Having been away for the morning, we felt the need to be outside. We departed together and within a hundred yards I stooped to look, like a kid hunting for seashells among the flotsam deposited by the tide’s last reach. Joanna walked on without me.

Although we call it Avogadro’s Number, after Amedeo Avogadro, its discovery resulted from the work of others (notably Brown (of Motion fame) and Millikan (of Oil Drop fame)). The findings of all of these scientists revealed that a mole quantity of a chemical substance is comprised of  6.02 X 10 23 molecules. Would it surprise you to know that a single drop of water contains 1.39 X 10 21 molecules? Although that’s an impressive number, I derive more satisfaction from knowing how it is that liquid water may form a solid. The liquid is able to make this remarkable transformation because of the way in which its component molecules interact and pack together, especially at low temperature. When temperature declines, so too does the energy of an individual water molecule and, as a result, each moves about less rapidly. As motion slows, the molecules are less able to resist the magnetic attraction they have for their neighbors. [I could wax poetic about the nature of the water’s polar covalent bond, but will spare you, dear reader.] As temperature continues to fall, the attraction between molecules increases and eventually they become linked by hydrogen bonds. The fascinating thing about water is that its molecules pack together less closely (because of limitations imposed by the hydrogen bonds themselves) at temperatures which lead to the formation of ice than they do at temperatures which allow for the formation of liquid water. And that is why ice is less dense than liquid water. And that is why ponds freeze from the top down, rather than the other way around. But, I digress.

What intrigue me about both of the images obtained on this particular day are the incidental elements found in them. The first demonstrates the phenomenon of interference, and the second records the movements of light as it reflects from the surface of the water. The interference pattern reminds me of workbook exercises from high school physics class, while the patterns of reflected light remind me of the adhesive byssus threads of marine bivalve molluscs. I was tempted to present a third image, but thought better of it. If you’re interested, click here to view a tightly cropped and highly modified version of another photo captured in a series which includes the second shown here. The result reminds me of plasma exploding off the surface of the sun and then streaming out and back, along magnetic fields, to create a solar flare.



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