Path of least resistance
The path of least resistance is the physical or metaphorical pathway that provides the least resistance to forward motion by a given object or entity, among a set of alternative paths. The concept is often used to describe why an object or entity takes a given path.
Description
In physics, the "path of least resistance" is a heuristic from folk physics that can sometimes, in very simple situations, describe approximately what happens. Other examples are "what goes up must come down" and "heat goes from hot to cold". But these simple descriptions are not derived from laws of physics and in more complicated cases these heuristics will fail to give even approximately correct results. In electrical circuits, for example, current always follows all available paths, and in some simple cases the "path of least resistance" will take up most of the current, but this will not be generally true in even slightly more complicated circuits. For example, if there are three paths of nearly the same resistance, the "path of least resistance" will only take up about a third of the current, and a path with nearly zero resistance will take up NO current if there is no potential difference between the ends of the path.
The path of least resistance is also used to describe certain human behaviors, although with much less specificity than in the strict physical sense. In these cases, resistance is often used as a metaphor for personal effort or confrontation; a person taking the path of least resistance avoids these. In library science and technical writing, information is ideally arranged for users according to the Principle of least effort, or the path of least resistance. Recursive navigation systems are an example of this.
Note: The path of least resistance applies on a local, not global, reference. For example, water always flows downhill, regardless of whether briefly flowing uphill will help it gain a lower final altitude (with certain exceptions such as superfluids). In physics, this phenomenon allows the formation of potential wells, where potential energy is stored because of a barrier restricting flow to a lower energy state.