Recently, the local university and the local science center initiated a Science Cafe program here in Calgary. The science Cafe is loosely patterned after the Parisian Cafe Philosophique. In Calgary, people meet in an Irish pub downtown the evening of the last Tuesday of every month and discuss "scientific" topics. The discussion is introduced and led by two speakers who present their views on it, hopefully not identical. There is a moderator to make sure that things proceed in an orderly and somewhat civilized fashion (you might expect that to be a given, but this is an Irish Pub after all ;). It's a brilliant idea - at least, I think it is. However, I don't always agree with their definition of what science is.
I bring this up because I recently attended a Science Cafe entitled "Is There Anyone Out There?" discussing extraterrestrial life. It has got me thinking.
As was pointed out at the Science Cafe, I think most people who have considered the evidence would have a hard time believing that microbial life is not widespread in the galaxy. Heck, we're even still hopeful that there's non-terrestrial life in our Solar System. So the real question in need of an answer is "Is there intelligent life out there?"
Now, if you were to argue that there might not even be intelligent life right here, I wouldn't necessarily disagree. So we better settle on what we mean by intelligence. I propose we define intelligent species as those whose capacity to alter their environment develops on time-scales much less than their evolutionary time-scale. There is, of course, still a lot of interpretation needed - how is capacity to alter the environment defined, and what constitutes a development along those lines. But I think upon reflection this is an operational definition which works rather well for the question of identifying intelligence in extraterrestrial life forms.
Next, enter the Copernican principle, named after Copernicus. He was, or course, instrumental in pointing out that the Earth is not, in fact, at the center of the cosmos. His principal (which he did not propose) can be summarized as saying that it is usually a mistake to assume that what we observe around us is in any way atypical of what one would generically observe anywhere. It has obvious limitations, but is nonetheless very useful.
In the context of extraterrestrial intelligence, the Copernican principle suggests that if there is intelligent life on Earth, then intelligent species should typically be found on Earth-like planets wherever they exist. And since Earth is circling a rather generic Sun, the Copernican principle suggests that Earth-like planets should not be uncommon in our galaxy. So, the Copernican principle suggest that intelligent life should be ubiquitous.
It was the physicist Enrico Fermi who is credited with raising the question "If intelligent beings are so ubiquitous in our universe, where are they?" This is now known as the Fermi paradox. Let's speculate on the answers and see what we can find. I put forth a numbered list of possible resolutions I've come up with to the Fermi paradox and evaluate whether I think they are likely below:
1) It is possible that intelligent life is very rare, or possibly unique to Earth. In those few places where it exists, the intelligent life-forms apply the Copernican principle ( presumably locally named after the member of their species who was instrumental in pointing out that their planet is not at the center of the Universe). They conclude that intelligent life should be ubiquitous, and wonder at the Fermi paradox (presumably locally named after the scientist on their planet who first articulated wonderment that they had not already contacted other intelligent life-forms).
It seems to me unlikely that if life is ubiquitous that intelligent life would not be. There is an obvious evolutionary niche in any ecosystem for a species that can manipulate its environment very effectively. It is admittedly in all likelihood a very difficult niche to occupy - there are likely a number of very specific traits that all must exist simultaneously for a species to effectively manipulate it's environment on the scale we do. Free appendages, a large brain, and sensory organs that allow for complex communications are some of the obvious ones. I bet there are a number of less obvious ones as well.
But given enough time, a chance convergence of these traits seems inevitable. The only outs, then, seem to be that there is not usually enough time, or that there are no simpler lifeforms to evolve into an intelligent one. The second, as I said, is hard to believe given the evidence - organic compounds in space, our emerging understanding of how widespread self-organizing systems are, etc. The first is harder to rule out - all we can say is that there was enough time on Earth - maybe mass extinctions of large life-forms, which certainly have occurred periodically on Earth, generically happen on time-scales much less than those needed for intelligent life to arise on average. Maybe we are on one of the few planets which beat the odds. The main problem with this resolution is that it smacks of putting the Earth at the center of the cosmos again - we are the one-in-a-trillion winners of the intelligence lottery.
2) Perhaps intelligent life is ubiquitous, but interstellar distances are so large they can't be traversed.
It is true that without a "warp drive" casual visits between stellar systems on opposite arms of the galaxy are unlikely (incidentally, an untenable model for a warp drive has appeared in the scientific literature, perhaps a topic for future blogs). However, there seems to be no technical limitation that we are not close to overcoming in sending a colony to a nearby star. As this becomes feasible, it seems to me likely that there will be those who want to pursue it. A few extra-solar colonies will be established. Eventually, they will each establish a few colonies of their own. It actually takes remarkably little time to colonize a substantial part of the galaxy using with this exponential colonization. So distance does not seem to be the problem.
Furthermore, even if intelligent life does not spread out in waves of colonization throughout the galaxy, it is at least as technically feasible to build Von Neumann machines which spread through the galaxy as to colonize it. Von Neumann machines are machines that can replicate themselves from raw materials. Being more robust to space travel and longer lived than lifeforms, if we are any indication, it is likely that they could be programmed to spread throughout the galaxy much more successfully and quickly than their creators. By having each Von Neumann machine record environmental data and pass it's and all it progenitor's memories on to each new generation, and making sure that some of the Von Neumann machines make it back periodically to the system of origin, this would be a very effective way to survey the galaxy before starting to colonize.
3) Perhaps intelligent life is ubiquitous, but we are amongst the first few intelligent lifeforms to evolve.
Well, someone has to be first, but there is no reason to believe we are - planets as much as 8 billion years older than Earth have been discovered in our galaxy. Since Earth is "only" 4.5 billion years old, it is extremely unlikely that much older systems evolved none of these ubiquitous lifeforms much earlier than Earth, so much earlier that colonization has had plenty of time to happen.
4) Perhaps intelligent extraterrestrial life is ubiquitous and has been here, but it has come and gone.
If intelligent life is ubiquitous, why is it gone? Well, I guess there could be gaps between colonizations, and our ability to think in terms of extraterrestrial life rather than "gods from the heavens" is so relatively recent, that it could have happened. But there is certainly no convincing evidence of alien structures or artifacts on Earth (pyramids not withstanding). Considering the archaeological and paleontological evidence we have for indigenous lifeforms, a lack of evidence for extraterrestrials would seem to indicate an intentional withdrawal and removal of evidence. Given that ubiquity would seem to imply many successive waves of colonization, this uniformity of secrecy (or is it just good manners) is pretty puzzling. And what about those Von Neumann machines - are they cleaning up after themselves too?
5) Perhaps intelligent extraterrestrial life is ubiquitous makes regular visits - what do you think those UFOs are, anyway? Or they are here, living among us, disguised as people.
OK, I admit it - prolonged exposure to cheesy science fiction makes that hard for me to even contemplate these with a straight face. But they are legitimate proposals, so let's explore them. First, I think UFOs are "unidentified flying objects" of terrestrial origin. I do not think they are spacecraft from other stellar systems. The main reason I think this is the case is that I just don't see the upside to being secretive, but not that secretive. What are they doing? If they want to stay hidden so as not to influence our development (can you say "prime directive"?) then why can't they do a better job of hiding? If they are not hiding, then why not land in Time Square and say "Hi, and here's the cure for cancer", or "All your base are belong to us", or whatever it is they want to say to us? Or perhaps we are so primitive and insignificant compared to them and our planet is so commonplace or resource poor as to make it not really worth visiting, but in that case what the heck are they showing up here for? I just don't get the UFO angle. The living among us angle is even harder - why in the world would they do that for? To learn about us? We broadcast more than enough information about ourselves out of the edge of our solar system. To prepare for invasion? Come on, if they can fly here across the galaxy and disguise themselves perfectly as us, how much preparation can it take? Of course, it could just be that they are sooo different from us that we can't understand their motivations. Any of their motivations. Because, after all, they are ubiquitous, so there are many, many different intelligent lifeforms originating on many, many different worlds, all of whom are being mostly secretive but not completely secretive for reasons we can't understand. And, by the Copernican principle, since they are so alien to us that we cannot understand any of their many different motivations, they likewise cannot understand the motivations of one another. On Earth, when we have had similar but obviously much less pronounced situations involving human cultures (I mean, we are at least from the same species), things have not gone well. If there was ever a prescription for a scenario to practice complete avoidance, this seems like it. But perhaps I'm just not understanding them ...
6) Perhaps intelligent extraterrestrial life is ubiquitous, and it is here now or has been here in the past, but it is so different that we have no way of recognizing it, like beings of pure energy, or silicon lifeforms that take thousands of years to move an inch or something.
I read a book a while back by Cambridge paleobiologist Simon Conway Morris called Life's Solution: Inevitable Humans in a Lonely Universe. He considers the question of the likelihood of intelligence arising. His conclusion is that life is ubiquitous but that intelligent life is probably very rare - in other words, he does not adhere to the Copernican principle. I don't agree with this part of his argument. He goes beyond that, though, to consider what intelligent life could be like given what we know of the universe. He argues convincingly (at least, I was convinced) that it must be very like human beings. For instance, consider vision. Would other intelligences "see" the universe with eyes like ours? Well, given that using information about our surroundings gives a huge competitive advantage, and given that one needs to transmit some form of energy to convey information, and given that light from the star around which it orbits is the most abundant form of energy on virtually every inhabitable planet that would exist in the galaxy, and that light is an excellent conveyor of energy over long distances, it seems inevitable that "seeing" would be developed and preserved by complex organisms in every system. Further, Conway Morris argues using examples of convergent evolution that there are really no competitive designs for a "seeing" organ but the two that have developed here on Earth, the compound eye and the camera eye. So, it seems likely to me that were intelligent extraterrestrial life here now, or if there were some evidence of it left on Earth, unless it was intentionally hiding (see proposition 5 above), we would recognize it.
7) Perhaps intelligent extraterrestral life is ubiquitous, but it has no interest in colonization.
As stated in proposition 2, I think we are not that far away from colonization or launching a Von Neumann machine survey of the galaxy. With the former, we may discover that colonization is not so desirable as we envisioned for any number of reasons, either slightly before, or perhaps early into our colonization, and halt it. If we are even moderately enlightened, we might decide not to unleash our Von Neumann machines onto the galaxy too. However, if the survey is launched, it is difficult to imagine how we would stop it. So once we start, every intelligent life form that comes after us will likely know of our existence through our machines, either active surveying or shut down and rusting. It would be truly remarkable to me if everyone on Earth became moderately enlightened in the next couple centuries an therefore no nation, corporation or individual on Earth decided to launch such a survey. It would be a million times more remarkable if none of the (probably) millions of other intelligent life forms in the galaxy did so either.
8) Perhaps intelligent extraterrestral life is ubiquitous, but it has never survived long enough to colonize the galaxy.
Sadly, based on the evidence, this seems to be to be the most likely scenario. Based on our own history, it is quite possible that an intelligent life form's ability to alter it's environment grows at a rate that outstrips it's ability to understand the impacts of those alterations. The life form ultimately alters it's environment so profoundly as to make it's niche marginal (I think it is unlikely that we will extinguish ourselves on the first try - another possible blog). It then regresses technologically, perhaps adapting to a new niche, perhaps trying to recreate its original niche, and, if succeeding in either, presumably repeating the cycle by altering its environment to the point of making its niche marginal again. Some number of cycles occur before the species becomes extinct because it has moved the available niches so far from what it can actually occupy that it is no longer able to adapt. This scenario fits the evidence well - not only the evidence that we are altering our ecology at breakneck speeds, but it allows the Copernican principle to survive in tact without having to invent exotic reasons as to why we have not seen other intelligent life forms.
Ultimately, the question of "Where are they?" is much to complex for a bloganalysis like this, and probably too complex for much definitive to be said at all. Nonetheless, I'm drawn to it for one simple reason - if I extrapolate our current rate of technological progress, we are not that far (a couple of centuries) from being able to colonize other planets. That means others may have been capable as much as 8 million years ago. If they were, they apparently didn't. Either we are alone in the universe, as Conway Morris contends, or there is generically some reason that colonization never occurs. Given the number of colonizations that probably could have occurred, if the technology ever became feasible, it would likely have been used. Thus the technology must have always been infeasible. What could uniformly prevent intelligent life forms from developing such technologies? Likely only the one thing they have in common, their intelligence. That's my conclusion. What's yours?