Universe

physical worldThe Universeuniversesuniversalheavenscosmosphysical universesizesize of the universeworld
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.wikipedia
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Observable universe

large-scale structure of the universelarge-scale structurelarge-scale structure of the cosmos
While the spatial size of the entire Universe is unknown, it is possible to measure the size of the observable universe, which is currently estimated to be 93 billion light-years in diameter.
The observable universe is a spherical region of the universe comprising all matter that can be observed from Earth or its space-based telescopes and exploratory probes at the present time, because electromagnetic radiation from these objects has had time to reach the Solar System and Earth since the beginning of the cosmological expansion.

Multiverse

parallel universesparallel universemultiversal
In various multiverse hypotheses, a universe is one of many causally disconnected constituent parts of a larger multiverse, which itself comprises all of space and time and its contents; as a consequence, ‘the Universe’ and ‘the multiverse’ are synonymous in such theories.
The multiverse, also known as a maniverse, megaverse, metaverse, omniverse, or meta-universe, is a hypothetical group of multiple universes.

Space

spatialphysical spacereal space
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
The concept of space is considered to be of fundamental importance to an understanding of the physical universe.

Geocentric model

geocentricPtolemaic systemPtolemaic
The earliest cosmological models of the Universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the center.
In astronomy, the geocentric model (also known as geocentrism, often exemplified specifically by the Ptolemaic system) is a superseded description of the Universe with Earth at the center.

Timeline of cosmological theories

cosmological modelscosmologyhistory of cosmology
The earliest cosmological models of the Universe were developed by ancient Greek and Indian philosophers and were geocentric, placing Earth at the center.

Milky Way

Milky Way Galaxygalaxyour galaxy
Further observational improvements led to the realization that the Sun is one of hundreds of billions of stars in the Milky Way, which is one of at least hundreds of billions of galaxies in the Universe.
Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe.

Dark matter

dark matter detectiondark-mattermissing mass
Dark matter gradually gathered, forming a foam-like structure of filaments and voids under the influence of gravity.
Dark matter is a form of matter thought to account for approximately 85% of the matter in the universe and about a quarter of its total energy density.

Causality

causalcause and effectcausation
In various multiverse hypotheses, a universe is one of many causally disconnected constituent parts of a larger multiverse, which itself comprises all of space and time and its contents; as a consequence, ‘the Universe’ and ‘the multiverse’ are synonymous in such theories.
The deterministic world-view holds that the history of the universe can be exhaustively represented as a progression of events following one after as cause and effect.

Void (astronomy)

voidvoidscosmic void
Dark matter gradually gathered, forming a foam-like structure of filaments and voids under the influence of gravity. At smaller scales, galaxies are distributed in clusters and superclusters which form immense filaments and voids in space, creating a vast foam-like structure.
Cosmic voids are vast spaces between filaments (the largest-scale structures in the universe), which contain very few or no galaxies.

Hydrogen

HH 2 hydrogen gas
Giant clouds of hydrogen and helium were gradually drawn to the places where dark matter was most dense, forming the first galaxies, stars, and everything else seen today.
Hydrogen is the most abundant chemical substance in the Universe, constituting roughly 75% of all baryonic mass. Non-remnant stars are mainly composed of hydrogen in the plasma state.

Helium

Hehelium IIsuperfluid helium
Giant clouds of hydrogen and helium were gradually drawn to the places where dark matter was most dense, forming the first galaxies, stars, and everything else seen today.
Helium is the second lightest and second most abundant element in the observable universe (hydrogen is the lightest and most abundant).

Inflationary epoch

inflation
After an initial accelerated expansion called the inflationary epoch at around 10 −32 seconds, and the separation of the four known fundamental forces, the Universe gradually cooled and continued to expand, allowing the first subatomic particles and simple atoms to form.
In physical cosmology the inflationary epoch was the period in the evolution of the early universe when, according to inflation theory, the universe underwent an extremely rapid exponential expansion.

Heliocentrism

heliocentricheliocentric modelheliocentric theory
Over the centuries, more precise astronomical observations led Nicolaus Copernicus to develop the heliocentric model with the Sun at the center of the Solar System.
The non-geocentric model of the Universe was proposed by the Pythagorean philosopher Philolaus (d.

Galaxy

galaxiesgalacticgalactic nuclei
The Universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.
In the astronomical literature, the capitalized word "Galaxy" is often used to refer to our galaxy, the Milky Way, to distinguish it from the other galaxies in our universe.

Theory of everything

theories of everythingeverythingattempt to explain all
The same synonyms are found in English, such as everything (as in the theory of everything), the cosmos (as in cosmology), the world (as in the many-worlds interpretation), and nature (as in natural laws or natural philosophy).
A theory of everything (TOE or ToE), final theory, ultimate theory, or master theory is a hypothetical single, all-encompassing, coherent theoretical framework of physics that fully explains and links together all physical aspects of the universe.

Nature

naturalnatural worldmaterial world
The same synonyms are found in English, such as everything (as in the theory of everything), the cosmos (as in cosmology), the world (as in the many-worlds interpretation), and nature (as in natural laws or natural philosophy).
Nature, in the broadest sense, is the natural, physical, or material world or universe.

Cosmos

cosmicKosmosorder
Another synonym was ὁ κόσμος, ho kósmos (meaning the world, the cosmos).
The cosmos is the Universe.

Cosmology

cosmologistcosmologicalcosmologies
The same synonyms are found in English, such as everything (as in the theory of everything), the cosmos (as in cosmology), the world (as in the many-worlds interpretation), and nature (as in natural laws or natural philosophy). The Big Bang theory is the prevailing cosmological description of the development of the Universe.
Cosmology (from the Greek κόσμος, kosmos "world" and -λογία, -logia "study of") is a branch of astronomy concerned with the studies of the origin and evolution of the universe, from the Big Bang to today and on into the future.

World

the worldGlobalWorldwide
Another synonym was ὁ κόσμος, ho kósmos (meaning the world, the cosmos).
In a philosophical context, the "world" is the whole of the physical Universe, or an ontological world (the "world" of an individual).

Big Bang

Big Bang theoryThe Big Bangbig-bang
The Big Bang theory is the prevailing cosmological description of the development of the Universe.
Lemaître also proposed what became known as the "Big Bang theory" of the creation of the universe, originally calling it the "hypothesis of the primeval atom": in his paper Annales de la Société Scientifique de Bruxelles (Annals of the Scientific Society of Brussels) under the title Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extragalactiques ("A homogeneous Universe of constant mass and growing radius accounting for the radial velocity of extragalactic nebulae"), he presented his idea that the universe is expanding and provided the first observational estimation of what is known as the Hubble constant.

Solar System

outer Solar Systeminner Solar Systemouter planets
Over the centuries, more precise astronomical observations led Nicolaus Copernicus to develop the heliocentric model with the Sun at the center of the Solar System.
Most people up to the Late Middle Ages–Renaissance believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky.

Natural philosophy

natural philosophernatural philosophersNatural
The same synonyms are found in English, such as everything (as in the theory of everything), the cosmos (as in cosmology), the world (as in the many-worlds interpretation), and nature (as in natural laws or natural philosophy).
Natural philosophy or philosophy of nature (from Latin philosophia naturalis) was the philosophical study of nature and the physical universe that was dominant before the development of modern science.

Inflation (cosmology)

cosmic inflationinflationcosmological inflation
Since the Planck epoch, space has been expanding to its present scale, with a very short but intense period of cosmic inflation believed to have occurred within the first 10 −32 seconds.
In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe.

Cold dark matter

coldCDMCold Dark Matter (CDM)
A version of the model with a cosmological constant (Lambda) and cold dark matter, known as the Lambda-CDM model, is the simplest model that provides a reasonably good account of various observations about the Universe.
Observations indicate that approximately 85% of the matter in the universe is dark matter, with only a small fraction being the ordinary baryonic matter that composes stars, planets, and living organisms.

Everything

all-thingsTotality
The Universe is often defined as "the totality of existence", or everything that exists, everything that has existed, and everything that will exist.
The Universe is everything that exists theoretically, though a multiverse may exist according to theoretical cosmology predictions.