The Light Fantastic

"My own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose" - JBS Haldane

Have you ever gotten a new camera, and decided to finally learn something about how photography works? You know, f-stops, exposure, ISO, all that stuff? I have. Multiple times, actually, because I can't seem to remember it. I'm learning again now. I was trying to figure out how aperture--the size of the hole light passes through in the lens--affects focus. I learned (once again), that the smaller the hole is, the greater your depth of field will be. Not only will your subject be in focus, but the background will be too. Make the hole bigger, and the background will be all blurry. But then I started wondering why that actually happens. Why does light that goes through a little hole stay more focused than light that goes through a big hole? That ignited my curiosity about light and lenses, and before long I had gotten out an old physics book from college to try to wrap my head around all that stuff.

That got me thinking about an idea I've always found fascinating. When you really start looking at how light behaves, it almost starts to seem intelligent. I mean, it's not really, but it gives that impression. Consider this: lenses work because they refract light, which just means they bend light rays. The reason they do is that light travels more slowly in glass than air. If you shine a beam of light through a thick piece of glass (at an angle) and onto a wall, it will bend and slow down when it enters the glass, and then bend again when it leaves. And here's where it gets weird--if a beam of light goes from point A to point B, as shown below, somehow it's able to choose the one path, among the many possible, that takes the least amount of time. That path isn't necessarily a straight line, because if it moves more slowly in glass, then it should alter its course so the distance through the air is farther, and the distance through the glass shorter.

The classic analogy is a with a lifeguard rushing to save a drowning swimmer. Imagine you're that lifeguard, standing on the beach. You look out to your left and see the swimmer in trouble, as shown below. Should you make a beeline--running, and then swimming, straight at him? No...sometimes the fastest route between two points isn't a straight line. You can run faster than you can swim, so you should run a little farther down the beach, so you don't have to swim so far. There's an optimal route that's faster than any other. Most lifeguards won't hit on it exactly. But light is smarter than a lifeguard, at least in that sense. It finds the fastest route, and it does so at, well, the speed of light. It doesn't matter if it has to bend and straighten its way through several layers of air and glass--the path it chooses will be the one that takes the least time.

How does it do that? How does it "know" which path to take? Christian Huygens came up with a plausible answer back in 1678, by thinking of light as moving in a wave, and of a wave front as the combination of many smaller waves. He was able to model refraction that way, as in this image. As the wave fronts approach the glass at an angle, each one changes angles as it slows down and enters. The change in direction will be at an angle that minimizes the time it takes for light to get from one point to another. Huygens was also able to model reflection this way, and a guy named Fresnel applied the idea to other "wavy" phenomena, like diffraction and interference. Nature is full of things that move in waves, and thus behave in all these ways, including water waves, sound waves in the air, and even seismic waves through the earth. Applying the idea to light helped turn the tide of scientific opinion away from Newton's idea theory that light was made of particles, and got physicists thinking of light as ripples propagating through space.

The Huygens-Fresnel idea does seem to provide a mechanism for how light "chooses" the shortest path, and it accurately predicts what that path will be. The problem is, light doesn't really work that way. At least, it's a lot more complicated than Huygens realized. Since the early 20th century, physicists have known that light is as much particle as wave. A beam of light is composed of countless discrete particles called photons. Each one has a frequency, which is what determines the color of visible light. Physicists once thought that brightness (amplitude) was analogous to the height of water waves--brighter light was thought to have higher crests and lower troughs. But it turns out that all photons of a particular wavelength carry the same amount of energy. A bright light is just spewing out more photons per second than a dim light.

This gums up the works for Huygens' wave theory. Even if you send one photon at a time through a piece of glass, light will still pick the fastest path. That's pretty crazy when you thing about it. How can a single particle do that? The simplistic wave theory also falls apart when you look closely at reflection. If you shine a light on a pane of glass, most of it will go straight through. But up to 16% of the photons will bounce back, which is why you see a dim reflection even in transparent glass. Light reflects from both the front side and the back side of the glass, and how much it reflects depends on how thick it is. And that's where it gets crazy once again. If you put a light detector inside a very thick pane of glass and aim a stream of photons at it, you can measure how many photons are reflected by just one surface--the front--and you'll find it's about 4% in most kinds of glass. But if you send the light all the way through the glass, and measure how much is reflected, you find a strange trend. As you keep making the glass thicker, you find that the amount of light reflected will rise and fall regularly--rising gradually from zero up to 16 percent, falling back toward zero, and then rising again. Think about that zero percent. That means, even though four percent of photons bounce off the front surface of glass, if you add a back surface it can cut that percentage to zero. What?? How does the light "know" how far away the back of the glass is when it's just getting to the front? Somehow it does, even if the glass is several meters thick. It's like light isn't just smart...it's psychic.

Of course, it's not really, but the truth is just about that weird. All this stuff is explained by the theory of quantum electrodynamics, or QED. Let's go back to light taking the fastest path through a piece of glass. If I understand it correctly, QED says that each photon takes every path from one point to another--even long ones, where it goes way off to the side and then back again. It spreads out all over the place in a very un-particle-like way, but then arrives as a particle. Each of those paths has a certain "probability amplitude" (the quantum world is all about probabilities) and oddly enough, most of the paths are about equally probable. But the probabilities mostly cancel each other out, except for those very close to the one that takes the least time. So that's the direction the light goes. A similar interaction of probabilities determines how much light will reflect off glass of various thicknesses. That all sounds crazy, and I certainly don't understand it in any deep sense, but apparently the math works just fine. Even physicists who have mastered the equations can't really explain what's going on--they don't understand why those equations work.

But they do work, smashingly. QED describes the quantum basis for most of the physical processes we see all around us; how light moves, how electrons orbit nuclei, how atoms bond together to create different materials...basically everything except nuclear physics, gravity, and certain kinds of radioactivity. Not only that, it's one of the most accurate theories in science. One of the originators of the theory, Richard Feynman, compared its accuracy to measuring the distance across the United States with a margin of error smaller than the width of a human hair. But the theory is also completely mind-boggling. As Feynman also said, "The theory of quantum electrodynamics describes Nature as absurd from the point of view of common sense. And it agrees fully with experiment. So I hope you accept Nature as She is--absurd." Light, and everything else at the quantum level, is pretty freaky stuff. But Feynman had a deep reverence for nature, and I think his point was more about common sense than nature itself. Light is more fundamental and ubiquitous than we are--it's pervaded space and time since the universe began. Looking at nature at a wide angle, we're the anomaly, not light or any other quantum phenomenon. If we find that it's absurd from the point of view of common sense, then we've discovered yet another flaw in common sense. Who are we to say what's absurd?

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QED: The Strange Theory of Light and Matter / Richard Feynman

I never explained how depth of field works. Here's a video that does

Good video introduction to QED

An even more mind-blowing, but more widely known, phenomenon of quantum physics is demonstrated by the double slit experiment. Good video on it here.

We are Stardust. No...Seriously.

We are stardust                     
We are golden                       
    We are billion-year-old carbon
                         - Joni Mitchell

Crab Nebula: A Supernova Remnant

Sometimes my fellow skeptics get on my nerves. So many of them focus too much on negatives--on what's false, rather than what's true. They get so fixated on debunking falsehoods and quackery that they forget to talk about how amazing the real world is. Don't get me wrong...nonsense certainly needs to be exposed, and naked emperors should assuredly be mooned. But still, there's a balance to be struck. Why spend all your time talking about what you don't believe? Why define yourself negatively--in terms of what you reject?

Since I spent my last post talking about astrology and other things I reject, in this one I want to tip the scales in a more positive direction and talk something not only beautiful and wondrous, but scientifically sound to boot. I want to talk about the stars--the stars of the astronomers, not the astrologers. Astrologers have always been fascinated by stars, and rightly so, but I think they miss what's really amazing about them. It's not that the stars influence our personality or destiny in any direct way. They are, after all, giant balls of incandescent plasma, and even the closest are almost inconceivably far away. There's zero scientific reason to think they influence our daily lives--they don't care about some race of featherless bipeds on a faraway planet, and they couldn't do anything about it if they did. But that doesn't mean we have no connection to them. The stars aren't about us, however much we might want them to be, but we are about them. Joni Mitchell was basically right--we really are stardust.

To be more specific, most of the atoms in our bodies, and almost all the elements in the periodic table, were forged billions of years ago in the interiors of stars. Many of the heavier elements were created in stellar death throes, in the titanic explosions known as supernovae. All these processes of element creation are still going on today. The elements that weren't formed in stars (mainly hydrogen and helium) have an even more impressive provenance--they were formed in the Big Bang itself, 13.8 billion years ago.

When scientists are asked what is the most amazing scientific fact they know, many of them talk about how we are made of stardust (star-forged atoms, technically). I tend to agree with them. It's an idea as stunning as anything I've ever heard, and unlike astrological ideas, it's almost certainly true. Here's the basic story scientists have pieced together.

Less than a second after the universe began, protons, neutrons, electrons, and various other particles had formed. As the infant universe expanded and cooled, between the first 3 and 5 minutes, protons and neutrons clumped together to form what would become the nuclei of hydrogen (which has a single proton), and helium (which has two). Conditions were such that this created 6 helium nuclei for every 76 hydrogen nuclei. After about 380,000 years, the radiation that had been knocking electrons away from nuclei cooled enough to allow atoms to form. The hot, glowing universe went dark, but this radiation can still detected today in the form of weak microwaves that permeate space. Astronomers call it the Cosmic Background Radiation--the afterglow of the creation of the universe.

The early universe, then, was a homogenous sea of hydrogen and helium atoms (along with a little bit of lithium). If it had stayed that way, we wouldn't be here--two elements don't make a rich-enough atomic alphabet to create complex structures like, say, us. But as things kept expanding and cooling, the weakest force of nature--gravity--began to assert itself. Matter attracted matter, and great clouds of hydrogen/helium gas started to collapse into spheres. When the pressure got high enough at their core, hydrogen nuclei were squeezed together into helium nuclei. Nuclear fusion reactions had ignited, and the dark universe lit up once again, this time with the light of countless stars. (At larger scales, of course, stars and other matter had formed galaxies, which grew as "small" galaxies combined into larger ones.)

The Cat's Eye Nebula (A Planetary Nebula)

After these primordial stars had burned for a few million or billion years (depending on their mass), a core of helium formed at their center.* The more massive the star, the hotter it burned, and the faster the helium core formed. When it did, helium started to fuse into carbon, which would one day become the backbone element for life. But the carbon core couldn't support the weight of the star, so it started to contract, while the hydrogen and helium around it burned even hotter. This caused the star to puff out its outer layers, forming a huge, cool(er), red giant star. Eventually this behemoth would blow away its outer layers entirely, forming a luminous cloud called a planetary nebula. The core would remain as an intensely hot, small, dense star called a white dwarf, which might be smaller than the earth but more massive than the sun.

Things got a little more exciting in bigger stars, several times as massive as the sun. Here again, hydrogen burned to create a core of helium, which then burned to create a core of carbon. This time, though, temperatures got high enough (hundreds of millions of degrees) for carbon to start fusing into neon. And on it went--neon fused into oxygen, oxygen into silicon, and silicon into iron. Now there was an iron core surrounded by all these other elements, still burning furiously in concentric layers. Once the iron core formed...game over. As tough as iron might seem to us, it couldn't support the weight of all those layers. The iron nuclei were torn apart, and then the protons combined with electrons to form neutrons. The core of the star collapsed and then rebounded, sending a shock wave shrieking through the outer layers of the star--blasting them apart in a supernova. Supernova explosions can release more energy in a few months than our sun ever will in ten billion years; causing the dying star to glow as bright as a small galaxy. The explosion was energetic enough to create all the remaining elements of the periodic table, and then blast them into space. All that remained of the core was a neutron star--a ball of neutrons as dense as an atomic nucleus but as big as a city, spinning several times per second and spewing jets of radiation from each pole.

These dying stars enriched interstellar space with clouds of elements beyond hydrogen and helium, capable of combining into an enormous variety of molecules, which could in turn combine into all kinds of complex, intricate structures. The new interstellar clouds of heavy elements and molecules then began to collapse again, forming a new generation of stars like our sun, born with a full suite of heavy elements. Around many of these stars, little balls of metal, rock, gas, and ice formed. We call those planets. Many of them have a wide variety of elements--potential building blocks for complex structures. On at least one of these planets, that potential was realized in the form of carbon-based life, which formed shortly after the Earth cooled. It's been evolving and diversifying ever since, creating millions of unique life-forms, from slime molds to blue whales, from giant sequoias to seahorses. Lately, it even created a race of odd, upright, talkative apes; quarrelsome creatures, but clever, too--clever enough to discover that they're made from the dust of exploding stars.

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* Helium was actually first discovered on the sun, based on characteristic spectral lines in the light it emits. It wasn't discovered on earth until later. It's named for Helios, the Greek god of the sun.

Postscript: I've heard the Joni Mitchell's song Woodstock probably a thousand times in my life (mostly the Crosby, Stills, Nash and Young version), and I never noticed that line about "billion year old carbon" until I looked up the lyrics today. Nice work, Joni.

Spa Enlightenment: What's So Spiritual About "New Age", Anyway?

"The universe is cool enough without making up crap about it." - Phil Plait

One of the most interesting things about being a librarian is that it lets you see what other people are interested in. The books you keep reshelving are the ones that strike people's fancy. Some of the books that fly off the shelves the most, at least in my library, have Dewey Decimal numbers in the 130's: Parapsychology and Occultism. That's where you find the books on psychic phenomena, astrology, ghosts, occult practices, and ancient aliens who built the pyramids (or even the moon, according to one book). People eat that stuff up. Every month or so I reshelve a book called Fairies 101: An Introduction to Connecting, Working, and Healing with Fairies and other Elementals. And every month I think, "I can't believe I'm putting this in the non-fiction section."

A closely-related genre that I'm always reshelving is alternative medicine--herbalism, homeopathy, acupuncture, crystal healing, and so on. Those check out at least as often as the books on mainstream medicine. Not all alternative medicine is a kooky as the notion that fairies really cavort in our gardens, but some of those books are pretty out-there, and the people that read them also tend to be drawn to the parapsychology and occult section.

The most common umbrella term for all these things, of course, is New Age. New Age is big business, and like most people in this country, I've met some very New Agey people. One thing that always fascinates me about them is that they seem to see New Age pursuits as a kind of enlightenment--as a means of spiritual growth; a pursuit of knowledge about the great cosmic mysteries. That always strikes me as odd, because it seems almost perfectly backward. In fact, you could make an argument that most New Age pursuits are the very opposite of enlightenment.

Let me explain. If you look at a shelf full of books on New Age ideas, or the kookier forms of alternative medicine, it's hard at first to see what they all have in common. What do ancient aliens have to do with psychic divination or telepathy? Why do the people who check out books on crystal healing also check out the ones on astrology? If you think about it, these are all very different ideas. All they have in common, I think, is an air of exotic mystery. They remain in the realm of the unproven, and outside the realm of mainstream science and medicine. They are, in other words, titillating. Not only that, but they can be personalized. A horoscope doesn't just  tell you about distant stars--it tells you what those stars mean for you. I'm convinced that more people are into astrology than astronomy because, as exotic and mind-expanding as astronomy is, it doesn't have that sexy air of magic and mystery, and it will never be about us.

That's why things like astrology seem like the very opposite of any kind of enlightenment to me. Surely a crucial aspect of enlightenment, whether it's spiritual or intellectual, is to see the wonder in the universe as it really is. It's about seeing the magic in the mundane, not ignoring the mundane because you're too preoccupied with exotica. Consider this: we have specialized organs in our heads that can detect a kind of mysterious energy. This energy pervades the universe and passes in waves through empty space. It can give us detailed information about the world, if we just open our eyes to it. No really. Those organs I'm talking about are our eyes, and that mysterious energy is called light. Light and sight are both entirely astonishing things, if you stop and think about them.

The problem is that we don't. Why are so many people more fascinated by unproven phenomena like auras and psychic divination than by the sense of sight? Because they experience sight every day, and because there are no great mysteries remaining about it. If they had been blind all their lives, and suddenly started seeing, then they would see just how astounding the sense of sight really is. On the flip side, if we were all psychic, and had grown up reading each others' minds, people would be bored with that, too. It's the mystery that grabs people. The problem is that it grabs them so much that they lose interest in the staggering wonders they've seen every day of their lives, and get stuck on exotic-sounding but fictional phenomena. That's not enlightmentment--that's distracted escapism. The real wonders are just that--real. It's just that people are bored with them.*

As I said, though, most of those real wonders aren't about us in any personal way, and that's another strike against them for many new agers. But that just shows another way that New Age thinking and real spiritual growth are opposed. Wouldn't real enlightenment involve some kind of transcendence of selfish concerns? New Age culture is far too self-focused to be considered enlightened. Once I was walking down the street in a city with a large New Age presence (I can't remember which one...maybe Boulder?) Anyway, I noticed a day spa offering various kinds of personal pampering, many involving manipulation of imagined "energies." The place was called Spa Enlightenment. I thought, "Yep, that pretty much sums up the whole mindset. Self-indulgence and fantasy as enlightenment."

Once again, I don't claim any particular enlightenment myself. But I can't help thinking truly enlightened people aren't to be found living in a pretty New Age paradise getting weekly chakra alignments. They'll be in some slum or developing country, trying to help someone besides themselves. And I don't think they'll talk much about horoscopes, crystals, or aliens. They won't be distracted by a set of ideas that have nothing in common except their air of mystery and titillation. They'll be too awestruck by the endless wonders they've been surrounded by all their lives.

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* I'm certainly not saying there's no place in the world for fantasy or fiction. It's just that we shouldn't mistake fantasies for reality, or too get wrapped up in them to notice amazing things that really do exist. Fairy tales are great, but that doesn't mean there are fairies under my bed. I'm also not saying no New Age or alternative medicine idea could ever turn out to be valid and proveable. But if it does go mainstream, I bet a lot of people will lose interest in it, because it won't seem mysterious anymore. Finally, I'm not saying all people with New Agey tendencies are selfish or kooky. Some I know are much more compassionate than I am, but it's not because they read their horoscopes.

Bellybutton Hedgehogs and Piggyback Plants

My latest reading kick is a botanical one--I've been fascinated with plants the last few weeks. But one of the things that's fascinated me most about them has more to do with human creativity than any principle of botany: plants have some truly wonderful names. There's the Piggyback Plant, Bouncing Bet and Herb Robert, Grass of Parnassus, and Mother in Law's Tongue. There's Toadflax and its disreputable impersonator, the Bastard Toadflax. And there's my personal favorite, the Upright Snottygobble. As impessive as the plant kingdom is on its own terms, it's also one of the great showcases of linguistic virtuosity. What unknown poet named the stinging plant called Tread Softly, or the seemingly unclimbable Monkey Puzzle Tree? What lovestruck botanist saw a flower surrounded by lacy bracts and named it Love in a Mist? What heartbroken herbalist named Love Lies Bleeding? Who was the whimsical character that looked at fat little desert succulents and named them Warty Tiger Jaws, or Fairy Elephant's Feet?

Some plant names strike our fancy because they hint at the old and arcane. Liverwort, spleenwort, birthwort, toothwort, and several other worts got their names from the Doctrine of Signatures--the idea that a plant's shape was a clue to the illnesses it could cure. Liverworts look vaguely like a liver, and lungworts look like lungs (if you squint), so people figured they must be good for those organs. The suffix "-wort" still has an air of alchemical mystery, but it's really just an old word for "plant" or "herb". Even the word "herb" sounds more potent than "plant", or "weed", but it really has no particular botanical meaning. An herb is just a smallish, non-woody plant. It might heal you, yes, but then again it might kill you, if you are foolish enough to eat one with a name like Death Camas, Fly Poison, or Deadly Nightshade.

Many plant names come from a more religious time, when the Church and Bible were at the top of people's minds. Hence we have Friar's Cowls, Monkshoods, Bishop's Hats, Angel's Trumpet's, Job's Tears, Jacob's Ladder, and Solomon's Seal. From the darker side of theology we get Devil's Claws and Devil's Walkingsticks. Other plants evoke folk legends and mythology, like Fairy Slippers or the spiky Hercules' Club tree. Some plants carry warnings. The Touch Me Not's name is rather histrionic--its seed pods explode if you touch them, but it won't do anything more than surprise you. Dumbcane won't actually make you stupid, but it will make your tongue go numb. But some plant names truly mean business. Even a goat, which will happily eat poison ivy, will rue the day it ate Goat's Rue, and so will you, if you try it. The same goes for Dogbane. You don't want your cattle getting into a patch of Locoweed, also known as Staggerweed. As for the aforementioned Death Camas, eating that is about as well-advised as handling the snake called the Death Adder. What's in a name? A whole lot, in those cases.

Some plant names, like many words and phrases in general, are so familiar we forget how clever they really are. Larkspurs, formerly known as Lark's Heels, really do have spurs that look like a lark's heel's. Foxgloves are just the right size to slip on a fox's paws, and snapdragons will open their little dragon mouths if you squeeze their cheeks. Another plant whose name will give you an aha! moment if you stop and think about it is the Marsh Mallow. It's a kind of mallow that grows in the marshes, and it was once made into the confections know as Marshmallows.

Some plants are named for virtues, like Honesty and Obedience. Why do plants inspire such names? Can you imagine a species of rodent called Honesty? Legions of plants, of course, are named for their appearance. The Common Donkey Orchid looks just like a long-eared jackass, and Bleeding Hearts look like injured valentines. The carnivorous Cobra Plant looks just like a cobra, complete with a forked tongue emerging from under its hood, while the Snake Lilly winds serpent-like around other plants. The Old Man Cactus has wispy white spines like an old man's hair. Dutchman's Pipe and Dutchman's Breeches look just like they sound, but I can't figure out how Bear's Breeches got their name. Everyone knows bears don't wear breeches--just look at Winnie the Pooh. Finally, there are plants whose names just sound fittingly funny. The Boojum and the Baobab Tree both look like they were designed by Dr. Suess, and their names suit them perfectly, whatever they actually mean.

As great as plant names are, a more humble kingdom reaches even greater heights of nomemclature. I'm talking about the fungi--particularly their fruiting bodies, known as mushrooms or toadstools (a great word in its own right). Mushrooms have some of the best monikers ever. I'm just starting to learn about them, so I'll just mention some of the best ones I've found. There's the Freckled Dapperling and the Lawyer's Wig, the Silky Piggyback and the Dingy Agaric (which is dirty-looking, not airheaded). The Splendid Webcap and the Petticoat Mottlegill seem like well-dressed, classy fungi. But the Dung Roundhead and the Blue Green Slimehead look as disreputable as they sound, and Devil's Fingers and Dead Man's fingers are downright macabre. Most offensive of all is the Stinkhorn, which truly smells horrid, and as its scientific name--Phallus impudicus--suggests, it looks perfectly lewd. It's an ill-mannered fungus all-around. And then there are the dangerous ones: Death Cap, Destroying Angel, Poisonpie, Deadly Gallerina, and Beechwood Sickener. You don't pick a fight with a Hell's Angel, and you don't eat a Destroying Angel.

Some mushrooms are imminent enough to have single names worthy of philosophers or pop stars. In fact, one is called The Prince. There's also The Miller, The Gypsy, and a shady figure known as Deceiver. Along with the Weeping Widow, these sound archetypal and mysterious; like figures in a tarot deck. More whimsical mushrooms include Plums and Custard, Chicken of the Woods, Jelly Babies, and best of all, Bellybutton Hedgehogs. Like plants, many mushrooms get their names from fairytales: Fairy's Bonnets, Pixie Webcaps, Green Elfcups, and Elfin Saddles. Circles of mushrooms that sprout after a rain are known as Fairy Rings. Step inside a fairy ring, the legend says, and you may become enchanted. That's surely true, at least metaphorically speaking. The more I hear about the names of mushrooms and plants, the more enchanted I get.