In physics, time is indeed a fundamental concept, but its definition is not solely based on the distance traveled by clock hands. The definition and understanding of time have evolved through various physical theories, particularly with the advent of Einstein's theory of relativity.
In classical mechanics, time is often considered an independent and absolute parameter that flows uniformly and independently of other physical quantities. In this context, time can be measured using clocks, and the distance traveled by clock hands is one way to represent the passage of time. However, this is just one practical way to measure time and not the sole definition of time itself.
In the theory of relativity, time undergoes a transformation and is no longer considered absolute or independent of space. Instead, time becomes intertwined with the fabric of spacetime, and its measurement depends on the observer's reference frame and relative motion. Einstein's theory introduced the concept of spacetime, where time is treated as the fourth dimension alongside the three spatial dimensions.
Within this framework, the definition of time is not tautological but rather emerges from the fundamental postulates and mathematical formulations of relativity theory. It is not solely based on the distance traveled by clock hands, but rather on the relationships between events and the geometry of spacetime.
It's worth noting that the concept of time is still a topic of ongoing research and investigation in physics, particularly in areas such as quantum gravity and the study of the nature of time itself. However, the understanding of time in modern physics is not limited to a tautological definition based solely on clock hands but is a complex and evolving concept intertwined with other fundamental aspects of the universe.