[tianshuo]

A relevant article on rotational and relativity is: https://en.wikipedia.org/wiki/Absolute_rotation

Here's a simplified explanation.

Newton's Bucket is a thought experiment proposed by Isaac Newton, which he used to demonstrate the existence of absolute space. He imagined a bucket filled with water suspended by a cord. If the bucket is twisted, and then released, it begins to spin. As the bucket spins, the water inside it climbs up the sides, forming a concave surface. Newton argued that this change in the water's shape was due to its rotation relative to absolute space. Ernst Mach, a 19th-century physicist and philosopher, offered a different viewpoint. He suggested that instead of absolute space - the bucket can be seen as stationary while the universe is rotating, and the water would also have the same concave surface. This is known as Mach's Principle. According to General Relativity, a rotating universe can actually "drag" the space and time in it, affecting the spacetime of the bucket, so there doesn't need to be any centrifugal forces. This omits the need for any "absolute rotation" or "absolute coordinates".