Mach's principle

Mach's principle is a hypothesis first stated by the physicist and philosopher Ernst Mach in 1893, which states that:

"The inertia of any system is the result of the interaction of that system and the rest of the universe. In other words, every particle in the universe ultimately has an effect on every other particle."

According to Mach's principle, which is an example of a relational theory, a single object in an otherwise empty Universe would feel no inertial forces. It would be impossible to determine whether the object is rotating or not. According to Mach, the inertial forces are caused by the existence of cosmic bodies such as the distant stars; rotation only make sense relatively to these other objects.

In this sense, Mach's principle can be said to be a form of philosophical holism.

Mach's principle has never developed into a quantitative physical theory that would explain a mechanism by which the stars can have such an effect. Although Albert Einstein was intrigued by Mach's principle, his general relativity does not agree with it.