What is the universe?

The universe is defined as all space and time in the physical sense (collectively referred to as space-time) and its connotation, including all forms of energy, such as electromagnetic radiation, ordinary matter, dark matter, dark energy and so on. Among them, ordinary matter includes planets, satellites, stars, galaxies, clusters of galaxies and intergalactic matter. The universe also includes physical laws that affect matter and energy, such as conservation laws, classical mechanics, relativity and so on.