Collision of worlds

Recently I've done posts about exploding lakes and colossal solar storms and places where continents are being torn in two, so it seems fitting to end the week on an appropriately cataclysmic note with the discovery of the remnants of a collision between two giant ice planets.

The coolest part of all of this is that one of the people who first realized something weird was going on was an amateur astronomer named Arttu Sainio, of Järvenpää, Finland (who is listed as an author and credited as "Independent Researcher" in the paper that appeared in Nature this week -- how awesome is that?).  Matthew Kenworthy, of Leiden Observatory, was scouring the data looking for evidence of rings around stars that might be involved in planet formation, which would be indicated by a periodic dimming and brightening of the light from the parent star.  Kenworthy found a candidate -- a sunlike star called ASASSN-21qj, 1,800 light years from Earth -- and posted his find on Twitter, saying, "It's amazing, this star is fading!"  Sainio saw his tweet and responded, "But did you know that it is brightening in the infrared?"

Sainio had been looking at data from NASA's NEOWISE orbiting telescope, and found that nine hundred days before the star had begun dimming, it had shown a strong uptick in the infrared region of the spectrum.  This clued in Kenworthy that his hopes of finding a ring were dashed -- but that maybe there was something even cooler going on here.

He assembled a team of astronomers to analyze the data, including Sainio's peculiar discovery, and they came to the conclusion that the best explanation for the anomalous brightening in the infrared and dimming in the visible light region was the collision of two Neptune-sized planets -- leaving an incandescent cloud of debris orbiting the star which radiated in the infrared as the heat from the collision dissipated, but partially blocked the star's visible light at the same time.

Artist's conception of the planetary collision around ASASSN-21qj [Image courtesy of artist Mark Garlick]

What will happen to the debris cloud next is a matter of speculation, because this is the first time anyone's seen an event like this occur.  While planetary collisions aren't uncommon -- our own Moon, for example, is thought to have formed when a huge protoplanet slammed into the Earth, blowing a blob of molten rock into space that eventually coalesced as the Moon -- no one's ever watched it happen more-or-less in real time.  It's probable that the debris will pull together gravitationally and eventually form one or more planets, but there's no certainty about how long that'll take.

"It will be fascinating to observe further developments," said Zoe Leinhardt, of the University of Bristol, who co-authored the paper.  "Ultimately, the mass of material around the remnant may condense to form a retinue of moons that will orbit around this new planet, but whether that will take ten years or a thousand, we don't yet know."

So a sharp-eyed amateur astronomer tipped off a whole bunch of professional astronomers and astrophysicists to take a closer look at a star that was behaving oddly, and ended up discovering something no one had ever seen happening before.  Just goes to show what a dedicated enthusiast can accomplish.  I've often felt awkward about my lack of credentials in the field I worked in -- I taught biology for over three decades with a bachelor's degree in physics and a master's in historical linguistics -- but I suppose there's nothing wrong with being a deeply curious, passionate-if-uncredentialed amateur.

Dilettantes FTW!

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A sun with no size

When I was in college, the original series Cosmos, hosted by Cornell University astrophysicist Carl Sagan, aired for the first time.

I was absolutely captivated.  I'd been an astronomy buff since middle school.  I was given my own telescope as a birthday present when I was thirteen, and spent many a happy evening in my parents' front yard trying to find the cool-looking astronomical objects I found on the star maps I collected obsessively.  (This is when I first fell in love with the Pleiades -- still my favorite naked-eye star group -- and when I found out that these were recently-created stars, almost fifty times younger than the Sun, I thought that was so cool.  It wasn't until I took an astronomy course in college that I learned how astronomers knew this.)

But when Cosmos came on, it took my interest to a whole new level.  For the time, the special effects and animations were stunning.  The soundtrack was nothing short of brilliant (in fact, it was my first introduction to the music of Dmitri Shostakovich, who has been one of my top three favorite composers ever since).  Sagan's writing and delivery were captivating; like many people who've seen it, if you read quotes from the scripts, you'll hear them in Sagan's unmistakable voice.  I'm not the only one who responded this way; the wildly talented rapper Greydon Square's song "Galaxy Rise" from his album The Mandelbrot Set is a tribute to Sagan and American physicist Michio Kaku.  Square himself majored in physics in college and includes concepts from science in a great many of his songs.

There were a couple of moments, though, that stand out in my memory as being jaw-dropping.  One was the breathtaking animation of colliding galaxies -- all generated from then cutting-edge computer models -- in episode ten, "The Edge of Forever."  But one passage from episode nine, "The Lives of the Stars," impressed me so much that now, forty-two years later, I can very nearly quote it from memory:

There are three ways that stars die.  Their fates are predestined; everything depends on their initial mass.  A typical star with a mass like the Sun will one day continue its collapse until its density becomes very high, and then the contraction is stopped by the mutual repulsion of the overcrowded electrons in its interior.  A collapsing star twice as massive as the Sun isn't stopped by the electron pressure.  It goes on falling in on itself until nuclear forces come into play, and they hold up the weight of the star.  But a collapsing star three times as massive as the sun isn't stopped even by nuclear forces.  There's no force known that can withstand this enormous compression.  And such a star has an astonishing destiny: it continues to collapse until it vanishes utterly.

Each star is described by the force that holds it up against gravity.  A star that's supported by its gas pressure is a normal, run-of-the-mill star like the Sun.  A collapsed star that's held up by electron forces is called a white dwarf.  It's a sun shrunk to the size of the Earth.  A collapsed star supported by nuclear forces is called a neutron star.  It's a sun shrunk to the size of a city. And a star so massive that in its final collapse it disappears altogether is called a black hole.

It's a sun with no size at all.

I can't imagine hearing the last line and not being a little goggle-eyed.

Since Sagan's time, we've learned a great deal more, but by and large, his series still holds up pretty well.  In fact, three years ago astronomers captured the first-ever photograph of a black hole (visible because of the x-ray emission of matter spiraling down toward its event horizon).  And just last week a paper appeared in Physical Review Letters about an event of cataclysmic proportions -- the collision of two black holes.

The collision was detected because of gravitational waves -- ripples in the fabric of spacetime that propagate outward from accelerating masses at the speed of light.  Most gravitational waves are tiny, so it takes huge masses moving really fast to detect them here on Earth; but these were so enormous that they were picked up by two separate detectors (LIGO and Virgo) from 1.2 billion light years away.  Here's artist Aurore Simonnet's conception of what this would have looked like from (much) closer:

It's hard to describe this event without lapsing into superlatives.  One of the most amazing things about it is that apparently, there was an asymmetry in the production of gravitational waves, and that gave a kick to the (larger) black hole produced once they coalesced, because of Newton's Third Law.

Well, "kick" doesn't begin to describe it.  The recoil from this particular gun left the bullet traveling at 0.5% of the speed of light -- about 1,500 kilometers per second.  Imagine the force it would require to propel a mass that large at that speed.  (Remember that Sagan said black holes only form from stars with a minimum mass of three times that of the Sun.  Minimum.  And this was two of them put together.)

So that's our mind-blowing news from astronomy for today.  Even though I have (on some level) known about this stuff for more than four decades, I still can't help being left in awe by the grandeur and beauty of the universe we live in, and by what we continue to add to our body of knowledge about how it works.

I think Carl Sagan would be delighted.

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The imaginary fireball

The subject of today's post isn't anything new; it was just new to me, and, I suspect, will be to a good many of my readers, as well.  I found out about it from a long-time loyal reader of Skeptophilia, who sent me a link about it with a note saying, "Okay, this is interesting. What think you?"

The link was to a 2008 article that appeared in Phys.org entitled, "Cuneiform Clay Tablet Translated for the First Time."   The tablet in question is called the "Sumerian planisphere," and was discovered in the ruins of Nineveh by a British archaeologist named Henry Layard in the middle of the nineteenth century.  From where it was found, it was dated to around 700 B.C.E., and although it was recognized that part of what it contained was maps of constellations, no one was quite sure what it was about.

The Sumerian planisphere [Image is in the Public Domain]

The researchers were puzzled by the fact that the arrangements of the stars in the constellations were close to, but not exactly the same as, the configurations they would have had at the time it was made, but then they concluded that those would have been their positions 2,400 years earlier -- and they claimed the text and maps didn't just show the stars on any old night, but on a sequence of nights chronicling the approach of a comet or asteroid.

Which, ultimately, hit the Earth.

They claim the collision site was near Köfels, Austria, and triggered a five-kilometer-wide fireball.  Why no huge crater, then?  The answer, they say, is that the steep side of the mountain gave way because of the impact, and a landslide ensued.  Organic matter trapped in the debris flow gave an approximate date, but once deciphered, the Sumerian planisphere's detailed sky maps (including the position of the Sun, the timing of sunrise, and so on) supposedly pinpointed the exact day of the impact: the 29th of June, 3123 B.C.E.

Between the planisphere and the geometry of the collision site, the researchers claimed that the comet came in at a very shallow angle -- their estimate is about six degrees -- clipped the nearby peak of Gamskogel, and exploded, creating a five-kilometer-wide moving fireball that finally slammed into Kófels head-on.

You may be wondering why Sumerian astronomers had any particular interest about an impact that occurred almost four thousand kilometers away.  They have an answer for that, too; the shallow impact angle created a sheet of superheated debris that arced away from the impact site, and right toward what is now the Middle East.  A 2014 paper by Joachim Seifert and Frank Lemke concluded that the greatest amount of damage didn't occur right at the collision site, but where all that flaming debris eventually landed -- in Mesopotamia.

"The back plume from the explosion (the mushroom cloud) would be bent over the Mediterranean Sea re-entering the atmosphere over the Levant, Sinai, and Northern Egypt," said Mark Hempsell of the University of Bristol, who is the chief proponent of the Köfels collision hypothesis.  "The ground heating though very short would be enough to ignite any flammable material - including human hair and clothes.  It is probable more people died under the plume than in the Alps due to the impact blast."

The dust and ash from the event caused a hundred-year-long "impact winter" that triggered droughts, leading to a several-centuries-long famine that ultimately caused the collapse of the Akkadian Empire.

Okay, so that's the claim.  There are, unfortunately, a host of problems with it, beginning with those pointed out by the scathing rebuttal by Jeff Medkeff in Blue Collar Scientist.  The first issue is that there is "impact glass" -- vitrified shards of debris partially melted by a collision -- in central Europe, but it dates to much longer ago (certainly more than eight thousand years ago).  There is no impact debris to be found between central Europe and the Middle East anywhere near 3,100 B.C.E., no scorched pottery shards or charred bones that would be indicative of a rain of fire.  An asteroid or comet "clipping" a mountain -- and then generating a plume of debris that was still superheated four thousand kilometers downstream -- would have sheared off the entire mountain top, and there'd be clear evidence of it today.  Last -- and most damning -- the Köfels formation has been studied by geologists and found to be not a single event, but a series of landslides, none of which show convincing evidence of having been triggered by an impact.

The scientists involved don't even seem sure of their own chronology; the Phys.org article says 3123 B.C.E. (the 29th of June, to be exact), while the Seifert and Lemke paper says the impact occurred almost a thousand years later (in 2193 B.C.E.).  The latter date at least is closer to the claimed civilization-destroying effects; the Akkadian Empire fell in around 2154.  It seems likely, though, that the collapse of the Akkadians (and various others, including the Indus Valley Civilization, the Egyptian Old Kingdom, and the Chinese Liangzhu Culture) was due to a drought called the "4.2 Kiloyear Event."  The cause of that is uncertain, but probably wasn't an impact (again, because of the lack of clear stratigraphic evidence).  The most likely culprit was a shift in cold-water currents in the North Atlantic changing patterns of rainfall, but even that is speculative.

As far as Hempsell's even more outlandish claim -- that the Köfels impact generated the story of the destruction of Sodom and Gomorrah -- I won't even go into details except to say that there is evidence of a much smaller airburst explosion where the cities were allegedly located, but once again, it's from a different date (around 1650 B.C.E.).  As for any other evidence of the biblical "Cities on the Plain," it's slim to nonexistent.  Archaeologist Israel Finkelstein, of Tel Aviv University, called the tale of the destruction of Sodom and Gomorrah "an etiological story, that is, a legend that developed in order to explain a landmark.  In other words, people who lived in the later phase of the Iron Age, the later days of the kingdom of Judah, were familiar with the huge ruins of the Early Bronze cities and told a story of how such important places could be destroyed."

So given the (1) lack of any reasonably reliable evidence, (2) a chronology that even the researchers don't seem to be able to keep straight, and (3) plausible alternative explanations for the supposed societal aftereffects, I'm afraid I'm gonna be in the "don't think so" column on this one.  As dramatic as it would be if the astronomers of Sumer documented the approach and ultimate collision of a comet or asteroid, a collision that ultimately showered flaming debris over the entire Middle East, I think we have to set aside the drama of an imaginary fireball for the cold light of reason.

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The rain of glass

A couple of weeks ago I looked at the rather unsettling fact that the seeming benevolence of our home planet is something of an illusion.  As I write this, I'm sitting in a warm house with the calm, clear sunshine sparkling on frost-covered grass, hardly a cloud in the sky, and it's difficult to imagine it ever being any different.  While I don't believe a thoroughly pessimistic outlook helps anything or anyone, it does bear keeping in mind how fragile it all is -- if for no other reason, so that we value what we have.

I started thinking about how quickly and unpredictably a place can go from tranquility to devastation when I ran across a paper that appeared in the journal Geology two weeks ago.  In it, I learned about something I'd never heard about -- a seventy-five-kilometer-wide patch of the Atacama Desert in northern Chile that is covered with shards of black and green glass.

The Atacama Desert is a strange place in and of itself.  Other than the dry valleys of Antarctica, it is far and away the most arid place on Earth; the average rainfall is around fifteen millimeters per year, and there are parts of it that are down in the nearly-unmeasurable range of one to three millimeters.  The few plants and animals that live there have dry-climate adaptations that beggar belief; they get most of the water they need using condensation from fog.  The reason for the peculiar climate is a combination of a more-or-less permanent temperature inversion produced by the South Pacific Anticyclone and the cold, northward-flowing Humboldt Current, combined with a two-sided rain shadow caused by the parallel Andes Mountains and Chilean Coast Range.  It's so dry and barren that it was used by NASA as one of the places to test the Mars Lander's ability to detect the presence of microscopic life.

The aridity is what allowed for the discovery that was the subject of the November 2 paper.  Geologists Peter Schultz (Brown University), R. Scott Harris (Fernbank Science Center), Sebastián Perroud (Universidad Santo Tomás), and Nicolas Blanco and Andrew Tomlinson (Servicio Nacional de Geología y Minería de Chile) analyzed the peculiar shards that cover the patch on the northern end of the desert, and found out that they were all formed in one event -- the mid-air explosion of a comet about twelve thousand years ago.

The authors write:

Twisted and folded silicate glasses (up to 50 cm across) concentrated in certain areas across the Atacama Desert near Pica (northern Chile) indicate nearly simultaneous (seconds to minutes) intense airbursts close to Earth’s surface near the end of the Pleistocene.  The evidence includes mineral decompositions that require ultrahigh temperatures, dynamic modes of emplacement for the glasses, and entrained meteoritic dust.  Thousands of identical meteoritic grains trapped in these glasses show compositions and assemblages that resemble those found exclusively in comets and CI group primitive chondrites.  Combined with the broad distribution of the glasses, the Pica glasses provide the first clear evidence for a cometary body (or bodies) exploding at a low altitude.  This occurred soon after the arrival of proto-Archaic hunter-gatherers and around the time of rapid climate change in the Southern Hemisphere.

The dry climate is why we even know about this event.  Cometary collisions almost never leave a crater; given that comets are mostly made of various kinds of ice, the heat of friction from the atmosphere causes them to evaporate and finally explode, creating an airburst but no solid-object impact.  The airburst can be devastating enough, of course.  The 1908 Tunguska Event, the largest such occurrence in recorded history, flattened eighty thousand trees in over two thousand square kilometers of Siberian forest, and registered on seismographs all the way around the world in Washington, D.C.  If Tunguska had happened over a major city, there wouldn't have been a person left alive or a building left standing in the blast zone.

Like Tunguska, at the time and place of the Atacama airburst, there weren't many people in the danger zone.  There was, however, a lot of sand, and the heat from the collision melted it into glass -- indicating temperatures in excess of 1,700 C.  In a climate with ordinary amounts of rainfall, the glass would have been degraded and eroded, but here, it rained out of the sky and then has just kind of sat there for the intervening twelve thousand years.

"It was clear the glass had been thrown around and rolled," study lead author Peter Schultz said, in an interview with Science News.  "It was basically kneaded like bread dough."

The glass shards (the dark bits) in the northern Atacama Desert [photograph by Peter Schultz]

It would have been quite a spectacular thing to witness (from a safe distance), and you have to wonder how the survivors explained it.  "It would have seemed like the entire horizon was on fire," Schultz said. "If you weren’t religious before, you would be after."

So that's our disquieting scientific research for the day.  The reassuring news is that we've gotten pretty skilled at mapping the asteroids, meteors, and comets out there in the Solar System, and none of them seem to be headed our way, at least not for a good long while.  Which is a bit of a relief.  As often as I complain about how dull it is to live in a part of the world where the biggest excitement of the day is when the farmer across the road lets his cows out into the field, this isn't the kind of change of pace I'm really looking for.

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If Monday's post, about the apparent unpredictability of the eruption of the Earth's volcanoes, freaked you out, you should read Robin George Andrews's wonderful new book Super Volcanoes: What They Reveal About the Earth and the Worlds Beyond.

Andrews, a science journalist and trained volcanologist, went all over the world interviewing researchers on the cutting edge of the science of volcanoes -- including those that occur not only here on Earth, but on the Moon, Mars, Venus, and elsewhere.  The book is fascinating enough just from the human aspect of the personalities involved in doing primary research, but looks at a topic it's hard to imagine anyone not being curious about; the restless nature of geology that has generated such catastrophic events as the Yellowstone Supereruptions.

Andrews does a great job not only demystifying what's going on inside volcanoes and faults, but informing us how little we know (especially in the sections on the Moon and Mars, which have extinct volcanoes scientists have yet to completely explain).  Along the way we get the message, "Will all you people just calm down a little?", particularly aimed at the purveyors of hype who have for years made wild claims about the likelihood of an eruption at Yellowstone occurring soon (turns out it's very low) and the chances of a supereruption somewhere causing massive climate change and wiping out humanity (not coincidentally, also very low).

Volcanoes, Andrews says, are awesome, powerful, and fascinating, but if you have a modicum of good sense, nothing to fret about.  And his book is a brilliant look at the natural process that created a great deal of the geology of the Earth and our neighbor planets -- plate tectonics.  If you are interested in geology or just like a wonderful and engrossing book, you should put Super Volcanoes on your to-read list.

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

All that glitters

If you own anything made of gold, take a look at it now.

I'm looking at my wedding ring, made of three narrow interlocked gold bands.   It's a little scratched up after almost eighteen years, but still shines.

Have you ever wondered where gold comes from?  Not just "a gold mine," but before that.  If you know a little bit of physics, it's kind of weird that the periodic table doesn't end at 26.  The reason is a subtle but fascinating one, and has to do with the binding energy curve.

The vertical axis is a measure of how tightly the atom's nucleus is held together.  More specifically, it's the amount of energy (in millions of electron-volts) that it would take to completely disassemble the nucleus into its component protons and neutrons.  From hydrogen (atomic number = 1) up to iron (atomic number = 26), there is a relatively steady increase in binding energy.  So in that part of the graph, fusion is an energy-releasing process (moves upward on the graph) and fission is an energy-consuming process (moves downward on the graph).  This, in fact, is what powers the Sun; going from hydrogen to helium is a jump of seven million electron-volts per proton or neutron, and that energy release is what produces the light and heat that keeps us all alive.

After iron, though -- specifically after an isotope of iron, Fe-56, with 26 protons and 30 neutrons -- there's a slow downward slope in the graph.  So after iron, the situation is reversed; fusion would consume energy, and fission would release it.  This is why the fission of uranium-235 generates energy, which is how a nuclear power plant works.

It does generate a question, though.  If fusion in stars is energetically favorable, increasing stability and releasing energy, up to but not past iron -- how do the heavier elements form in the first place?  Going from iron to anywhere would require a consumption of energy, meaning those will not be spontaneous reactions.  They need a (powerful) energy driver.  And yet, some higher-atomic-number elements are quite common -- zinc, iodine, and lead come to mind.

Well, it turns out that there are two ways this can happen, and they both require a humongous energy source.  Like, one that makes the core of the Sun look like a wet firecracker.  Those are supernova explosions, and neutron star collisions.  And just last week, two astrophysicists -- Szabolcs Marka of Columbia University and Imre Bartos of the University of Florida -- found evidence that the heavy elements on the Earth were produced in a collision between two neutron stars, on the order of a hundred million years before the Solar System formed.

This is an event of staggering magnitude.  "If you look up at the sky and you see a neutron-star merger 1,000 light-years away," Marka said, "it would outshine the entire night sky."

What apparently happens is when two neutron stars -- the ridiculously dense remnants of massive stellar cores -- run into each other, it is such a high-energy event that even thermodynamically unfavorable (energy-consuming) reactions can pick up enough energy from the surroundings to occur.  Then some of the debris blasted away from the collision gets incorporated into forming stars and planets -- and here we are, with tons of lightweight elements, but a surprisingly high amount of heavier ones, too.

But how do they know it wasn't a nearby supernova?  Those are far more common in the universe than neutron star collisions.  Well, the theoretical yield of heavy elements is known for each, and the composition of the Solar System is far more consistent with a neutron star collision than with a supernova.  And as for the timing, a chunk of the heavy isotopes produced are naturally unstable, so decaying into lighter nuclei is favored (which is why heavy elements are often radioactive; the products of decay are higher on the binding energy curve than the original element was).  Since this happens at a set rate -- most often calculated as a half-life -- radioactive isotopes act like a nuclear stopwatch, analogous to the way radioisotope decay is used to calculate the ages of artifacts, fossils, and rocks.  Backtracking that stopwatch to t = 0 gives an origin of about 4.7 billion years ago, or a hundred million years before the Solar System coalesced.

So next time you look at anything made of heavier elements -- gold or silver or platinum, or (more prosaically) the zinc plating on a galvanized steel pipe -- ponder for a moment that it was formed in a catastrophically huge collision between two neutron stars, an event that released more energy in a few seconds than the Sun will produce over its entire lifetime.  Sometimes the most ordinary things have a truly extraordinary origin -- something that never fails to fascinate me.

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In the midst of a pandemic, it's easy to fall into one of two errors -- to lose focus on the other problems we're facing, and to decide it's all hopeless and give up.  Both are dangerous mistakes.  We have a great many issues to deal with besides stemming the spread and impact of COVID-19, but humanity will weather this and the other hurdles we have ahead.  This is no time for pessimism, much less nihilism.

That's one of the main gists in Yuval Noah Harari's recent book 21 Lessons for the 21st Century.  He takes a good hard look at some of our biggest concerns -- terrorism, climate change, privacy, homelessness/poverty, even the development of artificial intelligence and how that might impact our lives -- and while he's not such a Pollyanna that he proposes instant solutions for any of them, he looks at how each might be managed, both in terms of combatting the problem itself and changing our own posture toward it.

It's a fascinating book, and worth reading to brace us up against the naysayers who would have you believe it's all hopeless.  While I don't think anyone would call Harari's book a panacea, at least it's the start of a discussion we should be having at all levels, not only in our personal lives, but in the highest offices of government.

Revising Hubble

If I had to pick the most paradigm-changing discovery of the twentieth century, a strong contender would be the discovery of red shift by astronomer Edwin Hubble.

What Hubble found was that when he analyzed the spectral lines from stars in distant galaxies, the lines -- representing wavelengths of light emitted by elements in the stars' atmospheres -- had slid toward the red (longer-wavelength) end of the spectrum.  Hubble realized that this meant that the galaxies were receding from us at fantastic speeds, resulting in a Doppler shift of the light coming from them.

What was most startling, though, is that the further away a galaxy was, the faster it was moving.  This observation led directly to the theory of the Big Bang, that originally all matter in the universe was coalesced into a single point, then -- for reasons still unclear -- began to expand outward at a rate that defies comprehension.

There's a simple quantity (well, simple to define, anyhow) that describes the relationship that Hubble discovered.  It's called the Hubble constant, and is defined at the ratio between the velocity of a galaxy and its distance from us.  The relationship seems to be linear (meaning the constant isn't itself dependent upon distance), but the exact value has proven extremely difficult to determine.  Measurements have varied between 50 and 500 kilometers per second per megaparsec, which is a hell of a range for something that's supposed to be a constant.

And the problem is, the value has varied depending on how it's calculated.  Measurements based upon the cosmic microwave background radiation give one range of values; measurements using Type 1A supernovae (a commonly-used "standard candle" for calculating the distances to galaxies) give a different range.

Enter Kenta Hotokezaka of Princeton University, who has decided to tackle this problem head-on.  “The Hubble constant is one of the most fundamental pieces of information that describes the state of the universe in the past, present and future," Hotokezaka said in a press release.  "So we’d like to know what its value is...  either one of [the accepted calculations of the constant] is incorrect, or the models of the physics which underpin them are wrong.  We’d like to know what is really happening in the universe, so we need a third, independent check."

Hotokezaka and his team have found the check they were looking for in the collision of two neutron stars in a distant galaxy.  The measurements made of the gravitational waves emitted by this collision were so precise it kind of boggles the mind.  Adam Deller, of Swinburne University of Technology in Australia, who co-authored the paper, said, "The resolution of the radio images we made was so high, if it was an optical camera, it could see individual hairs on someone’s head 3 miles away."

[Image licensed under the Creative Commons ESA, Colliding neutron stars ESA385307, CC BY-SA 3.0 IGO]

Using this information, the researchers were able to narrow in on the Hubble constant -- reducing the uncertainty to between 65.3 and 75.6 kilometers per second per megaparsec.

Quite an improvement over 50 to 500, isn't it?

"This is the first time that astronomers have been able to measure the Hubble constant by using a joint analysis of a gravitational-wave signals and radio images,"  Hotokezaka said about the accomplishment of his team.  "It is remarkable that only a single merger event allows us to measure the Hubble constant with a high precision — and this approach relies neither on the cosmological model (Planck) nor the cosmic-distance ladder (Type Ia)."

I'm constantly astonished by what we can learn of our universe as we sit here, stuck on this little ball of spinning rock around an average star in one arm of an average galaxy.  It's a considerable credit to our ingenuity, persistence, and creativity, isn't it?  From our vantage point, we're able to gain an understanding of the behavior of the most distant objects in the universe -- and from that, deduce how everything began.

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This week's Skeptophilia book recommendation is pure fun for anyone who (like me) appreciates both plants and an occasional nice cocktail -- The Drunken Botanist by Amy Stewart.  Most of the things we drink (both alcohol-containing and not) come from plants, and Stewart takes a look at some of the plants that have provided us with bar staples -- from the obvious, like grapes (wine), barley (beer), and agave (tequila), to the obscure, like gentian (angostura bitters) and hyssop (Bénédictine).

It's not a scientific tome, more a bit of light reading for anyone who wants to know more about what they're imbibing.  So learn a little about what's behind the bar -- and along the way, a little history and botany as well.

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

Life out of catastrophe

After yesterday's post about mysterious explosions in distant galaxies, today I want to look at a colossal explosion that happened much, much closer to home -- and may have jump-started life on Earth.

In a paper by Steven Benner of the Foundation for Applied Molecular Evolution in Alachua, Florida, presented at a conference last fall in Atlanta, we find out that there's geological evidence that early in Earth's history, there may have been a collision with an enormous object -- by some estimates, the size of the Moon -- that drastically altered the atmosphere.  4.47 billion years ago, only sixty million years after the Earth coalesced from the ring of planetary debris where it originated, it was struck so hard by planetoid that water molecules were ripped apart into oxygen and hydrogen, and superheated metallic debris was flung into the air and generated a torrential rain of molten iron.

Artist's conception of what the collision might have looked like from space

As the atmosphere (and everything else) cooled, the highly reactive oxygen bound to the iron, forming a thick layer of iron (and other metal) oxides that explains their prevalence in the Earth's crust today.  More interesting still is that the collision left behind the hydrogen in the atmosphere.  This created what is called a reducing atmosphere -- a collection of gases with an abundance of free electrons, essentially the opposite of what we have today (an oxidizing atmosphere, where oxygen and other electronegative elements mop up any available electrons, making organic matter and other reduced compounds fall apart).

The reducing atmosphere, Benner says, stuck around for two hundred million years, and it was during this time that the first organic compounds were formed.  This lines up neatly with the famous Miller-Urey experiment, where biochemists Stanley Miller and Harold Urey of the University of Chicago showed back in 1952 that in the presence of reducing gases and a source of energy, organic compounds formed readily, including DNA and RNA nitrogenous bases, amino acids, and simple sugars.

Benner believes that the critical one was RNA.  RNA is (as far as we know) unique in that it can not only replicate itself, it's autocatalytic -- it can catalyze its own reactions.  This pull-yourself-up-by-your-shoelaces ability is why a lot of scientists believe that the first genetic material was RNA, not the (currently) more ubiquitous DNA.  And Benner's theory about how the reducing atmosphere was generated explains not only how the building blocks of RNA could have formed, but why the Earth's atmosphere was reducing in the first place.

Benner believes the key is a set of biochemical reactions that involves repeated wetting and drying, along with interaction of the oxygen-free atmosphere with sulfur-containing gases released from volcanic eruptions.  He has demonstrated that in these conditions, formaldehyde -- CH₂O, one of the simplest organic compounds, would form "by the metric ton."  From there, reactions with the sulfur-bearing gases produced hydroxymethanesulfonate, which reacts readily to form glyceraldehyde (a simple sugar) and the four bases of RNA, adenine, cytosine, guanine, and uracil.

Once that happens, the autocatalytic ability of RNA means you're off to the races.  As Richard Dawkins pointed out in his tour-de-force The Blind Watchmaker, if you have two things -- an imperfect replicator, and a selecting mechanism -- you can generate order from disorder in the blink of an eye.  "[M]any experiments have confirmed that once RNA chains begin to grow, they can swap RNA letters and even whole sections with other strands, building complexity, variation, and new chemical functions," said science journalist Robert F. Service, writing for Science magazine.  "[T]he impact scenario implies organic molecules, and possibly RNA and life, could have originated several hundred million years earlier than thought.  That would allow plenty of time for complex cellular life to evolve by the time it shows up in the fossil record at 3.43 billion years ago."

This research not only confirms what Miller and Urey showed in their landmark experiment 67 years ago, but lines up beautifully with what is known from studies by geologists of the earliest rocks.  As for Benner, he's ready to put aside any doubt.  When Ramon Brasser, paleogeologist at the Tokyo Institute of Technology, laid out a timeline of the early Earth in his talk at the Atlanta conference, Benner asked him when the atmosphere would have likely dropped below a temperature of 100 C, the boiling point of water.  Brasser indicated a point about fifty million years after the impact with the planetoid.

"That's it, then!" Benner said excitedly, pointing to a spot at about 4.35 billion years ago on the timeline.  "Now we know exactly when RNA emerged. It's there—give or take a few million years."

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This week's Skeptophilia book recommendation is a little on the dark side.

The Radium Girls, by Kate Moore, tells the story of how the element radium -- discovered in 1898 by Pierre and Marie Curie -- went from being the early 20th century's miracle cure, put in everything from jockstraps to toothpaste, to being recognized as a deadly poison and carcinogen.  At first, it was innocent enough, if scarily unscientific.  The stuff gives off a beautiful greenish glow in the dark; how could that be dangerous?  But then the girls who worked in the factories of Radium Luminous Materials Corporation, which processed most of the radium-laced paints and dyes that were used not only in the crazy commodities I mentioned but in glow-in-the-dark clock and watch dials, started falling ill.  Their hair fell out, their bones ached... and they died.

But capitalism being what it is, the owners of the company couldn't, or wouldn't, consider the possibility that their precious element was what was causing the problem.  It didn't help that the girls themselves were mostly poor, not to mention the fact that back then, women's voices were routinely ignored in just about every realm.  Eventually it was stopped, and radium only processed by people using significant protective equipment,  but only after the deaths of hundreds of young women.

The story is fascinating and horrifying.  Moore's prose is captivating -- and if you don't feel enraged while you're reading it, you have a heart of stone.

[If you purchase the book from Amazon using the image/link below, part of the proceeds goes to supporting Skeptophilia!]

Weighty matters

Despite all of the daily litany of depressing and/or fury-inducing news, I'm pleased to say that the scientists are still hard at work showing us more of the internal workings of the universe, giving us better insights into the nature of the cosmos even as most of the rest of us focus on the minuscule doings of one species on a tiny planet around a completely ordinary star in the edge of a spiral galaxy that is one amongst billions.

Not to denigrate my fellow humans, of course.  I rather like being human, and I'm awfully fond of the little floating green-and-blue sphere where I live.  But it's nice to know that while we focus on our petty concerns, we have people who are looking outward, not downward.

The discovery I'm referencing is the observation by LIGO (the Laser Interferometer Gravitational-wave Observatory) of the collision of two neutron stars.  Neutron stars are the phenomenally dense cores of exploded giant stars; their matter is so compressed that, in the famous comparison, one teaspoon of neutron star-stuff would weigh as much as Mount Everest.

What is stunning about this observation isn't just the thought of what it would be like to see two such dense objects collide; in fact, the collision itself is just part of what's fascinating about this event.  Other amazing features are:

• In the moments before the collision occurred, the two stars were circling their center of mass at a rate of a thousand times per second.
• The collision not only created gravitational waves and a burst of light across the spectrum, it's thought that such events are what create a lot of the heavy elements in the periodic table.  So yes: the gold in your ring was very likely formed in a cosmic cataclysm.
• It is possible that the combined mass of the two stars exceeded the mass limit for a neutron star, and after the collision the stars immediately vanished -- became a black hole.  That point isn't settled yet.

The coolest part of all of this, however, is that the light and the gravitational waves from the collision arrived at detectors at the same moment -- showing that gravitational waves do indeed travel at the speed of light, which is one of the predictions of the General Theory of Relativity.  Put simply: Einstein wins again.  

If that doesn't put relativity into the "proven beyond a shadow of a doubt" column, I don't know what would.

The result was a flurry of papers being published, including one in Astrophysical Journal Letters that had 4,500 authors from 910 different institutions -- which surely must be some kind of record.

Daniel Holz, astrophysicist at the University of Chicago, who worked on the LIGO project, said, "I can't think of a similar situation in the field of science in my lifetime, where a single event provides so many staggering insights about our universe."

So maybe it's time to take a step back from the dreary ongoing march of political news and think a little bit more about the bigger picture.  I mean, the really big picture.  The one that encompasses the entire universe in which we live.  And now, because of a cataclysmic event 130 million light years away, one piece of which we are now able to view with greater clarity and understanding.

Orange dwarf catastrophe

It's no great insight that the media likes sensationalized stories, and that a lot of them (including, sadly, some major news outlets) have the attitude that facts don't matter much as long as they can keep readers reading.

What is more frustrating is the way the readers themselves become complicit in this dissemination of bullshit.  Now that we have the interwebz, sending along ridiculous "news" stories takes only a click. And before you know it, you have people believing that humanity is going to be wiped out because the Solar System is going to be destroyed during a collision with an orange dwarf star.

The original study, by astronomer Coryn Bailer-Jones of the Max Planck Institute for Astronomy in Heidelberg, is interesting enough.  Astronomers have long known that the stars move relative to each other; this means that the constellations aren't fixed, and that millions of years from now, a time traveler from today wouldn't recognize any of the current star patterns.  (I still remember my first encounter with this idea, on Carl Sagan's Cosmos, when I was a freshman in college.  Seeing the animation of the movements of the stars in the Big Dipper was one of those moments when I realized, "I really want to know more about science!")

So it's not too surprising that some stars will get closer to the Sun over time.  And Bailer-Jones found that two orange dwarf stars are predicted to make relatively close approaches -- HIP 85605 could get as close as 0.13 light years, and GL 710 could make a pass of 0.32 light years.

[image courtesy of the Wikimedia Commons]

Cool stuff.  But the media, unfortunately, is not content simply to report the facts.  Because that, somehow, would be boring.  This research has been picked up by a number of different online news sources, and one and all, they focus on the fact that this "close pass" might wipe us all out by gravitationally dislodging comets from the Oort Cloud, resulting in a "rain of comets," some of which could, perhaps, collide with the Earth.

Notice how many times I said "could" and "might" in the previous two paragraphs?  Bailer-Jones is up front about her study being speculative; the upper bounds for the pass distance of the two stars are 0.65 light years and 1.44 light years, respectively.  To put things in perspective; the closest estimate of HIP 85605 to the Sun was 0.13 light years, right?  Well, Pluto is 13 light hours from the Sun.  So this means that even at its closest, HIP 85605 will be 9,000 times further away than Pluto.

Next, let's consider the likelihood of a disruption of comets leading to a "rain of comets" and the certainty of a devastating Earth strike.  Let's assume that we do have a bunch of comets swooping inwards from the near pass of these stars.  What kind of target does Earth represent?

The issue here is scale, of course, and the amount of the Solar System that is (virtually) empty space. The best analogy I have run across is that if you shrank the entire Solar System down to a circle with a radius of 1,000 meters, with the orbit of Pluto as its perimeter, then the Earth would be about 7 meters from the center.

And it would be the size of a peppercorn.

So it's not exactly a huge target.  Yes, a comet or two could strike the Earth, as they have repeatedly during Earth's history.  No, it would not cause a rain of death.

But those aren't the only misrepresentations in the "news" story.  Not only has Bailer-Jones's research been sensationalized, it's had information added to it that is outright false.  In the above-linked story, which is no worse than the various other versions I've seen (i.e., I didn't pick this one because it was especially bad; they were all bad), here are some direct quotes, with commentary:

Apparently, the comets are made of rocks, dust and organic materials.

Actually, comets are mostly ice, a fact which has been known for decades and would have been immediately apparent had the author bothered to consult Wikipedia.

(T)he gravity [of the stars] can attract comets into the inner solar system and the passing comets might harshly affect Earth's atmosphere due to the powerful ultraviolet radiation that the comets might cause.

Ultraviolet radiation from what source, pray?  Comets aren't giant orbiting tanning lamps, for fuck's sake.

(A) small number of the alleged stars might explode like supernova while passing through the Oort Cloud.

Oh noes!  Not alleged stars explode like supernova!  That sound bad!

The Hip 85605 might reach the solar system in 0.13 to 0.65 light years away, while the GL 710 might take around 0.32 to 1.44 light years.

Ninth graders in Earth Science learn that a light year is a measure of distance, not time, a point that seems to have escaped the author, making me wonder how he ever got chosen to write a science story.  To be fair, unit confusion also plagued the writers of Star Wars, wherein we famously had Han Solo boasting that the Millennium Falcon had done the Kessel Run in "less than twelve parsecs," which would be like saying that your car was so fast that you went to the grocery store in less than five miles.  (Of course, there are Star Wars apologists who have talked themselves into thinking that the scriptwriters had some kind of fancy time-travel space-warp relativity thing in mind when they wrote it.  Myself, I think they just didn't know what a parsec is.)

And of course, it's only midway through the article that we find out when this catastrophe is predicted to happen:

1.3 million years from now.

So, to boil it all down:

Two small stars might, or might not, pass 9,000 times further away from the Sun than Pluto is, some millions of years in the future.  This could increase the number of comets entering the inner Solar System, generating a somewhat higher likelihood of a comet striking Earth.

But that version of the story wouldn't have induced so many people to read it and pass it along, would it?  Nope.  So they add sensationalized nonsense to it, so as to make it better clickbait.

At least it's still better than the post I saw on social media yesterday, wherein someone asked for help for a school project their child is doing regarding why the stars were created.  The responses included that god had made them "to rule the night with the moon," "to be for signs, and for seasons, and for days, and years," and "to declare god's glory."  The scholarly references given were the Book of Genesis and Psalm 19.

But hey, if you're going to buy into non-science, I guess you should go all the way, right?