Opinions like these (I stop one step short of calling them findings, as this is speculation either way) resonate with me. I'm, too, more convinced by the Rare Earth hypothesis, and I find it quite plausible that we're indeed the sole sentient lifeform in the Universe - at least throughout the time of our existence.
This belief never gained me much popularity though. And this is what I'm fascinated about - how badly a lot of people take to this view. Even seemingly rational individuals seem to have some deeply ingrained, emotional need to defend the belief in ETI.
My personal theory is that this emotional mechanism is actually of religious nature; just in disguise. It's very telling that the most popular narratives involving ETI are usually quasi-religious.
The aliens would typically "teach us how to live in peace" (if we're willing to sit down and listen, of course), or turn away from us in disgust (for our sins), or scold us for our poor moral judgment and deeds; generally trap us in shame. Or they'd be quite diabolical and bring all sorts of plagues upon us, giving us a taste of our own medicine for we're wicked.
But the eschatological component is rarely absent either way.
Even this sceptical paper uses biased language through and through, consistently referring to the belief in the prevalence of ETI as "optimistic", and calling the opposite belief "pessimistic". But why?
There are so many other explanations for Fermi Silence - from the reality of extremely limited sampling to the creeping suspicion that we're too mediocre and underdeveloped to recognise truly intelligent life - that grand assumptions about our specialness seem more than a little premature.
None of this requires aliens who will teach us anything, one way or the other. It requires aliens who ignore us because we're about as interesting as a termite mound.
And once you've seen a few billion of those, you've more or less seen them all.
Not necessarily, because the principle collides with observer bias in this case. I don't think it's valid in this context.
"There are so many other explanations for Fermi Silence"
Of course. I'm not concerned about the explanations themselves though - more about the emotional dimension; the attachment to the underlying idea. Lots of people seem to yearn for the ETI to exist at all. They'd be fine with any of the explanations you mentioned to be true, as long as the core concept is protected.
"None of this requires aliens who will teach us anything, one way or the other."
My point is not that they would, or that it's a logical scenario. My point is that humans exhibit a strong cultural need for this type of narrative.
I'm interested in this anthropologically, so to speak. I don't really care about the actual aliens (or the lack thereof).
I realise this is kinda poking holes in Christian theology (always fun), and there are these kinds of questions for all religions. Can an alien reach Nirvana through meditation? Are there alien Buddhas? Are there Mecca-equivalents on all inhabited planets, or do aliens need to know the direction to our Mecca to pray?
The woo-woo "aliens are gonna come and teach us how to be better humans" is less interesting, I think. The underlying psychological need for some beneficent parental authority figure to come and solve our problems is almost too obvious.
Pet peeve, honed by endless discussions on Slashdot in the late 1990s: -ii is not a Latin plural marker. -i is a Latin plural marker which can correspond to a singular -us. Plurals can look like -ii, but only if the singular word ends in -ius. That's simply because you replace -us by -i, and if there was an i before the -us, then there will be an i before the -i. (Example: the gladiator's sword, gladius, becomes gladii. But one of those i-s is part of the stem already.)
Neither Jesus nor virus end in -ius, so their plurals can definitely, certainly, 100% never be Jesii and virii. They also happen to be words that end in -us but belong to declensions that don't use -i for the plural at all. (So no Jesi and viri either. "Viri" is a Latin word but means something else.) And on top of that IIRC virus is uncountable in Latin and Jesus is irregular even for the declension it sort of belongs to, and are proper names even countable?
Thank you for coming to my TED talk.
So what would the plural of Jesus be?
My name is Marcus, and I whenever I meet another Marcus, I wedge the "Marcii" joke in there somewhere. I would like to be able to refine this. What would two Marcuses (which sounds so wrong) be called?
Note that Marcus is a second-declension (https://en.wiktionary.org/wiki/Appendix:Latin_second_declens...) noun, which is the class where a singular -us turns into plural -i (again, only a single one).
But Jesus is fourth declension (https://en.wiktionary.org/wiki/Appendix:Latin_fourth_declens...), so if it has a plural, then in Latin it's something more like Jesūs (or, again, Jesus without the diacritic; I believe it only marks lengthening of the vowel, no change of the quality of the sound). But https://en.wiktionary.org/wiki/Jesus#Latin says that while it's fourth declension, it's also "highly irregular", and "singular only". It would seem plausible to me that the question never arose in Latin practice, because multiple people called Jesus could always be described as "multiple people called Jesus", and multiple instances of the Jesus would be an unspeakable heresy.
As for English, well. Though I was pedantic above, I should also note that I know that language is what people make it. If the vast majority of English speakers decide that the plural of Jesus is "Jesuseseses", then that's what it is, in English. Even if "just" a certain community decides on a certain usage, then that usage is what the plural is -- at least in that community's variant of English.
Having established that, https://en.wiktionary.org/wiki/Jesus#English lists "Jesuses or Jesi" for the given name and "Jesuses or Jesusses or Jesi or Jesii" for the noun denoting the Christian savior. The variants with i-s hurt my eyes (pun not intended, but I'll take it), and as I explained above, have no roots in Latin (or the Ancient Greek that Latin got it from) but try to look Latin while showing deep misunderstandings of how Latin works, so I would advise against them -- they don't make you look smart or learned. "Marci" seems fine in this regard, but again "Marcii" is not. (Interestingly, a bunch of the Wiktionary quotations for "Jesi" are of the form "Jesuses (Jesi?)", i.e., cases where the author was questioning themselves on this point, which is kind of weak for a dictionary.)
I would say that since -s is the dominant way of forming plurals in English, "Jesuses" and "Marcuses" are the most natural choices, inasmuch as forming plurals of given names can ever sound natural. But I'm not the English police (nor even a native speaker). Only the don't-randomly-double-i-because-you-think-that's-Latin police :-)
> And worlds without number have I created; and I also created them for mine own purpose; and by the Son I created them, which is mine Only Begotten.
The laws of physics results in occasional clouds of dust and water (life) that can contemplate their unlikely existence (humans).
The ~50% probabilities from the paper are not fundamentally more founded in reality than "Did another planet in our galaxy develop intelligent life yet that attempted to communicate? I don't know, so let's assume 50% either way. Therefore, we are alone with 50% probability." Should that number be 50%? Or 10%? Or 99%? You're choosing some prior there. So does this paper, and the priors chosen gravely affect the result. Of course, the paper has more intricate math and more solid reasons for their priors, but fundamentally it is still just assigning almost arbitrary probability distributions to parameters that we have no grasp on. Specifically (see my other comment), the numbers that they get primarily depend on the choice of prior distribution for the abiogenesis rate, which overshadows all other parameters. It has such massive error bars (>200 orders of magnitude by their own account) that arriving at a concrete probability (in the way that you understood it when reading the paper) is somewhere between misleading and a lie, because it's more or less just a projection of that prior into a single number.
In other words, I'm convinced they could have easily arrived at probabilities like 0.1% or 99.9% by reasonably varying their prior distribution for that parameter alone.
In other other words, this reading of the paper also confirms the general point it makes: The Drake equation is garbage-in garbage-out. There is no way to determine what numbers to plug into it. So let's just drop the whole unscientific nonsense.
I think you are misinterpreting the conclusion of the paper. The conclusion is that there is "a substantial probability that we are alone in our galaxy". This extra probability is because of the extra uncertainty within our estimates of the parameters in the Drake equation.
But "substantial probability" is something entirely different than being sure.
The keyword is "observable" universe what about probability of life in unobservable universe. When we discovered microscope and telescope only then you could say that we started "observing" something. Modern science is only 100 years old and we can not even imagine what would be invented and discovered for 50 or 100 years.
Maybe SETI search should add several terms to the drake equation to understand odds of hitting gold. Is not enough to be intelligent life, to be found in the way we are searching for it, distance, way of communication, culture, kind and stage of civilization, wish to be found, wish to expand, biology, and probably more are just terms in the equation that lowers the probability for us to find anything. There are too much implicit assumptions about what we are searching for, and maybe there is none that fits that because some basic rule that we don't know yet, as we are not advanced enough (a dark forest is just an example).
Is like assuming that advanced enough cavemen will be communicating across the galaxy with louder drums. And that as we hear no drums in space, there is no life anywhere.
fc - "the fraction of civilizations that develop a technology that releases detectable signs of their existence into space"
This term for many people, is near 1. They assume that "detectable" means that WE can detect them with our current level of technology, and/or that "releases" means that it would be something familiar like radio or laser beam transmission.
...but the scope of this assumption is based upon a scant hundred years of human history. The rate of technological and AI advancement (on galactic timescales) is so brief, it is imperceptible. ...and recall that if life exists, the average age of such civilizations would be hundreds of millions to billions of years older than ours.
When we look at popular sci-fi media, one thing that is blatantly obvious is our inability to even imagine what our "civilization" will look like beyond a few hundred years - and often those shows are even superficially wrong.
If AI surpasses us (or integrates us, or exterminates us), our technological existence to "release detectable signals" will be a relative flash in the pan. Remember that AIs aren't limited by our meat lifespans. To them, taking 100 million years to populate the entire galaxy, is a reasonable amount of time. To them, WE may not be the life they are looking for - the emergence of an AI might be of some significance (or perhaps even not), and we are just the slime on the surface of the rock. ...the precursor to what THEY consider THEIR abiogenesis.
...and if AIs encountering one another in space are constructive rather than combative, then the rate of abiogenesis may not be all that relevant. It might simply be like adding another drop of water to an already full glass.
This makes intuitive sense too — an early Great Filter simply has to stop life from occurring, while a late Great Filter has to deal with the complexity of preventing life from doing what it does best (surviving and spreading in a “Life finds a way” style). Concretely, an early Great Filter has fewer variables it must affect than a late Great Filter. Like the paper says, we are probably alone, but there’s little reason to be alarmed about it.
And if you happen to believe that AGI and a Singularity are the inevitable outcome of intelligent life, the case is even stronger that we are the first, last, and only. However powerful the Great Filter might be, it’s unlikely that a super-intelligence would succumb to it.
And that's just one of the many ways coming where any average person can decide to ruin the world. It's already possible today for a single rich person, if they wanted to, to destroy the world. I don't remember exactly how. Something like buy 1k airplanes and have them seed the atmosphere IIRC. Those kind o things get cheaper and cheaper until their in reach of your average joe
We don’t really have to imagine ourselves, since enough science fiction novels have already been written where humanity nearly extinguishes itself (sometimes multiple times) but then finally gets its act together. There would have to be something more fundamental than technological power being too cheap and widespread for a late Great Filter to get to 100% effectiveness. The only thing I can think of is that every super-intelligence checks out of our universe for some reason — that the ultimate end of technology is always effectively (if not literally) suicide. But this goes against the very nature of technology — to reshape existence to fuel the battle against entropy. Perhaps every Singularity sees that this battle can’t be won, and decides to call it quits? Maybe. But it seems more likely it would fight until heat-death itself.
In fact, there’s a great short story about that too.
If there’s hope in our imagination, I think it’s likely there’s hope in our reality too.
I might be wrong about this, but I think intelligence and benevolence are more strongly correlated than intelligence and malevolence, and that as the world becomes more educated, it is also becoming more intelligent and more benevolent. An evil-genius is a trope because it is an anomaly. For every evil-genius there are thousands if not millions of good-geniuses. Evil tends to look like Hitler and Stalin, not Einstein and Turing.
It won't be a 14-year-old that brings the world to its knees. It will be old men (and women, I suppose) spewing hate and lies from their Oval Offices.
That experiment/art project with E. Coli on a penicillin gradient a few years back was terrifying.
Sounds interesting to me too.
Most civilisations will have just enough of a life support to keep the machines running. They might be spurred into action each time a sun burns out, but other than that why bother with the outside world?
I think that at least some people (and when you're dealing with galactic timescales and spaces, this means a lot of people) would stay in reality to figure out how to get around entropy and heat-death.
So even though we might very well be in a simulation of VR-checked-out civilizations (or even if we aren't), I would expect to see some people in our simulation/reality fighting against the parameters of the simulation/reality that puts a time-limit on existence.
It also follows:
If it is possible that one civilisation spreads itself in this manner, it is likely that we are decedents of that civilisation. Simply because there will be many more copies of the original civilisation with a penchant for spraying their seed around than other kinds of civilisation.
An _actual_ replicating Von Neumann probe, that we can imagine working within the laws of physics today (even if we don't yet have the engineering capacity to build) can actually clone not just a couple of DNA strands, but can bootstrap an entire new sapient civilization, including technological progress, likely all the way down to the civ's culture.
I'm not so sure why this supposed to make intuitive sense. Life is a gradient, so any metabolic process that happens on a energy gradient can be considered 'alife'. I really don't see how an early Great Filter would work - are you going to stop energy gradients from happening? I've read -- will try to dig up the source -- that -- at least simple life -- is pretty much a given since -- even though it creates pockets of lower entropy -- allows for the most paths to thermodynamic equilibrium.
In my opinion a late filter makes more sense. That is; any species that evolves in the confinements of competition for resources and natural selection is -- due to the requirements that competition for resources creates -- necessarily unable to properly transition to a steady-state mode with no competition for resources and no (or limited) natural selection.
The reason for that is that the transition phase from competition for resources to the steady-state phase is simply too short. I'm convinced that this is what we are currently seeing with Humanity on a global scale; even though there's no need for competition for resources, we're still biologically and socially 'programmed' to compete with each other for resources, mates and habitats.
(Biologically, all humans are more closely related to each other than -- for example -- any two chimpanzee tribes. We are not very diverse, genetically.)
That inability to quickly change a species 'modus operandi' to a steady-state model together with the immense power multiplication of technology and cooperation that make it possible for civilization to literally dominate their ecosphere, I don't see how any species is ever going to survive that threshold.
The result of that inability to switch to a steady-state model and the powers achieved - tools and cooperation are the ultimate exploits! -- is simply extinction by habitat destruction.
I think that the current observations quite neatly match this.
The great filter is evolution converging to a local maxima and not evolving creatures capable of higher intelligence.
We're scared about the mass extinctions on Planet Earth while at the same time they were the ones that cleared the field for different animals to evolve. Case in point, the Dinosaurs going bust paved the way for small mammals (then large mammals, etc)
"But couldn't we have intelligent dinosaurs" maybe not? (Because of a bunch of stuff that only came later like animal packs, family life, etc - though it might be argued that some dinosaurs had that)
Then we have the fact that mammals are born much more frail than other species and needs "a family" to take care of them for a while (and human's big heads made that "while" into "a lot of time")
But without that you don't get societies organizing. And the bigger the society the more you can do with it.
Given the galaxy, and given billions of years, the Great Filters that seem most likely are the ones that occur on the edges of the timeline: before multi-cellular life begins, or after a hyper-dominant intelligent species arises.
Having said that, I think you’re absolutely right about mammals and societies. If the Great Filter does occur in between life and intelligence, it seems like it would happen where the first signs of intelligence begin. And for earth, that means mammals and the arms race of mind-modeling that their social lives initiated. No other type of animal on earth has parental-care so fully built into its biology: milk glands and placentas force mammals to be social from the start.
A great book that doesn’t deal with intelligence and mammals directly, but provides a key connection, is “Consciousness and the Social Brain.” The book makes a strong argument that consciousness sprung from evolutionary pressures that were essentially social — that being able to model (and predict) the mind of another is essential for communication and cooperation. But one can only model the mind of another if you first model your own mind, and thus, consciousness (which I would argue is just another name for general intelligence).
The idea that life in the universe will be comprised of humanoid-esque beings that have the same perception of time as us, or the ability to communicate in a "language", is just a human-centric idea. It's us, projecting our own worldview (which has developed through millions of years of evolution) on to the infinite universe. This is the fundamental problem with positivism; using your current limited sensory knowledge to construct a complete world-picture.
Even life itself is not a neutral word; it mostly just means "carbon-based entities like those on Earth." Perhaps the reason the universe seems so empty is because we only have the ability to see things like ourselves?
Well, we do see this behaviour in other animals, and not just humans, or mammals even.
I realise that's not broadening the net much - we share a common ancestor with everything that could be considered "living" on this planet, so ultimately it's all "human-centric" to an extent.
But if there are forms of life that are wildly different, to the point we can't communicate with them or even understand that they're "alive" in any meaningful sense, then that's kinda out of scope ;) The definition of "alien intelligence" only includes things that we would be able to recognise as an alien intelligence. Otherwise we're just talking to the trees, and they're dull conversationalists.
You just need to see what faint a signal we receive form the Voyagers, which are deliberately pointing their antennas at us and are thousands of times closer to us than any star to appreciate how improbable it would be for us to ever detect extraterrestrial communication.
I agree, but for different reasons. My favourite way to dissolve the Fermi Paradox is to simple state that the main assumption, i.e. "the lack of evidence of extraterrestrial civilizations", is just wrong :)
This is very sobering to read if true. It’s all on us. Life is even more precious than we thought and every human life extinguished even more of a loss to the universe. If we could only band together and see this.
I imagine that people attracted to this movement to either stay true to the "voluntary" aspect and pay with genetic demise for their mental susceptibility, or realize that their movement will be never manage to voluntarily attract the number of people necessary for movement's "success" and at some point look for more effective ways of achieving the said human extinction. Anyway, this is next level kind of awkward stuff.
The paper considers each parameter of the Drake as a probability distribution over some range. Notably, they assume that f_l in the Drake equation (the fraction of habitable planets that actually develop life) may vary over (at least) 200 orders of magnitude. Yes, you read that correctly.
Naturally, they thereby get a long tail of "planets essentially never develop life, even despite there being so many of them".
My main critique (as someone with no further credentials) is that the prior probability distributions they assume for the parameter distributions are more or less meaningless. Their results say "if we assume that the log of f_i (life-bearing planets that develop intelligent life) is uniformly distributed between log(0.001) and log(1), similar for other parameters, then the probability of being alone in the milky way is > 50%".
Specifically, by far the largest impact here is from assuming some distribution for f_l that covers 10x as many orders of magnitude (!) as the remaining parameters together. I'm very certain (but haven't done the math) that slightly tweaking the sigma they assume for the corresponding log-normal distribution (that sigma is 50 orders of magnitude) would drastically impact the results. They do a lot of dancing around that fact (discussing how little impact the priors of other parameters, or even the center of the log-normal distribution for f_l have), but fundamentally the result boils down to:
"We're extremely unsure how often abiogenesis happens, and this parameter dominates everything else." Followed by some math that (oversimplified) boils down to "if we set the rate of abiogenesis to effectively zero half the time, then half the time we are alone in the universe."
PS: Title should probably have (2018).
The entire Earth's history is hundreds of millions of data points.
Each year that a habitable Earth existed prior to life evolving can be seen as a data point. ... and with life emerging very very near its habitability transition, this reduces the drake error bars considerably.
The real limitation of the Drake equation is the duration at which life sends out radio signals - which given technological advancement and AI is probably only a couple hundred years.
Lacking any credentials on the subject whatsoever, and based on what (little) I know about abiogenesis, intuition tells me it happens with a probability of 1, if (and here's the key) the conditions are right, and given enough time. (A fun corollary of this is that intelligent life also happens with a probability of 1, under proper conditions ).
So, we just need to find how many planets have had the right conditions for a long enough period of time.
 p(abiogenesis)=1 + "evolution is a universal law" => p(intelligent_life)=1
Time and time again we have discovered that we are less special than we thought. Life appeared quickly after Earth was formed. I'm convinced the universe is teeming with life.
So the lack of huge radio transmitters that we can detect really just means aliens aren't investing huge amounts of money into letting us know they exist. Why would they? Especially if they already know of other civilisations.
About the required power and signal degradation over distance, see this:
Everything about UFOs is so implausible that the alternative explanation of "we don't know what we saw, but almost certainly not a UFO" seems to be much better.
This contextualises the issue and brings up the questions you mention. Without this imposed meaning the questions go away.
People like giving meaning to the unknown.
In common parlance UFO also means "spacecraft of extraterrestrial origin", and I very obviously used it in that sense.