The story of the Scablands

After my rather cataclysmic posts about geology last week, which looked at the volcano off the Greek island of Thera and the fault just waiting to rupture near the Pacific Northwest, one of my friends and a long-time loyal reader of Skeptophilia asked me if I'd ever done a post on the "Channeled Scablands."  I told him I'd mentioned it once or twice, but always in passing.

So as befits a catastrophe so big it beggars belief, I thought a more thorough look was warranted.

There's a bizarre bit of terrain in what is now eastern Washington and Oregon that goes by the rather horrid-sounding name my friend referenced, and if you ever fly over it, you'll see why.  It's formed of teardrop-shaped pockets of relatively intact topsoil surrounded by gullies floored with bare rock.  The terrain has the look of what a shallow stream does to a sandy beach as it flows into sea, only on a gargantuan scale:

[Image licensed under the Creative Commons DKRKaynor, Channeled Scablands, CC BY-SA 4.0]

Then there's Dry Falls, in the upper Grand Coulee Basin, which even has a plunge pool basin at its foot... but almost no water:

[Image licensed under the Creative Commons © Steven Pavlov / http://commons.wikimedia.org/wiki/User:Senapa / CC BY-SA 3.0, Dry Falls (Washington), CC BY-SA 3.0]

Geologists figured out pretty quickly that the entire terrain was sculpted by a huge amount of running water.  But the problem is, the entire area is a desert, and apparently has been for a long while.

So where'd all the water come from -- and where did it go?

The answer turned out to be the Missoula Megaflood -- a tremendous flood (thus the name) that occurred eighteen thousand years ago, and which is right up there with Thera and the Cascadia Subduction Zone on our list of things that are big and scary and can kill you.

What apparently happened is that during the last ice age, a glacial dam formed across the northern Idaho Rockies, blocking the outflow of what are now the Columbia, Snake, Okanogan, Pend Oreille, and Spokane Rivers.  As the climate warmed, the ice melted, but all that water had nowhere to go, so it backed up into an enormous lake -- called Lake Missoula -- that covered a good bit of what is now western Montana. 

As the ice age ended, the warming continued.  Eventually this caused the ice dam to collapse, and all that water drained out, sweeping across what is now eastern Washington, and literally scouring the place down to bedrock. 

What made the flood even worse was a phenomenon called isostasy.  We're used to thinking of the tectonic plates as moving back and forth, more or less parallel to the Earth's surface, but what is less obvious is that they can also move up and down -- perpendicular to the surface, like ice cubes bobbing in a glass of sweet tea.  These chunks of the Earth's crust are actually floating in the semi-solid mantle beneath them, and the level they float is dependent upon how heavy they are, just as putting heavy weights in a boat makes it float lower in the water. 

Well, as the Cordilleran Ice Sheet melted, that weight was removed, and this caused the flat piece of crust underneath it to lift upward on its eastern edge.

The whole western corner of the United States tilted toward the Pacific Ocean.  It's like having a full bowl of water on a table, and lifting one end of the table. The bowl will dump over, spilling out the water, and it will flow downhill and run off the edge -- just as Lake Missoula did.

The result was a colossal flood that at its peak was traveling at an estimated one hundred kilometers an hour.  Dry Falls was, at that point, an enormous waterfall five times the width of Niagara Falls, with a flow rate ten times higher than all of the rivers in the world combined.

[Nota bene: This sort of isostatic tilt is still going on today, most notably underneath Great Britain.  During the last ice age, Scotland was completely glaciated; southern England was not.  The melting of those glaciers has resulted in isostatic rebound, lifting the northern edge of the island by ten centimeters per century.  The problem is, the whole country is connected (however a lot of Scottish people might wish otherwise), so the entire island is tipping like a teeter-totter.  The tilt is pushing southern England downward, and it's sinking, at about five centimeters per century.  Fortunately, there's no giant lake waiting to spill across the country.]

These kinds of megafloods aren't uncommon, usually during the transition between a glacial and an interglacial period.  Another place this happened is not far from where I live -- around thirteen thousand years ago, there was an ice dam across what is now the St. Lawrence River, blocking the main outflow from the Great Lakes.  This backed all that water up into a huge lake called Lake Agassiz, which encompassed all of the Great Lakes and then some.  It was the same story as Lake Missoula; as the climate warmed, the ice dam collapsed, and a large percentage of the water drained out into the North Atlantic.  Some climatologists think that this may have been responsible for the Younger Dryas event, when the warming trend in North America suddenly reversed, the temperatures dropping in only a few decades by an estimated 7 C -- because all that fresh water temporarily shut down the North Atlantic Meridional Overturning Circulation, stopping the Gulf Stream in its tracks and sending eastern North America, Greenland, and western Europe back into the deep freeze for over a thousand years.  (The link between the draining of Lake Agassiz, the Younger Dryas, and the shutdown of the NAMOC is far from settled, however.)

This sort of thing, besides being fascinating in its own right, always makes me think of the people who talk about Earth being "fine tuned" for human habitation.  When you start looking into geology, climatology, and astronomy, you realize how tenuous our existence actually is.  That we've done as well as we have, despite all the natural calamities, is impressive, but our continued survival is hardly guaranteed.  We'd better start understanding the past history of our home, including the violent and uncomfortable bits -- lest our own reckless and heedless actions trigger a catastrophe we're ill prepared to deal with.

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A map from the home world

One of the most persistent -- dare I say, canonical -- stories of alien abduction is the tale of Betty and Barney Hill.

The gist of the story is that the Hills, a couple from Portsmouth, New Hampshire, were driving home from their vacation in September of 1961, and near Franconia Notch, New Hampshire they saw a UFO that seemed to be following them.  After observing it for a while, including through binoculars, they experienced a "time-slip," and found themselves back home without any memory of how they'd gotten there.  The following day, they noticed some oddities -- Barney's new dress shoes were scuffed, the leather strap on his binoculars was broken, neither of their watches worked, and there were several shiny concentric marks on the hood of their car.

They were puzzled, but no explanation seemed forthcoming, so they forgot about it, until Betty started to have dreams about being aboard a spacecraft.  This eventually led to some hypnosis sessions in which both of them claimed to have suppressed memories of being abducted and examined (our lore about aliens doing, shall we say, rather intimate examination of abducted humans comes largely from Barney's claims under hypnosis).

All of this would be nothing more than your usual Close Encounter story -- lots of wild claims, nothing in the way of hard evidence -- if it weren't for one thing that Betty revealed.  While she was on the spaceship, she said, she was shown a star map that had the aliens' home world and various other star systems with lines between them showing "trade routes."  She attempted to reconstruct a two-dimensional drawing (she said the map she'd been shown was three-dimensional), and here's what she drew:

Now, potentially, this could be interesting.  One of the more eye-opening things I learned when I was a teenager watching the original Cosmos series was that the constellations in our night sky only seem 2-D from our perspective, but there's actually a third dimension -- depth -- that we can't see from Earth.  If you add that third dimension, it becomes obvious that what we call "constellations" are actually random assemblages of stars that only seem near each other from our perspective, but are actually at greatly varying distances from us.  This means that if they were observed from a different vantage point, the constellations would look nothing like they do here at home -- and in fact, many of the stars that appear to be close together would be widely separated in the sky. 

One of the coolest animations from the series was looking at the stars of the Big Dipper, first as we see it from the Earth, then making a huge circle around it.  It doesn't take much of a difference in angle to make it look nothing at all like the Big Dipper.  Here's the constellation as it's seen from Earth, and the same stars as viewed after a ninety-degree revolution around the star in the lower left corner:

So if Betty Hill's recollection of the alien star map was real, then it'd be pretty convincing -- because the aliens presumably would have drawn the stars from the perspective of their home star system, not ours.  This would be mighty hard to fake now, much less 58 years ago.  So the race was on to try and figure out whether the map Betty Hill drew conformed to any known configuration of stars as viewed from somewhere else in the galaxy.

The person whose answer is the most commonly accepted by UFO enthusiasts is Marjorie Fish, who identified the home world of the aliens as Zeta Reticuli (thus kicking off all of the claims that the Annunaki, the "Greys," and various other superintelligent species have come here from that star system).  Starting from that star, Fish said, there are nearby stars that could represent the ones on the Hill map.

Which brings up the problems with the claim.

Recall that the map is the only hard evidence -- if you can call it that -- to come out of the Hill story.  Brian Dunning, of the brilliant blog Skeptoid, is critical of the claim right from the get-go:

Several years [after the alleged abduction], a schoolteacher named Marjorie Fish read a book about the Hills.  She then took beads and strings and converted her living room into a three dimensional version of the galaxy based on the 1969 Gliese Star Catalog.  She then spent several years viewing her galaxy from different angles, trying to find a match for Betty's map, and eventually concluded that Zeta Reticuli was the alien homeworld.  Other UFOlogists have proposed innumerable different interpretations.  Carl Sagan and other astronomers have said that it is not even a good match for Zeta Reticuli, and that Betty's drawing is far too random and imprecise to make any kind of useful interpretation.  With its third dimension removed, Betty's map cannot contain any useful positional information.  Even if she had somehow drawn a perfect 3D map that did exactly align with known star positions, it still wouldn't be evidence of anything other than that such reference material is widely available, in sources like the Gliese Star Catalog.

The problem runs deeper than that, though.  Long-time readers of Skeptophilia may recall a piece I did a while back on ley lines -- the idea that there are towns and sacred sites that are aligned because there are "energy currents" beneath the ground that flow in straight lines, and were why the ancients chose to build on those specific sites.  The trouble is (as my post describes), in any arrangement of random dots, you can find strings of dots that are close to falling in a straight line, just by random chance.  No "energy currents" required.

Here, the difficulty is magnified by the fact that we don't just have a couple of hundred dots (or, in this case, stars) to choose from, but tens of thousands, and that's just counting the relatively nearby ones.  Also, they're not on a flat surface, as with the ley lines; they're in a three-dimensional grid, which you're allowed to look at from any perspective you want to.

If those were Marjorie Fish's constraints, it's actually astonishing that she took years to find a group of stars that matched Betty Hill's map.

We're pattern-finding animals, we humans.  As with pareidolia -- our capacity for seeing faces in inanimate objects like clouds, walls, and grilled-cheese sandwiches -- if there's no pattern there, our brains will often invent one.  Add to that confirmation bias and just plain wishful thinking, and it's not hard to see that the Hill map -- still considered the best evidence for the Hills' story -- is actually not much in the way of evidence at all.

Allow me to emphasize that I'm not saying Betty and Barney Hill weren't abducted.  It's just that -- to end with a quote from Neil DeGrasse Tyson -- "As a scientist, I need more than 'you saw it...'  If you have an actual object taken from a spacecraft, though, you'll have something of alien manufacture, and anything that has crossed interstellar space to get to Earth is going to be interesting.  So show me an object you've taken from the spaceship, and then we can talk."

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Little cat man

It's amazing how many attempts it took for primates to successfully colonize North America.

There's only one primate species currently in the continent.  Us.  Other mammalian groups -- carnivores, rodents, ungulates, insectivores, bats, and so on -- have done fine here, flourishing and diversifying and lasting for tens of millions of years.

Primates haven't been so successful.

The first primates -- well, proto-primates -- in North America were the plesiadapiformes, which first appear in the fossil record in the early Paleocene Epoch, right after the Chicxulub Impact pretty well wiped out all the big animal species (most notably, the non-avian dinosaurs).  To modern eyes, they would have looked a bit like squirrels:

[Image licensed under the Creative Commons Nobu Tamura (http://spinops.blogspot.com), Plesiadapis NT, CC BY-SA 3.0]

Despite the superficially squirrelly appearance, their skulls, and especially their teeth, show clear affinities with primates, not with rodents.

These guys were widespread, living throughout North America, Europe, and Asia.  All of those continents were still connected at this point -- what had been Pangaea had broken into a northern continent (Laurasia) and a southern continent (Gondwanaland, made up of what are now South America, Australia, and Antarctica).  But things were changing, as they are wont to do.  The Central Atlantic Magmatic Province had kicked into high gear, rifting Laurasia and splitting what would become North America from the rest of the continent, opening up the North Atlantic Ocean.  At that point, the primate species (and everyone else) in North America were pretty well stuck there.

And they lasted a while.  But at the end of the Eocene Epoch, around 34 million years ago, the North American continent got significantly cooler and drier.  This drove all the warmth-loving native primates to extinction.

[Nota bene: South American monkeys come from a different lineage.  Recall that at this point, North and South America were pretty far apart, and there was a lot of ocean in between.  South America was a great deal closer to Africa, though -- and was colonized by primates from Africa, probably by monkeys and other species clinging to rafts of plant roots and brush torn loose during storms.  They seem to have made this amazing journey in several pulses, starting about thirty million years ago.  In any case -- the genetic and structural evidence is clear that South American monkeys are related to primates from Africa, not the extinct groups in North America.]

In any case, North America was primateless for about four million years.  Then, suddenly, a primate appeared in what is now Nebraska.  This species, named Ekgmowechashala (the name is Sioux for "little cat man"), weighed about three kilograms, and looked a bit like a lemur.  But where the hell did it come from?

The whole topic came up in the first place because of new research into this odd creature, which appeared in the Journal of Human Evolution last week.  A thorough analysis of Ekgmowechashala fossils dating from around thirty million years ago found that they most closely resemble primate species in China and eastern Siberia.  Apparently, the ancestors of Ekgmowechashala did what the ancestors of the Native Americans would do, millions of years later.  They took advantage of the fact that the cooler conditions locked up more sea water in the form of ice, lowering sea levels.  Among other things, this turned what is now the Bering Sea into a broad valley with rolling hills (nicknamed Beringia), allowing them to cross into North America.

"The 'Lazarus effect' in paleontology is when we find evidence in the fossil record of animals apparently going extinct -- only to reappear after a long hiatus, seemingly out of nowhere," said Chris Beard, of the University of Kansas, who was senior author of the paper.  "This is the grand pattern of evolution that we see in the fossil record of North American primates. The first primates came to North America about 56 million years ago at the beginning of the Eocene, and they flourished on this continent for more than 20 million years.  But they went extinct when climate became cooler and drier near the Eocene-Oligocene boundary, about 34 million years ago.  Several million years later Ekgmowechashala shows up like a drifting gunslinger in a Western movie, only to be a flash in the pan as far as the long trajectory of evolution is concerned.  After Ekgmowechashala is gone for more than 25 million years, Clovis people come to North America, marking the third chapter of primates on this continent. Like Ekgmowechashala, humans in North America are a prime example of the Lazarus effect."

So the "little cat man" didn't last very long -- the continual cooling of the climate, peaking with the repeated continental glaciations of the "Ice Ages," was more than primates could cope with.  But as Beard points out, that didn't stop our own species from doing the very same thing, eventually colonizing all of North America, and more inhospitable places yet.

But it's odd to think that thirty million years ago, there was something very like a lemur living near what is now Omaha.

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The greatest wall

Sometimes simple words can be the hardest to define accurately.

For example, in physics, what do we mean by the word structure?  The easiest way to conceptualize it is that it's a material object for which whatever force is holding it together outcompetes any other forces that might be involved.  For example, a brick could be considered a structure, because the chemical bonds in the fired clay are stronger than the forces trying to pull it apart.  The sand on a beach, however, doesn't form a single structure, because the forces between the sand grains aren't strong enough to hold them together against the power of the wind and water.

Simple enough, it'd seem, but once you get out into space, it gets a little more difficult.

In astronomy, a structure is something that is bound together by gravity so that on some scale, it acts as a single unit.  The Solar System is a cosmic structure; within it, the gravitational pull of the Sun overwhelms all other forces.  The Milky Way is a cosmic structure by the same definition.  But how big can you get and still call it a single structure?  The question gives astronomers fits, because (to abide by the definition) you have to show that the pieces of the structure are bound together in such a way that the mutual gravitational attraction is higher than the other forces they experience -- and given that a lot of these things are very far away, any such determination is bound to rest on some fairly thin ice.

The largest generally accepted cosmic structure is the Hercules-Corona Borealis Great Wall, a galactic filament that (from our perspective) is in the night sky in the Northern Hemisphere in spring and early summer.  It's ten billion light years in length -- making it a little over a tenth as long as the entire observable universe!

[Image licensed under the Creative Commons Pablo Carlos Budassi, Hercules-CoronaBorealisGreatWall, CC BY-SA 4.0]

In the above image, each one of the tiny dots of light is an entire galaxy containing billions of stars; the brighter blobs are galaxy clusters, each made up of millions of galaxies.

And the whole thing is bound together by gravity.

What's kind of overwhelming about this is that because there are these enormous cosmic structures, there are also gaps between them, called supervoids.  One of the largest is the Boötes Void.  This thing is 330 million light years across, and contains almost no matter at all; any given cubic meter of space inside the void might have a couple of hydrogen atoms, and that's about it.  To put it in perspective; if the Earth was sitting in the center of the Boötes Void, there wouldn't be a single star visible.  It wouldn't have been until the 1960s that we'd have had telescopes powerful enough to detect the nearest stars.

That, my friend, is a whole lot of nothing.

What's coolest about all this is where these structures (and the spaces between them) came from.  On the order of 10^-32 seconds (that's 0.00000000000000000000000000000001 seconds) after the Big Bang, the bizarre phenomenon of cosmic inflation had not only blown the universe up by an amount that beggars belief (estimates are that in that first fraction of a second, it expanded from the size of a proton to about the size of a galaxy), it also smoothed out any lumpy bits (what the cosmologists call anisotropies).  This is why the universe today is pretty smooth and homogeneous -- if you look out into space, you see on average the same number of galaxies no matter which way you look.

But there are some pretty damn big anisotropies, like the Hercules-Corona Borealis Great Wall and the Boötes Void.  So where did those come from?

The current model is that as inflation ended, an interaction between regular matter and dark matter triggered a shock wave through the plasma blob that at that point was the entire universe.  This shock wave -- a ripple, a pressure wave much like a sound wave propagating through the air -- pushed some bits of the regular matter closer together and pulled some bits apart, turning what had been a homogeneous plasma into a web of filaments, sheets... and voids.

These baryon acoustic oscillations, that occurred so soon after the Big Bang it's hard to even wrap my brain around a number that small, are why we now have cosmic structures millions, or billions, of light years across.

So that's our mindblowing science for today.  Gravitationally-linked structures that span one-tenth of the size of the observable universe, and spaces in between containing damn near nothing at all, all because of a ripple that passed through the universe when it was way under one second old.

If that doesn't make you realize that all of our trials and tribulations here on Earth are insignificant, nothing will.

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Here are the answers to the puzzles from yesterday's post.  If you haven't finished thinking about them on your own, scroll no further!

1.  The census taker puzzle

The first clue is that the product of the daughters' ages is equal to 36.  There are eight possible trios of numbers that multiply to 36: (1, 1, 36), (1, 2, 18), (1, 3, 12), (1, 4, 9), (1, 6, 6), (2, 2, 9), (2, 3, 6), and (3, 3, 4).  Clue #2 is that the ages sum to equal the house number across the street, so the next step is to figure out what the house number could be.  Respectively: 38, 21, 16, 14, 13, 13, 11, and 10.

The key here is that when the census taker looks at the house number across the street, he still can't figure it out.  So it can't be (1, 4, 9), for example -- because if it was, as soon as he saw that the house number was 14, he'd know that was the only possible answer.  The fact that even after seeing the house number, he still doesn't know the answer, means it has to be one of the two trios of numbers that sums to the same thing -- 13.  So it either has to be (1, 6, 6) or (2, 2, 9).

Then, clue #3 is that the man's oldest daughter has red hair.  In the first possibility, there is no oldest daughter -- the oldest children are twins.  So his daughters have to be a nine-year-old and a pair of two-year-old twins.

2.  The St. Ives riddle

The answer is one.  "As I was going to St. Ives..." -- it doesn't say a thing about where the other people he met were going, if anywhere.

3.  The bear

It's a white bear.  The only place on Earth you could walk a mile south, a mile east, and a mile north and end up back where you started is if your starting place was the North Pole.

4.  A curious sequence

The pattern is that it's the names of the single digit numbers in English, in alphabetical order.  So the next one in the sequence is 3.

5.  Classifying the letters

The letters are classified by their symmetry.  (The capital letters only, of course.)  Group 1 is symmetrical around a vertical line, Group 2 around a horizontal line, Group 3 is around either a horizontal or a vertical line, Group 4 has no line symmetry but is symmetrical through a 180-degree rotation around their central point, and Group 5 are asymmetrical.

6.  The light bulb puzzle

Turn on switch one, and leave it on.  Turn on switch two for ten minutes, then turn it off.  Leave switch three off.  Go up to the tenth floor.  The bulb operated by switch one will be on; the one operated by switch two will be dark, but hot; and the one operated by switch three will be dark and cold.

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Lateral thinking

One of the biggest impediments to clear thinking is the fact that it's so hard for us to keep in mind that we could be wrong.

As journalist Kathryn Schulz put it:

I asked you how it felt to be wrong, and you had answers like humiliating, frustrating, embarrassing, devastating.  And those are great answers.  But they're answers to a different question.  Those are answers to the question, "How does it feel to find out you're wrong?"  But being wrong?  Being wrong doesn't feel like anything...  You remember those characters on Saturday morning cartoons, the Coyote and the Roadrunner?  The Coyote was always doing things like running off a cliff, and when he'd do that, he'd run along for a while, not seeing that he was already over the edge.  It was only when he noticed it that he'd start to fall.  That's what being wrong is like before you've realized it.  You're already wrong, you're already in trouble...  So I should amend what I said earlier.  Being wrong does feel like something.

It feels like being right.

We cling desperately to the sense that we have it all figured out, that we're right about everything.  Oh, in theoretical terms we realize we're fallible; all of us can remember times we've been wrong.  But right here, right now?  It's like my college friend's quip, "I used to be conceited, but now I'm perfect."

The trouble with all this is that it blinds us to the errors that we do make, because if you don't keep at least trying to question your own answers, you won't see your own blunders.  It's why lateral thinking puzzles are so difficult, but so important; they force you to set aside the usual conventions of how puzzles are solved, and to question your own methods and intuitions at every step.  This was the subject of a study by Andrew Meyer (of the Chinese University of Hong Kong) and Shane Frederick (of Yale University) that appeared in the journal Cognition last week.  They looked at a standard lateral thinking puzzle, and tried to figure out how to get people to avoid falling into thinking their (usually incorrect) first intuition was right.

The puzzle was a simple computation problem:

A bat and a ball together cost $1.10.  The bat costs $1.00 more than the ball.  How much does the ball cost?

The most common error is simply to subtract the two, and to come up with ten cents as the cost of the ball.  But a quick check of the answer should show this can't be right.  If the bat costs a dollar and the ball costs ten cents, then the bat costs ninety cents more than the ball, not a dollar more (as the problem states).  The correct answer is that the ball costs $0.05 and the bat costs $1.05 -- the sum is $1.10, and the difference is an even dollar.

Meyer and Frederick tried different strategies for improving people's success.  Bolding the words "more than the ball" in the problem, to call attention to the salient point, had almost no effect at all.  Then they tried three different levels of warnings:

1. Be careful!  Many people miss this problem.
2. Be careful!  Many people miss the following problem because they do not take the time to check their answer.
3. Be careful!  Many people miss the following problem because they read it too quickly and actually answer a different question than the one that was asked.

All of these improved success, but not by as much as you might think.  The number of people who got the correct answer went up by only about ten percent, no matter which warning was used.

Then the researchers decided to be about as blatant as you can get, and put in a bolded statement, "HINT: The answer is NOT ten cents!"  This had the best improvement rate of all, but amazingly, still didn't eliminate all of the wrong answers.  Some people were so certain their intuition was right that they stuck to their guns -- apparently assuming that the researchers were deliberately trying to mislead them!

[Image licensed under the Creative Commons © Nevit Dilmen, Question mark 1, CC BY-SA 3.0]

If you find this tendency a little unsettling... well, you should.  It's one thing to stick to a demonstrably wrong answer in some silly hypothetical bat-and-ball problem; it's another thing entirely to cling to incorrect intuition or erroneous understanding when it affects how you live, how you act, how you vote.

It's why learning how to suspend judgment is so critical.  To be able to hold a question in your mind and not immediately jump to what seems like the "obvious answer" is one of the most important things there is.  I used to assign lateral thinking puzzles to my Critical Thinking students every so often -- I told them, "Think of these as mental calisthenics.  They're a way to exercise your problem-solving ability and look at problems from angles you might not think of right away.  Don't rush to find an answer; keep considering them until you're sure you're on the right track."

So I thought I'd throw a few of the more entertaining puzzles at you.  None of them involve much in the way of math (nothing past adding, subtracting, multiplying, and dividing), but all of them take an insight that requires pushing aside your first impression of how problems are solved.  Enjoy!  (I'll include the answers at the end of tomorrow's post, if any of them stump you.)

1.  The census taker problem

A census taker goes to a man's house, and asks for the ages of the man's three daughters.

"The product of their ages is 36," the man says.

The census taker replies, "That's not enough information to figure it out."

The man says, "Okay, well, the sum of their ages is equal to the house number across the street."

The census taker looks out of the window at the house across the street, and says, "I'm sorry, that's still not enough information to figure it out."

The man says, "Okay... my oldest daughter has red hair."

The census taker says, "Thank you," and writes down the ages.

How old are the three daughters?

2. The St. Ives riddle

The St. Ives riddle is a famous puzzle that goes back to (at least) the seventeenth century:

As I was going to St. Ives,
I met a man with seven wives.
Each wife had seven kids,
Each kid had seven cats,
Each cat had seven kits.
Kits, cats, kids, and wives, how many were going to St. Ives?

3.  The bear

A man goes for a walk.  He walks a mile south, a mile east, and a mile north, and after that is back where he started.  At that point, he sees a large bear rambling around.  What color is the bear?

4.  A curious sequence

What is the next number in this sequence: 8, 5, 4, 9, 1, 7, 6...

5.  Classifying the letters

You can classify the letters in the English alphabet as follows:

Group 1: A, M, T, U, V, W, Y

Group 2: B, C, D, E, K

Group 3: H, I, O, X

Group 4: N, S, Z

Group 5: F, G, J, L, P, Q, R

What's the reason for grouping them this way?

6.  The light bulb puzzle

At the top of a ten-story building are three ordinary incandescent light bulbs screwed into electrical sockets.  On the first floor are three switches, one for each bulb, but you don't know which switch turns on which bulb, and you can't see the bulbs (or their light) from the place where the switches are located.  How can you determine which switch operates which bulb... and only take a single trip from the first floor up to the tenth?

Have fun!

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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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