When Arthur C. Clarke tells me that something is terrifying, he’s got my attention. After all, since boyhood I’ve not only had my imagination greatly expanded by Clarke’s work but have learned a great deal about scientific methodology and detachment. So where does terror fit in? Clarke is said to have used the term in a famous quote: “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” But let’s ponder this: Would we prefer to live in a universe with other intelligent beings, or one in which we are alone?
Are they really equally terrifying? Curiosity favors the former, as does innate human sociability. But the actual situation may be far more stark, which is why David Kipping deploys the Clarke quote in a new paper probing the probabilities.
Working with the University of Sydney’s Geraint Lewis, Kipping (Columbia University) has applied a thought experiment first conceived by Edwin Jaynes to dig into the matter. Jaynes (1922-1998) was a physicist at Washington University in St. Louis, MO. Through his analysis of probabilities (statistical inference was a key aspect of his work), Jaynes laid a framework that he analyzed with rigor, one that was later tweaked by J. B. S. Haldane, a man who had his own set of famous quotes, including the familiar “Now, my own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose.” This seems to be a day for good quotes.
Imagine a lab bench on which are a large number of beakers filled with water, roughly the same amount in each. The goal is to find out whether an unknown chemical will dissolve within these flasks. Remember, each flask contains nothing but water, all of it from the same source. You are to pour some of the chemical into each.
The logical expectation is that the unknown compound will either dissolve in each flask or not. That result should hold across the board: What happens in one flask should happen in all. What we would not expect is for the compound to dissolve in some flasks but not others. You can see what this would imply, that the tiniest variations in temperature and pressure could swing the outcome either way. In other words, as Kipping and Lewis note, it would imply that the conditions in the room and properties of the compound were “balanced on a knife edge; fine-tuned to yield such an outcome.”
Fine-tuning is telling us something: Are the conditions in the room so perfectly set that there is some kind of hair-trigger threshold that some but not all of the flasks can reveal when the chemical is added? How could that happen? Jaynes went about exploring this gedankenexperiment (and many others – he would become known as one of the founders of so-called Objective Bayesianism). The beauty of the Kipping and Lewis paper is that the authors have applied the Jaynes experiment, for the first time, I think, to the cosmos. Thus instead of beakers of water think of exoplanets, and liken the dissolving of the chemical to abiogenesis. From the paper:
Consider an ensemble of Earth-like planets across the cosmos – worlds with similar gravity, composition, chemical inventories and climatic conditions. Although small differences will surely exist across space (like the beakers across the laboratory), one should reasonably expect that life either emerges nearly all of the time in such conditions, or hardly ever. As before, it would seem contrived for life to emerge in approximately half of the cases – again motivated from the fine-tuning perspective.
Image: This is Figure 1 from the paper. Caption: In the gedankenexperiment of attempting to dissolve an unknown compound X into a series of water vessels, Jaynes and Haldane argued that, a-priori, X will either dissolve almost all of the time or very rarely, but it would be contrived for nearly half of the cases to dissolve and half not. The function plotted here represents the Haldane prior (F−1(1 − F)−1) that captures this behaviour. Credit: Kipping and Lewis.
The authors argue that the idea can be extended beyond abiogenesis to include the fraction of worlds on which multicellular life develops, and indeed the fraction of worlds where technological civilizations develop. Now we’re pondering a universe that is either crammed with life or devoid of it, with little room to maneuver in between. Which of these is most likely to be true? Can we connect this with the Drake Equation, that highly influential statement that so defined SETI’s early years in terms of the factors that influence the number of communicating technological civilizations in the galaxy?
Rather than extending the variables of the Drake Equation, a process that could go on indefinitely, the authors choose to distill it using what they call a ‘birth-death formalism.’ The result is a ‘steady state’ version of the Drake Equation (SSD).
The balance between birth and death is crucial. A civilization emerges. Another one dies. Think of the first six terms of the Drake Equation as representing the birth rate, while the final term, L, represents the death rate. The authors suggest that problems with the original equation can be resolved by paring it into this form, producing a new term F, which stands for the ‘occupation fraction’; i.e., planets with technological civilizations, a term arrived at through the ratio of births to deaths per year. Thus in the case of a galaxy filled with technological societies, F would come out close to 1. The paper fully develops how the new equation is reached but the end result is this:
Where λBD is the birth to death ratio. The particulars of how this is derived are fascinating, and can also be explored in Kipping’s Cool Worlds video.
Now we have something to work with. A galaxy in which there are few births compared to deaths is one that is all but empty. Start adjusting the ratio to factor in more civilization births and the galaxy begins to fill. Continue the adjustment and the entire galaxy fills. The S-curve is a familiar one, and one that puts the pressure on SETI optimists because it seems evident that not all stars are occupied by civilizations.
Assuming that F does not equal 1 or come close to it, we can explore the steep S-curve as it rises. Here NT refers to the total number of stars. From the paper:
This is what we consider to be the SETI optimist’s scenario (given that F ≈ 1 is not allowed). Here, F takes on modest but respectable values, sufficiently large that one might expect success with a SETI survey. For example, modern SETI surveys scan NT ∼ 103-104 targets… so for such a survey to be successful one requires F to exceed the reciprocal of this (i.e. F ≥ 10−4), but realistically greatly so (i.e. F ≫ 10−4 ) since not every occupied seat will produce the exact technosignature we are searching for, in the precise moments we look, and at the power level we are sensitive to. This arguably places the SETI optimist is a rather narrow corridor of requiring N−1T ≪ λBD ≲ 1.
That narrow corridor is the SETI fine-tuning problem. The tiny birth-death ratio range available in this ‘uncanny valley of possibility’ is all the room to maneuver we have for a successful detection.
And the authors point out that the value for λBD may be ‘outrageously small’. Just how common is abiogenesis? A telling case in point: One recent calculation shows that the probability of spontaneously forming proteins from amino acids is on the order of 10-77. And having arrived at these amino acids, it would still be necessary to go through all the further steps to arrive at an actual living creature. Not to mention the issue of producing living creatures and having them develop technologies.
Image: This is Figure 3 from the paper. Caption: Figure 3. Left: Occupation fraction of potential “seats” as a function of the birth-to-death rate ratio (λB/λD), accounting for finite carrying capacity. In the context of communicative ETIs, an occupation fraction of F ∼ 1 is apparently incompatible with both Earth’s history and our (limited) observations to date. Values of λB/λD ≪ 1 imply a lonely cosmos, and thus SETI optimists must reside somewhere along the middle of the S-shaped curve. Right: As we expand the bounds on λB/λD, the case for SETI optimism appears increasingly contrived and becomes a case of fine-tuning. Credit: Kipping and Lewis.
Thus the birth to death ratio cannot be too low but neither can it be too high if it is to fit our history of observations. The window for successful SETI detection is small, a fine-tuned ‘valley’ in which we are unlikely to be. To this point SETI has produced no telling evidence for technological civilizations other than our own (we do pick our own signals up quite often, of course, in the form of RFI, a well-known problem!) You have to get into the realm of conspiracy theories like the ‘zoo hypothesis’ to explain this result and still maintain that the galaxy is filled with technological civilizations.
We can also weigh the result in the context of our own planetary past:
Moreover, F ≈ 1 is simply incompatible with Earth’s history. Most of Earth’s history lacks even multicellular life, let alone a technological civilization. We thus argue that F ≈ 1 can be reasonably dismissed as a viable hypothesis…We highlight that excluding F ≈ 1 is compatible with placing a “Great Filter” at any position, such as the “Rare Earth” hypothesis (Ward & Brownlee 2000) or some evolutionary “Hard Step” (Carter 2008).
So what’s actually going on in those flasks on Jaynes’ lab table? Because if some flasks are doing one thing when the chemical is added and some are doing another, we may be precisely fine-tuned to where a SETI detection will be consistent with our previous observations. But that’s a pretty thin knife-edge to place all our hopes on.
I should add that the authors introduce mitigating factors into the discussion at the end. In particular, violating the SSD might involve the so-called ‘grabby aliens’ hypothesis, in which alien civilizations do emerge, though rarely, and when they do, they often colonize their own part of the galaxy. Thus most regions fill up, but not all, and we humans have perhaps emerged in an area where this colonization wave has not yet reached. That’s sort of intriguing, as it implies that the best SETI targets might be very far away, and extragalactic SETI may offer the best hope for a reception.
But let me end by questioning that note of hope, and for that matter, the issue of ‘terror’ that the Clarke quote invokes. Because I don’t find the idea of a universe devoid of other civilizations particularly terrifying, and I certainly don’t see it as one that is beyond hope. A Milky Way stuffed with civilizations would be fascinating, but a cosmos empty of other sentient beings is also a remarkable scientific result. So of course we keep looking, but the real goal is to understand our place in the universe. If we are a spectacular contradiction to an otherwise empty galaxy, let’s get on with exploring it.
The paper is Kipping & Lewis, “Do SETI Optimists Have a Fine-Tuning Problem?” submitted to International Journal of Astrobiology (preprint). See Kipping’s Cool Worlds video on the matter for more.
“The authors argue that the idea can be extended beyond abiogenesis to include the fraction of worlds on which multicellular life develops, and indeed the fraction of worlds where technological civilizations develop.”
I’ve been pondering this chain (abiogenesis to multicellular life to technological civilizations): the first link is subject to physical/biological laws, while the latter is emphatically not; that is, the first can be thought as subject to a kind of (predictable) necessity, while the latter, being necessarily social, becomes practically aleatoric.
On the one hand, the apparent conflation of these chains seems unwarranted, while, on the other, one need ask just how the rise of technological civilization is being thought.
But, essentially, is it a strictly, merely _statistical_ question, or do the matters of physical laws and social change matter _at all_ to the authors’ argument?
More thoughts on the matter at the website, below. But your thoughts on this question will be most appreciated/
Bryan Sentes’ musings and poetry can be followed at his Skunkworks site (https://skunkworksblog.com/) as well as Poeta Doctus (https://bryansentes.com/).
As to your question, Bryan, the authors explicitly argue that the statistical procedure they’re employing is valid across the range of astrobiology, including technological civilizations:
“This argument can be extended to other relevant astrobiology terms too, such as the fraction of worlds that are occupied with multicellular life, or technologically sophisticated species. As stated, the Haldane perspective seems persuasive, but perhaps a little qualitative and lacking rigorous justification. It’s also unclear what it’s implications really are to astrobiology, since all it really states is that the two extremes are equally likely – a lonely versus a crowded Universe.”
Have a look at the paper and the paragraphs following this one for more. Interesting stuff there on the weak anthropic principle.
So, with regard to my question “is it a strictly, merely _statistical_ question, or do the matters of physical laws and social change matter _at all_ to the authors’ argument?” I take it your answer is that the matter is merely or strictly statistical, a thesis whose grounds, admittedly, elude me, but that may be due to my weak acquaintance with statistics…
Nevertheless, I remain suspicious, as it were, of the conceptual investments underwriting this line of thought….
Mr. Bryan Sentes: you bring up a very important issue.
Replaying the tape of evolution, even from identical starting conditions, would likely produce widely divergent results with each replay of the tape.
There may be no ancient molecular cell biology formula that ensures even the appearance of eukaryotes from prokaryotes or even the prokaryotes themselves by stirring up the ancient elixir. Chaos theory and The Butterfly Effect may upset the apple-cart.
Robin, thanks for your comment.
Indeed, abiogenesis remains a problem, however many very ingenious solutions have been offered.
With regards to this paper’s argument, I’m curious how much purchase criticisms of such sort have in relation to the probabilistic argument being developed; my grasp of statistics is just too weak to know.
More acutely, however, my concerns orbit the concepts of “intelligence” and “technological civilization,” which in this field _tend_ take a minority of one society on earth (that of so-called “advanced civilizations”) as exemplary. In the case of “intelligence,” scrutiny and reflection explode this identification; in that of the latter, certain _ideological_ investments come into view–these claims are developed much more at Skunkworksblog…
The Haldene perspective is qualitative and lacks rigorous justification. We can always move between the outcome of few or most transitions by adjusting the description of the starting population. Adjust the description of Earth like planets until all of them have life or intelligence. This isn’t a huge problem though since it reinforces the role complexity plays in transitions. The population of each transitional state depends on the overall complexity of the environment and the requirements for a transitional state.
In a universe of finite resources and conversion loss through entropy, “trivially extending limits” is absurd. The time spent at F1 is dependent on occupation fraction. Bacterium that multiplies to fill a petri dish will eventually exhaust resources and F must become negative. Conceptually, the occupation fraction can be set high enough where Time at F1 is measured in eye blinks and F0 is infinite. I don’t know how to avoid occupation fraction being inversely proportional to Time spent at F1.
There is no evidence that evolution prefers traits that maximize carrying capacity or particular lifestyles, combinations of traits. The prediction that space faring people will choose lifestyles that maximize population is not based on evidence or evolutionary theory.
The physicist isn’t wrong, the dairy farmer has a fine tuning problem. But there is also no such thing as a perfectly spherical space faring people.
“There is no evidence that evolution prefers traits that maximize carrying capacity or particular lifestyles, combinations or traits.”
I would suggest that there is no evidence that evolution even favors intelligence. While evolution has favored hominids that are intelligent up to our current era, unfortunately intelligence might be a trait that ultimately is self defeating. Only time will tell. And since another 4 billion years will pass before the sun expands to annihilate the Earth, there is a lot of time yet to come.
The brain-to-body mass ratio has consistently increased throughout evolution, as shown in the vertebrate lineage. This implies increasing intelligence.
Brain–body mass ratio
The only evolutionary tendency we see is for increasing metabolic complexity and scale. Brains have been a successful adaption because bodies require internal monitoring and regulation. As bodies, the environment and lifestyles become more complex the brain must also become more complex.
I think that their argument suggests that technological civilizations are fine tuned. How many times could one have arisen on Earth? Probably many times in the 243 million years since the Triassic. If you are generous, it took humans roughly 1 million years to do this, so this suggests there were hundreds of trials, and only one success. In other words, “the birth to death ratio cannot be too low but neither can it be too high if it is to fit our history.”
While I actually am fairly optimistic on the occurrence of life in localities which got liquid water.
I do not view that as an automatic path to complex life in any form, only microbal organisms managing to hang on in environments without light and with none or miniscule amounts of oxygen which would allow for complex and active organisms.
Even on Earth which got both, it took roughly 3 billion years to go from the microbal stage to more complex organisms.
And even when the Earth life had gotten to sexual reproduction and multicellular organisms, it still got stuck at about the same stake and nothing noteworthy happened for an additional 1 billion years until the Cambrian diversification.
But that nearly came to complete end twice at the Permian and Ordivician extinction events. (The Cretaceous / dinosaur extinction is actually a mild one in comparison.).
During the Permian–Triassic extinction event 96% of all species got wiped out. Life probably cannot be completely eradicated by such an event. But we actually don’t know. yet it’s easy to envision a situation where such a reset would send life back to a pre Cambrian stage where it then get stuck again without another diversification event happening. In short we’re incredibly lucky to be here at all!
So do SETI Optimists Have a Fine-Tuning Problem?
Definitely!
There’s possibly millions of worlds, moons and planets with water oceans that could have microbes but never will provide an environment able to develop anything similar to a warmblooded civilisation building creature.
So yes, I firmly believe in aliens, but it will not be telescopes, but a microscope to find them!
Do we really know that technological life did not evolve on Earth before us? It is true that nobody has found unambiguous artifacts of such a civilization, but how much would actually survive on the Earth’s surface intact from tens or hundreds of millions of years ago? And we have no idea what is under the Antarctic ice. This is the basis of the Silurian Hypothesis. What if the “greys” sometimes seen in flying saucers left Earth when Antarctica froze over, and today have low population colonies scattered at hidden underground locations on the moon, throughout the solar system and nearby star systems?
This one’s easy. Go look on the Moon. If there was a previous civilization on Earth, they would most certainly have gone to the Moon. Solar wind erosion is slow enough that identifiable artifacts should last for millions of years. The asteroid belt and outer solar system would be good places to look for artifacts as well.
The problem I have with “empty Cosmos” arguments is . . . us. Here we are! We know life and technological civilization are _possible_ because the Universe has produced David Kipping.
The difficulty is that 1 is a very strange number. Science doesn’t deal well with a sample size of 1. It’s also hard to imagine the extremely fiddly fine-tuning necessary to create 1. So much easier to make 0.
If the Cosmos really is empty except for us, then that does make it rather plausible that Someone decided to bend the rules and make life happen here. (Though that raises the question of what the Creator wanted the _rest_ of the Universe is for.)
I’m still sticking to “insufficient data.” All we really know is that we haven’t recognized any signs of life or intelligence in the small portion of our own Galaxy we’ve examined in any kind of systematic way. There’s a lot of room between that and an empty Cosmos.
The rest of the cosmos is there to make our existence plausible. If p is the chance of spontaneous abiogenesis, then it becomes plausible as soon as there are 1/p “flasks”. The enormous size of the cosmos gives us an idea about how small p can be while still keeping the N=1 case plausible. That is: really, REALLY small.
To top things off, we seem to be caught in a state like Tantalus, reaching out in many directions, trying to address whether even life is unique to “here”, or whether it abounds or whether it was recently largely erased on neighboring worlds. Just how much of life’s essence through space can be transported… Individually or collectively, how could we “all” be born or come to consciousness in a brief era that can even appreciate such issues?
It would appear possible to resolve much more within a generation or two with the mechanisms of research we have constructed thus far. But in a way that seems like an oddity of our situation too. Move over Faust.
If we are alone, then even in that there are degrees. The very strict interpretation of that is that “randomness” is entirely responsible for our existence and our ability to have this discussion 13 giga-years after the cosmic ball was let loose to roll. That for every gazillion entropic processes working toward “disorder”, there are a certain number of processes heading in the other direction. And we are the beneficiaries – for a moment. “The thought of it” is just entropy in reverse, right?
Or maybe there actually is some validity to the rise of certain other forms of complexity stemming from fusion products such as carbon atoms, etc. and that these processes have consequences that might be of benefit to regions beside this particular place and time where we have this discussion. Other universes, if they exist could be tuned differently, for example, More friendly or more hostile to a development like ourselves. After all there are more ways to construct a cosmos hostile to such as us as there are to design them friendly. but this one has some life and consciousness friendly features built in. How friendly we do not know exactly since its got so mechanistic physical processes to begin with… Which sets up the question: Would the same people that worry about the rise of artificial intellect from circuits and data structures dismiss biological alternatives to us elsewhere or in time?
Present day research leaves us much akin to the mail recipient with a box announcing a lottery introduced with claims that “You may already have won.” Well, we have the packet, and we are alive,,, But we discover we still have to enroll in the sweepstakes. Increases the recipient’s chances at the jackpot, as it were.
In this case, we can also dismiss the enterprise in disgust – or continue our investigation with high hopes. There are still a number of interesting leads…
This way we will all be too busy in the dark to be terrified.
In the video, Kipping conflates life and ETI, until the very end. SETI is only looking for ETI. OTOH, there is now a focus on looking for life (or any kind) from, unicellular prokaryotes to ETI.
I don’t buy the argument that life is in the valley of fine balance. Life is an emergent property. natural selection even works at the chemical level if autocatalysis or metabolic chains/cycles spontaneously emerge with enough reactants. Unless there really is something special about Earth, then I would expect life to be ubiquitous wherever conditions allow it. The galaxy should be relatively full of life, even if very simple.
Technological civilization is a very different matter and in our case, highly path dependent. Evolutionary accidents have led our species to be able to be technological. Even so, since our emergence, it required a “cultural explosion” to set us on teh path to civilization, and from that eventually to a culture that discovered a way of thinking that led to the rapid growth of technology to where we are today. This may be a very rare event indeed. The galaxy could be littered with pre-technological species from microbes to animals able to chip stones, harness fire, and even manage to construct buildings, but have stalled at that stage as so many prior terrestrial civilizations managed before disappearing.
The search for life seems perfectly reasonable and I hope that our technology finds evidence around other stars. Civilizations that have advanced technology that might be detectable, may be a long shot indeed. However, a galaxy, a universe full of life, would be fascinating indeed, and a good start on understanding the constraints and probabilities of the emergence of different biologies and phenotypes.
What should be terrifying is our exploitative nature. If we can, we exploit every resource within reach. Unless or until we change, it might be better if we cannot reach the stars.
You raise a very good point. Simple life must be much more common than technological life – even going by Earth’s own history. Earth had single celled life for about 3 billion years, multicellular life for about 500 million -1 billion, a technological civilization for thousands, and a radio broadcasting civilization for about 120 years. That means we have been directly detectable for about a 4 x 10-8 fraction of the time when Earth had life.
The time it takes for something to evolve depends on the rate of evolution and is not a good indicator of probability of it evolving or not. The rate of evolution increases over time, as innovations occur that speed up evolution itself. Chromosomes and sexual reproduction are two examples of this. Once you have self replicating organisms, you’re on an ever accelerating trajectory towards increased complexity that cannot be stopped.
@Eniac
Evolution is also path-dependent. If the first phyla with a notochord had become extinct, there is no reason to believe that it would have reappeared again, as we know that the vertebrate lineage traces back to a single ancestral form. If vertebrates became extinct, no matter how fast evolution, there is very little likelihood that a new vertebrate lineage would appear.
This is very different from the evolution of eyes that have been independently evolved many times, even the type of eye that we have evolved separated in vertebrates and mollusks.
That’s very interesting, thanks for pointing it out, Alex. Still, in my opinion, there is also no reason to believe something similar to vertebrates would not have occurred again, eventually. Nor is there reason to believe the vertebrate body plan is the only one capable of producing advanced intelligence.
None of the other lineages have produced advanced intelligence in 500 + million years.
Computational experiments show that complexity/specialization cannot be unwound. Evolution effectively traps the genotype/phenotype at the peak of its local fitness landscape. It will eventually be replaced by a less complex/specialized organism as the fitness landscape changes. IOW, it is very unlikely that other lineages will be able to evolve vertebra. One caveat is that lineages that appear to have 2 life stage forms appear to have their motile form more closely related to our ancestral lineage. So just perhaps that motile form might be able to evolve a vertebrate form if the niche opens up and it can shuck its sessile stage. A big if, but who knows given enough time and a changed biosphere?
One aspect of path dependency for humans to have achieved a technological society, might be the ratio of personality types or talents.
It might only take a minor shuffle in the statistical frequency of human genes to get a society that produces far more Shakesperes and Picassos and far fewer Einsteins and Teslas. The effect could be self reinforcing, with that society producing a far richer artistic culture than ours, while any of us STEM types being perceived as very odd ducks indeed.
I don’t think so. Nurture/culture plays a role. Anecdotally, I know of at least 1 person who was clearly artistic all the way through high school, then switched, and did very well in neuroscience.
We are highly adaptable. Think of the many people who went into “banking” because of the attractiveness of the remuneration, but hated the job.
The US stimulated STEM interest in the 1960s with the space program.
In my opinion, nature is not so important in this regard.
@Alex Maybe this exploitive nature is the filter that could explain the Fermi paradox. No species with this nature will ever get past themselves, never mind becoming a space faring species. It’s also not surprising that we aren’t being (obviously) visited now, given how dangerous we are, to ourselves and every living thing on the planet. The other answer is of course there aren’t any to come visiting but I wouldn’t go that far. I recently read an interesting article about Avi Loeb’s controversial idea that we have in fact been visited. Here is the link if interested: https://www.scientificamerican.com/article/astronomer-avi-loeb-says-aliens-have-visited-and-hes-not-kidding1/
You could argue that the greater the level of complexity embodied in a species the less likely that species is to arise. I agree with those who say single celled life will be very common (a few percent or more of the total number of possibly viable planets, moons etc.), multicellular life will be less common requiring much longer to evolve (tenfold or more less than unicellular), and sentient tool users much, much less common (a few thousandths or less of one percent of all available niches). So sentient tool users are very, very rare. We may never find any. I wouldn’t be at all surprised by this even given the possibility of them trying to communicate with us and/or we them given the vast variable known as Time. We should be able to find unicellular ET fairly easily in comparison or evidence that it did exist in the past. I won’t be at all surprised if we find evidence of past or present microbial life under the ground on Mars for example. I think this falls within the range of what the authors are suggesting here doesn’t it?
Yes, I think this fits well with the conclusions of the paper, Gary.
While we can’t possibly know for sure, it’s not unreasonable to imagine that sentient life, at least, requires a fine balancing act – a combination of processes that are both nurturing to life yet disruptive enough to trigger evolution.
Examples might include:
A planet with volcanic activity to bring necessary minerals to the surface – but not so active as to destroy any evolutionary niches as fast as they appear. Plate tectonics might also be a requirement to supply sufficient change in available ecosystems over time to promote evolution.
A planet subject to an occasional meteor strike to shake up the ecosystem, but not so often as to destroy all burgeoning life. Which might suggest the need for gas giants in the outer solar system.
Tidal system to provide sufficient mixing of ocean depths, possibly implying to need for a large moon or moons.
I’m sure other contributors here can come up with many other examples.
Personally I’d almost prefer a cosmos devoid of other life… or at least other contemporary life, so there are plenty of archaeological sites to explore and learn from.
I think multicellular life and even sentient tool users are an inevitable consequence of evolution. If not us, it would have been one of the other hominid species. If not any hominids, it could have been cetaceans. Or cephalopods. Etc. etc. Multicellular organisms evolved 13 or 14 times independently that we know of. Similar arguments hold for any “barrier” to evolution that you could come up with. I am convinced that the real and vastly dominant filter is the step from 0 to 1, i.e. dead chemistry to evolving life. The first self replicating organism that didn’t die out right away.
@eniac
Evidence of single celled animals appears very early in the fossil record, almost as soon as the earth cooled off from its formation. This suggests (but does not prove) that microscopic life is almost inevitable. Multi-cellular organisms arose about a half-billion years ago which suggests (but does not prove) that complex life is the bottleneck. As for sentient tool use, who knows? It took half a billion years for projectile points and fire to show up, is this typical? Is it even necessary?
Intelligence may be a freak event. Even if it isn’t, use of tools and language may be a freak event. And even if it is common, a technology capable of communication or travel across light years may be extremely rare, if not impossible (except for us).
Our conjecture and speculation on biology appear to be on much more solid ground than that about intelligence.
I consider the idea that life must be common because it arose early a fallacy.
“Early” is still 1-2 billion years, depending on how much credence you give to reports of early microfossils. Microfossil interpretation is quite speculative, and the incentive to discover the earliest fossil is tremendous.
Furthermore, given that life does exist on Earth, the simple requirement that billions of years are needed to evolve to today’s complexity explains why it happened early. It says nothing about how probable it really is, because the probability of life arising, conditional on it existing today, is 1. The prior probability of it arising at all could be infinitesimally small, and most likely is. We have absolutely zero evidence to constrain that, except by speculating about the probability of abiogenesis, such as the 10^-77 number Paul mentions.
@Eniac
Actually, no. There is genomic evidence that ancestral cells existed within 200-300 my of the formation of the Earth after the Moon was formed. This is remarkably fast. Henry is correct that unicellular organisms appeared early, although there are other lines of evidence supporting this than microfossils.
Genomic evidence begins at LUCA. Genomic time estimates are not very accurate. Especially near the root of the tree. LUCA could be as young as 3.6 billion years ago.
I hope you will be back when I post about that very subject. ;-)
Yes, and that post is coming up pretty soon now.
There is another interesting way we could estimate the probability of abiogenesis:
The only thing we really know is that life arose at least once in the universe. If we apply Occam’s razor and postulate that the universe is not bigger than needed to explain this observed fact, we obtain the probability of us evolving on a given planet as the inverse of the number of planets in the universe. Thats a VERY small number. Taking inflation into account and the resulting vast unobservable universe, it could well be smaller than that 10^-77
This discussion caught me in the midst of a house/office cleaning exercise, trying to decide what to do with a vast collection of AAAS Science hard copies. Scanning interesting articles defers a final decision. Now and then articles related to our discussions pop up. Take this one:
Of course, some might be well versed in these matters and the episode. But at the very least, it should illustrate details of the terrestrial “ascendance of life” scenario that exoplanet life’s ascent would need to provide a parallel path, easier or more difficult, or else perhaps even transcendent.
“Geochemistry – A Shot of Oxygen to Unleash the Evolution of Animals”
Richard Kerr, Science, Vol. 314 , 8 December 2006 p 1529, Vol 314.
1st Paragraph:
“All animals need oxygen, but they haven’t always had enough of it to reach their full potential. Earth developed a trace of oxygen – at least in the atmosphere – more than 2 billion years ago. That was just before the appearance of sophisticated cells called eukaryotes in the fossil record. Ekaryotes went on to give rise to animals, but not until about 575 million years ago. Why the wait? For half a century, paleontologists have speculated that only then did oxygen levels rise high enough to support large, active cratures.
The evidence for such a jump in oxygen, however, has been sparse and indirect.
2nd:
“Now the theory’s proponents can breathe easier. In two papers published this week, researchers present geochemical and isotopic evidence that substantial amounts of oxygen first reached the deep sea 580 million years ago. In one place, the gas seems to have arrived there just 5 million years before macroscopic animals make their debut in the fossil record.”
Subsequent paragraphs focus on methods, but several milestones in animal or eukaryotic development stand out. References to two other Science articles appear to build the case:
Trace oxygen evidence at 2.4 billion years ago (Science, 17 June 2005, p 1730, indications of little oxygen in atmosphere beteen 2.48 and 0.58 billion years ago. The more recent temporal bound ( 580 million years ago) is also noted as as a period of the last of 3 putative world wide glaciations, the late “Proterrozoic Eon.
…”But at the end of the Gaskiers glaciation, deep-sea oxygen appeared, reaching levels that would have required an atmospheric abundance roughly 15% of today’s. That’s about how much oxygen the first large animals – the odd disks, fronds, and spindles of the Ediacara fauna – would needed once they evolved from their presumably near-microscopic , wormy ancestors. And in Newfoundland (Canada), the first Edicara appear 5 million years after the Gaskiers and the rise in oxygen.”
Other supporting data is provided in Nature based on marine rocks obtained off the Arabian Peninsula near Oman.
Last paragraph:
“… The cause of higher oxygen level is unclear. It may go back to the invasion of land by rock-weathering fungi and lichens, or a burst of mountain building.
Cracking that one will take of lot more information.”
– Richard Kerr
==
Of course, the particular ascent by this process to human appearance and cognition is still baffling, particularly if one is attempting to find repeatable pattern. But I am inclined to think that abiogenesis invokes more miracles than something about nature which allows an adaptable pre-program which can be launched on a number of exoplanet sods. And that there is some sort of essence to it. At least a layer deeper than what we’ve uncovered thus far. But what is it?
Given the vastness of the universe (even the part we can sense is vast), the problem of temporal coincidence, and now this “fine tuning valley” we might want to assume that other technological species are “practically” non-existent. That word meaning that detecting, communicating, interacting is impossible. Or just say “impossible for now” without changing the implication. What implication? That we had best take better care of the only known technological civilization and the planet that we exploit and enjoy. As an aside several hominin species, with tool-making and language capabilities have already arisen and disappeared on this planet before their technologies advanced to the point of world domination. Now that our technologies have gotten to that point, I hope “we” will learn to husband our resources and stop wrecking existing conditions of life.
“One recent calculation shows that the probability of spontaneously forming proteins from amino acids is on the order of 10-77. ”
Hi Paul, is this a reference to the fascinating work by Tomonori Totani?
Greetings from permanently raining Ireland!
Always glad to hear from one of my favorite places, even despite the rain! Adam, the reference on proteins is:
Axe, D. D. 2004, Journal of Molecular Biology, 341, 1295
doi: https://doi.org/10.1016/j.jmb.2004.06.058
The full text is available there.
This would have been a good example for Fermi to consider. 10^77 is just 10^-5 of all the atoms in the universe. This implies that even over 4 billion years and countless organisms, that particular protein is unlikely to exist.
But it does, so what is the solution? Evolution by natural selection. The algorithm rapidly hones the search space for viable functionality and continually improves functionality. Well before this paper was written, companies were using algorithms to improve the performance of enzymes, by tweaking the genomic sequences, replacing the domains in the proteins of model organisms, testing the performance, and iterating the process.
It wouldn’t surprise me if companies were already “designing” proteins using existing AI (e.g. AlphaFold and variants) to design biologicals for medical and industrial purposes to reduce the time and effort to achieve the protein functionality they want.
That a single protein has a probability of 1: 10^77 makes an assembly of even a simple bacteria so unlikely that life shouldn’t exist on Earth.
Fermi might then have said, “So why are we here?”
The earliest self replicating organisms likely didn’t have any proteins. They would have been relatively short RNA molecules in a metabolically favorable environment deep underground or underwater. Or both. Importantly, they would have had to be protected from being washed away or decaying faster than they could replicate. Probably in a porous mineral type environment, with Nickel, iron/sulfur and other metallic catalysts to play the role of enzymes. The metallic centers in modern proteins are likely the continuation of those early inorganic catalysts. Similarly, the RNA elements of modern replication and translation complexes are likely the continuations of those early RNAs. I doubt that they could still recognizably carry information from back then, though. The root of our modern tree of life, LUCA, was already much more advanced than those very early replicators. Its only distinction is that ALL of its contemporaries have died out. Because we lack any evolutionary data from before LUCA, we are pretty much limited to pure speculation as to the nature of those earliest replicators, or how they arose. There is a huge complexity gap between autocatalytic chemistry and self replicating organisms that, I think, we have no hope of probing in any real scientific way.
Here is said (animated) cartoon.
https://m.youtube.com/shorts/SmZmiQh0VnA
Eniac,
Reviewing the discussion over the last few days and trying to take it in,
came back to your description of the “earliest self-replicating organisms” without any proteins. Would that include viruses? I am often perplexed by the dual descriptions of viruses being parasitic with respect to “living” organisms and at the same time described as being so primitive. That distinction seems to suggest a scenario where “living” organisms arrived on stage earlier – and then somehow viruses dropped in to interfere with or disrupt life’s happy early
picture. On the other hand, if viruses or “the earliest self-replicating organisms” were much the same, then Drake equations based on “abiogenesis” would need some re-examination. At the very least some impact study.
@wdk
IIRC, the Tierra model, a computer simulation of evolution, that “viruses” developed as degenerate sequences that piggy-backed on the fully replicating “organisms”. This doesn’t prove that this is what may have happened in biology, but it does show that simulations can emerge spontaneously. What I find fascinating about viruses is that the phage variety is structurally more complex than most pathogenic types, injecting their DNA into bacterial cells. That is an interesting evolutionary step. One value of viruses is that the horizontal gene transfer in bacteria is achieved in multicellular organisms with retroviruses that can incorporate their genes directly into the organism’s genome. Sometimes those genes have fitness-enhancing value.
Thanks Paul, I will read the text.
Have a look at the article below by Tomonori Totani, if and when you get a chance (I hope it’s okay to post nature.com links here).
I think it’s amazing how he attempts to “relate(s) two quantities on vastly difference scales: lgN* on an astronomical scale and lmin on a biologically microscopic scale”.
*Emergence of life in an inflationary universe*
https://www.nature.com/articles/s41598-020-58060-0
He implies that life may be common in a truly infinite universe but each instance will always be too far away from any other, therefore for all practical purposes we are alone.
I saw a clever short newspaper cartoon once with the same conclusion – must try to find it again.
Still raining 🌧 here!
Thanks for the link, Adam. I’ll be quite interested to read this article.
This is a nice statistical solution to the fermi paradox. If RNA of the required length for abiogenesis is so hard to come by, then the Eukaryote is even more to come by.
This kind of reminds me of an old Larry Niven story “The Green Marauder”, where the rise of photosynthesis and consequently free oxygen in the Earths atmosphere wipes out an existing anaerobic civilization.
The Drake equation as a tool was introduced initially to address the likelihood that
“anyone” was out there listening and would clarify the issue raised by Enrico Fermi quite succinctly: “Where is everybody?” Consequently the probability approach to ET life has been examined in more detail whether expecting return calls or not, mostly addressing stars, planets, habitability and exobiology.
Amid all this I do not recall spotting a particular parameter’s probability. Perhaps it is generally assumed as unity. That is self awareness.
This might be a tricky matter. Beavers build dams and termites build towers. I suspect that a beaver has a similar self awareness to that of a dog or a cat with a certain amount of ability to communicate. Less confident about individual termites – and then somewhere in our biological chain, this individual self awareness goes to zero.
With artificial intelligence there are arguments whether it exists or not. Its behavior mimics ours, but it is supposed to.
I don’t remember things before I was born. Cases where people or before they were conceived – are anecdotal. Nonetheless, consciousness and awareness in an organism appears to be a property. Maybe we don’t even have as much of it as postulated exobiology. But in practice here on Earth, it is a little like the light emanating from the refrigerator when one opens the door. No matter how fast you open it, you can’t catch it off guard.
But if the power were to go off, or bulb burns out, it’s gone.
Metaphorically, how did the light get in there in the first place?
This is one of the more difficult distinctions between inorganic and organic chemistry if one is sent to the chemical stores closet to replicate life.
I came to pretty much the same conclusion myself, through a totally different line of reasoning. I hope I’m wrong. I’d much rather live in an interesting universe than a boring one.
There is one thing I CAN say though, with great confidence. The Fermi Paradox is phoobah! The fact we have no evidence YET is totally irrelevant. We haven’t been looking anywhere near long enough or far enough.
Fermi’s question was – why aren’t they here, in the sense of there should be signs of previous or current visitations if life and intelligence are so common. We shouldn’t need to look hard, they should be obvious, and everywhere we look.
It has been stated many times that we may not know how to look. The analogy is that we are like ants building a nest next to a freeway. If ETI is either millions of years of development like our past, or so advanced that they may even be transcendent. Neither case would leave obvious traces for us to detect.
As Clarke was quoted (although I have been unable to find where), in 2001: ASO, the aliens that visited Earth and planted the monolith were biological. They transition to become machines/spaceships, and finally become immaterial, as Bowman does as he is transformed into the “star child”. We would not detect that transient machine period unless we got very lucky finding such a structure.
If one believes that life and intelligence is common, then the Fermi Paradox is valid. There are many, many answers that explain the paradox. Pick one. However, the best explanation is that the premise is wrong. Technological ETI is extremely rare, so rare we may be the only one in the galaxy, possibly the universe. That is a terrifying thought, if only that that should lay a huge burden on our shoulders not to extinguish our civilization.
The irony is that while we social animals might crave an intelligence to talk to, we may end up creating it on Earth with our machines.
Well said. I don’t think it’s so terrifying. It means we need to roll up our sleeves and create that ability to colonize the galaxy that will eventually lead to the galaxy filled with life that we crave. In a sense, we are lucky to be born at this exact time, the time during which humanity will become a starfaring species. Even if it may be our AI descendants who will execute on the mission….
The Fermi paradox is not based on how long we have been searching. It is based on how long others should have already existed and should have spread throughout the galaxy. If they existed, they should be everywhere, including right here where we are. We KNOW that didn’t happen. That’s the paradox.
@eniac
They should be everywhere? 100 billion stars and 13 billion years. Maybe they’ve already been here, fifty thousand years ago, found no evidence of tech and they moved on. Or maybe your average space-faring species isn’t interested in any pen-pals. Or maybe they got tired of finding empty worlds and quit exploring altogether. Where is it written they need to leave monoliths or other evidence of their passing? Come to think of it, the conceit they left evidence of their passing in a place where we would need to first develop rudimentary space travel to find it, as Clarke suggests, is a perfectly reasonable hypothesis.
We cannot assume most (or even any) alien species feel motivated to search the galaxy to find correspondents. We don’t even know if intelligence naturally leads to radios and spaceships. Or may they already have all the friends (or enemies) they could possibly want and aren’t motivated to keep searching for others. We think we would do that, but we don’t even know that for sure. Why would any intelligent species feel the need to cover the entire galaxy once they had established their own civilization in enough places that they were secure.
All we really KNOW is that it hasn’t happened YET. Or if it happened, maybe they didn’t bother to tell us. Or if they told us we forgot about it, or thought they were gods, or simply were wiped out by some natural disaster shortly after they left. If ET landed on the White House lawn tomorrow we have no guarantee anyone a thousand years from now would remember the visit.
All the Fermi paradox really tells us is that ETI is very rare, or the speed of light is very slow, or most civilizations don’t last very long in cosmic terms. Dr Fermi knew intellectually, roughly, how big and how old the Galaxy was, but I don’t think he had the emotional grasp to really understand the immensity that size and age represents. Few people do, regardless of their intelligence or education. I never figured it out myself, until fairly recently.
You may be right, they will never reveal their presence, or they may show up tomorrow. We just don’t know. We have no way of knowing.
I assume that ETI will not be looking for “correspondents”. They will be looking for places to colonize, or for competitors to snuff out.
I would assume this of a species devoid of intellectual curiosity and predominantly of a brutish nature.
It’s not a matter of “passing by and leaving again”. Think of it more like a mold spreading over an apple or humanity spreading over Earth. The entire accessible habitat is eventually occupied. All it takes is a substrate to feed on, the ability to colonize and enough time.
We’re not talking about one civilization, either. Or about a unified “intent” to do something. We are talking about a species that has acquired the means to colonize other star systems. Due to light speed limitations, there will be a minimum of one coherent “civilization” per colonized star. As long as even a very small fraction of them continue to colonize, the entire galaxy will be filled with them in a small fraction of a billion years.
But imagine the richness of the experience after several cycles of colonization, when you have thousands, millions, or billions of civilizations. There will be no trade or war between stars, because of the latency. But history and culture from countless civilizations will come streaming to each one of them over the galactic communications network. It would be like having a million histories instead of just one. A million times the cultural experiences available to us now. It’s mindboggling, really.
Maybe it’s too bad that Fermi did not elaborate on what he meant by his question. And the “maybe” is on account of he might not have wanted to step on glue and get stuck with the question since he had plenty else to do and might have been satisfied with the horizons that existed there.
But when we tie together Fermi’s question as introduced – and the subsequent deliberations based on the Drake equation, we end up with an answering machine that means all things to all men. Save for little green ones – if they are even on hold. “… Please dial again.”
Metaphors, of course, but ones that allow some summary. Since Drake et al.,
as pointed out, were concerned with radio telescopes, getting time on them and making sure more sensitive ones were built and available too, retrospectively we can see the importance placed on listening for other people who liked to build radio telescopes too – and then calculating the odds that they were doing so. In articles on the subject, I also remember commentary about how much more sensible that would be than for the aliens to commit to such endeavors vs. flying out to greet us – or perhaps to tap with rocks…
But on the other hand, the Drake equation does not really need to focus on its basic premise, radio calls from other stars. All the pyramidal probabilities can
be examined up to any point desired: Number of planets in galaxy, number of habitable based on surrounding environment, number of planets with sufficient cooling and chemical development…. and then the biological circumstances as we know them.
The main reason to review this point is that we can pause the Drake equations at any part of the pyramid that is supposed to culminate in an alien sending out Morse code: planets with precursors to life, planets with possible prokaryotic flora, etc.
Because in the meantime since the circa 1960 introduction of the Drake equation, many of the elements then ( such as existence of exoplanets) have been placed into solid data tables. Then we could not see any of them, and now we can detect and characterize a fraction that defines what is below the tip of the iceberg. Exoplanet atmospheres are still a trying issue. But since the solar system could be considered by outsiders as a star system with “exoplanets”, we should anticipate some earth sized planets with atmospheres out there too. And should some switch from CO2 to some free oxygen, that would be encouraging as well.
All this suggests that whatever the real Drake equation answer is for civilizations, its likelihood has risen by orders of magnitudes from the decade when the concept originated. Even though we are not able to fill in probabilities for the likelihood of ET the radio ham.
And beside that, we have learned some interesting things along the way.
In my opinion the main idea here doesn’t hold water (pun intended). In the first case only the approx 50/50 requires fine tuning, but In life in cosmos question every case from .1 to 99.1 would require it’s own “fine tuning”. of course I have serious doubts about the higher percentages, but that’s just me.
The only problem I see with the zoo hypothesis is that although it is a hypothesis that matches observations, it makes the wrong comparison. I don’t think the comparison of today’s technological level and level of consciousness can be limited to animals, bugs, etc. Maybe ant hives in some cases. A more accurate comparison might be modern man to primitive cultures. Primitive man won’t work because he was before language and civilization. The idea is what counts and the zoo hypothesis really does make the idea of colonization obsolete if man’s future destiny is in the cosmos with interstellar travel like warp drives, etc. I like the idea that when our level of collective consciousness is high enough, the ET’s with interstellar travel would contact us. Maybe they won’t. Maybe they won’t contract us until we actually travel to to their world with a warp drive, etc. Consequently we join the galactic club which has a prime directive. I image that situation when we get there they tell us what took you so long? You cheated with your UFO retrieval program and technological development and you still took longer than us. That could be embarrassing. We become lazy when the answers are given to us.
Well, from our own existence, we know at least one technological civilization exists. But then either the ours is first, or some other got into existence before us. Either way, assuming big-bang theory is correct, there is/was certainly a civilization that was first in the universe, with no other civilizations existing anywhere. Maybe that is us .. or maybe not.
We can also assume that once civilization reaches interstellar capability, they will likely spread fast, at least within galaxy (I’ve seen simulations where whole galaxy is able to be colonized within few million years even with relatively slow ships, migrating when stars come very close to each other, less than 1 LY apart) – but how much more difficult would be spreading across galaxies?
This is actually a very good question. It would be very hard for intergalactic colonization to occur without FTL travel or without hitching a ride on natural bodies that are unbound from the home galaxy. If a civilization spreads to fill a galaxy, even if it doesn’t spread to nearby galaxies, there should be observable technosignatures from that occupied galaxy, if we can figure out what they are and look for them. If a civilization fills up a galaxy, colonizing every habitable world, building artificial habitats in essentially every star system where such is possible, and conducting interstellar and interplanetary commerce to the extent possible, what would be the signatures? A lot depends on what technologies they use for propulsion, but some factors should be independent of such considerations. There should be some signatures visible in infrared, radio, and possibly other wavelengths if we can figure out what to look for.
Of course, this poses the “flask” fine tuning problem of the original article, again: If it happens in some galaxies, it should have happened in all, including ours, but it didn’t.🤷♂️
One way may be knowing what to look for … but civilizations may have many motives for reducing their detectable signature. One might be efficiency (for example replacing high-power radio broadcasts with low-power directed laser communication, optic cables, etc …), one might be stealthiness (hiding for fear of being attacked by other civilization, or other fraction of that civilization), or ecology …
Perhaps the only detectable thing in civilization concentrating on the stealth factor could be waste heat (i.e. some excess of infrared) from technology, but maybe with some advanced technology this signature can be reduced/hidden/eliminated as well
I’ve always questioned that idea that ” once civilization reaches interstellar capability, they will likely spread fast,” even without FTL capability. This may very well be the case if the civilization is obsessed with spreading across eternity, and if it can maintain that obsession indefinitely, and if its colonies can immediately establish themselves and quickly develop local resources to continue the expansion, and if they are mostly successful at doing so at each new star system they colonize, and if they don’t stumble onto another expanding culture along the way. That’s a lot of ‘ifs’.
Personally, I think that’s mostly wishful thinking, or projection of our own obsessions onto others. After all, even the most imperialistic cultures on earth have limited their growth after certain spatial or temporal boundaries were reached. I believe even the most aggressive, expansionist cultures will lose that obsession once they have spread to enough worlds that their long-term survival as a species is assured. They will then settle down to exploit the fruits of their empires and concentrate on making their lives more comfortable, or collapse, succumbing to internal contradictions and conflicts. Either that, or they will collapse from internal stresses generated by the expansion.
There is another, more subjective consideration, as well. Look at a long time exposure photograph of any section of the milky way, or just go out on a dark night and take in the sky. That’s just a tiny piece of our home galaxy. It can hold multitudes.
Terrestrial civilizations reached their territorial limits due to the cost of maintaining it from outsiders that pushed back. The most recent example is the failure of the US to control Afghanistan, as each prior empire failed to do so.
However, if we think of expansion as a simple mindless spread, I see no reason why it couldn’t continue as long as resources enabled it. The von Neumann replicator model is an example of “mindless” expansion that could fill the galaxy, albeit c limits any coordination. And why assume the long-term survival of species, rather than selfish genes ( or now memes)? Biological beings that can effectively create resistant spores could, in principle, cross interstellar distances slowly, emerging from stasis and populating suitable planets. There needn’t be any need to maintain a civilization, cohesive or otherwise, just new populations forming their own civilizations based on whatever prior information of their originating civilization they want to keep.
I like Eniac’s suggestion that eventually the galaxy is filled with billions of civilizations, although I might temper this with billions in total over time, even though few might be extant contemporaneously. This would be the model of a shared Encyclopedia Galactica that recounts the billions of histories that existed over time. We may just be the “first”.
I think you, like many, confuse “lifetime of civilization” with “lifetime of life”. Civilizations may fall, but they are replaced with new ones of the same species. Species may end, due to competition with others, or by evolving into something different, but they will always be replaced by a new species in the same niche. Life itself is eternal. Cases were colonized star systems will revert to become uninhabited or sterilized will happen rarely, if ever. Even if they do, the empty habitat will likely be recolonized soon.
Actually, the “ifs” wirk in the opposite direction. You don’t need all civilizations to be “obsessed” with colonizing. If only a small fraction do, you get expansion. And you need only a subgroup of a civilization large enough to sustain the effort. The rest can be indifferent or even opposed. So, you only DON’T get expansion if ALL civilizations and all subgroups therein forego further colonization. That’s a very big ‘if’.
Worse, even: They ALL have to forego colonization completely for millions of years, despite having the capability.That strikes me as extremely unlikely.
I am actually not so convinced. In the last fifty years or so, we have seen that the most technologically advanced/economically developed nations end up with a below replacement birth rate. This appears true across broad cultural divides and totally different forms of government.
Therefore, even if humans develop interstellar travel, I do not think we will ever “fill” the galaxy (in the sense that there would be a population as large as current Earth’s around every suitable star, and thus a total human population of 10^20 or something).
It seems at least vaguely plausible that the economic factors that make this true for humans will apply for others as well.
@confused
The trend is more likely to be due to economics and income distribution than any inherent trend due to wealth. For example, after WWII, there was a baby boom that lasted into the mid-1960s. The Western world started an increase in inequality that continues to this day, making raising a child more expensive. Change that dynamic…
It is a different story in countries with low per capita incomes where public health improvements, contraception, and women’s education have reduced birth rates and death rates resulting in slowed population growth.
Open up a “new frontier” where opportunity and net income increase, and I would expect populations to rapidly increase.
I don’t think it’s just – or even primarily – inequality increasing the cost of raising a child. I think it’s things like urban social structures (vs “village to raise a child” cooperative dynamic), education costs, and “payback time”*.
I think the economic factors are pretty inevitable assuming high urbanization and a high tech/high education requirement economy. [During the post WWII baby boom, college was not perceived as necessary for a decent career, as it is today.]
And the lack of expansion doesn’t actually have to be universal or permanent – it is only necessary that no civilization sustain a high-tech expansionist phase long enough to colonize a significant part of the galaxy. Which is a really long time on civilization scales, though short astronomically. You could still have major colonization booms that eventually fizzle out.
Reading Kipping & Lewis’ paper rather than just the fine video, I see a flaw in their formalism. [ At least the math is within my capabilities!] They show that if the birth rate of communicating civilizations is greater than the death rate, then the number of extant, communicating civilizations should be the carrying capacity of the sample size, e.g. all the inhabitable stars in the galaxy. There is also a requirement that the number of civilization per planet cannot be more than one.
As they admit, this works for life, allowing all inhabitable planets to be inhabited. I see this as a result of life being forced to operate within its constraints – energy and matter, with no excesses possible. Indeed, this is what drives natural selection.
If we consider “technological civilizations” that are constrained by natural resources, none achieved any ET communicating capabilities. They could exist indefinitely (although by the discovery of metalworking, this may no longer be true). As long as they didn’t kill themselves off across the planet, they could continue as they had for millennia, and arguably for all of human prehistory. The Industrial Revolution produced a step change, with active resource depletion and the development of technologies with truly existential risks. There is no guarantee that humanity, or any ETI will survive more than momentarily on the cosmic time scale. Therefore the death rate may change depending on the technological state of the civilization.. Initially, it may be low, allowing for inhabitable planets to be fairly commonly inhabited by pre-technological and low-technological civilizations. Indeed, many per planet, each within a limited geographical range. However, once the technological level increases, the death rate rises. This makes the last term of the Drake equation – Lc – relevant. If radio or other communication means arrives, it may often be associated with the rapid death of that communicating civilization. In the video, we are that bread mold, we have run out of resources. Unlike mold, we probably cannot spore, nor will there be more bread to revive us.
If so, then the galaxy may be filled with civilizations that we could communicate with in principle, but only by visitation. If we snuff ourselves out, then that possibility ends.
The other possibility is that the birth rate is so low, that there has not been enough time for the number of civilizations to arrive to occupy their planets. The death rate could be zero, but the absolute numbers are so low that we may even be the first, but probably within a few, despite the universe’s age.
I see the Kipping and Lewis paper as an addition to the list of answers to the Fermi “Paradox”, but whether it has any special explanation seems unlikely to me.
[Call me cynical, but the initial value for Nc at the Greenbank conference of around 10,000 civilizations [?] was arrived at by motivated reasoning to justify devoting resources to further SETI. As Kipping notes, it is a staple of classes to allow students to come up with their own estimates for the Drake equation values and it is easy to get a value of 1 (Earth) or 100s of billions with just those last terms.]
Still trying to fit a curve to a single data point. Particularly this bit: “one might expect success with a SETI survey”; any such survey is loaded with assumptions about what might be detected, which assumptions we have no way of knowing whether they’re reasonable, never mind true.
Beside an inserted comment above about the Drake equation and how it does not have to be solved for only one value ( number of radio communicating civilizations), there is also the other side of the coin – odds of an empty cosmos.
And in consideration of the title which frames this topic, one could be accused of being a Polly Anna for ignoring it. After all, since the Age of Reason of the 18th century, such an answer has been widely assumed as “rational”.
Well, I am just not sure. This gets sensitive, of course, since we begin to speak of universal “design”. But if we argue enthusiastically that we are here with what rationality we have and all by accident and then elaborate on all the circumstances which were needed to fulfill our arrival on stage… It’s really becomes very compelling … that we really shouldn’t be here at all.
A century or so earlier than the rationalists, Rene Descartes provided the often quoted, “Cogito, ergo sum” quote. Readers since, if they were unsure of their existence were perhaps reconciled by this observation – and perhaps believed that he ( had) existed too. The LGMs have not weighed in in that manner.
Unless this accident, incident or experiment of our existence is repeatable in some manner or to some level. It might turn out that we are in isolation for all practical purposes. Admittedly some processes in the universe appear to be manifestations of disorder. And maybe we ourselves are in some manner – to allow for our appearance. Factors submitted currently for the Drake equation suggest a very exact roll for an awfully large number of dice.
So much of our discussion of the cosmos is based on a “non-unique” position within it, that we are not on the edge, middle, left or right, top or bottom but set within one of myriad galaxies. Time from start and galactic position and stellar remove count as important. … But our awareness is completely counter to that.
Arthur C. Clarke posed the problem, of course. If the universe is entirely empty and provable as such like a theorem, then it does have some logical issues due to the improbabilities piled up with our own existence, here, with such a string of staging circumstances. If there were rationalist wardens for this park we live in, and we were caught picnicking on the grounds, we might as well be arrested for trespass.
But it’s not a “no exit” situation, however. We might be on the verge of some answers that might make this all less evenly probabilistic. We might soon find evidence of previous or contemporary life of modest form. It could be independent and local in origin or part of system with universal precursors. We can then take up the issues again based on such a result. Rather than an either or, in the near future it could become a fraction more positive.
And, I should note again, that A. C. Clarke admits of his own existence and the other people in the theater audience when he poses his panic proposition. If he had assumed that some of the audience had imaginary friends, then the question that disturbs him gives him more of a bond with those others than he might have let on.
Olaf Stapleton’s “Star Maker” has transcendance of people from many civilizations who finally get to see the creator, the Star Maker. Clarke was highly influenced by Stapleton, and Clarke’s Childhood’s End is very much in that mould, as is the ending of 2001: ASO. Today we might think of transcendence as the singularity.
It is possible that this is how physical civilizations disappear, preferably without destroying their home world. It is a path that allows both life to be ubiquitous, and the birth/death ratio of civilization to be greater than unity, yet the galaxy (universe?) be apparently empty of advanced civilizations, or at least with far fewer than the exponential growth of populated worlds implies.
A.T.,
As a result of an earlier Centauri Dreams entry on Stapleton and his “Star Maker” story, made a resolution to locate it and “First and Last Men”. It took a while but one day found both in a local used book store. My only previous exposure was an excerpt of the former or “The First…” in an anthology when I was in middle school, if I recall correctly. Still startling but in a different way now. This time I took some notes.
But should the topic come up again on Centauri-Dreams, I look forward to participating in any of the related discussion.
A cosmos Drake’s N of 1 requires the universe be finite in space. For an infinite universe N is infinite. An N of 1 for the visible universe or a more realistic volume of some billion light years demands humanity be the most complex and capable beings in that volume. I am not terrified by this, but I need to be convinced that the rarest is most probable and that the emotional payoff off being the smartest and most capable isn’t biasing the prediction. Imho, the risk of emotional bias effects pessimists far more than optimists.
Is it just me?
Or has there been a big shift in the SETI community, just in the last few years or so, on the ubiquity of extra terrestrial civilizations?
It seems only recently that the consensus in the community shifted from “there are many technical civilizations” in the galaxy to there is “only one, or at most, only a handful”.
“Or has there been a big shift in the SETI community, just in the last few years or so, on the ubiquity of extra terrestrial civilizations?”
There does seem to be a shift in the SETI zeitgeist recently. Unwarranted in my view and I’m still in the “too little data” camp.
Though lately, I’ve been toying with looking at the N=1 (in our galaxy) hypothesis backwards.
If we make two highly questionable assumptions:
1. All Earth like planets in the Milky Way, follow roughly the same trajectory and time line. I.e. it will take an Earth like planet ~4 Gyrs to host a civilization at least as advanced technologically as ours.
2. The conditions governing the emergence & development of life in our Galaxy have remained constant for at least the last 4Gyrs.
Then using some even cruder maths, if N=1 (us), then at this current point of time, there will be ~4E7 planets in the galaxy that have some form of life ranging from single cell organisms, through to dinosaur analogs through to us. 4E7 is simply calculated as the ratio of the length of time life has been on Earth to the number of years we have had radio telescopes (~100 years).
Similarly of those 4E7 planets, 5E6 of them will have life more advanced than Earth during the Cambrian explosion.
Also, assuming that our species is 200,000 years old and civilization is 10,000 years old, then 2000 planets will have some form of intelligent species of which 100 will have some form of civilization ranging from analogs of our earliest civilizations through to us.
Scale the above numbers for your favourite value of N.
Bonus question do the same crude BOTE assumptions and estimates apply to small satellite galaxies like the LMC & GMC or to elliptical galaxies?
Suppose the moment T today; our empty galaxy and number 1 – we, which have emerged, let’s say randomly. We must then consider ourselves as one of the key factors that may be able to engender life elsewhere, in the sense that our productions; interventions on other worlds close to the earth, have already altered the precarious and mysterious balance of the universe. What balance can we have already changed?
It is a bit the story of the papillion that we crush in prehistory: very clever is the one who will be able to predict what will happen 200 million years later.
Thus, in this hypothesis, there is “no one” and it is normal, we have to wait. (which raises the question of our survival in time etc) But in the same time it seems to me that by reasoning in this deterministic way we cancel the question of whether it is terrifying or reassuring what allows progress.
If we consider ourselves as a simple variable of adjustment – I know it’s hard, our ego takes a hit :) – and not as ETI to ETI, the mind experience takes on another dimension…
On universal scales, and in relation to our tiny size, we are reduced to speculations because the distance does not allow us to “see” what is probably also globally at our scale or less. Our latest technology allows us to see the horizon of the universe at >13 billion years but not what is on the object targeted or around. We are therefore condemned to either improve ourselves technologically or to expect a hypethetic “sign” of an ETI, an object, or more simply an unusual phenomenon in the universe that will confirm us that…
The question of consciousness has been discussed above. It reminds me of a reply in another post, where I asked for “why” we were on the arm of Orion, neither too close nor too far from the center of our galaxy. the answer is often connected either to theology or to randomness. But one of you raised the idea that the consciousness proper to our species (?) had emerged at that time and at this position of the earth in the galaxy. It could have emerged before or after The idea troubled me a lot. In other words, without consciousness, whether there is life elsewhere or not, we can’t say anything. I agree with the philosophical idea that the universe (and what is in it) exists …because we can observe it.
We might run out of fossil fuels, but not resources. All of our technology, especially computers has moved towards being more energy efficient. Survival forces our civilization to have progress in technological development. With a warp drive, a civilization could find resources on other planets and even exoplanets that don’t have life. After seeing some UFO’s, I have thought one of the drake equation variables is very improbable, the extinction though nuclear war. If we take that one out of the equation, then not any civilization in our galaxy die. They just leave their system when it becomes a white dwarf and move their planet into the life belt during the red giant phase. I hope that is our fate.
@Geoffrey
Entropy says you are wrong. As an example, imagine if all our resources have become so mixed that it would be like trying to extract elements from seawater. The costs would be astronomical. [AFAIK, there are still no companies trying to extract gold from seawater, let alone other, more useful, elements. ]. It wasn’t that long ago that there was some issue of contaminating iron with so many other elements using recycled steel, that all steels would be rendered contaminated and unfit for specialized use.
@Alex Open AI Chat GPT thinks you are applying the entropy idea out of context. I agree. Entropy is the second law of thermodynamics where the universe moves towards a disordered state. It depends on the efficiency of the recycling process and what one’s food and energy sources are whether they are reusable or non reusable like fossil fuels. We have yet to reach full efficiency or depletion. Steel is made of carbon and ion and alloy. Stainless steal is another alley or combination of metals. Iron and steel are recyclable. In the future our homes might not even be made of wood, but space age materials and meta materials.
Although my friend Jim Cambias likes the ‘insufficient data’ position, I have been thinking that the data is getting pretty sufficient, thanks to Breakthrough Listen, which has done ~100 M$ state-of-art searching.
I am beginning to think that it’s now too late to say that it’s too early to tell about SETI detection.
In a new as-yet-unpublished paper by Marcy and Tellis, which searched the Milky Way Plane along a 6-deg swath for pulses of monochromatic light from laser beams as faint as 15th magnitude, no detections are reported.
They note that “We have now had 64 years of non-detections by past optical and radio SETI observations. In addition, thousands of all-sky surveys, performed at all wavelengths, discovered many extraordinary astrophysical objects, but revealed no signs of technology. Hypotheses that presume the Milky Way Galaxy is teeming with technological beings must be demoted, a profound realization. The dearth may be due to the rare evolutionary ascent of sentient beings or to their self-destruction.”
So, in contrast to Henry Cordova , I think the evidence against communicating civilizations in the stars is rapidly accumulating.
Throw in hydrogen hypothesis for Eukaryote and your argument is massively reinforced.
@James Benford
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That’s funny. I thought I agreed with that statement! Remember my contribution to centauri-dreams “A SETI Reality Check, Jul 3, 2020”.
“Indirect evidence suggests that SETI-capable civilizations will be highly separated in space and even more so in time. There may be a much smaller probability than previously thought to make contact with these cultures. In order to maximize this probability, we may have to rely on search strategies which are counter-intuitive.”
I’ve recently come to believe the number of communicating civs in our galaxy active at this time is “at best, a handful”. I’d like to leave the door ajar for a possibility of at least a few (or maybe find myself a new hobby).
I still believe the logic of the Fermi Paradox is in error, but I must concede the conclusion it leads to may still be correct.
@James
T2o-way communication may indeed be a remote possibility simply because of distance, time, and the speed of light.
But not one-way communication. Every prior terrestrial civilization has communicated something to us through their physical works, practices, and even better, their thoughts. The Greeks and Romans left us a wealth of thoughts that are still used today in Classics education.
If the Conquistadors hadn’t deliberately destroyed Mayan texts, we might know a lot more about their thoughts too.
We have often discussed the longevity of terrestrial artifacts. A few million years at best seems the conclusion – on Earth. But the Moon is a different environment and far more stable as a preserving ground. I am reminded of those ideas by Rezabek about putting “vessels” of our culture and technology to be recovered by our descendants. One location was the Moon. A buried repository would also be a means to communicate with its discoverers, human, post-human, robotic, or ETI.
As it doesn’t announce itself to the stars with energy-consuming beacons, any more than Stonehenge, the Pyramids, Troy, or any number of buried structures and artifacts, there is no reason to be a prior discouraged. It may require our civilization to be star-faring to discover the equivalent remains of other, possibly very rare, civilizations. If they left repositories of their civilization, perhaps a museum’s worth of “Golden Disks”, they would be able to communicate with us from the past. We are on the threshold of creating true machine intelligence. Add that to a human repository and ETI and this AI could eventually have a 2-way communication.
Let us remember that “Absence of evidence is not evidence of absence”. We can never prove X does not exist, only that it does. The black swan history is a perfect example of this as the Old World had only white swans. It took voyages to Australia to discover they existed. It might take STL voyages of millions of years by our descendants to discover extinct civilizations through their artifacts, just in our galaxy alone. There is far vaster universe out there beyond the Milky Way.
Unlike most people, I’m not bothered by us being alone in the universe. I don’t understand why people are so bothered by this.
Look up Nick Lane and the hydrogen hypothesis origin of the Eukaryote. This is the single biggest filter for the emergence of complex life and is the reason I think we are alone.
If there are other civilizations, they are likely a billion or more light years from us.
I think you may be misreading Lane. Yes, the endosymbiosis of a bacteria into an archaean may have been a singular event, but it took place over 1 billion years ago, about 2-3 billion years after life emerged. There is no reason to suppose that this event could not happen repeatedly until it successfully took. The same applies to chloroplasts in plant cells.
It still took at least another half billion years before we saw the emergence of all the current phyla from the “Cambrian explosion” and their much more rapid evolution of forms since then.
There are other events, especially mass extinctions that have changed the dominant forms, most notably the KT event that eliminated the non-avian dinosaurs and allowed the small mammals to rapidly radiate in forms, including the primates, and thence hominids.
I’m not misreading Lane. Lane himself believes we are alone based on the fact that all Eukaryotes actually did come from a single ancestor. Yes, the endosymbiosis may have happened multiple times, and I’m sure it did. But the fact it that it “took” only once as far as we can tell. This alone suggests its a wildly improbable event.
The recent discovery that does have implications for the availability of habitable planets is the recent discovery that the manganese modules produce “dark” Oxygen by an abiogenic process. This suggests that there may be a far greater number of habitable planets in the galaxy (and universe) but that the vast majority of their Oxygen atmospheres are generated by abiogenic processes.
I watched an interview with Lane and you are correct, he views the emergence of eukaryotes by endosymbiosis as a rare event in that all eukaryotes share a common ancestor, and that there are exceedingly rare cases of bacteria with other endosymbiotic bacteria. However, I would say the same argument could be made of LUCA, even though it is often posited that there were other contemporaneous lineages that went extinct. Is it not possible that our lineage is a similar example, that our ancestor was just the most successful symbiosis and all others were eliminated?
Lane seems ambiguous concerning life at all being elsewhere, although he says that he thinks bacteria could be fairly common, even though he doesn’t know whether life is a natural outcome if the ingredients and conditions are present. He does think that as multicellular life must be eukaryote (because no bacteria or archaea have ever created morphologically complex life that we have observed) and therefore because it is such a singular event in his opinion, that ETI may not be present and therefore “we” are alone if referring to “we” as eukaryote life, and just possible alone if “we” refers to all life.
He is not didactic though, and humble enough to admit he could be wrong.
We just won’t know until we look. What it does suggest is that if we find life elsewhere in the solar system, it will be prokaryotic, and therefore no fish swim in the Europan or Enceladon subsurface oceans. It just doesn’t mean that all inhabited worlds must stall out with prokaryotes and that this implies not ETI, just that if he is right, ETI will be very rare. He says in the interview that this is his favored solution to the Fermi question.
Nick Lane interview
Even a cosmos chock-full of forms is seen by some to be as empty as a mirage pool in a desert is devoid of water.The saying goes “Form is emptiness and emptiness is form”.
The doctrine of sunyavada (emptiness) is as difficult as the non-reality of ones’ self.
Yet even if we accept the universe as real, one has to contend with the end of the universe.
This article, brilliant as it may be, misses the forest for the trees.
It is based on the assumption that there are many Earth-like planets in the universe. JWST data along with numerous other satellites prove this is not the case.
The Earth sits in a cocoon of protection not witnessed anywhere else in the universe.
Our Sun is larger and more powerful than 95% of the stars in the universe. Yet, it is thousands of times less dangerous than all other sun-like stars we have observed. Our Sun’s solar flares and CME’s are a fraction of similar stars.
Further separating us from the universe’s normal, planets have only been observed orbiting metal-rich stars like our Sun. Thus only a small percentage of stars can have planets.
The latest research also indicates that 80%+ of all stars exist as binary pairs or in larger groups. The gravitational interactions and solar activity of these stars would also make life impossible.
In short, no other star in the universe, we have thus far observed, can support life.
No other solar system remotely resembles our own. There is no such thing as a group of small rocky planets closely orbiting a giant star with massive gas/ice planets orbiting at further distances. The large planets form a protective shield that stops comets and asteroids from ending all life on Earth on a regular basis.
Our moon stabilizes the Earth’s rotation and therefore our climate. Simply put, no moon, no life on Earth. But exo-moon has ever been observed.
The Earth itself is completely unique in the universe. The chemical composition, the magnetic field, the ozone layer, the presence of liquid water, plate tectonics…all these things have to be precisely balanced for life.
Finally, we have to be located in exactly the correct place in the Galaxy. Any closer to the center and radiation and collisions are life exterminators. Any further out and there aren’t elements that life needs to exist.
Everything is goldilocks on Earth, but this article takes it all for granted.
You are arguing for an anthropic principle for our Earth. Douglas Adams satirized that argument:
“If you imagine a puddle waking up one morning and thinking, ‘This is an interesting world I find myself in — an interesting hole I find myself in — fits me rather neatly, doesn’t it? In fact it fits me staggeringly well, must have been made to have me in it!”
I agree with the anthropic principle. It does not rule out more solar systems similar to our own with gas giants in the outer solar system and a third planet with a moon and rocky planets in the inner solar system. In other words we are not the one and only since the laws of statistical probability based on the general relativity of solar system formation favor more of the same, but yes these would make intelligent life more rare and dependent upon many more contingencies than microbes.
“It is based on the assumption that there are many Earth-like planets in the universe. JWST data along with numerous other satellites prove this is not the case.”
I am not aware of anything about JWST, or any other satellite, that supports this statement. You do not need an earthlike planet to have life. Other planets may have characteristics suitable for the origin and evolution of earth-type life, yet still be quite different. And there may even be other types of life. As long as certain constraints are in place, life will evolve to meet the conditions present. Once certain basic conditions exist, it does not need a goldilocks condition.
“The Earth sits in a cocoon of protection not witnessed anywhere else in the universe.”
I see no ‘cocoon of protection’. Just what do you mean?
“Our Sun is larger and more powerful than 95% of the stars in the universe. Yet, it is thousands of times less dangerous than all other sun-like stars we have observed. Our Sun’s solar flares and CME’s are a fraction of similar stars.”
Life can evolve under ground, or under water, there is no reason it could not evolve on any star that lived long enough and was relatively stable. It might look different than earth life, but it would not be impossible.
“Further separating us from the universe’s normal, planets have only been observed orbiting metal-rich stars like our Sun. Thus only a small percentage of stars can have planets. ”
Planets have been found around all types of stars, even metal poor ones. They are just metal-poor planets.
“The latest research also indicates that 80%+ of all stars exist as binary pairs or in larger groups. The gravitational interactions and solar activity of these stars would also make life impossible.”
Not all binary pairs are close binaries, where the companion star’s evolution or gravitational perturbations would threaten biology on the other member.
“In short, no other star in the universe, we have thus far observed, can support life.”
That is simply not correct. Besides, we have seem many other stars that resemble our own sun, and others who have been considered life candidates.
“No other solar system remotely resembles our own. There is no such thing as a group of small rocky planets closely orbiting a giant star with massive gas/ice planets orbiting at further distances. The large planets form a protective shield that stops comets and asteroids from ending all life on Earth on a regular basis.”
Due to the crudeness of our planetary detection methods, we do not know if that statement is true. And if it is true, we do not have any reason to believe it matters.
Our moon stabilizes the Earth’s rotation and therefore our climate. Simply put, no moon, no life on Earth. But exo-moon has ever been observed.
Some people do believe the alleged stabilization effect of a moon is a requirement for life. I don’t. But even if it is true, other factors may compensate for it.
“The Earth itself is completely unique in the universe. The chemical composition, the magnetic field, the ozone layer, the presence of liquid water, plate tectonics…all these things have to be precisely balanced for life.”
The earth is not necessarily unique. But to have life we need not posit an exact copy of it. Life is adaptable, it has evolved to thrive in many environments on earth, including some very hostile ones that appeared in our past. In fact, life has altered the planetary surface and atmosphere and made it more hospitable for advanced life forms. Life already had arisen when plate tectonics began, life CREATED the ozone layer when photosynthesis released free 02 into the atmosphere, liquid water is the very definition of Habitable Zone. Even in our solar system, other planets have magnetic fields.
“Finally, we have to be located in exactly the correct place in the Galaxy. Any closer to the center and radiation and collisions are life exterminators. Any further out and there aren’t elements that life needs to exist.”
Not true. Although there is indeed a metallicity gradient in the galaxy, wherever massive stars have formed their evolution has already returned , through nucleogenesis and supernovae and planetary nebulae, metals to the interstellar medium. Yes, there is more metals here, but there are pockets of metallicity all over. As for “radiation and collisions”. that may be a problem in the very center of the galaxy, near the black hole , but the risks drop the further out you go. The sun is a long way out from the center, I’m sure hospitable conditions occur much further in.
“Everything is goldilocks on Earth, but this article takes it all for granted.”
All of your arguments seem to hinge on the idea that life can only exist in a very narrow range of conditions, and that the earth is the only possible place where all those conditions have been fully satisfied. Its as if life arose only on this world because of divine, intelligent design.
But everything we know about life on earth tells us it is tenacious, adaptable and damn near indestructible. We also know it arose on this planet when conditions were, by our contemporary standards, completely toxic. And it thrives here now in environments we would find intolerable.
There’s a lot we don’t know about astrobiology, but everything we do know suggests life is common in the universe, and intelligent life is possible. Ours is a worthwhile pursuit.
The list of concerns above are worth remembering and considering in so much as we are speculating on undetected life or intelligence. But as comprehensive as it appears, and how rare it would appear to make life itself over all, one has to note how ruthlessly the processes that resulted in life – and eventually us – appeared to have taken advantage to this remarkable exception.
The stability of the sun was not always the same. Crashing a planet into the Earth to produce the moon does not appear to be a sure fire method to produce life a billion years hence, or recovery from a total freeze over – or the release of enough oxygen to allow for advanced cellular life – or a succession geological crises…
But here we are.
In addition it is difficult to reconstruct how many asteroid bombardments or supernovas the Earth might have encountered in the interim. Should we presume that they are necessary crises for life because they are part of our geological history or could it be that life at some phase of ascendency on Earth made adaptations?
If so, then can we make a sharp delineation with the data available that precludes life on any body other than Earth as of yet?
The points above about the search over the spectrum for emissions similar to a technological civilization such as our own or we foresee for our future. These returns, they are what they are. At the very least, they indicate that Little Green Men are not doing business that way in our vicinity. Anthropology would be a misnomer for a species we have yet to encounter. But whatever the topic is, it could play both ways: The subjects might not do things that we do because they can’t or don’t exist; or they don’t do things the way we do because they don’t have to or disapprove. I could attempt further speculation, but will just suggest in summary we might have to tread water backwards if the LGMs are there but don’t use many of our “modern conveniences”. I don’t know if it’s a radical idea or not, but perhaps exponential industrial growth is counter to survival in the galaxy, especially with the first technologies a “manipulative” species encounters in development.
But search for life or how it is different elsewhere is still a scientific issue of importance. Years preceding the Apollo landings, the scientific community often published reports to the effect that they would rather have found out more about life precursors on comets. Although I can’t guarantee an outcome, our back and forth these days on the subject ( life beyond Earth, if not necessarily ETI) makes me appreciate that standpoint more than I would have prior to the lunar landings.
I’m not familiar with the work showing that the Sun is unusually placid compared to similar stars – it would be very interesting to find something special about our star. But the Sun is, at least, not *always* as calm as it has been in recent times; there are “Miyake Events” which make even the Carrington Event undetectable by comparison. https://www.scientificamerican.com/article/solar-superflares-rocked-earth-less-than-10-000-years-ago-and-could-strike-again/
A lovely article, adding another piece to the puzzle through its clarity of form and presentation of what else could possibly be out there and how. Though I must admit that in resolving the picture of what could be out there, in this way, we may be necessarily making it nigh impossible to see the bigger picture and quantifying that ‘big picture complexity’ that will actually solve it.
The assumptions that we seem to be hanging our hat on, in my barely-qualified opinion, may be causing our view to be off-centre of the target – that is quantifying what life-type-complexity exists out there and how.
Like saying:
… that the necessary ‘complexity beach-head’ for multicellular life happens to be a certain system of uni-cellular life; that the necessary complexity beach-head for sentient life happens to be a certain system of multicellular life; etc., eventually to sapient life, intelligent life, community, intelligent community; technology, space, etc., etc., as if we were travelling along a flowchart with each milestone being a discrete destination and the path between them simply a necessary causal path. As an example, why not an abundant multi-cellular form + an assistance of several novel, but old, unicellualr forms + a very rare specific environment to reach sentient forms — where the bottleneck was not the multi-cellular but the rare specific environment — not a simple path of increasing existing complexity but a special ecosystem condition.
…And that’s just abiogenesis; what of panspermia or intelligent/ programmed seeding/ curating from beyond our small ‘solar’ eco-system?
…And that’s just within our ‘off-the-beaten-path’ spiral arm
…And that’s after nearly 14B years of expanding universe
My point is that we seem to often be spending so much time on wondering how many other places are like ours and assuming that as a reasonble cradle for life when perhaps we need to determine what cosmic conditions are the most likely for life-ingredients to become complex and how early that could have happened (assuming that the first complex life in the universe was abiogenesis).
When we proceed from the most likely in time and space, we can likely better understand ourselves and where to find whatever else we may be looking for wherever else.
My personal barely-informed opinion is that there has ever only been a bare few true abiogenetic civilizations within our galaxy (assuming that as the fundamental closed unit in which the most possible elements and conditions can exist) many billion years ago (off galactic core?), and that a certain number of those have evolved to a level of complexity that has spread — but started in a way more benevolent (thus likely) environment than our own.
Our civilization only exists due to the interventions of one of the original civilizations during the time passing since our local star formed it’s disk, rings, globs of matter along certain orbits, all within a certain goldilocks zone. Whether that intervention was to modify the planet, some of the local environments, seeding with the right ‘garden’ of ingredients, or some other social nudging, is anyone’s guess. So then, the idea that the amount of time that has passed, the tortured path of evolution, and the pin-hole routes to technological civilization in our history, in my mind, points to outside help, probably often.
The key then is to posit that most probable route in time and space, outward of such a civilization’s growth – if premised on ‘causing life’, if not spreading solely, would be the natural place to look(?) – though, I am guessing that this has been tried and is ongoing, which is not likely helped in premise, by this otherwise inspiring Paper. My 2c.
In one billion years there will be no Fermi Paradox. This is because a seed exists here and now – us – which will fill the galaxy. We are the existence proof for the future widespread population of the cosmos.
We can only use life’s early start on Earth as evidence that abiogenesis is easy if the example where randomly chosen. The early start could be coincidence or evidence that early Earth was an ideal environment for abiogenesis. Observer selection effect, the anthropic principle, doesn’t help since it applies equally to all choices. As long as the scenario includes an observer, the anthropic principle says yes to any explanation of the scenario. The Strong Anthropic Principle is just observer selection effect screaming yes. The anthropic principle can not increase the odds a scenario occurs. Imo, Earth being ideal is the stronger argument. Super rare coincidences are by definition, super rare. In the game of poker going all in blind assuming you will be dealt a royal straight flush is a dumb bet.
I favor a metabolism first or focused theory for abiogenesis. The young Earth hosted the wide spectrum of steeply inclined sources of free energy needed to push complex metabolism above a critical threshold. The slow accumulation of complexity may never allow abiogenesis. Frankenstein’s monster may only respond to a bolt of lightening. Trickle charging may be useless.
However we define civilization, along as entropy is assumed, a star system or any resource base will be depleted. Add bacteria or fungi to a petri dish and we will see one of two scenarios dependent on the species. The population will either expand to fill the dish and hit the Malthusian crisis at full speed or, well before it fills the dish, self impose F1. The latter will outlast the former. An observer randomly dropped in the dish will have limited success using a random search pattern to find the colony.
Everywhere we look we see organisms that traded population density, positive F, or positive occupation fraction, for positive Time. This isn’t surprising. Evolution is based on the assumption that agents compete for positive Time. Models based on the assumption that organisms must prioritize population density, positive occupation fraction or F do not conform to our understanding of evolution or evidence. Pessimists need to disprove entropy or argue that leaving a fat corpse is a more successful evolutionary strategy than living skinny.
I expect we will find many planets and moons with suspiciously active, prebiotic goo, very few worlds with life and, of those with life, a fare share with intelligence. If we posit civilization as mechanism that sufficiently intelligent agents employ to generate and democratize traits, evolution predicts an increase in the scale and capability of individual agents. If there is a finite number of discoverable traits, the utility provided by civilization diminishes. Agents will employ the combination of traits and occupy the niche that provides the largest value for Time. Optimists need to figure out what those traits are and where that niche is. We need to figure out what reality is made of first.
Imho, we are not ants living next to a highway. We are small industrious ants living near astronomically scaled ants in retirement.
H.S.,
Had to read several times – and maybe more yet – but this helped to tie several loose ends connecting the original report and the “comments” more general discussion.
A helpful analysis with some good illustrations worth keeping in mind. Thanks.
With the original article it was difficult to picture the problem
– or should I say pitcher the problem?
A quick thought on the likelihood of life arising:
First addressing this comment: One recent calculation shows that the probability of spontaneously forming proteins from amino acids is on the order of 10-77
Lets us assume that life is initiated through self replicating RNA chains that later incorporates of amino-acids to assist this—basically becoming a ribosome as the first step towards cellular life.
Self replicating RNA chains about 50 bases long have been made in the lab. So what are the chances of these spontaneously forming? If you have a correct base, there is a 1 in 4 chance the next base will be correct, and let us also assume there is an equal chance the chain will terminate at this point, so 1 chance in 5. The probability of randomly creating the correct chain is therefor 5^50 or 1 in 8 x 10^34. One averaged mole of a base pair with attached phosphate sugar weights approximately 360 grams, so 10^11 moles weights in at 3.6 x 10^7 ton of material needed. If you have a cyclic system like drawing in water through a central ocean vent where RNA chains are catalyzed then drawn into the hot vent to break down, this could work with a relatively small quantities on a planetary scale.
If RNA life started out with just two base pairs such as adenine and cytosine, the chance of self replication goes way up. 3^50 is 7 x 10^23, which is barely more than a mole of material. You could do this in a lab.
So if you have a cyclic system creating and recreating RNA strands, the odds of self-replicating RNA spontaneously appearing look good especially when you have 100s of millions of years to play with.
I have just listened to a lecture by Michel Mayor where he asks a beautiful question: “is life a cosmic imperative?” Mayor works on the formation of planetary systems which can potentially give birth to single-celled life through chemistry. It distinguishes well the research done by SETI which aims to find complex, intelligent, technological forms of life; therefore the approaches are very different.
I see that the article is exciting given the number of comments :)
Stephen Baxter’s “Creation Node” posits that life is so rare and sentient forms even rarer, that it needs a multiverse and possibly a 100 billion years across a bubble of universes in the multiverse to find another, humanoid ETI. This would be the extreme version of the Kipping & Lewis argument.
>Would we prefer to live in a universe with other intelligent beings, or one in which we are alone?
The question is interesting but the idea of communication should be included. Ideally, it should be bilateral between them and us, at least from us to them. Wouldn’t it be more frightening to be certain of having totally deaf blind and mute “neighbors” than to know oneself alone ? Let’s remember Helen Keller…
what’s happen if “they” are not equipped with the communication at least of the methods of communications that we know, whether physiological or technological. what would we then remain to chat with this ETI : organic chemistry like the pheromones of insects? the telephatie ?…brrr…I prefer to be alone:)
so, back to SETI: maybe other ETI are present but for a reason we do not know can not communicate. Not detecting them is one thing, their inability to communicate would be another.
It is easy to conceive of highly intelligent creatures or societies that are so physiologically different from us that we cannot communicate. In fact, there may be intelligent species out there we may not even be able to recognize as sentient!
Intelligence could arise in ecosystems; imagine sentient rain forests, coral reef civilizations, intelligent fungal communities in steppe soils. Technology could go in other directions than our physics/engineering model. ETI may be into chemical, acoustic, genetic technologies, or exist in environments that are simply incompatible with machines. Instead of fire and metals, perhaps they modify and sense their surrounding by breeding vassal and slave organisms instead. Our aliens may not only be incapable of building radios and spaceships, they might even be unable to conceive of them.
It is possible to imagine cultures that operate at such slow (or fast) speeds that we could be immersed in them and neither of us would be aware of the other. Without physical contact, we cannot possibly communicate across stellar distances unless both of us are familiar with Maxwell’s Equations. An advanced machine intelligence would not even appear ‘natural’, just a device with no obvious way of talking or listening or seeing, and that device might be distributed across an enormous number of orbiting nanogadgets. I have a smart TV I can’t program, I have to get my wife to do it for me.
OK, I’m making this all up, but can we rule any of these speculations out? Do we really expect them to land a saucer on the White House lawn and come strolling out in glossy plastic jump suits, speaking slightly accented English?
Perhaps the question we should be asking is not how many intelligent cultures share the galaxy with us, but how many are similar enough to us that we can even identify each other. We need a few more terms in the Drake Equation.
And what about communication? A highly intelligent cephalopod might communicate with its fellows using chamaeleon like color patterns on its skin. It might not understand our gestures, or even be able to hear our voices. Unless its carrying or wearing some artifact, we would not even be able to recognize it as a thinking being, much less an ambassador from a sophisticated civilization..
Without the mind tools as Dennett posits as our route to increased capabilities, paleolithic humans could hardly communicate with modern humans despite being the same species with the same sense organs. Maybe an anthropologist could make a little connection, but it would be limited.
I think you may well be correct in regards to types of intelligence and whether meaningful communication can be made between very different types. The hobbits could talk with the trees, but in reality, would trees and hobbits have any common frame of reference? This makes me think that the idea of AI intermediaries to communicate with aliens may be fanciful pixie dust unless they have the similar frames of reference as humans.
Cetaceans do not have a phylogenetic history of living in tropical forests with continuous overhead canopies associated with brachiation that brought binocular vision, depth perception, stereoscopic vision, prehensile hands, three-axis shoulder movement amongst other characteristics that distinguish humans from cetaceans. With our vision and our upper limbs cetaceans would be able to do a lot more.
Could we speak the language of dolphins? | Denise Herzing
October 30, 2015
In this IPaT Distinguished Lecture, Denise Herzing of the Wild Dolphin Project, and Georgia Tech professor Thad Starner present their cutting-edge work and recent results on the challenges of studying Atlantic spotted dolphins and decoding their communication signals using a wearable underwater computer.
https://www.youtube.com/watch?v=blmTrZMTcUs
Even more critical: Could an Orca Give a TED Talk? | Karen Bakker | TED …
July 18, 2023
What if we could hear nature’s ultrasonic communication — and talk back? From a bat’s shrill speech to a peacock’s infrasound mating call, conservation technology researcher Karen Bakker takes us through a sound bath of animal noises that are far outside humanity’s range of hearing, demonstrating how artificial intelligence has translated the incredible complexity of nature’s soundtrack.
She asks us to consider the moral weight of such transformative technology and explores the futuristic opportunities presented for conservation, interspecies communication and more.
https://www.youtube.com/watch?v=FvchLmGiXfY
underground mycelia in forest systems perform numerous functions attributable in other systems to neurological functions.
Cetacean brains are morphologically different from humans brains with structures not found in humans, besides being bigger overall. And some of the functions are more complex than in humans.
Just as in our search for ETI, we assume all intelligent beings want to meet and converse with us. Considering how unpredictable and dangerous our species is, I would say we need to reconsider this attitude.
Yes of course there are genuinely nice, considerate, and peaceful people. If there weren’t we would have wiped ourselves out long ago. It is the ones who are not nice and deliberately so that we need to pay heed to.
Higher intelligence sometimes merely gives an individual more ways to be selfish and destructive. This rule is not just for primates but cetaceans as well. I have read reports about dolphins that show them to be just as cruel and amoral in complex ways as humans, and I don’t think they even have a system of religion to keep them in check.
This is one of many reasons why I want to know about ETI: Are they truly civilized or not, or does their intelligence just give them new ways to behave like the baser creatures they evolved from?
Going to the source:
https://hakaimagazine.com/features/in-the-mind-of-a-whale/
How I Fell in Love with the Cetacean Brain…
https://www.youtube.com/watch?v=mOhfr23iHCY
Lori Marino: Dolphin Brains: An Alternative to Complex Intelligence in Primates…
https://www.youtube.com/watch?v=y-x9NgnZrdI
“Just as in our search for ETI, we assume…”
We?
Ron S. on August 20, 2024 at 20:07:
“Just as in our search for ETI, we assume…”
We?
It is a Royal “We”. Carry on.
Ooh, let’s not forget the cephalopods!
https://www.youtube.com/watch?v=t_R7QKmC0ug
and…
https://www.youtube.com/watch?v=ogCIqaCe2zI
The problem with cephalopods is their short life expectancy. Even the biggest ones live much less than a decade. And there is minimal parent-child educational interaction.
The problem with cephalopods is their short life expectancy.
Even the biggest ones live much less than a decade. And there is minimal parent-child educational interaction.
There’s a good question: Does one need long-term parenting so they can become intelligent and civilized?
Maybe some terrestrial organics do, but not Artilects.
And again, we have ONE data point to go on so far, Earth life.
Octopuses are very intelligent beings who memorize very quickly. However, they did not dominate in the chain of living because the mother dies too quickly without being able to transmit its experience to its offspring. Result: each generation of octopus must relearn almost everything so there is no evolution. The question of communication is therefore also linked to that of the transmission of acquired knowledge and thus to the time factor. We are already seeing the difficulties of communicating with a different species, which is part of our own planet. I don’t want to be too pessimistic but given the incredible diversity that can result from chemistry in the universe we may have trouble communicating with E.T. Intelligence is an ability to adapt to the environment in which the organism evolves. We can therefore assume “intelligent” beings in worlds that we consider impossible.We will have 2 planets 2 “intelligent” lives but a total impossibility to communicate.
Statistically, and in a radius close to our solar system, I remain skeptical about the fact that the basic organic chemistry could have evolved exactly the same way as we did to create Saturn V or an Iphone. It would be too beautiful. On the immensity, why not. In the best case, one could assume a technological evolution but which would be very different from ours, which signalizes that it would take time for us to really have an “exchange”.
Making contact is a first step, but then you need to know how to communicate. Of course, if a Type III calls us it will have no problem to decipher any of our metro plans:)
On a slightly tangential note, I found the Uplift books by David Brin quite an interesting read and concept. Specifically the idea of engineering “consciously close” species into current human level consciousness. In the books, humans engineered/uplifted species such apes and dolphins.
Currently we are bent on making artificial companionship but maybe the answer lies in carbon based systems rather than in silicon based systems.
Clarke wrote a short story “An Ape About the House” (1962) about an intelligent chimp. In the renowned, “A Meeting with Medusa” (1971) he followed up with aa crew of super chimps (simps) on the airship voyage that ended in disaster. Baxter and Reynolds expanded that story into a novel “The Medusa Chronicles” that expanded the role of the simps and their future of Earth’s, and AI’s history.
Baxter and Reynolds are more nuanced than Clarke, and IIRC, Brin, in that the uplift of the chimps is a mixed bag of benefits and problems. Our actual human history of “uplift” of indigenous humans has largely been a mess, with horrors still being found today. As for animals, I live within the limits that my cat has trained me to understand him. An AI that could accurately convert his actions and vocalizations to words would be of help. I really do not want him to be even child-level intelligent.
We have a wealth of intelligent animals on Earth who would be interesting to converse with, however limited, if we could. Whether AI successfully helps with this is still unknown. At least the communication would be with relatively “alien” minds with very different experiences.
Building AIs with human-level AGI has limited appeal, as they are a reflection of us, not truly different minds (assuming they eventually get them). Useful as companions and advisors, but not for truly interesting conversations outside the human experience. If AIs could indeed act as intermediaries for intelligent animals, a conversation with animals via AI translators, or AI proxies for animals, would be interesting, IMO. While animals will not have the level of perspectives we have, not they understand ours, they may offer unique, if simple, perspectives.
P K Dick sometimes had Neanderthal populations in his stories. There have been suggestions that we might use Neanderthal DNA to recreate these people, just as we are about to do with recently extinct animal species. I think recreating Neanderthals (or other extinct Hominids) is immoral and should not be attempted. We would unleash the very problems we seem to have inflicted on indigenous peoples, whether we tried to “uplift” them, or kept them in reservations [zoos].
While I don’t believe the “zoo hypothesis” is the answer to the Fermi Question, it does strike me that allowing us to live on our home planet without attempting to visit or especially to “uplift” us is a sensible, and moral POV. Brin’s aliens that uplift species, as with Clarke’s aliens that uplift Moonwatcher’s tribe (to save them, naturally), are examples of violating a “Prime Directive” which seems to be a position that is gaining ground as we expand out into space.
In some ways we are maybe talking past each other. I guess I am moving towards/conflating(?) are two slightly different, but, related notions.
1. Are we alone?
2. Can we talk to someone that is not us?
– AI is a path
– Aliens are another
– Maybe uplift can be yet another option
Brin’s story, and the others you mention, are indeed a reflection of our richly sordid past and I dare say this endeavour will have similar outcomes. However if successful, it would mean we are not alone, that there is another voice.
Though we don’t have precise answers to the Drake equation or even precise values for its inputs, there is much to be learned or considered in examining its probability factors. For example, when we consider the prospects of intelligence on Earth, we just noted how our own existence can result in tidal effects such as making domesticated animals intelligent as well. Or, more evidently, artificial intelligence associated with our machines and software. And then there are our ancient ancestors of which we know nothing of their languages, but have identified their DNA, tools and arts… If there were other circumstances leading to intelligent life on other worlds, the answer might be as nuanced or more. More than one intelligence could originate on another world – and have the potential to spread to others, perhaps at the same time. At the very least we already have robotic devices on other solar system worlds.
Still, a great deal of the frustration with this basic question is how much it rests on the assumption that physical evidence of visitation or effort to contact us should exist already if such beings exist.
Spotting a big enterprise in the sky would help validate ETI. But the further away it is the bigger the megalopolis and the brighter it has to shine. Whether individual consumption or collective, the argument is that higher civilization will need much more energy with resultant display. Much akin to the electric power company extrapolating customer future needs. Perhaps pitching to investors an unstable open loop plan… Aliens using the Kardeshev system receiving signals from Earth emitted decades back would scale us based on elements such as the Ford River Rouge auto plant, tallying up the terrestrial whole.
There is not much we can do if alien life actually exists but does not want to contact us in the spectacular manners we think befitting. And on the other hand, if we try to detect them, well perhaps the main attraction of a high level Kardeshev civilization IS its detectability. For those trying to maintain it, or faced with it as a potential way of life, it might not have ever been that attractive. It might even call into question the “intelligence” in the abbreviation of ETI.
With the assumed energy displays they just might not be worth the effort. Like spinning plates on bamboo canes as an act for the old Ed Sullivan show; spectacular to viewer in a way too, but nonsense as a way of life. Setting up more and more spinning dishes eventually reaches saturation, especially if drawing the energies of a star. Here spinning disks spectacle was sustained for the length of music accompaniment intervals, e.g., fast gypsy dances.
We can extrapolate such energy displays eventually for ourselves, in some respects. But it is often due to social features such as computational energy requirements, inclusive of features such as bitcoin mining or storing and tagging all our data. Civilizations capable of levels II or III likely should have curved their impulses earlier before they lost their plate spinning balance. Beavers in North America acquired the skill to build dams. They exploited the Missouri river valley, but didn’t subjugate it. Consequently, one might suspect some extravagant displays of energy somewhere in the cosmos, but suspect successful civilizations will be more subtle than that, standing out less from the natural fabric.
Maybe when we calm down a little someday, some of our more discreet spacefaring neighbors might stop by or say “hello”.
Interestingly, domestication of animals and humans, reduces brain-to-body mass ratios implying reduced intelligence.
With humanity, we can offload our thinking to physical and mental tools. For example, writing removes much of the need to dedicate brain areas to recalling facts, stories, etc. Mental tools such as how to manipulate numbers removes the tedious tasks of counting, and even counting is easier using physical tokens like pebbles, and placing them in small piles. So we can compensate for smaller brains with education and tools. Animals, not so much. In fact we want domesticated animals to have less intelligence as it makes them easier to manipulate.
As for uplifting animals, a more downbeat story is Olaf Stapleton’s Sirius (1944) about an uplifted dog. The reboot of Planet of the Apes saga follows a similar theme with the uplift of the chimp, Caesar.
More generally, and I mentioned this before, the answer could be that civilisation go in and not out. They either become virtual or create a more interesting universe.
Maybe that is the final filter, live in this safe place for eternity or create a universe (or at least a door to that “other” universe where everyone is hanging out).
Kipping’s et al’s fine paper and excellent video rightfully simulated a lot of conversation, analysis, and opinion.
I am Jim Benford’s camp: I too think the evidence against communicating civilizations in the stars is rapidly accumulating. But I would refine that statement to: any communicating civilizations, or their surviving machines, are too far away to have received their signals yet, or they sent signals so long ago that they have passed us by. It is the old synchronicity problem mentioned above by several others. (this thinking excludes exotic communication technologies by far advanced ET-civs which are not measurable)
What I thought missing in the discussion is the idea of the “needle in the haystack” analysis of how well we have searched for ETI’s presence, and what the “figure of merit” is across various searches.
Following this idea a little deeper (excuse the pun) a fascinating paper “How Much SETI Has Been Done? Finding Needles in the n-Dimensional Cosmic Haystack” (Jason T. Wright, Shubham Kanodia, and Emily Lubar, July 2020 in arXiv) updated Tarter’s analogy from a glass of water compared to the earth’s oceans, to that of a small swimming pool of 8,000 liters by comparison. This is 6X10^-18 of the total search space according to the paper which took into account Breakthrough Listen’s campaigns, and others, that happened after Tarter’s estimate.
However, Wright et al concluded that “…our haystack definition included vast swaths of interstellar space where we have no particular reason to expect to find transmitters; humanity’s completeness to subsets of this haystack—for instance, for continuous, permanent transmissions from nearby stars—is many orders of magnitude higher.”
Coincidentally (or not?) Jim Benford mentioned Marcy and Tellis’s search of the Milky Way’s Plane (MWP) for optical signals. I assume many radio searches have been made of the MWP as well and this caused me to wonder what the figure of merit is for the MWP.
The band of stars we call the Milky Way covers about 17% of the celestial sphere (I assumed a 20 degree wide band in steradians as a percent of the celestial sphere.)
If 60% of searches have been of isolated stars, globular clusters, or nearby galaxies which are not in the MWP, that leaves 40% of searches concentrated on the MWP. I have no idea what the true values are, it’s a thought experiment!
In refining the haystack size, what then is the comparative analogy for that subset?
My math follows Wright’s in that the total ocean volume is multiplied by the Haystack searched.
HAYSTACK SEARCHED IN THE MWP
6X10^-18 (Wright’s figure of merit) x 17% x 40% = 4.17E-19 (haystack searched)
OCEAN COMPARISON
1.34E+21 (liters in the oceans) x 4.17E-19 (haystack searched) = 5.56E+02 (liters or ~150 gallons.)
150 gallons is a typical size for a small water or fuel storage tank 52″ high x 32″ diameter.
I was surprised at the low value, and I hope my math is correct!
We have done so little real SETI because through most of its history, the efforts have been token ones at best. Yes, there have been a few long-term searches, but they remain in a few bands.
Check out this list of historical SETI efforts and you tell me how many would have had a real chance of finding anything based on their parameters and search times:
https://www.seti.net/indepth/history/history.php
We have also been stymied by decades of those who dominated SETI protocols with the parameters of searching for altruistic aliens who are beaming out radio signals from terrestrial type worlds circling Sol-type stars. In other words, versions of us.
Things are slowly starting to change around in SETI, thanks to advances in technology and the slow removal of the stigma about the possibilities for extraterrestrial life. Having proof of over five thousand exoworlds and climbing certainly helps in that regard. But we could do far more if we wanted to.
Another reason why we have yet to succeed with SETI can be found with a fellow named Jack Baird. He is a psychologist who wrote a book in 1978 titled The Inner Limits of Outer Space. It is “the first and only book to grapple with the psychological aspects of SETI.” That should tell you something right there.
See here for more:
https://www.supercluster.com/editorial/would-we-recognize-an-extraterrestrial-message-if-we-received-one
Thank you for this. I had never heard of Baird or this book. Scanned the Journal paper which made me reflect on how long it took to solve the human-created “alien message” for the “A Sign in Space” challenge.
I ordered a copy of the book too.
Many years ago, mathematician Keith Devlin gave a talk at SETI that challenged our assumption that mathematics was universal and therefore the best means to communicate with aliens.
Contact with ET using Math? Not so fast. – Keith Devlin (SETI Talks)
Thank you for this article. We often think in terms of technology, forgetting our own nature. We are influenced by our own culture and perceptions. Example: if I say “area 51” what do you think? I’m willing to bet that it wasn’t the composition of desert sand; the plants found there or ancient peoples who crossed this place:)
A perfect human “neutrality” in research is therefore almost impossible because we all have a history and we swim in a sum of knowledge that keeps accumulating what influences us etc. Another example: see how human species have perceived eclipses through time.
I like Baird’s idea that the message could be spread out in time that is not ours. Let’s be crazy: imagine an ETI that communicates its message in 1 billionth of a second, would we have perceived it today or 100 or 300 years ago? imagine a “call” on ultra-low frequencies divided into several pieces on each of our millennium (and in phase rotation or with a quantum binary encoding, to complicate the game) the signal may be there but we can not apprehend it.
we are therefore condemned in a research direction because we must choose one – and it is very good – but at the risk of going to price something else because the number of factors to master for this universal communication is still too important. We can therefore remain optimistic in the assumption that another ETI will be more developed and will adapt to our current communication possibilities.
I think Henry is on the right track. The problem is in the assumptions. To begin with, there is no limit on the amount of time available – if we take the logarithm, that is. If something evolved during the period of quark-gluon plasma, that tiny fraction of a second would have been a vast age of civilization, and its inconceivably tiny unit of length would have been a vast universe, and its environment would have seemed cold and empty – from its point of view. If something evolved before the Planck era, it might even have perceived the universe to have a different number of physical dimensions than we do. And if something evolves in the far future, when neutrinos gently drift into clusters and begin following rules of ‘neutrino chemistry’, such a beast much find a trillion trillion years to be just a heartbeat in its busy day.
Once something evolves, all bets should be off. You can’t predict what will happen to your identical beakers once a chemist has wandered through your lab doing experiments. A zoo, a nature preserve, a fancy computer trying to reverse engineer 42 … who really knows what our part of the universe is, and how its probabilities have been shaped by former inhabitants?
For that matter, is there any provable reason to assume there isn’t “alien life” here now? Stealth UFOs, smart microbes … even something as ubiquitous as graphene cosmic dust might turn out to have a sort of sentience, able to pattern itself and process vast amounts of information and energy. We won’t really be able to rule out the existence of such a distributed intelligence in the fallow places of space, until we are capable of building such a thing ourselves. I think unaided logic will always be powerless in the face of the deep unknown.
The discussion on “Odds of Empty Cosmos” has taken us up and down the probability factors of the Drake equation. And for one there an element of fundamental unlikelihood has been introduced with repetition of abiogenesis
repetition odds in one’s neighborhood as 10 to 77th to one.
Admittedly, I do not have the ability to re-check those calculations – and now and then I have argued that abiogenesis such as it is ( represented) makes it seem like perpetual entrapment in trying to relight an attic gas water heater. With that I shouldn’t say “nonetheless”, but an interesting link did show up on a feed:
https://pubs.acs.org/doi/full/10.1021/acscentsci.3c01108
Clearly, I would not be called on as a critical reviewer for such a paper. But I suspect that its research potentially opens a very wide door for phenomena such as ourselves in lieu of some of the scenarios and conclusions we are reaching.
My intuition is/was that there ought to be processes such as described that do more to level the playing field for repeated initiation of life. If the findings of the paper hold up well to critical evaluation, then a better case can be made for widespread prokaryotic life, maybe more. Maybe more in the sense that this cosmos appears to have an element of self assembly beyond physical chemistry.
In our discussions above, A.T. brought up the 1930s work of Olaf Stapledon, in particular “The Starmaker”. Stapledon’s cosmos was paradoxical in the sense that it was filled with life and potential radio correspondents, but it was also a cosmos with a true dearth of planets. Planetary formation was based on close and infrequent close passage of stars where matter was drawn out between them.
On that formation process and the odds, little did he know. But despite all this he elaborated on galactic wide societies of sentient beings originating from isolated and local events of abiogenesis. He didn’t understand his own odds.
Since then we have at least two developments. Planets are as numerous as stars in our galactic neighborhood by direct or indirect sampling. And we also have increasing evidence that the chemistry for life is / was underway before the planets formed. If the chemistry paper is more than plausible, then precursor chemistry should lace a variety of clouds: clouds where stars form and the vicinities where stars are lighting their hydrogen pilot lights. It might be a question more of when such chemical production might decrease or stop as circumstellar disks coalesce or disperse into planets.
Thermal Synthesis of Carbamic Acid and Its Dimer in Interstellar Ices: A Reservoir of Interstellar Amino Acids
Here is the abstract:
ABSTRACT: Reactions in interstellar ices are shown to be capable of producing key prebiotic molecules without energetic radiation that are necessary for the origins of life. When present in interstellar ices, carbamic acid (H2NCOOH) can serve as a
condensed-phase source of the molecular building blocks for more complex proteinogenic amino acids. Here, Fourier transform infrared spectroscopy during heating of analogue interstellar ices composed of carbon dioxide and ammonia identifies the lower limit for thermal synthesis to be 62 ± 3 K for carbamic acid and 39 ± 4 K for its salt ammonium carbamate ([H2NCOO−][NH4 + ]).
While solvation increases the rates of formation and decomposition of carbamic acid in ice, the absence of solvent effects after sublimation results in a significant barrier to dissociation and a stable gas-phase molecule. Photoionization reflect[i?]on time-of-flight mass spectrometry permits an unprecedented degree of sensitivity toward gaseous carbamic acid and demonstrates sublimation of carbamic acid from decomposition of ammonium carbamate and again at higher temperatures from carbamic acid dimers. Since the dimer is observed at temperatures up to 290 K, similar to the environment of a protoplanetary disk, this dimer is a promising reservoir of amino acids during the formation of stars and planets
=================================================
So far I’ve been most impressed by this idea: https://pubmed.ncbi.nlm.nih.gov/28952648/ The direct production of ribonucleotides on a mineral matrix seems tantalizingly close at hand, and once they evolve, a naked RNA-like form of life isn’t that far away. I suspect that within a decade some grad student will do abiogenesis in a flask over the course of a single day. And I suspect that parts of our biochemistry are still quite close to the reactions that evolve during those first first few hours. A curious consequence of this, if true, is that aliens, if evolved on their own planet for robust detoxification of poisons and pathogens, might just be able to eat us.
It is a jump from being able to create ribose sugar to getting these to form chain and bonding correctly only to the bases A,U,G,C to create self=replication RNA sequences as a simple start for RNA-World. I would like to see some evidence that happens spontaneously.
https://en.wikipedia.org/wiki/RNA
It’s a good point, and alas I can answer only with blind speculation. We know ribose is formed with hydroxylapatite as a catalyst. We know nucleic acids of all sorts bind hydroxylapatite well ( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2916501/ ), but from this article we also see they can be eluted with phosphate buffer, so there’s a potential for one phosphate-containing molecule to displace and free another.
If we can attach the ribose covalently to a phosphate in the mineral, we need only for it to react with some nitrogen-containing base to become a nucleotide. If that nucleotide can somehow react to make a 3′ linkage to another nucleotide, well, now we have nucleic acids.
The toughest part is the energy – where would it come from? RNA degrades spontaneously, not assembles, when we’re talking about monophosphates. Two guesses… The easier notion is that Hadean conditions dehydrated phosphate rocks and made polyphosphates – which our bodies even today use as a sort of energy storage interconvertible with ATP. If the initial hydroxylapatite formation contained a bit of this, it would have made a free energy source, which just needed some nucleotide to dip in and split it up, bringing out one phosphate and attached nucleotide to extend its chain. The tougher idea is that riboflavin is a nucleotide – the essential respiration electron carrier FAD actually contains it connected 5′ to 5′ with adenosine. Riboflavin actually absorbs sunlight. So bearing in mind that “RNA” in the early days would be a more unruly collection of nucleotides than today, we can picture that riboflavin or related compounds could have brought in solar energy to power the polymerization.
Either way, I think I’d expect early RNA life to catalyze reactions more as a lawn attached fairly closely to the parent mineral than as a long, complicated polymer reaching far out into the solution.
New Study Proposes how a Black Hole in Orbit Around a Planet Could be a Sign of an Advanced Civilization.
In 1971, English mathematical physicist and Nobel-prize winner Roger Penrose proposed how energy could be extracted from a rotating black hole. He argued that this could be done by building a harness around the black hole’s accretion disk, where infalling matter is accelerated to close to the speed of light, triggering the release of energy in multiple wavelengths. Since then, multiple researchers have suggested that advanced civilizations could use this method (the Penrose Process) to power their civilization and that this represents a technosignature we should be on the lookout for.
Full article here:
https://www.universetoday.com/168149/new-study-proposes-how-a-black-hole-in-orbit-around-a-planet-could-be-a-sign-of-an-advanced-civilization/