Friday, May 2, 2008

How Science Works - The Tiger's-Eye Gem

Creationists like to manufacture conspiracy theories to why the Theory of Evolution continues to be the most important theory in Biology. Mostly they revolved around alleged purity movements designed to "Expell" those that question "Darwinism." That's not how scientists conduct themselves.

Rather, a scientist wants to figure how the universe works. Actually works. Not in some bland authoritarian "Goddidit, shut up and give me 10% of your income" but how it actually works, in all its beauty. And sometimes, they check up on accepted pieces of knowledge, just to make sure they understand them or that they are still the best explanation. Like this one:

Early in the 1800s, mineralogists recognized that tiger's-eye was a fibrous variety of quartz, or silicon dioxide. In 1873, the German mineralogist Ferdinand Wibel learned more. While studying the chemistry of hawk's-eye, a blue form of tiger's-eye, he found that the gem was almost entirely quartz but that it also contained fibers of crocidolite, an often bluish, iron-bearing form of asbestos. Wibel proposed that hawk's-eye forms in Earth's crust when quartz dissolved in hot water infiltrates spaces between crocidolite fibers and then slowly replaces the asbestos' molecules. Brown tiger's-eye, Wibel said, comes after yet another step. It results when chemical reactions transform some of the iron in the bluish crocidolite into brownish iron oxide.
Wigel had a nice theory and it lasted a long time. But, as Einstein once pointed out when Hitler was trying to discredit him, it didn't matter how many Nazi scientists signed a letter stating that the Theory of Relativity was wrong. It only took one contrary fact. Which not only illustrates that political/social denunciation from authoritarians accomplishes nothing in the world of science, it segues into the discovery process, and it's periodic challenges of accepted theory, conducted by science:

The idea that tiger's-eye is a pseudomorph--a mineral in which crystals of one material take on the form of another, which it replaces atom by atom--held sway for more than 125 years. In fact, tiger's-eye is cited in many textbooks as a classic example of a pseudomorph, says Peter J. Heaney, a mineralogist at Pennsylvania State University in University Park. During his own efforts to understand the processes underlying pseudomorphism, Heaney examined thin samples of tiger's-eye under a microscope and realized that Wibel was wrong.
He was collecting data. Looking at the structure so he could understand the phenomenon through his own discovery process instead of just accepting the theory as explained. With his contrary fact, Heaney over-turned the theory of formation proposed by Wibel and submitted his own:

Heaney expected to find that the quartz in tiger's-eye is chalcedony, a form that typically consists of fibrous, defect-riddled crystals less than 1 micrometer in diameter. Instead, Heaney was surprised to discover relatively fault-free, column-shaped quartz crystals that measured more than 100 micrometers across and up to 10 millimeters in length. Pseudomorphism doesn't produce such a uniform crystal form.

Heaney and his Penn State colleague Donald M. Fisher suggest that the crystal structure of tiger's-eye forms via a so-called crackseal mechanism. In such a process, quartz and crocidolite crystals simultaneously condense from hot, mineral-rich fluids coursing through a tiny crack in a rock and grow to fill it. Repeated episodes of fracturing lead to more cycles of simultaneous, crack-filling growth of the two crystals.

In the tiger's-eye samples that Heaney studied, crocidolite fibers often ran parallel to the quartz columns. In some cases, however, the angle between the crocidolite and quartz was as much as 30[degress]. Because in those instances, the reflected cat's-eye bands of light were perpendicular to the crocidolite fibers, the scientists conclude that in tiger's-eye the chatoyancy arises from the crocidolite fibers, not the quartz. The researchers report their findings in the April Geology.
Heaney's reward, beyond any internal satisfaction of discovery, is now his name goes with the theory of the formation of Tiger's-Eye gem. Additionally, this feather in his cap may help him secure tenure (if he doesn't have it), grant money and respect.

As members of the general public, we see, in this very recent example, just how the scientific process works when people with political agendas don't try to suborn the process. The best explanation that fits the facts wins, and when someone comes up with a better theory to explain the facts, it will supplant the former theory.
Just as Einstein supplanted Newton in the understanding gravity and it has withstood the test of time, so has the Theory of Evolution taken on all comers and critics. For nearly 150 years (1859). And, with Medal's work (forgotten for decades, ironically) published in 1865, lead to the relatively modern discipline of Genetics.

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