“Without vitamin C,” Anthony writes, “we cannot produce collagen, an essential component of bones, cartilage, tendons and other connective tissues. Collagen binds our wounds, but that binding is replaced continually throughout our lives. Thus in advanced scurvy”—reached when the body has gone too long without vitamin C—“old wounds long thought healed will magically, painfully reappear.”
In a sense, there is no such thing as healing. From paper cuts to surgical scars, our bodies are catalogues of wounds: imperfectly locked doors quietly waiting, sooner or later, to spring back open.
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.
I'd like to call the more general phenomenon that this is a specific instance of "ghost knowledge": It is knowledge that is present somewhere in the epistemic community, and is perhaps readily accessible to some central member of that community, but it is not really written down anywhere and it's not clear how to access it. Roughly what makes something ghost knowledge is two things:
It is readily discoverable if you have trusted access to expert members of the community.
It is almost completely inaccessible if you are not.
In this sense, most knowledge is ghost, particularly if you take an expansive view of what counts as an epistemic community.