Imagine an extraterrestrial civilization that manages to colonize the entire galaxy. Then imagine the colonizing civilization collapsing so definitively that no trace of its existence has yet been detected, at least from our planet. We can call it, as Jacob Haqq-Misra and Seth Baum (Pennsylvania State University) do in a recently released paper, a ‘graveyard civilization,’ one whose remains might still be accessible provided we know where and how to look.
Pushing the Limits of Growth
What could bring down such a civilization? The idea here is that we can explain the Fermi paradox (‘Where are they?’) by assuming that exponential growth is not a sustainable development pattern for intelligent civilizations. The authors draw on human experience in analyzing this possibility. Here’s the gist of it:
The consequences of unsustainable development are often dire. In many documented cases, resource depletion caused by human activities has led to the permanent collapse of human populations, and resource depletion and environmental degradation can also cause or exacerbate violent conflict. Note that collapsed human populations do not necessarily disappear —they may persist in diminished numbers. This is particularly evident in the case of Easter Island, where resource depletion is believed to have caused or significantly contributed to a major population decline. Some analysts are concerned that the unsustainable practices of human civilization could lead to a global-scale collapse. Should such a collapse occur, human civilization would not be able to colonize the galaxy.
Fermi’s question, of course, was built around the assumption that alien civilizations would do more or less what we would do if we had their technology, which is to explore and colonize the galaxy the way we have done these things on our own world. Thus one answer to Fermi is that the reason we do not see evidence of extraterrestrials is that exponential growth patterns throughout the galaxy are not feasible. This does not rule out the existence of ETI, but does establish some constraints:
…the Paradox can only conclude that other intelligent civilizations have not sustained exponential growth patterns throughout the galaxy. It is still possible that slower-growth ETI civilizations exist but have not expanded rapidly enough to be easily detectable by the searches humans have yet made.
Such a slower growth pattern resonates in an era when ‘sustainable development’ in everything from technology to agriculture and environmental protection is much in the air. Civilizations moving beyond their growth limits, under this scenario, might find themselves in a state of retreat:
It is also possible that faster-growth ETI civilizations previously expanded throughout the galaxy but could not sustain this state, collapsing in a way that whatever artifacts they might have left have also remained undetected. Both of these growth patterns can be observed in human civilization, suggesting that they may be possible for ETI civilizations as well.
Recalibrating the SETI Search
You can see the effect of this on SETI strategy. Haqq-Misra and Baum suggest that SETI be recalibrated to focus on slow-growth civilizations, and those that have already endured their collapse. After all, a society that has chosen a sustainable, slow growth path may still broadcast a signal detectable by SETI. So, too, might a post-collapse culture, which might beam the story of its downfall out to the broader universe, or perhaps use automated systems to send out a galactic requiem.
But the authors’ first choice for SETI is to follow up on the possibility that slow-growth cultures might still be able to send small, long-duration star probes, in the absence of true colonizing forays into the universe. If so, we might consider complementing the SETI search with SETA (Search for Extraterrestrial Artifacts), which has been considered at both visible and radio wavelengths. The paper goes so far as to suggest that “…a survey of the solar vicinity may be more pragmatic than an all-sky search for encoded messages.”
What we don’t know is how representative we are. Nor do we know the limits of exponential growth, for they may lie not at the planetary but the solar system level, assuming they’re not fully surmountable in the first place (by some future civilization if no one has done it in the past). A success at finding some kind of artifact here in our own system would at least tell us that an interstellar crossing is not out of the question, but how much further do we want to take these conclusions? The authors raise the question themselves, and point out that “…we cannot rule out the possibility that ETI civilization may follow a development pattern sufficiently different that we wouldn’t recognize it even if we detected its signal.”
The paper is Haqq-Misra and Baum, “The Sustainability Solution to the Fermi Paradox,” Journal of the British Interplanetary Society 62 (2009), pp. 47-51 (available online).
One method advanced (but extinct) civilizations may have employed would have launched spacecraft into counter-rotating Galactic orbits, thereby increasing the number of targets flown by at close range by per unit time.
Here’s a link to a poster that outlines the concept and provides an example of a search strategy we may employ to detect such spacecraft:
Link to “Galactic Drifter SETI” poster: http://allsouls.0nyx.com/seti/gds.html
“Should such a collapse occur, human civilization would not be able to colonize the galaxy.”
I disagree with this as a blanket statement. There would be no a priori reason preventing the post-collapse survivors from rebuilding and successfully colonizing on the ‘second try’ as it were. Even if the collapse was all the way back to the stone age, and the rebuilding took another 10 000 years, it would still be, comparatively, a very short time on cosmic scales.
Only a collapse all the way to extinction would preclude the possibility of recovery.
There’s a paper on the lightspeed limit restriction on exponential expansion from a few years back which limited range to about 300 ly, in extremis, before collapse or evolution away from exponential growth.
The light cage limit to interstellar expansion
JBIS, Journal of the British Interplanetary Society. vol. 55 no. 7-8 pp. 279-284 July 2002
By Colin McInnes… http://www.mecheng.strath.ac.uk/staffprofile.asp?id=97
Means 200,000 exponential growth waves could have been and gone in the Galaxy without encountering each other or their debris. There maybe dozens of ‘graveyard civilizations’ littering the Galaxy. Kind of makes the cosmic morality of our economic choices stand out in stark relief. What we choose as a civilization determines if we become another statistic.
why the scientists are so hard to admit, aleast the possibility that UFOs could real solution for the Fermi paradox ?
that i think that could be a real possibility,and diserve be search by the scientific community.who knows what a very high tecnological advanced civilization are capable?
who knows why that such civilazation haven’t make a official contact yet?
why not,that such civilization already found a way to travel the vast distance between the star?
i’m not any ufologist but i think this could be a real possibility that diserve some respect,because we don’t know all about the physcical laws yet.
Hmmm… back when we were having the Cold War, the solution to the Fermi paradox was that the aliens would inevitably blow themselves up with nuclear weapons. Now we’re facing global warming, it’s because the aliens fail to manage their environment properly…
Is this really a likely solution, or is this another example of projecting ourselves onto the cosmos?
I suspect the answer is (b).
It’s an interesting paper, but disappointingly lacking in one key area. They discuss the issues of exponential growth and sustainable development in an Earth-bound context, but they really don’t really explore them in the context of an interstellar capable civilization or galactic empire. There are a couple of references in passing to the travel limitations imposed by the speed limit of light, but when you’re paper is proposing sustainable development and exponential growth then collapse as solutions to the Fermi Paradox, it would have been nice to see more discussion as to why these scenarios should be seriously considered.
The problem isn’t that scientists won’t admit the possibility that aliens have visited or are visiting Earth, it’s that the evidence being presented by the UFO community is so poor and so obviously riddled with fraud and pseudoscience. These people have proved themselves, time and again, to be unreliable advocates and thus don’t deserve to be taken seriously.
It may be that one day one of these people will be proven right, but I suspect that the scenario will play out in a very different manner than the usual sightings/abductions nonsense that’s normally put out by UFOlogists.
I was listening just a couple of weeks ago to some “expert” on Coast to Coast AM, and he was going into incredible detail about the history, motives and actions of both the aliens behind the UFO sightings and (of course) the US Government people involved in the supposed cover up. But it was clear to anyone with an ounce of common sense that he was simply making the whole lot up.
While I would love things to be different, there just isn’t any half-credible evidence for this type of stuff yet.
Miniaturization could be another answer: there is plenty space, when a civilization redesigns itself ever smaller and smaller.
I recently read about predictions from before the time of Moore’s law of future computers, that would solve all our problems and would need factory sized buildings and a power station. Reality went another way.
When I plugged my “best estimates” into the Drake equation, I got 1.
I know this is slightly off topic, but in the case of UFO advocates I knew one before he went off into “UFO Land” – Michael Salla. When I knew him he was studying still here in Australia, becoming increasingly interested in Peace studies and the work of peace-making activist groups. Apparently he has extended the hand of peace to all the ETIs routinely visiting planet Earth, some sixteen or so species which, in my mind, indicates the danger of taking UFOology too seriously. I read people like Timothy Good and others in the hope they’ll report what seems like an irrefutable encounter, but instead I come away feeling as though they, the writers and people like Michael Salla, have been conned. There’s a lot of attention-seeking people manifesting low-grade psychoses IMO who spin elaborate stories about aliens, their secret bases on Earth and Mars (usually) and the dark doings by the US government to cover it all up. I would feel differently if some real data was presented by such people, such as accurate astronomical information – for example a list of observable exoplanets around nearby stars – instead of the same old recycled truisms.
I feel similarly frustrated by the claims of modern religious revelation with one particular point illustrating my point. Modern revelations, like the material from Helena Blavatsky or the Urantia Book, show an eagerness to co-opt the findings of science, but never produce anything new. Blavatsky’s history of the Earth, for example, claimed it was a mere 18 million years or so old, fitting the calculations of Lord Kelvin to that effect. A few decades later the Urantia Book is “received” and gives a geological time-scale of hundreds of millions of years – BUT gives the old geological timescale before radiometric dating was refined. Both ‘revelations’ are dated because of this, like the short timescales of the Bible, the flat, geocentric Earth of the same, and so forth. While all such works may have spiritual insights, they’re not obviously messages from another Intelligence and likewise all the UFO material I’ve ever encountered.
Maybe there are alien probes and alien minds somewhere in the heap, but for sure the predominant alien intelligence revealed is that of our fellow human beings. We are a mystery to ourselves, let alone any ETIs who may be watching or whose Archives we might discover on some graveyard world around a nearby red-dwarf or stored in a beacon probe in our own system.
It could be that ETIs might not be around because their evolution outstrips their expansion. The article talks about the minimum length of time it would take for a speed-of-light limited diaspora to expand through the galaxy as about 600,000 years.
Well, just think how far we have come in that amount of time without the aid of advanced technology that is now on the horizon. Who knows what the human race will be like in another 100,000 years, let alone 600,000?
For example, we may find that the best way to cheat death is to download ourselves into artificial constructs (AI containers, if you will) and once we’re there, the cyberspace environment would really only limited by the ingenuity and imagination of the programmers. Any Matrix-like fantasy of your choosing (working for you, rather than against you) would be possible, and the real universe could easily pale in comparison.
There would be virtually no limit to the number of entities (people) that could inhabit a construct that would be far smaller than, say, the Moon, so there would be no longer be an urge to expand outward into the galaxy to find more living space. No doubt there would be some who remained curious about the wonders that may lurk in the far reaches of the Milky Way, but there would be little incentive to do anything but visit, observe and record and, perhaps eventually, interact.
Of course, this is just one scenario. Evolution (even technological evolution) may take many forms, and perhaps over a broad span of a half million years, a great number of those forms may preclude the need or even the desire for outward expansion on a massive scale.
ive read a theory about ETI which states that.. as life evolves, only the predators become more intelligent, not the prey. that would mean that intelligent life should have capacity for aggression, which lends support to colonization and war among ETI, as well as the possibility that those two processes wiped them out.
however, fermis paradox doesnt preclude ETI. a large civilization spanning part of the milky way galaxy would highly unlikely to remain undetected, but even a civilization around several stars could go unnoticed. and ETI that remains in its own solar system would be even harder to find. this is to say nothing of ETI possibilities in other galaxies.
still, im inclined to believe that ETI is rare.. the more advanced life is, the less common it should be. primitive life is probably widespread.. after all, life as we know it is made up of common elements like carbon, and lives on elements like oxygen, and these elements are in many places throughout the universe. life could even be based on different elements than ours.
“Some analysts are concerned that the unsustainable practices of human civilization could lead to a global-scale collapse.”
Yes, I pause in concern, but how close are we to the oft-mentioned a “global-scale collapse”? What signs are there that something this drastic is close to occurring? I am not saying that I don’t think it is possible that we could reach some kind of tipping point, but I wonder about the likelihood of our reaching it. Is there any strong evidence to suggest that humanity is uber-capable or in the process of out-doing all of the previous mass extinctions? The burden of proof, it seems to me, is on those who believe we are this powerful. Having said this, I think we need to be much more respectful/compassionate with the myriad living creatures with which we SHARE this planet.
Assuming we reach this momentous state of affairs, there have been many mass extinctions throughout Earth’s history and yet life has not only recovered from these harrowing events it has also flourished albeit in the form of different types of species. Now, although life may recover and even some of humanity may survive in this barren sad world of the future, we might be forced into living such a bare-bones existence solely focused on garnering whatever smidgen is left to meet our basic needs; therefore, galactic communication, let alone galactic colonization may no longer be in the cards.
My personal dream is for humanity to enter into a glorious era that I coin as The Era of, Restoration and Exploration. This era would entail not a perfect world, but a world with far less suffering, far more environmental sustainability, far better equality, etc. With many of our social problems corrected, the two main foci of human activity would be righting the wrongs of the past e.g. healing the planet’s wounds, giving back to creatures, and cleaning up our mess– hence the name Restoration. The other main activity, which is endless in scope and rife with challenge, would be moving out into the Universe in a big way– hence the name Exploration. I am reasonably young now, but I doubt I’ll live to see the beginning of The Era of Restoration and Exploration and I fully concede it may never come to fruition.
All the best, my friends.
We will not find a graveyard civilization or any other civilization for that matter. There is only the earth and our solar system, and us. The rest of what we see as the cosmos is merely a projection of light onto a screen. Without such projection we would quickly go mad from being confined to a cramped and boring little solar system. The creator provided this projection 6000 years ago during the creation of the world for the protection of our collective sanity. It’s in our nature that we need something mysterious to explore and to investigate but there simply was not enough space available in the universe to provide anything bigger than the solar system and the aforementioned screen and projection system.
I predict that in a few years the Pioneer and Voyager spacecraft will each make a dull “thud” as they strike the screen and fall to the floor of the theater.
And boy will the creator be miffed.
Global civilizational collapse as a result of unsustainable resource use is sóóó 20th century ;-)
But seriously, as others also argue, it is doubtful whether even such a collapse would be able to wipe our species out completely, rather just throw it back some centuries or millennia in development. It is a rock hard biological given that a species living beyond its carrying capacity will be corrected harshly by nature, in other words: some kind of (dynamic) balance is always reached, even if the hard way.
It is thinkable, however that humankind could be thown back in such a drastic way, that we would no longer be able to get beyond a kind of subsistence level.
However, more important is the notion, that it is likely and commonly assumed by astronomers that any civilization reaching the interstellar level (roughly equal to adapted Kardashev 2), will be almost indestructible, since it will consist of several or many autonomous and independent ‘islands’, each experiencing its own development and challenges. It is simply extremely unlikely that they would all be struck by the same fate.
It is possible that a civilization limited to one solar system will eventually be terminated by the end of the habitable lifespan of its star. As discussed in another thread, many sunlike stars in the galactic neighborhood are considerably older than our sun ánd, moreover, older than their own habitable lifespan (which is much less than the total lifespan). However, if such a civilization has not been able to save itself by moving to other solar systems, it is also unlikely that it will be able to leave behind long-lasting beacons.
With regard to UFOlogy, I wholeheartedly agree with Adam, but I do make an exception for physicist Stan Friedman.
I agree with Ronald regarding the unlikelihood of a total collapse of a galactic colony. As long as a colony is truly self-sufficient and stable, there’s no reason for it to automatically go the way of its parent colony. It’s easy to imagine scattered pockets of long-term survivors of a civilization now extinct on its planet of origin, cut off from each other and perhaps even unaware of each other’s existence. Transplanted, isolated civilizations of any significant age would have an interesting quandary, however. Because there wouldn’t be an evolutionary fossil trail for them to follow back in time on their host planet, their very existence could be attributed as “magical” somehow and give rise to belief in a divine creator who put them there, an ET Adam and Eve myth. While some ET scientists might speculate (correctly) that their planet was colonized sometime in the distant past, without solid evidence (preserved remains of the original landing vessel(s), an identifiable, readable captain’s log) this creationist belief would be hard to refute. How that might limit scientific exploration and advancement would be interesting to witness, especially in light of our own lengthy periods of stagnant scientific development due to misguided religious beliefs.
A clear implication of these ideas of constrained civilizations is that, should they survive their leveling-off phase, they will be thrifty. That’s why we Benfords wrote those two papers on the cost of beacons, to find out what the minimum cost could be. In turn that minimum dictates features of any cost-conscious beacon: broadband (~100 MHz), higher frequencies than conventional SETI reaches (~10 GHz) and pulsed, not steady.
If wise, constrained civilizations live for long times, they will need an equilibrium strategy, and may well outnumber the early, spendthrift societies. Ours hasn’t even reached the Bacon-building phase, so we should ponder how the adults might act.
tacitus i agree with you… i don’t believe in ufology ,for me ufology its not science,because ufology don’t use science methodogy to prove they cases… but some unexplained UFO cases derseve futher scientific inverstigation from the science community, maybe if take some of this UFO cases serious some truly science evidence would came out,of extraterretrial presence on earth.
I think graveyard civilizations is perhaps putting the question on the wrong footing. There’s plenty of potential for the galaxy to be riddled with the outsized refuse of astronomically advanced technological civilizations (some of which might be detectable by our current technology) without any need to presuppose civilizational collapse.
The drake equation and fermi paradox are, to my mind, more an indication of our gross ignorance about the nature of life and civilization beyond Earth than anything else. The fermi paradox says “by this calculation, they should be everywhere, including here, why aren’t they?” To some this raises the likelihood that “they” are not here, and not everywhere, and we don’t quite know why. But to me it reminds me of the fabled calculation that bumble bees cannot fly. This did not point to an inability of the bumble bee to fly but more to our own ignorance in understanding the nature of bumble bee flight (turns out, we now know how bumble bees fly, and it’s categorically different from the way a conventional airplane or helicopter flies).
To presuppose that we have any expertise in understanding the nature of interstellar technology, civilization, and colonization over time periods longer than the history of civilized mankind is presupposing quite a lot more than we should. We should look, and we should try to gather what evidence we can, but we should not imagine our knowledge extends any further than our observations (both of which are extremely limited in this area).
TL/DR: our ignorance outweighs our knowledge in regard to extraterrestrial life, technology, and civilizations by literally orders of magnitude. We should act accordingly and recognize that we know almost nothing about whether, how, why, where, and when extraterrestrial life exists/has existed, technological or not.
I think that the idea of extinct interstellar civilisations is complete nonsense. There is just no thing that would destroy an interstellar civilisation without us either noticing or being destroyed as well.
Resource depletion ? Are you kidding us ? There is so much free floating resources and energy in the universe. In fact, the bulk of the baryonic matter in our galaxy is resources and energy. And even if someone stripmined galaxy, we would see it. Missing milky way would be extremely hard to overlook.
War ? The fireworks needed to destroy an interstellar civilization would be seen far and wide. Not to mention the fact, that just a handful colony ships escaping into yet uncolonized parts of the galaxy would be enough to start the whole thing again. Galaxywide genocide would destroy us as well, so if we are there, there has been none.
Environmental degradation ? Of what ? Of interstellar vacuum ? there is only one thing that could make the vacuum even more inhospitable. Gamma ray burst. But such a thing would destroy earth as well.
Killer diseases/ biological warfare ? There is no better quarantine than several parsec of distance.
This is simply a non- answer to the fermi paradox.
As is nuclear war ( it would not kill entire population, even if we tried as hard as we could )
As is global warming ( it is an issue only on worlds in the closer half of the habitable zone, on more distant worlds it would actually make the more hospitable )
As is biological warfare ( there is no disease to which someone wpuld be not immune )
As is nanotechnology ( there already are molecular killer machines all around us trying to eat us as hard as they can, they are called germs )
As is resource depletion ( there is more than enough solar energy for our needs, if we start mass building solar powerplants in desert areas )
My bets on the fermi paradox are that we are among the first wannabe space travelers. Our sun has twice the metallicity for a star of its age. Which means, there is quite a chance that we are among the first, and most other planets are billions of years are still in their equivalent of archaean era.
Adam said, regarding Michael Salla, “Apparently he has extended the hand of peace to all the ETIs routinely visiting planet Earth, some sixteen or so species which, in my mind, indicates the danger of taking UFOology too seriously.”
Which indicates the danger of taking UFOology too seriously, extending the hand of peace or believing there are 16 species of extraterrestrials? Or is it both?
Exopolitics, to be sure, operates under some pretty amazing assumptions. But if we are indeed on the cusp of “full disclosure” by the governments of our planet as is being widely discussed in certain circles, is it not a very good thing that there have been people preparing for this day for some time now? I fail to understand how Michael Salla’s career serves as a cautionary tale since we have no idea what tomorrow may hold.
He and other pioneers in the field may be the Exopolitical “Zephram Cochranes” of our future.
And if all his ideas and effort come to naught should our first contact scenario result in our planet’s utter destruction or humanity’s subjugation to evil alien overlords, at least he had a plan.
amphiox: “There would be no a priori reason preventing the post-collapse survivors from rebuilding and successfully colonizing on the ’second try’ as it were. Even if the collapse was all the way back to the stone age, and the rebuilding took another 10 000 years, it would still be, comparatively, a very short time on cosmic scales.”
In principle, that’s true. However, our technological civilization has been stripping the Earth of all the easy-to-get resources for a couple of centuries. We are now at the point where we cannot even get to the new resources without prodigious amounts of technology.
If our civilization were to collapse, the remaining humans would have a much tougher job of rebuilding than we had. There wouldn’t be easy access to the petrochemical bounty that we have enjoyed.
About the only thing that could be said for those humans is that there would no doubt be lots of scrap tech lying around. Some of the more advanced stuff would probably not be much use, except as supply for raw materials. But the beefier stuff would be very handy.
Also, provided some modicum of knowledge survives, then any technical books that stick around will prove very useful.
Freya Borealis wrote:
I let this through because it was in response to a previous comment, but let’s not go any further in this direction. There are many UFO sites on the Internet, but Centauri Dreams is not one of them. This is a science site — we don’t do conspiracies — and we do need to stay on topic.
As has been mentioned in these comments, a good solution to fermi is that all ETIs experiment with simulated worlds (uploading into AI constructs) , and find this kind of life to be totally acceptable, and in fact so engrossing that the whole civilization (all individuals) migrates to simulated worlds before it expands through interstellar travel.
Long before ETIs (and humans) develop space-faring technology, they will be able to start experimenting with simulations, cybernetics, brain emulation through small offshoots from computation, medicine and biology etc – interstellar travel is a massive, long-duration side-project by comparison.
As the previous poster has noted, the simulated environments could be changed at will by users; however simulated minds would also have infinite plasticity. After a couple of centuries or so of this, do ETIs even have intellectual capacities to realize goals in this reality , like exploration and migration to other star systems?
also, interstellar travel times increase in terms of perceived time when simulated minds cycle faster (and faster as computation develops). . .
let us say the usa collapses, i.e “western civilization”. the survivors can mine the
garbage dumps for high quality and refined materials. there are those that say the usa produces nothing of value any more. WRONG! we produce the best garbage. but perhaps and just perhaps, it aint resource limitation. it may be a lack of sustainable organization. organization can fail from corruption and greed and folly. there is no limit to human greed and folly. i dont know anything about ETI but humans have a limit for social organization. i call i the money sphere. all here should do a web search for “monkey sphere”. briefly all primates have a social limit of “in group” members as opposed to “others” based on brain size. and…current events
demonstrate wars without end and misdirected funds. current events also indicate
mass killings and starvation. i am glad i live in an ivory tower. aint you?
Regarding the finding of the remains of civilizations, I wonder what we would
find when we do finally go star hopping, or what an ETI might find of our
society should it collapse and we disappear.
The answer might be not much, at least for things built by us. The book The
World Without Us and some recent programs on the same subject on the
History and National Geographic Channels, shows that most everything we
have built in modern times will be gone or buired within a matter of centuries,
though ancient structures like the Great Wall of China will last for thousands
Items left by us on the Moon and other nearby celestial bodies, plus the
few probes that have escaped our Sol system, will last for millions and
even billions of years, so those may be only remaining clues that we ever
existed – along with our transmissions both deliberate and accidental
that will sail onward through the Universe for as long as it exists.
It’s a fascinating question, isn’t it? I seem to remember a Jack McDevitt novel that goes into finding ancient ruins like this — does anyone remember which of Jack’s books this was? I know the subject has been treated often in science fiction, but Jack’s book must have caught me at an impressionable time.
See also my comment in the thread “Alpha Centauri Hunt Intensifies”: it is likely that there are (even) many more uninhabited but terraformable terrestrial planets out there than already inhabited ones, plus the fact that these do not pose any ethical problems with regard to indigenous life. These planets can constitute a huge and very attractive bounty of real estate for any advanced civilization desiring to spread and establish its own (adapted) lifeforms. These lifeforms are likely to stay and develop, even long after any civilization may be gone.
Therefore, I think that, once we are able to look for traces of lost civilizations in the galaxy, it might be much more effective to look for biological traces (such as remarkable similarities in genetic and biochemical make-up between planets) than purely technological ones.
I’m not really qualified in any way to comment but…
Just a quick point, linked to what Roland was saying that a civilization spanning more than a handful of star systems would, if it collapsed, presumable not collapse back to it’s original home system. It’s members would not all board ships and head home. So what you’d have is a civilization expanding to let’s say 100 stars, then if there was a general collapse presumably the population around each star would become isolated from the rest and regroup from there. Thus you then have 100 separate beginnings of a new civilization, and rather than one civilization regrouping and restarting it’s journey, you have 100 doing so.
This could go part of the way to explain the potential slow growth of civilizations rather than explosive growth, and seems much more in keeping with longevity. Kind of like it keeps on testing the boundaries, get’s pushed back, but not all the way to the beginning, then grows and pushes the boundaries again, get’s pushed back but not as far…. etc.
Further to Jeremy, I dare say that the longevity/survival chances of a civilization increase exponentially with the number of planetary systems settled.
In fact this is basic ecology: also on earth the extinction risk of a species decreases rapidly with increasing natural range. Which is one reason why rats won’t go away, while mountain gorillas ar on the brink (besides population size and reproductive rate).
An truly galactic species, and even more so an intergalactic species, must be next to indestructible. The only thing that could make it disappear would be the gradual change (evolution) of its constituent colonies themselves.
Ref. to Alex, Tacitus and others with regard to artificial life, uploading and the like, I have my strong doubts about this option, often mentioned nowadays. First of all, because it is an entirely unfounded idea (borrowed from SF), that we could upload our ‘minds’, ‘conscience’, etc., into a silicon based or other artificial (i.e. non-organic) material. It might wel appear that carbon-based life is indeed that: fundamentally dependent upon carbon molecules. Furthermore, it is equally unfounded that an intelligent species and advanced civ would sooner or later inevitably develop a longing for ever more (and more extreme) mental and simulated experiences. Finally, and maybe most importantly, I think it is a gross mistake to assume that miniaturization plus ‘minimal-energy-requirement’ would greatly increase the survival chances: the above-mentioned ecological concept (also related to the concept of island biology) is merciless: a small concentrated population is very (VERY) susceptible to extinction as a result of external factors, be it geological, climatological, cosmic (meteorites, etc.) or simply rat-equivalents gnawing the wires.
From a biological point of view I strongly believe in the imperative of risk-spreading through dispersal and isolation.
Once a society gets spread out through out a solar system, it should be quite “crash-proof”. A society spanning interstellar space should most certainly be crash-proof. I cannot think of a catastrophe that could wipe out a civilization that encompassed a region of, say, a 500 light year radius.
The resource consumption argument applies only to fossil fuels. The metals and other materials would still be around, just not in their original natural form. Aside from fossil fuels, no metal or other resource is actually destroyed in its use.
@kurt9: correct. A supernova explosion is supposed to be dangerous up to some 20 to 30 ly ‘only’, even a hypernova (extremely rare) up to a couple of hundred ly. That means, that if you plan your planetary colonies well, i.e. not too close to a super-heavy star, you should be ok. And these superheavy stars (>5 – 10 solar mass) are very rare in the galactic disk. For instance, my own survey of the nearest 70 ly (about 2000 stars) did not even turn out any O or B star, let alone bigger ones.
Resource depletion is indeed almost entirely limited to fossil fuels a perhaps a few rare metals and minerals. Most other things can either be recycled, mined in abundance, or made renewably from organic base materials. In the (near) future we’ll make more and more materials from organics, superfibers and so.
The only ultimate criteria is abundant energy. And of course water and carbon, in any form.
Jack McDevitt wrote so many books about this topic, some of them are Seeker, Ancient Shores, Deepsix, The Engines of God etc.. The main problem is that the author lost his focus in the middle section; therefore these novels are imperfect.
With all the problems humanity has in current space travel efforts, and the fact humanity is so conflicted among itself, the odds seem so much more bleak when viewing space colonization from within our own human perspective. Even if the alien beings are far more advanced than us, they will still face the tough challenges of just getting around in their own local region. Also, once those who made the journey have found new homes, they will likely settle, and then require a vast time period to regroup into a civilization that is again willing to hop about once again. I believe that vast “galactic” colonization is very much unlikely, and is most likely to be just a trickle before fizzling out of trace. If anyone tries it in our region, it will likely be us, and the odds are not looking up for us at this current page of the human story. At best we may someday colonize a single world that is in all likelihood different from our own Earth, so much so as to make colonization a harsh challenge at best. Whoever survives to the next generation will not likely have the means to simply say “oh this is nice, let’s go have another try, shall we?”… at least not for a very very long time!
“I seem to remember a Jack McDevitt novel that goes into finding ancient ruins like this — does anyone remember which of Jack’s books this was?”
It was The Engines of God.
“Once a society gets spread out through out a solar system, it should be quite “crash-proof”.”
A nearby supernova should effectively destroy such a civilization.