Physical cosmology

The universe comprises all of existence: all forms of matter and energy, and the structures they form, from sub-atomic particles to entire galactic filaments. Since the early 20th century, the field of cosmology establishes that space and time emerged together at the Big Bang ago and that the universe has been expanding since then. The portion of the universe that can be seen by humans is approximately 93 billion light-years in diameter at present, but the total size of the universe is not known.

hypothetical begin of the Universe through expansion out of an infinitely small and infinitely dense state

thumb|upright=1.35| Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the composite photo is an individual [[galaxy, some of them as old as 13.2 billion years; the observable universe is estimated to contain more than 2 trillion galaxies. From the Hubble eXtreme Deep Field.]]

thumb|upright|Spectral line|Absorption lines in the [[visible spectrum of a supercluster of distant galaxies (right), as compared to absorption lines in the visible spectrum of the Sun (left). Arrows indicate redshift. Wavelength increases up towards the red and beyond (frequency decreases).]]

The multiverse is the hypothetical set of all universes. Together, these universes are presumed to comprise everything that exists: the entirety of space, time, matter, energy, information, and the physical laws and constants that describe them. The different universes within the multiverse are called "parallel universes", "flat universes", "other universes", "alternate universes", "multiple universes", "plane universes", "parent and child universes", "many universes", or "many worlds". One common assumption is that the multiverse is a "patchwork quilt of separate universes all bound by the sa

thumb|The Big Bang theory of modern cosmology postulates the universe evolved from a hot dense state. Cosmogony, also spelled as cosmogeny, or cosmogenesis, is any model concerning the origin of the cosmos or the universe.

observation in physical cosmology

thumb|Stars rotating in the night sky The cosmos (, ; ) is an alternative name for the universe or its nature or order. Usage of the word cosmos implies viewing the universe as a complex and orderly system or entity.

branch of cosmology which studies mathematical models of the universe

thumb|250px|right|The globular cluster M80. Stars in globular clusters are mainly older metal-poor members of [[population II.]] In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-dark) matter in the universe is either hydrogen or helium, and astronomers use the word metals as convenient shorthand for all elements except hydrogen and helium. This word-use is distinct from the conventional chemical or physical definition of a metal as an electrically conducting element. Sta

hypothetical recollapse of the universe

philosophical consideration that observations of the Universe must be compatible with the conscious and sapient life that observes it

alternative to the Big Bang model of the evolution of the universe

dialogue by Plato

first image taken by the James Webb Space Telescope, of galaxy cluster SMACS 0723

cosmological contradiction between the observed darkness of the night sky and a static universe model

multiple exposure image of deep space in the constellation Ursa Major

astronomy dealing with objects outside the Milky Way

quantum field theory in which the three gauge groups of the standard model combine into subgroups of a larger gauge group

possible fate of universe in which all matter is torn apart by the gravitational influence of dark energy

history and future of the universe according to Big Bang cosmology

multiple exposure image of deep space in the constellation Fornax

topic in physical cosmology

physics thought experiment pointing out the improbability of the universe as described by thermodynamics

theoretical foundation of Newtonian mechanics

metric properties of the spacetime based on Albert Einstein's metric tensor and field solution for the spacetime

The term cosmography has two distinct meanings: traditionally it has been the protoscience of mapping the general features of the cosmos, heaven and Earth; more recently, it has been used to describe the ongoing effort to determine the large-scale features of the observable universe.

model in cosmology

visual illustration of the history of the Universe

field theory on a spacetime with small, compact extra dimensions beyond the large observed dimensions

Latin phrase meaning "out of nothing"

the proposition that the occurrence of life in the universe is very sensitive to the values of certain fundamental physical constants and that the observed values are, for some reason, improbable

astronomy debate held on 26 April 1920 at the Smithsonian Museum of Natural History between Harlow Shapley and Heber Curtis about whether spiral nebulae were different galaxies or part of the Milky Way

overview about the location of Earth in the Universe

spectral line of hydrogen state transitions

cosmological model involving repetitions of Big Bangs followed by Big Crunches

In physical cosmology, a protogalaxy, which could also be called a "primeval galaxy", is a cloud of gas which is forming into a galaxy. It is believed that the rate of star formation during this period of galactic evolution will determine whether a galaxy is a spiral or elliptical galaxy; a slower star formation tends to produce a spiral galaxy. The smaller clumps of gas in a protogalaxy form into stars.

name assigned to the average color of the universe

measurement of distance in which the change due to the expansion of the universe is factored out

period very shortly after the Big Bang where the universe was hotter than the grand unification scale

future scenario (heat death or the Big Freeze): observations suggest that the expansion of the universe will continue forever. If so, then a popular theory is that the universe will cool as it expands, eventually becoming too cold to sustain life

parameter which characterizes the expansion of the universe

period in the evolution of the early universe prior to hadron confinement, during which the universe consisted of quark–gluon plasma

model of the universe that is not expanding or contracting, e.g. one in which the cosmological constant exactly balances things

the maximum distance from which light from particles could have traveled to the observer during the age of the universe

several theories in particle physics and cosmology related to superstring theory and M-theory

theoretical component of a galaxy that envelops the galactic disc and extends well beyond the edge of the visible galaxy

cosmological solution to the Einstein field equations of general relativity

hypothetical cosmological model for the origin of the known universe

period in the evolution of the early universe

theories attempting to explain the deficiencies of the Standard Model, Quantum field theory and general relativity

attempts to develop a quantum mechanical theory of cosmology

cosmology

period (~1 to 10 seconds after the Big Bang) in the early universe in which leptons dominated the mass of the Universe, after hadron–antihadron annihilation ended the hadron epoch but before Big Bang nucleosynthesis and the photon epoch

in ancient cosmological models, rotating spheres made of aether in which the stars or planets are embedded

period in the evolution of the early universe in which photons dominated the energy of the universe

multiple exposure image of deep space in the constellation Tucana

book by Lawrence Krauss

epoch at which charged electrons and protons first became bound to form electrically neutral hydrogen atoms, around 378 thousand years after the Big Bang

cosmological model which identifies the Big Bang with a collision between branes and which solves the flatness and homogeneity problems via the flatness of the branes without invoking inflation