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Amazing Pictures Of The Universe Definition

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The Universe is commonly defined as the totality of existence,[1][2][3][4] including planets, stars, galaxies, the contents of intergalactic space, and all matter and energy.[5][6] The broadest definition of universe is that it is simply everything, while a narrower definition is that the universe is limited to what can be observed.[dubious – discuss] Similar terms include the cosmos, the world and nature.

Scientific observation of the Universe, the observable part of which is about 93 billion light years in diameter,[7] has led to inferences of its earlier stages. These observations suggest that the Universe has been governed by the same physical laws and constants throughout most of its extent and history. The Big Bang theory is the prevailing cosmological model that describes the early development of the Universe, which in physical cosmology is calculated to have occurred 13.798 ± 0.037 billion years ago.[8][9]

There are various multiverse hypotheses, in which physicists have suggested that the Universe might be one among many universes that likewise exist.[10][11] The farthest distance that it is theoretically possible for humans to see is described as the observable Universe. Observations have shown that the Universe appears to be expanding at an accelerating rate.

Physicists remain unsure about what, if anything, preceded the Big Bang. There are many competing theories about the ultimate fate of the Universe.
History of the Universe
According to the prevailing scientific model of the Universe, known as the Big Bang, the Universe expanded from an extremely hot, dense phase called the Planck epoch, in which all the matter and energy of the observable universe was concentrated. Since the Planck epoch, the Universe has been expanding to its present form, possibly with a brief period (less than 10−32 seconds) of cosmic inflation. Several independent experimental measurements support this theoretical expansion and, more generally, the Big Bang theory. Recent observations indicate that this expansion is accelerating because of dark energy, and that most of the matter in the Universe may be in a form which cannot be detected by present instruments, called dark matter.[14] The common use of the "dark matter" and "dark energy" placeholder names for the unknown entities purported to account for about 95% of the mass-energy density of the Universe demonstrates the present observational and conceptual shortcomings and uncertainties concerning the nature and ultimate fate of the Universe.[15]

On 21 March 2013, the European-led research team behind the Planck cosmology probe released the mission's all-sky map of the cosmic microwave background.[16][17][18][19][20] The map suggests the universe is slightly older than thought. According to the map, subtle fluctuations in temperature were imprinted on the deep sky when the cosmos was about 370,000 years old. The imprint reflects ripples that arose as early, in the existence of the universe, as the first nonillionth of a second. Apparently, these ripples gave rise to the present vast cosmic web of galaxy clusters and dark matter. According to the team, the universe is 13.798 ± 0.037 billion years old,[21][9] and contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. Also, the Hubble constant was measured to be 67.80 ± 0.77 (km/s)/Mpc.[21][16][17][18][20]

An earlier interpretation of astronomical observations indicated that the age of the Universe was 13.772 ± 0.059 billion years,[22] (whereas the decoupling of light and matter, see CMBR, happened already 380,000 years after the Big Bang), and that the diameter of the observable universe is at least 93 billion light years or 8.80×1026 meters.[23] According to general relativity, space can expand faster than the speed of light, although we can view only a small portion of the Universe due to the limitation imposed by light speed. Since we cannot observe space beyond the limitations of light (or any electromagnetic radiation), it is uncertain whether the size of the Universe is finite or infinite.