image of a small region of the sky, near the constellation Fornax. The light from the smallest, most redshifted galaxies originated roughly 13 billion years ago.]]The Universe is everything that physically exists: the entirety of space and time, all forms of matter, energy and momentum, and the physical laws and physical constants that govern them. In a well-defined, mathematical sense, the universe can even be said to contain that which does not exist; according to the path-integral formulat