Are humans unique and alone in the vast universe?
May 21, 2016 1:12 PM   Subscribe

A New Empirical Constraint on the Prevalence of Technological Species in the Universe
Recent advances is exoplanet studies provide strong constraints on all astrophysical terms in the Drake Equation...We find that as long as the probability that a habitable zone planet develops a technological species is larger than ~ 10-24, then humanity is not the only time technological intelligence has evolved.
(Paper published in Astrobiology [paywalled]; preprint available on arXiv)

Researchers from the Universities of Rochester and Washington explore how recent exoplanet discoveries impact the Drake Equation (previously). From the press release (with accompanying visualization tool):
By applying the new exoplanet data to the universe’s 2 x 10 to the 22nd power stars, Frank and Sullivan find that human civilization is likely to be unique in the cosmos only if the odds of a civilization developing on a habitable planet are less than about one in 10 billion trillion, or one part in 10 to the 22th power.

“One in 10 billion trillion is incredibly small,” says Frank. “To me, this implies that other intelligent, technology producing species very likely have evolved before us. Think of it this way. Before our result you’d be considered a pessimist if you imagined the probability of evolving a civilization on a habitable planet were, say, one in a trillion. But even that guess, one chance in a trillion, implies that what has happened here on Earth with humanity has in fact happened about a 10 billion other times over cosmic history!”
Elsewhere in news of the universe: Mega-Tsunamis Wiped Away Shoreline of a Martian Ocean
(full paper available as an open article from Scientific Reports)

Articles best read while listening to Voivod's Astronomy Domine and We Are Not Alone
posted by Existential Dread (57 comments total) 18 users marked this as a favorite
 
It's too soon to make a judgment like that, because the approaches we are using now to detect exoplanets induce selection bias in which planets we find. In other words, they aren't a representative sample.
posted by Chocolate Pickle at 1:21 PM on May 21, 2016 [5 favorites]


It is amazingly arrogant to assume that we are alone in the universe.
posted by grumpybear69 at 1:31 PM on May 21, 2016 [3 favorites]


Say it with me now: "You are not special. You're not a beautiful and unique snowflake."

What would a representative sample of exoplanets be? Sure, maybe you could get one for this galaxy, during this period of galactic light time, but on the whole even that wouldn't necessarily be representative of the universe as a whole.
posted by anarch at 1:31 PM on May 21, 2016 [1 favorite]


It sure feels alone here on this planet with... seven billion other people ?
posted by Pendragon at 1:32 PM on May 21, 2016


I haven't read the paper yet, but the abstract discusses setting "a firm lower bound' - I'm not sure the selection bias objection is terribly meaningful in this circumstance? I doubt they're saying "we expect X% of stars have planets, and Y% of planets we've seen are habitable"; it's much more likely that it's "of a sampling of N visible stars, at least Z% of them have habitable-zone planets". Unless your objection is that we're only looking at stars that are disproportionately likely to have planets? And even in that case, one can correct the lower-bound calculation by assuming that none of the types of stars we haven't looked at have planets.
posted by NMcCoy at 1:35 PM on May 21, 2016 [2 favorites]


It is amazingly arrogant to assume that we are alone in the universe.
posted by grumpybear69 at 1:31 PM on May 21 [+] [!]


...unless you're 15 and he/she won't return your call...
posted by From Bklyn at 1:35 PM on May 21, 2016 [2 favorites]


Ahh yes, the Drake equation. A mathematical equation saying that if you take a smidgen of actual scentific knowledge and then multiply it with conjecture, hunches, wild guesses, random decisions, the unknown and the unknowable, you will have done mathematics about the probability of the existence of "civilizations", a concept mostly abandoned even by anthropologists here on Earth.
posted by Pyrogenesis at 1:44 PM on May 21, 2016 [6 favorites]


It could still be that evolving higher life is hard enough that our nearest neighbors are halfway across the universe, right? We would be effectively alone, still. Do their results rule out this likelihood?
posted by polymodus at 1:53 PM on May 21, 2016 [1 favorite]


Lots of other intelligent civilizations, and in a few thousand years when we have a few tens of thousands of space telescopes each several hundred miles in diameter floating out beyond the Kuiper belt running a survey of planets in other galaxy's we'll get fuzzy signals of their local sitcoms knowing that theirs suns probably went nova a million years before ours was formed.

They are were out there.

long long ago
posted by sammyo at 2:03 PM on May 21, 2016 [1 favorite]


Or what polymodus said :-)
posted by sammyo at 2:09 PM on May 21, 2016


Given only one indubitable example of life, almost anything is possible. We might be the only living things in the entire universe. Or life could be fairly common, and our very limited searchings simply haven't happened to turn any up.

This study doesn't rule any of these extremes out - it simply puts bounds to the mathematical picture we have, given we have a vaguely better idea of how many exoplanets there are.

> It is amazingly arrogant to assume that we are alone in the universe.

It is just as arrogant to assume that are we not. Pending the slightest evidence either way, a skeptical person can only say, "Unproven".
posted by lupus_yonderboy at 2:22 PM on May 21, 2016 [7 favorites]


In what way exactly is it arrogant to think that we're commonplace and the universe is seething with all sorts of life?
posted by Pyrogenesis at 2:28 PM on May 21, 2016 [3 favorites]


It is irresponsible to assume that there is life elsewhere. As cosmonaut Yuri Glazkov put it:
After eighteen days of a space mission I was convinced that all visible space—the black emptiness, the white, unblinking stars and planets—was lifeless. The thought that life and humankind might be unique in the endless universe depressed me and brought melancholy upon me, and yet at the same time compelled me to evaluate everything differently.
Nature has been limitlessly kind to us, having helped humankind appear, stand up, and grow stronger. She has generously given us everything she has amassed over the billions of years of inanimate development. We have grown strong and powerful, yet how have we answered this goodness?
Most people don't seem to give a shit about the well-being of their own planet. All this talk about exo-biology is just a way to make people feel better about trashing this place.
posted by No Robots at 2:50 PM on May 21, 2016 [10 favorites]


All this talk about exo-biology is just a way to make people feel better about trashing this place.

Or maybe, just maybe all this talk about exobiology is a way for us to think about the awe and wonder of an immense universe. There doesn't have to be an ulterior motive.

Besides, if you want to go after people looking for an excuse to trash this place, start with the vast number of people who believe we live in the Biblical end times, and once they're sorted out, you can talk to the exobiologists.
posted by chimaera at 2:54 PM on May 21, 2016 [11 favorites]


Say it with me now: "You are not special. You're not a beautiful and unique snowflake."


That has nothing to do with it. I hate this binary mode of thinking. Of course, in some ways we are unique and special and in other ways we're not. What's with the impulse to pick one wrong bias over another? The truth is more complicated and resolves all the seeming dualities; like how it's always both day and night at once when you take a big enough picture view.

I'm sure there have been all kinds of civilizations before ours. Who knows if weed ever even be able to recognize the signs well enough to distinguish them from natural processes, though.
posted by saulgoodman at 2:55 PM on May 21, 2016 [3 favorites]


It is just as arrogant to assume that are we not.

Someone didn't pass their Law of Large Numbers quiz. It's a safe assumption that intelligent life exists in more than one place in the universe. The converse is definitely NOT the safe assumption.
posted by chimaera at 2:56 PM on May 21, 2016 [5 favorites]


To add: that doesn't mean there's intelligent life anywhere nearby (for astronomical values of nearby, which again, REALLY big numbers are involved), or that there is any feasible means by which to detect or communicate with it. But I feel very, very safe in assuming we're not alone.
posted by chimaera at 2:59 PM on May 21, 2016 [1 favorite]


[I]f you want to go after people looking for an excuse to trash this place, start with the vast number of people who believe we live in the Biblical end times, and once they're sorted out, you can talk to the exobiologists.

Any scientist wanking about exo-biota while we're in the middle of a mass extinction event right here is definitely part of the problem.
posted by No Robots at 3:05 PM on May 21, 2016


Any scientist wanking about exo-biota while we're in the middle of a mass extinction event right here is definitely part of the problem.

You have an awful wide net for what qualifies as part of the problem. I'm no astrobiologist, but if you're making a list of people who are part of the problem with this kind of criterion, you'll have to put me on your list. I think I can live with that.
posted by chimaera at 3:07 PM on May 21, 2016 [12 favorites]


We require leadership from our scientists, not infantile speculation.
posted by No Robots at 3:09 PM on May 21, 2016


Did a SETI astronomer run over your dog?
posted by chimaera at 3:12 PM on May 21, 2016 [23 favorites]


Another poster suggested there is a moral dimension to this subject area, and so I felt at liberty to moralize a little myself.
posted by No Robots at 3:19 PM on May 21, 2016


I contend that it's likely you're barking up the wrong tree.
posted by chimaera at 3:21 PM on May 21, 2016


Down, you two.
posted by Chocolate Pickle at 3:25 PM on May 21, 2016


>> It is just as arrogant to assume that are we not.

> Someone didn't pass their Law of Large Numbers quiz.

I'm an engineer with a degree in mathematics in active use.

> It's a safe assumption that intelligent life exists in more than one place in the universe. The converse is definitely NOT the safe assumption.

Sorry, you are wrong. You simply have NO idea what the chances are, based on a sample of one.

Indeed, I'll let you fix the values of all the variables but one in the Drake Equation to be anything you please - as long as I get to set that last one, I can set it sufficiently low that the chances that there is any other intelligence, or even any other life, in the universe is vanishingly small.
posted by lupus_yonderboy at 3:29 PM on May 21, 2016 [2 favorites]


Unless your objection is that we're only looking at stars that are disproportionately likely to have planets?

We don't know. That's part of the problem.

It's not just that our sample is biased; we don't know what the bias is.
posted by Chocolate Pickle at 3:29 PM on May 21, 2016


And to be clear, I suppose what we're arguing about is, "Will we ever know anything about other intelligences?"

If some current theories are true, there could be many multiverses, or the universe could repeat cyclically forever. If the universe is infinite, given that we know life is possible, it has to happen infinitely often.

But given a finite universe, and given the fact that we have only one example of life and a paucity of data, we really have no idea if life is something that happens one time in a billion, or one time in a googol and we just happened to be there for that one time.
posted by lupus_yonderboy at 3:33 PM on May 21, 2016 [1 favorite]


Given that every human is, in fact, an unironically beautiful and unique snowflake, it doesn't seem unfair to view humanity as a whole as one as well.
posted by qntm at 3:43 PM on May 21, 2016


It's Koch snowflakes all the way 'round.
posted by No Robots at 3:48 PM on May 21, 2016 [1 favorite]


I remain irrationally hopeful that we might be the only intelligent life in the universe that is just like we are. I wouldn't wish Humanity As We Know It on any other poor planet.
posted by oneswellfoop at 3:57 PM on May 21, 2016 [1 favorite]


To me it seems inevitable that there will be life elsewhere, the interesting question is what is the average distance between systems with life. Because of the expansion of the universe we will never be able to communicate with or travel to anything more distant than around 4740 megaparsecs, corresponding to galaxies with a red shift of about 1.69, as they recede from us apparently faster than the speed of light and the light they are emmiting now will never reach us (ref). So we might not be alone, but we might effectively be alone.
posted by drnick at 4:11 PM on May 21, 2016 [9 favorites]


The basic problem is unchanged: We don't know the numerator for many of the terms we need to figure out the odds that other technological civilizations ever existed. We have zero idea. There is no empirical evidence to support even a wide range of estimates. Giving more precision to an already very large denominator does nothing to help us figure out the end result. People intuitively want to say, well, it might be small but it can't be that small, as in the quote above: Thinking the per planet odds were one-in-a-trillion is pessimistic, so one-in-a-trillion-trillion is impossibly small! One iota evidence that either or both of those numbers are larger or smaller than the actual odds is not offered.

I will also add something on the arrogance side. that I think one of the reasons for finding the "it can't be that small" appealing is precisely because people think we are special in some way. It's trivial for things to happen that have a 1-in-10^24 chance of happening. Just throw 24 ten sided dice (or 7d34 if you prefer) and write down the numbers in order. Congratulations! Something unimaginably unlikely just happened--the only reason people aren't saying it was impossible is because they attach no meaning to it. We attach meaning to life and it's really hard not to think of ourselves as being an important product of history, not just a bit of random chance the universe doesn't give a damn about.
posted by mark k at 4:15 PM on May 21, 2016 [6 favorites]


I wouldn't wish Humanity As We Know It on any other poor planet.

Trump le Monde?
or: This is the Planet of Trump?

Other intelligent species out there: Destroy us immediately or back away very quietly. We cannot be reasoned with.
posted by Dumsnill at 4:17 PM on May 21, 2016 [2 favorites]


Adam Frank discusses the paper in this podcast from the public radio station affiliated with the University of Rochester.

it might seem arrogant to some to try to work any of this out, but the original arrogance I guess is Drake's, isn't it? How dare we silly little monkeys even contemplate these sorts of things, right?

Anyway, Frank comes to this from asking "how long do technological civilizations last?". As in, do they all blow themselves up in nuclear holocausts or cook themselves with, oh, say, runaway global warming? Or, do they figure it out somehow and get through it long enough for us to hear them?

(Disclosure: Never met Frank, but I live and work with people who work with him.)
posted by one weird trick at 4:29 PM on May 21, 2016 [2 favorites]


The real arrogance is believing that we could possibly have more in common with creatures from other planets than we have with those on our own.
posted by No Robots at 4:45 PM on May 21, 2016


The conclusion is reasonable.

The more important question is how much longer will somewhat intelligent life exist on this planet.

It certainly looks as though there's an intelligence threshold below which life will fail. Experiment in progress.
posted by Twang at 4:46 PM on May 21, 2016


I'm uncomfortable with assuming a usable, uniformly applicable definition of intelligence to assess if we are the only intelligent species. We're barely able to get a handful of our number out of our planet's gravity well, and the universe is incomprehensible to us in its sheer vastness, even what potentially small part of it is visible to us. We may be the functional equivalent of bacteria on parasites on ants - with no realistic way of ever having perspectives or descriptions extrinsic to our own mathematical language. At best, maybe we will be lucky enough to come across remnants of civilizations past that we could only learn about in limited ways — information that is encrypted or scrambled by any intelligence advanced past our own will be likely lost to entropy forever.
posted by a lungful of dragon at 5:06 PM on May 21, 2016 [1 favorite]


None of this surprised me, except that Voivod once covered "Astronomy Domine" and I somehow had missed it. Thanks for posting!
posted by not_on_display at 5:44 PM on May 21, 2016 [2 favorites]


>We require leadership from our scientists, not infantile speculation.

I'm a scientist, and I can't even get my Facebook friends to take me seriously.

Less important than the numbers is acceptance of the *possibility* of other life forms. I'd hope that a person who took that possibility seriously would also take climate change seriously, and would be concerned about the life on this planet.
posted by acrasis at 5:51 PM on May 21, 2016 [8 favorites]


We require leadership from our scientists, not infantile speculation.

I think this is a terrible idea. We need scientists to do scientific work. There are issues where clear scientific data is vital to making the right choices. That doesn't mean the ones producing the data should be making the choices. The last thing you want is scientific work being done with policy in mind. As Chesterton said, it's up to my private physician to tell me which food will kill me, but it's up to my private philosopher to tell me whether I ought to be killed.
posted by pattern juggler at 8:07 PM on May 21, 2016 [2 favorites]


Relevant.
posted by Autumn Leaf at 8:12 PM on May 21, 2016


It could still be that evolving higher life is hard enough that our nearest neighbors are halfway across the universe, right? We would be effectively alone, still. Do their results rule out this likelihood?

There results don't really rule anything in or out, but to address this specifically, the odds are for any technological intelligence at any time and (I believe if I skimmed the article correctly) any galaxy. Divide by the appropriate factors if you're looking for something "close" and currently existing.
posted by mark k at 8:17 PM on May 21, 2016


The thing is, we know only the following for sure:

We have not seen any sign of a technological society out there.

We have no evidenceence that the Earth has been visited/colonized in the past.

From fairly conservative estimates of what a technological culture could do in the long run, we should have at the least detected a civilization- hell, they should have colonized the galaxy already.

The combination of those items leads to some really pessimistic conclusions: either other civilizations aren't out there, civilizations don't last long, or it's pretty much impossible to live off a planet.
posted by happyroach at 8:18 PM on May 21, 2016


Practically, yes.
posted by bonobothegreat at 9:20 PM on May 21, 2016


It might be that civilizations do not stay in the radiowave communication stage for very long. Keep in mind that with our current radio telescopes, we would have a hard time detecting a civilization at our own level of development even if it were right next door at alpha centauri. We could be in the middle of an empire and not notice because they communicate with 'hyperwaves' or somesuch. If intelligent life is especially abundant, we might simply be too non-notable for anyone to care to visit.
posted by Pyry at 10:30 PM on May 21, 2016


I think this is a terrible idea. We need scientists to do scientific work. There are issues where clear scientific data is vital to making the right choices. That doesn't mean the ones producing the data should be making the choices. The last thing you want is scientific work being done with policy in mind. As Chesterton said, it's up to my private physician to tell me which food will kill me, but it's up to my private philosopher to tell me whether I ought to be killed.

No problem. My policy position, then, is to ensure that there is no government funding for exo-biology.
posted by No Robots at 10:49 PM on May 21, 2016


No problem. My policy position, then, is to ensure that there is no government funding for exo-biology.

Is there any evidence government money was spent on this? Forgive me if I am missing something, but it seems like your complaint is that anyone is doing anything less than utterly vital in the sciences (or at all).
posted by pattern juggler at 11:07 PM on May 21, 2016 [2 favorites]


Having read Three-Body Problem, this paper fills me with dread. Humanity must set aside its petty differences and devote every resource to the development of planet-busting superweapons. Once we have these we must take steps to fortify our solar system, before launching simultaneous, devastating sneak attacks in all directions against the implacably hostile civilizations we must assume are out there somewhere.
posted by um at 2:49 AM on May 22, 2016 [2 favorites]


Elephants wonder about the possibility of trunk-bearing life in the universe....
posted by miyabo at 6:17 AM on May 22, 2016 [1 favorite]


> That has nothing to do with it. I hate this binary mode of thinking. Of course, in some ways we are unique and special and in other ways we're not.

Story was about other potential "technological" species. You'll heave to deal with the fact that we are just not unique.
posted by anarch at 6:38 AM on May 22, 2016


The research question is "How many habitable zone planets are there?" Which is a perfectly reasonable scientific question.The rest is just acknowledging the fact that the reason a lot of the public cares is because the thought of life evolving elsewhere is really cool. I mean the whole field of astronomy and the field of particle physics and in fact many fields of science are funded because people really do care about knowing what the universe is like on a fundamental level, and not because they are going to lead to practical applications.

And even if "answering questions about the nature of the universe" falls outside of your arbitrarily defined goals for your "practicality" it is certainly at least as morally valuable as entertainment, which people are willing to spend billions and billions of dollars on each year. And strangely enough, I never hear these people with "practical" arguments make a peep about how bad it is that people spend a ton of money on that - because frivolities are apparently perfectly practical when someone's getting rich off of them instead just making enough live off of decently and do their research and share it freely with the world.
posted by Zalzidrax at 7:02 AM on May 22, 2016 [3 favorites]


Any scientist wanking about exo-biota while we're in the middle of a mass extinction event right here is definitely part of the problem.

Just to add my $0.02: the problem is not a lack of funding for research into clean energy alternatives, climate science, or the effects climate change is having right now. The problem is a lack of political will to confront the problem in any meaningful way. Whatever small amount of funding is being used to study exoplanets and exobiology is peanuts compared to what's being spent by ARPA-E, DOE, NSF, and NIH on climate change research and alternative energy research.

By your calculus, we should just shut down the Hubble, scrap the James Webb Telescope, and hell, what's the point of running the LHCs.

Is there any evidence government money was spent on this?

The article doesn't specify any funding source in the acknowledgements, unfortunately. The Martian tsunami work was funded by NASA.
posted by Existential Dread at 8:33 AM on May 22, 2016 [2 favorites]


It's fascinating to me how the emotions stirred up by this topic have such intensity. Throughout, I get the strong impression that a lot of people (1) don't have a clear idea of how scientists evaluate evidence and (2) how scientists make use of predictive models.

It is just as arrogant to assume that are we not. Pending the slightest evidence either way, a skeptical person can only say, "Unproven".

Although "proof" is an important aspect of mathematics, it is not how empirical science operates. We have not, for example, "proved" that either our models of general relativity or quantum mechanics are true (indeed, their mutual inconsistency suggests that both require modification). However, each provides a very good account of the available data.

Importantly, we do have evidence that pertains to the Drake equation (as well as my preferred version, the Seager equation). Prior to the hunt for exoplanets, we only had models of solar system formation to guess at how common planets of various types might be, and no one really knew what to expect. And sure enough, the earliest exoplanets that were discovered were weird (hot Jupiters and the like), not at all what people expected. But now, with several different techniques available, we have confirmed that not only are gas giants relatively common, but so are rocky planets. This can't be emphasized enough: In a small subregion of our local galaxy, rocky planets are abundant.

One of the most important assumptions that scientists make in cases like these is the Copernican principle: "Unless evidence suggests otherwise, assume that there is nothing special about our neighborhood." In light of star and planet formation, that means making the assumption that (1) galaxies like our own are fairly common, (2) stars like our own are not rare, and (3) that planetary systems like our own are not rare. We've know that the first two statements are reasonable for some time, and the bulk of the exoplanet data are consistent with the third statement.

Any scientist wanking about exo-biota while we're in the middle of a mass extinction event right here is definitely part of the problem.

It's sadly to be expected that this would devolve into an attack on basic research. There is a conception that scientists have super-heroic abilities to influence policy or to create wonder technologies that magically solve the collateral damage caused by our actual technologies. That's not how science works. Instead, the benefits of basic research have historically been indirect and surprising.

Astronomy has been involved in major scientific advances throughout history. It's called "Helium" (after the Greek god Helios) because it was discovered on the Sun using mass spectroscopy before it was isolated on Earth. The first demonstration that the speed of light is not instantaneous relies on measuring the orbital periods of the moons of Jupiter. The first definitive demonstration of general relativity's efficacy was predicting the procession of Mercury. The entire history of optics and photography is tied up with observing and recording the heavens, with major advances in CCD technology seeing their first applications in state-of-the-art telescopes and probes.

"So what will astronomy, cosmology, or exobiology do for me tomorrow?" asks the concerned taxpayer. Well, we don't know. If we knew, we would already be leveraging that knowledge. Maybe the sensors that will allow us to perform spectroscopy on the atmospheres of exoplanets will be crucial in studying our own atmosphere. Perhaps cracking the mystery of dark matter will open the door to new energy technologies. Perhaps the statistical challenges of processing the immense amounts of data astronomers find themselves working on will benefit the study of complex processes here on Earth.

At the same time, the point of basic research has never been to get you a better toaster. It would go counter to everything the history of science tells us to require that every scientist work on practical applications of current knowledge.

We require leadership from our scientists, not infantile speculation.

The speculations involved are the farthest thing from infantile, because they involve thinking seriously about topics like the relative abundance of elements in the universe, the gravitational dynamics of star and planet formation, and how to use our best telescopic and sensor technology to draw defensible conclusions from stars so distant we will never visit them ourselves. The best demonstration that these are not infantile speculations is that they're evidently a bit too sophisticated for some Mefites to appreciate.

Scientists should absolutely advocate for the policies that they think will bring about a better world. They should also absolutely seek to raise the level of scientific literacy of the general public. At the end of the day, "science" isn't going to solve the Earth's problems by itself. That will require politics that does not bury its head in the sand, but rather embraces the current state of scientific knowledge.
posted by belarius at 10:42 AM on May 22, 2016 [7 favorites]


Sorry, you are wrong.

Still, it's revealing when we arrive at the actual limits of human knowledge and folks still just bluffly assert the obvious truth of their opinions. I mean, we're literally talking here about what no one knows; you'd think a single smidge of epistemic humility might come in handy.
posted by RogerB at 11:02 AM on May 22, 2016 [6 favorites]


A slightly less pessimistic conclusion is that they are out there but have moved, leaving no forwarding address, ever since the first episodes of I Love Lucy reached their systems.
posted by y2karl at 11:30 AM on May 22, 2016


I blame William Frawley.
posted by y2karl at 11:33 AM on May 22, 2016


Story was about other potential "technological" species. You'll heave to deal with the fact that we are just not unique.

To be clear I'm not on the side of "cancel all exobiology research." For example, one thing I would totally fund and get excited about is a good Europa flyby that included ice fragment scooping and analysis for complex organics. I assume it's harder than I think since it hasn't been done, but still . . .

Regardless, when I see comments about "dealing with it" I have to say again that neither this or anything else has anything to do with offering evidence as to whether we are unique or not. It gives an estimate that to be unique in the history of the observable universe the odds of something "like" us evolving would have to be less than one in 2 x 10^22. The logical next question is "OK, that helps. What are the odds of something like us evolving?" Something no one has answered.

Instead there's a lot of "guess that clinches it." In point of fact we have neither evidence of intelligence off this planet nor a remotely empirical probabilistic model that suggests it is likely.
posted by mark k at 4:58 PM on May 22, 2016


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