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 formulation of quantum mechanics, even unrealized possibilities contribute to the probability amplitudes of events in the universe. The universe is sometimes denoted as the cosmos or Nature, as in "cosmology" or "natural philosophy". Scientific experiments have yielded several general facts about the observable universe. The age of the universe is estimated to be 13.7±0.2 billion years. The universe is very large, possibly infinite, being at l

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z # TAGS