Timey-wimey light

I don't always need to understand things to appreciate them.

In fact, there's a part of me that likes having my mind blown.  I find it reassuring that the universe is way bigger and more complex than I am, and the fact that I actually can parse a bit of it with my little tiny mind is astonishing and cool.  How could it possibly be surprising that there's so much more out there than the fragment of it I can comprehend?

This explains my love for twisty, complicated fiction, in which you're not handed all the answers and everything doesn't get wrapped up with a neat bow at the end.  It's why I thoroughly enjoyed the last season of Doctor Who, the six-part story arc called "Flux."  Apparently it pissed a lot of fans off because it had a quirky, complicated plot that left a bunch of loose ends, but I loved that.  (I'm also kind of in love with Jodie Whittaker's Thirteenth Doctor, but that's another matter.)

I don't feel like I need all the answers.  I'm not only fine with having to piece together what exactly happened to whom, but I'm okay that sometimes I don't know.  You just have to accept that even with all the information right there in front of you, it's still not enough to figure everything out.

Because, after all, that's how the universe itself is.

[Nota bene: Please don't @ me about how much you hated Flux, or how I'm crediting Doctor Who showrunner Chris Chibnall with way too much cleverness by comparing his work to the very nature of the universe.  For one thing, you're not going to change my mind.  For another, I can't be arsed to argue about a matter of taste.  Thanks.]

In any case, back to actual science.  That sense of reality being so weird and complicated that it's beyond my grasp is why I keep coming back to the topic of quantum physics.  It is so bizarrely counterintuitive that a lot of laypeople hear about it, scoff, and say, "Okay, that can't be real."  The problem with the scoffers is that although sometimes we're not even sure what the predictions of quantum mechanics mean, they are superbly accurate.  It's one of the most thoroughly tested scientific models in existence, and it has passed every test.  There are measurements made using the quantum model that have been demonstrated to align with the predictions to the tenth decimal place.

That's a level of accuracy you find almost nowhere else in science.

The reason all this wild stuff comes up is because of a pair of papers (both still in peer review) that claim to have demonstrated something damn near incomprehensible -- the researchers say they have successfully split a photon and then triggered half of it to move backwards in time.

One of the biggest mysteries in physics is the question of the "arrow of time," a conundrum about which I wrote in some detail earlier this year.  The gist of the problem -- and I refer you to the post I linked if you want more information -- is that the vast majority of the equations of physics are time-reversible.  They work equally well backwards and forwards.  A simple example is that if you drop a ball with zero initial velocity, it will reach a speed of 9.8 meters per second after one second; if you toss a ball upward with an initial velocity of 9.8 meters per second, after one second it will have decelerated to a velocity of zero.  If you had a film clip of the two trajectories, the first one would look exactly like the second one running backwards, and vice versa; the physics works the same forwards as in reverse.

The question, then, is why is this so different from our experience?  We remember the past and don't know the future.  The physicists tell us that time is reversible, but it sure as hell seems irreversible to us.  If you see a ball falling, you don't think, "Hey, you know, that could be a ball thrown upward with time running backwards."  (Well, I do sometimes, but most people don't.)  The whole thing bothered Einstein no end.  "The distinction between past, present, and future," he said, "is only an illusion, albeit a stubbornly persistent one."

This skew between our day-to-day experience and what the equations of physics describe is why the recent papers are so fascinating.  What the researchers did was to take a photon, split it, and allow the two halves to travel through a crystal.  During its travels, one half had its polarity reversed.  When the two pieces were recombined, it produced an interference pattern -- a pattern of light and dark stripes -- only possible, the physicists say, if the reversed-polarity photon had actually been traveling backwards in time as it traveled forwards in space.

The scientists write:

In the macroscopic world, time is intrinsically asymmetric, flowing in a specific direction, from past to future.  However, the same is not necessarily true for quantum systems, as some quantum processes produce valid quantum evolutions under time reversal.  Supposing that such processes can be probed in both time directions, we can also consider quantum processes probed in a coherent superposition of forwards and backwards time directions.  This yields a broader class of quantum processes than the ones considered so far in the literature, including those with indefinite causal order.  In this work, we demonstrate for the first time an operation belonging to this new class: the quantum time flip.

This takes wibbly-wobbly-timey-wimey to a whole new level.

Do I really understand what happened here on a technical level?  Hell no.  But whatever it is, it's cool.  It shows us that our intuition about how things work is wildly and fundamentally incomplete.  And I, for one, love that.  It's amazing that not only are there things out there in the universe that are bafflingly weird, we're actually making some inroads into figuring them out.

To quote the eminent physicist Richard Feynman, "I can live with doubt and uncertainty and not knowing.  I think it's much more interesting to live not knowing than to have answers which might be wrong.  I have approximate answers and possible beliefs and different degrees of certainty about different things, but I'm not absolutely sure about anything."

To which I can only say: precisely.  (Thanks to the wonderful Facebook pages Thinking is Power and Mensa Saskatchewan for throwing this quote my way -- if you're on Facebook, you should immediately follow them.  They post amazing stuff like this every day.)

I'm afraid I am, and will always be, a dilettante.  There are only a handful of subjects about which I feel any degree of confidence in my depth of comprehension.  But that's okay.  I make up for my lack of specialization by being eternally inquisitive, and honestly, I think that's more fun anyhow.

 Three hundreds years ago, we didn't know atoms existed.  It was only in the early twentieth century that we figured out their structure, and that they aren't the little solid unbreakable spheres we thought they were.  (That concept is still locked into the word "atom" -- it comes from a Greek word meaning "can't be cut.")  Since then, we've delved deeper and deeper into the weird world of the very small, and what we're finding boggles the mind.  My intuition is that if you think it's gotten as strange as it can get, you haven't seen nothin' yet.

I, for one, can't wait.

****************************************

It's all becoming clear

The phenomenon of transparency is way more interesting than it appears at first.

I remember thinking about the concept when I was a kid, the first time I watched the classic horror/science fiction film The Invisible Man.  Coincidentally, I was in high school and was in the middle of taking biology, and we'd recently learned how the human eye works, and Claude Rains's predicament took on an added layer of difficulty when it occurred to me that if he was invisible -- including his retina -- not only would we not be able to see him, he wouldn't be able to see anything, because the light rays striking his eye would pass right through it.  Since it's light being absorbed by the retina that stimulates the optic nerve, and Rains's retinas weren't absorbing any light (or we'd have seen them floating in the air, which is kind of a gross mental image), he'd have been blind.

So an invisibility potion isn't nearly as fun an idea as it sounds at first.

It wasn't until I took physics that I learned why some objects are transparent, and why (for example) it's harder to see a glass marble underwater than it is in the air.  Transparency results from a molecular structure that neither appreciably absorbs nor scatters light; more specifically, when the substance in question has electron orbitals spaced so that they can't absorb light in the visible region of the spectrum.  (If not, the light passes right through it.)  Note that substances can be transparent in some frequency ranges and not others; water, for example, is largely transparent in visible light, but is opaque in the microwave region -- which is why water heats up so quickly when you put it in a microwave oven.

The second bit, though, is where it really gets interesting.  Why are some transparent objects still clearly visible, and others are nearly invisible?  Consider my example of glass in air as compared to glass under water.  You can see through both, but it's much harder to discern the outlines of the glass underwater than it is in air.  Even more strikingly -- submerge a glass object in a colorless oil, and it seems to vanish entirely.

The reason is something called the index of refraction -- how much a beam of light is bent when it passes from one transparent medium to another.  A vacuum has, by definition, an index of refraction of exactly 1.  Air is slightly higher -- 1.000293, give or take -- while pure water is about 1.333.  The key here is that the more different the two indices are, the more light bends when crossing from one to the other (and the more the light tends to reflect from the surface rather than refract).  This is why the boundary between air and water is pretty obvious (and why those amazing photographs of crystal-clear lakes, where you can see all the way to the bottom and boats appear to be floating, are always taken from directly overhead, looking straight down; even at a slight angle from perpendicular, you'd see the reflected portion of the light and the water's surface would be clearly visible).

Likewise, the more similar the indices of refraction are, the less light bends (and reflects) at the boundary, and the harder it is to see the interface.  Glass, depending on the type, has an index of refraction of about 1.5; olive oil has an index of 1.47.  Submerge a colorless glass marble in a bottle of olive oil, and it seems to disappear,

The reason all this comes up has to do with the evolution of transparency in nature -- as camouflage.  It's a pretty clever idea, that, and is used by a good many oceanic organisms (jellyfish being the obvious example).  None of them are completely transparent, but some are good enough at index-of-refraction-matching that they're extremely hard to see.  It's much more difficult for terrestrial organisms, though, because air's lower index of refraction -- 1, for all intents and purposes -- is just about impossible to match in any conceivable form of living tissue.

Some of them come pretty close, though.  Consider the "skeleton flower," Diphylleia grayi, of Japan, which has white flowers that become glass-like when they're wet:

The transparency of the flower petals is likely to be a fluke, as it's hard to imagine how it would benefit the plant to evolve a camouflage that only works when the plant is wet.  An even cooler example was the subject of a paper in the journal eLife last week, and looked at a group of butterflies called (for obvious reasons) "glasswing butterflies."  These are a tropical group with clear windows in their wings -- but, it turns out, they're not all closely related to each other.

In other words, we're looking at an example of convergent evolution and mimicry.

The study found that some of the clear-wings are toxic, and those lack an anti-glare coating on the "windows."  This makes the light more likely to reflect from the surface, rather than pass through; think about the glare from a puddle in the road on a sunny day.  Those flashes of light act as a warning coloration -- an advertisement to predators that the animal is toxic, distasteful, or dangerous.

The glasswing butterfly Greta oto of Central and South America [Image is licensed under the Creative Commons David Tiller, Greta oto, CC BY-SA 3.0]

The coolest part of last week's paper was in looking at the mimics; the species that had the transparent windows but weren't themselves toxic.  Unlike the toxic varieties, those species had evolved anti-glare coatings on the windows, so the mimicry was obvious in bright light -- but in shadow, the lack of glare made them seem to disappear completely.  In other words, the clear parts act as a warning coloration in sunshine, and as pure camouflage in the shade!

Even more amazing is that a number of only distantly-related species have stumbled on the same mimicry -- so this particular vanishing act has apparently evolved independently more than once.  A good idea, apparently, shouldn't just be wasted on one species.

So that's today's cool natural phenomenon, which I hope I've clarified sufficiently.  There seems truly to be no end to the way living things can take advantage of physical phenomena for their own survival -- as Darwin put it, to generate "endless forms most beautiful and most wonderful."

*************************************

It's kind of sad that there are so many math-phobes in the world, because at its basis, there is something compelling and fascinating about the world of numbers.  Humans have been driven to quantify things for millennia -- probably beginning with the understandable desire to count goods and belongings -- but it very quickly became a source of curiosity to find out why numbers work as they do.

The history of mathematics and its impact on humanity is the subject of the brilliant book The Art of More: How Mathematics Created Civilization by Michael Brooks.  In it he looks at how our ancestors' discovery of how to measure and enumerate the world grew into a field of study that unlocked hidden realms of science -- leading Galileo to comment, with some awe, that "Mathematics is the language with which God wrote the universe."  Brooks's deft handling of this difficult and intimidating subject makes it uniquely accessible to the layperson -- so don't let your past experiences in math class dissuade you from reading this wonderful and eye-opening book.

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

Loop-the-loop

Of all the bizarre and fascinating discoveries physicists have made in the last century and a half, I think the one that twists my brain the most is the effect massive objects have on the space around them.

I use the "twists" metaphor deliberately, because the concept -- commonly called "warped space" -- is that anything with mass deforms the space it's in.  You've probably heard the two-dimensional analogy, to a bowling ball sitting on a trampoline and stretching the fabric downward.  If you then roll a marble across the trampoline, it will follow a deflected path.  Not because the bowling ball is mysteriously attracting the marble; the marble is merely following the contours of the space it's traveling through.

Increase the number of dimensions by one, and you've got a basic idea of what this feature of the universe is like.  We live in a three-dimensional space warped into a fourth dimension, and something passing near a massive object (as with the trampoline analogy, the more massive the object, the greater the effect) will follow a curved path.  Possibly, if the "attractor" is big enough, curved into a closed loop -- like the Moon does around the Earth, and the Earth does around the Sun.

Where it gets even weirder is that the degree of deflection of the moving object is dependent on how fast it's going.  Again, the marble provides a good analogy; a fast-moving marble will not alter its trajectory from a straight line very much, while a slow-moving one might actually fall into the "gravity well" of the bowling ball.  The same is true here in three-dimensional space.  This is why there's such a thing as "escape velocity;" the velocity of an object has to be great enough to escape the curvature of the gravity well it's sitting in, and that velocity gets larger as the "attractor" becomes more massive.

With a black hole, the escape velocity is greater than the speed of light.  Put a different way, space around a black hole has been warped so greatly that nothing is moving fast enough to avoid falling in.  Once you get close enough to a black hole to experience that degree of space-time curvature (a point called the "event horizon"), there is no power in the universe that can stop you from falling all the way in and meeting a grim fate called (I kid you not) "spaghettification."

Which, unfortunately, is exactly what it sounds like.

Why this mind-warping topic comes up is because of a paper that appeared this week in Scientific Reports, describing research by Albert Sneppen, a student at the Niels Bohr Institute, looking at what would happen to light as it passed very near -- but not within -- the event horizon of a massive black hole.  Sneppen came up with a mathematical model showing that it creates an effect so bizarre and unmistakable that it is now being proposed as a way of detecting distant black holes.

Suppose between us and a distant galaxy is a large black hole.  The black hole (being black) is invisible; it can only be seen because of how it interacts with the matter and energy around it.  So the light from the galaxy has to pass near the black hole on its voyage to us.  The particles of light that stray too close follow the curvature of space right into the black hole, as you might expect.  The ones that get close, but not too close, are where things are interesting.

Recall that the Earth follows an elliptical path around the Sun because the Sun is warping space enough, and the Earth is moving slowly enough, that the Earth doesn't slingshot away from the Sun (fortunately for us) but remains "captured," following the shortest path through curvature of the space it's in.  So presumably there is a distance around a massive black hole that would have the same property vis-à-vis light; a distance where light speed is exactly right for it to follow the lines of the intensely curved space it's traveling through and describe a circular (or elliptical) path.

So light at that distance would become trapped, circling the black hole forever.  But what about light from the same distant galaxy that is just a leeeeeetle bit farther away?  And a leeeeetle farther than that?  What Sneppen showed is that this effect would cause the light rays from the galaxy passing progressively farther and farther away from the black hole to make a specific number of loops around the black hole before "escaping."  So of the photons of light from the galaxy that end up after that cosmic loop-the-loop heading our way, some (the ones the farthest away from the black hole to start with) would have circled the black hole only once, some twice, some three times, etc.

What this would do is create multiple images of the same galaxy, strung out in a line.

Check out the drawing by Sneppen's collaborator, Peter Laursen, showing the results of the effect:

So there you have it; this morning's reason to feel very, very small.  I don't know about you, but I think the human species can use a little humility these days,  We need to be reminded periodically that we are tiny beings in an enormous universe, one that is so bizarre that it boggles the mind.  Although I have to say it's impressive that we tiny insignificant beings have begun to understand and explain this bizarreness.  As astronomer Carl Sagan put it, "We are a way for the universe to know itself."

**************************************

I've loved Neil de Grasse Tyson's brilliant podcast StarTalk for some time.  Tyson's ability to take complex and abstruse theories from astrophysics and make them accessible to the layperson is legendary, as is his animation and sense of humor.

If you've enjoyed it as well, this week's Skeptophilia book-of-the-week is a must-read.  In Cosmic Queries: StarTalk's Guide to Who We Are, How We Got Here, and Where We're Going, Tyson teams up with science writer James Trefil to consider some of the deepest questions there are -- how life on Earth originated, whether it's likely there's life on other planets, whether any life that's out there might be expected to be intelligent, and what the study of physics tells us about the nature of matter, time, and energy.

Just released three months ago, Cosmic Queries will give you the absolute cutting edge of science -- where the questions stand right now.  In a fast-moving scientific world, where books that are five years old are often out-of-date, this fascinating analysis will catch you up to where the scientists stand today, and give you a vision into where we might be headed.  If you're a science aficionado, you need to read this book.

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

Through a glass, darkly

I was chatting with my younger son a couple of days ago.  He's a professional scientific glassblower, so anything having to do with the properties, chemistry, or uses of glass is going to interest him automatically.  And this was how he ran into the name of Walter John Kilner.

My son asked me if I'd ever heard of him, which I hadn't, and he suggested I look into him as a possible topic for Skeptophilia.  What I found out was pretty interesting -- straddling that gap between "fascinating" and "crazy."

Kilner, who lived from 1847 to 1920, studied medicine, physics, and engineering at Cambridge University, eventually earning a master's degree as well as a doctorate in medicine.  He had a private medical practice as well as being a "medical electrician" -- then a brand-new field -- at St. Thomas Hospital in London.

So the man was certainly not lacking in brains.  But he veered off into an area that is fringe-y at best, and to this day we don't know if what he was seeing was real.

The basic idea is familiar to us today as the "aura," but what most people mean by that -- some sort of spiritual halo around humans (and supposedly, all living things) that conveniently can't be measured by any known technique -- is several shades more woo-woo than what Kilner meant.  He seems to have latched onto the idea of there being a kind of electromagnetic radiation given off by the human body that was outside the range of human vision, and which could potentially be used as a diagnostic tool if a device was developed that allowed us to see it.

In fact, there is invisible radiation coming from our bodies; it's infrared light, which is light that has a longer wavelength than red light.  (Nota bene: it took me some pondering to get past the misunderstanding that infrared and thermal radiation aren't the same thing.  Thermal radiation can be in any region of the spectrum -- think of the red light given off by a hot stove burner.  The wavelength of thermal radiation is dependent upon the temperature of the source.  Infrared, which can be emitted thermally, is defined by having wavelengths longer than that of visible light, regardless of how it's generated.)

More germane to Kilner and his goggles, although the human eye can't detect it, mosquitoes' eyes can (one of the ways they find us in the dark), and it can be sensed by the "loreal pits" of pit vipers that they use for finding prey at night, not to mention the infrared goggles used by the military, which convert long-wavelength infrared light to shorter wavelengths that we can see.  

So there was at least some scientific basis for what he proposed, and remember that this would have been in the late nineteenth century, when the properties of electromagnetic radiation were still largely mysterious.  What Kilner proposed was that since light is altered when it passes through filters of any kind, there might be a filter that could take the electromagnetic radiation from the aura and convert it to visible light.

His approach was to take thin layers of alcohol-soluble dyes, most derived from coal tar, sandwiched between two sheets of clear glass.  He claimed he found one that worked -- a blue dye he called dicyanin -- but according to Kilner, it was difficult to produce, so he started fishing around for a substitute.

Along the way, he convinced a lot of people that his dicyanin filter allowed him to see the human aura, and generated a huge amount of enthusiasm.  People suggested other blue dyes -- cobalt-based ones, and other coal tar derivatives like pinacyanol -- but the results he obtained were equivocal at best.  Nobody was able to produce dicyanin again, or even figure out what its chemical composition was, which certainly made any skeptics raise an eyebrow.  But to the end of his life, Kilner swore that his dicyanin filter allowed him to see clearly an aura around his volunteers' naked bodies, despite an analysis by the British Medical Journal stating bluntly, "Dr. Kilner has failed to convince us that his 'aura' is more real than Macbeth's visionary dagger."

So what, if anything, did Kilner see?  The easiest answer is: we don't know.

The whole thing reminds me of Kirlian photography -- those familiar (and striking) photographs that result from placing a photographic plate on top of a high voltage source, then adding a flat object of some kind.  This produces a coronal discharge, a purely physical effect caused by the voltage creating temporary ionization of the air molecules.  Pretty much anything works; I've seen Kirlian photographs of coins.  But this doesn't stop the woo-woos from claiming that Kirlian photographs are capturing the aura, and giving it all sorts of spiritual and/or esoteric overtones.

Kirlian photograph of a dusty miller leaf [Image licensed under the Creative Commons Rarobison11, MDR Dusty Miller, CC BY-SA 4.0]

In the case of Kilner, though, the effect was never successfully replicated.  This hasn't stopped people from making "Kilner goggles" that you can still buy online, if you've got no better use for your money.  But as far as Kilner himself, he seems to have been entirely sincere -- i.e., not a charlatan or outright liar.  He pretty clearly believed he'd seen something that deserved an explanation.  Whether it was some kind of optical effect produced by his mysterious dicyanin, or a faint blur in the image that he then gave more significance than it deserved, we honestly don't know.  (This is reminiscent of the "canals of Mars," first described by astronomer Giovanni Schiaparelli, which were clearly an artifact of poor telescope quality -- when the optical equipment improved, the Martian canals mysteriously vanished, never to be seen again.)

Another possibility, though, was brought up by my wife; a lot of the dyes and solvents that Kilner used are neurotoxic.  It could be that what he was seeing was a visual disturbance caused by inhaling the fumes from nasty compounds like polycyclic aromatic hydrocarbons, common in the coal tar he was using to prepare his dyes.

The interesting thing is that Kilner completely dismissed the esoteric spin that auras were given during the last decade of his life, primarily by the Theosophists and Spiritualists who were skyrocketing in membership during the first decades of the twentieth century.  Kilner remained to the end a staunch believer in the scientific method, and that anything he'd seen had a purely physical origin that was explainable in terms of the properties of light and electromagnetism.

It's an interesting case.  The fact that in the hundred years since he died, no one's ever been able to replicate his findings, strongly supports the fact that he was simply wrong -- he'd seen something, but it had nothing to do with anything that could be called an aura.  Even so, he's an interesting example of someone who was clearly trying to do things the right way, but his own determination to prove his conjecture blinded him to the obvious conclusion.

Further stressing the truth of Leonardo da Vinci's statement that "We must doubt the certainty of everything that passes through our senses."

*************************************

One of the most devastating psychological diagnoses is schizophrenia.  United by the common characteristic of "loss of touch with reality," this phrase belies how horrible the various kinds of schizophrenia are, both for the sufferers and their families.  Immersed in a pseudo-reality where the voices, hallucinations, and perceptions created by their minds seem as vivid as the actual reality around them, schizophrenics live in a terrifying world where they literally can't tell their own imaginings from what they're really seeing and hearing.

The origins of schizophrenia are still poorly understood, and largely because of a lack of knowledge of its causes, treatment and prognosis are iffy at best.  But much of what we know about this horrible disorder comes from families where it seems to be common -- where, apparently, there is a genetic predisposition for the psychosis that is schizophrenia's most frightening characteristic.

One of the first studies of this kind was of the Galvin family of Colorado, who had ten children born between 1945 and 1965 of whom six eventually were diagnosed as schizophrenic.  This tragic situation is the subject of the riveting book Hidden Valley Road: Inside the Mind of an American Family, by Robert Kolker.  Kolker looks at the study done by the National Institute of Health of the Galvin family, which provided the first insight into the genetic basis of schizophrenia, but along the way gives us a touching and compassionate view of a family devastated by this mysterious disease.  It's brilliant reading, and leaves you with a greater understanding of the impact of psychiatric illness -- and hope for a future where this diagnosis has better options for treatment.

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