A novel and comprehensive ‘Dual-Energy’ Cosmological model (DEC) is shown to emerge from one principle. It sweepingly addresses problems in the current ΛCDM model from an initial singularity to dark energy. It follows from a new fundamental understanding of energy and gravity. This new understanding of energy and gravity is based on highly specific qualitative evidence from key cosmological features and the physical energy source for gravity. The evidence coherently suggests the presence of negative energy in space and a fundamental positive-negative symmetry of energy. Gravity is shown to be the fundamental mechanism that generates positive and negative energies from zero. In gravitational acceleration energy is gained at the expense of negative energy in space. A wide range of hard problems in current theory are naturally addressed. A discernable fault line in current theory emerges. The new model naturally provides physical definition for origin and expansion of the universe. A universe of positive energy arises naturally from zero in a ‘not quite so big’ bang with corresponding negative energy. The nature of the forces driving expansion and their direction are finally defined. Expansion is driven by repulsive gravitational forces between positive masses and surrounding voids dominated by negative energy. A higher order of symmetry in the evolution of the universe emerges. Spatial flatness emerges naturally. Isotropy with repetitive structures emerge from an origin of uniform mechanisms. Negative energy acts as a dynamically evolving property of space. The dual-energy principle naturally delivers both repulsive negative energy and the physical model for its increase. It addresses an observed accelerated expansion. The contrived concept of a positive dark energy becomes obsolete. An anti-de Sitter like character of space provides surprising support for string theory in AdS/CFT correspondence. Fundamental energy concepts in other areas of physics may be reevaluated. The fundamental physical properties of negative energy are to be explored.