Complex Numbers

Turning Over a New Leaf

Here's a confession:

I'm not entirely confident when it comes to picture prompts.

But I do feel like it's important to try new things, to, as the kids say, step outside of my comfort zone and do something I'm not sure of, like this month's round of "Journalistic Intentions"  [18+].

One thing I continue to do: pick prompts at random. Today, we have this lovely photo of a leaf under a blanket of water: Orange Submersion  

I've seen reports that at least one person is having trouble with xlinks, so if that hyperlink doesn't work for you, I can provide the raw URL on request.

Ever wonder why water is (mostly) clear? I have. I mean, apart from when it's murky from suspended particles, or sometimes when mixed with delicious booze (which is itself, in its pure form, clear). And it's clearly (pun intended) not the same as air; you can almost always tell where one ends and the other begins. The surface of pure water is easy to identify, but, for me at least, damn near impossible to render in a drawing. But then, I've never been very good at drawing... but I digress.

The best answer to why water is clear that I've been able to come up with is that this is not the right question to ask.

Life crawled up onto land "only" about half a billion years ago. In comparison to the four billion or so years since life began on Earth, that's a significant fraction of time, but it means that life was changing and evolving for 7/8 of its history underwater. And some of that life, at least the animal portion, found a competitive edge in being able to directly sense prey or predators: in short, vision is a very useful sense to possess.

It's my understanding that eyes evolved several different times. That is, there's not one proto-organism that gradually turned light-sensitive cells (which many organisms have, not just animals) into an eyeball, which then split off into different species. No, the proto-organism might have been mostly blind, and some of its descendants developed vision in different ways: compound eyes like ours, or the simple eyes of arthropods and such, or whatever.

But most of those eyes originally evolved underwater. Thus, they developed in such a way that vision would be an evolutionary advantage, which means being sensitive to a range of the electromagnetic spectrum to which water is mostly transparent.

Water isn't clear because of some innate property of it; it's clear, to us, because our distant ancestors evolved a sense that allowed them to see in it. Water blocks some other wavelengths.

But the other thing it does is change the direction of light at its boundary. Stick your arm into a fish tank, and it'll appear to bend. At some angles, the light doesn't escape the water at all, but reflects off of it like a perfect mirror (this is a function of index of refraction, and it's also how fiber optic cables transmit data). The surface is also partially reflective when viewed from above, which is how you get the artistic dappled effect from ripples, like in today's picture prompt.

Leaf (pun absolutely intended) it to me to get all sciencey about a pretty picture. But I'm of the considered opinion that the knowledge gleaned from science can improve an aesthetic experience. I know the math and physics behind rainbows (or, well, I used to, and can easily find the information again), but that doesn't decrease one's visual impact.

And if today's discussion hurt your brain, just be glad I didn't go into the biology of what makes leaves turn color and fall off as winter approaches.

Another time, perhaps.