Abstract
In fundamental theories of physics, the dynamical equations all have time inversion invariance. Except for the evolution of some simple system which has realistic inverse processes, but for a slightly more complicated system, the evolution processes are irreversible. This is the problem of arrow of time, which is always warmly debated. In different point of view, we find there may have some conceptual misunderstanding in the controversy: 1) The realization of an inverse process does not mean the time of the system goes backward. 2) The principles of relativity and covariance are the constraints to physical laws, but not constraints to specific solutions. The equations must be covariant, but the solutions are not definitely symmetric. 3) Time is a global property of the universe, which is a measurement of the evolution process of the universe. The internal time of a matter system reflecting its internal evolution speed also takes this cosmic time as a unified background and standard of measurement. 4) The universe has a unified cosmic time T and a cosmic space related to this cosmic time. They are objective and absolute. 5) The eigensolution of a spinor is a critical state losing time concept, which responses the interaction of environment with some uncertainty, then the evolution process of the world is not uniquely determined. 6) The non-uniqueness of the evolution process means that the inverse process is absent. So for a world including spinors, the evolution is essentially irreversible. In this paper, according to the widely accepted principles and direct calculations of transformation, we reveal the misunderstandings in the usual controversy, and then give more natural and reasonable explanations for structure of space-time and arrow of time.
Highlights
In fundamental theories of physics such as Newtonian mechanics, electrodynamics, quantum mechanics, the dynamical equations all have time inversion invariance
In different point of view, we find there may have some conceptual misunderstanding in the controversy: 1) The realization of an inverse process does not mean the time of the system goes backward; 2) The principles of relativity and covariance are the constraints to physical laws, but not constraints to specific solutions
The internal time of a matter system reflecting its internal evolution speed takes this cosmic time as a unified background and standard of measurement; 4) The universe has a unified cosmic time T and a cosmic space related to this cosmic time
Summary
In fundamental theories of physics such as Newtonian mechanics, electrodynamics, quantum mechanics, the dynamical equations all have time inversion invariance. The universe has a unique and unified cosmic time, and it always goes unidirectionally forward. Related to this cosmic time we have the specific state of universe at some time, which forms the cosmic space and the existences. There is an internal time to reflect the evolution process of a system, just like the history and lifetime of a man, which is the proper time of the system This proper time takes the cosmic time as a unified background and a measuring standard. Since the total universe is a realistic solution of all physical laws This solution is objective, and it does not definitely have the symmetry of the equations. We give some detailed discussion for the structure of the space-time and relative symmetries of the transformation through specific calculations and explanations
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