Inevitability of Science, and the Rise of Science in the West v. China

A friend posed a question, which I attempt to give my answer to.

Q: In Paul Davies's Eerie Silence, there's a section titled 'Is Science Inevitable?' In the paragraph beginning 'Suppose an asteroid had hit Paris ... It goes on to say: In medieval China, no clear distinction was drawn between moral laws and laws of nature. Do you think that is still the case? After 65 years of communist rule?

A: There are really two questions here. First, whether the rise of science is inevitable given the rise of a toolmaking intelligent species, and second whether Chinese society today reflects the same sort of philosophical attitude towards epistemology as it did in the Middle Ages. (To paraphrase). Never one to shy away from discussing things I only slightly understand, I will attempt some comments.

If I took his point, what Davies was saying is that science; or, more specifically, the scientific method, arose because of a contingent series of historical accidents, beginning with ancient Greek logic, followed by late Medieval philosophical developments which themselves were dependent on certain intellectual currents in the Islamic world, followed by a new age of exploration and technological development in the Renaissance. Take away any of these elements— q.e.d., no science, and presumably much slower or non-existent progress towards systematic procedures for uncovering the actual nature of physical reality, slower technological growth, etc. Counter-example being China, which in 1000 AD was far ahead of the West in every way, including technology and what you might call practical engineering and descriptive science, but which had not developed a procedural system or methodology for investigating scientific truth. And as a result, in a few short centuries it fell hopelessly behind the west in science and technology.

Davies apparently infers (from what, I’m not entirely sure) that the Medieval Chinese drew “no clear distinction… between moral laws and laws of nature.”  To the extent that statement is true, though, I’m not sure that the development or failure to develop scientific methodology is explained by it, or that either is necessarily dependent on the other. (Although it would seem likely that the state of philosophical development could significantly affect the timing of scientific advances). There are those (such as Thomas Nagel) who even today reject the modern secular notion that values are purely relative, so the idea that a civilization could not have a systematic set of cultural norms that espoused “moral laws” as objectively true, and at the same time develop a truly scientific methodology, does not seem obvious or even plausible to me.

For example, the Ming Emperors Hong Xi (r. 1424-1425) and his son Xuan De stopped the voyages of exploration of the great admiral Zheng De, who had explored the Indian ocean and rounded the tip of Africa in huge trading fleets during the late 14th and early 15th centuries, well before Columbus. And, interestingly, their reasons for doing so were apparently moral, i.e., that it was unfit to require crippling tribute from foreigners. (Anti-Imperialism in 15th century Chinese political philosophy!). (See http://en.wikipedia.org/wiki/Zheng_he). But I have to say, can there be any real doubt that had history not caught up with China, i.e., had the Europeans not beat them to the punch, they would have, in time, resumed these voyages of exploration? And the Chinese may have had more intellectual baggage surrounding the nature of truth, and so on, but Buddhist philosophy contains the principle of determination of truth through direct investigation, which could quite easily have led in time to something hardly distinguishable from the scientific method. I actually think the parallels between more or less isolated Chinese civilization and the civilization of the West (including Islam) up to around this time more plausibly leads to the inference that something like science, and certainly engineering and technological development, were very much inevitable developments.

Looking at it from the broader context (the assessment of the likelihood that extraterrestrial intelligence, if you posit its existence, would necessarily develop advanced science and technology),  what Davies is saying seems to me to be a variation on his Anti-Copernican theme. Namely, that maybe we here on Earth, both in terms of the serendipity of the origin of life, the suitability over deep time of our home planet for life to thrive and for complex, and ultimately intelligent, life to arise, maybe actually ARE kind of special, after all. That this series of events is not only contingent but maybe rather spectacularly unlikely, in the greater universe. Add some apparently rather unlikely contingencies for the development of advanced science and technology, even given a toolmaking intelligent species, and you get an argument for extreme rarity of technological civilizations, which is pretty much exactly where Davies seems to be going with this.

To my mind, there’s  a lot of sort of anti-teleology going on here. Or what you might think of as negative special pleading. Sure, there are a lot of things that have to have gone right to get us to the point, say 10,000 years ago, where civilization was about to arise on Earth. There are all kinds of arguments for why that is terribly unlikely to happen elsewhere in the universe, to which those who advocate that extraterrestrial intelligence likely is out there counter, yes, but there are so many, many stars and worlds, surely some of them must have had their own favorable contingencies (and not necessarily the same ones), etc. etc.

But looking only at the question of whether science was purely dependent on the specific contingencies of European civilization ca. 1500, I have to say I don’t buy it.

As for the second question here, which is whether there is some kind of continuity with the what I’m referring to the epistemological cultural attitudes of Chinese civilization vis-à-vis the West, and whether it continues today in Modern China, well. That’s inscrutable. No, seriously, I think of the Chinese as being pre-disposed to longer term thinking than Westerners, by and large (a stereotype, of course, but like many stereotypes, with a grain of truth). And the same goes for their history. As a nation on the edge of the World’s great continent, subject to repeated barbarian invasion, occupation, and eventual assimilation of the barbarians to the (to them) obviously superior Chinese civilization, Chinese history almost looks like a series of pendulum swings between stable empire (Heaven’s favor) and the chaos of various interregnums, (Heaven’s disfavor), when thugs and brigands rule and Confucian morality is trampled upon. Not hard to see the period from 1930 to the present (and beyond?) as such a “warring states” period. I don’t doubt that many in China, even though it’s not yet safe to say it, would argue that Deng Xiao Ping was a restoration emperor, who brought back a civil order, but I suspect others would say that the deeply corrupt and nepotistic Communist Party, the unrest of the people, and the environmental instability and unsustainable growth of the modern Chinese society all are indicators that the period of Chaos isn’t over yet. (It is pretty clear that specifically Maoist/Communist rule came to an end sometime before 1990, but the regime didn't change. An entire historical treatise on how Marxism, and even Leninism, were subverted to become mere ideological pretexts for totalitarian regimes, but I've already ventured far enough afield. It is notable, though, that the Chinese regime has pretty undeniably retreated somewhat from the kind of totalitarianism that held sway under the worst days of Mao).

All of which is to say that moral truth may not be a major issue for Chinese leaders today. They have embraced Western technology, and its science, and perhaps even more significantly the currently fashionable Western moral relativism. China has produced, for example, some fine physicists and other scientific leaders, and their society has seemingly embraced amoral market capitalism even more enthusiastically than is the case in the countries of the birth of that concept. But whether, in the long run, a purely Chinese traditional philosophical system will re-emerge and modify their attitude towards science, it’s hard to say. I like to think that what will emerge, perhaps during this century, is a synthesis of western and traditional eastern attitudes towards what truth is, and how it is arrived at, which may allow for a syncretistic and secularized acceptance of certain key moral values as objectively necessary and true. Perhaps then, the favor of Heaven may come to bless our whole world, and the people and the rulers will live in harmony; the Confucian ideal. (Don’t hold your breath, but we have to have something to work towards).

This has been a rambling and verbose answer to these questions, but there you have it.

Blue Sky: signature of living worlds

An alien being with vision approximately in the same wavelength range as ours could immediately infer from seeing the Earth's sky that the Earth is a living world.
 

The blue hue we see is caused by Rayleigh scattering (a quantum effect) that preferentially scatters shorter wavelength light, combined with two factors, one of which is peculiar to humans and the other of which is the key to the statement above. Humans have a deficiency of violet sensitive photoreceptors, which makes us see violet fields as bluer (or you could say redder, anyway less violet) than they really are. So the sky is "really" a bit more violet than we see it.

But just as importantly, molecular oxygen selectively absorbs light in the near violet, so that it's not just that the sky appears more blue, it actually is more blue. If it were pure nitrogen, it would be distinctly blue-violet in color. And so, a being from another living world who found himself magically transported to the surface of the Earth could infer at once that he might not be home, but he was standing on the surface of a living world whose atmosphere contained a substantial percentage of molecular oxygen.

Ain't the universe remarkable?

More Thomas Nagel. . .

So Nagel says of a predisposition of the cosmos to the existence of life, consciousness and value (let's say harm/benefit to such beings):

«In the present intellectual climate such a possibility is unlikely to be taken seriously, but . . . no viable account, even a purely speculative one, seems to be available of how a system as staggeringly functionally complex and information-rich as a self-reproducing cell, controlled by DNA, RNA or some predecessor, could have arisen by chemical evolution alone from a dead environment. Recognition of the problem is not limited to defenders of "intelligent design." Although scientists continue to seek a purely chemical explanation for the origin of life, there are also card-carrying scientific naturalists like Francis Crick who say it is almost a miracle. Crick is led by his reflection on the probabilities to the hypothesis of "directed panspermia"-- that Earth was seeded with unicellular life sent from an advanced civilization elsewhere in our galaxy where life had evolved earlier. This depends on the supposition that there were other planets or other stars whose physical environment made the accidental formation of life less unlikely. But Crick acknowledges that there is no basis for confidence about any of these likelihoods. 

​   Some form of teleology. . . would be an alternative to a miracle -- either in the sense of a wildly improbable fluke or in the sense of a divine intervention in the natural order. The tendency for life to form may be a basic feature of the natural order, not explained by the nonteleological laws of physics and chemistry. »

​ He might as well have mentioned Jacques Monod in place of Francis Crick. Anyway, as a dyed in the wool secular humanist/Buddhist, I nonetheless find these ideas strangely compelling. ​

Machine Civilization ?

Paul Davies and Seth Shostak, two SETI pundits who have rather divergent views on several of the relevant issues, both believe that advanced alien civilizations, if and when we discover evidence of their existence, are likely to be “post-biological,” i.e., some form of advanced computers.

While I give both of these gentlemen considerable credit for imaginativeness and for considering carefully the implications of a lot of the assumptions that are usually made about the likelihood of alien life and intelligence, here is an area where I think they are both making unfounded assumptions.

The fact is that there is no evidence, at all, that artificial computers have any awareness or consciousness. I question whether evolution or intentional development can or will occur among “artificial minds,” when there is no indication that their functioning is anything more than rapid and complex calculation, lacking any sort of subjective experiential nature.

I suppose it’s conceivable that artificial machines could reproduce themselves and mutate and evolve through natural selection, this isn’t something we’ve ever seen, so I would like to see some evidence that it’s likely to happen before we start assuming that it will happen. And, along the lines of the Fermi Paradox as reasons for concluding that intelligent life is probably not all that common in the universe, I think the lack of intelligent machines swarming all over and cluttering the place up (which they would if they were common and had existed for an arbitrarily long time, given the immense age of the universe and the fact that it has existed pretty much as it is now for a significant fraction of that time), is pretty strong evidence that such machine civilizations are not common in the universe either.

More on Fermi Paradox: Implications of Space Arks

Paul Davies, in his book from a few years ago, Eerie Silence, touches on a wrinkle in the famous Fermi Paradox (see this), the implications of which I hadn’t really fully thought of  before.

Let’s take as a given that in the 12, —or more conservatively let’s say 6—  billion years or so that the Galaxy has been more or less like it is now (since stars have to have gone through a generation or two to produce the metal materials necessary for life)… there could have arisen some reasonable number of advanced technological civilizations. By reasonable, I mean, let’s say 50 or more, in that time, which most enthusiasts for the whole concept of extraterrestrial life would consider quite conservative, in 6 billion years of time. In a Galaxy now said to have as many as 400 billion stars, that in any case isn’t too big a stretch, assuming you accept the argument that it’s at least plausible that life arises relatively readily in suitable environments spontaneously (an unproven assumption, but one that can reasonably be made at least for the sake of argument). (It’s also implicit that there is some reasonable probability that a scientific/technological/intelligent species has at least some chance to arise; another purely speculative assumption, but again, for the sake of argument).

Now, set aside the Von Neumann machine argument, as speculative (which it is; see the link above; it’s not really a given that any civilization would try this, or that it would actually prove feasible). And set aside the possibility of faster than light travel (for pretty definitive reasons, see this). But add this posit: at least some percentage of these technological civilizations will during their history overcome natural selection pressure and collective stupidity well enough to survive for several million years. OK, that’s a lot of “let’s assumes,” but actually, that’s my point. If you make all these assumptions and infer a likely outcome, which in fact does not conform to what we see, it’s at least an indication that some of these assumptions need to be questioned.

So, what would likely happen if all these assumptions were correct? Obviously we don’t really know. It’s possible that there could be some number of quiescent, own-business minding technological civilizations co-existing with our threshold version right now, in various places in the Galaxy, and we just haven’t seen evidence of their existence so far. (Or evidence of the existence of any particularly wild and crazy versions that might even be detectable across intergalactic distances— in other galaxies). Possible.

But consider this. What if, as seems not totally unlikely, some fraction of these technological societies were naturally expansive? Prone to colonization of unoccupied real estate? This is  clearly a feature of Homo sapiens, and there’s at least some reason to believe it’s hard-wired into a lot of the genetic code of terrestrial life: the tendency to expand to occupy available space.

Now let’s engage in a little reasonable extrapolation of technology. Several engineering minded folks, such as Gerard O’Neill, Freeman Dyson, and sci-fi writers from Larry Niven to Iain Banks, have discussed the feasibility of constructing artificial habitats in space. It seems pretty clear that there is nothing preventing this technology from being realized other than inertia. It will likely come to pass right here in our Solar System, unless we, as a civilization, expire from terminal stupidity (an outcome perhaps more probable than we like to think, but one that’s already accounted for in our assumptions above with respect to the hypothetical other civilizations under consideration).

So, here’s the thing. I submit that it is no great stretch to go from huge artificial habitats in space, to something like Arthur C. Clarke’s idea for a traveling space colony, which he called Rama in his sci-fi novel. A sufficiently advanced civilization could quite plausibly build some such slow-moving space arks, and using space telescopes (also feasible, including possibly the natural gravitational lens telescopes discussed here), could identify all the relatively nearby habitable planets. Over long periods of time, these hypothetical advanced civilizations could indeed colonize other worlds. This would not be space travel. No to and fro required. It would be one-way colonization, but over time, it would mean that a civilization originating in one star system would come to occupy a region of space. (This could well be our very long term future).

Following from that, you arrive at the inference that there would be an expansion rate, of some value, and that the volume of space encompassed by a civilization would increase. There would also be implications for the survival of the living beings involved. Assuming that they continue to co-exist as living things in conjunction with whatever machines they’ve built, their survival would presumably be enhanced by occupying a lot of different abodes. Think of a plant or animal species that occupies all the forests of a continent as opposed to one little neck of woods on an isolated island or peninsula. Its survival potential is enhanced, clearly.

And following from that, you arrive at the assumption that in some fraction of the entire period under consideration, if unchecked, one or more of these civilizations would come to occupy planetary systems throughout the entire Galaxy. The Galaxy is huge, but finite. And even if you conservatively estimate that the time for a civilization to expand by one new system, which might average a distance of say 10 light years, is 100,000 years, or some similar number, you still find that in time shorter than the available billions of years, the expansion fills all the available space in the Galaxy. Even if you assume civilizations are finite in lifetime, and eventually fade away, to be replaced by others, there’s still a definite tendency, if these assumptions are all correct, for space to be not a vast wasteland of unexplored territory, but a finite resource, any particular locale within which is likely to have been exploited at some point in this long history.

What we find on Earth, I submit, is inconsistent with this. We don’t find any plausible evidence that the Earth has been colonized, or that alien spacecraft and space structures have ever existed in our star’s system. So, pretty clearly, something is wrong with some of these assumptions. Somewhere in there, the logical chain of connections breaks: either life is actually not too likely to arise in the first place, intelligent/technological/expansive societies are not likely to arise or not likely to survive long enough to actually occupy an expanding section of the Galaxy.

Or perhaps, civilizations quickly realize that natural planets aren’t really worth the effort. There’s plenty of matter and energy in the universe, why bother with the trouble, vast time, and expense, of interstellar colonization, when you can just build artificial environments (Ringworlds, Dyson Spheres, Banks Orbitals), and stay put? Yet that begs the question, all of them? Even if some high percentage of technological civilizations avoids expanding colonization schemes, wouldn't some of them do this? Yet the negative evidence, at minimum, sets constraints on this, to the effect that there has never been really widespread and long lasting space colonization going on. And if that's true for our Galaxy, it's likely universally true as well, which definitely has some implications for the assumptions we make about the prevalence of tehcnological civilizations such as what we envision for our own future. Perhaps, as I've mused elsewhere, we are in fact early pioneers, and it will be we, not some past technology creating beings, who will be first to spread intelligent life far and wide in the universe. Or at least this neck of the woods.

In any case, this is one more aspect of the Fermi Paradox: Where Are They? Because if any appreciable number of advanced civilizations had ever existed long enough to undertake major efforts at interstellar colonization, the universe and our Galaxy are old enough that it’s quite likely that process would have already reached where we are, and we would know about it.

Gravitational Lens Telescopes

In reading Lee Billings's Five Billion Years of Solitude (which as a book has its strengths and weaknesses), I came across a really intriguing idea which apparently isn't at all new, but had escaped my attention to now. I knew that in 1919 E. R. Eddington had demonstrated the truth of Einstein's 1916 General Relativity Theory by measuring the displacement of star positions near the limb of the Sun due to gravitational refraction of the light.

There's that word: refraction. In the late 70s, several independent theorists conceived the idea that if the sun, or for that matter any star, is bending light, systematically and achromatically (without regard to the wavelength), then the light from any given direction should come to a focus at a point in the opposite direction from whatever is being observed. In other words, the sun's gravity could act in effect as a telescope with an enormous tube length (focal distance) and an aperture effectively equal to the Sun's 1.4 million kilometer diameter.

Turns out the focal length is about 550 AU (more, actually, due to electromagnetic effects; effectively it's about 150 billion kilometers). That's a long, long way... further than Voyager has yet reached. So we're talking about at least one order of magnitude leap in space technology before this could be attempted. But in principle, if you wanted to look at Alpha Centauri, for example, you could send a Hubble Space Telescope to the point opposite that star in the celestial sphere and 150 billion km. from the Sun. Then block out the disk of the sun and look at just the ring of space just beyond the sun's disk (filtering out coronal effects and flares; but that's easy enough). What would you get? A telescope that could image coastlines, mountains, rivers... cities. Really. This isn't science fiction. Out to a distance of at least tens of light years it would be just absolutely amazing; although of course you have to go to the right place to see any particular thing. But think of it. The focal-sphere around any star is automatically a fantastic telescope that can view the entire universe at magnifications we can only dream of using artificial instruments.

It's breathtaking. And we will do it, I believe. And even more strongly I believe that others, in the past, at other places, and in the future as well, have done it and will do it. Who knows? One of your ancient astronauts might have espied the Earth in just this way (although there's unfortunately no evidence for that as yet).

Opposing TRULY AWFUL Iran sanctions resolution

I just sent the following message to every one of the Democrats who have indicated support for the horrible Kirk Menendez resolution to hamstring the president's efforts to reach a diplomatic solution to the Iran nuclear issue.

«I am terribly disappointed that any Democrat would seek to undermine the president’s foreign policy, which is designed to achieve a diplomatic solution to the Iran nuclear problem. I urge you withdraw support for this terrible bill, which would potentially draw America into yet another Mideast war that the American people overwhelmingly oppose. »

Here's the list. Go to http://www.senate.gov/general/contact_information/senators_cfm.cfm to get contact. Note: Blumenthal won't take messages from out of state, so enter a Connecticut address or mail a letter to his office.

Begich (Alaska), Michael Bennet (CO), Richard Blumenthal (Conn.), Cory Booker (N.J), Ben Cardin (Md.), Bob Casey Jr. (Pa.), Chris Coons (Del.), Joe Donnelly (Ind.) Kirsten Gillibrand (N.Y.), Kay Hagan (N.C.), Mary Landrieu (La.), Joe Manchin (W.Va.), Bob Menendez (N.J.), Mark Pryor (Ark.),Charles Schumer (N.Y.), or Mark Warner (Va.)

Senate Dems undercutting president's diplomatic efforts on Iran

I worry seriously about the AIPAC (Foreign government lobby) sponsored effort, with 16 Democratic senatorial co-sponsors, to undermine the president's diplomatic efforts to resolve the nuclear issue with Iran. The actual Menendez resolution is just horrible: committing the US to war all but automatically based on the paranoia of a foreign state (Israel)!!? I am appalled and will actively oppose the re-election of any Democrat who votes for this travesty. Even if Obama vetoes it, there's actually a pretty good chance of override, all because politicians are afraid to oppose the Israel lobby. Sheesh.

Mind and Cosmos/ Thomas Nagel

Still slowly working my way through Mind and Cosmos by Thomas Nagel. It's a bit of a slog; he uses words like phenomenology, teleology, epistemology, and reductionism the way most writers use 'door,' 'stone,' and 'ground.' But his main thesis, I must acknowledge, is intriguing, although I remain skeptical.

He is non-reductionist. He rejects the notion that pure material (chemical/physical) explanations can solve the mind/body problem or account for consciousness and mental life, and especially for rationality. He makes a fairly convincing argument that higher order consciousness and rationality is very unlikely to arise from purely material natural selection. He is not arguing for God, but for an element of nature that is inherently subjective and mindlike (to paraphrase; he doesn't use that word).

In fact, he rejects the notion that life itself is likely to have originated from purely physical processes; SOME form of teleology or inherent mind nature is necessarily implied. He doesn't have a coherent theory of what was involved, but he does make a strong argument that the sort of purely Dawkinsian/sociobiological explanation for intelligent living beings is just not plausible. Sometimes it's the role of philosophy to identify what we do not know, not to inform us of the way things are.

One thing he says that I like (which can be true even in a materialist reductionist interpretation) is that we, as conscious and (sometimes) rational beings, ARE, each of us individually and all of us collectively, a manifestation of the waking to awareness of the universe. (Because you can think of the conscious beings as the aspect of the universe that is aware, if you choose to look at it purely materially).

Romney wishes he could turn back the clock

So Romney says if he could turn back the clock and expose Obama's "lie" that people could keep their health plans under the A.C.A., he wouldn't have lost the election.  Remember this is a health plan modeled pretty closely on the very same models used in Romney's health care plan for Massachusetts, which had the same issue: some health insurers withdrew noncompliant plans (plus health insurers sent cancel letters like this every year to a large number of people anyway; it's what they do). 

Just shows how lucky we were to have avoided having this guy at the helm.

Thoughts on SETI... what if we succeed?

What would actually happen if SETI were successful, and some kind of signal from an extraterrestrial civilization were actually discovered?

Although the SETI effort is in deep financial trouble right now, it seems likely that in some way or other the Hat Creek Array will be reinstated and continue searching before long. Seth Shostak has plotted a timeline based on expected searches, and the estimated probability of a detectable civilization based on the Drake Equation (Google it if not familiar). Conservatively, these folks believe that it’s fairly likely detection of a civilization capable of communicating with us will occur sometime between now and 2050. I am personally skeptical for a variety of reasons which I’ve discussed on this blog (Search), but let’s just stipulate it’s certainly a possibility.

What would happen? Here are my speculations:

First, there would be a great deal of public interest. It would travel the breadth and depth of popular culture worldwide as the Greatest Meme Ever. But there is something important to bear in mind. We will not be having a chat with aliens. At best, we will glean some kind of meaning from a one-way signal, because if the conservative estimates are correct, and there are 10,000 communicating civilizations among the 300 billion stars of the Milky Way (I would guess more like 10 to 100, but let’s stick with 10,000), that means the nearest one is probably 500 to 1000 light years distant… so two way conversations would be very tedious indeed. 

It’s not at all clear that we would even be able to decipher a “message,” if we did receive one, but even unequivocal proof that living beings capable of technology exist at all would be one of the most momentous discoveries in human history.

Shostak has given his reasons for thinking that any civilization we contact will likely be a “machine civilization,” because the potential of technology to surpass the ability of living beings to “think” is already at a threshold in our, presumably quite young, civilization. I doubt this, too, for other reasons I’ve also discussed on this blog, but I’m not sure this is critical. The key point is that, just statistically, it’s a near certainty that any beings we contact will be far more technologically advanced than we are.

And this is the great unknown of SETI. What exactly would that mean? Would we be the recipients of a technology transfer that would transform our lives?

We really cannot know, but it seems likely that if it proves possible to discern meaning from a signal, and if the signal is rich enough in content, it probably would contain information that would catapult scientific knowledge, at least in some fields, far beyond anything anyone can meaningfully speculate about; and the same may apply to technologies as well.

As I’ve intimated, I’m somewhat of a SETI skeptic. But, the upside of value to be potentially gained from success, and the natural curiosity of people to just want to know what’s out there, more than justifies the relatively minor expenditure. (Currently, the US government is not spending anything on this effort; it’s entirely privately funded).

As for those who fear alien invasion, or our culture being overwhelmed like the Tahitians by the Europeans… well, we’re in a pretty fair pickle anyway, so I’ll take my chances. But, seriously, these arguments are ignorant. The distances to the stars are so great that it’s just not worth it to try to exploit other star systems. If “they” are out there, it’s a fair certainty that their only interest in us will be purely out of the same interest we have: to find out what’s out there. The universe is literally full of matter and energy, and there is nothing to be gained from hostility to remote neighbors; now, or ever.

Results from the Late Lamented Kepler Mission

I was watching a youtube from early in the Kepler mission (Jon Jenkins ; http://www.youtube.com/watch?v=UNGviQ0LPDQ if you wanna look at it), and it set out the "critical questions" the mission (now unfortunately over) was intended to answer. I will essay to say what they found out, based on listening to a number of NASA and other science website lectures on the subject.

• • Are terrestrial planets common or rare?
  
  
  • What are their sizes and orbital distances?
    
  • How often are they in the habitable zone?

First, it's worth pointing out what Kepler was for and what it did in the broadest terms. It's a space telescope, in solar orbit, that looked at only one small patch of sky in the Constellation Cygnus, along the disk of the Milky Way. It critically examined the "sunlike" stars in that field of view out to an effective distance of about 3000 light years. That's 150,000 stars, more or less similar to the Sun. The point was to try to detect planets, and create some meaningful statistics about what it found.

Turns out what I'll call terrestroid (i.e., small, rocky) planets (e.g., Mercury, Venus, Earth, Mars) are very common. Kepler's methodology, which is detection of transiting planets (crossing the disk of their star as seen from Earth) involves a selection effect: only quite flat ecliptic-plane systems are detected, and only something like 2 or 3% at most of stars viewed in the Kepler field of view will be oriented correctly for detection. Single stars are also heavily favored, because binary star planetary disks, even though the stars (it turns out) may often have planets, are unlikely to be flat enough to have transiting planets.

Still, it's thought that the systems Kepler has and will have detected (once all the data is processed), are relatively well representative of sunlike star systems in general. They found that small rocky planets are actually much more common than gas giants (in the Solar System we have four of each; a typical system might have four or five dense rocky worlds and only 1 or 2 gas planets, and there is not a preference for the rocky worlds to be close in, as formerly thought). So, from this point of view, very roughly earthlike worlds should be common. The question is implicit, what percentage of sunlike stars have planets at all? ... and the answer seems to be most of them, although the exact percentage is not really clear from Kepler data. Unfortunately, the one type of planet that would be most interesting, which is small planets, in the habitable zone of sunlike stars, and with an orbital period approximately similar to Earth's, is a type that the mission did not detect well, because it didn't have a long enough time to form a good baseline. Based on what was seen, there's good reason to believe that such planets (between let's say .9 and 1.5 Earth diameters, and in the zone where water can be liquid on the surface) are not particularly rare. A rough (but informed) guess would be maybe 2 to 5% of sunlike stars have such a planet.

Of note, in the Solar System Earth is the largest of the terrestroid planets, but in most of these systems, rocky planets larger than Earth, up to 2½ Earth diameters (still small enough NOT to have retained their hydrogen envelopes, like Neptune or Uranus), are common. Such planets have been widely labeled "super-Earths" in the popular scientific literature. Various models have been proposed for what the implications of the greater mass and size of these planets would be, but there's a good deal of uncertainty still.

• What is their dependence on stellar properties?

This question is less clearly answered. Kepler did not look at stars dimmer than about K5, nor brighter than F0, so it is intrinsically limited to a category of stars that are actually quite a bit brighter than most stars, which are red dwarfs, on average. Turns out (from other detection methods) that red dwarfs almost always have planets, and the sunlike stars mostly do, too. The "habitable zones" of dimmer stars are very narrow, so it remains likely that sunlike stars are a good deal more likely to have liquid water surface rocky planets than are much dimmer stars. But since dimmer stars (not only the M dwarfs but the dimmer-range sunlike dwarfs, say from G5 to K5) are more common, it's a safe bet that the median, or typical, earthlike world with seas, clouds, mountains, plate tectonics, etc., (let's call them "First Order Earthlike;" the presence of life being another matter), will orbit a star dimmer than the Sun. Just exactly how those numbers will work out is still somewhat uncertain.


Binary stars do, it seems, often have planets (most of this information comes from other planet detection regimes), so it would appear that at least some earthlike worlds could be "Tattooines" (planets orbiting two closely separated stars), or could orbit one of two or more very widely separated stars in a single system (e.g., Alpha Centauri, where planets have been detected). But these, it seems safe to say, will be the exceptions: habitable planets are more likely to be found orbiting single stars, probably by a significant margin.  

• Bottom line question: Are we alone?

Unfortunately, unless there's a big surprise in the final reports, it doesn't appear that Kepler is going to answer this question. There are a number of suggested methods of teasing from the data information about whether life could exist on a planet that's been detected. The atmosphere of a planet transiting a star can affect the spectrum of the star, and from that comparison such things as the presence of ozone in the atmosphere could theoretically be inferred. A planet, for example, that had both methane and ozone detectable in its atmosphere would be so seriously in chemical disequilibrium that, albeit controversially, such a detection would be widely accepted as definitive proof of the existence of life there.* But it hasn't been demonstrated, so far. So while Kepler does not provide any reason to infer that life is not likely, or not present on one or more of the detected worlds, it doesn't confirm that, either. As for the detection of intelligent life; well, not. Again, nothing to rule it out, but nothing to confirm it either.
♦♦

*The point is that if chemicals that will react with each other strongly both exist in the atmosphere of a planet, one or both of them must be continuously replenished, and in the case of oxygen (which yields ozone in the stratosphere), that can pretty much only be life, at least over time... if there were only one such detection, it could be explained away by transitory geological phenomena, but if the signature were detected in several different instances, the conclusion would be that it could pretty much only be a biosignature.