A Statistical Estimate of Extraterrestrial Intelligence in the Milky Way Galaxy
arxiv.org
arxiv.org
We examine three major parameters:
1) the likelihood rate of abiogenesis ({\lambda}A);
2) evolutionary timescales (Tevo); and
3) probability of self-annihilation of complex life (Pann)
To my understanding:
1) Unknown.
2) Unknown outside earth.
3) Unknown.
Given the title and the problems above, I didn't read beyond the introduction as time is limited.
It sounds like an updating of the Drake equation without addressing the fundamental problems with that as an estimation tool rather than a more modest method for informing interesting speculation.
I think statistics is entirely bad approach to resolving this problem at least until we have more data.
We need to know more about how planets form (again, we have rather small sample we have studied well), we need to know what exactly is necessary to jumpstart life and how likely it is to happen. Then we have a hard task understanding why exactly intelligent life evolved and whether it is unavoidable or a fluke. And a bunch other questions that statistics is entirely unprepared to answer.
> 1) Unknown.
Abiogenesis is known on Earth. Life appeared quite soon after Earth had cooled down enough, within the first couple of 100 million years. Of course, we don't know if it took 1 million or 300 million years. And it might be difficult to find out.
Also, why do you consider "unknown" a problem when they explicitly set out to investigate the influence of these parameters? For example, they explore Pann of 0.0, 0.5 and 0.99 (per Myr). Could you explain what problem you see here?
That's a misrepresentation of what I said.
I made it clear I had only read as far as I had because the premise of the title was unpromising given the unknowns, and that it sounded like an updating of the Drake equation without its flaws in the calculating of probabilities (as implied by the title) addressed.
Feel free to summarise how it fundamentally differs from Drake in that important regard, with the findings and their usefulness in the context of the unknowns and title which promises an estimate of extraterrestrial intelligence.
Left over artifacts from their civilizations are just as exciting a find.
Personally, I feel the thought that we are alone in this universe is a wee bit arrogant.
The universe is so big and existed for so long, we have to assume that sentient life existed in the past, perhaps exists now and will definitely exist in the future.
Hopefully, we find at least artifacts that prove alien life, just because the minds of humans expand a bit more, because imagine how shocking it is to religions around the world if existence of aliens is confirmed.
If anything like us existed in the milky way it's almost certainly dead now. If there's something alive it will be almost incomprehensibly different than us.
I think this may be making some weird assumptions about motivation. Let’s say, for the sake of argument, that travel at 5% of the speed of light is practical. Would you be signing up to go colonise a planet around Alpha Centauri? What would be the motivation opportunity such colonisation? Who would pay for it?
If interstellar travel turns out to be permanently slow, difficult, and expensive, then that may cast doubt on the idea that anyone who theoretically can spread out all over the place given a hundred million years actually will.
But I think both of these opinions come from human-centric reasoning. A species that could hibernate may be able to control hibernation through technology, so a ten year journey wouldn’t be as complicated for them. Other species on earth simply don’t have the curiosity to explore the way humans do.
Speculation about alien intelligence is interesting to me, but I imagine it’s a lot weirder than we think. Especially around topics adjacent to intelligence, like curiosity, motivation, and cultural values.
Earth gives us a wide range of organisms with different lifespans and metabolic rates. There are not that many species that live longer than us, and extremely few that live significantly longer than us. Even if something lived 100 times longer than us, only a very small portion of the galaxy would be traversible within a lifetime, and there is still no reason to go more than a few lightyears.
the most convincing meta-analysis i've seen, which considers the probability distributions implied by the error bars in our current best estimates of the relevant parameters (https://arxiv.org/pdf/1806.02404.pdf), suggests a 39–85% chance we are alone in the observable universe. i'm less impressed by those particular numbers than by the attempt to rigorously quantify our ignorance on the issue, where some component values span fifty orders of magnitude. while the universe may indeed be big, i'm not sure it's broader than the sheer span of our ignorance.
Basically, the universe is so ludicrously huge and so ludicrously old that it is as close to statistically impossible as one can imagine that human beings are the only things ever to evolve in such circumstances as to be sapient.
Note that the paper you have linked uses the term "detectable civilization", which is significant limitation due to our current level of technology, the age of the universe, and the propagation speed of light. It wasn't that long ago that we couldn't even detect extra-solar planets.
There is of course an argument to be made for us being "alone" in the universe in the sense that sapience is rare enough that pretty much all species, including ourselves, will die out before ever meeting another sapience, but the idea that in all the unimaginable vastness of the universe we are the only ones?
In other words, the fact that it has happened at least once very strongly suggests it has happened more than once.
No, it doesn't at all.
Maybe just the opposite.
The universe is mind-bogglingly large, but it's also really, really empty, and really, rally sparse. The numbers games starts to dwindle very quickly in terms of all the ingredients necessary.
And the Fermi paradox helps provide crudely indirect evidence.
If there was any validity at all to the 'common life theory' - then it would have started long ago and probably spread everywhere to the point wherein there would probably be ample evidence.
In the 'common life' scenario, it should be rare/impossible to find life that's disconnected from other life scenarios.
There's a decent chance we are alone.
Maybe even out of 1,000,000,000 of similar universes only 1 would actually happen to have life. It's similar with planets. If you only know of 1 planet within 1B to have life, how can you tell the odds are not low enough to have 1 universe out of 1B to have life?
This could be an awesome example of survivorship bias to assume because there's life here, there must be life elsewhere in the universe too. We only have experience with a planet where there's life, so we are innately biased to think that it might be more frequent occurrence than it really is.
The non-existence proof of ETI also means laws of physics are cruel and cannot be violated. There is almost 100% chance that advanced life forms exist in other galaxies, may be even billion year old. But no one has figured out how to travel faster than light.
If anything I'd hazard our ignorance is more on the side of things we don't know we haven't observed than things we observed incorrectly.
I think compared to how long it took for somewhat intelligent life to evolve on Earth, from the point of first life. Assuming* a comparable evolutionary cadence, the question then becomes - how often does life begin?
*This I assume because the cadence of living things on Earth is at the very least tied to the day/night cycles, winter/summer seasons, and lunar tides, none of which are especially unique.
The common argument in favor of more life is that the probability of life evolving is some very small number, such that there must be a very large number of opportunities for life to evolve in order for life to actually evolve. At the same time, there are a large number of opportunites given the size of the universe. Given that there is presumably no relation between the "small" probability for life to evolve and the "large" number of opportunities in the universe, we don't expect these two numbers to conspire to be near the same size, which is what would have to happen for just one life to evolve. Rather, we expect there should be lots of life that evolved in different places or that the probability that any life evolved at all is extremely (vanishingly) small. So if this argument is correct and we know of one life form, we should expect many more in the universe. (Not to imply we would necessarily be able to find them.)
There is one potential problem with this argument. It assumes there is just one universe. If there are many universes then it is possible that life did not evolve in almost all of them. In universes where life did evolve, odds are it happened just once. And of course, that life (us, for example) would see that univese and the life that evolved there, however improbably that would be.
I read a saying "You know an argument is wrong if it invokes quantum mechanics." But I'll do it anyway. Some educated people believe quantum mechanics works this way - the univese effectively branches into parts that are essentially distinct (referred to as different universes too). It is not as outlandish as it may seem. The whole reason quantum computers are supposed to be powerful is that different things happen in parallel.
You don't have to buy the quantum mechanics part. If there are multiple universe for whatever reason then the probability argument above is not valid.
I do want to add one thing. The number of "opportunities" for life in our universe grows linearly with each dimension in the universe. (Lets just say to the fourth power of the size of the universe.) On the other hand, the size of probability grows/shrinks exponentially. So it is not hard to imagine between the two of these numbers, the exponential one wins.
For most I think that we are hear seems to indicate some inevitably but I like that we are an anomaly, we shouldn't exist, the we die.
An insult repeated to the point of cliche in this context which I suspect isn't normally personally meant, but nevertheless seems to deny the counter-arguer the abilities of imagination and wonder, and also presumes ("arrogantly"?) they haven't considered the known numbers first before coming to their conclusion that either there is little hope of communication or we don't know enough to decide.
Perhaps the evolving spectroscopic signature of our atmosphere will provide a durable signpost. The earth terraformed itself well before intelligent beings ever evolved, and maybe an astute and patient observer might have been able to guess that we were on our way towards intelligent life at some point.
Getting to complex cells took 2 billion years. And getting to where we are now another 2 billion years.
All that time conditions were fairly stable.
Given that life might need some elements created in supernova explosions mixed into other solar systems, and that we had just 13 billion years since the beginning, when you add some randomness, schedule starts to look tight for me.
We might be one of the first civilisations in our neighborhood.
I'm not saying that I believe that's the case but that's entirely possible.
This matters because, as far as we can see, our solar system has more planets than any other system we have been able to observe (so far.)
See https://www.sciencenewsdigital.org/sciencenews/december_19__..., article #9 (subscription required.)
I may be out of date, but I thought that was an artefact of our methods and equipment rather than anything else — we can only see big things close to their stars, so if we were looking at our own system we’d miss (I forget, so e.g.) Mars, Uranus and Neptune?
“ We also concluded that at the current time of the study, most intelligent life in the Galaxy is younger than 0.5 Gyr, with values of probability parameter for self-annihilation between 0 - 0.01; with a relatively higher value of the annihilation parameter (≥ 0.1), most intelligent life is younger than 0.01 Gyr.”
If other intelligent life is very young (just like us) could there be more room for understanding if we ever communicate?
I suspect we will barely recognize even alien sentience, since it will literally be alien to our understanding
Would you mind expanding on that? Why would intelligences being young mean we are more likely to understand them?
Yeah... this is why I suspect we may see signs of alien life, but just not know what we're looking at. You're not alone in thinking of intelligence as some kind of scalar quantity from bacteria to super beings, and if only we could find creatures in our range, we'll be able to communicate
Embedded in our conception of intelligence is us. We measure intelligence by what we think is important. But creative approaches to fitness in radically different environments will be multidimensional and multivalent, extremely difficult to judge by our own standards
I speculate that if we were to find aliens, we could never communicate beyond basic Skinnerian reward and punishment schema, if that, never mind prime numbers and such, no matter how sophisticated they are. We wouldn't even really be certain if we were witnessing intelligent behavior or autonomic processes, and neither could they. We can't even understand whales or dolphins, and those would be vastly easier to understand than anything without DNA, emergent from a completely different planet
How could we possibly communicate with a civilization that communicates in the time scale of oaktrees, or are sessile, or communicate using flashes of microwaves in patterns we have no hope of even discerning?
Time's too big. There's no reason to assume that the lifetime of technological civilization is more than a few hundred years. By then they will have destroyed their own habitat and - despite some half-hearted (or even serious) attempts on colonizing different planets/planetoids - will have come to an inglorious end.
Let's be generous and say that the lifetime of a technological civilization is a thousand years. That's the time that it can both send and receive signals from another technological civilization.
The chance that one technological civilization is able to receive the signals of another is so vanishingly small as to be zero for all practical purposes.
Correlation, if any, does not imply causation, and the causality principle has nothing to do with statistics.
Observations (counting), however many, will never reveal causality, because they are orthogonal.
The same day I saw the King Tut exhibit I also saw an exhibit from feudal Japan. The workmanship of the Japanese items was absolutely stunning, much more impressive than the King Tut items as one would expect from a period many centuries later. All of these examples were still done by hand. It's hard to imagine a person in the modern era devoting a lifetime to make only a handful of swords.
What makes these items interesting is that they were made without modern tools or technology. Today our manufacturing technology could replicate these achievements easily. Even common items like grave tombstones can be produced in short order with highly polished stone and precise engraving. See [1].
Given the wide variety of environments where life can reproduce, shouldn't even non-sentient life eventually escape into space? This removes many of the 'great filter' arguments. This would be more likely on a planet with a shallower gravity well than earth.
Life, even bacterial-level life tends to spread out exponentially as resources allow, which should make it easier to detect.
Ignoring all extinct species, there's an estimated 8.7 million unique species of plants and animals currently on Earth. So let's do some dumb estimating and say that there's a one in 10 million chance of "intelligent" life evolving on a planet that supports life. (I will not address the controversial issue of whether or not human life is actually intelligent.)
So whatever estimation is used for the number of habitable planets in our galaxy, Only 0.00001% of those planets might have intelligent life. Next, you must factor in how many of the intelligent species develop technology capable of interstellar communication, and when do they do it? Humans have existed for a few million years, but we have only had radio for a hundred years. With the development of technology comes the risk of self annihilation. We humans have had the ability to destroy ourselves for roughly 60 years. How much longer we go is anybody's guess, but given that life on our planet has existed for roughly 3.5 billion years, and the planet will become uninhabitable in another 5 billion (when the sun changes modes), the time window is pretty small. It's likely that life needs some elements that were less available in the early universe, so let's assume that it's only possible on planets of third-generation stars like ours. Also consider the speed-limit of EM propagation (C). There are only 76 stars within 100 light years of us. It's unlikely that intelligent life exists in any of those systems, but if it did, the inhabitants (if they were listening) would just now be able to hear us. Assuming we survive our technological revolution/evolution for another 100 years, we might get a message from a nearby system. Before then, we might receive some communications from systems farther away, but how long does a technological civilization use radio with simple modulation schemes that we would recognize as something other than noise? Maybe in less than a hundred years, we will have gone through radio, optical, and then quantum communications technology. It's likely that other technological civilizations (if they exist) are using communication technology that is incompatible with ours.
I'm not sure if Drake considered all of these things, but it looks pretty bad for us with regard to our ability to confirm the existence of extraterrestrial intelligence any time soon.Isn't that the probability that a species is intelligent. The probability that intelligence will eventually evolve on a planet with life is 1.0, from the evidence that we have so far.
Also, Earth has had numerous extinction events that killed off at least 3/4 of land-based life (and 96% of marine life). We have no way of knowing whether extinction events are more, or less common on other habitable planets, or whether such events might even be necessary for the evolution of intelligent life.
A person who has a 1 in a million chance to win the lottery CAN still win the lottery. And if he does win the lottery, his chances of winning was STILL one in a million.
Same with life in the universe. Just because it happened does not make the probability of it happening at all 100%. Far from it.
Even right now on Earth, we have multiple tool-using species spanning mammals, birds, and cephalopods, separated by hundreds of millions of years of evolution. They all seem like good candidates for developing technology at some point over a few million years.
Progressing to that stage this seems unlikely for a planet with life on.
As for the sudden nature of humanity's major technological advances, that's just the nature of geometric growth - every advancement makes more advancements easier. The humans that took thousands of years to go from agriculture to writing were biologically no different from and no less capable than those who went from first flight of a plane to first walk on the moon in a single lifetime.
The most recent common ancestor with our primate cousins was about 7M years ago. There have been various hominid species, but I don't think we call them humans. I thought the general rough guess is homo sapiens are on the order of 200K-300K years old.