by Dave Moore
Dave Moore, a frequent Centauri Dreams contributor, tells me he was born and raised in New Zealand, spent time in Australia, and now makes his home in California. “As a child I was fascinated by the exploration of space and science fiction. Arthur C. Clarke, who embodied both, was one of my childhood heroes. But growing up in New Zealand in the 60s, anything to do with such things was strictly a dream. The only thing it did lead to was to getting a degree in Biology and Chemistry.” But deep space was still on Dave’s mind and continues to be, as the article below, drawing on his recent paper in the Journal of the British Interplanetary Society, attests. “While I had aspirations at one stage of being a science fiction writer,” Dave adds, “I never expected that I would emulate the other side of Arthur C. Clarke and get something published in JBIS.” But he did, and now explains the thinking behind the paper.
The words from “Science Fiction/Double Feature” in the Rocky Horror Picture Show seem particularly apt after looking into the consequences of temporal dispersion in exosolar technological civilizations.
And crawling on the planet’s face
Some insects called the human race . . .
Lost in time
And lost in space
. . . and meaning.
All meaning.
Hence the title of my paper in a recent issue of the Journal of the British Interplanetary Society (Vol. 63 No. 8 pp 294-302). The paper, “Lost in Space and Lost in Time: The Consequences of Temporal Dispersion for Exosolar Technological Civilizations,” grew out of my annual attendance at Contact in San Jose, an interdisciplinary convention of scientists, artists and science fiction writers. From the papers presented there, I got a general feeling for the state of play in the search for extraterrestrial civilizations but never felt inclined to make a contribution until it occurred to me to look at the results of Exosolar Technological Civilizations (ETCs) emerging at different times. It would be an exercise similar to many that have been done using the Drake equation only, but instead of looking at the consequences of the spatial dispersion, I’d be looking at the consequences of different temporal spreads.
My presentation of the results and my conclusions went over sufficiently well that it was suggested that I turn it into a paper, but not having any experience in publishing papers, I let the project drop until Paul got to see my musings and suggested JBIS as a suitable forum.
The Separation Between Civilizations
The core of the paper is a table showing the number of ETCs you would get and their average separations assuming they arose at various rates from a starting point four billion years ago.
I used an idealized galaxy which was a disk of uniform stellar density, that of our solar neighborhood, to keep things simple. (For the justification of why this is a reasonable assumption and to why it seems quite likely that potential life-bearing planets have been around for eight billion years, I’ll refer you to my paper.)
One of the first things I realized is that the median age of all civilizations is entirely independent of the frequency at which they occur. It’s always approximately one-third the age of the oldest civilization. If ETCs start emerging slowly and their frequency picks up (a more likely scenario), this skews the median age lower, but you are still looking at a period of about a billion years.
And the median age of all civilizations is also the median age of our nearest neighbor. There’s a fifty/fifty chance it will be either younger or older than that, but there’s a 90% chance it will at least be 10% of the median, which means that in all likelihood our nearest neighbor will be hundreds of millions of years older than us. And, if you want to find an ETC of approximately our own age, say within a thousand years of ours, you will on average have to pass by a million older to vastly older civilizations. As you can see from columns 5 and 6 in the table, if ETCs haven’t emerged with sufficient frequency to produce a million civilizations, then you won’t find one.
Once you realize that ETCs are not only scattered through vast regions of space but also scattered across a vast amount of time, then this casts a very different light on many common assumptions about the matter. Take the idea very prevalent in a lot of literature that the galaxy is full of approximately coequally-aged civilizations (emerging within a thousand years of each other), a scenario I will call the Star Trek universe. If you look at the bottom row of the table, you can see there are simply aren’t enough stars in our galaxy for this to work.
After discovering that when dealing with extraterrestrial civilizations, you are dealing with great age, I then began to look at the sort of effects great age would have on civilizations.
Age and Power
The first thing I did was to extrapolate our energy consumption, and I discovered that at a 2% compound growth rate our civilization would require the entire current energy output of the galaxy (reach a Kardashev III level) in less than 3000 years, which doesn’t look likely unless a cheap, convenient, FTL drive get discovered. What this does point out though is that in extraordinarily short times, geologically speaking, civilizations can theoretically grow to enormous power outputs.
The next thing I did was to review the literature on interstellar travel. Many of the interstellar propulsion scenarios have power requirements that cluster around the 100 Terawatt level. This is a million times that of a proposed 100 MW nuclear powered Mars vessel, which is considered to be within our current or near future range of capabilities. Assuming a society with a million times our current power consumption would find a 100 TW vessel similarly within its capabilities, then our first interstellar vessel would be 700 years into our future at a 2% growth rate.
Are these energy levels feasible? If Earth continues its current growth in energy consumption, we will overheat our planet through our waste heat alone in the next century, never mind global warming through CO2 emissions. So, it looks as if we remain confined to our planet, we will probably never have the ability to send out interstellar colony ships. There is, however, a way to have our civilization reach enormous energy levels while still within our solar system.
Our solar system may have as many as a trillion comets and KBOs orbiting it, ten times the mass of the Earth, all nicely broken up. (There may be more comets in our solar system than there are stars in our galaxy.) And as this is the bulk of the easily accessible material, it would be logical to assume that eventually this is where the bulk of our civilization will finish up.
A hydrogen-fusion powered civilization could spread throughout our cometary belt, and with no grand engineering schemes such as the construction of a Dyson sphere, it could, through the cumulative growth of small, individual colonies, eventually build up a civilization of immense power and size. For example, if each of a 100 billion comets were colonized with a colony that used 1000 MW of power (a small city’s worth) then the total civilizational power consumption would be in the order of 1020 Watt. Pushing it a bit, if there was a 20,000 MW colony on each of the 5 trillion comets in the Oort cloud and the postulated Hills cloud, then the total civilizational power consumption would be 1023 Watt, that of a red dwarf star.
For this society, interstellar colonization would be but another step.
The End of a Civilization
Ian Crawford has done some analysis of galactic colonization using a scenario in which a tenth-lightspeed colony ship plants a colony on a nearby star system. The colony then grows until it is capable of launching its own ship, and so on. This produces a 1000-2000 year cycle, with the assumptions I’ve been using, but even if you work this scenario conservatively, the galaxy is colonized in 20 million years, which is an order of magnitude less that the expected age of our nearest neighbor.
Of course, all the previous points may be moot if a civilization’s lifetime is short, so I then looked into the reasoning advanced for civilizational termination.
Various external causes have been postulated to truncate the life span of a technological civilization–Gamma Ray Bursters are a favorite. When you look at them though, you realize that anything powerful enough to completely wipe out an advanced technological civilization would also wipe out or severely impact complex life; there’s at most a 10,000 year window of vulnerability before a growing civilization spreading throughout the galaxy becomes completely immune to all these events. This is one fifty-thousandth of the 500 million years it took complex life to produce sentience. So any natural disasters frequent enough to destroy a large portion of extraterrestrial civilizations would also render them terminally rare to begin with. If extraterrestrial civilizations do come to an end, it must be by their own doing.
There’ve been numerous suggestions as to why this may happen, but these arguments are usually anthropocentric and parochial and not universal. If they don’t apply to just one civilization, that civilization can go on to colonize the galaxy. So, at most, self-extinction would represent but another fractional culling akin to the other terms in the Drake equation. There’ve also been many explanations for the lack of evidence of extraterrestrial civilizations: extraterrestrials are hiding their existence from us for some reason, they never leave their home world, our particular solar system is special in some way, etc., but these are also parochial arguments; the same reasoning applies. They also fail the test of Occam’s razor. The simplest explanation supported by the evidence is that our civilization is the only one extant in our galaxy.
Into the Fermi Question
The only evidence we have about the frequency and distribution of ETCs is that we can find no signs of them so far. This has been called the Fermi paradox, but I don’t regard this current null result as a paradox. Rather I regard it as a bounding measurement. Since the formation of the Drake equation, two major variables have governed our search for ETCs: their frequency and longevity. This leads to four possibilities for the occurrence of Exosolar civilizations.
- i) High frequency and longevity
- ii) High frequency and short life spans
- iii) Low frequency and longevity
- iv) Low frequency and short life spans
These four categories are arbitrary, in effect being hacked out of a continuum. The Fermi paradox eliminates the first one.
We can get a good idea of the limits for the second by looking at an article that Robert Zubrin did for the April 2002 issue of Analog. In it, he postulated a colonization scenario similar to Ian Crawford’s but cut the expanding civilizations off at arbitrary time limits. He then found the likelihood for Earth having drifted through the ETCs’ expanding sphere of influence in the course of our galactic orbit. The results indicated that unless all civilizations have lifetimes of under 20,000 years, we are very likely to have been visited or colonized frequently in the past. But to have every civilization last less than a specified time requires some sort of universalist explanation, which is hard to justify given the naturally expected variation in ETCs’ motivation.
Nothing that we had seen so far eliminates the third possibility however.
Implications for SETI Strategy
Finally, in the paper, I turned to reviewing our search strategies for ETCs in light of what has been learned.
Given that ETCs will most probably be very distant and have a high power throughput, then looking for the infrared excess of their waste heat looks like a good bet. Low frequency but high power also implies searching extra galactically. Take the Oort cloud civilization I postulated earlier and assume it colonizes every tenth star in a galaxy like ours. Its total power consumption would be in the order of 1030 Watt. This would show up as an infrared excess of one part in 107 to 108 of a galaxies’ output.
I found other ideas like searching for ancient artifacts and using gravitational lensing for a direct visual search seem to have some potential, but when I looked at radio searches, this turned out to be one of the least likely ways to find a civilization. The problem quickly becomes apparent after looking at Table I. Any ETCs close enough to us to make communication worthwhile will most likely be in the order of 108 to 109 years old, which gives them plenty of time to become very powerful, and therefore highly visible, and to have visited us. If civilizations occur infrequently, as in the top row of Table I, then the distances are such that the communication times are in the order of 10,000 years. If civilizational lifetimes are short but the frequency is high, then you still have enormous distances. (You can use Table I to get some idea of the figures involved. The last two columns show the distances at various frequencies for civilizations within 1000 years of our age. For ten thousand years move those figures up one row, for 100,000 years two rows, etc.) Under most cases, the signal reply time to the nearest civilization will exceed the civilizations’ lifetime–or our patience. Looking for stray radio signals under the distant but short-lived scenario does not look very hopeful either. To send a signal tens of thousands of light years, an effective isotropic radiated power of 1017 – 1020 Watts is required, and while this is within sight of our current technology, the infrastructure and power levels are far in excess of anything required for casual communication even to nearby stars.
The results of all my thinking are not so much answers but, hopefully, a framing for asking the right questions.
Considerations in SETI searches have tended to focus on the nearby and a close time period and were set when our knowledge in this field was in its infancy. There’ve been some refinements to our approach since them, but generally our thinking has been built on this base. It’s time to carefully go over all our assumptions and reexamine them in the light of our current knowledge. The Fermi paradox needs to be explained — not explained away.
The paper is Moore, “Lost in Time and Lost in Space: The Consequences of Temporal Dispersion for Exosolar Technological Civilisations,” JBIS Vol. 63, No. 8 (August 2010), pp. 294-301.
Look for Dyson clouds. Billions of space habitats orbiting a star. This is what an advanced civilization should look like.
This article completely ignored the possibility that “technological but not technocratic” civilizations, using technology to solve problems but not treating technology as a value in itself, may be the norm. Such civilizations would not grow exponentially in power output, rather they would explore new kinds of physics to solve problems Earthlings restrict themselves to think of in terms of energy. Technocracy may be linked to self-destruction, but space may still be teeming with technoLOGICAL (just not technoCRATIC) civilizations.
@kurt9:
Not so sure about “Dyson clouds” or any other artificial structure for long-term habitation. Everything requires maintenance, and anything habitable in an environment as ferocious as vacuum will require a LOT of continuing maintenance.
Maintenance requires an economy to support it and the will to pay the price to keep it up. For a current example of infrastructure problems in an environment where air and water don’t need to be manufactured, have a look at: http://www.asce.org/reportcard/
Geoffrey A. Landis wrote a thought provoking article on this:
The Fermi Paradox: An Approach Based on Percolation Theory
http://www.geoffreylandis.com/percolation.htp
Hi Paul,
I published a paper in The International Journal of Astrobiology this past January titled “Temporal Dispersion of the Emergence of Intelligence: An Inter-arrival Time Analysis”. Check your archives and you will find I sent the article to you…just wondering what distinguishes Dave’s unoriginal article from my very original article? Google “temporal dispersion seti” and notice what pops to the top. Dave claims to have done a literature review on interstellar travel, well he should have also done one on temporal dispersion and cited my work.
One immediate comment: the idea that civilizations will not broadcast, by whatever means, just because distances are too large to communicate isn’t a very convincing one. The typical counter-example is the fact that we have lots of knowledge about the ancient Greeks, etc. etc. The point being that civilizations might consider transmitting no different than writing books to be read by future generations. Directly targeting systems with planets in their habitable zones, out to distances of thousands of light years, is a pretty easy technological problem, relatively speaking (since humans can just about do that now).
A paper that covers some of the same ground is “Temporal dispersion of the emergence of intelligence: an inter-arrival time analysis” by Thomas Hair in the International Journal of Astrobiology, Volume 10, Issue 2, 2011.
I have written several posts on this site regarding the time and distance question of ETC’s. This article by Dave Moore is without a doubt one of the best if not the best I have seen on this subject. It reflects my thinking and expands on it in a very intelligent manner. I thank Dave for his contribution and Paul for sharing it with us.
Frank I thank you for the link to Mr. Landis article, these two reads made for an interesting afternoon for me……..Tom
Thomas Hair writes:
Tom, I’m afraid I’m sent a huge number of articles and although I try to get to as many of them as possible, sometimes things get lost in the shuffle. Now that you’ve reminded me, I do recall (and have found) your paper and wish I had gotten to it at the time. Sorry about this oversight and would still like to write about your conclusions. I’ll let you and Dave discuss the rest of this back-channel.
Tom’s paper is Hair, “Temporal dispersion of the emergence of intelligence: an inter-arrival time analysis,” International Journal of Astrobiology 10: 131-135, published online February 25, 2011, with abstract here:
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8143571
Well, we can also imagine that civilization turn digital somehow in a Kurzweil’s technological singularity way. It seems very unlikely that such civs tend to expand and consume more and more energy. Why should they being rather some kind of sophisticated software than DNA based organisms? At the very moment you become Godlike creature that can comprehend the entire physics you simply stop to expand. There is no need to expand any more, or is it?
Enough with SETI and the Fermi paradox already! Please, people, let’s have no more speculation until we’ve got a few more facts under our belt. We haven’t even established whether there are any microbes on Mars, for goodness sake!
Although It is an enjoyable read, I find the article to be highly speculative, there is no information on how long a civilization can survive. Thousands to millions of years for a civilization to live, at this time, is unknowable. It also does not take into account increasing efficiencies of the technologies.
“It seems very unlikely that such civs tend to expand and consume more and more energy. Why should they being rather some kind of sophisticated software than DNA based organisms?”
Computers use a lot of energy – try turning off the aircon in a server farm and you’ll find out pretty quickly.
I would have had some trouble citing Mr. Hair’s paper. I submitted it to JBIS in October 2010 and received acceptance in late December 2010 pending some revisions. In January 2011, I was working on the revisions. Mr. Hair’s paper came out in February 2011. The issue of JBIS with my paper in it, dated August 2010, came out in July of this year.
Incidentally, I would agree with Greg that my paper is highly speculative, but I see the purpose of it not to provide answers but to help frame the question. They say half the answer is asking the right question, and I fear we have not been asking the right questions.
astronist errs on the side of caution. this is good. i read that viking did prove life on mars. i also read that sending sterile spacecraft there boost mission costs dramatically. to make missions economical sterilization was removed.
no doubt mars has microbes now, earth microbes. EARTH ATTACKS!
i also read of famous american politicians who derided SETI. it was cut to save money from the budget. now american politicians think nothing of spending billions on never ending wars without victory. do ETC do that also?
and what of finance? do ETC have money? does that curtail expansion of civilizations? what do financial leaders do on earth? hoard mostly. i have read of super yachts that cost millions of dollars. when the rich start building
private star ships of the one way variety, then i think the party is over.
m j sallberg’s comments are most enlightening. isnt it growth that will lead to our western civilization’s demise, i.e. technology for technology’s sake?
which leads to the question no one wants to ask or answer except by ridicule,
is there an advanced civilization on earth?
as to mathematical modeling…some one famous once said, “one sample is poor statistics”. and as another famous person said, “if you want to find something it best to start searching for it”.
we have no choice but to be parochial, for now. even our imaginations are parochial. how can we gain insight or second guess something (ETC) we have no knowledge or experience of?
Astronist, speculation it might be, but for many it is an enjoyable experience to consider such speculation. It costs almost nothing other than time and effort on the part of the speculator, which is wholly voluntary.
So why should we stop?
FrankH, Geoffrey A. Landis’ use of percolation theory to slow the expected timescale of galactic colonisation is an absolute classic. Unfortunately it is my understanding that, even holding rigorously to the assumptions that he makes, his model still fails if the position of the stars relative to each other change on anything like the rate that they must within a real galaxy. Judging by the reference that you give, this is a failing that he has never been able to address.
>Please, people, let’s have no more speculation until we’ve got a few more facts under our belt.
The purpose of speculation is not the answer(s); it is exploring, illuminating, and understanding the question in the confines of the whole language-concept-thought triangle we inhabit. If, and it is fairly likely this will happen, additional questions are generated in the process, all for the better. Now there is nothing wrong with data, some of my best friends are data-points and eventually we have to get down to the dreary business of collecting them, but an awful lot of useful thinking can be done in their absence.
@Rob Henry
If you are interested in colonization scenarios that take into account the drift of stars in the galaxy, I firmly recommend you get hold of Robert Zubrin’s Analog 2002 article: Galactic Society. It gives a very convincing model showing why we can’t have long lived civilizations in the galaxy and avoid the Fermi paradox.
It is not just about us
It seems to me that your model predicts vastly different outcomes for communications depending on the density if stars. The neighborhoods might be more active as we approach the core of the galaxy
We ARE parochial. what about the possibility of two civilizations ( not us) establishing communications? Once that occurs it is likely their whole approach to exploration might change . Once a small group of communicating civilizations are “networked” the system expands outward- either by expansion of the original civilizations into new systems, or by recruitment of emerging intelligence- depending on the density of civilizations and on the physics/ requirements of interstellar travel. The probability of any given civilizations contacting
another is as you describe ( if your assumptions are correct) but the probability of some contact occurring some where in the galaxy is a polynomial function of your calculated probability ( probably goes with the square of the number of civilizations)
the strong prediction is that there are civilizations already out there doing the interstellar “facebook” We need a broadband connection and we need to download the “app” to plug in. LOL
@Geoffrey Brent
certainly they do, but it doesn’t matter. Single computer uses finit amount of energy. If Kurzweil is right with his singularity argument computers that are fast enough will be able to simulate human brain and afterwards enhanced human brains and more and more upt to certain limit called singularity. If this limit is finite there is no need to expand any more. Such computers therefore are nondetectable for other, less advanced, civs.
Excellent article. I have always believed the problem lies more with our human-centralized impatience to “find idealized Star Trek aliens” than the simple fact we A.) are alone, or B.) the enormous spacial and temporal distances involved simply preclude a galaxy burgeoning with sentient lifeforms that mirror our own spatial-temporal frame.
I maintain we will find alien life, though not sentient, and will probably come across archeological evidence of another civilization long before we ever meet another alien species. You simply cannot ignore the time frame and spacial distances involved. Humans need to stop thinking in such limited and parochial terms.
Congratulations to Dave Moore on a most interesting analysis (and others working on similar approaches). The scenario based approach, utilising essentially the full spectrum of possible rates for the emergence of ETCs brings out very well the implications of deep time, when combined with the volume of space available
Meant to add…I thought the requirement for ETCs to be either exceptionally infrequent or for an almost universal process to lead to their extinction in a relatively short time to lead to a conclusion consistent with the ‘great silence’ very interesting indeed. I don’t see whay such an extinction process would be (that would operate with such a reliable result as would be needed). This leaves the two extreme end members of the possible solutions to the Fermi paradox, as far as I can see. We are either an astonishingly unlikely event or someone is choosing to ignore us
Why do civilizations have to colonize other star systems? This is always treated as a given. Perhaps the process is so difficult and unappealing that it is almost never done. Humanity isn’t colonizing the sea floor either.
This treatment convinces me that we ARE the communication of a highly advanced predecessor ETC. (I LIKE that acronym!) One hopes that our eventual expansion into the universe is thus guaranteed! Gardening anyone? EDEN now!
Meanwhile… the miracle of life must be appreciated by other expressions of that communication who are here to study us as part of their own curiosity concerning evolutionary processes in the expanding universe. One wonders after the successes and failures they might have found elsewhere/other times? Non-interference by those evolved entities a given? Hopefully we will evolve in a similar direction – with a little luck that is and the crik don’t overflow – again!
This related article discusses that if ETI visited Earth at ten randomly chosen times in history, there is no guarantee they would appear when human civilization existed to record them.
http://lablemminglounge.blogspot.com/2009/03/fermi-paradox-meets-timescale.html
Dear Max
the argument goes as follow
Assuming the systems are biological, then they must have evolved
Evolution involves both adaptation and speciation. As organisms evolve the move into new environments or colonize similar environments nearby. If they do not do this, then they are simply wiped out when their habitat is lost( which can happen in a few minutes or over geologic time, but it does ALWAYS happen
Thus species that do not have the ability and the drive to colonize hew territory do not survive. as intelligence evolves so does the need to colonize and compete. When technology arises, competition drives the species to broaden it range. If this does not happen there is no civilization – and we are chiefly concerned with the actions of civilizations . Thus- we are driven to colonize when some members of a species recognizes a new niche- that is why we humans will ( probably ) expand into the solar system. The biological imperative is the strongest drive we have as a species. That is also why engineered AI will always be beaten by evolved AI. It is why my great grandpa came to the US from Hungary, and why I read this blog. curiosity, conquest, kids and cash.. the big drivers.
Dave Moore I think that the saying “half the answer is asking the right question” is a gross underestimate in many situations, and to that purpose allow me the following personal anecdote.
From the time I was thirteen my father put a large advanced mathematics poster on my wall, and it endeared itself to me sufficiently that I retained it till my university days. One day I noticed there was still one puzzle on it that I did not know how to answer: the seven bridges of Konigsberge. It took me an hour, and when I found the method it was astonishingly simple and involved only logic. What struck me, is that for a long time no one could solve the problem, then suddenly I realised the solution was elementary once you are given the new perspective – in that case that a problem that looks so soluble might not be.
Thanks for the reference, though my limited Analog & Astounding collection does not contain it, I will hunt it down.
Having left a rather exasperated comment above about the sterility of all this debate about the supposed Fermi paradox when we can’t yet even find or rule out microbes on Mars, I find I’m now putting it into the paper I’m currently working on for JBIS! Love it or hate it, it seems the Fermi “paradox” just can’t be ignored!
Dave gets well to the point in this paragraph:
What is not sufficiently emphasized is that this simple point makes all the prior talk about spatial and temporal separation moot: If there is even just one civilization more than 20 million years older than us that colonized the stars, they would be all around us, today. Regardless of where in the galaxy they got started, temporally or spatially. The conclusions are clear:
Either:
1) We are alone, or
2) We will never make it to the stars, or
3) They are all around us.
In order of my preference….
I think there are two solutions to the Fermi Paradox which are the most likely explanations for why we have not encountered any aliens. The first, and this is mentioned quite often, is that intelligent life is rare, so that we are separated by great distances and are unlikely to encounter other intelligent creatures anytime soon. The second, and this is mentioned less often, is that we can agree that technological civilizations would have to be at least as intelligent as us, we are the minimum, to be detectable. How likely is it that civilizations evolved to exactly the same level of intelligence as us and stayed at that level? I say not very likely. So chances are they are much more intelligent than us now and so we can not hope to guess at a society like that’s motivations. It would be like a squid trying to understand what humans are doing with particle accelerators. Or even if ETIs were at our level of intelligence, at least initially, they are most likely millions or even billions of years ahead of us and still the case is as hopeless at trying to understand that sort of civilization. Just look at our own species a mere 15000 years ago. There is no chance that someone living 15000 years ago could have guessed what we would be doing now. Perhaps there are civilizations out there, doing things that are quite noticeable to themselves, but we just can’t understand what they are doing.
Well done, Dave Moore! (As far as I can tell from the article here at Centauri Dreams)
As always, there are considerations and objections (some are mentioned in comments made by others here), but I’m impressed by your approach of modeling a galaxy and seeing what consequences various assumptions have. This injects one more piece of very necessary realism. I even would not characterize your work as “highly speculative” — Dave, you are too humble (as some may remember, I talked against too much speculation on this site in the past, as I’m an advocate of — if you don’t mind the pun — down to earth science).
Something comes to my mind, when I read “an idealized galaxy which was a disk of uniform stellar density”. A refinement of Dave’s approach would be taking into account that the following facts cause considerable heterogeneities:
(a) the occurance of star factories as clumps with a lot of violence involved,
(b) destructions caused by novae and super novae,
(c) turbulances caused by collisions of galaxies (e.g. of the milkyway with its accompanying dwarf galaxies), and
(d) a galaxy having a restricted habitable zone (a minor point).
Okay, difficult. But as I know as a mathematician and as a developer of physics simulations we should expect heterogeneities like the above having substantial consequences (by the way, the same will be true for interstellar colonization, which, because of the above, will be much more difficult than some people think).
Tim Ferris the temporal Christmas tree of time and space
http://www.youtube.com/watch?v=hv-PlOq-6N8
Regarding colonization:
In the past, colonization has always been a result of political or economic pressure.
When political or economic pressure is taken out of the equation, humans will not colonize. There is enough land and resources here on Earth to ensure a quality life for all of its soon 9 Billion inhabitants. Population growth is expected to level off around 2050. I believe that we will spread into the solar system, but not for political or economic reasons. Curiosity will be the primary driver and we’ll probably have science stations on some planetary body before this century is out. But colonization? Unlikely. The Moon or Mars are hostile environments, much more hostile to life than Antarctica or the Gobi desert. Yet you don’t see large-scale human colonization of the last mentioned areas despite them being almost completely empty.
I do see humans crossing the gulf between the stars to satisfy their curiosity. But interstellar colonization? Extremely unlikely. Given the vast distances involved it is not realistic to assume extrasolar planets will act as a “release valve” for political or economic pressure here on Earth.
@Max: The point of colonization really is to get away. To start something new. Earth is now so thoroughly under control that settling Antarctica, deserts, or the ocean floor would be much like a survivalist camping trip in your backyard: Completely pointless, with the fridge a few steps away.
Colonisation happens at the frontier, and there is no frontier left on Earth. If getting away is the motivation, interstellar distances are as good as it gets.
You can write your own version of the Drake equation in Excel and put in numbers based on what we know about the number of stars in the galaxy and fraction having planets etc. All of this produces an optimistic scenario about how many ETC there are until you put in a time limit on the life of a civilization.
Suddenly, your average distance between them drops a lot. (my estimate is roughly 8000 LY).
What do we mean by time limit on age of a civilization? I do not mean that a civilization somehow dies as any sufficiently advanced civilization will get around extinction events. What I mean is “what is the time period in which we would recognize an advanced civilization” because a sufficiently advanced civilization is likely to be invisible to us. Consider that more than 120 yrs ago, we did not use radio at all but our tech is advancing exponentially. Do you think we will be broadcasting power in the EM spectrum as we do now 100 yrs from now? Consider spread spectrum communications, it looks like noise unless you know its there. I’d expect earth to become “dim” in the EM spectrum in a few years not because we are hiding but simply because radiating so much power is wasteful. if you can communicate with far less power by increasing the Signal to noise ratio, you do it. You’d probably not use a communication medium like EM that is so subject to “noise” from natural events, you might consider communication using neutrinoes or other things that interact weakly with the world of matter. It will be energy efficiency not a desire to hide that makes an advanced civ invisible to even nearby less advanced ones.
Any sufficiently advanced civilization will have visited lots of star systems and seen evidence of millions of now invisible civilizations. When you see an anthill in a cow pasture, how many do you need to look at before you have enough data to not need more. They do not visit because they simply have enough data already.
If a civ gets advanced to go faster than light, then the probability of them visiting gets even lower because this opens up the entire universe to them and may open it up temporally as well. With so much to see, the prob they will visit during the past 2000 yrs is very low.
I see no Fermi Paradox.
Max, you made an interesting point regarding colonization: “… Antarctica or the Gobi desert. Yet you don’t see large-scale human colonization of the last mentioned areas despite them being almost completely empty.”
First, I thought, yes, only a very small number of human beings live in deserts here on earth, why should someone want to live in the much more hostile desert of space. But then, I remembered having seen, that in Egypt indeed people “colonize” the desert. Starting at the borders of the cities, e.g. Cairo, more and more buildings are constructed in the desert; this process already goes on for several decades now (and not only in Egypt as far as I know), and it is indeed “large-scale”. What people get from the desert is ground, air and light — nothing else being there –, and everything else they bring with them.
A similar process for space would be, as others mentioned already, colonizing near earth space first, then the solar system. An obstacle: as long as there are much more “friendly” deserts on earth available …
Going further along this idea of how an advanced civ would be invisible to us:
We mostly use radio frequencies for communication, down to say wavelengths of about 1 cm. Using optical wavelengths in fibers or lasers would increase the data transmission rate by a factor of 10,000. Going to 10 KeV x-rays would get you up to 100,000,000 times higher data transmission rate and 1 MeV gamma rays would get you up to 10,000,000,000 times more. We would never see this.
There is one additional observational fact that is rarely taken into account: Our own position (us, today) within the temporal distribution of all human throughout history. From the principle of mediocrity, we should be rather typical: What are the odds that we live on our homeplanet, without any extraterrestrial colony, if humanity is to colonize billions of worlds (regardless whether these worlds are comets or planets) and thus have a total population in the many billions? Off course we might argue that we (us, today) are special, but arguments built up upon such an assumption are usually not very reliable.
This observational fact would imply that whatever the reason, lifetimes of civilizations are very short, on the order of a few 10’000 years. If that is the case, it doesn’t really matter whether the occurrence frequency of ETIs is high or low. Only a very small fraction may last long enough to survive into the deep cosmological future (or to have lived through today). So few that the galaxy is, at large, still pristine and untouched (in our era).
Any civilization inventing vacuum energy would lose all interest in exploiting energy resources, which may explain the absence of Dysonian structures.
@jkittle: If our ancestors had been competitive, they would have lived with motifs for deception all the time. If our ancstors had lived with motifs for deception all the time, indoctrinable individuals would have been exploited and selected against. Ergo, the fact that the majority of humans are indoctrinable proves that our ancestors did not have to compete against each other.
@Donald Kines: Real brains are based on statistics, not digital computation. All animals, including humans, must have statistical brains to survive in nature because nature is full of unplanned obstacles. Robots with statistical steering units can circumvent unplanned obstacles, robots with digital steering units cannot. With statistical brains, brainpower is not about processing many bits, but about precision, since the neurons are the “vote counting centrals” in the network. That means that in minimal brains, increasing brainpower has huge cognitive effct, but with more brainpower a further increase loses in effect, analogous to relativistic mass increase preventing acceleration. The fact that humans have such high precision they can conceptually discriminate to the point of being able to ask questions and investigate causes of faliure shows they are as close to infinite precision as to make no functional difference. That is why intelligence researchers can reduce general intelligence to mental age in humans but not in animals, and it also trunctates Arhur C Clarkes “apes or angels” thing with the fact that there is no angels.
@Max: There is a VAST difference between “theoretically possible to ensure a quality life (what a arbitrary term!) for everyone by strict resource management” and “free resources and not needing to worry for competition”. Staying on Earth only promises the former, while space colonization promises the latter. Having to worry for competition also leads to learned instrumental demonstrativeness, which is bound to create great injustices no matter how the societal system is arranged (think about the fact that former Soviet party leaders lived like capitalists) and competition also creates motifs for deception, which leads to exploitation of the indoctrinable population majority. Space colonization, on the other hand, means an abundance of resources and real estate, leading to a “I do not have to be demonstrative about power or property because there is abundant resources and real estate I can always reach anyway and with this easy space travel nobody can oppress me” mentality. What sounds best? Space colonization, of course!
Is there an arxiv preprint or similar? Google Scholar does not find this paper. Not for me anyhow :)
Unless everything that leaves the Sol system for the wider Milky Way galaxy and beyond is an Artilect, the first humans to move beyond our solar neighborhood will likely not be the noble NASA type astronauts but members of some religion/cult that want to be free of any Earth-based limitations by the rest of human society. Or political dissidents. Or even some kind of criminal element. Or perhaps a combination of all three.
Pure scientific curiousity will not be first on their minds, if at all, except in how it will help in their survival in deep space.
There probably will be a section of humanity that ventures out into the void for the sake of pure adventure exploring the unknown, but they will have to be part of a group of like-minded people with the necessary knowledge, resources, and funding to conduct and survive such a journey. Which leads us back to the cult scenario. And one can also add those who are escaping from some kind of natural or human-made disaster that affects Earth and its neighboring worlds.
Maybe I am just being too cynical. Perhaps things will get better in the future and we will have interstellar expeditions ala Star Trek. However, so long as humanity remains essentially as it has for the last few thousand years, I see individual freedom, personal and social safety, and even fear and greed as stronger and higher motivations for “missions” to other star systems as the first and strongest reasons for humanity leaving our Sol system over science and altruistic knowledge.
This can also apply to our primary reasons for colonizing the Sol system, just as Apollo was mainly meant to outdo the Communist Party of the Soviet Union over gaining scientific knowledge about the Moon. Even testing spacecraft engineering was given a higher priority over lunar science by a fair number of NASA employees involved in Apollo. If the main reason NASA and the USA wanted to go to the Moon was for pure science, robotic missions would have been able to accomplish much of what Apollo did, including the simple desire to physically reach Earth’s natural satellite.
To add to what I wrote above, if it is possible and even likely that our first interstellar “representatives” will not be a collection of shining astronauts or cosmonauts, then we should also wonder – at the risk of putting human traits on non-human intelligences – what are the true motivations for any ETI who might journey to the Sol system some day. While I do not envision them as the stereotypical invaders, such ETI might still inadvertently harm us in some way with their own personal intentions, for they would not come light years across space for nothing.
Or like the alien worldship in Arthur C. Clarke’s Rendezvous with Rama, they might only stop here to refuel and leave without any interest in or regard for humanity. Would it be worse for our collective psyches to be ignored by the rest of the Universe than anything else?
@Bynaus:
It would have to be fewer than one, because one is sufficient to take all pristinity (?) out of the galaxy, within a few short tens of millions of years.
@Duncan:
Very well observed. You don’t even have to go all the way to Egypt. Your comment reminded me vividly of once driving between Las Vegas and Los Angeles, where there are many people living literally in the middle of nowhere. Las Vegas itself can serve as a prime example of a vibrant settlement in an inhospitable location.
@Eniac
Thank you for the example of Las Vegas (by the way, from Europe where I live, traveling to Egypt is easier than traveling to Las Vegas).
Lets think a little bit further: Why do people settle in the desert?
In Egypt, as far as I can see, most people did it just because they have not been able to go elsewhere. In Las Vegas some people earn their living there, others have fun.
That’s *not* because of the cold war, religion, being criminal (yes, I know, there have been criminals in Las Vegas, but that’s like things are everywhere), or being scientifically curious. There’s hope ;-)
Most analyses of space colonisation hold the assumption that, at least for humans, it will follow if centuries of cheap and ready access to space are given. In order to uphold this, I believe that we must give a rather more robust explanation of our reluctance to colonise inhospitable regions on our own planet than those already give here.
It strikes me that the infrastructure costs of making barren land habitable cannot far exceed the benefit of spending the same resources on less marginal land. The fact that this condition has rarely been met on Earth suggests we are in need of extraordinary benefits for off-world living. Many benefits have been mooted but, none has been shown to be neigh inevitable.
Most worrying of all is that the bases in Antarctica are driven by a powerful combination of national prestige, science, and potential for long term economic gain. Many have been there for fifty years, and yet none looks close to such a degree of self-sufficiency, that they would be able to be maintained by enthusiasts without huge government subsidies.
To me the answer may be that, in order to maintain otherwise automated mining operations, a small community of expert extraterrestrial humans is an economic solution. Given the length of the supply lines, making these communities self contained would be a high priority.
Anyhow, we should spend more time on this problem than we do.
Hypothetical future space colonization is often compared to the colonization of North America by the Europeans from the 17th to the 19th century. Yet this analogy is deeply flawed: There is no “free land” in space, waiting to be colonized. The Gobi desert or Antarctica are cozy, hospitable places compared to the hard-rad vacuum of the Lunar surface or the frigid mega-desert we call Mars. Without a complex life support system, a human being exposed to these environments wouldn’t remain conscious for a minute and be dead in a few. The planetary bodies of our solar system are interesting and warrant our attention, but they aren’t viable targets for settlement. Limited living space would have to be created at an extraordinary cost. I think Rob Henry hit the nail on the head when he wrote that humans will only go a certain length to make land hospitable. When the required effort is too great, they’ll choose some place easier to live. That we aren’t colonizing the deserts*, Antarctica or the sea floor should tell us all we need to know about the economic and social viability of space colonization. Note that I’m talking about colonization, which implies people emigrating in large numbers with the intention of living permanently off Earth. I do think that we’ll see human activity on extraterrestrial bodies, but it will remain restricted to scientific outposts, mining operations and maybe tourism and be largely non-permanent in nature: A limited number of human specialists will be required on-site and be rotated in and out from Earth, similar to how things are run today in Antarctica.
The situation would be different if we had a habitable planet with a breathable nitrogen-oxygen atmosphere and sufficient gravity orbiting right next door and space transportation cheap enough so that people willing to emigrate could buy a ticket to go there without needing to have at least several hundred Million dollars on their bank accounts. But there is no such planet. And spaceflight is still in its infancy.
*There are vibrant settlements in desert regions, but there are almost always good economic reasons why they are there. Some developed along trade routes. Others are mining towns (commonly abandoned after the mine is depleted, unless its inhabitants find another opportunity to realize an income in order to buy goods to support themselves).
But nobody is moving into a desert for “land”. Nobody is proposing to set up self sufficient settlements in the Sahara far away from an oasis or river, which is what colonization of the Moon, Mars or asteroids would be like, just a thousand times more difficult.
One key advantage of space over inhospitable regions on Earth (or anywhere on Earth) is that space is practically infinite. I have already explained the advantages of practical infinity of resources and real estate. The really good thing about colonizing space is not any one location in itself, but the fact that locations and the resources in them are abundant and you can get/take what you want without having to worry about interest conflict (and with the lack of interest conflict comes freedom, since animal pecking orders are all about first-hand right to scarce resources and government is really no different from animal pecking orders). Cheap launches would be necessary to invent first however. I am already doing experimental progress with a technology for cheap launches and have ruled out the error sources most experimentalists fail to rule out.