Since Galileo’s time, it has been known that bodies that are not affected by any forces move in straight lines, that is, along the shortest path. William Hamilton formulated the principle that among all kinematically possible movements of a system from configuration A to configuration B, performed in the same period, the one for which the “Hamilton action” is the smallest is valid. The principle of least action is that the body moves so that the effort (which depends on the trajectory of movement) is minimal.
For example, there is a ball placed in an empty space. At some distance from it, there is an elastic wall. The desirable position of the ball would be in the same place after a while. Under these conditions, the ball can move in two different ways.: first, it can just stay in place, and second, one can push it against the wall. The ball will reach the wall, bounce off it, and bounce back. A person can push it at such a speed that it will return at precisely the right time.
This theory covers the cognitive factors of attention, focus, speed, and flexibility and covers many different fields, including various fields ranging from biology to design. For instance, the modern world desires to receive information as soon as possible. Therefore, this principle has become a leading direction in user experience (UX) digital design. UX presumes to interact with customers and deliver the requested information responsively. Keeping the principle of least action in mind, web designers started to use icons instead of lengthy descriptions to alleviate one’s understanding. Since the human brain can process visual images more quickly, such an approach helps them do things faster. This principle helped to reframe the existing web designs.