What is Mach's principle?

Mach's principle is a concept in physics that suggests that the inertial properties of an object are influenced by the presence and distribution of mass in the universe. It is named after the Austrian physicist Ernst Mach, who articulated this idea in the 19th century. The essence of Mach's principle is that the inertia of a body is not an intrinsic property but rather depends on the gravitational effects of all other mass in the universe. In other words, local inertial frames are influenced by the mass and motion of distant objects. This idea implies a relational view of motion, contrasting with the notion of absolute space and time as proposed by Newton. Although Mach's principle has not been formulated in a precise mathematical framework and is somewhat controversial, it has inspired various theories in physics, including aspects of general relativity. Einstein, for instance, was influenced by Mach's ideas when developing his theory, as he sought to incorporate the role of mass and energy in the geometry of spacetime. In summary, Mach's principle explores the interconnectedness of inertia and gravitational interactions in the cosmos, suggesting that an object's resistance to acceleration is somehow tied to the mass of all other entities in the universe.