John Archibald Wheeler was an American theoretical physicist. He was largely responsible for reviving interest in general relativity in the United States after World War II. Wheeler also worked with Niels Bohr in explaining the basic principles behind nuclear fission. Together with Gregory Breit, Wheeler developed the concept of the Breit–Wheeler process. He is best known for linking the term "black hole" to objects with gravitational collapse already predicted early in the 20th century, for coining the terms "quantum foam", "neutron moderator", "wormhole" and "it from bit", and for hypothesizing the "one-electron universe".
Wheeler speculated that reality is created by observers in the universe. "How does something arise from nothing?", he asked about the existence of space and time. He also coined the term "Participatory Anthropic Principle" (PAP), a version of a Strong Anthropic Principle. In 1990, Wheeler suggested that information is fundamental to the physics of the universe. According to this "it from bit" doctrine, all things physical are information-theoretic in origin.