The unification of the four fundamental forces is an active field of research. Up to now, no successful unified field theory has been formulated yet and the unified field force remains a hypothetical force. In spite of this situation, this goal continues to motivate research in theoretical physics. Scientists are clearly guided by a cosmological motivation. The unified field force would be the single force at the beginning of the universe and would evolve into the four fundamental forces as the temperature of the early universe decreased. A successful unified field theory must provide a realistic cosmological model. It should take into account the existence of quasars and other compact astronomical objects and be able to account for the mechanisms of such peculiar phenomena as the supernovae. An alternative unified field theory might exist and could start with new insights into the Lorentz transformations, the principle of special relativity, and the physical contents of these transformations. This book should be especially useful to professionals and students in elementary particle physics and astrophysics, or anyone else who is interested in the existence of the universe.