ET, call Lexington

If you needed more evidence that we're living in surreal times, some scientists have collaborated with the Tourism Board of Lexington, Kentucky to send a message to aliens inviting them to come to the city for a visit.

The message was sent via infrared laser toward TRAPPIST-1, a multi-planet system about forty light years from Earth.  Astonishingly, they actually got permission from the Federal Aviation Administration -- not a government office known either for its flexibility or its sense of humor -- to beam the message out.  The message, in coded bitmap form, contained information regarding the intent of the transmission, some photographs of the Lexington area, and an audio recording of blues musician Tee Dee Young.

"The bitmap image is the key to it all," said Andrew Byrd, a linguistics expert at the University of Kentucky, who was one of the scholars involved in the project.  "We included imagery representing the elements of life, our iconic Lexington rolling hills, and the molecular structure for water, bourbon, and even dopamine because Lexington is fun."

It also contained the message, "Come to Lexington!  We have horses and bourbon.  Just don't eat us."

I feel obliged to interject here that I'm not making any of this up.

The Lexington Tourism Board's promo art for the project, which I also did not make up

Regular readers of Skeptophilia know that the possibility of alien life -- perhaps intelligent life -- is a near-obsession with me, but I'm not sure this is really the way to go about trying to contact it.  While TRAPPIST-1 isn't a bad choice given the fact that it's fairly close and we know it has seven planets, there's no indication any of them host life.  Four of the planets appear to orbit within the star's "Goldilocks Zone," where the temperatures are "just right" for water to exist in liquid form, but that doesn't mean the planets have liquid water, or even atmospheres.  The fact that the planets have such tight orbits -- the farthest one only has an orbital radius six percent of Earth's, and orbits its star in nineteen days -- suggests they're probably tidally locked, meaning the same side of the planet always faces the star.  (I wrote about the difficulty of life evolving on a tidally-locked planet a year ago, if you're curious to read more about it.)

Then there's the problem of waving hello at aliens who might be vastly more powerful than we are and would respond by squashing us.  Stephen Hawking addressed this in stark terms back in 2010, saying, "We don't know much about aliens, but we know about humans.  If you look at history, contact between humans and less intelligent organisms have often been disastrous from their point of view, and encounters between civilizations with advanced versus primitive technologies have gone badly for the less advanced.  A civilization reading one of our messages could be billions of years ahead of us.  If so, they will be vastly more powerful, and may not see us as any more valuable than we see bacteria."

Of course, if there are intelligent aliens out there, they probably already know about us.  At least the ones under 104 light years away do, because there's an expanding bubble of radio and television transmissions sweeping outward from us at the speed of light that began with the first commercial radio broadcast in 1920.  Assuming any aliens on the receiving end are at least as smart and technologically capable as we are, they're probably already decoding those transmissions and listening to Fibber McGee and Molly and watching Lost in Space, after which they will definitely think we're no more valuable than bacteria.

The last issue -- and this may be the good news, here, if you buy what Hawking said -- is that because TRAPPIST-1 is forty light years away, any aliens who might live there won't receive the message until 2064, and the earliest we could get a response is 2104.  Even if they have some kind of superluminal means of travel and jumped into their spaceships as soon as they got the message, it wouldn't be until the 2060s that they could even potentially get here.  

At least the Lexington Tourism Board has a good window of time to get their hotels ready for the influx of alien tourists.  And if they turn out to be hostile, at that point (if I'm still alive) I'll be over a hundred years old, and I figure that an alien laser pistol blast to the face is about as dramatic a way to check out as I could ask for, so I suspect I'll be fine with the Earth being invaded regardless which way it goes.

So the Lexington Tourism Board's efforts fall squarely into the "No Harm If It Amuses You" department.  And I guess the more time people spend focusing on this sort of thing, the less they'll spend dreaming up new and different ways to be awful to each other.  So as far as that goes, I'm all for sending messages to the stars.

Even if the best things you can think of to talk about are horses, bourbon, and dopamine.

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A cosmic slide whistle

In 1894, physicist Albert Michelson said, "It seems probable that most of the grand underlying principles [in science] have been firmly established …  An eminent physicist remarked that the future truths of physical science are to be looked for in the sixth place of decimals."

The irony of this statement is twofold.  First, within thirty years, the entire field of physics would be upended twice, by Einstein's Special and General Theories of Relativity, and from the development by Niels Bohr, Louis de Broglie, and Erwin Schrödinger of the Quantum Model.  Second, it was the null result from the experiment Michelson himself performed with Edward Morley that disproved the existence of the luminiferous aether and directly led to Einstein's revolutionary theories about the nature of light and motion.

The fact is, there is still a ton of stuff we don't fully understand, and then there are all the things that we don't even know we don't know.  The universe is full of mystery, and there will be plenty to keep scientists occupied for a very, very long time.

Take, for example, a paper last week in Monthly Notices of the Royal Astronomical Society about a bizarre twist on an already poorly-understood phenomenon -- the fast radio burst.  These sudden explosive blasts in the radio region of the spectrum, lasting between 0.001 and 3 seconds, pack as much energy in that time as the entire Sun emits in three days.  Some are transient, but others -- like the euphoniously-named FRB 180916.J0158+65 -- have a regular periodicity, in this particular case 16.35 days.

[Image licensed under the Creative Commons ESO/M. Kornmesser, Artist’s impression of a fast radio burst traveling through space and reaching Earth, CC BY 4.0]

Since their discovery in 2007, hundreds of fast radio bursts have been observed.  Given their unpredictability and ephemeral nature -- you have to have your radio telescope aimed at exactly the right place in the sky at exactly the right time, and you have a window of under three seconds to see them -- it's probable that they are insanely common, and we just miss 99% of them.  Canadian astrophysicist Victoria Kaspi estimates that over ten thousand fast radio bursts happen somewhere in the sky every single day, so there's potentially a huge amount of data out there to study if we can only figure out a way to observe them.

Explanations for what these things could be are all over the map, and include hitherto-unknown behavior of neutron stars, magnetars, black holes, collapsing/dying supergiant stars, or some combination thereof.

Or an alien intelligence trying to signal us.  Admit it, you knew this had to come up.

The bottom line is the astrophysicists still don't know what causes fast radio bursts, much less why some repeat and some don't.  And the whole thing just got a lot weirder with the discovery by observers at the SETI (Search for Extraterrestrial Intelligence) Institute, who found a fast radio burst that had 35 explosive outbursts -- and each one slid up the frequency scale before it ended, drawing comparisons to an enormous outer space slide whistle.

What could cause a fast radio burst to sweep up the frequency scale in that fashion is, at the moment, beyond guessing.  All we know is that is that what was already a mystery just became a hell of a lot more mysterious.

So I think Michelson may have been a wee bit hasty in proclaiming science to be settled except insofar as calculating things to six decimal places.  I suspect that a closer estimate -- if it were possible to do such a thing -- is that the bits of the universe we understand well are hugely outnumbered by the bits we still haven't a clue about.  I prefer the assessment made by Carl Sagan: "Out there, something incredible is still waiting to be known."

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Remnants of forgotten civilizations

As silly as it can get sometimes, I am a dedicated Doctor Who fanatic. I'm late to the game -- I only watched my first-ever episode of the long-running series about seven years ago -- but after that, I went at it with the enthusiasm you see only in the born-again.

The best of the series tackles some pretty deep stuff.  The ugly side of tribalism ("Midnight"), the acknowledgement that some tragedies are unavoidable ("The Fires of Pompeii"), the Butterfly Effect ("Turn Left"), the fact that you can't both "play God" and avoid responsibility ("The Waters of Mars"), the sad truth that you can sometimes give it your best game and still lose ("The Haunting of Villa Diodati"), the devastating fact that the ones orchestrating war are seldom the ones who suffer because of it ("The Zygon Inversion"), and the terrible necessity of personal self-sacrifice ("Silence in the Library").  Plus, the series invented what would be my choice for the single most terrifying, wet-your-pants-inducing alien species ever dreamed up, the Weeping Angels (several episodes, most notably "Blink").

So it shouldn't have been a surprise when Doctor Who got a mention an article in Scientific American, but it still kinda was.  It came up in a wonderful piece by Caleb Scharf called "The Galactic Archipelago," which was about the possibility of intelligent life in the universe (probably very high) and the odd question of why, if that's true, we haven't been visited (Fermi's paradox).  Here at Skeptophilia we've looked at one rather depressing answer to Fermi -- the "Great Filter," the idea that intelligent life is uncommon in the universe either because there are barriers to the formation of life on other worlds, or that once formed, it's likely to get wiped out completely at some point.

It's even more puzzling when you consider the fact that it would be unnecessary for the aliens themselves to visit.  Extraterrestrial life paying a house call to Earth is unlikely considering the vastness of space and the difficulties of fast travel, whatever the amazingly-coiffed Giorgio Tsoukalos (of Ancient Aliens fame) would have you believe.  But Scharf points out that it's much more likely that intelligent aliens would have instead sent out self-replicating robot drones, which not only had some level of intelligence themselves (in terms of avoiding dangers and seeking out raw materials to build new drones), but could take their time hopping from planet to planet and star system to star system.  And because they reproduce, all it would take is one or two civilizations to develop these drones, and given a few million years, you'd expect they'd spread pretty much everywhere in the galaxy.

But, of course, it doesn't seem like that has happened either.

Scharf tells us that there's another possibility than the dismal Great Filter concept, and that's something that's been nicknamed the "Silurian Hypothesis."  Here's where Doctor Who comes in, because as any good Whovian will tell you, the Silurians are a race of intelligent reptilians who were the dominant species on Earth for millions of years, but who long before humans appeared went (mostly) extinct except for a few scattered remnant populations in deep caverns.

The Silurian Madame Vastra in the episode "Deep Breath," played by the incomparable Neve McIntosh

A while back, astronomers Gavin Schmidt and Adam Frank, of NASA and the University of Rochester (respectively), considered whether it was possible that an intelligent technological species like the Silurians had existed millions of years ago, and if so, what traces of it we might expect to find in the modern world.  And what Schmidt and Frank found was that if there had been a highly complex, city-building, technology-using species running the Earth, (say) fifty million years ago, what we'd find today as evidence of its existence is very likely to be...

... nothing.

Scharf writes:

[Astrophysicist Michael] Hart's original fact [was] that there is no evidence here on Earth today of extraterrestrial explorers...  Perhaps long, long ago aliens came and went.  A number of scientists have, over the years, discussed the possibility of looking for artifacts that might have been left behind after such visitations of our solar system.  The necessary scope of a complete search is hard to predict, but the situation on Earth alone turns out to be a bit more manageable.  In 2018 another of my colleagues, Gavin Schmidt of NASA's Goddard Institute for Space Studies, together with Adam Frank, produced a critical assessment of whether we could even tell if there had been an earlier industrial civilization on our planet.

 
As fantastic as it may seem, Schmidt and Frank argue -- as do most planetary scientists -- that it is actually very easy for time to erase essentially all signs of technological life on Earth.  The only real evidence after a million or more years would boil down to isotopic or chemical stratigraphic anomalies -- odd features such as synthetic molecules, plastics, or radioactive fallout.  Fossil remains and other paleontological markers are so rare and so contingent on special conditions of formation that they might not tell us anything in this case.

 
Indeed, modern human urbanization covers only on order of about one percent of the planetary surface, providing a very small target area for any paleontologists in the distant future.  Schmidt and Frank also conclude that nobody has yet performed the necessary experiments to look exhaustively for such nonnatural signatures on Earth.  The bottom line is, if an industrial civilization on the scale of our own had existed a few million years ago, we might not know about it.  That absolutely does not mean one existed; it indicates only that the possibility cannot be rigorously eliminated.

(If you'd like to read Schmidt and Frank's paper, it appeared in the International Journal of Astrobiology and is available here.)

It's a little humbling, isn't it?  All of the massive edifices we've created, the far-more-than Seven Wonders of the World, will very likely be gone without a trace in only a few million years.  A little more cheering is that the same will be true of all the damage we're currently doing to the global ecosystem.  It's not so surprising if you know a little geology; the current arrangement of the continents is only the most recent, and won't be the last the Earth will see.  Because of erosion and natural disasters, not to mention the rather violent clashes that occur when the continents do shift position, it stands to reason that our puny little efforts to change things won't last very long.

Entropy always wins in the end.

The whole thing puts me in mind of one of the first poems I ever read that made a significant impact on me -- Percy Bysshe Shelley's devastating "Ozymandias," which I came across when I was a freshman in high school, and which is still a favorite.  It seems a fitting way to conclude this post.

I met a traveller from an antique land,
Who said—Two vast and trunkless legs of stone
Stand in the desert.  Near them, on the sand,
Half sunk a shattered visage lies, whose frown,
And wrinkled lip, and sneer of cold command,
Tell that its sculptor well those passions read
Which yet survive, stamped on these lifeless things,
The hand that mocked them, and the heart that fed;
And on the pedestal, these words appear:
"My name is Ozymandias, King of Kings;
Look on my Works, ye Mighty, and despair!"
Nothing beside remains.  Round the decay
Of that colossal Wreck, boundless and bare
The lone and level sands stretch far away.

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Room for exploration

As a followup to yesterday's post, about my generally dubious take on the claim of a Mexican scientist that he'd discovered fossilized alien bodies, today we're going to look at why we haven't run across aliens yet.  As big as the universe is, it seems like we should have heard from someone by now.  What are we, a bad neighborhood, or something?  Do the aliens go zooming by the Earth, making sure their windows are rolled up and their doors are locked?

I mean, Elon Musk alone would be justification for their doing so, but it's still kind of disappointing.

I've discussed the Fermi Paradox here at Skeptophilia before -- and the cheerful idea of the Great Filter as the reason why we haven't heard from alien life.  As I explained in a post a while back, the explanation boils down to three possibilities, nicknamed the "Three Fs."

We're first, we're fortunate, or we're fucked.

Being an aficionado of all things extraterrestrial, that has never sat well with me.  The idea that we might be all alone in the universe -- for any of the three Fs -- is just not a happy answer.  

Yes, I know, I always say that the universe is under no obligation to act in such a way as to make me happy.  But still.  C'mon... Vulcans?  Time Lords?  Ewoks?  G'gugvuntts and Vl'hurgs?  There's got to be something cool out there.  With luck, lots of cool things.  The Dentrassi, the Ood, Quantum Weather Butterflies, the Skithra, Andorians, the Vashta Nerada...

Okay, maybe not the Vashta Nerada.  But my point stands.

The Andromeda Galaxy [Image licensed under the Creative Commons Adam Evans, Andromeda Galaxy (with h-alpha), CC BY 2.0]

So I was considerably cheered yesterday when I ran into a study out of Pennsylvania State University that attempted to estimate what fraction of the universe we actually have surveyed in any kind of thorough fashion.  The authors, Jason Wright, Shubham Kanodia, and Emily G. Lubar, write:

Many articulations of the Fermi Paradox have as a premise, implicitly or explicitly, that humanity has searched for signs of extraterrestrial radio transmissions and concluded that there are few or no obvious ones to be found.  Tarter et al. (2010) and others have argued strongly to the contrary: bright and obvious radio beacons might be quite common in the sky, but we would not know it yet because our search completeness to date is so low, akin to having searched a drinking glass's worth of seawater for evidence of fish in all of Earth's oceans.  Here, we develop the metaphor of the multidimensional "Cosmic Haystack" through which SETI hunts for alien "needles" into a quantitative, eight-dimensional model and perform an analytic integral to compute the fraction of this haystack that several large radio SETI programs have collectively examined.  Although this model haystack has many qualitative differences from the Tarter et al. (2010) haystack, we conclude that the fraction of it searched to date is also very small: similar to the ratio of the volume of a large hot tub or small swimming pool to that of the Earth's oceans.  With this article we provide a Python script to calculate haystack volumes for future searches and for similar haystacks with different boundaries.  We hope this formalism will aid in the development of a common parameter space for the computation of upper limits and completeness fractions of search programs for radio and other technosignatures.

The actual analogy Wright and his colleagues used is that saying our current surveys show there's no intelligent life in the universe (except for here, which itself seems debatable some days) is comparable to surveying 7,700 liters of seawater out of the total 1.335 billion trillion liters in the world's oceans.

So basing a firm conclusion on this amount of data is kind of ridiculous.  There could be intelligent alien species out there yelling, "Hey! Earthlings!  Over here!  We're over here!", and all we would have to do is have our radio telescopes pointed a couple of degrees off, or tuned to a different wavelength, and we'd never know it.

Which is pretty cool.  Given the fact that my all-time favorite movie is Contact, I'm hoping like hell that people don't read Wright et al.'s paper and conclude we should give up SETI because it's hopeless to make a thorough survey.  When I think about what poor Ellie Arroway went through trying to convince her fellow scientists that her research was valid and deserved funding... yecch.  And if anything, the current attitudes of the government toward pure research are, if anything, worse than those depicted in the movie.

But despite all that, it's awe-inspiring to know we've got so much room to explore.  Basically... the entire universe.  So my dream when I was a kid, sitting out in my parents' yard with my little telescope, that as I looked at the stars there was some little alien boy in his parents' yard looking back at me through his telescope, may one day prove to be within hailing distance of reality.

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Signals of interest

Usually, when people think about finding extraterrestrial intelligence, they think of radio transmissions -- a trope that has been the basis of dozens of movies and television shows (Contact and Starman immediately come to mind).  Just two days ago I looked at a new approach to detecting biosignatures -- traces of living things, usually in the context of life on other planets -- which involved arguments having to do with complex biochemistry.

Then yesterday, I ran into a new study from the SETI (Search for Extraterrestrial Intelligence) Project describing a recently-developed deep learning technique which goes back to radio astronomy -- and that has already uncovered eight "signals of interest" from previously-analyzed radio telescope data.

Now, before we go any further, allow me to state up front that no one (well, no one credible) is saying any of these signals actually come from you-know-who. 

Don't get your hopes up quite yet.

But this finding does give us alien enthusiast types some hope for answering the Fermi paradox -- "If life is common in the universe, where is everyone?" -- with two rejoinders: (1) we've only studied a vanishingly small slice of the star systems even in our own galaxy; and (2) our previous techniques for analyzing the radio emissions of the systems we have studied still missed some signals that by previously-accepted criteria should warrant a closer look.

All eight signals of interest shared the following three characteristics that put them in the "curious" column:

1. They were narrow-band -- i.e. only peak at a narrow range of frequencies.  Radio signals from natural sources tend to be broad-band.
2. They had non-zero drift rates, meaning they were not moving with the same speed as the observatory.  This rules out terrestrial sources, a constant source of interference with radio telescope data.
3. The signals occurred only at specific celestial coordinates, and the intensity fell off rapidly when the telescope moved from being aimed at those coordinates.

All of these are features you would expect from radio transmissions from an extraterrestrial intelligence.

"In total, we had searched through 150 terabytes of data of 820 nearby stars, on a dataset that had previously been searched through in 2017 by classical techniques but labeled as devoid of interesting signals," said Peter Ma of the University of Toronto, who was lead author of the paper, which appeared in Nature Astronomy.  "We're scaling this search effort to one million stars today with the MeerKAT telescope and beyond.  We believe that work like this will help accelerate the rate we're able to make discoveries in our grand effort to answer the question 'are we alone in the universe?'"

I'm delighted astronomers are continuing to push forward with the search for extraterrestrial intelligence.  They certainly could be forgiven for giving up, considering the fact that since the SETI Institute was founded in 1984, they have yet to find anything that has convinced scientists.  Even with arguments like the one I made in my post two days ago, that purely statistical arguments like the Drake equation suggest that life is common in the universe, the complete lack of hard evidence would certainly be sufficient justification for scientists to put their efforts elsewhere.

That they haven't done so is a tribute not only to their dogged determination, but the importance of the question.  Not only would finding extraterrestrial life (or even better, intelligence) have profound implications for our understanding of astronomy, biochemistry, and biology, it would create seismic shifts in everything from anthropology to theology.  Such a finding would fundamentally and permanently alter our perception of the universe and our own place in it.

Myself, I think that'd be a good thing.  Our species needs period reminders that we're not all that and a bag of crisps.  Finding out that we're only one intelligent species of many would further emphasize that we don't occupy the center of the universe in any sense -- and, hopefully, reinforce our sense of wonder at the forces that have produced life and intelligence not only here on Earth, but throughout the myriad galaxies.

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Assembling aliens

There are a lot of hurdles in detecting extraterrestrial life, and that's not even counting the possibility that it might not exist.

Honestly, I don't think that last stumbling block is all that likely, and it's not just because proving we're not alone in the universe has been one of my dearest wishes since I was six years old and watching the original Lost in Space.  Since astronomer Frank Drake came up with his famous Drake equation in 1961, which breaks down the likelihood of extraterrestrial intelligence into seven individual parameters (each with its own, independent probability), the estimates of the values of those parameters have done nothing but increase.  As only one example, one of the parameters is f(p) -- the fraction of stars that have planetary systems.  When Drake first laid out his equation, astronomers had no certainty at all about f(p).  They were working off a sample size of one; we know the Solar System exists because we live in it.  But was its formation a fluke?  Were stars with planets extremely uncommon?

No one knew.

Now, exoplanet discovery has become so routine that it barely even makes the news any more.  The first exoplanet around a main-sequence star -- 51 Pegasi b -- was discovered in 1995.  Since then, astronomers have found 5,297 exoplanets, with new ones being announced literally every week.  It seems like damn near a hundred percent of stable main-sequence stars have planetary systems, and most of them have at least one planet in the "Goldilocks zone," where the temperatures are conducive to the presence of liquid water.

Even setting aside my hopes regarding aliens, the sheer probability of their existence has, from a purely mathematical standpoint based upon the current state of our knowledge of the universe, improved significantly.

But this still leaves us with a problem: how do we find it?  The distances even to the nearest stars are insurmountable unless someone comes up with warp drive.  (Where are you, Zefrem Cochrane?)  So we're left with remote sensing -- looking for biosignatures.  The most obvious biosignature would be a radio transmission that's clearly from intelligent life, such as the one Ellie Arroway found in Contact; but it bears keeping in mind that through almost all of the Earth's 3.7-billion-odd years it's been inhabited by living creatures, it would have been entirely silent.  Alien astronomers looking from their home worlds toward the Earth would not have heard so much as a whisper.  It's only since we started using radio waves to transmit signals, a century ago, that we'd be detectable that way; and given how much transmission is now done via narrow-beam satellite and fiber optics cables rather than simple wide-range broadcast, it's entirely possible that once the technology improves Earth will go silent once again.  There may only be a short period during which a technological civilization is producing signals that are potentially detectable from a long way away.

So the question remains: how could we determine if an exoplanet had life?

I'm guessing that whatever the aliens look like, it's not this.  Unfortunately.

The tentative answer is to look for other kinds of biosignatures, and the most obvious one is chemicals that "shouldn't be there" -- in other words, that would not form naturally unless there were life there producing them through its metabolic processes.  This, too, is not a simple task.  Not only is there the technological challenge of detecting what's in a distant exoplanet's atmosphere (something we're getting a lot better at, as spectroscopy improves), there's the deeper question of how we know what should be there.  If we find an odd chemical in a planet's atmosphere, how do we know if it was made by life, or by some exotic (but abiotic) chemistry based on the planet's composition and conditions?

We've gotten caught this way before; three years ago, scientists discovered traces of a chemical called phosphine in the atmosphere of Venus, and a lot of us -- myself included -- got our hopes up that it might be a biosignature of something alive in the clouds of our hostile sister planet.  The consensus now is that it isn't -- the amounts are vanishingly small, and any phosphine on Venus is a product of its wild convection and bizarre atmospheric makeup.  So once we detect a chemical on an exoplanet, is there a way to do a Drake-equation-style estimate of its likelihood of forming abiotically?

Astrobiologist Leroy Cronin, of the University of Glasgow, has proposed an answer, based on something he calls "assembly theory."  Assembly theory, significantly, doesn't rely on any kind of analogy to terrestrial life.  Cronin and others are now trying to figure out strategies to find life as we don't know it -- living creatures that might be based upon extremely different chemistry.

What he's done is given us a purely mathematical way to index chemicals according to how many independent steps it takes to create them from simple, pre-existing building blocks.  This molecular assembly number, Cronin says, is directly proportional to its likelihood of being created by a living thing.  As a simple analogy, he shows how you would find the molecular assembly number for the word abracadabra:

1. add a + b;
2. add ab + r;
3. add abr + a;
4. add abra + c;
5. add abrac + a;
6. add abraca + d;
7. add abracad + abra (we'd already created abra in step three).

Seven steps from the primordial building blocks, so the molecular assembly number for abracadabra is seven.

Replace putting letters and letter groups together with steps in a chemical reaction chain, and you have an idea how assembly theory works.

Like the Drake equation, Cronin's method isn't proof.  Finding some complex chemical in an exoplanet's atmosphere, the gas of a nebula, or a meteorite might be suggestive of life, but almost certainly wouldn't convince the doubters without a lot more in the way of evidence.  Still, just as Frank Drake did in 1961, it's nice to have a protocol for determining the likelihood of a biosignature that doesn't depend on our unavoidable Earth-centrism.  Like with the formation of the Solar System, we're familiar with only one kind of life -- the kind all around us, that we ourselves are examples of.  Shaking the bias that all life is Earth-like is not easy.

It's understandable that the creators of Lost in Space and Star Trek visualized almost all of the aliens as basically humans with odd facial excrescences, and that's granting the difficulty of finding a way to portray non-humanoid aliens convincingly using human actors.  When they did manage to get beyond humans with rubber noses, such as in the Lost in Space episode "The Derelict" and the Star Trek episodes "The Devil in the Dark" and "Obsession," the aliens were, respectively, giant mobile bubbles, a tunneling, acid-spewing rock, and a disembodied vampiric mist cloud, all of a which at least gave a shot at trying to visualize what truly non-Earthlike life might be.

I'm hopeful that the work of Cronin and others is moving the new field of astrobiology forward from simple "what ifs" to actual rigorous algorithms for analyzing the spectroscopic data we're gathering from exoplanet atmospheres.  And maybe... just maybe... within my lifetime we'll have enough data to feel confident we've identified for certain what I've been waiting for since I was six: life on another planet.

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Water worlds

My older son has followed in his old man's footsteps, combining a fascination for astronomy, biology, chemistry, and physics with a wild imagination to generate a fantastic universe within which to spin fictional tales.  He is adding a skill I most definitely do not have -- art -- to create a brain-bending saga that I'm sure you will one day see sitting on people's bookshelves.

Just a couple of days ago, we were talking his creation, and were musing about the possibility of alien intelligence, and in particular, the fact that the kind of intelligence we humans evolved was very much driven by the kind of planet we live on.  The tools we create, which facilitated our dominance of the Earth, required availability of metal ores and the ability to make fire to smelt them.  Even our combative, competitive nature may well owe its origins to our having evolved in a place (east Africa) with plentiful large predators, scarce resources, and seasonal drought.

What kind of intelligence might develop on a planet with no dry land?  That intelligence can develop in aquatic life forms is undeniable; by most biologists' estimates whales and dolphins have about the same intelligence as the great apes, and at least some of the vocalizations they make might qualify as actual language.  (That question is currently not settled, but there have been some suggestive recent studies supporting that contention.)

But even though whales and dolphins are intelligent, they're non-technological.  It's entirely imaginable that there could be aquatic life forms that might exceed humans in memory storage, recall, complexity of communication, and flexible problem-solving, and yet they still might not have anything we would call hard technology.  Note that the water-world in the Star Wars universe -- Kamino, the origin of the eponymous clones of the Clone Wars -- still had to have a solid (if floating) surface, made of conventional materials like metals, glasses, and plastics, in order to have a technology similar enough to that in the rest of the canon for the story to be plausible.

It all comes down to how much the evolution of intelligent life is constrained -- hemmed in by drivers that would likely generate similar forms in all conceivable habitable worlds.  My conclusion is that there are constraints, but they're few in number -- things like having complex sensory organs, having those organs and the central processing unit (brain) located near the anterior end, having some kind of appendages for moving through whatever medium the planet is outfitted with, and having some mechanism for communicating between individuals.  That's about it.  Otherwise... all bets are off as to what we'll find when we first set foot on another planet.

[Image is in the Public Domain courtesy of NASA/JPL]

This significantly complicates the possibility of finding intelligent extraterrestrial life.  There could be a water-world populated by something like super-intelligent dolphins, and they would have no capacity for (nor, likely, any interest in) building radio transmitters and receivers.  So to us, such a planet would appear completely silent and devoid of life.  Our SETI (Search for Extraterrestrial Intelligence) efforts have been confined by necessity to looking for signals of the kind we ourselves send -- which might also restrict us to finding only the life that evolved on planets with conditions extremely similar to Earth.

The result is that we might well miss most of what's out there.  The reason this comes up -- besides my conversation a couple of days ago with Lucas -- is an article by University of Arizona astronomer Chris Impey that just appeared in The Conversation.  Impey tells us something that should encourage people like me, who would very much like it if extraterrestrial life exists out there somewhere; that a third of all exoplanets are "super Earths," planets with a mass between that of the Earth and Neptune.  Further, most of these orbit cool dwarf stars, which have a vastly longer life span than Main Sequence stars like the Sun, so there would be a great deal longer for life to evolve and become complex.  Impey says that the "most habitable of all possible worlds" would fall into the super Earth category -- roughly twice the mass of Earth, and twenty to thirty percent larger in volume.  (The reason is that a larger planet would have a thicker atmosphere with a greater heat-storage capacity, and thus be more resistant to the rapid changes in climate that have plagued the Earth since its formation.)

However, if that thicker atmosphere contained water vapor, you might well be looking at planets completely covered by a deep ocean -- a water-world, where any life would evolve along very different pathways that it has here.  In that case, the only way to see that it exists from our perspective here on Earth is by biosignatures, gases in the atmosphere that would be unlikely to exist unless there were life present to create them.  (An example is free oxygen in Earth's atmosphere; it's so reactive that without photosynthesizers like plants and phytoplankton producing it continuously, it would get locked up by chemical reactions and disappear from the atmosphere entirely.)

So despite what you might have seen on Star Trek, the most common intelligent alien life out there might not be bipedal humanoids with rubber facial prostheses.  We smart hairless apes might actually be vastly in the minority -- a possibility I find fascinating but a little mind-boggling.

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Can you hear me?

Most of you have probably heard of SETI -- the Search for Extraterrestrial Intelligence.  SETI is an umbrella term that links dozens of different projects and approaches, but is most often connected to the SETI Institute, founded in 1984 specifically to address the question of whether extraterrestrial life exists, and if so, whether we could communicate with it.

Just detecting the evidence of an extraterrestrial intelligence (assuming there is any) is fraught with difficulties.  To begin with the most glaring problem, there are an estimated 250 billion stars in the Milky Way alone, which makes for a hell of a survey area.  And even if you start by looking only at the relatively nearby ones, there's still the question of what exactly you're looking for.  Radio wave signals are an obvious choice, and we have radio telescopes that do exactly that, but to start with, that's an awfully broad band of frequencies (between 300 and 3,000 kHz).  Even to pick it up would mean not only listening to the right region of space, but being tuned to the right frequency at the right time.

But there are other problems.  Suppose there is an intelligent civilization on a star 25 light years from us, and they're sending out a radio signal of some sort.  There are two possibilities, of which the first is that the signal comes from their own intraplanet communications, like the oft-discussed bubble of transmissions from our early radio and television, which is currently carrying snippets of I Love Lucy and Gilligan's Island that are sweeping past planets and stars seventy-odd light years away.  The second is that the signal is a deliberately-deployed beacon, an interstellar lighthouse specifically for communication with other civilizations.

Each of these presents its own problems.  In the first case, the bubble of radio transmissions gets fainter and fainter as it expands, according to the inverse-square law of intensity.  So as funny as it is to think of some extraterrestrials on the third planet of Vega judging humanity by The Beverly Hillbillies, my suspicion is that by the time it arrived the signal would be so faint that it would be nearly impossible to detect.  (And that's not even considering degradation of the signal from passing through interstellar dust and gas.)

The second sounds more promising, but it too has a difficulty.  If you're beaming a signal toward another star, you get an improvement in intensity because the logical way to do it is to collimate the beam as tightly as possible.  You're still subject to the inverse-square law, but a tightly-collimated beam has such a narrow cross-section and high intensity that it could retain its power for a great deal longer.  (Consider that even back in 1962, the Lunar Laser Ranging experiment successfully collimated a laser tightly enough that they were able to reflect it from the Moon, and detect the reflected pulse back here on Earth 2.6 seconds later.)  But the narrower your beam, the smaller the area of your potential target.  You would have to have a good reason to choose a particular star, or at least a region of space, or your signal would miss detection entirely.

So broad signal/low intensity, narrow signal/smaller sample size.  There doesn't seem to be any way around those equal-and-opposite problems.

There's also the difficulty of how exactly you could encode a message that would be understandable to a non-human intelligence.  Once the signal is received, how do you make sure the aliens can figure out what it's saying?  This question has most recently been tackled by a team led by Jonathan Jiang of NASA's Jet Propulsion Laboratory, and this is in fact why the topic comes up.  Jiang has made a proposal to send out a message aimed toward the densest patch of stars in the night sky, in the direction of the galactic center in the constellation Sagittarius.  To be successful such message would have to contain enough information to (1) tell its recipients that it's not just an anomalous radio blip from a natural source, (2) give an indication of how to translate it, and (3) tell the extraterrestrials a little about where and who we are.

Jiang's proposal addresses all three.  It first contains an easily-deciphered binary code that links to our base-10 counting system, and lists off the first 24 prime numbers.  (Shades of the wonderful movie Contact, in which SETI researcher Ellie Arroway recognized that there is no naturally-occurring process that would produce blips in prime-number groups.)  Once that (hopefully) convinces the aliens that we're relatively intelligent, the message goes on to communicate our understanding of time (using a standard time interval -- the spin-flip transition of hydrogen -- that would hopefully be known to any technological species).  There would be information using this universal clock telling when the signal was sent, which would tell the recipient how far away we are.  Last, there would be a binary-encoded sketch of two humans, and some basic information about our biology and biochemistry, reminiscent of the gold plaques placed on Pioneer 10 and Pioneer 11 when they were launched in (respectively) 1972 and 1973.

[Image is in the Public Domain courtesy of NASA/JPL]

There's also the question, of course, of whether alerting the aliens to our presence (and giving them directions for how to get here, no less) would be a good thing.  Back in 2011, physicist Stephen Hawking warned us that first contact might not be quite as cheery as it was in Star Trek.  "We only have to look at ourselves to see how intelligent life might develop into something we wouldn’t want to meet," Hawking said.  "I imagine they might exist in massive ships, having used up all the resources from their home planet.  Such advanced aliens would perhaps become nomads, looking to conquer and colonize whatever planets they can reach.  If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans...  They could be billions of years ahead of us technologically.  If so, they will be vastly more powerful and may not see us as any more valuable than we see bacteria."

Which is both humbling and scary.  The positive side of all this is that even if the aliens do turn out to be hostile, they're still very far away.  Let's say that there is intelligent life on a planet orbiting Gliese 581 (the home of the first Earth-like planet ever discovered).  Gliese 581 is 20.4 light years away, so it's in our general neighborhood.  If we sent a signal to them saying hello, they'd get it 20.4 years from now, and we'd receive their response in (minimally) 40.8 years.  If instead of just sending a radio response back they were offended by our sending them biochemistry and pictures of naked people, and launched an attack fleet, it'd be even longer before they arrived here.  So even if they're hostile, we're safe for some time.

That's assuming that they haven't found some way to overcome the light-speed barrier and get here at superluminal velocities.  In that case, we might well be fucked.

But, like Hawking, I still think we should do it.  Finding out we're not alone in the cosmos would be the most stupendous discovery humans have ever made.  Jiang and his team don't have a proposed date for beaming out our "Can you hear me?" message, but there's no reason why it couldn't be done soon.  And if it does reach an extraterrestrial intelligence, we'll just have to cross our fingers and hope it's not the Daleks, Stenza, Sontarans, or the Crystalline Entity.

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A signal from our neighborhood

I try to keep my rational brain engaged, but man, sometimes it's hard going.

Like when I read the story that popped up over at Scientific American last Friday.  My ears perked up at the very first line: "It's never aliens, until it is."

Written by Jonathan O'Callaghan and Lee Billings, it tells about a recent discovery made by "Breakthrough Listen," the search-for-extraterrestrial-intelligence program launched by entrepreneur Yuri Milner in 2015.  Despite scanning the skies for five years looking for something that might be a sign of alien intelligence, Breakthrough Listen hasn't found anything that couldn't be explained using ordinary astrophysics...

... until now.

Maybe.  I hate to add that word, but... "rational brain engaged," and all.  There's a lot that's exciting about what they discovered, not least that the signal they found comes from Proxima Centauri -- the nearest star to the Sun, right in our own neighborhood at only 4.2 light years' distance.  (Okay, I probably shouldn't say "only."  4.2 light years is about 25,000,000,000,000 miles.  One of the fastest spacecraft ever made by humans, Voyager 2, would still take 73,000 years to reach Proxima Centauri -- if it were heading that way, which it's not.)

The proximity of the signal's source is hardly the only exciting thing about it.  After all, the universe has plenty of radio sources, and all the ones we've found so far have purely prosaic explanations.  The signal is weirdly compressed, occupying a narrow band of frequencies centering around 982 megahertz.  Interestingly, this is a frequency range that is usually fairly empty of transmissions, which is one of the reasons the signal stood out, and decreases the likelihood that it's some kind of human-made source being picked up accidentally.  "We don’t know of any natural way to compress electromagnetic energy into a single bin in frequency,” said astrophysicist Andrew Siemion, who is on the team that analyzed the signal.  "Perhaps, some as-yet-unknown exotic quirk of plasma physics could be a natural explanation for the tantalizingly concentrated radio waves, but for the moment, the only source that we know of is technological."

The "tantalizing" part is that we know for sure that Proxima Centauri has at least one Earth-like planet -- Proxima b, which is 1.2 times the size of the Earth, and orbits its star in eleven days.  (If that doesn't sound very Earth-like, remember that Proxima Centauri, as a red dwarf, is a lot less massive than the Sun, so its "Goldilocks zone" -- the band of orbital distances that are "just right" for the temperatures to allow liquid water" -- is a lot closer in, and the planets in that region travel a lot faster.)  Red dwarf stars are prone to solar flares, so some of the more pessimistic astrophysicists have suggested that the radiation flux and general turbulence would destroy any nearby planets' atmosphere, or at least shower the surface with sufficient ionizing radiation to prevent the development of complex biochemistry, let alone life.

But it's important to realize that this, too, is a surmise.  Truthfully, we don't know what's down there on Proxima b -- just that it's got a rocky surface and a temperature range that would allow for liquid oceans, rivers, and lakes.

Just like here.

In short, finding a suspicious radio signal from the nearest star to our own is pretty amazing, even if I *wince* *grimace* keep my rational brain engaged.

The fact is, even the scientists -- normally the most cautious of individuals -- are sounding impressed by this.  "It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before," said Sofia Sheikh of Pennsylvania State University, who led the team that analyzed the signal and is the lead author on an paper describing it, scheduled for publication this spring.

Honestly forces me to add that there's one bit of information about the signal that points away from it being a technosignature: unlike the signal detected at the beginning of the movie Contact, it has no internal fine structure.  “BLC1 [Breakthrough Listen Candidate 1] is, for all intents and purposes, just a tone, just one note," Siemion says.  "It has absolutely no additional features that we can discern at this point."

But even the doubters are saying it's worthy of further study.  "If it’s an ETI it must eventually be replicable, because it’s unlikely it would be a one-off,” said Shami Chatterjee, a radio astronomer at Cornell University.  "If an independent team at an independent observatory can recover the same signal, then hell yes.  I would bet money that they won’t, but I would love to be wrong."

So would a lot of us, Dr. Chatterjee.  I know we've had other strange signals before, stretching all the way back to the beginnings of radio astronomy and the discovery of incredibly rapid-fire "blinking" of a radio source discovered at Jodrell Bank by astrophysicist Jocelyn Bell Burnell in 1967.  That one also elicited the comment of "we don't know a natural process that could generate such fast oscillation" -- and the source was actually nicknamed "LGM" (Little Green Men) until Burnell showed that the signal was coming from a pulsar, a rapidly-spinning neutron star.

So it was bizarre, perhaps, but not a message from an extraterrestrial intelligence.

In any case, I'll be eagerly awaiting replication and confirmation of the discovery.  Even if it doesn't turn out to be aliens *heavy sigh* it'll probably turn out to be something interesting.  But until then... well, I guess it's premature to request transport to the mother ship, but I can still keep hoping.

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Not long ago I was discussing with a friend of mine the unfortunate tendency of North Americans and Western Europeans to judge everything based upon their own culture -- and to assume everyone else in the world sees things the same way.  (An attitude that, in my opinion, is far worse here in the United States than anywhere else, but since the majority of us here are the descendants of white Europeans, that attitude didn't come out of nowhere.)  

What that means is that people like me, who live somewhere WEIRD -- white, educated, industrialized, rich, and democratic -- automatically have blinders on.  And these blinders affect everything, up to and including things like supposedly variable-controlled psychological studies, which are usually conducted by WEIRDs on WEIRDs, and so interpret results as universal when they might well be culturally-dependent.

This is the topic of a wonderful new book by anthropologist Joseph Henrich called The WEIRDest People in the World: How the West Became Psychologically Peculiar and Particularly Prosperous.  It's a fascinating lens into a culture that has become so dominant on the world stage that many people within it staunchly believe it's quantifiably the best one -- and some act as if it's the only one.  It's an eye-opener, and will make you reconsider a lot of your baseline assumptions about what humans are and the ways we see the world -- of which science historian James Burke rightly said, "there are as many different versions of that as there are people."

[Note:  If you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]

Requiem for an old friend

My fascination for astronomy started a long time ago.  I started learning the constellations when I was about six, and received a telescope as a Christmas present from my grandmother when I was eight.  Just about any clear night it was a good bet I'd be out in my front yard looking up at the stars, wondering what it was like out there, thinking about what other planets might host life -- and if somewhere there was a little alien boy looking back my way and wondering the same thing.

It was about that time that I found out about the Arecibo Observatory in Puerto Rico.  One of the many astronomy books I had called the three-hundred-meter radio dish "our eye on the sky" -- it was my first introduction both to the idea that not all telescopes looked like the little tube with lenses on a stand that I owned, and that it was possible to "see" the sky using wavelengths of light that were invisible to human eyes.  Also, if you were to view the sky with a radio telescope (or in microwaves, or x-rays, or ultraviolet light, or whatever) you would see a very different set of features than the familiar twinkling points of light set against a black background.

In the microwave region, for example, you'd see light coming from basically all directions at once -- the "three degree microwave background radiation" which Arno Penzias and Robert Wilson discovered -- and which is one of our most persuasive pieces of evidence of the Big Bang.  (This discovery was made not at Arecibo but at the Holmdel Horn Antenna in New Jersey.)  X-ray astronomy is how black holes were discovered, and we know about the terrifyingly powerful Wolf-Rayet stars because of telescopes sensitive to the ultraviolet region of the spectrum.

Arecibo, though, was particularly evocative, not only for its function but because of its site, in a limestone sinkhole in the jungles of northern Puerto Rico.  Add to this its role in searching for signs of extraterrestrial life, and you have a combination sure to capture the imagination.  Because of this it made a number of appearances in science fiction, such as the 1994 episode of The X Files called "Little Green Men," and most notably, the amazing 1997 movie Contact, which remains my number-one favorite movie ever, not only for the story but because of a tour de force performance by Jodie Foster as the indomitable astronomer Ellie Arroway.

[Image is licensed under the Creative Commons Mariordo (Mario Roberto Durán Ortiz), Arecibo radio telescope SJU 06 2019 6144, CC BY-SA 4.0]

So it was with considerable sadness that I found out a couple of weeks ago that Arecibo was being permanently dismantled.  Earlier this year, a pair of cable breaks ripped gashes in the dish, and it seemed like the venerable telescope was unrepairable.  As if to confirm that, just two days ago the nine-hundred-ton equipment platform collapsed, falling almost two hundred meters and destroying the entire center of the telescope.

"When we looked outside the control room, we started to see the eventual downfall of the observatory," observatory director Ángel Vázquez said.  "After the breakage of two cables earlier this year, strands of the remaining three cables had been unraveling in recent days, increasing the strain.  And because two of the support towers maintained tension as the collapse occurred, some of the falling equipment was yanked across the side of the dish rather than falling straight down through its focal point...  This whole process took thirty seconds, and an icon in radio astronomy was done."

Vázquez isn't the only one to feel its loss deeply.  "While life will continue, something powerful and profoundly wonderful is gone," said astronomer Seth Shostak, whose work with SETI (the Search for Extraterrestrial Intelligence) was a good part of the inspiration for Contact.

I understand the sentiment.  The whole thing makes me feel something like grief.  Arecibo has been an inspiration to me since I was a child, and its destruction is like losing an old friend.  I know there are other, and more powerful, telescopes out there, but this one seemed to me to be a symbol of our search for something beyond ourselves, for unraveling the secrets of the universe while still right here, looking up into the skies from our home planet.

So farewell to Arecibo.  There will always be something unique and marvelous about the image of that huge telescopic eye in the Puerto Rican jungle.  As Seth Shostak pointed out, its loss won't stop our yearning for knowledge, but it's hard to imagine finding something as grand and iconic to take its place in our imaginations.

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One of the most compellingly weird objects in the universe is the black hole -- a stellar remnant so dense that it warps space into a closed surface.  Once the edge of that sphere -- the event horizon -- is passed, there's no getting out.  Even light can't escape, which is where they get their name.

Black holes have been a staple of science fiction for years, not only for their potential to destroy whatever comes near them, but because their effects on space-time result in a relativistic slowdown of time (depicted brilliantly in the movie Interstellar).  In this week's Skeptophilia book-of-the-week, The Black Hole Survival Guide, astrophysicist Janna Levin describes for us what it would be like to have a close encounter with one of these things -- using the latest knowledge from science to explain in layperson's terms the experience of an unfortunate astronaut who strayed too close.

It's a fascinating, and often mind-blowing, topic, handled deftly by Levin, where the science itself is so strange that it seems as if it must be fiction.  But no, these things are real, and common; there's a huge one at the center of our own galaxy, and an unknown number of them elsewhere in the Milky Way.  Levin's book will give you a good picture of one of the scariest naturally-occurring objects -- all from the safety of your own home.

[Note: if you purchase this book using the image/link below, part of the proceeds goes to support Skeptophilia!]