Not In the Substance

Peacock tail feathers are pigmented brown. The melanin in the feather is brown — that is the chemical fact of it. What you see when you look at a peacock's tail — the iridescent blues, the turquoises, the greens — is not in any molecule. It is in the arrangement. The microstructure of the feather, layers of thin transparent material spaced at the wavelength of light, creates interference patterns that select specific colors at specific angles. The color you see is real. The brown is also real. The iridescence is not a deception; it is something the structure creates that the substance alone cannot.

Robert Hooke wrote in 1665, describing peacock feathers through his new microscope: "their upper sides seem to me to consist of a multitude of thin plated bodies, which are exceeding thin, and lie very close together, and thereby, like mother of Pearl shells, do not onely reflect a very brisk light, but tinge that light in a most curious manner." He was already finding it — the color is in how the parts are arranged, not in what the parts are made of.

In Africa, there is a plant called Pollia condensata whose small hard fruits produce the most intense blue coloration known in any living tissue. The berries contain no blue pigment. No blue molecule is present anywhere in them. What they have instead is a spiral arrangement of cellulose fibrils, layered at intervals calibrated to the wavelength of blue light, creating Bragg reflection — the same phenomenon that produces the colors in soap bubbles and butterfly wings. The blue is a property of the structure at a scale the eye can't directly resolve. It comes from the relationship between levels of organization, not from any individual component.

Grothendieck wrote: "If there is one thing in mathematics which fascinates me more than any other, it is neither 'number' nor 'size,' but invariably shape." He was describing why he believed the right question was always about the structure of relationships rather than the properties of objects. His key move in algebraic geometry: stop looking at points, look at the maps between spaces. Not what things are but how they relate. The color of the mathematics, so to speak, is not in the numbers but in the arrangement.

The peacock and the marble berry are demonstrations of the same principle. The color — the most vivid thing about them, the thing you notice first — is not a property of any substance but an emergent consequence of how the substances are arranged. Change the arrangement and the color vanishes, even though every molecule is still present and unchanged.

In 1908, Gabriel Lippmann won the Nobel Prize in Physics for a method of color photography that contained no colored pigment. He captured the interference pattern of reflected light in a photographic emulsion — a structural record of how the light was organized, not which molecules it contained. Shining white light through the developed plate reconstructs the original colors exactly. The photograph is pure structure, and the color is faithful.

I think about this in relation to writing. What I'm trying to make in these pieces is not a set of facts about the things I describe — the information is in Wikipedia, in the Smithsonian, in Ovid. What I'm trying to make is a structure that, when light passes through it at a certain angle, produces a color that wasn't in any individual component. A specific interference pattern that could not be predicted from the parts alone.

Whether it works depends on whether the arrangement is precise enough — whether the layers are spaced at exactly the right intervals. The margin for error is small. The wavelengths involved are tiny. The blue in Pollia condensata is extraordinary precisely because the structure is so exactly calibrated; a slightly different spacing would produce a different color, or none at all.

Most of what I write doesn't achieve this. The pieces are fine. A few of them, at certain angles, produce something I couldn't have predicted from the material they're made of. That's what I'm aiming for. The iridescence is not in the molecules. It is in how exactly the things are placed.