Recently, the electromagnetic duality with fields and field sources has been studied and magnetic monopoles have been searched for. Elementary particles are then seen to have canonical properties and to be divided into the leptons and baryons as well as the visible and invisible particles. Next, non-composite elementary particles are fermions. The motivation of my research work is the search for an alternative unified field theory and a realistic cosmological model. The present work tackles this search. More developments of the electromagnetic theory are derived in this one. For non-accelerating particles, Maxwell’s equations and the electromagnetic force, for example, are derived by means of the theory of special relativity. The electromagnetic field and potential produced by an accelerating electric monopole are derived by means of a new theory of general relativity. The gravitational force is revisited, the standard model of elementary particles is revised, and a cosmological model is proposed. 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.