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Today's topic in Skeptophilia isn't controversial so much as it is amazing.  And shows us once again what a weird, endlessly fascinating universe we live in.

First, though, a bit of a science lesson.

A great many processes in the natural world happen because of the Second Law of Thermodynamics.  The Second Law can be framed in a variety of ways, two of which are: (1) heat always tends to flow from a hotter object to a colder one; and (2) in a closed system, entropy -- disorder -- always increases.  (Why those are two ways of representing the same underlying physical law is subtle, and beyond the scope of this post.)

In any case, the Second Law is the driver behind weather.  Just about all weather happens because of heat energy redistribution -- the Sun warms the ground, which heats the air.  Hot air tends to rise, so it does, drawing in air from the sides and creating a low pressure center (and wind).  As the warm air rises, it cools (heat flowing away from the warmer blob of air), making water vapor condense -- which is why low pressure tends to mean precipitation.  Condensation releases heat energy, which also wants to flow toward where it's cooler, cooling the blob of air further (which is also cooling because it's rising and expanding).  When the air cools enough, it sinks, forming a high pressure center -- and on and on.  (Circular air movement of this type -- what are called convection cells -- can be local or global in reach.  Honestly, a hurricane is just a giant low-pressure convector.  A heat pump, in essence.  Just a fast and powerful one.)

Okay, so that's the general idea, and to any physicists who read this, I'm sorry for the oversimplifications (but if I've made any outright errors, let me know so I can fix them; there's enough nonsense out there based in misunderstandings of the Second Law that the last thing I want is to add to it).  Any time you have uneven heating, there's going to be a flow of heat energy from one place to the other, whether through convection, conduction, or radiation.

But if you think we get some violent effects from this process here on Earth, wait till you hear about KELT-9b.

KELT-9b is an exoplanet about 670 light years from Earth.  But it has some characteristics that would put it at the top of the list of "weirdest planets ever discovered."  Here are a few:

• It's three times the mass of Jupiter, the largest planet in our Solar System.
• It's moving at a fantastic speed, orbiting its star in only a day and a half.
• It's tidally locked -- the same side of the planet is always facing the star, meaning there's a permanently light side and a permanently dark side.
• It's the hottest exoplanet yet discovered -- the light side has a mean temperature of 4,300 C, which is hotter than some stars.

So the conditions on this planet are pretty extreme.  But as I found out in a paper by Megan Mansfield of the University of Chicago et al. in Astrophysical Journal Letters, even knowing all that didn't stop it from harboring a few more surprises.

Artist's conception of KELT-9b [Image is in the Public Domain courtesy of NASA/JPL]

Tidally-locked planets are likely to have some of the most extraordinary weather in the universe, again because of effects of the Second Law.  Here on Earth, with a planet that rotates once a day, the land surface has an opportunity to heat up and cool down regularly, giving the heat redistribution effects of the Second Law less to work with.  On KELT-9b, though, the same side of the planet gets cooked constantly, so not only is it really freakin' hot, there's way more of a temperature differential between the light side and the dark side than you'd ever get in our Solar System (even Mercury doesn't have that great a difference).

So there must be a phenomenal amount of convection taking place, with the atmosphere on the light side convecting toward the dark side like no hurricane we've ever seen.  But that's where Mansfield et al. realized something was amiss.  Because to account for the temperature distribution they were seeing on KELT-9b, there would have to be wind...

... moving at 150,000 miles per hour.

That seemed physically impossible, so there had to be some other process moving heat around besides simple convection.  The researchers found out what it is -- the heat energy on the light side is sufficient to tear apart hydrogen molecules.

At Earth temperatures, hydrogen exists as a diatomic molecule (H2).  But at KELT-9b's temperatures, the energy tears the molecules into monoatomic hydrogen, storing that as potential energy that is then rereleased when the atoms come back together on the dark side.  So once again we're talking the Second Law -- heat flowing toward the cooler object -- but the carrier of that heat energy isn't just warm air or warm water, but molecules that have been physically torn to shreds.

So, fascinating as it is, KELT-9b would not be the place for Captain Picard to take his away team.  But observed from a distance, it must be spectacular -- glowing blue-white from its own heat, whirling around its host star so fast its year is one and a half of our days, one side in perpetual darkness.  All of which goes to show how prescient William Shakespeare was when he wrote, "There are more things in heaven and Earth, Horatio, than are dreamt of in your philosophy."

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Ill winds

When you think about it, wind is a strange phenomenon.

In its simplest form, wind occurs when uneven heating of the surface of the Earth causes higher pressure in some places than in others, and the air flows from highs to lows.  But it's considerably more complex (and interesting) than that, because as surface-dwellers we often forget that there's a third dimension -- and that air can move vertically as well as horizontally.

I got to thinking of this because I've been reading Eric Pinder's fascinating, often lyrical, book Tying Down the Wind: Adventures in the Worst Weather on Earth.  Pinder is a meteorologist who was stationed as a weather observer on Mount Washington, New Hampshire, which one in every three days clocks hurricane-force winds (greater than 119 kilometers per hour) and is the spot that holds second place for the highest anemometer-clocked wind speed ever recorded on the Earth's surface (an almost unimaginable 372 kilometers per hour; the only higher one was on Barrow Island, Australia, which on April 10, 1996, during Cyclone Olivia, hit 407 kilometers per hour).

The fact that air moves vertically, of course, is why air moves horizontally.  When the Sun heats a patch of ground, the air above it warms and becomes less dense, causing it to rise.  This creates an area of low pressure, and air moves in from the side to replace the air moving upward.  This process, writ large, is what causes hurricanes; the heat source is the ocean, and the convection caused by that tremendous reservoir of heat energy not only generates wind, but when the water-vapor-laden air rises high enough, it undergoes adiabatic cooling, triggering condensation, cloud formation -- and torrential rain.

The process can go the other direction, though.  A weather phenomenon that has long fascinated me is the convective microburst, something that most often happens in hot, dry climates in midsummer, like the American Midwest.  The process goes something like this.  Rising air triggers cloud formation, and ultimately rain clouds.  When the droplets of water become heavy enough that the downward force of gravity exceeds the upward force of the air updrafts, they fall, but they drop into the layer of warm, dry air near the surface, so they evaporate on the way down, often not making it to the ground as rain.  Evaporation cools the air that surrounds them, making it denser -- and if the process happens fast enough, it creates a blob of air so much denser than the air surrounding it that it literally falls out of the sky, hits the ground, and explodes outward.  Windspeeds can go from nothing to 100 kilometers per hour in a matter of fifteen seconds.  Then -- a couple of minutes later -- it's all over, the dust (and any airborne objects) settle back to Earth, and everyone in the vicinity staggers around trying to figure out what the hell just happened.

A convective microburst in Nebraska [Image licensed under the Creative Commons Couch-scratching-cats, Downburst 1, CC BY-SA 4.0]

Microbursts aren't the only weird weather phenomenon having to do with density flow.  Have you heard of katabatic winds?  If you haven't, it's probably because you live in an area where they don't happen, because they're really dramatic where they do.  Katabatic winds (from the Greek κατάβασις, "falling down") occurs when you have significant chilling of a layer of air aloft -- on top of a mountain, for example, or (even better) over an ice sheet.  This raises the density of the air mass, creating a huge difference in gravitational potential energy from high to low.  The superchilled air pours downward, funneling through any gaps in the terrain; the effect is accentuated when there's a low pressure center nearby.  The katabatic winds off Antarctica (nicknamed "Herbies," for no reason I could find) and the ones off Greenland (known by the Inuit name piteraq) can be unpredictable, fast, and frigid, often driving layers of snow horizontally and creating sudden whiteout conditions.

Then there's the foehn (or föhn) wind, created when onshore air flow is pushed up against a mountain range.  This occurs in the southern Alps, central Washington and Oregon, parts of Greece and Turkey, and south-central China.  On the windward side of the mountains, the air rises and cools; this causes condensation and higher rainfall.  But when the air piles up and gets pushed over the mountain passes, it warms for two reasons -- the pressure increases as it goes downhill on the other side, and the condensation of water vapor releases heat energy.  The result is a warm, dry wind that pours downhill on the leeward side of the mountains -- the source of the "Chinook winds" that desiccate the northwestern United States east of the Cascades.

Interestingly, foehn winds are associated with physiological problems -- headaches, sinus problems, and mood swings.  It's documented that prescriptions for anxiolytic medications go up when the foehn is blowing; and a study at the Ludwig Maximilians Universität München found that suicide and accident rates both go up by about ten percent during periods when there's a strong foehn, and no one knows why exactly.

In any case, there are a few interesting tidbits about a phenomenon we usually don't think about unless we're in the path of a hurricane or tornado.  Something to think about next time your face is brushed by a warm breeze.  We live at the bottom of a layer of moving fluid, driven by invisible forces that usually are benign.  Only occasionally do we see how powerful that fluid can be -- preferably, from a safe distance.

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Locked in place

The Moon orbits the Earth in such a way that the same side always faces us.  Put another way, its periods of revolution and rotation are the same; it takes the same amount of time for the Moon to turn once on its axis as it does to circle the Earth.

This seems like a hell of a coincidence, but there is (of course) a physical explanation for it.  Close orbits -- either of a planet around its host star, or a satellite around a planet -- generate a high tidal force, which is the gradient in the gravitational force experienced by the near side of the orbiting body as compared to the far side.  There's always going to be a tidal force; even tiny Pluto has a greater pull from the Sun on the near side than it does on the far side, but with a small body at that great a distance, the difference is minuscule.  (You're experiencing a tidal force right now; the Earth is pulling harder on your feet than on your head, assuming you're not upside down as you're reading this.)  But the Moon's proximity to the Earth means that the tidal force it experiences is comparatively huge.  So even if it once rotated faster than it revolved, the higher pull on the near side slowed its rotation down -- a sort of gravitational drag -- until the two matched exactly.

The result is called 1:1 tidal locking, and is why (apologies to Pink Floyd) there is no permanently dark side of the Moon.  There's a near-Earth and a far-Earth side, but no matter where you are on the Moon, you'll have a 28-day light/dark cycle.  However, the apparent position of the Earth in the sky doesn't change.  If where you stand on the Moon's surface, the Earth appears to be hovering thirty degrees above the western horizon, that's where it will always be from that perspective.

It's been known for some time that planets can also be tidally locked.  Once again, it's more likely to happen when they orbit close to their host star, which means a lot of tidally-locked planets are probably so hot they're uninhabitable.  But the situation changes if the host star is a red dwarf -- small, low-luminosity stars that are incredibly common, making up almost three-quarters of the stars in the Milky Way.  These stars have such a low heat output that the "Goldilocks zone" -- the distance from the star in which the conditions are "just right" for liquid water to form -- is very close in.

So a star in a red dwarf's habitable zone might well also be tidally locked.

Think of how bizarre a situation that would be.  If the planet is at the right distance for the lit side to be comfortable, there'd be a region of perpetual twilight bounding it, and on the other side of that, permanent, freezing-cold night.  Not only that; this would create the convection cell from hell.  Weather down here on Earth is largely caused by uneven heating of the planet's surface; air warms and rises near the Equator, cools, eventually becoming cool enough to sink and completing the circle.  The Earth's rotation and topography complicate the situation, but basically, that convective rise-and-fall is what generates wind, clouds, rain, snow, and the rest of the meteorological picture.

On a tidally-locked planet, these processes would be almost certainly be amplified beyond anything we ever see on Earth.  Especially the twilit boundary zone -- the constant heating of the bright side, and loss of heat to radiation on the dark side, would cause the atmosphere on the bright side to rise, drawing in cold air from the dark side fast.  The result would be a screaming hurricane across the boundary.

At least, so we think.  We don't have any tidally-locked planets to study, only airless moons.

Until now.

A study out of McGill University has confirmed the first tidally-locked exoplanet, LHS 3844b, a "super-Earth" that was identified by measuring the light coming off the planet at different places in its orbit -- something that allowed the researchers to estimate its temperature.

Artist's impression of the dark side of LHS 3844b [Image credit: NASA/JPL-Caltech/R. Hurt (IPAC)]

Chances are, LHS 3844b doesn't have much of an atmosphere, so the convective hellscape I described above might not apply to it.  Still, the idea that astronomers have identified that an exoplanet is tidally locked is kind of astonishing.  The first exoplanet was only discovered in 1992; in the intervening thirty-odd years not only have we found thousands of them, we're now getting so good at analyzing them we can figure out the size of their orbits, how fast they rotate, and the probable composition of their atmospheres.

Our understanding of the universe has accelerated so much, it's hard even to imagine where it might be headed.  The idea that we could not only find an exoplanet around a distant star, but determine that the same side of the planet always faces the star, boggles the mind.

The future of astronomy is looking pretty stellar, isn't it?

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The water world

Coming hard on the heels of an encouraging paper about the possibilities of near-light-speed travel, at which we might potentially have probe data from the nearest star to the Sun in ten years or so, we have an even more encouraging study of a place right here in the Solar System that might be worth looking at as a home of extraterrestrial life.

The place is Enceladus, the sixth largest moon of the planet Saturn.  It's a pretty decent-sized object, about one-seventh the diameter of the Earth.  Flyby data from the spacecraft Cassini in 2014 showed that it's a curious place, with a liquid water ocean capped by a shell of solid ice.  There are geysers coming up through cracks in the surface, and Cassini was able to sample the spray and confirm that it is, indeed, water.

Enceladus [Image is in the Public Domain courtesy of NASA/JPL and the Cassini probe]

But it's kind of a topsy-turvy world even so.  Here on the Earth, oceans are warmest at the top and coolest at the bottom; the deep parts of the ocean are the most stable ecosystems on Earth, always completely dark, under crushing pressure, and about four degrees Celsius (the temperature at which water is densest).  On Enceladus, it's the other way around; coldest on top, where it's in contact with the undersurface of the ice cap, and warmest at the bottom, where it's in contact with the core of the moon.  There's no land surface; the oceans on Enceladus are estimated at thirty kilometers deep (contrast that to an average three kilometers for Earth's oceans).

The upside-down temperature structure on Enceladus is what makes it an excellent place to look for extraterrestrial life, but to see why, we'll need to take a brief digression for a physics lesson.

One of the main drivers of ocean currents -- the movement of water not only horizontally, but vertically -- is convection, which is fluid flow because of differences in density.  One of the best-studied examples, which I described more fully in a post a few weeks ago, is the Atlantic Conveyor (known to scientists as the Atlantic Meridional Overturning Circulation), in which evaporation from the warm Gulf Stream as it flows north cools the water and makes it more saline, both of which have the effect of increasing its density.  Eventually, the blob of water becomes cool and saline enough that it exceeds the density of the water surrounding it, and it sinks.  This usually occurs in the North Atlantic southwest of Iceland, and that draw-down is what pulls more warm water north, keeping the whole system moving.

This has multiple effects, two of which concern us here.  The first is that it acts as a heat transfer mechanism, warming the air (and the land near it) and giving the American Northeast, the Maritimes of Canada, Iceland, and northwestern Europe the temperate climate they have, which otherwise would be a lot more like Siberia.  Second, the water carries with it nutrients of various sorts, and redistribution of those nutrients forms the basis of phytoplankton growth and the food chain.  (The most obvious example of this latter effect is the El Niño Southern Oscillation, in which upwelling of nutrient-laden water off the coast of Peru supports a huge population of fish -- until an El Niño year, when warm water flowing east blocks the upwelling, and the entire food chain collapses.  The four-year lots-of-fish to no-fish cycle was observed as far back at the seventeenth century, when the Spanish rulers of Peru noted that the collapse often started in midwinter, and gave it the name El Niño, which refers to the baby Jesus.)

So as long as you have alterations in density, a fluid will move.  It's what drives all weather, in fact; ground heating raises the temperature of air, lowering its density and making it rise, generating a low-pressure system that draws in more air to replace what's moving aloft.  This causes wind, and if the air has moisture, it'll condense out as it rises and cools, causing rain and/or snow.

Of course, the water drawn down by the sinking of the Gulf Stream near Iceland (or the air moving upward because of warming) is only half the picture.  It's got to come back somehow, and both the atmosphere and ocean are filled with convection cells, swirling, more-or-less circular currents following the motion both vertically and horizontally.  And once again -- to return to why the topic comes up -- these redistribute not only heat, but (in the case of water), nutrients.

On Enceladus, the pattern is upside down as compared to Earth's oceans.  Water in contact with the underside of the ice shell cools and eventually sinks, drawing warmer water up from near the center of the moon.  This mixing stirs the pot, and any potential nutrient chemicals don't just settle out on the bottom.  Thus, Enceladus is a prime candidate for extraterrestrial life of some sort.

To be sure, it'd be different from what we have here on Earth.  A lot different.  Despite the cracks and geysers, the ice shell on Enceladus is thick and pretty much solid, so any living things under there would never come into contract with direct rays of the Sun (as dim as they'd be out there).  The only energy source would be the warmth of the core, so there'd be no photosynthesis, only chemosynthesis, perhaps similar to the weird organisms near Earth's hydrothermal vents in the deep oceans.  

Even so, it's a prime spot to look for signs of life.  And unlike Proxima Centauri, the nearest star, which in a best-case scenario would require ten years for an outward-bound near-light-speed probe and returned signal back on Earth, the same round-trip to Enceladus would take on the order of three hours.  

Once again highlighting that the universe is freakin' huge.

If we can develop near-light-speed travel, maybe the first thing to do is to send some probes to explore our own Solar System more thoroughly.  Not only Enceladus, but a similar water-world moon of Jupiter, Europa, which is even closer.  I'd say the likelihood of finding intelligent life on either one is slim to none, so I wouldn't be looking for anything like the super-tech civilization on a planet orbiting Vega in the movie Contact, but I think there's an excellent chance that there's something living down there, even if it turns out to be only as complex as bacteria.

But even so.  How cool would that be?  A life form completely unrelated to anything we have down here.  And if we did find life on Europa or Enceladus, it would really bolster the hunch I've had for years, which is that life is common in the universe.

And I, for one, would settle for that in a heartbeat.

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The sad truth of our history is that science and scientific research has until very recently been considered the exclusive province of men.  The exclusion of women committed the double injury of preventing curious, talented, brilliant women from pursuing their deepest interests, and robbing society of half of the gains of knowledge we might otherwise have seen.

To be sure, a small number of women made it past the obstacles men set in their way, and braved the scorn generated by their infiltration into what was then a masculine world.  A rare few -- Marie Curie, Barbara McClintock, Mary Anning, and Jocelyn Bell Burnell come to mind -- actually succeeded so well that they became widely known even outside of their fields.  But hundreds of others remained in obscurity, or were so discouraged by the difficulties that they gave up entirely.

It's both heartening and profoundly infuriating to read about the women scientists who worked against the bigoted, white-male-only mentality; heartening because it's always cheering to see someone achieve well-deserved success, and infuriating because the reason their accomplishments stand out is because of impediments put in their way by pure chauvinistic bigotry.  So if you want to experience both of these, and read a story of a group of women who in the early twentieth century revolutionized the field of astronomy despite having to fight for every opportunity they got, read Dava Sobel's amazing book The Glass Universe: How the Ladies of the Harvard Observatory Took the Measure of the Stars.

In it, we get to know such brilliant scientists as Willamina Fleming -- a Scottish woman originally hired as a maid, but who after watching the male astronomers at work commented that she could do what they did better and faster, and so... she did.  Cecilia Payne, the first ever female professor of astronomy at Harvard University.  Annie Jump Cannon, who not only had her gender as an unfair obstacle to her dreams, but had to overcome the difficulties of being profoundly deaf.

Their success story is a tribute to their perseverance, brainpower, and -- most importantly -- their loving support of each other in fighting a monolithic male edifice that back then was even more firmly entrenched than it is now.  Their names should be more widely known, as should their stories.  In Sobel's able hands, their characters leap off the page -- and tell you a tale you'll never forget.

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

Polygons on Pluto

When NASA's New Horizons probe made a flyby of Pluto last summer, it sent back remarkably detailed photographs of this strange frozen dwarf planet, so distant that even one of the fastest man-made vehicles took nine years to get there.  Naturally, it's taken scientists a while to explain what the photographs contained, given our prior lack of knowledge of Pluto's composition.

One of the most curious features noticed were more-or-less straight-sided "polygons" in a region called "Sputnik Planum."  There's no doubting that the pattern is peculiar:

[image courtesy of NASA/JPL]

And of course, all it takes is "peculiar observation" added to "scientists haven't explained this yet" to send the woo-woos of the world off into a dizzying spiral of completely loony speculation.

Here are a few suggestions as to what the "polygons" might be:

• the rubble-strewn walls of an ancient alien city
• a secret base on Pluto designed (possibly with alien help) by NASA.  If you buy this one, then New Horizons was not a research mission, but was going to reestablish contact with people who are already there
• evidence that Pluto is actually the fabled planet Nibiru
• the encampments of a hostile force from another solar system

Apropos of the last one, it didn't take long for someone to remember that Pluto has been identified as the site of H. P. Lovecraft's world "Yuggoth," home to sentient fungus-beings who are able to switch personalities with human beings and keep our consciousness stored in what amount to high-tech tin cans.

So okay.  Let's start with the fact that H. P. Lovecraft's story "The Whisperer in Darkness" is labeled "fiction."  As far as the rest of the hypotheses (I hate to dignify them with that name), allow me simply to say that if I were looking for a place to build a base, Pluto would not be my first choice.  For one thing, I hate cold weather, and Pluto's average surface temperature is -229 C.  Plus, it doesn't appear to have much of an atmosphere, and I kind of like going outside without putting on a space suit.

Additionally, we just got word a couple of days ago from actual scientists (i.e. people who prefer evidence and logic than talking out of their asses) that they now have a good working explanation for the polygons.  Planetary astronomers Andrew J. Dombard and Sean O'Hara of the University of Illinois have proposed that the pattern can be explained by vigorous convection -- what we are seeing are the tops of Rayleigh--Bénard convection cells, which occur when a fluid is heated from below.  (This is what causes the pattern you observe if you carefully add cream to hot coffee without stirring.)

"Evidence suggests this could be a roiling sea of volatile nitrogen ice," Purdue planetary scientist Jay Melosh explained.  "Imagine oatmeal boiling on the stove; it doesn't produce one bubble for the entire pot as the heated oatmeal rises to the surface and the cooler oatmeal is pushed down into the depths, this happens in small sections across the pot, creating a quilted pattern on the surface similar to what we see on Pluto.  Of course, on Pluto this is not a fast process; the overturn within each unit happens at a rate of maybe two centimeters per year."

So once again, we have a cool explanation of an odd natural pattern, without any recourse to aliens, conspiracies, Nibiru, or Yuggoth.  All of which reminds me of the wonderful quote from Tim Minchin: "Throughout history, every mystery ever solved has turned out to be... not magic."