What is universe?

Answer 1

u·ni·verse (yū'nə-vûrs')
n.
All matter and energy, including the earth, the galaxies, and the contents of intergalactic space, regarded as a whole.

The earth together with all its inhabitants and created things.
The human race.
The sphere or realm in which something exists or takes place.

universe

noun

The totality of all existing things: cosmos, creation, macrocosm, nature, world. See matter, part/whole.
The human race: earth, flesh, Homo sapiens, humanity, humankind, man, mankind, world.

universe
n
Definition: everything in creation
Antonyms: locality


universe, totality of matter and energy in existence. The study of the origin of the universe, or cosmos, is known as cosmogony, and that of its structure and evolution, cosmology. The age of the universe depends on which theory of cosmology one accepts. According to the big bang theory, favored by most scientists, the universe is between 10 and 20 billion years old. The steady-state theory holds that the universe has been in existence for all time.
Matter and Energy in the Universe

The matter in the universe is subject to various forces, but the greatest force on the cosmological scale is gravitation. This force pulls matter together to form stars, which either exist alone or are part of binary star or multiple star systems, or brown dwarfs, which are also known as “failed stars.” Gravitation also acts to group billions of stars into galaxies and to group galaxies into clusters and superclusters. The main source of energy in the universe is the conversion of the matter of the stars into energy through thermonuclear reactions (see nuclear energy). These reactions continue throughout the different stages of stellar evolution (see also stellar populations) until the star has consumed all its available nuclear fuel.

The Size and Shape of the Universe

The first systematic theory of the size and shape of the universe that attempted to explain observed data was constructed by Ptolemy in the 2d cent. In this theory the solar system was thought to be the entire universe, with the earth at its center and the distant stars located just beyond the farthest planet. This belief was held until the 16th cent., when Copernicus advanced the idea that the sun, rather than the earth, is at the center of the system and that the stars are at very great distances compared to the planets. During the first part of the 20th cent., astronomers discovered that the sun is only one of billions of stars in the Milky Way galaxy and is located far from the galactic center.

Estimates of the size of the universe have been refined as methods of measuring galactic and extragalactic distances have improved. Close stellar distances were at first found by measuring a star's trigonometric parallax. A more powerful contemporary method is to analyze the light reaching the earth from an object by means of a spectroscope; the distance of a very faint object can be estimated by comparing its apparent brightness to those of similar objects at known distances. Another method depends on the fact that the universe as a whole appears to be expanding, as indicated by red shifts (see Doppler effect) in the spectral lines of distant galaxies. Hubble's law makes it possible to estimate their distances from the speed with which they are rushing away from the earth. At present the universe is believed to be at least 10 billion light-years in diameter. One problem with estimating the size of the universe is that space itself (or more properly, space-time) may be curved, as held by the general theory of relativity. This curvature would affect measurements of distance based on the passage of light through space from objects as far away as 5 billion light-years or more.

universe

IN BRIEF: All space and everything in it.

The noun universe has 4 meanings:

Meaning #1: everything that exists anywhere
Synonyms: existence, creation, world, cosmos, macrocosm


Meaning #2: the whole collection of existing things
Synonym: cosmos


Meaning #3: (statistics) the entire aggregation of items from which samples can be drawn
Synonym: population


Meaning #4: everything stated or assumed in a given discussion
Synonym: universe of discourse


universe




The deepest visible-light image of the cosmos, the Hubble Ultra Deep Field.The term universe has a variety of meanings based on the context in which it is described.

In materialist philosophical terms, the universe is the summation of all matter that exists and the space in which all events occur which has an equivalent idea amongst some theoretical scientists most noted Brackus Mons known as the total universe. In cosmological terms, the universe is thought to be a finite or infinite space-time continuum in which all matter and energy exist. (It has been hypothesized by some scientists that the universe may be part of a system of many other universes, known as the multiverse.)

The terms known universe, observable universe, or visible universe are often used to describe the part of the universe that can be seen or otherwise observed by humanity. Because cosmic inflation removes vast parts of the total universe from our observable horizon, most cosmologists accept that it is impossible to observe the whole continuum and may use the expression our universe, referring only to that knowable by human beings in particular.

Expansion and age, and the Big Bang theory
Main article: Age of the universe
The most important result of cosmology, the understanding that the universe is expanding, is derived from redshift observations and quantified by Hubble's Law. Extrapolating this expansion back in time, one approaches a gravitational singularity, a rather abstract mathematical concept, which may or may not correspond to reality. This gives rise to the Big Bang theory, the dominant model in cosmology today. The age of the universe from the time of the Big Bang, was estimated to be about 13.7 billion (13.7 × 109) years, with a margin of error of about 1 % (± 200 million years), according to NASA's WMAP (Wilkinson Microwave Anisotropy Probe). However, this is based on the assumption that the underlying model used for data analysis is correct. Other methods of estimating the age of the universe give different ages.

A fundamental aspect of the Big Bang can be seen today in the observation that the farther away from us galaxies are, the faster they move away from us. It can also be seen in the cosmic microwave background radiation which is the much-attenuated radiation that originated soon after the Big Bang. This background radiation is remarkably uniform in all directions, which cosmologists have attempted to explain by an early period of inflationary expansion following the Big Bang.

Size of the universe and observable universe
Main article: Observable universe
There is disagreement over whether the universe is indeed finite or infinite in spatial extent and volume. Many astronomers and cosmologists believe the universe is infinite due to recent findings in NASA's WMAP project supporting a flat (therefore infinite) universe.

However, the observable universe, consisting of all locations that could have affected us since the Big Bang given the finite speed of light, is certainly finite. The edge of the cosmic light horizon is 13.7 billion light years (4.19 Gpc) distant. The present distance (comoving distance) to the edge of the observable universe is larger, due to the ever increasing rate at which the universe has been expanding; it is estimated to be about 78 billion light years (7.8 × 1010 light years, or 7.4 × 1026 m). This would make the comoving volume, of the known universe, equal to 1.9 × 1033 cubic light years (assuming this region is perfectly spherical). The observable universe contains about 7 × 1022 stars, organized in about 100 billion galaxies, which themselves form clusters and superclusters. The number of galaxies may be even larger, based on the Hubble Deep Field observed with the Hubble Space Telescope. The Hubble Space Telescope discovered galaxies such as Abell 1835 IR1916, which are over 13 billion light years from Earth.

Both popular and professional research articles in cosmology often use the term "universe" when they really mean "observable universe". This is because unobservable physical phenomena are scientifically irrelevant; that is, they cannot affect any events that we can perceive. See also Causality (physics).

Shape of the universe
Main articles: Shape of the universe, and Large-scale structure of the cosmos
An important open question of cosmology is the shape of the universe. Mathematically, which 3-manifold represents best the spatial part of the universe?

Firstly, whether the universe is spatially flat, i.e. whether the rules of Euclidean geometry are valid on the largest scales, is unknown. Currently, most cosmologists believe that the observable universe is very nearly spatially flat, with local wrinkles where massive objects distort spacetime, just as a lake is (nearly) flat. This opinion was strengthened by the latest data from WMAP, looking at "acoustic oscillations" in the cosmic microwave background radiation temperature variations.

Secondly, whether the universe is multiply connected, is unknown. The universe has no spatial boundary according to the standard Big Bang model, but nevertheless may be spatially finite (compact). This can be understood using a two-dimensional analogy: the surface of a sphere has no edge, but nonetheless has a finite area. It is a two-dimensional surface with constant curvature in a third dimension. The 3-sphere is a three-dimensional equivalent in which all three dimensions are constantly curved in a fourth.

If the universe is indeed spatially finite, as described, then traveling in a "straight" line, in any given direction, would theoretically cause one to eventually arrive back at the starting point.

Strictly speaking, we should call the stars and galaxies "views" of stars and galaxies, since it is possible that the universe is multiply-connected and sufficiently small (and of an appropriate, perhaps complex, shape) that we can see once or several times around it in various, and perhaps all, directions. (Think of a house of mirrors.) If so, the actual number of physically distinct stars and galaxies would be smaller than currently accounted. Although this possibility has not been ruled out, the results of the latest cosmic microwave background research make this appear very unlikely.

Fate of the universe
Depending on the average density of matter and energy in the universe, it will either keep on expanding forever or it will be gravitationally slowed down and will eventually collapse back on itself in a "Big Crunch". Currently the evidence suggests not only that there is insufficient mass/energy to cause a recollapse, but that the expansion of the universe seems to be accelerating and will accelerate for eternity (see accelerating universe). Other ideas of the fate of our universe include the Big Rip, the Big Freeze, and Heat death of the universe theory. For a more detailed discussion of other theories, see the ultimate fate of the universe.

Multiverse
There is some speculation that multiple universes exist in a higher-level multiverse (also known as a megaverse), our universe being one of those universes. For example, matter that falls into a black hole in our universe could emerge as a Big Bang, starting another universe. However, all such ideas are currently untestable and cannot be regarded as anything more than speculation. The concept of parallel universes is understood only when related to string theory.

Other terms

Universum - C. Flammarion, Woodcut, Paris 1888Different words have been used throughout history to denote "all of space", including the equivalents and variants in various languages of "heavens," "cosmos," and "world." Macrocosm has also been used to this effect, although it is more specifically defined as a system that reflects in large scale one, some, or all of its component systems or parts. (Similarly, a microcosm is a system that reflects in small scale a much larger system of which it is a part.)

Although words like world and its equivalents in other languages now almost always refer to the planet Earth, they previously referred to everything that exists—see Copernicus, for example—and still sometimes do (as in "the whole wide world"). Some languages use the word for "world" as part of the word for "outer space", e.g. in the German word "Weltall".

Answer 2

Universe represents the whole. The term has mathematical significance especially in set theories.Usually since it represents the whole it is a finite entity.

Answer 3

It's infinite size of space with no end ,no direction in which billions or trillions of galaxies exist.And some of them are at a distance apart of millions or trillions of light years. And if we close our eue then a space can be a size of an atom. All illusions.