Let me combine my answer with a bit of history of science.
In his book 'Philosophiæ Naturalis Principia Mathematica' (for short: 'the Principia'), Newton argued that rotation is absolute. Newton used two lines of reasoning, one based on an everyday observation, and one based on a thought experiment.
The everyday observation:
Think of a bucket half-filled with water. When the water is circulating the surface of the water is concave, when the water is not circulating the surface is flat. The determining factor is whether the water is in circulating motion with respect to the overall environment. The bucket itself is closest to the water, but when you discount the effects from friction the state of motion of the bucket does not determine whether the surface of the water will be flat or concave.
The thought experiment:
Imagine two objects, at some measurable distance relative to each other. Imagine they are surrounded by empty space, there is no visible reference for motion. Question: are the two objects stationary, or are they in a state of circumnavigating their common center of mass? Newton argued the answer is obvious: if there is nothing connecting the two objects and their relative distance remains the same then they are not circumnavigating. For the two objects to be circumnavitating a centripetal force must be provided; a rope or string of whatever material must be present in order to provide the required centripetal force. Given the amount of inertial mass of each object you can infer the rotation rate from a measurement of the amount of tension of the rope.
The astronomer de Sitter (1873-1934) offered the following observation/reasoning:
When two celestial bodies orbit their common center of mass in an elliptical orbit then the following characteristics remain the same: the plane of the orbit keeps the same orientation (just as with circular orbits), and the ellipse keeps pointing in the same direction. That is, unless influenced by another celestial body the ellipse itself does not rotate in any way. Astronomical observations identified systems of double stars, with some of those systems showing an elliptical orbit. All the observations pointed in the direction of those elliptical orbits not rotating. This was strong corroborating evidence that the reference for rotation is the same everywhere in our galaxy. In other words, strong corroborating evidence that rotation is absolute.