find out soon enough. Still, I do have doubts we’ll be meeting an ETI any time soon.

    Mr. Man

  38. Underlings says

    What about the idea that once technology reaches the ability to precisely manipulate matter at the molecular level, expansion into space will occur at exponential rates? This would not only drastically increase contact likelihood, but also obviate the need to factor in the lifespan of the home sun.

  39. Lawrence B. Crowell says

    It will have no impact if the worst happens. Suppose by various mis-steps Palin is elected President in 2012. She and her “handlers,” needed since she is not mentally competent to really run the country, decide to launch a full out nuclear attack to bring Jesus back. BTW, she tends to believe that sort of stuff! That will nix any prospect of humanity moving into space for sure. And we are seeing more and more mentally disordered people rising up as prominent voices and power-decision makers of late.


  40. Mr. Man says

    Palin is not the sharpest tool in the shed, but I sincerly doubt she would launch salvos of Nukes just to bring Jesus back.

  41. Jean Tate says

    Hon. Salacious B. Crumb,

    Your post was not consciously deleted, but was probably posted in Universe Today on the old server, around the time Fraser moved us to the new one, and got stuck there (Fraser mentioned that server moves always result in problems of one kind or another).

    Sorry about that.

    Thanks for your clarification.

  42. Lawrence B. Crowell says

    @ Mr. Man: I think it is more likely that the people behind her would not permit it. She is not mentally competent. When she gives a speech that is anything beyond glittering generalities and mocking terms she degenerates into speaking incoherent sentence fragments. If by some disaster she became President, she would largely be a puppet or a manipulated figurehead.


  43. Hon. Salacious B. Crumb says

    @ Jean

    I though that it might be something like that as I could see any problems with what I’ve said. these thing happen I suppose.
    It is interesting that the Drake equation has SFR as the first item (R*) [R star], which was originally given by Drake as “the average rate of star formation in the galaxy”
    Most have interpreted this as “the mean star formation rate over the age of the galaxy”

    In the end, this important part of the equation is really based on our knowledge of star formation (and recently planetary formation) and the processes taking place. As we have yet to even understand why, for example, the outcomes of nebulae produce say many small stars with a few massive ones or just a whole lot of medium solar-type stars.

    It is also interesting that this is the only stellar parameter in the equation. It has always been ill-defined and ambiguous in its interpretation. Thinking about it, Duncan Forgan and Ken Rice have really done the same – interpreting how stars are formed throughout the whole spiral galaxy.

    As a open comment, it is surprising that the Drake equation dos not have a universe evolution component. I.e Where life can only exist within a range of time – say when the amount of metals (those elements heavier than Helium) were available for planet formation or when the available nebula gas in a galaxy is depleted sufficiently to make star formation a rarity.
    In this view, for example, life is unlikely to have been created in the first billion years or 100 billion years from now.

  44. Hon. Salacious B. Crumb says

    Mr. Man Says:
    February 10th, 2010 at 11:56 am
    Palin is not the sharpest tool in the shed, but I sincerly doubt she would launch salvos of Nukes just to bring Jesus back.Mr. Man

    Question: Should this be added as another variable in the Drake equation. I.e. f_sub_p ??

  45. Lawrence B. Crowell says

    I think the Drake equation has a factor involving the duration of any intelligent life. The problem as I see it is that our intellectual abilities are a sort of byproduct of our complex social behavior and language. We did not evolve to build machines, probe the atom or look deep into the unvierse. Yet, we have that ability and we have gotten far with it.

    At the core our behavior is from our hominid evolution, which is really just a branch of apes in general. So here we are as somewhat brainy ground apes largely rampaging exponentially out of control. We also have nuclear bombs, and are tearing down the planet at an astounding rate. It would be if you left loaded guns near a chimpanzee troupe and watched the show —best done at some distance I should think.

    So I suspect most ETI confront this problem, and many go extinct I would imagine. Intelligent life does not evolve to learn quantum mechanics, but does so as a byproduct. This would in many cases lead to conflicts between their base behavior and their intelligence. StarTrek advanced a fictional species of aliens, the Vulcans, who managed to get a grip on their behavior, individually and collectively. That is the route for any long term survival of an intelligent species of life. We are long away from this goal, and our exponential trends make time frames for addressing this issue rather short.


  46. Dark Gnat says


    Your right that war will certainly play a part, along with pestilence, famine and death.

    It’s strange that we will bring the things we fear the most upon ourselves, especially when we have the ability to avoid them.

    I consider myself very conservative. I believe in small government and that the right to bare arms is critical for democracy, but people like Sarah Palin frighten me. Both Democrats and Republicans have become shallow reactions to each other, and are neglecting the people they represent and their constitution.

    When people become desperate, they become gullible – that’s how dictators come to power. Certain politicians also tend to play the “Providence” card as if they are destined to lead people to greatness.

    They prefer to keep the populace uneducated and distracted while they quietly remove rights and liberties under the guise of “security”, “public safety” “crime reduction” or whatever else is convenient. All governments are corruptable, and larger governments tend to lead to larger corruptions.

    Watching “The Road Warrior” the other day, I thought to myself that the film was probably an accurate depiction of the future – much more accurate than Star Trek, for example.

  47. Uncle Fred says

    This forum has (understandably) become a place to vent our doom and gloom frustrations.

    LC, I was hoping to hear your answers to the questions I posed earlier. I feel few have addressed these questions directly in any recent article. Here is what I gathered since last night:

    1/2. On the statistical likelihood of finding a Earth-like planet within 50-100 light years (your optimistic variables):

    – Guesses are to be avoided, but many claim one could be found within 1-5 years. Does this seem reasonable? Kepler perhaps? Problem I find with Kepler is that it is only looking at a small chunk of the sky. Yet since Kepler is looking further afield then 100 lights years, it may find something further out.

    3. If we do find it, what can we discern from it using current, or near-term technologies/techniques?

    – From my understanding, and I am no scientist, but we could deduce its mass, internal composition, orbital characteristics, median temperature, and traces of it’s atmospheric composition. We could infer (guesstimate) on other basic areas such as rotation and tectonic activity.

    Am I correct? Have I missed something? Let me know.



  48. Lawrence B. Crowell says

    I did my analyses by computing the Lyapunov exponent for a three body system, such as Sun, Jupiter and Earth (ignoring other planets), for the chaotic drift of the Earth-like planet. I then ran some Bayesian calculations of the likelihood of an Earth like planet at a radius r ~ 1AU orbit etc around a F_l, G, K_h (h and l mean high and low) class of star. If the Jovian planet is too close to the star it rattles the orbit of any 1AU radially distant planet too much for the planet to remain their in a stable configuration. I came up with close to a thousand such planets may exist in our galaxy, using as a Bayesian prior estimate based on our solar system and another one found which is a “close match.” Now a part of this estimate, an priori assumption is also used based on the existence of a band in the galaxy with stars that have statistically an optimal metallicity (elements higher in atomic number than helium) that is about 10% of the galaxy. This is a sort of habitability zone in our galaxy. So let us estimate in a ballpark fashion how close these stars would be. For a 100,000 light year diameter galaxy that is a disk area of about 3e^{10}ly^2, where the area which we think. Now using my estimate of 1000 stars bearing a planet at least comparable to Earth, then the area which includes these stars is ~ 3e^8 ly^2 divide by 1000 and take a square root and we get an average distance between these stars as 550 light years. For amore optimistic 10,000 Earth-like planets this is an averaged distance of 173 light years. Yesterday I came up with the 100 light years by ignoring the factor of pi in the area estimate I ran in my head. So at 173 light years averaged distance between stars with a stable 1AU orbiting planet we should be able to observe one or more of these. The Kepler spacecraft, or subsequent generations of similar spacebased observing systems, may indeed find such a star. In my book I discuss this in the context of the physics of sending a spacecraft to another star. If we get lucky and find such a planet within a few tens of light years we might be able to send a probe to this star system to take a close look.

    In observing extrasolar system the orbital characteristics (6 parameters of an orbit in Newtonian mechanics) can be estimated, the mass and density of the planet can be further estimated. In an optical interferometer a closer look can be made, and the chemistry of the atmosphere and surface measured in a coarse grained fashion. The surface geology (tectonic plates etc) is harder to infer. From such data signatures of possible life might be found, which might be strongly suggestive of a complex biologically active planet. There are of course other possibly competing factors, such as whether the rotational axis or angular momentum of the planet is stable or not. Earth is pretty highly stabilized by the presence of the moon, which by tidal interactions in a sort of “pin-orbit coupling” keeps the rotational axis of the Earth fairly stable. On the other hand it is possible that a planet not so well stabilized might evolve life capable of adapting to such changes.

    As for the “doom factor,” this does enter into this discussion with respect to the longevity of ETI and ourselves. To be honest I don’t think things look terribly good for us over the next few centuries. I will also say that I think that there is a lot of hubris in connection with our ideas about what we might be able to control and have power over in the future, such as controlling planetary orbits, colonizing interstellar space etc. These ideas in some measure seem to reflect our bias that the universe ultimately exists for us, or that we are at the center of things. This bias seems to be expressed in a science, or science fiction, type of format.


  49. Dark Gnat says

    I don’t mean to sound like a downer, but the reality of the situation makes our chances of survival slim…at least civilized survival.

    Humanity might survive and once again regain “civilization” but it is my hope that when that happens they will be aware of what brought us down.

    It’s possible that there are many ETI’s out there but unless they have found a way around the limits of the universe, they may figure that there isn’t much point in contacting us anyway. After all, what could we do other than say “Here we are.”

    If they are 700 light years away, we might be able to beam signals to them, but by the time we get a responce, at least 1400 years will have passed on Earth. Empires could have risen and fallen in that time. This of course assumes that the signal is still detectable by the time it gets there. Obviously I hope they are closer.

    I predict that if we are visited by ETI’s, then they would likely be very far ahead of us technology wise, and possibly thought capacity. Looking at how destructive we are, they may decide that we are simply roaches to be exterminated.

    Or they will be nice and give us hovercars, teleporters, and replicators. But what would we have to give in return?

  50. Paul Eaton-Jones says

    If there is a is a galactic civilisation that trades, exchanges ambassadors and goes to war it is more likely to be found inward of our position out here in the suburbs. Why would any starfaring nation come out here where the distances between star systems are so vast. The idea that they might send out ‘genertional’ ships is ridiculous. A civilisation with ‘slow’ star ships might do that but if you’re part of an interstellar community you’re not going to come out here unless you have FTL technology. Also why would you send signals out to the ‘burbs if communication is going to take thousands of years each way. That is the more likely reason we haven’t heard from them – not because they’re not there but because it’s not worth while chatting to people 15,000 light years away. They’re probably there but not interested. I think that would come as more of a shock to humans [intelligent life not intersested in us] than the fact we’re totally alone.

  51. Paul Eaton-Jones says

    Again we get bogged down with things we can’t yet prove i.e. numers of stars that can allow the formation of planets with atmosphere, liquids etc. The number of planets that can support life once it’s appeared and lives long enough to bring forth intelligent life capable of reaching the staers etc etc. All the discussions are based SOLELY on the fact that life evolved here, on earth, on one planet. Reducing the number of stars that may just allow life to evolve in its system down from 200/400 billion to a billion, a million, a thousand or just one is pointless. Informed/intelligent guess work? Based on what? Nothing. It seems all calculations are based around water, carbon, a large satellite, plate tectonics,equitable temperatures we have here and anything different and it won’t occur or be extremely difficult! Sheer hubris. Until we find unequivocal evidence from beyond earth speculation based on unknowable numbers and conditions and making [firm] declarations is verging on the ludicrous.

  52. Jean Tate says

    So far as planets with life, complex life (a.k.a. multicellular), animals, and intelligent animals are concerned, the science is severely constrained by having a sample of one.

    I’m not sure what the current status is for the number of times multicellular life evolved – more or less independently – from simple life, but there certainly were several resets in the evolution of animals (there are at least five mass extinctions, of which at least two caused a pretty major change in the fauna of Earth).

    There’s a lot more data on the rise and fall of civilizations, and in terms of the kind of simulation Forgan and Rice ran, it sure is fun to think about what the planetary conditions for intelligent animals to develop civilizations which can engage in SETI are.

    For example, Jared Diamond’s book Collapse suggests that human societies are not especially good at managing their resource usage sustainably (at the society level, you might say they are suicidal).

    Also, why didn’t science in the Middle East (during the European Dark Ages) or China (ditto) get to the point of discovering that the rules which govern celestial events are the same as those down here on Earth?

  53. Lawrence B. Crowell says

    A lot of this depends upon whether life is fairly common or not. This is different from what I would call a bio-exuberant planet like Earth. I think Mars might have life, and there are ideas of Jovian and Saturnian moons having sub-iceshelf oceans with life. Yet in these cases it appears that these bodies are not bio-planets, but cases where life emerged at some point and has managed to continue by adapting to severe environments. Martian life, should it exist, is not likely to be much more than prokaryotic-like forms making a living in the soil or in little niches free from solar UV and where they can catch a bit of water now and then. Time will tell of course whether this is at all the case. Yet if life is a fairly normal product of chemistry or geochemistry, and if it is found to happen in a number of cases in our solar system, we can pretty safely assume that it is common throughout the universe. My estimate was only that there are about 1000 planets in some orbital and stellar configuration similar to Earth’s. If this estimate is close to the mark (say by an order of magnitude or so), then these planets might be expected to have life and temperature and energy flow through which might foster complex life in fecund ecological systems. Even without the moon a planet like Earth might still harbor complex life, though of an entirely different nature than we have here. By complex life I am referring to any multi-cellular (like) form, and the early Cambrian period with small shelled animals, spirogyra like plants, worms etc is an example of complex life. So there might exist millions of planetary bodies in the galaxy similar to Mars or the Jovian moons with unicellular life, but I suspect far fewer planets are bio-philia zones similar to Earth.

    Finding a bio-planet in some other stellar system of planets is the great coup we might be working for. If we get some signal from an ETI that would approach some the dimensions of a religious revelation of some kind. I am frankly rather dubious about our prospects for ever getting an ETI call. Yet if we find a bio-planet or two out there we can infer the existence of ETI. The cosmological data indicates the universe is a flat space (k = 0 in FLRW) which is expanding outwards (a time-time curvature in general relativity) according to so called dark energy. In such a universe if we know life exist elsewhere in abundance on some planets then it would also throughout the universe. This a Copernican principle: The universe on average appears the same everywhere. So doubtless there then should exist other intelligent life forms.

    We have to then bag our first bio-planet out there! Maybe Kepler will find one. Until then we can only at best try to estimate upper or lower bounds on occurrences of situations favorable to life and to make other estimates which might be better than complete shots in the dark.


  54. William928 says

    An interesting article, and even more interesting comments. @Paul Eaton-Jones:
    I don’t believe anyone is making any ironclad suppositions about life on other planets, simply offering food for thought, and in my opinion, interesting topics for discussion. It’s fairly clear that until we discover space travel approaching C, it’s highly unlikely we’ll ever meet any intelligent life. This doesn’t preclude speculating about what may be out there however.

  55. Paul Eaton-Jones says

    Agreed that The Copernican Princilple states that the universe on average appears the same wherever you look but I don’t thinkit should be used to infer that life must/probably/possibly exists elsewhere just because it does here. I personally feel that the Milky Way is teeming with life at all levels of complexity and organisation. We should stop using humanity as a yardstick against which we measure the viability of ‘other’ ET civilisations. Just because our 5-6 thousand year history is littered with wars, self-induced famine, environmental degradation etc does not mean for one second mean that someone else will/has followed the same path. Again, hubris. Doing so moves the argument close to the pre-20th century “we’re the centre-of-the-universe-and-aren’t-we-special”. Just because we have the tendency to screw up don’t think ETs have to.

Comments are closed.