Cold snap

After the warmest fall I can remember, we here in upstate New York finally are seeing cooler weather.  I greet this with mixed feelings.  As I've pointed out here many times, the abnormally warm temperatures we've had in the last few years are not good news.  On the other hand, being a transplanted southerner, I can't say I'm fond of the cold, even after forty years of living in higher latitudes.

Our chilly winters, though, are nothing compared to a lot of other places.  My Canadian friends, even the ones who live in the southern parts of that vast country, see cold temperatures the likes of which I've never had to deal with.  The Rocky Mountain region, from Colorado up into Alberta, drops down to dangerous lows, often coupled with howling winds and snow.  Scandinavia, Siberia, Greenland... there are a lot of places on Earth where the cold season is actively trying to kill you.  The lowest temperature ever recorded on the surface of the Earth was -89.2 C, at Vostok Station, Antarctica, cold enough to freeze carbon dioxide into dry ice.

Makes our current 2 C seems like a gentle spring zephyr.

But I wonder if you've ever considered how much colder it can get?

Temperature is a measure of the average molecular motion of a substance.  It is connected to, but not the same as, the heat energy; to prove that to yourself, put a pot of water on the stove and bring it to boil, and set your oven to 212 F/100C, and then decide which one would be less fun to stick your hand into.  The water and the air in the stove are exactly the same temperature -- i.e., the molecules are moving at the same average speed -- but the water has a great deal more heat energy, because water molecules are so much harder to get moving than air molecules are. 

So logically, there's a minimum temperature; absolute zero, where all molecular motion stops.  This would occur at -273.15 C (0 on the Kelvin scale), but practically speaking, it's impossible to get there.  Even if you could somehow extract all the heat energy from a substance, there's still the kinetic energy of the ground states of the atoms that can't be removed.  Still, the scientists have gotten pretty damn close.  The CUORE laboratory in Italy set a record in 2014, reaching a temperature of 0.006 K, but recently that's been broken on extremely small scales -- two years ago scientists working with an exotic form of matter called a Bose-Einstein condensate got it down to 38 picokelvin -- that's 0.000000000038 degrees above absolute zero.

But that, of course, is all done in a lab setting.  What's the lowest naturally-occurring temperature ever measured?

You might think it's somewhere in deep space, but it's not.  The temperature in deep space varies all over the place; recall that what matters is the average velocity of the atoms in an area, not how much heat energy the region contains.  (The solar corona, for example, can reach temperatures of a million K, which is way higher than the Sun's surface -- there aren't many atoms out there, but the ones there are move like a bat out of hell.)

The coldest known place in the universe, outside of labs down here on Earth, is the Boomerang Nebula, a planetary nebula in the constellation of Centaurus, which has measured temperatures of around 1 K.  The reason why is weird and fascinating.

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

A planetary nebula forms when a red giant star runs out of fuel, and the collapse of the core raises the temperatures to a ridiculously high one million degrees kelvin.  This sudden flare-up blows away the outer atmosphere of the star, dissipating it out into space, and leaves the exposed core as a white-hot white dwarf star, which will then slowly cool over billions of years.

So how could a flare-up of something that hot trigger temperatures that cold?  What's amazing is that it's the same process that heated up the core, but in reverse -- adiabatic heating and cooling.

Way back in 1780, French scientist Jacques Charles discovered that when you compress a gas (reduce its volume), it heats up, and when you allow a gas to expand (increase its volume), it cools.  Volume and temperature turned out to be inversely proportional to each other, something we now call Charles's Law in his honor.  If you've ever noticed that a bicycle pump heats up when you inflate your tire, you've seen Charles's Law in action.

This all happens because upon compression, the mechanical work of reducing the volume adds kinetic energy to the gas (increasing its temperature); when a gas expands, the opposite occurs, and the temperature falls.  This is how compressors in air conditioners and refrigerators work -- the compression of the coolant gas increases its temperature, and the warmed gas is passed through coils where the heat dissipates.  Then it's allowed to expand suddenly, reducing its temperature enough to cool the interior of a freezer compartment to below zero C.

This is what's happening in the Boomerang Nebula, but on a much larger scale.  The outer atmosphere of the star is expanding so fast its temperature has dropped to just one degree above absolute zero -- making this peculiar nebula five thousand light years away the coldest spot in the known universe.

So that's our tour of places you wouldn't want to vacation.  Top of the list: the Boomerang Nebula.  Might be pretty to look at, but from a long way away, and preferably while warmly dressed.

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Relics of a lost planet

It took astronomers a good long while to figure out how the Moon formed.

Some initial working models were found, upon analysis to... well, not work.  One early idea was that what is now the Moon sheared away from the Earth while it was molten because of centrifugal force, but the viscosity of molten rock is too high (or the rotational speed of the Earth is way too low) for that to be feasible.  Another possibility was the gravitational capture of a pre-formed body, but that makes it hard to explain the Moon's nearly perfect circular orbit.  (Captured objects -- a likely candidate is Neptune's moon Nereid -- tend to have highly elliptical orbits and/or orbits not parallel to their host planet's rotation, because there's no reason to suppose that their capture occurred at any particular angle.)

A big clue came from isotopic analysis of lunar rocks, which found that the ratios of isotopes for several different elements were nearly identical to terrestrial rocks, arguing for a common source.  The prevailing theory is that the Moon formed when, about 4.5 billion years ago, the proto-Earth was struck by a Mars-sized planet -- named Theia, after the Greek Titan who was the mother of Selene, the goddess of the Moon -- which caused a blob of material to shear away, propelling it into orbit where it coalesced into what we see today on a clear night.

Artist's depiction of the collision between Theia and the proto-Earth [Image is in the Public Domain courtesy of NASA/JPL]

The reason the topic comes up is because of a paper that appeared this week in Nature that I found out about from a friend and loyal reader of Skeptophilia.  A team led by geophysicist Qian Yuan of Arizona State University took a look at two large low-velocity provinces (LLVPs) in the Earth's lower mantle -- dense regions where seismic waves slow down, and which are hypothesized to have a significantly higher iron oxide content than the rest of the mantle -- and their models support the astonishing idea that these are the remnants of Theia.

It's wild that there are still relics discernible, between the violence of the collision and the fact that 4.5 billion years have passed since it happened.  You'd think this would be plenty enough time to stir the mantle and homogenize the material Theia brought in with whatever was present in the proto-Earth.  But Yuan et al. think that the collision's energy was mostly dissipated into the upper mantle, allowing the remnants of Theia's core to sink into the lower mantle without mixing completely -- where the pieces are still detectable today.

Like all good science, the Yuan et al. paper raises some interesting questions, such as what effect the collision had on the rest of Earth's evolution.  "A logical consequence of the idea that the LLVPs are remnants of Theia is that they are very ancient," said Paul Asimow, of the California Institute of Technology and senior author of the paper, in an interview with Science Daily.  "It makes sense, therefore, to investigate next what consequences they had for Earth's earliest evolution, such as the onset of subduction before conditions were suitable for modern-style plate tectonics, the formation of the first continents, and the origin of the very oldest surviving terrestrial minerals."

So that's today's cool scientific research, which I can say without fear of contradiction is pretty close to earthshattering.  Think about that next time you see our companion's ghostly white light in the night sky -- that despite its tranquil appearance, it may well have been born from a collision of almost unimaginable violence, billions of years ago.

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Analysis of a monster

In my post a couple of days ago about the unstable geology of the Greek island of Thera, I stated that this is far from the only place in the world where lots of people live in harm's way from the vagaries of plate tectonics.  I mentioned the Cascadia Subduction Zone, off the coast of the Pacific Northwest, and included a link to the rather desultory post I'd made a while back about what's going on over there.  A loyal reader of Skeptophilia wondered if I might write a more thorough piece about the terrifying situation looming in that beautiful part of the world, so here I am to elaborate, and probably to scare the absolute shit out of anyone living in coastal British Columbia, Washington, Oregon, and northern California.

Even after the general acceptance of plate tectonics by geologists in the 1960s and 1970s, it took a long time for them to see what was happening in the northeastern Pacific.  The presence of a ridge (divergent zone) meant that the seafloor was spreading on both sides; the fact that the small Explorer, Juan de Fuca, and Gorda Plates were being shoved eastward meant that there had to be a trench somewhere between the ridge and continental North America.  But the earliest sounding techniques couldn't find one.  It turned out that it was buried -- submerged under hundreds of meters of muck, silt and sand washed out of the region's numerous rivers.

This, and the fact that there hadn't been a big earthquake in the Northwest since settlement by people of European descent, led a lot of geologists to the conclusion that the trench was "aseismic."  Either the small plates east of the ridge weren't moving, or they were slipping underneath the North American Plate so smoothly that there were no measurable earthquakes.

This wasn't just a little bit wrong.  This was stunningly wrong.  This was wrong with whipped cream and a cherry on top.

The red dots represent earthquakes within the seafloor; the green dots are earthquakes within the continental crust of North America.  [Image is in the Public Domain courtesy of the United States Geological Survey]

The Explorer, Juan de Fuca, and Gorda Ridges are very much active spreading centers, and the fact that there haven't been any recent big earthquakes along the trench -- the Cascadia Subduction Zone, denoted on the map by the line with black triangles -- is not good news.  The entire coastline of the Pacific Northwest is compressing as the three small plates get shoved under North America, just like trying to slide something underneath a throw rug makes it rumple and hump up.  In fact, surveys measuring the positions of the peaks in the Cascade Range and on Vancouver Island have found that the whole terrain is being squished west-to-east, so entire mountains are being pushed toward each other.

Imagine the power required to do that.

Further, the fact that the trench is filled with mud doesn't mean the subduction zone is aseismic; quite the opposite.  It turns out that a large part of the mud deposits there are turbidites -- the result of colossal underwater landslides.

Such as might occur during an enormous earthquake.

More of the mechanism was elucidated in 2003, when researchers found that the whole region was experiencing a phenomenon called episodic tremor and slip, where deeper parts of the conjoined plates -- the bits that are hotter and more plastic -- slip against each other, causing barely a rumble.  This slip/tremor happens like clockwork every fourteen months.  While this may sound like a good thing, it's actually the opposite.  Releasing stress that has built up in the deep parts of the fault merely passes that stress upward to the colder, shallower parts that are still locked together, each ETS episode dialing up the energy like the clicking of another tooth in a ratchet.

So along the subduction zone, the two opposing sides of the plates are stuck together, building up more and more tension -- tension that will one day be released as the faultline unzips, and the whole northwest coast of the continent springs back toward the west.

To say the result will be catastrophic is understatement of the year.

It's happened before.  In fact, geologists taking cores of the aforementioned turbidite sediments off the coast of Washington found evidence that in the past ten thousand years it's happened nineteen times.  The spacing between megathrust earthquakes -- as these are called -- varies between three hundred and nine hundred years, with the average being around five.  And the last one happened a little over 323 years ago.

We actually know down to the hour when it happened -- about 9 PM local time, January 26, 1700.  Indigenous tribes in the area have a long tradition that many years ago, there was a terrible earthquake one midwinter night, during which the seashore dropped and salt water flooded in, killing many people.  Evidence from tree rings in "ghost forests" -- the trunks of hundreds of western red cedars that had all been killed simultaneously by an influx of salt -- showed that some time in the 1690s or early 1700s there had been a massive flood from the ocean as the coastline suddenly dropped by several meters.  The exact date was determined from records across the Pacific, where Japanese scribes describe what they called an "orphan tsunami" (a huge wave that, from their perspective at least, was not preceded by an earthquake) striking coastal Japan.  Knowing the speed with which such waves travel across the ocean, geologists were able to determine exactly when the fault last unzipped from end to end.

The earthquake that resulted is estimated to have been somewhere between 8.7 and 9.2 on the Richter Scale, and to have resulted in land movement averaging around twenty meters.

Not pleasant to consider how that would play out if it happened today.

The worst part, for coastal communities today, is how close the Cascadia Subduction Zone is to shore.  At its closest approaches -- near the west coast of Vancouver Island, and from central Oregon south to Cape Mendocino -- it's estimated that the lag time between the ground shaking and the first of the tsunami waves striking the shore will be around eight minutes.  That's eight minutes between being thrown all over the place by an enormous earthquake, and somehow getting yourself to high ground before you're hit by a giant wall of salt water.

I remember when I first heard in detail about the dangers of the Cascadia Subduction Zone -- in 2015, from Kathryn Schulz's brilliant analysis in The New Yorker called "The Really Big One."  It impressed me so much I actually used the fault as a plot point in my novel In the Midst of Lions, where the story is bracketed by earthquakes (one of them massive).  But when I was a Seattle resident in the 1980s, I had no idea.  I still dearly love the Northwest; not only does it have the ideal climate for a fanatical gardener like myself, it has amazing spots for hiking and camping.  During my time there I spent many happy days on the coast of the Olympic Peninsula -- never realizing that a monster lurked offshore.

So while I miss many things about the Northwest, I know I could never live there again.

It may be that the fault won't rupture for another two hundred years; on the other hand, it could happen tomorrow.  While our ability to analyze plate tectonics is light years beyond what it was even thirty years ago, when the situation in the Northwest first began to come clear, we still don't have any way to determine when the earthquake will happen with any kind of precision.  At the moment, all we know is that it will rupture, sooner or later.

And I don't want to be anywhere near it when it does.

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The shroud of ice

It's hard to imagine Antarctica as anything but a frozen wasteland.  Bitterly cold even in summer, barely any precipitation (if it were warmer, Antarctica would be classified as a desert), much of the continent buried under a sheet of ice hundreds of meters thick.  The central "dry valleys" of Antarctica were used as a proving ground for the Mars rovers -- because it was the place on Earth that's the most like Mars.

It's kind of cool that H. P. Lovecraft, writing early in the twentieth century, recognized that this icy and inhospitable land might not always have been that way.  In one of his best short stories, "At the Mountains of Madness," we find out that the continent was once inhabited.  And by "once," I mean long before Homo sapiens appeared on the African savanna.  The denizens of the place -- the "Elder Things" -- were bizarre beasts with five-way symmetry and brains far more advanced than ours, and they built colossal edifices (invariably described as "eldritch" and "cyclopean") which, in the context of the story, are the subject of a scientific investigation.

And being that this is Lovecraft we're talking about, it did not end well.

Even more interesting is his story "The Shadow Out of Time," wherein we find out that the Elder Things amassed the information they have by using their eldritch (of course) technology to switch bodies -- they can flip their consciousness with a member of another sentient species anywhere in time and space, spend a year or two learning about the species and its culture, then flip back and write down what they found out.  The Elder Things lived in Antarctica a hundred million years ago, at which time the frozen continent was a warm, lush, humid jungle.  Listen to how one of their unwilling visitors, a human man from the early twentieth century, describes the place:

The skies were almost always moist and cloudy, and sometimes I would witness tremendous rains.  Once in a while, though, there would be glimpses of the Sun -- which looked abnormally large -- and the Moon, whose markings held a touch of difference from the normal that I could never fathom.  When -- very rarely -- the night sky was clear to any extent, I beheld constellations which were nearly beyond recognition.  Known outlines were sometimes approximated, but seldom duplicated; and from the position of the few groups I could recognize, I felt I must be in the Earth's southern hemisphere, near the Tropic of Capricorn.

The far horizon was always steamy and indistinct, but I could see that great jungles of unknown tree ferns, Calamites, Lepidodendron, and Sigillaria lay outside the city, their fantastic fronds waving mockingly in the shifting vapors...  I saw constructions of black or iridescent stone in glades and clearings where perpetual twilight reigned, and traversed long causeways over swamps so dark I could tell but little of their towering, moist vegetation.

Lovecraft's prescience was shown when plate tectonics was discovered, twenty years after the author's death.  Antarctica wasn't always centered at the South Pole, and in fact had drifted in that direction from somewhere far nearer to the equator.  Since Lovecraft's time, fossils of temperate-climate organisms have been found in abundance, indicating that the climate had shifted dramatically, just as he'd said.

And shrouded underneath thousands of meters of ice, that primordial terrain is waiting to be studied.

Artist's conception of the ancient Antarctic rain forests [Image credit: James McKay of the Alfred Wegener Institut]

That colossal task has been taken on by a team led by glaciologist Stewart Jamieson of Durham University, who led a research project to use a remote telemetry technique called radio-echo sounding to map, for the first time, what's underneath the East Antarctic Ice Sheet, one of the most inhospitable places on Earth.  The region is home to the coldest temperatures ever recorded -- below -80 C -- and experiences katabatic winds (winds caused by cold air rushing downhill from higher elevations) in excess of three hundred kilometers per hour.  

Not a place most of us would choose to visit.  But Jamieson and his team did -- spending whole seasons traversing the continent with their sensors.  The result was a "ghost image," a map showing sharply-peaked, river-carved hills and a hollow that probably was once a massive lake.  The topography reminded Jamieson of Snowdonia in Wales.

"It's an undiscovered landscape," Jamieson said.  "No one's laid eyes on it.  The ice sheet that covers it has been there for at least fourteen million years, perhaps longer.  The land under the East Antarctic Ice Sheet is less well-known than the surface of Mars."

No word on whether his team saw signs of any eldritch and cyclopean architecture.

Despite the fact that I've known for many years that the continents move around and climates change, I'm always a little blown away when I consider how different things are now from even the relatively recent geological past.  And, of course, that the current configuration we have now will itself change as plate tectonics (and human messing-about) alters the Earth's ecosystems.  It may be true that in the span of a human lifetime -- as the famous song by Kansas put it -- it may seem like "nothing lasts forever but the Earth and sky," the truth is that given a long enough time scale, Tennyson hit closer to the mark:

There rolls the deep where grew the tree.

O Earth, what changes hast thou seen?

There, where the long road roars

Has been the stillness of the central sea.

The hills are shadows, and they flow

From form to form, and nothing stands,

They melt like mists, the solid lands,

Like clouds, they shape themselves and go.

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A dangerous beauty

The Greek island of Thera -- often known by its Italianized name of Santorini -- is the southernmost of the Cyclades, an island chain in the Aegean Sea southeast of mainland Greece.  Like much of the region, it's a stunningly beautiful place.  In fact, one of Thera's names in antiquity was Καλλίστη -- "the most beautiful one."

[Image licensed under the Creative Commons Pedro Szekely from Los Angeles, USA, Santorini, Greece (38051518795), CC BY-SA 2.0]

The steep, rugged, rocky terrain, though, didn't happen by accident.  Thera and the other Cyclades formed because they sit near the margin of the Hellenic Subduction Zone, where the northern edge of the enormous African Plate is being shoved underneath the much smaller Aegean Sea Plate.  The result is the formation of an island arc, where the material in the subducted plate is pushed downward to a depth were it melts, and the blobs of magma rise toward the surface to create a chain of volcanoes.  (Most of the islands in the Caribbean, the Aleutians, and pretty much the entirety of the nations of Japan and Indonesia were formed this way.)

This makes it a dangerous place to live.  It was the site of the Minoan-era city Akrotiri, which became prosperous because of being a central port for the copper trade out of Cyprus (the Latin word for copper, cuprum, actually means "metal from Cyprus").  It was second only to Crete as a center of civilization for the Minoan Empire, and was famed for its art, especially elaborate and beautiful frescoes, pottery, and sculpture.  Many of the houses there had running water carried by bronze pipes, and geothermal heat.

The geothermal heat might have clued its residents in that something was going on underground.  All of the high times came to an end with a colossal eruption of the volcano just offshore in around 1600 B.C.E. 

[Nota bene: this is not what inspired the myth of Atlantis, despite the claims you see all over the place on the interwebz.  Plato made it clear that the legend said Atlantis was "west of the Pillars of Hercules" (the Straits of Gibraltar), somewhere out in the Atlantic (thus the name).  But... allow me to stress this point... Atlantis never existed.  Because it's a myth.]

Anyhow, the eruption of Thera not only destroyed pretty much the entire island, but blew an estimated forty cubic kilometers of dust and ash into the air, triggering atmospheric and climatic effects that were recorded by contemporaneous scholars in Egypt and China and draw comparisons from modern geologists to the Mount Tambora eruption of 1815 that caused "The Year Without A Summer."  The eruption generated a tsunami that devastated coastal cities all over the Mediterranean, including the Minoan city of Knossos on the north shore of Crete.  (The Minoan civilization limped along for another couple of hundred years after this calamity, but was finally finished off by a massive earthquake in 1350 B.C.E. that destroyed Knossos completely.)

Here's the thing, though.

The volcano off the coast of Thera is still active.

A paper last week in Nature Communications looked not at the enormous 1600 B.C.E. eruption, but a much smaller eruption in 1650 C.E.  The leadup to this eruption, however, was about as ominous as you could get.  People noticed the water in the seas off the north coast of Thera boiling and changing color -- and dead fish rising to the surface as well, cooked in situ.  Sulfurous gases wafted over the island.  This was followed by a cinder cone emerging from the sea, which proceeded to fling around molten rocks and ash plumes.

Then... boom.

The new research suggests that what triggered the eruption was a landslide, similar to what kicked off the famous Mount Saint Helens eruption of 1980.  In this case, though, the landslide was underwater, off the northwest flank of the volcano.  This landslide did two things -- it displaced huge amounts of water, generating a twenty-meter-high tsunami, and it took the pressure off the top of the magma chamber, causing it to explode.

The combination killed seventy people and hundreds of domestic animals -- horrible, but nowhere near what the island proved itself capable of 3,600 years ago.  The study found that the magma chamber is refilling at a rate of four million cubic meters per year, meaning with regards to subsequent eruptions -- to invoke the old cliché so often used in connection to active volcanoes and tectonic faults, it's not a matter of "if," it's a matter of "when."

Unsurprisingly, the people in the region seem unaware of the time bomb they're sitting on.  "Local populations, decision-makers, and scientists are currently unprepared for the threats posed by submarine eruptions and slope failures, as has been demonstrated by the recent 2018 sector collapse of Anak Krakatau and the 2022 [Hunga Tonga] eruption," the authors write.  "Therefore, new shore-line crossing monitoring strategies... are required that are capable of being deployed as part of rapid response initiatives during volcanic unrest and which enable real-time observation of slope movement."

It remains to be seen how this could help the almost two thousand people who currently live on the slopes of the island, many of them living in houses sitting on layers of fused ash deposited there during the 1600 B.C.E. eruption.  It's something we've seen here before; people like living in tectonically active regions because (1) the terrain is often dramatic and beautiful, (2) volcanic soils are good for agriculture, and (3) people have short memories.  If the last time things went kablooie was almost three hundred years ago, it's easy for folks to say, "What, me worry?"  (Witness the millions of people living near the terrifying Cascadia Subduction Zone, about which I wrote three years ago.  As well as all the people in the aforementioned countries of Japan and Indonesia.)

Anyhow, that's our rather ominous scientific study of the day.  The Earth is a beautiful and dangerous place, and nowhere does that combination come into sharper focus than the Greek islands.  Makes me glad I live where I do -- despite the cold winters, at least I don't have to worry about the place blowing up.

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Bending the light

One of the coolest (and most misunderstood) parts of science is the use of models.

A model is an artificially-created system that acts like a part of nature that might be inaccessible, difficult, or prohibitively expensive to study.  A great many of the models used by scientists today are sophisticated computer simulations -- these are ubiquitous in climate science, for example -- but they can be a great deal simpler than that.  Two of my students' favorite lab activities were models.  One of them was a "build-a-plant" exercise that turned into a class-wide competition for who could create the most successful species.  The other was a striking simulation of disease transmission where we started with one person who was "sick" (each student had a test tube; all of them were half full of water, but one of them had an odorless, colorless chemical added to it).  During the exercise, the students contacted each other by combining the contents of their tubes.  In any encounter, if both started out "healthy," they stayed that way; if one was "sick," now they both were.  They were allowed to contact as many or as few people as they wanted, and were to keep a list of who they traded with, in order.  Afterwards, we did a chemical test on the contents of the tube to see whose tubes were contaminated, then used the list of trades to see if we could figure out who the index case was.

It never failed to be an eye-opener.  In only five minutes of trades, often half the class got "infected."  The model showed how fast diseases can spread -- even if people were only contacting two or three others, the contaminant spread like wildfire.

In any case, models are powerful tools in science, used to study a wide variety of natural phenomena.  And because of a friend and fellow science aficionado, I now know about a really fascinating one -- a characteristic of certain crystals that is being used as a model to study, of all things, black holes.

[Image licensed under the Creative Commons Ra'ike (de:Benutzer:Ra'ike), Chalcanthite-cured, CC BY-SA 3.0]

The research, which appeared last month in Physical Review A, hinges on the effects that a substance called a photonic crystal has on light.  (We met photonic crystals here only a few weeks ago -- in a brilliant piece of unrelated research regarding why some Roman-era glass has a metallic sheen.)  All crystals have, by definition, a regular, grid-like lattice of atoms, and as light passes through the lattice, it slows down.  This slowing effect happens with all transparent crystals; for example, it's what causes the refraction and internal reflection that make diamonds sparkle.  A researcher named Kyoko Kitamura, of Tohoku University, realized that if light could be made to slow down within a crystal, it should be possible to arrange the molecules in the lattice to force light to bend. 

Well, bending light is exactly what happens near a black hole.  So Kitamura and her team made the intuitive leap that this property could be used to study not only the crystal's interactions with light, but indirectly, to discover more about how light behaves near massive objects.

At this point, it's important to clarify that light is not gravitationally attracted to the immense mass of a black hole -- this is impossible, as photons are massless, so they are immune to the force of gravity (just as particles lacking electrical charge are immune to the electromagnetic force).  What the black hole does is warp the fabric of space, just as a bowling ball on a trampoline warps the membrane downward.  A marble rolling on the trampoline's surface is deflected toward the bowling ball not because the bowling ball is somehow magically attracting the marble, but because the marble is following the shortest path through the curved two-dimensional space it's sitting on.  Light is deflected near a black hole because it's traversing curved space -- in this case, a three-dimensional space that has been warped by the black hole's mass.

[Nota bene: it doesn't take something as massive as a black hole to curve space; you're sitting in curved space right now, warped by the mass of the Earth.  If you throw a ball, its path curves toward the ground for exactly the same reason.  That we are in warped space, subject to the laws of the General Theory of Relativity, is proven every time you use a GPS.  The measurements taken by GPS have to take into account that the ground is nearer to the center of gravity of the Earth than the satellites are, so the warp is higher down here, not only curving space but changing any time measurements (clocks run slower near large masses -- remember Interstellar?).  If GPS didn't take this into account, its estimates of positions would be inaccurate.]

In any case, the fact that photonic crystals can be engineered to interact with light the way a black hole would means we can study the effects of black holes on light without getting near one.  Which is a good thing, considering the difficulty of visiting one, as well as nastiness like event horizons and spaghettification to deal with.

So that's our cool scientific research of the day.  Studies like this always bring to mind the false perception that science is some kind of dry, pedantic exercise.  The reality is that science is one of the most deeply creative of endeavors.  The best science links up realms most of us would never have thought of connecting -- like using crystals to simulate the behavior of black holes.

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Bishop Hatto and the mice

To round out our week of looking at odd and creepy tales, today we're going to consider one of the most famous: the story of the evil Bishop Hatto.

Hatto was a real person, and was Archbishop of Mainz in the late tenth century C. E.  He had a reputation for being a dreadful human being, grasping, greedy, and cruel, and in fact had a tower built on a small island in the Rhine (near present day Bingen am Rhein) to control shipping traffic.  The top of the tower had a platform for crossbowmen, and ships were forced to pay tolls to pass the island -- or risk having his bowmen pick off the sailors from their high vantage point.

So Bishop Hatto got richer and the poor got poorer (as they are wont to do).  Things reached a peak in the mid-970s, when a famine struck central Europe.  Rather than use his considerable wealth to ease the suffering of the peasants, he took this as another opportunity to fatten his own coffers, storing up what grain there was and jacking up the prices to wring as much cash as he could from the desperate.  Finally, the peasants had had enough, and according to the best-known version of the legend, plotted to rebel against and depose Bishop Hatto.  But they didn't take into account the bishop's cunning, nor the fact that he had paid informants to keep him apprised of what was going on.  Well aware of what was being planned, he put forth a proclamation that he'd relented and would give away the grain to anyone who needed it.

Relieved, the peasants showed up at Hatto's massive grain storage barn -- only to find that it was empty.

And the doors were barred behind them.

Hatto then had his soldiers set fire to the barn, and as the peasants died screaming, the bishop laughed and said, "Listen to the mice squeak."

Hearing his words, one of the poor unfortunates in the burning barn came to a gap in the wood and shouted, "Mice?  You'll rue your words, Hatto... before this night is over, the mice will come to take their vengeance on you!"

Undaunted, Hatto returned to his residence, and what the legend says happened next is hardly a surprise.  He was settling down for the night, and heard rustling and squeaking -- hordes of rats and mice, swarming up the stairs.  He fled, but they followed him, and eventually he made his way across the Rhine to his tower.  But the mice swam after him... and there was nowhere for him to go.  He was cornered and eaten alive.  And ever since then, the tower on the little island has been called the Mäuseturm -- "Mouse Tower," in German.

Bishop Hatto about to meet his fate (from The Nuremberg Chronicles, 1493) [Image is in the Public Domain]

There are four problems with this legend.

The first is that there's no contemporaneous historical record indicating that Hatto was nibbled to death by mice.  However, given the dearth of any records at all from the tenth century, perhaps we can set that one aside.

A more troubling issue is that the original name of the tower wasn't Mäuseturm -- it was Mautturm (which, more prosaically, means "toll tower").  The renaming of the tower to Mäuseturm seems to have happened much later, and as a sort of play on words that works way better in German than it does in English.

Third, there is no historically credible source documenting Hatto being all that much worse than any other medieval religious or secular leader.  After all, this was a time when being nasty to peasants was right up there with fox hunting and falconry as the favorite sport of the nobility.  There had been an earlier Archbishop of Mainz -- also, confusingly, named Hatto -- whose reputation for being an unmitigated asshole was much better documented.  (Among many other things, he promised Count Adalbert of Babenburg safe passage through his lands, then captured him and had him beheaded, and later plotted unsuccessfully to murder Henry, Duke of Saxony.)  This Hatto's nasty reputation may have besmirched the later Hatto's -- and for what it's worth, Hatto I is also reputed to have come to a bad end, having died after being struck by lightning.

Fourth, the whole eaten-by-mice thing is the punchline of the stories of two other allegedly nasty medieval rulers -- Popiel of Gopło and the Count of Wörthschlössl, each of whom has his own "Mouse Tower" (still standing to this day) where he allegedly met his grisly fate.  To judge by the legends, German mice did nothing but run around all the time looking for cruel peasant-abusers to eat:

Mouse 1: Hey, bro, we gotta get going.  We're supposed to go eat the Count von Wienerschnitzel tonight.

Mouse 2: Seriously?  I've still got indigestion from the archbishop we ate last night.  Can't we find, like, a nice salad bar or something?

Mouse 1: Dude.  Get your ass up.  We're mice, and we eat evil German magnates.  I don't make the rules.

Mouse 2 (*sighs heavily*): Fine.  But I'm fucking well taking tomorrow off.

So for those of you who like tales of divine and/or rodent-mediated vengeance, the whole Bishop Hatto story is kind of a non-starter.  Kind of a shame, really.  It'd be nice if evil people got such a swift comeuppance.  I can think of a few who would be good candidates, if any modern mice who read Skeptophilia are casting about for victims to devour.

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