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."

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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!]

The physics of holy water

A couple of days ago, I had the honor of being interviewed by Robert Chazz Chute, the journalist, writer, and deep thinker who sponsors the Cool People Podcasts.  The conversation was varied and interesting, touching on skepticism, atheism, science, pseudoscience, and education -- all of which regular readers of this blog will know are particular fascinations of mine.  (And a link to my interview will be posted as soon as it becomes available, should any of you be interested in hearing what I sound like -- and seeing whether I make the same amount of sense when speaking extemporaneously as I do when I've had time to plan what I'm going to say ahead of time.)

At one point, the question came up (during a discussion of conspiracy theories) of how heavily we should lean against rules of thumb like Ockham's Razor and the ECREE principle.  Although different in their details, both of these guidelines for sound thinking revolve around the idea that the world generally behaves in a predictable manner, and that wild claims that rest on large numbers of ad hoc assumptions require a higher standard for evidence than do ones for which the mechanism is already well understood.  To give an admittedly facile example, if I said that I dropped a stone off the railing of my deck, and it fell straight down and hit the ground, I shouldn't need to prove it; if I claimed that it fell upwards and finally vanished into the clear blue sky, something more than just my word for it would be rightfully demanded of me.

The sticking point comes with where, on the spectrum of weirdness, a particular claim lies.  Not everything is quite as clear cut as stones falling upwards rather than the usual down.  There is no meter to measure the sensibility of an idea, more's the pity.  Also, there are realms of what is now experimentally-supported science -- subatomic physics comes to mind -- where the conclusions are so counterintuitive that if they had been presented as simple statements of fact by a physicist a hundred years ago, (s)he would have been laughed into oblivion.

So, how do you decide, then?  "That sounds specious" isn't exactly a rigorous analysis.  Is there some better way to approach the question?

Let's turn to a specific example that came out of Russia last week -- a claim that making the sign of the cross over a container of water changes the water's properties.

Here's the claim.  I'm quoting the article directly, but this is the English version created by Google Translate, so any grammatical errors are probably not in the original and should not be blamed on the author.

Studies conducted by the Laboratory of Biomedical Technology Institute of Industrial and Marine Medicine, became a sensation. Scientists have proved experimentally that the sign of the cross kills germs and changes the optical properties of water.

- We have confirmed that the ancient custom of going to baptize food and drink before the meal has a deep mystical sense - says physicist Angelina Malakhovskaya - For the practical use of it is hidden: the food is cleared in just a moment. It is a great miracle that happens literally every single day.

Its research strength sign of the cross Angelina Malakhovskaya spent almost 10 years. Carried out a large series of experiments that repeatedly cross-checked before publish the results.

They are phenomenal: identified the unique antibacterial properties that appear in the water from its consecration prayer and sign of the cross. A new, previously unknown property of the Word of God to transform the structure of water, greatly increasing its optical density in the short ultraviolet region of the spectrum.

The very possibility of this research to Malakhovskaya Angelina and her fellow St. Petersburg was a miracle - they were not funded, is beyond the scope of research institutes. But scientists do a large amount of work free - just to give people an opportunity to feel and see the healing power of God.

The scientists tested the effects of prayer "Our Father" and the sign of the cross on the pathogenic bacteria. For the study, samples were taken from the oceans of water - wells, rivers and lakes. In all the samples contained E. coli, Staphylococcus aureus. But it turned out that if you read the prayer "Our Father" and make the sign of the cross test, the amount of harmful bacteria decreased in 7, 10, 100 or even 1000 times!..  

- It was found that the optical density compared to its original value before the consecration increases - says Angelina Malakhovskaya - This means that the water as if to "discriminate" the meaning of the prayers uttered over it, it remembers the impact and keeps it indefinitely - in the form of increased absorbance values. She seemed to be "saturated" with light. The human eye can catch these salutary changes in the structure of water, of course, can not. But spectrograph instrument provides an objective assessment of this phenomenon.

Sign of the cross changes the optical density of the water almost instantly. Optical density of tap water is sanctified by the commission sign of the cross over her ordinary believers increased by 1.5 times! And at the dedication of the priest - almost 2.5 times! So it turns out that the water "distinguish" the degree of dedication - a layman or a priest who has his right hand in blessing so stacked that represent the first letters of the name of Christ.

An interesting result of the consecration of the waters of baptism, but the unbeliever, not wearing a crucifix. It was found that water "distinguishes" faith even degree - optical density changed only by 10%!

Now, I doubt I have to state for the record that I think these claims are grade-A horse waste.  But in science, that's not enough.  That's yet another fallacy, the Appeal to Authority -- that I have set myself up as some sort of Arbiter of What Makes Sense, and you should agree with me just because I say so.

So let's take the claim apart.  What Dr. Malakhovskaya seems to be saying is that after being blessed, two things happen to a container of water: (1) its bacteria count goes down; and (2) its optical density in the short ultraviolet region increases.

Let's take those two claims in order.

A fundamental rule of doing science is that if the changing one variable causes another to change, it will do so in a regular fashion.  This predictability is the basis on which all science rests.  As science educator Roger Olstad puts it, "Science is, simply put, the search for regularity among observations."  A corollary of this idea is that if perturbing a particular variable causes different results each time, there must be something else going on that you haven't accounted for.

In scientific parlance, the experiment is not "well controlled."

Note that in the alleged experiment with the Staphylococcus aureus bacteria, the blessing of the water made the bacterial count drop by a factor of 7.  Or 10.  Or 100.  Or "even 1000."  Is it just me, or does this sound like there's a problem with her experimental design, here?  Maybe she didn't measure the bacteria accurately in the first place.  Or maybe they weren't uniformly dispersed throughout the water sample.  Or maybe she made errors in her sampling protocol after the water was blessed.  There are a hundred things that could have gone wrong with this experiment, each of which would be a far better explanation of the variability of the results than the alternate explanation, which is that the Sign of the Cross works better as an antiseptic on Sundays than it does on Thursdays.

So let's take a look at her second claim, which gets us into (if you'll forgive the pun) even deeper water.

Seeing the problem with the second experiment -- that blessing water increases its optical density -- requires that you understand a bit of physics.  The wonderful site The Physics Classroom explains optical density as follows:

The optical density of a material relates to the sluggish tendency of the atoms of a material to maintain the absorbed energy of an electromagnetic wave in the form of vibrating electrons before reemitting it as a new electromagnetic disturbance. The more optically dense that a material is, the slower that a wave will move through the material.

One indicator of the optical density of a material is the index of refraction value of the material. Index of refraction values (represented by the symbol n) are numerical index values that are expressed relative to the speed of light in a vacuum. The index of refraction value of a material is a number that indicates the number of times slower that a light wave would be in that material than it is in a vacuum.

So, the claim is that blessing the water somehow changes the speed with which light travels through it -- but only the speed of light waves in the short ultraviolet region.

Herein lies the problem.  The optical properties of transparent substances have been studied extensively (largely because otherwise, we would have a hard time making camera, telescope, microscope, or eyeglass lenses that worked).   The optical density of a substance is dependent on wavelength -- the relationship is called the Sellmeier Equation.  And what the Sellmeier Equation implies is that it would be impossible to change the optical density of water at one wavelength without changing its optical density at every other wavelength.  You can't, in other words, selectively alter water's optical density in one region of the spectrum, which is what Dr. Malakhovskaya is saying.  In order to accept what her claim, you pretty much have to trash everything we know about optics.

So which is more likely -- that every physicist who has studied the behavior of light transmission in the past hundred years is wrong, or that Dr. Malakhovskaya's spectrograph wasn't working?  Or that she fabricated her results?  Or that there was a flaw in her experimental design?  Be honest, which requires you to make the least ad hoc assumptions, here?

That is how you apply Ockham's Razor.

Now, I know that there are some devout folks who at this point are saying, "Yes, well, what if god had something to do with it?  Anything is possible with god."  Okay, fine, but you have now moved the discussion outside of the realm of science.  Once you have allowed for the finger of the deity tinkering with the results in some kind of capricious fashion, you have put paid to anything science can say about the matter.  That is not how science is done.  And I must, in the interest of honesty, throw in a quote from Tim Minchin: "Every mystery ever solved, in the history of the world, has turned out to be NOT MAGIC."

I have deliberately chosen a rather ridiculous example, here, at least in part so as not to raise hackles.  But there's no reason why you have to stop with this one.  Look at other claims using this method.  A few suggestions: homeopathy; astrology; telepathy; clairvoyance; astral projection; remote viewing; divination; witchcraft; and, I might add, the majority of the beliefs of the world's major religions.   Ask yourself what the evidence really supports.  Ask what well understood, experimentally supported laws of science the claim is asking you to jettison.

Then, and only then, decide what you think is correct.