This is a fascinating question you pose, and for which I have thoughts I would like to share in response. My response is based not only on my personal beliefs, but knowledge gained through passionate and intense study and research pertaining to my innate desire and thirst to understand the nature of our purpose for existing, and how we are to achieve growth toward a divine level of wisdom and maturity through life on Earth.
Much of what I have learned has been gained through the intense and thorough research and reading of the life of Edgar Cayce, but not limited to just that. In short, I believe that we, as spiritual entities, are given the chance to grow and mature through the experiences in a physical plane of matter, specifically, Earth.
By being restricted in physical form, we are "gifted" with the consequences of choices made, by experiencing the resulting "reaction" of our Will exercized upon the natural laws of physics. Each thought, action, choice, idea, spoken word...in brief, ANY action expended by a person impacts what "was" just the present, and creates or directs us along a path in resonance with that action. If you know anything about quantum physics, it has (finally!) been observed that a quantum particle is affected by one's mere observation of it, which, once observed, collapses the potentially of what that particle may have become. THIS is a dimension not yet taught because science has not progressed enough to understand the full meaning of what they are observing.
Therefore, aside from dimensions I am as yet unlearned about, I believe in the following: matter (which I define as having height, width and depth), space (the vaccuum) and time, the latter of which is made possible only through the observation of one event in time (which has coordinates in space which will exist forever) and another event (another set of coordinates in space at a specific moment in time.)
Can one go back in time? Yes. But only to observe, and through that observation, they have the ability to create NEW paths to explore that will solidify in the physical universe, for the very act of thinking about what choices could have been made, instead of the ones that were made (and thereby led one to their current set of "coordinates" in space and time) can alter their future. This is ONLY possible through the expansion of sentient awareness and perception within oneself, and thus, do we grow in spirit and conscious awareness.
Renée