“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.
Forest Therapy, also known as “Shinrin-yoku,” refers to the practice of spending time in forested areas for the purpose of enhancing health, wellness, and happiness. The practice follows the general principle that it is beneficial to spend time bathing in the atmosphere of the forest. The Japanese words translate into English as “Forest Bathing.”
Wang tiles (Hao Wang, 1961) are a class of formal systems. They are modelled visually by square tiles with a color on each side. A set of such tiles is selected, and copies of the tiles are arranged side by side with matching colors, without rotating or reflecting them.
The basic question about a set of Wang tiles is whether it can tile the plane or not, i.e., whether an entire infinite plane can be filled this way. The next question is whether this can be done in a periodic pattern.
In 1966, Wang's student Robert Berger solved the problem in the negative. He proved that no algorithm for the problem can exist, by showing how to translate any Turing machine into a set of Wang tiles that tiles the plane if and only if the Turing machine does not halt. The undecidability of the halting problem then implies the undecidability of Wang's tiling problem.