diffraction / photography

Everyday Diffraction

by Nancy Roth · Published July 28, 2020 · Updated January 31, 2022

Diffraction is a phenomenon associated with the behaviour of light, a kind a scattering, or bending when it passes through a “grating,” or narrowed area. The same term may also apply to other kinds of matter moving in a discernible direction, such as water or air. It is relatively easy to think of examples that you might set up, or build, the way you’d set up an experiment. It’s more challenging to think of examples in very ordinary situations, perhaps because we need to start thinking about things that never seemed to bear thinking about before. It seems, for example, that the lens on a camera — or the lens in one’s own eye — is designed to correct for the diffraction of light that passes through the small shutter of the camera, or the pupil of the eye.

Everyday diffraction could be a name for an awareness of matter in constant motion — of particles of varying size and speed and “spin” being focussed or scattered, bumping into things, changing direction, becoming entangled, etc.

The idea of photograph as measurement begins to make sense against this background: a record of light on the sensitive surface appears, to human senses, to “stop” the motion.

Tags: Diffraction

The idea comes from particle physics, from the effort to measure matter — particles — and getting mixed up with them. Heisenberg talked about the uncertainty of the resulting measurement. But that seems to keep the distinction between the measurer and the measured intact: the measurer just can’t quite be sure whether the result is accurate. Bohr spoke of indeterminacy, which seems to imply more: that the identities of measurer, measured and apparatus are all fluid.

Karen Barad’s book Meeting the Universe Halfway has been reverberating in my mind since I first read it, just over two years ago. Barad is a particle physicist, a feminist, and the designer of a philosophical position she calls agential realism. It positions us, human beings, as both observing and consisting of matter, both examining aspects of reality and participating in it.

On this site, I’m trying to adapt these ideas to my own purposes, to grasp the crucial terms — intra-action, uncertainty, indeterminacy, diffraction, measurement, entanglement as they might apply to familiar experiences. I want to “translate,” that is, from the context of particle physics into the language English-speakers use to describe transactions with matter and their intra-action with what matters, such as air, water, plants, trees and one another. Barad has made a very strong start.

As I finished my first reading of the book, it seemed to say that human beings would do well to approach matter — including themselves and one another — with broad humility, restraint and wonder. This voice from an utterly unfamiliar world, had a stronger authority for me than any religious teaching I have encountered so far.