According to Einstein's theory of relativity, both special and general, there is no concept of absolute rest. This idea challenges the traditional notion of absolute space and time, where objects can be considered at rest relative to some fixed reference frame.
The reason people do not believe in absolute rest in the context of relativity is due to the following key concepts:
Principle of Relativity: The principle of relativity, central to Einstein's theories, states that the laws of physics are the same in all inertial reference frames. An inertial reference frame is a coordinate system in which an object not subject to any external forces remains at a constant velocity (including being at rest). In other words, there is no preferred or special reference frame in the universe.
Special Theory of Relativity: In Einstein's special theory of relativity, he introduced the concept that the laws of physics, including the fundamental speed limit of light, are the same for all observers moving at constant velocities relative to each other. This theory postulates that the laws of physics should remain consistent regardless of the observer's motion. Therefore, there is no absolute rest frame that can be distinguished from other inertial frames.
General Theory of Relativity: Einstein's general theory of relativity builds upon the special theory and provides a framework for understanding gravity. In this theory, the presence of mass and energy curves the fabric of spacetime, causing objects to move along curved paths. The motion of objects is influenced by the distribution of matter and energy in the universe. In general relativity, there is no privileged reference frame because the geometry of spacetime is affected by the presence of matter and energy.
The combination of these concepts from special and general relativity suggests that there is no preferred or absolute reference frame in the universe. The laws of physics and the behavior of objects are relative to the observer's motion and the distribution of mass and energy in spacetime. Consequently, the idea of absolute rest is inconsistent with the principles of relativity, as supported by experimental observations and empirical evidence.