Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Saturday, July 11, 2020

Genes on loan

I wonder what the early pioneers of genetics -- people like Gregor Mendel, Thomas Hunt Morgan, Reginald Punnett, and William Bateson -- would think if they could peruse a modern genetics textbook.

My hope is that they'd be delighted beyond words at where the science has gone since their time.  The simple foundation laid down by the first geneticists has been elaborated and modified into a complex, far-reaching science that has explanatory power from the molecular level to the characteristics of the organisms themselves (the phenotypes, or physical expressions, of the genes).  And now, just over 150 years after the publication of Mendel's book on statistical genetics that showed that inheritance of traits followed natural laws and generated predictable statistics, we're still adding to what we know.

Take the paper that came out in Nature this week, that describes a fascinating exception to Mendel's Law of Independent Assortment (one of his four laws of statistical genetics).  The Law of Independent Assortment says that every gene inherits by its own separate statistics.  Put another way, genes don't inherit in chunks; each one is its own flip of the coin.  Here's an example:

Let's say your mom inherited a type A blood type gene and an Rh negative gene from her father, and a type B blood type gene and an Rh positive gene from her mother.  (This, by the way, would make her AB+.)  Now, she passed on to you her father's type A gene.  Which Rh gene did you get?

Answer: by the Law of Independent Assortment, there's no way to be sure. Knowing she passed on her father's type A gene doesn't make it any more likely you got her father's Rh negative gene; each gene operates by its own statistics, and the inheritance of one gene does not influence the inheritance of any other.

Well, we've known about some exceptions to that law for years; in fact, the aforementioned Bateson and Punnett were the ones who figured out what was going on with the discovery of linked genes, genes that lie near each other on the same chromosome.  In my earlier example, if the ABO blood type gene and the Rh+/- gene were close together on the same chromosome (they're not), then inheriting the A gene from her dad would make you more likely to also get the negative gene from her dad.  (You may be wondering why, if they're on the same chromosome, it doesn't make the likelihood of their inheriting together 100%; that's a whole 'nother topic, called crossing over, which I won't explain in this post because otherwise we'll never get to the recent research.)

The paper in Nature, called "Massive Haplotypes Underlie Ecotypic Differentiation in Sunflowers," by a huge team led by the trio of Marco Todesco, Gregory Owens, and Natalia Bercovich of the University of British Columbia, describes how the inheritance of huge chunks of DNA -- hundreds of millions of base pairs long, inherited as a single block -- has allowed related species of sunflowers to grab beneficial traits from each other and triggered differentiation and, ultimately, the formation of new species.

[Image is in the Public Domain]

The authors write:
Species often include multiple ecotypes that are adapted to different environments.  However, it is unclear how ecotypes arise and how their distinctive combinations of adaptive alleles are maintained despite hybridization with non-adapted populations.  Here, by resequencing 1,506 wild sunflowers from 3 species (Helianthus annuus, Helianthus petiolaris and Helianthus argophyllus), we identify 37 large (1–100 Mbp in size), non-recombining haplotype blocks that are associated with numerous ecologically relevant traits, as well as soil and climate characteristics.  Limited recombination in these haplotype blocks keeps adaptive alleles together, and these regions differentiate sunflower ecotypes.  For example, haplotype blocks control a 77-day difference in flowering between ecotypes of the silverleaf sunflower H. argophyllus (probably through deletion of a homologue of FLOWERING LOCUS T (FT)), and are associated with seed size, flowering time and soil fertility in dune-adapted sunflowers.  These haplotypes are highly divergent, frequently associated with structural variants and often appear to represent introgressions from other—possibly now-extinct—congeners. These results highlight a pervasive role of structural variation in ecotypic adaptation.
Catch that last bit?  Some of these "supergenes," as they're called, could have come from now-extinct species, whose DNA still exists and is still influencing the evolution of a different species.  How cool is that?

"What we think could have happened is that a species arrives in a new habitat, 'steals' adaptive supergenes from a local related species, and then replaces that species," said study co-lead author Marco Todesco, in an interview with Science Daily.  "We could call this a 'ghost supergene', the lingering contribution of a species that no longer exist."

How Gregor Mendel and the pioneers that followed would have been fascinated by all this!  We've come a tremendously long way from Mendel's mysterious "factors" (what we now call alleles) and the simplistic probabilities that generate the inheritance of flower color in pea plants.  Even the linked genes of Bateson and Punnett now seem like only the prologue to the story.

And what's more mindblowing still is that to geneticists in a hundred years hence, even what we know now will still probably only be chapter one.

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Friday, July 10, 2020

Big voices

One of the funniest scenes in the Monty Python movie Life of Brian is when a man is condemned to be stoned for saying "Jehovah," and the High Priest (played by John Cleese) is facing a crowd which is already armed with stones, ready to carry out the sentence.  The crowd, unbeknownst to the High Priest, is made up of women (who by law are forbidden from being there), and it's even funnier because that means the crowd was men playing women who were pretending they were men.

Well, at one point in the proceedings, the High Priest says the word "Jehovah" and gets clunked in the head by a rock.  He then demands to know who threw the rock.

A chorus of high-pitched, pseudo-feminine voices shouts, "She did!  She did!  She did!... um...."  (continuing in deeper, masculine voices)  "He did!  He did!  He did!"


This was the first thing my rather loopy brain thought of when I read a paper yesterday in Biology Letters.  In "Acoustic Allometry and Vocal Learning in Mammals," by Maxime Garcia (of the University of Zurich) and Andrea Ravignani (of the Max Planck Institute for Psycholinguistics), we find out that "dishonest signaling" -- using a voice that makes you sound bigger or more threatening than you actually are -- has been found in dozens of mammalian species.

The authors write:
Vocal production learning (VPL) can be defined as the experience-driven ability, rare among mammals, to modify existing vocalizations, to produce novel sounds or to imitate sounds that do not belong to an individual's vocal repertoire...  VPL inherently involves modulation of acoustic features related to the source, filter or both.  Yet, different species have varying degrees of control over the anatomical components involved in phonation.  For instance, despite a generally assumed lack of vocal control some non-human primates might have limited sound production plasticity, including for non-voiced sounds.  While the presence of VPL in non-human primates is debated, strong evidence for VPL has been found to date in humans and four other mammalian clades: non-otariid Pinnipedia, Elephantidae, Chiroptera and Cetacea.
"If you saw a Chihuahua barking as deep as a Rottweiler, you would definitely be surprised," said study co-author Andrea Ravignani, in an interview with Science Daily.  "Nature is full of animals like squeaky-Rottweilers and tenor-Chihuahuas...  Some animals fake their size by developing larger vocal organs that lower their sound, which makes them sound larger than you would expect.  Other animals are good at controlling the sounds they produce.  Such strategies -- 'dishonest signaling' -- could be driven by sexual selection, as males with larger body size or superior singing skills (hitting very high or low notes) attract more females (or vice versa)."

I know one good example of little animal/big voice from my own back yard -- the Carolina Wren (Thryothorus ludovicianus).  It's a tiny thing, what birders call an "LBJ" (Little Brown Job), but its outsized shriek of "TEAKETTLE TEAKETTLE TEAKETTLE" frequently wakes me up at four in the morning during the spring and early summer, especially given that there's one of 'em who likes to sing from the branches of the box elder tree right outside my bedroom window.  But this is volume, not pitch.  For misleading pitch, there's none that can compete -- at least in the bird world -- with the Great Potoo (Nyctibius grandis) of the rainforests of South America.  Take a listen to this:


Since this bird is nocturnal, and (as you can see) is very cryptically colored, a lot of the natives didn't realize that sound was a bird for a long time.  Their explanation -- that there was a horrible monster out there in the forest roaming around at night -- is completely understandable, given what its vocalizations sound like.

So the capacity to create misleading sounds isn't the sole provenance of the Monty Python crew's fake falsettos.  There are lots of animal species that do the same thing, either to frighten off potential predators or to sound sexier for potential mates.

Or, perhaps, to give a misleading answer to questions like, "Are there any women here today?... good, very well then."

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Thursday, July 9, 2020

Reptilian splits

One of my favorite lectures in my AP Biology class was about how there's no such thing as a reptile.

If you took your last biology class before about 1995, you probably learned about Class Reptilia, containing turtles, lizards, snakes, crocodiles, alligators, and a few other assorted groups.  The class was defined by having dry, scaly skin, internal fertilization, "amniote" eggs with shells, and hearts that had incomplete septa (the wall down the center that separates the oxygenated left side from the deoxygenated right side).

Well, the last one wasn't 100% true, and that should have been a clue to what was going on.  Crocodiles and alligators have four-chambered hearts, and are also partial endotherms -- they show some capacity for internally regulating their own body temperatures, just as birds and mammals do.

It was genetic testing that finally settled who was related to whom, and that was when a lot of us got a shock (not so much the evolutionary biologists, who kind of expected this was how it was gonna work out).  The word "reptile" has no real taxonomic significance, because it lumps together groups that really aren't very closely related, and excludes others that are closer.  Here's how this branch of Kingdom Animalia evolved:


As you can see from the diagram, the problem was birds.  Crocodiles are more closely related to birds than they are to lizards (despite superficial appearance); and if you throw dinosaurs into the mix, it becomes even clearer, because birds are dinosaurs.

Think about that the next time you feed the chickadees.

So if you throw all the reptiles together, by the rules of cladistic taxonomy, you'd have to include birds, and nobody much wanted to call birds reptiles.  So the entire Class Reptilia was broken up, now as three different classes: Lepidosauria (lizards, snakes, and the oddball tuatara of New Zealand), Testudines (turtles), and Crocodilia (obviously crocodiles et al.).  Birds have their own class (Aves).

But what this brings up is how such different-looking animals as turtles and snakes evolved from a common ancestor.  The differences between the different groups of reptiles is pretty dramatic.  The explanation has usually been that it was adaptive radiation, a phenomenon that deserves some explanation.

Adaptive radiation is when a group undergoes rapid diversification to fill many available niches.  The classic example is Darwin's finches, a group of birds on the Galapagos Islands, which descend from a common ancestral group that split up to occupy different niches because of bill size and strength (which determines what they can eat).  That's a pretty drastic oversimplification, but it captures the essence: many available niches, and a population with sufficient genetic diversity to split up and specialize into those niches.

Because of the "many available niches" part, adaptive radiation is most common under two scenarios: a population colonizing a previously-uninhabited territory (as with Darwin's finches), and remnant populations left after a major extinction.  This was what was thought to have powered the split-up of the reptiles -- the "Great Dying," the Permian-Triassic extinction of 252 million years ago that by some estimates wiped out 95% of life on Earth.

Nota bene: there is fairly good evidence that the trigger for the Permian-Triassic extinction was hypercapnia -- a sudden increase in atmospheric carbon dioxide.  This led to drastic warming of the atmosphere and ocean acidification.  The cause -- according to a paper that just came out two weeks ago in the journal Geology -- was massive burning of coal.  Sound familiar?  In this case the cause was natural; it's thought to have been triggered by massive volcanism.  But the end result was the same as what we're doing now by runaway use of fossil fuels.  I'd like to think this would be a cautionary note, but the world's leaders seem to specialize in ignoring science unless it can directly make them money and/or keep them in power, so I'm not holding my breath.

But back to the reptiles.  The study that triggered this post, which came out this week in Nature Communications, points out the flaw in the argument that the adaptive radiation of reptiles was due to the Permian-Triassic extinction.  According to recent analysis, the split up was already well underway before the extinction started.  And the extinction itself was sudden, at least in geological terms; from start to catastrophic finish, the whole event took about a hundred thousand years.  In geological strata, this length of time is a very, very narrow band.

Plus, the different groups of reptiles individually show drastically different rates of specialization. "Our findings suggest that the origin of the major reptile groups, both living and extinct, was marked by very fast rates of anatomical change, but that high rates of evolution do not necessarily align with taxonomic diversification," said study lead author Tiago Simões of Harvard University, in an interview in Phys.Org.  "Our results also show that the origin of snakes is characterized by the fastest rates of anatomical change in the history of reptile evolution -- but that this does not coincide with increases in taxonomic diversity [as predicted by adaptive radiations] or high rates of molecular evolution."

The end result of the study is that the cause of the adaptive radiation is unknown.  It probably was pushed along by the mass extinction -- the species that survived the hypercapnia and the resulting environmental devastation were set up to have a whole empty world to colonize.  But what was driving the split-up of the group prior to the extinction itself?

Unknown, but the current study shows that clearly the adaptive radiation had already started.

I love puzzles like this.  In science, there are almost always more questions than answers, and every answer brings up new questions.  But another feature of science is the conviction that there is an answer even if we don't currently know what it is.  And chances are, further study will elucidate what exactly was going on -- and what led to the fragmentation of a group that now, over 250 million years later, comprises some of the best-known and most familiar critters who have ever walked (or flown across) the Earth.

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Wednesday, July 8, 2020

Cause and effect

In 1960, Carl Jung coined the term synchronicity in his book of the same name, and defined it as follows:
How are we to recognize acausal combinations of events, since it is obviously impossible to examine all chance happenings for their causality?  The answer to this is that acausal events may be expected most readily where, on closer reflection, a causal connection appears to be inconceivable...  It is impossible, with our present resources, to explain ESP [extrasensory perception], or the fact of meaningful coincidence, as a phenomenon of energy.  This makes an end of the causal explanation as well, for "effect" cannot be understood as anything except a phenomenon of energy.  Therefore it cannot be a question of cause and effect, but of a falling together in time, a kind of simultaneity.  Because of this quality of simultaneity, I have picked on the term "synchronicity" to designate a hypothetical factor equal in rank to causality as a principle of explanation.
Synchronicity is a peculiar thing, and when it happens to us it can be extremely startling.  I recall going to a doctor's appointment one day, and in the car I was listening to a station that plays classical music.  When I arrived I was in the middle of the first movement of Beethoven's Moonlight Sonata, a piece I love -- but I was right on time for the appointment and couldn't sit and listen to the rest of it.

So I shut the engine off, got out of my car, and went into the doctors' office.  I checked in, went to the waiting room...

... and over the speakers came the ethereal notes of the piano playing the first movement of the Moonlight Sonata, picking up almost exactly where I had left off five minutes earlier.

This would have been surprising but not really all that peculiar if they had simply been tuned to the same station on Sirius-XM satellite radio as I was; but they weren't.  As I found out from sitting there for the next half hour (just because I was on time for my appointment doesn't mean the doctor was), the music being piped in was just a collection of "atmospheric piano music" for waiting rooms and the like.  The fact that it seemed to pick up exactly where I'd turned the radio in my car off was pure coincidence.

Or, if you like Jung's term, synchronicity.  I'm wary of it for two reasons.  First, it immediately turns on our conviction that occurrences like this Mean Something, that it was more than simple random chance at work.  Second, this kind of magical thinking is at the heart of dart-thrower's bias -- our tendency to notice (or overemphasize) the hits and ignore the misses.  In this case, all of the millions of times I've walked into a waiting room or elevator or grocery store and the speakers weren't playing a tune I was just listening to or thinking about.  All of that randomness gets subsumed into the background white noise of life.  I only noticed it this time, and remembered it afterward, because the music I heard was unexpected in some way.

The reason this comes up is because of an article at Insider about a phone app called "Randonautica," which takes the concept of synchronicity to new levels.  What the app does is to give you a random set of coordinates within a ten minute drive of your home, and then acts as a GPS to get you there.  Before you leave, you're supposed to "set an intention" -- something you want to find or learn when you arrive -- with the expectation that at the site, you'll discover something relevant to that intention.

Various "Randonauts" have reported all sorts of things -- creepy abandoned buildings, unexpected beautiful spots hidden away from view, cryptic graffiti on walls that seemed in some way to connect to the seekers' intention, and so on.  One group had a horrifying experience; Randonauts in Seattle stumbled upon a suitcase that contained human remains in a plastic garbage bag.

Now, I'm not trying to rain on anyone's parade (although finding a dead body certainly would quell my enthusiasm for the whole enterprise).  I can see how Randonautica could be a great deal of fun, and in fact, it's related in spirit to a hobby my wife and I both participate in, geocaching.  But it's an interesting question to consider whether what the Randonauts are finding is meaningful.

My take on it is that sure, it's meaningful, but the meaning is something the Randonauts are imposing upon what they find.  Put another way, there's nothing mystical to this; if you go to a strange place and look for something, with the only criterion being that it has to be relevant to a broad intention to "find something strange," then you're almost certain to succeed.  I can pretty much guarantee that no matter where you go, if you look for weird and unexpected stuff, you'll find something.

But that's just me being a hyperrational type, and there are people who absolutely swear by synchronicities that even I would find a little hard to explain as dart-thrower's bias.  Jung, for example, told the story of a patient who had a vivid dream of a golden scarab beetle, and asked him what relevance it had to her life.  While she was telling him this, he heard a noise, and saw there was an insect trying to get out of the window -- and reached out his hand and caught it.  Guess what it was?  He handed the shining green-gold beetle to the patient, and said, "Here is your scarab."

"This experience punctured the desired hole in her rationalism and broke the ice of her intellectual resistance," Jung wrote.  "The treatment could now be continued with satisfactory results."

[Image is in the Public Domain]

So who knows?  Maybe there's more to this than I'm seeing.  I'd encourage you to try Randonautica if you're so inclined, and let me know if anything untoward happens.  I may well do the same -- although I wonder what would happen if your intention contains the subclause, "... but there's probably nothing mystical going on here."

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Tuesday, July 7, 2020

Water worlds

Water is one of those things that seems ordinary until you start looking into it.

The subject always puts me in mind of the deeply poignant Doctor Who episode "The Waters of Mars," which has to be in my top five favorite episodes ever.  (If you haven't seen it, you definitely need to, even if you're not a fanatical Whovian like I am -- but be ready for the three-boxes-of-kleenex ending.)  Without giving you any spoilers, let's just say that the Mars colonists shouldn't have decided to use thawed water from glaciers for their drinking supply.

Once things start going sideways, the Doctor warns the captain of the mission, Adelaide Brooke, that trying to fight what's happening is a losing battle, and says it in a truly shiver-inducing way: "Water is patient, Adelaide.  Water just waits.  Wears down the cliff tops, the mountains.  The whole of the world.  Water always wins."


Even beyond science fiction, water has some bizarre properties.  It's one of the only substances that gets less dense when you freeze it -- if water was like 99% of the compounds in the world, ice would sink, and lakes and oceans would freeze from the bottom up.  Compared to most other liquids, it has a sky-high specific heat (ability to absorb heat energy without much increase in temperature) and heat of vaporization (the heat energy required for it to evaporate), both of which act not only to allow our body temperature easier to regulate, it makes climates near bodies of water warmer in winter and cooler in summer than it otherwise would be.  It's cohesive, which is the key to how water can be transported a hundred meters up the trunk of a redwood tree, and is also why a bellyflop hurts like a mofo.  It's highly polar -- the molecules have a negatively-charged side and a positively-charged side -- making it an outstanding solvent for other polar compounds (and indirectly leading to several of the other properties I've mentioned).

And those are the characteristics water has at ordinary temperatures and pressures.  If you start changing either or both of these, things get weirder still.  In fact, the whole reason the topic comes up is because of a paper in Astrophysical Journal Letters this week called "Irradiated Ocean Planets Bridge Super-Earth and Sub-Neptune Populations," by astrophysicist Olivier Mousis of Aix-Marseille University, about a very strange class of planets where water is in a bizarre state where it's not quite a liquid and not quite a gas.

This state is called being supercritical -- where a fluid can seep through solids like a gas but dissolve materials like a liquid.  For water, the critical point is about 340 C and a pressure 217 times the average atmospheric pressure at sea level -- so nothing you'll run into under ordinary circumstances.  This weird fluid has a density about a third that of liquid water at room temperature -- way more dense than your typical gas and way less than your typical liquid.

Mousis et al. have found that some of the "sub-Neptune" exoplanets that have been discovered recently are close enough to their parent stars to have a rocky core surrounded by supercritical water and a steam-bath upper atmosphere -- truly a strange new kind of world even the science fiction writers don't seem to have anticipated.  One of these exoplanets -- K2 18b, which orbits a red dwarf star about 110 light years from Earth -- fits the bill perfectly, and in fact mass and diameter measurements suggest it could be made up of as much as 37% water.

So there you are -- some strange features of a substance we all think we know.  Odd stuff, water, however familiar it is.  Even if you don't count the extraterrestrial contaminants that Captain Brooke and her crew had to contend with.

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Monday, July 6, 2020

Moonstruck

A lot of times, it's the simple, easily-stated questions that are the hardest to answer.

Take, for example, the question of how the Moon formed.  Satellites around planets are common -- Jupiter has 79, for example -- but our own is a bit of an anomaly.  For example, if you make a list of moons in the Solar System in order of mass with respect to its host planet, the Earth's Moon is way out in front.  Its mass is 0.0123 of the Earth's.  Next in line would be Titan, which has a moon mass to planet mass ratio fifty times smaller (0.000237).

It's easy to picture a planet the size of Jupiter or Saturn gravitationally capturing blobs of the coalescing matter during the Solar System's formation, but it's harder to see a small planet like the Earth having the gravitational oomph to snag something the size of the Moon.  Another oddity is that of the sixteen most massive moons in the Solar System, the Moon's orbit around the Earth is by far the most eccentric.  Eccentricity is a number between zero and one that indicates how elliptical an orbit is, with 0.000 eccentricity being a perfect circle.  The Moon's deviation from a circular orbit is twice the next contender (which is once again Titan; whether that's a coincidence or not isn't known).  But the elliptical nature of the Moon's orbit is why its apparent size from Earth fluctuates, and explains why when there's a solar eclipse, sometimes it's total (complete coverage of the Sun's disk) and sometimes it's annular (occurs when the Moon is farther away and has a smaller apparent size, so at totality there's a ring of the Sun's disk still visible).

A third peculiarity of the Moon only became apparent when scientists got their first views of the far-Earth side around 1960, and they discovered that the far side had few maria -- the darker regions that were named for the Latin word for sea because it was thought early on that they might be water-filled oceans.  The largest two, the Oceanus Procellarum (Ocean of Storms) and the Mare Imbrium (Sea of Showers) together cover about 10% of the near-side disk of the Moon, and given that they're dotted with impact craters they seem to be very old structures.  (The first Apollo manned landing, in 1969 in the Mare Tranquillitatis (Sea of Tranquility), showed that the darkness of the maria is due to their being made largely of the dark volcanic rock basalt.)

[Image is licensed under the Creative Commons Gregory H. Revera, FullMoon2010, CC BY-SA 3.0]

So something odd is going on here, but a research team headed by geophysicist Stephen Elardo of the University of Florida has come up with a compelling answer to at least one piece of it.  The best hypothesis for the formation of the Moon, the researchers say, is the head-on collision of two protoplanets, one about ten times larger than the other (the smaller is estimated to be about the size of Mars).

Wouldn't that have been something to see?  From a safe distance?

In any case, this colossal collision blew both planets to smithereens, creating a whirling cloud of white-hot rocks and dust.  When the debris cooled and re-coalesced, the heavier one (eventually the Earth) had a high enough gravity to sort out the mess and pull the denser elements, like nickel and iron, into the core.  The lighter one (eventually the Moon) didn't, so it was left asymmetrical, with one side enriched in uranium, thorium, and the elements collectively called KREEP (potassium [symbol K], the Rare Earth Elements [such as cerium, lanthanum, dysprosium, and yttrium], and phosphorus [symbol P]).  This combo is what created the maria.  Uranium and thorium are radioactive, and as they decay, they release heat.  One effect of rocks being enriched in KREEP elements is that it lowers their melting point.  This meant that the surface remained liquid much longer -- becoming the flat, dark basalt plains we now can see from Earth.  The other side, being much lower in uranium, thorium, and KREEP, froze solid very early, and the landscape largely lacks maria.

"Because of the relative lack of erosion processes, the Moon's surface records geological events from the Solar System's early history," said study co-author Matthieu Laneuville, geophysicist at the Tokyo Institute of Technology, in an interview with ScienceDaily.   "In particular, regions on the Moon's near side have concentrations of radioactive elements like uranium and thorium unlike anywhere else on the Moon.  Understanding the origin of these local uranium and thorium enrichments can help explain the early stages of the Moon's formation and, as a consequence, conditions on the early Earth."

So that's one piece of the puzzle.  It brings up other questions, though, such as whether the fact that all this happened on the near-Earth side is a coincidence or was driven by something about the collision that formed the Earth-Moon system.  But whatever the answer to that is, the whole topic is fascinating -- and the violence of our satellite's origin is something to remember the next time you're looking up on a clear, peaceful moonlit night.

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This week's Skeptophilia book recommendation of the week is for anyone who likes quick, incisive takes on scientific topics: When Einstein Walked with Gödel: Excursions to the Edge of Thought by the talented science writer Jim Holt.

When Einstein Walked with Gödel is a series of essays that explores some of the deepest and most perplexing topics humanity has ever investigated -- the nature of time, the implications of relativity, string theory, and quantum mechanics, the perception of beauty in mathematics, and the ultimate fate of the universe.  Holt's lucid style brings these difficult ideas to the layperson without blunting their scientific rigor, and you'll come away with a perspective on the bizarre and mind-boggling farthest reaches of science.  Along the way you'll meet some of the key players in this ongoing effort -- the brilliant, eccentric, and fascinating scientists themselves.

It's a wonderful read, and anyone who is an aficionado of the sciences shouldn't miss it.

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




Saturday, July 4, 2020

Through the looking glass

Regular readers of Skeptophilia may remember that a couple of weeks ago, I attempted to write a post on the odd superstitions surrounding mirrors, but got sidetracked over and over.

In a curious almost-synchronicity, today I ran into an article about how artificial intelligence can learn how to detect mirror-reversed images, even when they don't have such obvious cues as text to go by.  So I figured I ought to give another shot at addressing the topic of mirrors, more seriously this time.

Mirror reversal is a peculiar phenomenon, and I recall when I was in introductory physics in college and we were studying the optics of mirrors and lenses, I spent an inordinate amount of time trying to figure out why a flat mirror reverses an image right-to-left but not top-to-bottom.

The answer, which many of you probably already know, is that mirrors don't reverse right-to-left, exactly; they reverse back-to-front.  This has the effect of a right/left reversal because it's like you're looking at the object from the other side (imagine the object in question was transparent, but you could still see its contours, and the reasoning becomes easier).

Look, I can prove it to you.  Stand in front of a mirror.  What it seems like is that there is another person who looks exactly like you standing behind a clear piece of glass, at the same distance from the glass as yourself and facing you.  Now, think about what it would be like if you were to join him/her -- go behind the mirror.  To get there, you would have to walk behind the glass and turn 180 degrees about the vertical axis to face you.  If you did that, your left hand would be opposite his/her right hand, and vice versa.  What actually happened is that your reflection didn't do a 180 degree turn.  It was reversed front to back with no rotation at all.  You're seeing yourself not so much reversed as turned inside-out.

Interestingly, there is a mirror that reverses objects top to bottom -- a concave mirror.  It also creates an image that appears to be in front of the mirror, not behind it, and in the right setup, the image seems to be floating in space (which is why the physicists call concave mirror images "real images," and ones that are behind the mirror -- as in flat and convex mirrors -- "virtual images").

[Image is in the Public Domain]

Whether concave mirrors reverse text is left as an exercise for the reader.

But what brought me to the subject of mirrors (again -- although my first attempt was pretty pathetic) is the paper "Visual Chirality," by Zhiqiu Lin, Jin Sun, Abe Davis, and Noah Snavely, of Cornell University, which was presented at the 2020 Conference on Computer Vision and Pattern Recognition.  What the researchers did was to use a trainable artificial intelligence program to analyze images, some of which were mirror-reversed and others which were not, to see if it was possible to determine reversal without using such giveaways as text, analog clocks, and so on.

And they got pretty good at it.  Some of the cues it picked up on were of the "oh, yeah, of course" type, such as looking at where the buttons were on a button-down shirt.  (Buttons tend to be on the right side -- although years ago women's shirts used to button from the other side, most shirts for either gender now usually have the buttons on the right.)  Wristwatches were also a giveaway, even when the faces weren't visible; most people wear them on the left wrist.  People carrying phones usually had them in their right hands, probably attributable to the fact that between seventy and eighty percent of us are right-handed.

But there were some curious ones.  Turns out the algorithm figured out that when people are in face-forward photographs but not looking directly at the camera, they usually gaze to the left.  Men with facial hair also were easy for the software to pick out when reversed -- the researchers suspect it has something to do with the way men trim their beards (perhaps also connected to using the right versus the left hand to do so), but what exactly the algorithm was picking up on, the researchers aren't certain.

"It’s a form of visual discovery," said study co-author Noah Snavely.  "If you can run machine learning at scale on millions and millions of images, maybe you can start to discover new facts about the world."

After training, the algorithm was getting the answer right eighty percent of the time even when all the obvious giveaways were removed -- not a bad score.  The study has applications in the analysis of images, and detection of when those images have been doctored or altered.

What it puts me in mind of is the facial asymmetry that most humans have, something well-known to portrait artists.  Take a sheet of paper, and stand in front of your bathroom mirror.  Relax your facial muscles -- try for a neutral expression -- and cover up first one, then the other, half of your face with the paper.  You'll be surprised at how different they look -- angle of the mouth, position of the eyebrows, and so on can vary greatly.  (There was an interesting study a while back that correlated facial symmetry with our perception of beauty -- and found that of the people tested, Denzel Washington had the most perfectly symmetrical face.  It may be that symmetry is an indication of freedom from some genetic flaws that influence skeletal development -- making symmetrical people good bets for producing healthy children -- but that, of course, is speculation.)

Anyhow, it's an interesting finding.  But I'm definitely going to pay more attention next time I trim my facial hair.

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This week's Skeptophilia book recommendation of the week is pure fun, and a great gift for any of your friends who are cryptid fanciers: Graham Roumieu's hilarious Me Write Book: It Bigfoot Memoir.

In this short but hysterically funny book, we find out from the Big Guy's own mouth how hard it is to have the reputation for being huge, hairy, and bad-smelling.  Okay, even he admits he doesn't smell great, but it's not his fault, as showers aren't common out in the wilderness.  And think about the effect this has on his self-image, not to mention his success rate of advertising in the "Personals" section of the newspaper.

So read this first-person account of the struggles of this hirsute Everyman, and maybe even next time you're out hiking, bring along a little something for our australopithecene distant cousin.

He's very fond of peach schnapps.

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