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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The biochemical zoo

The human/alien hybrid is a common trope in science fiction.  From the angst-ridden half-Vulcan Mr. Spock, to the ultra-competent and powerful half-Klingon B'Elanna Torres, to the half-Betazoid empath Deanna Troi, the idea of having two intelligent humanoid species produce children together is responsible for dozens of plot twists in Star Trek alone.

Much as I love the idea (and the show), the likelihood of a human being able to engage in any hot bow-chicka-bow-wow with an alien, and have that union produce an offspring, is damn near zero.  Even if the two in question had all the various protrusions and indentations more or less lined up, the main issue is the compatibility of the genetic material.  I mean, consider it; it's usually impossible for two ordinary terrestrial species to hybridize -- even related ones (say, a Red-tailed Hawk and a Peregrine Falcon) are far enough apart genetically that any chance mating would produce an unviable embryo.

Now consider how likely it is to have genetic compatibility between a terrestrial species and one from the fourth planet orbiting Alpha Centauri.

Any hope you might have had for a steamy tryst with an alien just got smashed even further by a study that came out of a study from the Tokyo Institute of Technology, Emory University, and the German Aerospace Center a few days ago.  Entitled, "One Among Millions: The Chemical Space of Nucleic Acid-Like Molecules," by Henderson James Cleaves II, Christopher Butch, Pieter Buys Burger, Jay Goodwin, and Markus Meringer, the study shows that the DNA and RNA that underlies the genetics of all life on Earth is only one of millions of possible information-encoding molecules that could be out there in the universe.

It was amazing how diverse these molecules were, even given some pretty rigid parameters.  Restricting the selection to linear polymers (so the building blocks have to have attachment points that allow for the formation of chains), and three constituent atoms -- carbon, hydrogen, and oxygen, like our own carbohydrates -- the researchers found 706,568 possible combinations (counting configurations and their mirror images, pairs of molecules that are called stereoisomers).  Adding nitrogen (so, hooking in chemicals like proteins and the DNA and RNA nitrogenous bases, the letters of the DNA and RNA alphabets) complicated matters some -- but they still got 454,442 possible configurations.

The results were a surprise even to the researchers.  "There are two kinds of nucleic acids in biology, and maybe twenty or thirty effective nucleic acid-binding nucleic acid analogs," said Henderson James Cleaves, who led the study, in an interview in SciTechDaily.  "We wanted to know if there is one more to be found...  The answer is, there seem to be many, many more than was expected."

Co-author Pieter Burger of Emory University is excited about the possible medical applications of this study.  "It is absolutely fascinating to think that by using modern computational techniques we might stumble upon new drugs when searching for alternative molecules to DNA and RNA that can store hereditary information," Burger said.  "It is cross-disciplinary studies such as this that make science challenging and fun yet impactful."

While I certainly can appreciate the implications of this research from an Earth-based standpoint, I was immediately struck by its application to the search for extraterrestrial life.  As I mentioned earlier, it was already nearly impossible that humans and aliens would have cross-compatible DNA, but now it appears that alien life might well not be constrained to a DNA-based genetic code at all.  I always thought that DNA, or something very close to it, would be found in any life form we run across, whether on this planet or another; but the Cleaves et al. study suggests that there are a million or more other ways that organisms might spell out their genetic code.

So this drastically increases the likelihood of life on other planets.  The tighter the parameters for life, the less likely it is -- so the discovery of a vast diversity of biochemistry opens up the field in a manner that is breathtaking.

... but the chance that the aliens will look like this is, sadly, pretty low.

This raises the problem of whether we'll recognize alien life when we see it.  The typical things you look for if you're trying to figure out if something's alive -- such as a metabolism involving the familiar organic compounds all our cells contain -- might cause us to overlook something that is alive but is being carried along by a completely different chemistry.

And what an organism with that completely different chemistry might look like -- how it would move, eat, sense its environment, reproduce, and think -- well, there'd be an embarrassment of riches.  The possibilities are far beyond even the Star Trek universe, with their fanciful aliens that look basically human but with odd facial structures and funny accents.

The whole thing boggles the mind.  And it further reinforces a conclusion I've held for a very long time; I suspect that we'll find life out there pretty much everywhere we look, and even on some planets we'd have thought completely inhospitable.  The "Goldilocks Zone" -- the region surrounding a star where orbiting planets would have conditions that are "just right" for life to form -- is looking like it might be a vaster territory than we'd ever dreamed.

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This week's Skeptophilia book recommendation is for people who have found themselves befuddled by such bizarre stuff as Schrödinger's Cat and the Pigeonhole Paradox and the Uncertainty Principle -- which, truthfully speaking, is probably the vast majority of us.

In Six Impossible Things: The Mystery of the Quantum World, acclaimed science writer John Gribbin looks at six possible interpretations of the odd results from quantum theory.  Gribbin himself declares himself a "quantum agnostic," that he is not espousing any one of them in particular.  "They all on some level sound crazy," Gribbin says.  "But in quantum theory, 'crazy' doesn't necessarily mean 'wrong.'"

His writing is clear, lucid, and compelling, and will give you an idea what the cutting edge of modern physics is coming up with.  It'll also blow your mind -- but isn't good science always supposed to do that?

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

Alien DNA test

Online Critical Thinking course -- free for a short time!

This week, we're launching a course called Introduction to Critical Thinking through Udemy!  It includes about forty short video lectures, problem sets, and other resources to challenge your brain, totaling about an hour and a half.  The link for purchasing the course is here, but we're offering it free to the first hundred to sign up!  (The free promotion is available only here.)  We'd love it if you'd review the course for us, and pass it on to anyone you know who might be interested!

Thanks!

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Today we're going to take a break from subatomic physics and the Big Bang, not to mention the current state of political affairs (and I'm using that in both senses of the word) in the United States, to consider:

DNA tests that are designed to see if you have alien ancestry.

As with so many of the topics I address here at Skeptophilia, I owe this one to Reddit, that amazing clearinghouse for ideas from profound to ridiculous to completely baffling.  The post on Reddit that clued me in to the fact that alien DNA testing is a thing lands toward the "baffling" end of that continuum, although to be fair, the person who found it posted it on r/Skeptic, so they clearly didn't believe it themselves.

It was accompanied by a screencap of the offer on eBay, which I include below:

Being that the print is a little small, let me list the salient features:

• It sounds like your typical DNA analysis kit, wherein you spit into a test tube and send it in.  I did one of these (23 & Me) just out of curiosity, not that there's anything particularly in question about my own ancestry.  My heritage is French, Scottish, German, Dutch, and English, and my DNA came back: French, Scottish, German, Dutch, and English.  At least it speaks well for the accuracy of the analysis, not to mention my genealogical research and the low incidence of infidelity in my family.  (Incidentally, my DNA profile allowed me to connect with four different people whom I had not known before, and who turned out to be fairly close cousins.)
• The difference here is that instead of telling you your ethnic makeup, this test purports to tell you how much of it doesn't originate on planet Earth.  Note that it is accompanied by a highly scary-looking artist's representation of an individual who, if your test turns out to be positive, is apparently your Great-Great-Great Grandpa G'zork.
• It originates in Canada, and you can't have it shipped to the United States.  I find this a little suspicious.  I mean, it could be because it would require the transportation of bodily fluids across national boundaries, which could be a serious issue vis-à-vis disease transmission, but I prefer the hypothesis that it's because here in the United States, they'd prefer it if we don't find out we're actually aliens.  So far, apparently they're keeping Rudy Giuliani in the dark, and he looks a lot more like the aforementioned G'zork than most of the humans I've seen.
• It costs only $15.95 (Canadian).  This is a hell of a deal, especially given what it purports to do.  My 23 & Me test set me back eighty bucks, which I spent to find out what I more or less already knew.  (It did tell me that I have about three hundred "Neanderthal gene markers," which probably explains why I like my steaks on the rare side, and periodically feel like hitting people with a club, especially the ones who walk really slowly while blocking the entire aisle in the grocery store.)

So to any of my Canadian readers who don't mind sacrificing sixteen bucks for a little empirical research, I encourage you to buy a kit, and let us know here at Skeptophilia headquarters about the results.

Having a background in genetics, however, I have to wonder what they're using for their basis of comparison.  I know that in the historical documentary The X Files, the government had lots of deep-frozen alien babies in a lab somewhere, which (of course) Mulder found and (of course again) Scully didn't get to see.  So did they do a genetic analysis of the alien babies?

More importantly, why am I putting so much effort into analyzing this?

My general feeling is that even if alien intelligence exists, it's extremely unlikely that it will have a similar biology to ours, and even less likely that it will encode its genetic material the same way.  (Witness the fact that even related terrestrial species, who have fairly recent common ancestry, can't interbreed.)  So the chance of human/alien hybridization is nil, and that's even assuming they have naughty bits that are of the right size and shape to be compatible with ours.

Anyhow, that's our dip in the deep end for today.  And if you turn out to have alien DNA, I'm sorry if I sounded scornful.  I don't mean to insult your family.

Although I'd make an exception in the case of Rudy Giuliani.

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This week's featured book is a wonderful analysis of all that's wrong with media -- Jamie Whyte's Crimes Against Logic: Exposing the Bogus Arguments of Politicians, Priests, Journalists, and Other Serial Offenders.  A quick and easy read, it'll get you looking at the nightly news through a different lens!

Life out of balance

As anyone who is a regular reader of Skeptophilia knows, I have a bit of an obsession with alien life.

My students know this, too, not because I bring it up in class, but because I have a poster from the Roswell UFO Museum, the Fox Mulder "I Want to Believe" poster, and a ceramic pot shaped like an alien head in my classroom.

I also have a lot of Bigfoot-related stuff, but we'll save that for another time.

Despite my obsession, I recognize the problem with the claim that extraterrestrial life has been detected, or (even more) that alien intelligence has made it here to Earth.  I've examined a lot of claims for both, and none of them have held up to scientific scrutiny.  It's too bad, really; I think one of the best moments I've ever seen in a science fiction movie was when Zefram Cochrane shakes hands with the Vulcan at the end of Star Trek: First Contact.

I've imagined myself many times in the position of being the first human to welcome a friendly alien intelligence to Earth.  The sad truth is that, without warp drive, the interstellar distances are simply too large.  Einstein's General Theory of Relativity, which sets the speed of light as the ultimate universal speed limit, has never been shown to have an exception -- nor that there's some kind of technological workaround.

Dilithium crystals notwithstanding.

So we're kind of stuck here, meaning that if we do detect life on other planets, it'll have to be remotely.  And now three scientists, from the University of Washington and the University of California-Riverside, have shown us how we might do that.

In a paper that came out in Science:Advances this week, titled, "Disequilibrium Biosignatures Over Earth History and Implications for Detecting Exoplanet Life," astronomers Joshua Krissansen-Totton, Stephanie Olson, and David C. Catling have developed a method of figuring out whether an exoplanet hosts life -- by simply analyzing the spectral lines from its atmosphere.

The idea here is that life keeps Earth's atmosphere out of balance -- more specifically, out of chemical equilibrium.  The most obvious example is the presence of diatomic oxygen, which is highly unstable (it is, unsurprisingly, a strong oxidizer).  If all life on Earth were to vanish, the amount of atmospheric oxygen would decline until it was very close to zero, as it interacted with (and was chemically bound up in) rocks and sediments.

As has been so often pointed out in seventh-grade life science classes, without photosynthesis, we'd be monumentally screwed.

So what Krissansen-Totton, Olson, and Catling did is to figure out how far out of chemical equilibrium an atmosphere would have to be to be a significant indicator for the presence of life.  The authors write:

Chemical disequilibrium in planetary atmospheres has been proposed as a generalized method for detecting life on exoplanets through remote spectroscopy.  Among solar system planets with substantial atmospheres, the modern Earth has the largest thermodynamic chemical disequilibrium due to the presence of life.  However, how this disequilibrium changed over time and, in particular, the biogenic disequilibria maintained in the anoxic Archean or less oxic Proterozoic eons are unknown.  We calculate the atmosphere-ocean disequilibrium in the Precambrian using conservative proxy- and model-based estimates of early atmospheric and oceanic compositions.  We omit crustal solids because subsurface composition is not detectable on exoplanets, unlike above-surface volatiles.  We find that (i) disequilibrium increased through time in step with the rise of oxygen; (ii) both the Proterozoic and Phanerozoic may have had remotely detectable biogenic disequilibria due to the coexistence of O2, N2, and liquid water; and (iii) the Archean had a biogenic disequilibrium caused by the coexistence of N2, CH4, CO2, and liquid water, which, for an exoplanet twin, may be remotely detectable.  On the basis of this disequilibrium, we argue that the simultaneous detection of abundant CH4 and CO2 in a habitable exoplanet’s atmosphere is a potential biosignature.  Specifically, we show that methane mixing ratios greater than 10−3 are potentially biogenic, whereas those exceeding 10-2 are likely biogenic due to the difficulty in maintaining large abiotic methane fluxes to support high methane levels in anoxic atmospheres.  Biogenicity would be strengthened by the absence of abundant CO, which should not coexist in a biological scenario.

So that's what is known, in scientific circles, as "pretty freakin' cool."  The SETI Project and other programs designed to detect electromagnetic signals from ET are awesome, but the problem is, it tells us nothing about forms of life out there that for one reason or another might not use electromagnetic transmissions.  In fact, some scientists think that the era of using EM carriers for information might be fairly short -- for us here on Earth, it began about 120 years ago, and could well be drawing to a close already because of better technology.

The proposal by Krissansen-Totton et al. might give us a means of detecting life of all sorts -- not just intelligent life.  Which, as a biologist, I find tremendously exciting.  I mean, if a Vulcan ship isn't going to land in my back yard, I'll take what I can get, you know?

The source of the noise

A common theme in Skeptophilia is that people in general need to learn some scientific terminology.

Not only is science cool, and thus learning about it a worthy goal in and of itself; but knowing how science works, and some of the field's vocabulary, will keep you from being duped.  As we've seen over and over, the world is full of folks who either through ignorance or outright duplicity misrepresent what scientists are doing -- and without adequate mental firepower, you're gonna fall for their nonsense every time.

As an example, this weekend, a story started popping up all over that claimed that we'd finally received a good candidate for an alien signal from an extrasolar planet.  This immediately caught my eye -- it is one of my dearest wishes that we have incontrovertible evidence of alien intelligence before I die.  I'd be perfectly satisfied if it comes in the form of some kind of radio signal, but if an actual alien spacecraft landed in my back yard, that would also be acceptable, at least until they started vaporizing my dogs with laser pistols.

So my reaction was one of cautious enthusiasm.  Cautious, because I suspected that if this had actually happened, it would be all over the news, not just surfacing in the form of links on Twitter and Facebook.  But the stories all made the same claim.  Here's an excerpt from the version that appeared on UFO Blogger:

Astronomers have picked up a mystery "noise" which they believe could be coming from an Earth-like planet in the outer space [sic]. After analyzing the strange signals emitting from the object, scientiscientistssts [sic] are certain that a habitable planet exists some 22 light years away, a report said. 

In 2010, scientists had dismissed the mystery noise or signals as stellar bursts but after the latest research it was clear that an Earth-like planet, or Gliese 581d, has conditions which could support life, and is likely to be a rocky world, twice the size of Earth.

Okay, given the typos and grammar, it's not exactly the most credible of reports.  But all of the links I saw agreed; an extrasolar planet called Gliese 581d, 22 light years from Earth, had been reported as the source of a strange, unexplained noise.  The planet was bigger than Earth, but in the "Goldilocks Zone" -- the "just right" region around its star where water would be in liquid form, and therefore a place where life something like what we have here could evolve.

So immediately I started picturing Star Trek-style aliens, complete with fake rubber alien noses and bad accents.  Then I thought of the amazing final scene in Star Trek: First Contact, which is clearly the best movie the franchise ever produced, wherein Zefram Cochrane shakes hands with a Vulcan for the first time.  And before you know it, I had myself worked up into a lather about the possibilities.

Then I thought, "Calm down, dude.  Verify your sources."  So I typed "noise Gliese 581d" into a Google search to see if I could find out where this information had come from.  Clearly it was all similar enough that it had some kind of common origin, and it wasn't wacky enough to have come from The Weekly World News.  And after five minutes' search, I found the press release in Phys.org that had caused the stir -- the origin of the "noise."

And I put "noise" in quotation marks for a good reason, as you'll see.  The press release was a blurb summarizing a paper in Science by Anglada-Escudé and Tuomi called "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581."  Here's the relevant passage:

A report published in Science has dismissed claims made last year that the first super-Earth planet discovered in the habitable zone of a distant star was 'stellar activity masquerading as planets.' The researchers are confident the planet named GJ 581d, identified in 2009 orbiting the star Gliese 581, does exist, and that last year's claim was triggered by inadequate analysis of the data.

The planet candidate was spotted using a spectrometer which measures the 'wobble', small changes in the wavelength of light emitted by a star, caused as a planet orbits it. In 2014 researchers revisiting the data said that the 'planet' was actually just noise in the data caused by starspots. The possible existence of the planet was widely dismissed without further questioning. 

But now researchers from Queen Mary University of London (QMUL) and University of Hertfordshire have questioned the methods used to challenge the planet's existence. The statistical technique used in the 2014 research to account for stellar activity is simply inadequate for identifying small planets like GJ 581d.

Note the use of the word "noise" twice.  This, apparently, is the source of the story of an alien noise coming from Gliese 581d.

Scientists use the word "noise" differently from the rest of us.  To a scientist, "noise" is scatter in the data, background junk, that might obscure something real and measurable (the "signal").  If you have enough noise, the signal becomes impossible to detect, so reducing the noise in a data set is critical.  A high "signal-to-noise ratio" is what you're after; lots of signal, little noise.  So when the astrophysicists re-analyzed the data from 2009 that had been rejected last year as supporting an Earth-like extrasolar planet around Gliese 581, they found a way of reducing the noise in the data, and were able to confirm that the planet did, actually, exist.

What they did not find was some kind of unexplained noise coming from Gliese 581d.  The noise was the scatter in the data, not some Klingon sending an insulting message at the Earth such as "Hab SoSlI' Quch" ("Your mother has a smooth forehead").

Not that I'm happy to report this, mind you.  No one would be more thrilled than me if we had received an alien communiqué, even if it contained an insult.  But unfortunately, the stories about mysterious and unexplained alien noises turn out to be unmysterious and completely explainable ignorance of bloggers regarding the use of scientific vocabulary.

So we keep waiting.  Given the number of extrasolar planets the astronomers are discovering, I'm still optimistic that one day, we'll find the aliens.  Or maybe they'll find us.  Either way, it'd be amazing, because, after all, Heghlu'meH QaQ jajvam ("Today is a good day to die").