In the framework of modern physics, including both classical mechanics and the theory of relativity, there is no concept of absolute rest or absolute motion. The principle of relativity, as formulated by Albert Einstein, states that the laws of physics are the same for all observers in uniform motion relative to each other. In other words, there is no privileged or preferred reference frame from which absolute rest or motion can be determined.
From this perspective, if something were to be considered at absolute rest, it would not grant it the status of a universal observer. In the absence of an absolute reference frame, all observers are considered to be on equal footing, regardless of their state of motion or rest. Different observers may measure different quantities, such as time intervals or lengths, depending on their relative motion, but all observations are considered valid from their respective frames of reference.
The concept of a universal observer, in the sense of an observer who can measure absolute rest or motion, is not compatible with the principles of modern physics. Instead, scientific theories and measurements are based on observations made within specific reference frames, relative to other objects or frames of reference.
It's also important to note that the nature of reality and the behavior of physical phenomena at extreme scales, such as those found in cosmology or quantum physics, are areas of active scientific research. Our understanding of these subjects continues to evolve as scientists explore and develop new theories and experimental techniques.