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Today I wanted to write more about giant clams and their astonishing ability to “farm” algae within their body (and then live off of the sweet sugars which the algae produce).  I still want to write about that, but it proving to be a complicated subject: giant clams mastered living on solar energy a long time ago, and we are still trying to figure out the full nature of their symbiotic systems.

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Today, instead we are going to look at the phenomenon which gives the mantles of giant clams their amazingly beautiful iridescent color. It is the same effect which provides the shimmering color of hummingbird feathers and blue morpho wings, or the glistening iridescence of cuttlefish.  All of these effects are quite different from pigmentation as generally conceived:  if you grind up a lapis lazuli in a pestle, the dust will be brilliant blue (you have made ultramarine!) but if you similarly grind up a peacock feather, the dust will be gray, alas! This is because the glistening reflective aqua-blue of the feather is caused by how microscopic lattices within the various surfaces react with light (or I suppose, I should really go ahead and call these lattices “nanostructure” since they exist at a scale much smaller than micrometers). These lattices are known as “photonic crystals” and they appear in various natural iridescent materials—opals, feathers, and scales.  Scientists have long studied these materials because of their amazing optic properties, however it is only since the 1990s that we have begun to truly understand and engineer similar structures on our own.

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Physicists from the 19th century onward have understood that these iridescent color-effects are caused by diffraction within the materials themselves, however actually engineering the materials (beyond merely reproducing similar effects with chemistry) was elusive because of the scales involved.  To shamelessly quote Wikipedia “The periodicity of the photonic crystal structure must be around half the wavelength of the electromagnetic waves to be diffracted. This is ~350 nm (blue) to ~650 nm (red) for photonic crystals that operate in the visible part of the spectrum.”  For comparison, a human hair is about 100,000 nanometers thick.

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The actual physics of photonic crystals are beyond my ability to elucidate (here is a link to a somewhat comprehensible lay explanation for you physicists out there), however, this article is more to let me explain at a sub-rudimentary level and to show a bunch of pictures of the lovely instances of photonic crystals in the natural world. Enjoy these pictures which I stole!

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But, in the mean time don’t forget about the photonic crystals! When we get back to talking about the symbiosis of the giant clams, we will also return to photonic crystals!  I have talked about how ecology is complicated.  Even a symbiotic organism made up of two constituent organisms makes use of nanostructures we are only beginning to comprehend (“we” meaning molecular engineers and materials physicists not necessarily we meaning all of us). imagine how complex it becomes when there are more than one sort of organism interacting in complex ways in the real world!

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A day ago an international team of stellar physicists announced that the sun’s surface is covered with thousands of searing hot plasma super tornadoes each of which is the size of a large continent on Earth.  Using a combination of a space telescope and a ground telescope, researchers discovered that each of these plasma vortexes spins at velocities up to 14,500 kilometers (9,000 miles) an hour.

(CREDIT: Wedemeyer-Böhm: Parts of the image produced with VAPOR)

The mystery of why the corona of the sun is 300 times hotter than the star’s surface has long vexed scientists.  The surface of the sun is a balmy 5,526 degrees Celsius (9,980 Fahrenheit), while temperatures in the corona peaks 2 million degrees Celsius (3.5 million Fahrenheit). The discovery of these giant fast-moving storms provides a new mechanism by which heat is transferred through the sun’s atmosphere and ejected into the corona. Energy locked in the powerful magnetic vortexes is effectively self-insulated and does not heat the solar photosphere and chromosphere as much as the corona (where the storms widen and dissipate).

The Sun photographed by the Atmospheric Imaging Assembly (AIA 304) of NASA’s Solar Dynamics Observatory

Sven Wedemeyer-Böhm, a Norwegian scientist working on the team was quick to stress that the tornadoes are likely one of several complicated energy transfer mechanisms by which heat reaches the solar corona. However it seems that there are more than 11,000 of these huge plasma tornadoes on the solar surface at any given time.

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