The evolution of extraterrestrial life

This is the third or fourth video I’ve seen of Arvin Ash, and have been impressed with how level headed his thinking is.  (In other words, his biases seem to match up well with mine.)  This one on how alien life might evolve strikes me as right on the money.

(The first few minutes end up being an advertisement for Magellan TV.  It’s over around the 2:41 mark.)

Ash quotes Seth Shostak’s hypothesis that the intelligence we’re most likely to encounter would be machine life.  I think that’s right, although those machines might be be far more organic looking than our current ones.

As the video notes, evolution made life out of the most common elements lying around in the universe.  It strikes me that an advanced civilization would be able to utilize those most common elements for their machines.  And one which has mastered nanotechnology would probably produce machines that act a lot like life.  In other words, if we do encounter an alien intelligence, it might look a lot more like engineered life than what we think of as machines.

That said, per Fermi, I’m not holding my breath for such an encounter.  The Earth has been sitting here with an interesting biosphere for billions of years, with visible complex life for the last 600 million.  If there are alien civilizations sending probes out into the galaxy, we should have been discovered long ago, and the aliens (either as machines or engineered life) should have been here long before we evolved.

Maybe they are here, but hiding, either for a Star Trek style Prime Directive purpose, or for managing the zoo.  Or they could be here and out in the open, but we’re not able to recognize them.  An interesting exercise is to try to ponder what things we’ve always taken as natural that could conceivably be technological artifacts, as difficult for us to recognize as the significance of a fence is to a monkey.

It could be that they were once here but are now extinct, because civilizations all destroy themselves, apparently including their machine progeny.  Or it might turn out that interstellar exploration, even by machines, is so appallingly difficult or costly that no one bothers.

Or they might simply be too far away to have reached us yet.  That’s where my money is.  They may be so far away that we’ll never manage to encounter them before expansion of the universe separates us forever, or our machine progeny may someday encounter their machine progeny somewhere out in the universe, far from either of our places of origin.  (I’d say I hope I’m wrong about this, but I’m not sure that’s true.  It seems an act of faith to assume things would necessarily turn out well in such an encounter for the less developed civilization.)

In the meantime, I think Ash is right.  The type of alien life we’re most likely to encounter is microscopic and unicellular.  In that scenario, we’d probably be on the most developed side.  Probably.  (Remember the havoc a microscopic agent is currently causing in our world, not to mention the famous ending of War of the Worlds.)  Either way, I wonder how that will turn out for the less developed side.

 

SETI vs the possibility of interstellar exploration

Science News has a short article discussing a calculation someone has done showing how small the volume of space examined by SETI (Search for Extraterrestrial Intelligence) is relative the overall size of the galaxy.

With no luck so far in a six-decade search for signals from aliens, you’d be forgiven for thinking, “Where is everyone?”

A new calculation shows that if space is an ocean, we’ve barely dipped in a toe. The volume of observable space combed so far for E.T. is comparable to searching the volume of a large hot tub for evidence of fish in Earth’s oceans, astronomer Jason Wright at Penn State and colleagues say in a paper posted online September 19 at arXiv.org.

“If you looked at a random hot tub’s worth of water in the ocean, you wouldn’t always expect a fish,” Wright says.

I have no doubt that the amount of stars SETI has examined so far is a minuscule slice of the population of the Milky Way galaxy.  And if SETI’s chief assumptions are correct, it’s entirely right to say that we shouldn’t be discouraged by the lack of results so far.

But it’s worth noting what one of those chief assumptions are, that interstellar travel is impossible, or so monstrously difficult that no one bothers.  If true, then we wouldn’t expect the Earth to have ever been visited or colonized.  This fits with the utter lack of evidence for anything like that.  (And there is no evidence, despite what shows like Ancient Aliens or UFO conspiracy theorists claim.)

But to me, the conclusion that interstellar travel is impossible, even for a robotic intelligence, seems excessively pessimistic.  Ronald Bracewell pointed out decades ago that, even if it is only possible to travel at 1% of the speed of light, a fleet of self replicating robot probes (Bracewell probes) could establish a presence in every solar system in the Milky Way within about 100 million years.  That may sound like a long time, but compared to the age of the universe, it’s a fairly brief period.  Earth by itself has existed 45 times longer.

NASA image via Wikipedia

People sometimes respond that the Earth may be in some type of backwater.  The problem here is, if you know about where the Earth is in the Milky Way, in the Orion Spur off the Sagittarius Arm, about halfway between the center and rim of the galaxy, you’ll know that we’re not really in a backwater.  The backwater theory might be plausible if we were thousands of light years off the galactic plane, beyond the rim, or in a cluster far removed from the main galaxy, but we’re not.  Even then, the nature of the self replicating probe propagation is pretty relentless and would still eventually reach backwater stars.

Of course, if there is only one or a few other intelligent species in the galaxy, then it’s entirely possible that their Bracewell probe is here, just lying low, observing us, possibly waiting for us to achieve some level of development before it makes contact.  (Or maybe it has been making contact 2001: A Space Odyssey style.)

But if the number of civilization is in the thousands, as is often predicted by people speculatively playing with the numbers in the Drake equation, then we should have hundreds of those probes lying around.  Given their diverse origins, we shouldn’t expect them to behave with unanimity.  Even if one probe, or coalition of probes, bullied the others, the idea that such an arrangement would endure across billions of years seems implausible.

And the Earth has been sitting here for billions of years, with an interesting biosphere for most of that time.  The idea that none of these self replicating probes would have set up some kind of presence on the planet, a presence we should now be able to find in the geological record, again seems implausible.  Indeed, if they existed, we should expect to have at least some of them in front of us now.

Now, maybe they are in front of us, and we’re just not intelligent enough to realize what we’re seeing.  Monkeys, after all, likely have no understanding of the significance of the buildings and machinery they climb over.  It seems like something we have to keep in mind, but historically it’s never been productive to just assume we can’t understand something, and taking this principle too much to heart seems like it would make it impossible to ever dismiss any dubious notion.

So SETI largely depends on interstellar travel being infeasible.  This is actually the conclusion a lot of radio astronomers have reached.  Could they be right?  I don’t think we know enough to categorically rule out the possibility.  If they are right, then SETI will be our best chance to someday make contact with those other civilizations, even if it’s only composed of messages across centuries or millenia.

As I’ve written here before, my own conclusion is that some form of interstellar exploration is possible, and that life is probably pervasive in the universe, although most of it is microscopic.  Complex life is probably far rarer, although I wouldn’t be surprised if there aren’t thousands of biospheres, or more, in our galaxy that have it.

But intelligent life capable of symbolic thought and building a civilization?  The data seems to be telling us that this is profoundly rare, so rare that the nearest other intelligent species is probably cosmically distant.  If we’re lucky, they might be close enough that we can encounter them before the expansion of the universe separates us forever.  If we’re not lucky, we’ll never have a chance for that encounter.

Unless of course, I’m missing something?

The extraordinary low probability of intelligent life

Marc Defant gave a TEDx talk on the improbable events that had to happen in our planet’s history for us to eventually evolve, along with the implications for other intelligent life in the galaxy.

I find a lot to agree with in Defant’s remarks, although there are a couple points I’d quibble with.  The first, and I’m sure a lot of SETI (Search for Extraterrestrial Intelligence) enthusiasts will quickly point this out, is that we shouldn’t necessarily use the current lack of results from SETI as a data point.  It’s a big galaxy, and within the conceptual space where SETI could ever pay off, we shouldn’t necessarily expect it to have done so yet.

My other quibble is that Defant seems to present the formation of our solar system as a low probability event, or maybe he means a solar system with our current metallicity.  I can’t really see the case for either being unlikely.  There are hundreds of billions of stars in our galaxy, most with some sort of attending solar system.  So I’m not sure where he’s coming from on that one.

My own starting point for this isn’t SETI, but the fact that we have zero evidence for Earth having ever been colonized.  If the higher estimated numbers of civilizations in the galaxy are correct, the older ones should be billions of years older than we are.  They’ve had plenty of time to have colonized the entire galaxy many times over, even if 1% of lightspeed is the best propagation rate.

The usual response is that maybe they’re not interested in colonizing the galaxy, not even with their robotic progeny.  That might hold if there is one other civilization, but if there are thousands, hundreds, even a few dozen?  Across billions of years?  The idea that every other civilization wouldn’t be interested in sending its probes out throughout the galaxy seems remote, at least to me.

But to Defant’s broader point about the probability of intelligent life evolving, there are many events in our own evolutionary history that, if we were to rewind things, might never happen again.

Life seems to have gotten an early start on Earth.  Earth is roughly 4.54 billion years old, and the earliest fossils date to 3.7 billion years ago.  With the caveat that we’re unavoidably drawing conclusions from a sample of one planet’s history, the early start of life here seems promising for its likelihood under the right conditions.

But there are many other developments that seem far less certain.

One crucial step was the evolution of photosynthesis, at least 2.5 billion years ago.  The development of photosynthesis gave life a much more reliable energy source than what was available before, converting sunlight, water, and carbon dioxide into sugars.

And its waste product, oxygen, started the process of oxygenation, increasing the levels of oxygen in Earth’s atmosphere, which would be very important as time went on.  The early atmosphere didn’t have much oxygen.  Indeed, the rise of oxygen levels may have originally been a serious problem for the life that existed at the time.  But life adapted and eventually used oxygen as a catalyst for quicker access to free energy.

The good news with photosynthesis is that there are multiple chemical pathways for it, and it’s possible it evolved multiple times, making it an example of convergent evolution.  That means photosynthesis might be a reasonably probable development.  Still, oxygen producing photosynthesis doesn’t seem to have arisen until the Earth was more than halfway through its current history, which doesn’t make it seem very inevitable.

The rise of eukaryotes may be a more remote probability.  The earliest life were simple prokaryotes.  Eukaryotes, cells with organelles, complex specialization compartments, arose 1.6-2.1 billion years ago.  All animal and plant cells are eukaryotes, making this development a crucial building block for later complex life.

Eukaryotes are thought to have been the result of one organism attempting to consume another, but somehow instead of consuming it, the consuming organism entered into a symbiotic relationship with the consumed organism.  This low probability accident may have happened only once, although no one knows for sure.

Yet another crucial development was sexual reproduction, arising 1-1.2 billion years ago, or when Earth was 73% of its current age.  Sexual reproduction tremendously increased the amount of variation in offspring, which arguably accelerated evolution.  Who knows how long subsequent developments might have taken without it?

Oxygen had been introduced with the rise of certain types of photosynthesis, but due to geological factors, oxygen levels remained relatively low by current standards until 800 million or so years ago, when it began to rise substantially, just in time for the development of complex life.  The Cambrian explosion, the sudden appearance of a wide variety of animal life 540-500 million years ago, would not have been possible without these higher oxygen levels.

Complex life (animals and plants) arose in the last 600-700 million years, after the Earth had reached 84% of its current age.  When you consider how contingent complex life is on all the milestones above, it’s development looks far from certain.  Life may be pervasive in the universe, but complex life is probably relatively rare.

Okay, but once complex life developed, how likely is intelligent life?  There are many more low probability events even within the history of animal life.

Earth’s environment just so happens to be mostly aquatic, providing a place for life to begin, but with enough exposed land to allow the development of land animals.  In general, land animals are more intelligent than marine ones.  (Land animals can see much further than marine ones, increasingly the adaptive benefits of being able to plan ahead.)  A 100% water planet may have limited opportunities for intelligence to develop.  For example, mastering fire requires being in the atmosphere, not underwater.

Defant mentions the asteroid that took out the dinosaurs and gave mammals a chance to expand their ecological niche.  Without an asteroid strike of just the right size, mammals might not have ascended to their current role in the biosphere.  We might still be small scurrying animals hiding from the dinosaurs if that asteroid had never struck.

Of course, there have been a number of intelligent species that have evolved, not just among mammals but also among some bird species, the surviving descendants of dinosaurs.  Does this mean that, given the rise of complex life, human level intelligence is inevitable?  Not really.  While there are many intelligent species (dolphins, whales, elephants, crows, etc), the number of intelligent species that can manipulate the environment is much smaller, pretty much limited to the primates.

(Cephalopods, including octopusses, can manipulate their environment, but their short lives and marine environment appear to be obstacles for developing a civilization.)

Had our early primate ancestors not evolved to live in trees, developing a body plan to climb and swing among branches, we wouldn’t have the dexterity that we have, nor 3D vision, or the metacognitive ability to assess our confidence in making a particular jump or other move.  And had environmental changes not driven our later great ape ancestors to live in grasslands, forcing them to walk upright, and freeing their hands to carry things or manipulate the environment, a civilization building species may never have developed.

None of this is to say that another civilization producing species can’t develop using an utterly different chain of evolutionary events.  The point is that our own chain is a series of many low probability events.  In the 4.54 billion years of Earth’s history, only one species, among the billions that evolved, ever developed the capability of symbolic thought, the ability to have language, art, mathematics, and all the other tools necessary for civilization.

Considering all of this, it seems like we can reach the following conclusions.  Microscopic single celled life is likely fairly pervasive in the universe.  A substantial subset of this life probably uses some form of photosynthesis.  But complex life is probably rare.  How rare we can’t really say with our sample of one, but much rarer than photosynthesis.

And intelligent life capable of symbolic thought, of building civilizations?  I think the data is telling us that this type of life is probably profoundly rare.  So rare that there’s likely not another example in our galaxy, possibly not even in the local group, or conceivably not even in the local Laniakea supercluster.  The nearest other civilization may be hundreds of millions of light years away.

Alternatively, it’s possible that our sample size of one is utterly misleading us and there actually are hundreds or even thousands of civilizations in the galaxy.  If so, then given the fact that they’re not here, interstellar exploration, even using robots, may be impossible, or so monstrously difficult that hardly anyone bothers.  This is actually the scenario that SETI is banking on to a large extent.  If true, our best bet is to continue searching with SETI, since electromagnetic communication may be the only method we’ll ever have to interact with them.

What do you think?  Is there another scenario I’m missing here?

Arrival, the shape of aliens, and bridging the communication barrier

arrival_movie_posterThis weekend, I watched the movie ‘Arrival‘.  It starts off with the now common scenario of several floating ships appearing in the skies around the world.  But unlike most movies in this mold, it focuses on humanity’s efforts to communicate with the aliens and understand why they’ve come.  The protagonist is an expert in linguistics.

I found this movie to be uncommonly intelligent and high quality science fiction, of a type that we rarely see in cinema.  I’ve heard it’s won and been nominated for various awards.  In my opinion, it’s well deserved.  I highly recommend it.

That said, I’m going to quibble with a couple of its aspects.  I won’t spoil anything that you wouldn’t see in the first act, but if having even bits of that spoiled bothers you, you may want to skip this post until you’ve seen it.

I’m not going to quibble with the existence of the aliens, or why they arrived when they did.  A common criticism I have of alien invasion movies is that the aliens usually choose to show up when we can resist them, rather than any of the previous 4.54 billion years when the planet was a sitting duck.  But I actually think the movie has a good answer for that, which I won’t spoil.

Okay, first quibble.  The movie goes out of its way to portray the aliens as utterly, well, alien.  On the one hand, I very much appreciate this.  Too often, media sci-fi portray aliens as humans with maybe an extra bump on their forehead or in overall humanoid form but maybe with reptilian skin or something, together with all too human emotions and attitudes.  Historically, some of this came from technological constraints on what could be shown.  But with CG technology being what it is today, this excuse, still somewhat plausible for television, doesn’t really cut it for high production movies.

That said, in its attempt to make the aliens profoundly different, I think the movie ignores some simple realities.  Extraterrestrial life would undoubtedly be very different from Earth life, but the laws of physics put limits on just how strange it could be.

For example,we never see eyes on the aliens.  (Or at least I couldn’t ever make out any.)  Now, it’s possible that an alien that evolved in a consistently dark or opaque environment, such as an underground sea or in a thick opaque atmosphere, might never evolve vision.

But we see the aliens communicating visually, which implies some kind of ability to take in information from electromagnetic radiation (light).  And eyes weren’t a one time mutation in Earth history.  From what I’ve read, they evolved several times in independent evolutionary lines.  In other words, eyes are one of the features that evolution tends to converge on.  The aliens didn’t have to be portrayed with two stereoscopic eyes.  They could have had many, like on spiders.

The other is the overall body plan of the aliens.  They don’t come across as having much dexterity.  But as I’ve noted before, the only civilization producing species on this planet needed more than intelligence, but also the ability to physically manipulate the environment.  It’s why a primate species currently rules the planet instead of a cetacean, elephantine, corvine, or other type of intelligent species.

I’m not saying that the aliens needed to have humanoid body plans.  Ant-like bodies with prehensile limbs might have done the trick.  But the movie aliens needed to have better physical abilities than what was portrayed.  Their portrayed bodies might have been dexterous in a liquid environment, similar to cephalopods, but that didn’t appear to be the environment they were in.

My second quibble is with the effort to communicate with the aliens.  If you’ve seen the movie,  you understand this issue’s place in the plot, but the initial decision to translate written language doesn’t make that much sense.  As Seth Shostak of SETI (Search for Extraterrestrial Intelligence) has pointed out, it makes a lot more sense to attempt initial communication with pictures.

This makes sense when you consider that the earliest human writing evolved from using pictures to convey concepts.  Over time, the pictures got streamlined into symbols for each word or concept.  It was thousands of years before the idea of letters standing in for individual speech sounds developed.  Attempting to jump over all that with an utterly alien mind seems like the hard way to do it.

Of course, conveying complex information with pictures wouldn’t itself be easy.  For example, how do you get across the main question the humans had for the aliens, “Why have you come?”  But a series of pictures showing the alien ships approaching humans, followed by alternating pictures of humans dead or alive might have given the aliens a quick chance to make their intentions clearer.  And once you had a basic form of communication going, a common symbolic vocabulary could be worked out, eventually allowing more sophisticated exchanges.

A much tougher challenge might be if the aliens didn’t have visual senses.  Imagine trying to build a common vocabulary with a bat like alien that sensed the world through echolocation, or one that thought and moved on vastly different time scales, such as conscious trees.  But even then, we’d still live in the same universe, and there would have to be some common overlapping ways of perceiving the world.  It might come down to small model statues arranged in sequences to convey scenarios.

Of course, it’s always possible to engage in rationalizations to explain away these quibbles with the movie.  And as I indicated above, this is a movie that is far more intelligent than your typical sci-fi film.  Not the least because it gave me an excuse to talk about alien body plans and communication strategies 🙂

Why alien life will probably be engineered life

Martin Rees has an interesting article at Nautilus: When We Find Aliens, We Might Find Something Like the Borg

This September, a team of astronomers noticed that the light from a distant star is flickering in a highly irregular pattern.1 They considered the possibility that comets, debris, and impacts could account for their observations, but each of these explanations was unlikely to varying degrees.2 What their paper didn’t explore, but they and others are beginning to speculate, is that the flickering might be caused by enormous structures built by an advanced civilization—whether the light might be evidence of ET.

In thinking about this possibility, or other similarly suggestive evidence of extraterrestrial life, an image of an alien creature might come to mind—something green, perhaps, or with tentacles or eye stalks. But in this we are probably mistaken. I would argue that any positive identification of ET will very likely not originate from organic or biological life (as Paul Davies has also argued), but from machines.

Few doubt that machines will gradually surpass more and more of our distinctively human capabilities—or enhance them via cyborg technology. Disagreements are basically about the timescale: the rate of travel, not the direction of travel. The cautious amongst us envisage timescales of centuries rather than decades for these transformations.

A few thoughts.

First, I haven’t commented yet here about KIC 8462852, the star Rees mentions in the first paragraph.  It would be beyond cool if this turned out to be something like a partial Dyson swarm or some other megastructure.  But with these types of speculation, it pays to be extra skeptical of propositions we want to be true.  Possibility is not probability.  I think the chances that this is an alien civilization are remote, but I can’t say I’m not hoping.

On the rest of Rees’s article, I largely agree.  (I’m sure my regular readers aren’t shocked by this.)  I do have one quibble though.  Rees uses the terms “robotic” or “machine life”.  In cases where it would make sense to have a body of metal and silicon, such as operating in space or some other airless environment, I think it’s likely that’s what would be used (or its very advanced equivalent).

But when operating inside of a biosphere, I suspect “machine life” might be more accurately labelled as “engineered life”.  In such an environment, an organic body, designed and grown by an advanced civilization for the local biosphere, might be far more useful and efficient than a machine one.  An organic body could get its energy from the biosphere using biological functions such as eating and breathing.  This might be substantially more efficient than carrying a power pack or whatever.

If we met such life, they might well resemble classic sci-fi aliens in some broad fashion.  Nor do I think we should dismiss the possibility that the form of such aliens might not stray too far from their original evolved shapes.  Even the advanced machine versions might well resemble those original shapes, at least in some contexts.

Of course, that original shape might still be radically different than anything in our experience, such as Rees’s speculation about something that starts as an evolved integrated intelligence.  And after billions of years, engineered life may inevitably become an integrated intelligence, at least on the scope of a planet.  (The speed of light barrier would constrain the level of integration across interstellar distances.)

Snowden’s answer to the Fermi Paradox and its assumptions

The Fermi Paradox is the question that, if the conditions for life in the galaxy are as ubiquitous as they appear to be, so that there should be hundreds, if not thousands of alien civilizations out there, then where is everyone?  Why have we found no evidence for any for those civilizations?  And why aren’t they here?

Edward Snowden has a proposed answer:

“When you look at encrypted communications, if they are properly encrypted, there is no real way to tell that they are encrypted. You can’t distinguish a properly encrypted communication, at least in the theoretical sense, from random noise,” says Snowden. He suggests that over time all societies realize that encryption is a necessity. “So if you have an alien civilization trying to listen for other civilizations, or our civilization trying to listen for aliens, there’s only one small period in the development of their society where all of their communications will be sent via the most primitive and most unprotected means.”

This is an interesting idea, although it’s a variation of another one that’s been around for a while.  Many have speculated that a society that simply digitally encodes all of their signals might make them indistinguishable from natural noise.  Digitally encoding a signal requires protocols, which we, of course, wouldn’t be privy to.  Encryption would just make it even more unlikely that we’d detect it.

But this answer makes a large assumption, that interstellar exploration of any type is impossible, or so monstrously costly that no one ever bothers.  On the face of it, the idea of Star Trek like exploration might well be impossible.  But when you consider ideas like AI probes exploring the galaxy at 1% the speed of light, the notion of exploration being impossible starts to look overly pessimistic.  If those probes were self-replicating, they’d be able to fill the galaxy in 20-30 million years, a long time by human standards, but peanuts on geological or cosmological time scales.

Of course, another possibility is that such exploration is possible, and that the probes or similar technology are here, but keeping hidden.  We can’t eliminate this possibility, except that the idea that an alien intelligence wouldn’t be interested in researching our biosphere seems far fetched, or that if they’re doing so, that we wouldn’t find any indications of it.

Another possibility is that they are here and not being hidden at all, but that we’re simply too primitive to even distinguish them from the natural environment, similar to how a monkey probably regards a building as just another rock, or a vehicle as just another animal.  Again, it doesn’t seem like we can eliminate this possibility, but I can’t see that it’s especially productive to dwell on it.

This always brings me back to the simplest explanation, that intelligent life is profoundly rare, and that the closest civilization may be millions, or maybe even billions of light years away.

G-HAT (Glimpsing Heat from Alien Technologies)

For those interested in the post about finding advanced civilizations in other galaxies by their heat emissions, Paul Gilster at Centauri Dreams has a write up about the study, including links to additional material as well as the actual paper.

I found that this part clarified the seeming contradiction in the Science Daily article.

The currently reported work tells us that none of the galaxies resolved by WISE in this study contain Type III civilizations that are reprocessing 85 percent or more of the starlight of their galaxy into the mid-infrared. And as mentioned above, out of 100,000 galaxies, only fifty show a mid-infrared signature that could be considered consistent with reprocessing more than 50 percent of the starlight.

These fifty point to the further investigations ahead.

The overall endeavor of which the study is a part appears to be named G-HAT (Glimpsing Heat from Alien Technologies).   Gilster links to a site that looks like it has lots of additional information on it, along with some interesting articles.

Searching for advanced civilizations in other galaxies: 50 possible candidates found?

At first, this article seems like a bit of a downer:
Search for advanced civilizations beyond Earth finds nothing obvious in 100,000 galaxies — ScienceDaily.

After searching 100,000 galaxies for signs of highly advanced life, a team of scientists has found no evidence of advanced civilizations there. The idea behind the research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths.

…”Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” Wright said. “This same basic physics causes your computer to radiate heat while it is turned on.”

Theoretical physicist Freeman Dyson proposed in the 1960s that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. It was not until space-based telescopes like the WISE satellite that it became possible to make sensitive measurements of this radiation emitted by objects in space.

However, somewhat contradicting the title of the article and its opening passage, we have this snippet:

Wright reports, “We found about 50 galaxies that have unusually high levels of mid-infrared radiation. Our follow-up studies of those galaxies may reveal if the origin of their radiation results from natural astronomical processes, or if it could indicate the presence of a highly advanced civilization.”

I’m not entirely sure what to make of this passage given the apparent contradiction, but it sounds like we have 50 possible candidate galaxies for advanced civilizations.  (Emphasis on the word “possible” here.)

Based on the information the article provides, it seems obvious that the scientists were looking for Type III civilizations on the Kardashev scale.  A Type I civilization has harnessed all of the energy on its native planet.  (We’re not a Type I civilization yet).  A Type II civilization has harnessed all of the energy of its native star, possibly using concepts like Dyson spheres or swarms.  And a Type III civilization will  have harnessed all of the energy in its galaxy, or, at least for purposes of this study, enough to be noticeable across intergalactic distances.

Of course, we have no real idea how possible a Type III civilization actually is.  It would involve engineering on scales that currently seem hard to imagine.  But given enough time (think hundreds of millions of years), there doesn’t seem to be anything in the laws of physics that prevent it.  We also can’t be sure that some observed astronomical phenomena that we’re chalking up to nature might not turn out to be mega-structures created by extraterrestrial intelligence.

But given the age of the universe, and the fact that there’s no evidence of Earth ever having been colonized in its 4.5 billion year history, it seems likely that if there are advanced civilizations out there, they’re too far away to have reached us yet.  50 out of 100,000 galaxies sounds like about the right number.  The nearest advanced civilization may be several hundred million light years away.

Unless they find natural explanations for the high levels of mid-infrared radiation.  Then the closest advanced civilization might might be billions of light years away, or even outside our visible universe.

Subsurface oceans everywhere and the possible pervasiveness of life

Well, it now looks like Ganymede, one of Jupiter’s moons, has a subsurface ocean.

Ganymede’s great distinction among moons – apart from its size – is that it has its own magnetic field.

Hubble has managed to track that field’s behaviour by watching how it draws in and excites space particles, generating a glow of ultraviolet light around the satellite’s north and south poles.

But this intrinsic magnetic field also interweaves with Jupiter’s, and the aurora “rock” back and forth as a result of the interplay.

It is by modelling the expected rocking against what is observed by Hubble that scientists can infer something about the internal structure of the moon. And they now say a salty ocean at depth is the best explanation for what they see.

It seems like these subsurface oceans are all over the place in the outer solar system.

Ganymede is just one of a large list of objects in the Solar System now thought to hide an ocean deep below the surface. These include the dwarf planets Pluto and Ceres; other Jupiter moons – Europa and Calisto; Saturn’s moons Enceladus, Titan and Mimas; and possibly Neptune’s moon, Triton.

“The Solar System is now looking like a pretty soggy place,” joked Jim Green, the US space agency’s director of planetary science.

In some ways, this shouldn’t be too surprising.  In the outer solar system, where temperatures are typically far below -100 °C, ice is basically a type of rock, and water is essentially a molten form of that ice rock, in the same way as magma is to the rock we’re familiar with.

But all of these subsurface oceans give us lots of environments that have the potential to host life similar to how we understand it, in that they have liquid water coupled with an energy source (whatever is keeping the water warm enough to be a liquid).  One mystery of the origin of life is how likely that origin is to occur.  If it’s more likely, then there’s more life in universe.

If, despite lots of places where conditions are favorable for it, we find don’t find life anywhere else in the solar system, then that may indicate that life is fairly rare in the universe.  On the other hand, if we do find it, and we can establish that it’s not somehow related to life on Earth, then it seems like it indicate that life is pervasive throughout the universe.

How could life on Ganymede be related to life on Earth?  It seems farfetched, but in an ancient solar system with asteroid strikes flinging debris into space, it’s very possible that microbes could be exchanged between planets.  Martian rock has been detected in some of the meteorites that have crashed to Earth.  That said, the outer solar system is much farther away, and any transfer between here and there seems much more tenuous.

None of this would have too much bearing on how prevalent intelligent life is in the universe, except perhaps to set a possible upper bound on it.  Life existed on the Earth for billions of years before intelligence evolved, with intelligent tool using species being very rare.  Even if life is pervasive in the universe, intelligent life is likely still exceedingly rare.

Three conditions are necessary for SETI to succeed

The Parkes 64 metre radio telescope at the Par...
(Photo credit: Wikipedia)

Tom Hartsfield has a post up at Real Clear Science criticizing both the Drake equation and SETI:

If you like science fiction, you’re probably familiar with the Drake equation. This famous one-line formula solves for the number of intelligent alien civilizations within our galaxy with whom we might be able to communicate. Supporters of the search for extraterrestrial life (SETI) often refer to the expression to bolster their case.

There’s just one BIG problem with the Drake equation. It’s completely useless! In fact, I believe it may actually misrepresent the search for ET and limit our ideas about it.

Hartsfield goes on the discuss the impossibility (at least currently) of knowing the values for each of the variables.  Because of this inability to test or observe the various values, he says, the formula is non-scientific.

He then takes aim at SETI (the search for extraterrestrial intelligence):

The worst thing about the Drake equation is that it gives us a false idea of grasping the problem we are trying to solve. A mathematical equation connotes some scientific study or understanding of a subject. But this is misleading: SETI is simply NOT a scientific endeavor. It’s entirely a leap of faith, albeit a leap that uses tools devised by science. It’s like searching for paranormal activity with an electronic sound recorder.

Now, I happen to think that, due to the Fermi Paradox (if there are thousands of civilizations out there, why aren’t any of them here?), the probability of large numbers of civilizations within our galaxy is pretty small.  That doesn’t mean there aren’t civilizations in other galaxies, but they may be hundreds of millions of light years away.

That being said, I think Hartsfield is being overly harsh in his assessment.  The Drake equation has never been meant to be anything other than a stimulus for discussion.  Most people who understand this subject know that it’s essentially just structuring our ignorance.  Given its original goal, and given that people still talk about it today, I think it is fairly successful.

Is it scientific?  That depends on your definition of science, but I think the variables are things humanity may be able to measure, someday.  A scientific theory doesn’t have to be testable immediately in order to be considered science; it just needs to be testable in principle.  I don’t know too many people who would actually call the Drake equation a theory, but to what extent it’s modelling the problem might eventually be testable, at some point in the future.  I think everyone acknowledges that the Drake equation is almost certainly incomplete, in that there are probably numerous factors that influence the final number that we’re simply not aware of yet, but that applies to many things in science.

I think calling SETI unscientific is simply engaging in polemics.  SETI is definitely a long shot.  But the search is being conducted carefully and empirically.  Saying that the people who are going about it aren’t being scientific, comparing them to paranormal investigators and the like, is just making a value judgment about their enterprise while pretending to be objective.

Now, as I said, I do think SETI is a long shot.  There are certain things that have to be true for it to work.

  1. There needs to be a large number of civilizations out there.  Enough that a number of them are close enough for us to detect them.
  2. Pervasive interstellar travel needs to be impossible, or so monstrously difficult that hardly anyone bothers.  Otherwise they would have been here long ago.  Even if only 1% of light speed is achievable, that’s still fast enough for a fleet of self replicating probes to colonize the galaxy in 100 million years.   (No, there’s no evidence that they’ve been here, despite what the Ancient Aliens people say.)
  3. They need to communicate in a manner that is detectable with our current technology.  If there are civilizations out there, they may be advanced in ways we can’t fathom, and us attempting to listen in on them may be far more fruitless than a primitive hunter-gatherer tribe attempting to listen in on global communications, by watching for smoke signals.

It seems to me that these three constraints make success for SETI unlikely, but not impossible.  And nothing about how unlikely it is to be successful necessarily makes it unscientific.

Personally, given 2 above, one strategy to find extraterrestrial intelligence may be to search for probes in the solar system.  It may be that there are several already here, laying low.  Of course, if they are here and dormant, you have to wonder what they’re waiting for, how far advanced the civilization on the third planet is going to have to be before they initiate contact.  And given the vastness of the solar system, if they don’t want to be detected, the chance of us being able to do so seems remote.