White hole. In general relativity, a white hole is a hypothetical region of spacetime which cannot be entered from the outside, although matter and light can escape from it.
In this sense, it is the reverse of a black hole, which can only be entered from the outside, but from which nothing, including light, can escape. White holes appear in the theory of eternal black holes. In addition to a black hole region in the future, such a solution of the Einstein field equations has a white hole region in its past.[1] However, this region does not exist for black holes that have formed through gravitational collapse, nor are there any known physical processes through which a white hole could be formed.
Like black holes, white holes have properties like mass, charge, and angular momentum. In quantum mechanics, the black hole emits Hawking radiation and so can come to thermal equilibrium with a gas of radiation. Origin[edit] 1980s – present speculations[edit] See also[edit] References[edit] External links[edit] Big Bang. According to the Big Bang model, the universe expanded from an extremely dense and hot state and continues to expand today.
The graphic scheme above is an artist's concept illustrating the expansion of a portion of a flat universe. The Big Bang is the scientific theory that is most consistent with observations of the past and present states of the universe, and it is widely accepted within the scientific community. It offers a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background, large scale structure, and the Hubble diagram.[3] The core ideas of the Big Bang—the expansion, the early hot state, the formation of light elements, and the formation of galaxies—are derived from these and other observations.
As the distance between galaxies increases today, in the past galaxies were closer together. Overview Timeline of the Big Bang The earliest phases of the Big Bang are subject to much speculation. Elementary particle. In particle physics, an elementary particle or fundamental particle is a particle whose substructure is unknown, thus it is unknown whether it is composed of other particles.[1] Known elementary particles include the fundamental fermions (quarks, leptons, antiquarks, and antileptons), which generally are "matter particles" and "antimatter particles", as well as the fundamental bosons (gauge bosons and Higgs boson), which generally are "force particles" that mediate interactions among fermions.[1] A particle containing two or more elementary particles is a composite particle.
Everyday matter is composed of atoms, once presumed to be matter's elementary particles—atom meaning "indivisible" in Greek—although the atom's existence remained controversial until about 1910, as some leading physicists regarded molecules as mathematical illusions, and matter as ultimately composed of energy.[1][2] Soon, subatomic constituents of the atom were identified. Overview[edit] Main article: Standard Model. Hadron. In particle physics, a hadron i/ˈhædrɒn/ (Greek: ἁδρός, hadrós, "stout, thick") is a composite particle made of quarks held together by the strong force (in a similar way as molecules are held together by the electromagnetic force).
Of the hadrons, protons are stable, and neutrons bound within atomic nuclei are stable, whereas other hadrons are unstable under ordinary conditions; free neutrons decay with a half life of about 880 seconds. Experimentally, hadron physics is studied by colliding protons or nuclei of heavy elements such as lead, and detecting the debris in the produced particle showers. Etymology[edit] The term "hadron" was introduced by Lev B. Not withstanding the fact that this report deals with weak interactions, we shall frequently have to speak of strongly interacting particles. Properties[edit] All types of hadrons have zero total color charge. According to the quark model,[5] the properties of hadrons are primarily determined by their so-called valence quarks.