Species, types, and the "No True Scotsman" fallacy

One of the most frustrating of logical fallacies is the No True Scotsman fallacy.

It gets its name from an almost certainly apocryphal story, in which a serial rapist and killer is being pursued by the police in Glasgow, and a Scottish MP encourages the police to search amongst the immigrant population of the city.  "No Scotsman would do such a thing," the MP said.

When the criminal was caught, and turned out to be 100% Scottish, the MP was challenged about his remark.

"Well," he said, drawing himself up, "no true Scotsman would have done such a thing!"

The crux of this fallacy is that if you make a statement that turns out, in view of evidence, to be false, all you do is shift your ground -- redefine the terms so as to make your original point unassailable.

Very few other fallacies have such a capacity for making me want to smack my forehead into a wall as this one.  Someone who commits this fallacy can't be pinned down, can't be backed into a corner, can't receive his comeuppance from the most reasoned argument, the most solidly incontrovertible evidence.  The dancing skills of a master of the No True Scotsman fallacy are Dancing With The Stars quality.

All of this comes up because of an online discussion that I read, and (yes) participated in, a couple of days ago, on the topic of the demonstrability of evolution.  Someone, ostensibly a supporter of evolution but seemingly not terribly well-read on the subject, was using such evidence as the fossil record as a support for the idea.  A creationist responded, "The fossil record, and fossil dating, are inaccurate.  You evolutionists always think that bringing us a bunch of bones and shells proves your point, but it doesn't, because no one can really prove how old they were, and none of them show one species turning into another.  You can't show a single example, from the present, of one species becoming another, and yet you want us to believe in your discredited theory."

Of course, I couldn't let a comment like that just sit there, so I responded, "Well, actually, yes, I can.  I know about a dozen examples of speciation (one species becoming another) occurring within a human lifetime."

Challenged to produce examples, I gave a few, including the ones that I described in an earlier post (Grass, gulls, mosquitoes, and mice, February 9, 2012), and then sat back on my haunches with a satisfied snort, thinking, "Ha.  That sure showed him."

Well.  I should have known better.  His response, which I quote verbatim: "All you did was show that one grass can become another grass, or a mosquito can become another mosquito.  If you could show me a mosquito that turned into a bird, or something, I might believe you."

Now, hang on a moment, here.  You asked me for one thing -- to show one species turning into a different species, in the period of a few decades.  I did so, adhering to the canonical definition of the word species.  And now you're saying that wasn't what you wanted after all -- you want me to show one phylum turning into a different one, in one generation?

I sat there, sputtering and swearing, and not sure how to answer.  So I said something to the effect that he'd pulled a No True Scotsman on me, and had changed the terms of the question once he saw I could answer it, and he'd damned well better play fair.  He humphed back at me that we evolutionists couldn't really support our points, and we both left the discussion as I suspect most people leave discussions on the internet -- unconvinced and frustrated.  So I was pondering the whole thing, and after taking my blood pressure medications I had a sudden realization of where the confusion was coming from.  It was from the idea of a type of organism.

Most people who aren't educated in the biological sciences (and I'm not including just formal education, here; there are many people who have never taken a single biology class and know plenty about the subject) really don't understand the concept of species.  They think in types.  A bird is one type of thing; a bug is a different one.  If you pressed them, they might admit that there were a few types of birds that seemed inherently different.  You have your big birds (ostriches), your medium-sized birds (robins), and your little birds (hummingbirds).  I've had students that have thought this way, and when they hear I'm a birdwatcher, they seem incredulous that this could be a lifelong avocation.  Wouldn't I run out of new birds to see pretty quickly?  When I tell them that there are over 10,000 unique species of birds, they seem not so much awed as uncomprehending.

The phylogenetic tree of birds (Class Aves) [credit: Dr. Gavin Thomas, University of Sheffield, UK]

I suspect that the source of this misapprehension is the same as the source of the general misapprehension regarding the antiquity of the Earth and the origins of life: the Bible.  In Leviticus 11, where they go through the whole unclean-foods thing that eventually would be codified as the Kosher Law, they split up the natural world in only the broadest-brush terms; you have your animals that have hooves and chew the cud, various combinations of ones that don't, creatures that have fins and scales and ones that don't, insects that jump and ones that don't, and a few different classes of birds (which, to my eternal amusement, includes bats).  And that's pretty much it.  Plants were sorted out into ones that had edible parts (wheat, figs, olives), ones that had useful wood (boxwood, cedar, acacia), and ones that had neither of the above (thorn bushes).  And these distinctions worked perfectly well for a Bronze-Age society.  It kept you from eating stuff that was bad for you, told you what you could build stuff from, and so on.  But as a scientific concept, the idea of "types of living things" kind of sucks.  And yet it still seems to live on in people's minds, lo unto this very day.

So, anyway, that was my brief excursion into that least useful of endeavors, the Online Argument.  It gave me a nice example of the No True Scotsman fallacy to write about here.  And it really didn't affect my blood pressure all that much, but it did make me roll my eyes.  Which seems to happen frequently when I get into conversations with creationists.

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The worst century in history

I've always loved a mystery, and for that reason, the European "Dark Ages" have fascinated me for as long as I can recall.

But the moniker itself is off-puttingly self-congratulatory, isn't it?  It's not like Roman rule was that pleasant for your average slob to live under, after all.  Be that as it may, after the conquests of the Roman Empire started to fall apart in the fourth century C.E. from a combination of invasion, misrule, and downright lunacy, things went seriously downhill.  Life was pretty rough until the eighth and ninth centuries, when some measure of order returned as damn near all of Europe coalesced around the Roman Catholic Church, ushering in the Middle Ages.  And what we know about the period in between is... not a hell of a lot.  Accounts are scattered, vague, and full of conflation with mythology and legend.  The few that were written by contemporaries, rather than long after the fact -- such as Gregory of Tours's History of the Franks -- contain as much hagiography as they do history.

St. Gregory and King Chilperic I, from Grandes Chroniques de France de Charles V (fourteenth century) [Image is in the Public Domain]

Which is why I was thrilled to read a paper that appeared in Antiquity about a study of the "worst decade to be alive" -- 536-546 C. E.

The research, which combines the skimpy evidence we have from accounts written at the time with hard scientific data from analysis of ice cores, paints a grim picture.  Writings from the year 536 describe a mysterious "fog" that lasted for eighteen months, generating widespread crop failure and what one Irish cleric called "three years without bread."  From the ice core analysis, medieval historian Michael McCormick and glaciologist Paul Mayewski identified what they believe to be the culprit: a cataclysmic volcanic eruption in Iceland that dropped the global temperature an average of two degrees Celsius in a matter of months.

This was followed by another eruption in 540, and the following year, the single worst plague on record -- the so-called "Plague of Justinian," which killed between a third and a half of the inhabitants of the Eastern Roman Empire, and resulted in so many corpses that people loaded them on ships and dumped them in the Mediterranean.  The disease responsible isn't known for certain, but is believed to be Yersinia pestis -- the same bacterium that caused the Black Death, almost exactly eight hundred years later.  But to give you an idea of the scale, there's reason to believe the Plague of Justinian dwarfed both the fourteenth century Black Death and the Spanish Flu of 1918-1919 -- usually the two examples that come to mind when people think of devastating pandemics.  The death toll is estimated at sixty million.

There probably was a connection between the cold and the plague, too, although not the obvious one that famine triggers disease susceptibility.  Many scholars think that the lack of food, and cold temperatures following a period that had generally been warm, forced mice and rats into homes and on board ships -- not only in close proximity to humans, but in their means of travel.  The fleas they carried, which are vectors for the plague, went with them, and the disease decimated Europe and beyond.

The effects of the eruption, however, were felt all over the Earth.  Tree ring analysis from North America shows 540 and the years following to have been unusually cold, with short-to-nonexistent growing seasons.  Volcanic dust is found in those layers of ice cores everywhere they exist.  Famines occurred in Asia and Central America.

All in all, a crappy time to be around.

Things didn't rebound for almost a hundred years.  Archaeologist Christopher Loveluck, of the University of Nottingham, found traces of dust containing significant amounts of lead in ice strata from the year 640, which he believes were due to a resurgence in silver smelting for coinage.  (I suppose if there's a hundred years during which your three main occupations are (1) not starving, (2) not freezing, and (3) not dying of a horrible disease, then making silver coins is kind of not on your radar.)  And the tree rings and ice cores bear out his contention that this indicates better conditions; although there were a couple of other volcanic eruptions we can see in the glacial records, none were as big as the one in 536.  The silver smelting, Loveluck says, "... shows the rise of the merchant class for the first time."  Things, finally, were improving.

What's coolest about this study -- despite its gruesome subject -- is how hard science is being brought to bear on understanding of history.  We no longer have to throw our hands up in despair if we're interested in a time period from which there were few written records.  The Earth has recorded its own history in the trees and the glaciers, there for us to read -- in this case, telling us the tale of the worst century the human race has ever lived through.

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Fish star

Fomalhaut is the brightest star in the southern constellation of Piscis Austrinus, the Southern Fish.  At a declination (stellar latitude) of −29° 37′, it's seldom visible where I live, but I did get a good look at it when I was in Ecuador a few years ago.  It's bright -- a first-magnitude star -- but looked brighter because of the elevation; when you're up in the mountains, on a clear night it's hard to recognize constellations because there are so many visible stars.

The star's odd moniker comes directly from the Arabic Fom al-Haut, "the mouth of the whale."  As always, though, other cultures saw it differently.  The Chinese gave it the fanciful name Běiluòshīmén, meaning "the north gate of the military camp."  To the Persians it was Hastorang, one of the "Four Royal Stars."  (The other three were Aldebaran, Regulus, and Antares.)  It seems to have had some significance to indigenous Americans; the two-thousand-year-old Earthwork B, in Mounds State Park in Indiana, seems to line up with the rising of Fomalhaut, but the reason is unknown.  To the Moporr, an indigenous people in South Australia, it was a powerful male deity named Buunjill.  Not to be outdone, in the Lovecraftian mythos Fomalhaut is the home of the Great Old One Cthugha, who appeareth unto mankind as a fiery sphere and basically scareth the absolute shit out of everyone who seeeth him.

More prosaically, though, Fomalhaut is interesting to astronomers as the eighteenth brightest star in the sky overall, and the third brightest star known (or thought) to have a planetary system (after the Sun and Pollux).  It's young, something on the order of four hundred million years old.  (I know that seems pretty damn old, but keep in mind that the Sun is over ten times older than that.)  It's a Type A star, which doesn't mean that it's hard-working and tightly-wound, but that it's blue-white in color and has strong emission lines from hydrogen and ionized metals.  (Another, better known, Type A star is Vega, made famous as the home system of the aliens in the wonderful movie Contact.)

What's coolest about this star, though -- and the reason it comes up today -- is its ring of dust and debris, which was photographed directly in 2012 by ALMA (the Atacama Large Millimeter/submillimeter Array):

[Image licensed under the Creative Commons LMA (ESO/NAOJ/NRAO). Visible light image: the NASA/ESA Hubble Space Telescope ; Acknowledgement: A.C. Boley et al., ALMA observes a ring around the bright star Fomalhaut, CC BY 4.0]

The James Webb Space Telescope just got even more detail; it was able to discern not only the outer ring of debris but an inner ring, comparable to the Sun's Kuiper Belt and Asteroid Belt, respectively. which suggests to astrophysicists that there are planets gravitationally "herding" the debris into rings, just as Neptune and Jupiter do for our two belts.

"I would describe Fomalhaut as the archetype of debris disks found elsewhere in our galaxy, because it has components similar to those we have in our own planetary system," said András Gáspár of the University of Arizona in Tucson, lead author of the paper, which appeared in Nature Astronomy last week.  "By looking at the patterns in these rings, we can actually start to make a little sketch of what a planetary system ought to look like -- if we could actually take a deep enough picture to see the suspected planets."

"Where Webb really excels is that we're able to physically resolve the thermal glow from dust in those inner regions," said Schuyler Wolff, also of the University of Arizona in Tucson, who co-authored the paper.  "So you can see inner belts that we could never see before.  We definitely didn't expect the more complex structure with the second intermediate belt and then the broader asteroid belt.  That structure is very exciting because any time an astronomer sees a gap and rings in a disk, they say, 'There could be an embedded planet shaping the rings!'"

Or, you know, a Lovecraftian Elder God creating a fire vortex in the eldritch nether regions of the void.  You know how it goes.

In any case, it's incredibly cool to see what's coming in from the JWST.  Here, we're seeing a system that might be a little like what the Solar System looked like four billion years ago, as the planets were coalescing from the rocky debris of the protoplanetary disk.  The astronomers, of course, are going to give it a much closer look.  "The belts around Fomalhaut are kind of a mystery novel: Where are the planets?" said George Rieke, of the JWST's Mid-Infrared Instrument (MIRI) team, who also co-authored.  "I think it's not a very big leap to say there's probably a really interesting planetary system around this star."

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Mystery disk

I'm always fascinated by a good mystery, and that's definitely the appropriate category for an artifact called the Phaistos Disk.

Found in the Minoan palace of Phaistos, on the island of Crete, in 1908, the Phaistos Disk is fifteen centimeters in diameter, made of fired ceramic clay, and (most interestingly) has an inscription on it.  Here's a photograph:

[Image licensed under the Creative Commons C messier, Δίσκος της Φαιστού πλευρά Α 6380, CC BY-SA 4.0]

The Disk is thought to have been made in the second millennium B.C.E., making it approximately contemporaneous with the Linear B script of Crete, which was successfully deciphered in the early 1950s by Alice Kober, Michael Ventris, and John Chadwick.  This accomplishment was the first time that anyone had cracked a script where not only was the sound/letter correspondence unknown, but it wasn't even known what language the script was representing.  (As it turned out, it was an early form of Mycenaean Greek.  Earlier guesses were that it represented Etruscan, a proto-Celtic language, or even Egyptian.  The script itself was mostly syllabic, with one symbol representing a syllable rather than a single sound, and a few ideograms thrown in just to make it more difficult.)

The problem is, the Phaistos Disk is not Linear B.  Nor is it Linear A, an earlier script which remains undeciphered despite linguists' best attempts at decoding it.  The difficulty here is that the Phaistos Disk has only 242 different symbols, which is not enough to facilitate translation.  Some seem to be ideographic, but as you undoubtedly know, many symbols that start out as pictographic end up representing phonetic units, so we can't rely on "it looks like a dog so it means 'dog'."  Once again, we're not sure what the language is, although it's a good guess that it's some form of Greek (other linguists have suggested it might be Hittite or Luwian, both languages spoken in ancient Anatolia (now Turkey), and which had their own alphabet that bears some superficial similarities to the symbols on the Disk).

This lack of information has led to wild speculation.  Various people have claimed it's a prayer, a calendar, a story, a board game, and a geometric theorem, although how the hell you'd know any of that when you can't even begin to read the inscription is beyond me.  But it only gets weirder from there.  Friedhelm Will and Axel Hausmann back in 2002 said that the Disk "comes from the ruins of Atlantis."  Others have suggested it's of extraterrestrial origin.  (Admit it, you knew the aliens were going to show up here somehow.)

Others, more prosaically, think it's a fake.  In 2008 archaeologist Jerome Eisenberg proclaimed the Disk a modern hoax, most likely perpetrated by Luigi Pernier, the Italian archaeologist who claimed to have discovered it.  Eisenberg cites a number of pieces of evidence -- differences in the firing and in how the edges were cut, as compared to other ceramic artifacts from the same period; the fact that it's incredibly well-preserved considering how old it supposedly is; and vague similarities to Linear A and Linear B characters, with various odd ones thrown in (Eisenberg says the symbols were chosen to be "credible but untranslatable" and selected "cleverly... to purposely confuse the scholarly world."

Of course, this didn't settle the controversy.  Archaeologist Pavol Hnila cites four different artifacts, all discovered after the Disk, that have similar characters to the ones on the Disk, and that there is not enough evidence to warrant accusing Pernier and his team of something as serious as a deliberate hoax.

So the mystery endures, as mysteries are wont to do.  I find this fascinating but more than a little frustrating -- to know that there is an answer, but to accept that we may never find out what it is.  That's the way it goes, though.  If you're a true skeptic, you have to be willing to remain in ignorance, indefinitely if need be, if there is insufficient evidence to decide one way or the other.  This leaves the Phaistos Disk in the category of "Wouldn't this be fun to figure out?" -- a designation that is as common in science as it is exasperating.

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The dying of the light

In the brilliant, funny, thought-provoking, and often poignant television series The Good Place, a character named Simone, who is an Australian neuroscientist, ends up in heaven (the titular "Good Place") and flatly refuses to believe it.

The whole thing, she claims, is merely a hallucination cooked up by her dying, oxygen-starved brain.  That she died (or was in the process of it), she could believe; but knowing what she does about neurophysiology, it is simply impossible for her to accept that what she is seeing is real.

The more you know about the brain and its sensory/perceptual system, the easier it is to understand how an actual neuroscientist would come to that conclusion.  As we've seen here at Skeptophilia a good many times, what we perceive is fragmentary and inaccurate, and that's even while we're alive, wide awake, and all the relevant organs are in good working order.  As astrophysicist Neil deGrasse Tyson put it, all too accurately, "The human brain is rife with ways of getting it wrong."

Oh, it works well enough most of the time.  We wouldn't have survived long otherwise.  But to assume that what you're perceiving, and (even worse) what you remember perceiving, is at all complete and accurate is simply false.

It gets even dicier when things start to go wrong.  Which was why I was so fascinated with a study from the University of Michigan that was published a couple of weeks ago in Proceedings of the National Academy of Sciences that looked at EEG traces from comatose patients who had experienced cardiac arrest and died, and the researchers found as the patients died, their brains showed a surge of activity in the regions associated with consciousness and perception.

Gamma wave activity -- associated with awareness -- spiked, as did signaling at the junction of the temporal, occipital, and parietal lobes of the cerebrum.  This area is correlated with dreaming, hallucination, and other altered states of consciousness, and the high activity there might be an explanation for the commonalities in near-death experiences, like the familiar "tunnel of light" that has been reported hundreds of times.

This story was reported in a lot of popular media as providing support for claims that "your life flashes before your eyes" as you die, but that seems to me to be a significant stretch.  For one thing, the study was small; only four individuals, understandable given the specificity of the criteria.  For another, the spike of activity in the temporal-occipital-parietal junction is correlated with altered states of consciousness, but it doesn't tell us what these people were actually experiencing.  And we can't ask them about it, because they're dead.

[Image from Punch, 1858, is in the Public Domain]

So what this says about the experience of dying is in the category of "interesting but very preliminary," and what it says about the possibility of an afterlife is "nothing."  My guess is people who already disbelieve in an afterlife will, like Simone, add this to the evidence against, and the people who already believe in it will add it to the evidence in favor.  In reality, of course, the new study only looks at the threshold of death, not what happens after it occurs.  I'm still agnostic about an afterlife, myself.  I recently read an article written by by Stafford Betty, professor emeritus of religious studies at California State University - Bakersfield, who stated that survival after death was "a near certainty" and that doubters are simply ignoring a mountain of evidence.  "They are so dug into their materialist worldview," Betty writes, "that they refuse to investigate research that contradicts it.  They are afraid of getting entangled in a worldview, often religiously based, that belongs to a past they 'outgrew.'"

Well, maybe.  I've read a lot of the research, and I don't think it's as clear-cut as all that, nor is my skepticism due to my clinging to materialism or a fear of getting trapped in religion.  In fact, I can say without hesitation that if I found out there was an afterlife, I'd be pretty thrilled about it.  (Some afterlifes, anyway.  I'm not so fond of the ones where you're tortured for eternity.  But Valhalla, for example, sounds badass.)  It's more that the evidence I've seen doesn't reach a level of rigor I find convincing.

But I'm certainly open to the idea.  Like I said, the other option, which is simply ceasing to be, isn't super appealing.

Anyhow, the University of Michigan paper is fascinating, and gives us a unique lens into the experience of someone while dying.  It's the one thing that unites us all, isn't it?  We'll all go through it eventually.  It reminds me of the passage from my novel The Communion of Shadows, where the main characters are discussing the fear of death:

“Aren’t you scared?” came T-Joe’s voice from behind him, after a moment’s silence.

“Scared? A little.”  Leandre paused.  “It’s like when I was a child, and I used to climb an oak tree that leaned out over the bayou.  You’re there, hunched on the branch, nothing but the empty air between your naked body and the water’s surface.  It looks like it’s a hundred feet down.  You think, ‘I can’t do it.  I can’t jump.’  Your hands cling to the branch, your heart is pounding, you’re dripping sweat.  You know once you jump it’ll be all right, you’ll swim to shore and in a moment be ready to do it again.  But in that instant, it seems impossible.”  He paused, giving a lazy swat at a mosquito.  “I’m once again that skinny little boy in the tree, looking down at the bayou, and thinking I’ll never have the courage to leap.  I know I can do it, and that it’ll be okay.  Think of all the people who have passed these gates, endured whatever death is and gone on to what awaits us beyond this world.”  He turned around with a broad smile on his face.  “If they can do it, so can I.”

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Resurrecting a fossil

A year ago I wrote about linguistic isolates -- single languages, or small clusters of related languages, that have no apparent relation to any other language on Earth.  The problem, of course, is that being spoken by only a small number of people, these are some of the most endangered languages.  There are many of them for which the last native speakers are already elderly, and there's a high risk of their going extinct without ever being thoroughly studied.

And as I pointed out in my post, the sad part of that is that each one of those is a lens into a specific culture and a particular way of thinking.  Once lost, they're gone forever, or only exist in scattered remnants, like the fossils of extinct animals.  What you can reconstruct from these relics is perhaps better than nothing, but still, there's always an elegiac sense of what we've lost, and what we're still losing.

This topic comes up because of an article in Smithsonian sent to me by a friend and frequent contributor of topics to Skeptophilia, about some linguists who are trying to reconstruct the extinct indigenous Timucuan language of northern Florida.  Timucuan was a linguistic isolate, and seems to be unrelated to the languages spoken by neighboring groups (such as the Seminole, Muscogee, and Choctaw).  The Timucua people, which at the time of European contact in 1595 comprised an estimated 200,000 people in 35 chiefdoms, each of which spoke a different dialect, was decimated by war and by diseases like smallpox.  By 1700, there were only about a thousand Timucuans left, and the slave trade eradicated those few survivors.  There is currently a genetic study to see if some populations in Cuba might be the descendants of the Timucuans, but so far the results are inconclusive.

This would just be another in the long list of complete and irretrievable cultural loss, if it weren't for the efforts of linguists Alejandra Dubcovsky and Aaron Broadwell.  Working with a handful of letters written in Timucuan (using the Latin alphabet), and a rather amazing bilingual document by Spanish missionary Francisco Pareja called Confessions in the Castilian and Timucua Language, With Some Tips to Encourage the Penitent, they have assembled the first Timucuan dictionary and grammar, and reconstructed how a long-gone people spoke.

A page from the Confessions, with Spanish on the left and Timucuan on the right [Image courtesy of the John Carter Brown Library, Brown University]

Which is incredibly cool, but there's also a wryly amusing side to it, because with Dubcovsky's and Broadwell's knowledge of the Timucuan language, they're able to compare what Pareja wanted the translators to say with what they actually did say.  "Our favorite is the description of marriage," Dubcovsky said.  "The Spanish side asks very clearly, 'Have the man and a woman been joined together in front of a priest?'  And the Timucua version of that sentence is, 'Did you and another person consent to be married?'  The Timucua translation not only takes out any mention of gender, but it also removes any mention of a religious officiant.  A priest did not write this, because a priest does not forget to include himself in the story."

So the Confessions document is not only a Rosetta Stone for Timucuan, it gives us a fascinating window into how the Timucuan translators saw the Spanish Catholic culture that was being imposed upon them.

It's tragic that this language and its people were so thoughtlessly (and ruthlessly) eradicated; worse still that such tragedies are all too common.  So it's all the more important that people like Dubcovsky snd Broadwell work to resurrect these extinct languages from the scant fossils they left behind.  It can't ever repair the damage that was done, but at least allows us to glimpse the minds of an extinct culture -- and to honor their memory in whatever way we can.

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Rough neighborhood

In keeping with the stargazing topics that have been our focus this week, today we're going to start with my favorite naked-eye astronomical object: the Pleiades.

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

It's also known as the Seven Sisters; in Greek mythology, the seven brightest stars (about all you can see without a telescope, even if you have good vision) represented the seven daughters of the Titan Atlas and the Oceanid nymph Pleione.  Where I live they're visible in the winter; I love seeing them glittering in the black sky on cold, clear nights.

The Pleiades are mostly hot type-B stars, and the whole group is about 444 light years from Earth, making it one of the closest star clusters.  Stars of this class are so energetic that they have relatively short life spans.  It's estimated that the Pleiades formed about a hundred million years ago from a cloud of gas and dust similar to the Orion Nebula; already the energy output of the individual stars is blowing away the shroud of material from which they were formed, resulting in the halo-like "reflection nebulae" you see surrounding them.

They're also moving away from each other, leaving the "stellar nursery" in which they were born.  In another couple of hundred million years, they will have separated widely enough that future astronomers (assuming there are any around) will have no obvious way to know they started out in the same region of space.  Plus, the biggest and brightest of them will already be approaching the ends of their lives, exploding in the violent cataclysm of a supernova, leaving behind a rapidly-rotating stellar remnant called a neutron star, spinning like a lighthouse beacon to mark the spot where a star died.

The reason all this comes up is some recent research into the composition of the stellar nursery where the Sun formed.  Because it, after all, was born the same way; along with a number of siblings, it coalesced in a massive cloud of hydrogen and helium, with a few heavier elements thrown in as well.  When you look up into the night sky, any of the stars you see could be one of the Sun's sibs.  It's impossible, from where science currently stands, to tell which ones.  They've all undoubtedly traveled a long way away from their point of origin in the 4.6 billion years since they formed.

But the research, which appeared in the Monthly Notices of the Royal Astronomical Society, uncovered a bit more about what our star's stellar nursery was like.  These formations do have some significant differences -- some are small and quiet, with only enough material to form a few stars, while others are enormous and violently active (such as the aforementioned Orion Nebula).  In particular, the models of stellar formation suggest that the two different environments would influence the quantities of heavier elements like aluminum and iron.  By measuring the amounts of these elements in meteorite fragments that are thought to be leftover material from the formation of the Solar System, the researchers concluded that the Sun formed in a high-energy intense environment like the Orion Nebula, swept by gales of dust and hammered by the shock waves of supernovae.

What a sight that would have been.  (From a safe distance.)

So next time you see the Pleiades or Orion's Belt, think about the fact that our calm and stable home star was born in a rough neighborhood.  Lucky for us, it's grown up and settled down a little.  As beautiful as the Pleiades are, I don't think I'd fancy living there.

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