In optics, a caustic is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light.
A piece of milled plexiglass acting as a projecting lens; via the Computer Graphics and Geometry Lab at the École Polytechnique Fédérale de Lausanne
New milling techniques applied to glass and plexiglass panels could be used to “create windows that are also cryptic projectors, summoning ghostly images from sunlight.”
[Pauly and Bompas] hope that the technique will be used in architectural design, to create windows that mould sunlight and throw images or patterns onto walls or floors,” which, if timed, milled, and manipulated just right, could produce a slowly animated sequence of images being projected by an otherwise empty window during different times of day.
To control the shape of a caustic pattern generated by a specular or refractive surface, we need to solve the inverse problem: how can we change the surface geometry, such that incident light is redirected to produce a desired caustic image?
The [Lake Erie] ecosystem underwent a series of changes, each of which were related. There was an increase in the human population; which led to higher phosophorus levels in the water; which led, at last, to an increased level of algae in the lake. In effect, Lake Erie’s ecosystem was rewritten. Changed by human activities into…something else.
But Franklin cites the study because it’s doing something slightly novel: applying Selye’s principle of stress to ecological systems, suggesting that they are, much like humans, just as susceptible to external stressors. And I’ve been thinking about that a lot lately, especially this week. Because Franklin’s suggesting that the work begins not by “fixing the system.” Rather, she suggests it’s about shifting the priority a little: to removing whatever stress you can.