The objective is to find a unified description of physical properties which applies at the small (atomic) scale and at the large (cosmological) scale. The starting point is the General Theory of Relativity. Light is described as a wave disturbance of spacetime propagating through space. The light interference experiment is discussed in detail considering light as a real physical wave passing through the apparatus and interacting with the detector so that probabilistic effects take place at the point of detection. The nature of mass and the nature of charge are explained. The concepts of force and field are shown to be dependent attributes and all properties are shown to be derived from spacetime. The nature of protons, neutrons and electrons as looped waves in spacetime is analysed with the implications for experimental observations. The unification of the four fundamental forces is achieved by recognising that the property "force" is not fundamental. The forces (gravitational, electromagnetic, strong and weak nuclear) arise as a result of differences in energy between possible positions of objects in spacetime. The forces arise in each case due to the context in which they occur. The Theory of Everything (TOE) or master theory question is resolved by showing that the core theory equations are the Einstein equations of GR with a cosmological constant of zero.