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There's probably no industrial civilization on Kepler-186f

Yesterday, the environmentalists-Leninists were celebrating Vladimir Lenin's birthday once again – or the Earth Day, as these watermelons (green on the surface, red inside) like to call it in order to superficially look hip and modern. We would hear that there is no Planet B again, and so on.



Well, just a few days earlier, NASA's Kepler spacecraft announced the discovery of Kepler-186f which is pretty much nothing else than such Planet Earth B, the most Earth-like habitable-zone planet discovered so far. The alternative home is located 492 light years from us. At the current speed, Voyager spacecrafts would get there in (20,000 times 500) nine [thanks, Gene] million years (which is still short relatively to the lifetime of a star or a planet) but let's hope that in the future, we will have speedier spaceships (and ETs should have faster ones, too).

Their mother star, Kepler-186, is a main-sequence M1-type dwarf star whose radius as well as mass is 1/2 of the Sun's values but the luminosity is 1/25 of that of the Sun. The surface temperature, below 4,000 kelvins, is cooler than the Sun's temperature and all these numbers combine to the fact that at the orbital radius of 0.5 AU (4 light minutes), Kepler-186f is in the habitable zone. The temperature should allow liquid water which seems "enough" for those who believe that ETs are almost everywhere. The size of the planet exceeds the Earth just by 11% – so it's almost a twin sister.

Hontas Farmer thinks that the probability that an industrial civilization is thriving over there exceeds 50%. Not bad (he or she even claims to see some intelligent pattern in some electromagnetic noise). I suppose that the reasoning is that life has to exist there sometime in the future or the past and we might be more advanced or less advanced than them, with the chances for both options at 50%. Count me as a skeptic, my guess would be well below 1%.




We have clearly entered the era in which planets with physical characteristics extremely close to Earth's may be discovered pretty often. I have personally no doubt that the Earth's temperature plus minus 10% or so is just fine for life; the size of the Earth plus minus dozens of percent (and perhaps plus minus an order of magnitude) is OK for life, too. And I have no doubt that there are billions of planets just in the Milky Way that have these OK enough characteristics.

So why don't I believe that the smart ETs "probably" live on such a random planet?




My main reason is the simplest empirical one, one that Enrico Fermi pointed out. We haven't seen too many ETs or their signals here on Earth. If civilizations on habitable-zone planets routinely get to the point we are enjoying here and now, many of them should have sent at least some spacecrafts to all good enough planets that are at most 1,000 light years from them. Note that it's enough to reach the required industrial power – to send these thousands of spacecrafts – once. I don't need to assume that the civilizations survive for millions of years.

But we haven't been contacted by the "ambassador spacecraft" sent from Kepler-186f. We haven't been contacted by any "ambassador spacecraft" from the hundreds of other hypothetical planets where life should be much more advanced than ours and that are about as close as Kepler-186f. It seems bizarre to me. I think that a universe – or the Earth – drowning in the cosmic sea of hi-tech planets simply looks very different from ours.

The absence of non-bogus observations of ETs on Earth as of today seems to be the most important approximate measurement of the concentration of ETs that we seem to have, I think. It's a "negative" measurement. The most important "positive" piece of evidence indicating that ET life should be common is the fact that life began to evolve relatively quickly here on Earth. If some unlikely processes that may be fixed by repetition were needed during the creation of life, it would be far more likely that we find ourselves living on a planet whose star is going to die soon – a star that is as old as you can get. It doesn't seem to be the case.

However, the birth of life may have depended on some unlikely conditions that cannot be improved by waiting. The composition of chemicals – heavier elements, perhaps some special compounds, and possibly even some simpler or more complex organic molecules (or panspermia-like seeds distibuted by comets, asteroids, and dust, but only in some regions of the galaxy) – we have here on Earth may be rare. Some debris from several different types of dying stars could have met at a single point (on the Earth) and this just doesn't happen too often – and it will be happening even less frequently as the Universe keeps on expanding and diluting and stars keep on dying.

I have used this analogy before. The RNA/DNA/protein-like complex molecules that are needed for life may be as rare in the Milky Way as good string theory groups are rare on Earth. To establish a meaningful string theory group, you need to concentrate and accumulate the intellectual resources. In a similar way, certain – many – economic activities require some concentration of the capital. Because of the required concentration, these things just won't occur and can't occur everywhere.

The number of precise enough measurements of the number of ET civilizations – or the amount of robust enough evidence of any kind, including very indirect theoretical arguments – is extremely low which means that our prior beliefs – also known as prejudices – are obviously playing a very important role for our opinions about the number of advanced ET civilizations. Needless to say, I will instantly turn the coat once we start to watch our third alien TV channel if not earlier than that. ;-) But so far, the idea that we're very special – and perhaps the only ones in the Milky Way or perhaps the visible Universe (and there may even be some reasons why it is so), seems to admit a rather natural model that is compatible with all the evidence I am aware of.

Many people seem to be convinced about the idea that the "ETs are almost everywhere" because they think that they can disprove the idea that life is very rare. The main difference between them and myself is that I think that their disproof is just invalid. They believe that the "fast start of life" here on Earth immediately implies the "fast start on every good enough planet". But it's just not necessarily so – there may be differences in the "genetic setup" of the Earth, some very special detailed properties that planets either possess or (usually) not possess from the very beginning and the Earth's "genetic predispositions" simply could be extremely special and rare.

On the other hand, I feel that the advocates of "ET life everywhere" often hold beliefs that are in conflict with our observations of zero ET signals and ambassadors accessible to all of our tools of detection by 2014 AD. I think that their belief that an O(1) fraction of the hospitable-zone planets inevitably turns into the home of superadvanced civilizations predicts certain observations of ETs that our actual observations have refuted.

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reader CIPig said...

If there are ET's out there, they certainly don't seem to be in any rush to contact us. Of course we can imagine a galaxy wide alien civilizations which has quarantined us from contact for some reason or other, but if that's the case it might be really hard to learn about them anyway.


reader Luboš Motl said...

LOL, I think that this way of thinking reflects your hardcore communist thinking.


A galaxy-wide quarantine - are you joking? The perimeter of the Milky Way is 100,000 light years. Even if sending signals were enough to impose the really big (galactic) government's law about the quarantine, you would need 100,000 years for the message to get to the other place.


But before that, there would have to be lots of back-and-forth interactions (galaxy-wide wars) that the galaxy-wide leftists would have to win in order to be able to restrict the freedom of life forms across the Milky Way galaxy.


At any rate, you are surely showing what kind of a Stalnist ultraextremist you are. Not only you are not shocked by the attempts to restrict the freedom in the whole countries - including the U.S. You would prefer a 1984-like state in the whole Milky Way!


It is morally disgusting and, fortunately, de facto physically impossible due to the restrictions of relativity. Some civilizations might decided that we're too dirty to touch but it's very clear that others - an O(1) fraction - would think differently. You can't really ban civilizations/planets with certain types of political thinking that are routinely found on Earth. Like the desire to freely intreract. You might love to restrict the freedom of all remaining life forms on the Earth - or in the Milky Way - but you fortunately can't convert your pathological dreams into a reality. Relativity is against you, and so are the people who will kill you when you will try to circumvent relativity and introduce this galaxy-like tyranny. ;-)


reader Uncle Al said...

Kepler-186f needs military advisers. When the Pentagon finally gets there, they'd better speak Russian.


reader Maznak said...

Well I have one possible explanation for the lack of signals - maybe galaxywide electromagnetic broadcasting (like we are doing right now) is an obsolete technology for ETs more advanced than we are, one that is maybe used only in 200 Earth years window or so during the history of advanced civilization. It is for sure very wasteful, compared to for instance point - to - point laser-like signals. And who knows, maybe there are other fields that can be modulated and have some advantage over electromagnetism. This is of curse pure laymen´s speculation.


reader physicsnut said...

Fermi's "where are they" argument assumes that Life is easy on your average planet, and ETs can afford to send missionaries to convert us.


reader vixra said...

Nice article and I agree. My guess would be that to reach the stage of intelligent enough life for technology requires a series of lucky events including several mass extinction events that manage to get rid of just the right number of dead end species. Possibly a large moon is required for ocean currents/stability and other specific circumstances too. Probably the best we can hope for is microbial life on most "Earth-like" planets


reader etudiant said...

Is not the simplest explanation for the absence of aliens the demonstrable reality that industrial/scientific culture is very implausible?
Here on earth, life has been around for billions of years, Despite several resets via mass extinctions, industrial intelligence did not arise until recently, a few thousand years ago at most. So the odds favor life, but not industrial intelligence.


reader Gene Day said...

Your numbers are off a bit, Lubos. The Voyager spacecraft would take about 8.5 million years to reach Kepler-186f at their current speed even if traveling in the right direction.
Also, assumptions regarding the likelihood that an advanced civilization would even want to send spacecraft our way are suspect. Why would they? We may eventually engage in unmanned exploration of nearby planetary systems but what would be gained by initiating projects that could only pay off in hundreds to tens of thousands of generations?
I don’t doubt your conclusion in the least but another important factor is the probability of primitive life forms evolving into intelligent life forms. This may well be minuscule in the short time available thus far. We are very young, really.


reader Gene Day said...

Mass extinctions seem probable in any young planetary system that harbors life but why connect this with the evolution of intelligent life forms?


reader Gordon said...

There is a difference between "ET life everywhere" and "ET life". We haven't uncovered it because life evolved enough to signal us is too far away, and we are not evolved enough maybe to detect their signals anyway. The number of stars in the universe is staggering, and the projected number of them with planetary systems, similarly myriad. We are at the stage where we can create synthetic life--(Craig Venter) and origin of life studies are making progress (RNA first, metabolism first...).
There are about a million stars within a 1000 light year radius. Maybe there are no advanced intelligences in those million, but there are around 10exp 24 stars in just the observable universe, and most of those have some sort of planetary system. And that is JUST the observable universe.
(Just to get this out of the way, though, the Drake equation should be junked as a wild and crazy extrapolation belonging in Sci Am :))
Regarding life itself, I would bet on some primitive form on enceladus. Look at our own extremophiles, or at dinococcus radiodurans, a bacterium with hyperactive DNA repair mechanisms that can withstand the barrage of radiation in space.


reader Gordon said...

"industrial intelligence"--is that an oxymoron? :)


reader Gene Day said...

It does seem likely that primitive life is probable or even inevitable whenever conditions are right. I would not take your bet, Gordon.


reader CIPig said...

Probably, but there could have been Earthlike planets ever since metallicities got high enough - perhaps 10 billion years ago.


reader CIPig said...

What you call my "way of thinking" is actually a common science fiction trope, but the galaxy has existed for 130,000 light transit times - perhaps 100,000 them since the first Earthlike planet might have evolved, so if the first society to emerge colonized the galaxy, except for a few reservations, it has had lots of time to synchronize its watches.


I consider that scenario unlikely for a variety of reasons, but relativity might well be a minor one.


reader Gene Day said...

It’s not an oxymoron, Gordon, but an occupation. Spies are everywhere.


reader vixra said...

My natural expectation for a mass extinction would be that life is set back to an earlier primitive state, but on Earth each extinction has helped, e.g. by removing dinosaurs to allow mammals to develop. Perhaps that is what happens on all planets but that would bring us back to the Fermi paradox.


reader m said...

That is because God made the universe Lorentz-invariant: to protect his creation from a universal Marxism!

lOl ;)


reader ItFromBit said...

We are no closer to discerning the physical/chemical origin of life than we were 50 years ago when Watson Crick discerned the structure of DNA. The OOL is still a mystery so we cannot postulate how easy it may arise on other planets. I agree with Lubos, there is a good chance intelligent life may be unique to this planet and, in the extreme case, life itself may be unique to Earth.


reader Gordon said...

What you said in your first sentence is absolutely not true.


reader Jim Z said...

Life, auto-replicating chemistry, probably exists many, many places in the universe. So Darwinian evolution, auto-replication with defects, and selective advantage equally probably exists in many, many places in the universe.


In the history of life on this earth, the evolutionary advantage of intelligence has, so far, been an infinitesimally small fraction of the total history of life on this planet. (The odds of correct replication are great, the odds of viable incorrect replication are very, very small; so Archaic bacteria still exist. Will humans exist in a billion years in the future? In a million years?)


It is not obvious that intelligence is a durable evolutionary advantage. Nor is it obvious that the duration could be greater in the other location in the universe.


reader Jim Z said...

I agree with Gordon. The "physical/chemical" origin of an auto-catalyzing chemistry (auto replicating) is well understood. It is the inevitable consequence of chemistry (amino acids in water).


reader Jim Z said...

(Idealized...) Take a test tube of the primordial soup. Wait a while. Put a drop of that aged soup into a test tube of fresh primordial soup. Wait a while. Put a drop of that resultant into a tube of fresh soup. (Wash. Rinse. Repeat... a million times...)


Complexity will occur. It has, even in laboratory timescale.


reader Jim Z said...

Lubos, you said;

"If civilizations on habitable-zone planets routinely get to the point we are enjoying here and now, many of them should have sent at least some spacecrafts to all good enough planets that are at most 1,000 light years from them. Note that it's enough to reach the required industrial power – to send these thousands of spacecrafts – once. I don't need to assume that the civilizations survive for millions of years."



How many space craft have we earthlings sent out to other planets? In the near immediate future of humans, the next hundred years, how many more do you think that we will sent? Londinistan, in North Pakistan probably won't launch any. Greater Chechnya will probably be looking down towards the earth, not outwards.


So, will there be a thousand outward bound spacecraft launched, before our demise?


So when we speculate about 'intelligent extra terrestrial life', in other places in the universe, why don't we ever posit that is only a super developed version of Waziristan? Instead, we always imagine super evolved life without tribalism.


reader Florin Moldoveanu said...

Wow, what an interesting read after the dust had finally settled on PBR. In the beginning I was just as confused as everyone else on this and with hindsight re-reading this and other points of views (Matt, Scott, Wallace) along with reader comments made for a nice and entertaining read. This one is for the history books. Plenty of early analysis errors to go around for everyone, myself included. The paper itself is poorly written because it assumes familiarity with not universally accepted points of view and does not effectively get the point across. On the claim itself, what is the long term impact of the result? Gone is the early excitement that the wavefunction cannot be probabilistic. No impact on the Bayesian approach either and "psi-epistemists" remained unmoved in their beliefs. The situation is effectively back to where it was before PBR.


reader Gordon said...

Then there are always silicon life forms (or gallium arsenide ones with optical enhancement). These are the singularity that Kurzweil keeps talking about. Take a self-replicating automaton (courtesy von Neumann) add some basic evolutionary programming that after startup allows it to learn, mutate,incorporate redundancy,write its own software and replicate using the next few generations of 3d printers. Kurzwell just has his time frame wrong. To me, it seems inevitable eventually, if we humans can keep from going extinct for a few hundred more years.


reader Gordon said...

Seti simply needs the NSA to hack the ET broadcasts. They listen to everything else :)


reader Luboš Motl said...

You're right, it's 8.6 million years

http://www.wolframalpha.com/input/?i=492+light+years+divided+by+the+speed+of+Voyager



I should have used this calculator for the division, too, it's safer. ;-)


If we could try to colonize known habitable planets, I would surely want to start the process. It gives some stability to the human existence etc. This is not about the payoff to the mother planet's civilization at all.


On the other hand, even those 9 million years are long enough for a mission (perhaps an unmanned ET mission) to come here and return back, too.


Of course, the evolution to intelligent life forms could be unlikely. It took some billions of years here now. But it's plausible that at an O(1) fraction of the planets with a primitive life, it eventually works and it is faster than here so it shouldn't be a problem.


reader Luboš Motl said...

LOL, Gordon, have you adopted the Luddite viewpoint of environmentalists such as Alexander Ač and James Cameron that people must be extremely stupid and unintelligent to pursue something as dangerous as the *industry*? ;-)


reader Luboš Motl said...

Dear Dr Moldoveanu, thanks for a flattering and refreshingly sensible voice from an insider. So I guess that now, 2.5 years later, the feelings of PBR's colleagues have converged closer to my feelings a day after I read PBR. Your description is exactly correct: PBR assume a certain very special basic framework how QM "should" work that other people do not accept - and I, for one, am absolutely sure that these basic assumptions are incorrect.


PBR was just another fad in the "revolutionization of foundations of QM" and these fads are getting increasingly shallow and shorter-lived, I think. It's only quantum mechanics with its clear rules to calculate the probabilities - that must be interpreted as a matter of subjective expectations about the results of experiments - that will survive in the long run.


reader Jim Z said...

Gordon,


The silicon or gallium doesn't have a 'natural', or convenient solvent. Not like common water.


The chemical auto-replication of life isn't like von Neumann; it's dumb. It has no design. Evolution is a 'blind' process. It's an inevitable, blind, process.


reader Jim Z said...

And, without regard to what the 'chemical species' of an ET life form are, how can we think that any one powerful ET life species, dominant of it's planet's life forms, how can we think that it can evolve to it's dominance without it's developing some sort of tyrannical defect. A tyrannical tendency that prevents it from 'looking outward'?


There is no 'intelligent design'. Evolution can only proceed by Mendelian heritance and Darwinian selection. So as intelligent species, and sub-species, evolve there are competing adaptive advantages. So what adaptive behavior will prevail, in the ET society? (There will be competing species and cultures; there can not be evolution, and advancement, without them). Our planet's dominant human society is one of diversity of purpose, and dysfunctional operation (i.e. climate science instead of space exploration). For a 'unity of purpose' culture, one that can sent out a thousand 'announcement' spacecraft to the 1000 light year's near 'Goldilocks' planets, it would need to be a dictatorial culture. It will send the expensive spacecraft out to nothing, instead of feeding hapless members of its' society? It has no hapless members of its' society? (It euthanized them?) It is a Utopian society, and it can splurge on anything, that each member desires?


The totalitarian culture looks outward, to ETs, for what? More authority?


The 'it can afford anything' society, Does it look for anything, at all?


(Our approximately competitive society, it weighs the value of sending a thousand spacecraft out to the stars, and its' component members do *nothing*.)(And it's hard to see when that will ever change...)


reader Luboš Motl said...

If someone is following this: Eight months later, i.e. today, these CMS multilepton OSSF1 excesses have finally made it to a preprint. Numbers unchanged:

http://arxiv.org/abs/1404.5801

I think that 8 months is very slow. This delay increases the odds that new physics may still be found in the 2012 run data.


reader Casper said...

We might surmise that the problem for Fermi's theory is that ET wasn't educated in the EU and therefore doesn't think like him in the slightest. Therefore its called Fermi's Fallacy. In fact the extra-terrestrials don't want to visit Earth really because if they did then all the Earth physicists heads would implode. Obviously they are concerned that Earth civilization would not survive this catastrophe.


reader strictly speaking... said...

...But you don't need faster than light speed travel to colonize the galaxy. You simply need to be able to travel from one star to the next and build an industrial civilization there, or anything equivalent to it, capable of building interstellar spaceships.

If the "build an industrial civilization" part takes less than a millenia or so you could colonize the galaxy in 50 million years or so, and once the process has been started it'd be unlikely to stop.


reader Florin Moldoveanu said...

I am not an "insider" and I have very little influence within the community. I am merely stating the historical facts as I have seen them unfold.


reader Anonymous said...

As in Carl Sagan's romance "Contact" ... they are already trying to contact us, but we are simply not bright enough to detect them. Most likely, they are using "dark signals" which do not get screened by interstellar gas. In fact, it would be much more efficient than using photons, right ? Let's see in near future.


reader stevenjohnson2 said...

Science news recently noted that the ninth drop of pitch fell. Is it really reasonable to assume that manufactured devices has enough stability to remain functional? Geology has demonstrated that rocks bend. Will structural members really retain their shape? Radioactive dating has to be careful to allow for impurities escaping or penetrating crystals. Will dopants really keep their proper levels in the right places? Superconductivity can arise at low temperatures. Do we know all the possible quantum effects that might appear on a macro scale at interstellar temperatures?



If a probe were to get to another system, what would it do? Perhaps an alien probe landed on Sedna 5 000 years ago.
Or perhaps twenty thousand years ago an alien probe was effectively incinerated in the Io flux tube. Or perhaps alien von Neumann machines are gathering materials on the surface of Venus, and in just another millennium another armada of interstellar probes will erupt from the Cytherian atmosphere?


I suspect there's a good chance if you came up with the equivalent of a Drake equation for the Fermi probability of alien visitation, you would find that it has just about as many unknowns.


reader Gordon said...

lol, I guess I wasn't specific enough for your brain to intuit what I thought was obvious---"silicon life" originates when intelligent biological life builds them. They don't originate "chemically"---thought that was blindingly obvious. Also the von Neumann replication of course is not "chemical"--never said it was--just mentioned von Neumann because he and Turing were first to implement the idea mathematically--once again---blindingly obvious unless you take everything literally.


reader Gene Day said...

“-stability to human existence-”?
What do you mean by that, Lubos.
I would question that in several ways but, primarily, I don’t envision any threat that would be lessened by our colonizing other planets.
Colonization has always happened in the hope of financial gain or to improve one’s life, which actually means the same thing. Even exploration has always had the same motivation. The moon landing was merely a political stunt; unmanned exploration would have been far more cost effective.
Anyway, life is basically unstable as any elderly person knows very well.


reader Luboš Motl said...

What I mean is that if someone denotates the Earth or brings some deadly infection killing mankind on this planet, the mankind at other places could still survive.


More places like that surely increases the survival chance of the human race, doesn't it?


reader Gene Day said...

Having worked my entire career in industry, Lubos, I have found leaders in industry to be at least as smart as our top academic people and a lot more street savvy. Perhaps Gordon was attempting humor. Of course my attempt (see below) was even more pathetic.


reader Gordon said...

No, not at all...just a cheap joke. I do want to protect the environment, but am at the other outlier Gaussian tale than the Luddites. I want the best of both worlds.


reader Gordon said...

yes, Gene--humor---but I improvise on the fly before higher centre neurons have had a chance to edit :)
The results can sometimes be the opposite of what my frontal lobes believe :)


reader Eugene S said...

Dear Luboš,

How do you read this out loud:


I think that their belief that an O(1) fraction of the hospitable-zone planets etc.


Short form / long form / "for dummies"?

I keep seeing you use this but I can't find an immediate answer on Wikipedia:

https://en.wikipedia.org/wiki/O%281%29#Orders_of_common_functions
"Big O notation has two main areas of application. In mathematics, it is commonly used to describe how closely a finite series approximates a given function, especially in the case of a truncated Taylor series or asymptotic expansion."

https://en.wikipedia.org/wiki/Orthogonal_group#Low-dimensional_topology
Here, it says, "O(1) = {±1}, a two-point discrete space".

Does either of these entries correspond to your intended meaning?


reader Luboš Motl said...

Dear Eugene, O(1) is pronounced "oh one". ;-) No, it doesn't mean the group you found. It means a number of the same order as 1, i.e. 100%, so it may be 30% or 50% but not 0.0001% or 50000%. ;-)


reader David Nataf said...

Do you see human beings sending out people to live on alpha centauri never mind Kepler 186f? We can hardly colonise the moon or even antarctica.


reader Tom Trevor said...

I think that intelligent life is rare, because it appear that any life at all is rare even in our own solar system. We have found no proof at all that even a microbe of life exists outside of the earth. It strikes me that if life was as common as many people think it is, we would have found at least one extraterrestrial microbe. Sure the other planets and moons in the solar system are less hospitable to life, than Earth is, but they don't appear to be totally incapable of ever having had life on them, and they should have been hit by about as many comets as earth has been hit by. So, if life is common, and as many people suggest, likely exists on comets, I would think we would have found evidence of at least a microbe on The Moon, Mars, Europa, or Io by now.


reader Kris said...

You're argument to why there would be no life is unjustifiable. Even one bacterium is considered life.
Just because this planet does not have black eyed, big headed little green men coming to greet us is irrelevant to the possibility of life claim.
Is there a possibility? Yes. If there is water on the planet there is a possibility that there would be some type of bacterium at the least given the right atmosphere.
As pointed out on the NASA article, atmosphere is key.
Also, we haven't reached an intelligence level that would sufficiently give us an up close inspection of this planet and even signal pick up has a limit. What makes you think other life, hypothetically speaking that "life" would be similar to that of a "human", is capable of reaching us? We can't reach them at this stage in time.


reader anony said...

Sure, whales and dolphins are intelligent, never taught in a school of higher education, but we just finally closed loopholes that allowed people to use them for food. The fact that we haven't been eaten by hyperintelligent beings is by far the best evidence they don't exist.


reader Devdan said...

What do you think about ET's being smart and all, living here in this planet but not making it too obvious? Having troubles with their planet called Lorien?


reader Mr_Speck said...

Guess its not called Fermis paradox for nothing.
And my second guess is that the situation will only evolve to being still more paradoxical...


reader Luboš Motl said...

Nice but there are no real paradoxes in Nature. A "paradox" is something that only looks contradictory - because one is making some wrong assumption(s).


reader Smoking Frog said...

Lubos - I once argued with a friend who thought it was virtually unavoidable that advanced aliens exist, and exist on a "decent" number of planets, (say) hundreds or thousands of planets per galaxy. My argument was something like yours: What if we're a fluke? What if (I invented) we're analogous to the only rock in the world that looks just like JFK?

He said, "Do you know of a fluke that's of any significance for science?" I admitted that I didn't. He said, "So you're asking what if intelligence is of no significance for science. How could that be?" I didn't have a good answer, but I pointed out that he was hostile to criticisms of Darwinism, even though Darwinists claim that evolution has no built-in direction. He took the point, but we agreed that it was weak.

How would you answer him?


reader Luboš Motl said...

Dear Smoking Frog, quite generally, if an explanation/theory requires some unlikely event or choice - a fluke - I view it as unlikely. The more unlikely and special initial conditions it requires, the smaller prior probability such an explanation should get.


So I don't like general "we are fluke" explanations, either.


But there is a subtlety here. What we're really observing is that there is at least one living planet in the Universe. We're not really observing that there is life on a randomly selected planet. Ours isn't a randomly selected planet. It's selected by our being here. So the explanation of us using a fluke only assumes that "there is at least one planet with such a fluke somewhere" which isn't unlikely, and therefore the "fluke requiring" explanation shouldn't be disfavored for the reasons mentioned at the beginning.


I acknowledge that the previous paragraph includes me among (at least mild) anthropic believers but I don't really agree with the anthropic explanation of anything else - any details of our existence.


reader Hontas Farmer said...

I never said it was "probable" Even in my title I said it was a 50/50 shot given both the Kepler data and the data from SETI live which looked at the planet with the Allen Telescope Array (All due respect to Dr. Shostak clearly not everyone at SETI thinks the ATA is a pointless device). To say anything one way or the other would require more and better observations than we can make right now. I simply think it is a 50/50 chance and worth further investigation.. Got it? Good. :)