This subcategory gathers theories belonging to physics: the laws and models of matter, energy, motion, forces and the universe's fundamental structure, at scales from subatomic particles to the observable cosmos, including mechanics, thermodynamics, electromagnetism, relativity and quantum theory. A theory placed here explains a physical phenomenon through a mathematical law or a model tested by experiment, distinct from a theory that primarily explains a chemical reaction, an astronomical structure, or a living system's biology, which belong to their own subcategories.