False Bay Birefringence

(Brit )

The trip to False Bay took place at night… in black and white.  Spreading out across the shadowy darkness of the wide mudflat—divergent groups adorned in the fuzzy glow of headlamps, poking and prodding the expanse of inhabited sediment—I could not help but think we were in some small way giving life and breath to the photoelastic stress analysis test that had so gripped imaginations during Kelly Dorgan’s presentation earlier in the day—a meandering scattershot of flashlights pinpointing the cracks and fissures of our small manmade excavations.    


Dorsal view of Nereis verins – image from Dorgan et al. 2007 research

In truth, I suppose it may be a poor metaphor.  A photoelastic stress analysis test requires the objects of investigation to be immersed in materials exhibiting the property of birefringence.  Birefringence is the result of light waves splitting into two unequally reflected or transmitted waves by an optically anisotropic medium.  Anisotropic objects are those that have different physical properties in different directions – the strength of wood along its grain vs. against, for example.   And, with the night as clear and dry as it was, well, we were all fairly well fixed in temperate atmospheric homogeneity.

Optical anisotropy.  Hmmm.  Setting those two words side by side it almost becomes another small meditation on the different properties of seeing—a la Phil’s blog from Sucia, maybe?   And, if I’m lucky, an acceptable segue into posting an image or two of something discussed over the course of the evening but never actually seen?  

Also black and white…  at least they resemble the chromatic theme of this particular blog post:



Haminoea from FHL’s website

The “bubble snails” Melanochlamys and Haminoea  are said to occupy territory on False Bay in the spring and summer.   

Too bad we missed them this year!



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