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The cosmological principle is consistent with the observed isotropy of: ( i ) the celestial distribution of radio galaxies, which are randomly distributed across the entire sky, ( ii ) the large scale spatial distribution of galaxies, which form a randomly tangled web of clusters and voids up to around 400 megaparsecs in width, ( iii ) the isotropic distribution of observed red shift in the spectra of distant galaxies, which implies a uniform expansion of space or Hubble flow in all directions, and ( iv ) the cosmic microwave background radiation, the relic radiation released by the expansion and cooling of the early universe, which is constant in all directions to within 1 part in 100, 000.
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cosmological and principle
The Big Bang theory depends on two major assumptions: the universality of physical laws and the cosmological principle.
The cosmological principle states that on large scales the Universe is homogeneous and isotropic.
If the large-scale Universe appears isotropic as viewed from Earth, the cosmological principle can be derived from the simpler Copernican principle, which states that there is no preferred ( or special ) observer or vantage point.
To this end, the cosmological principle has been confirmed to a level of 10 < sup >− 5 </ sup > via observations of the CMB.
The cosmological principle implies that the metric should be homogeneous and isotropic on large scales, which uniquely singles out the Friedmann – Lemaître – Robertson – Walker metric ( FLRW metric ).
It was later realized that Einstein's model was just one of a larger set of possibilities, all of which were consistent with general relativity and the cosmological principle.
Given the cosmological principle, Hubble's law suggested that the universe was expanding.
One is that there is no compelling reason, using current particle physics, to expect the universe to be flat, homogeneous and isotropic ( see the cosmological principle ).
Steven Weinberg and a number of string theorists ( see string landscape ) have used this as evidence for the anthropic principle, which suggests that the cosmological constant is so small because life ( and thus physicists, to make observations ) cannot exist in a universe with a large cosmological constant, but many people find this an unsatisfying explanation.
Inflation answers the classic conundrum of the Big Bang cosmology: why does the universe appear flat, homogeneous, and isotropic in accordance with the cosmological principle when one would expect, on the basis of the physics of the Big Bang, a highly curved, heterogeneous universe?
David Hume and later Paul Edwards have invoked a similar principle in their criticisms of the cosmological argument.
These two conditions comprise the cosmological principle.
Bondi and Thomas Gold used the Copernican principle to argue for the perfect cosmological principle which maintains that the universe is also homogeneous in time, and is the basis for the steady-state cosmology.
Measurements of the effects of the cosmic microwave background radiation in the dynamics of distant astrophysical systems in 2000 proved the Copernican principle on a cosmological scale.
This follows directly from the cosmological principle, wherein it is assumed our Hubble volume is not special or unique.
Moreover, the majority of cosmologists take the cosmological principle as a given, which assumes that matter at the scale of billions of light years is distributed isotropically.
The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle, which is supported by astronomical observations.
Since these are unknown in exact detail, cosmological models have been based on the cosmological principle, which states that the universe is homogeneous and isotropic.
However, assuming the cosmological principle that the universe is homogeneous and isotropic everywhere, every point in space is like every other point ; hence, the metric tensor must be the same everywhere.
It may seem that this conclusion is uncertain since it is based on the questionable assumptions of perfect homogeneity and isotropy ( the cosmological principle ) and that only the gravitational interaction is significant.
For example, Sir Arthur Stanley Eddington claimed that the cosmological constant version of the vacuum field equation expressed the " epistemological " property that the universe is " self-gauging ", and Erwin Schrödinger's pure-affine theory using a simple variational principle produced the field equation with a cosmological term.
cosmological and is
Anaxagoras is famous for introducing the cosmological concept of Nous ( mind ), as an ordering force.
I support the cosmological hypothesis which states that the development of the universe is repeated in its basic features an infinite number of times.
Thus there are alignments in all directions which would suggest there is little of astronomical significance, However, ethnohistorical records show that the various directions do have cosmological and astronomical significance with various points in the landscape being significant at different times of the year.
In one of two stanzas in the poem Grímnismál that mentions the bridge, Grímnir ( the god Odin in disguise ) provides the young Agnarr with cosmological knowledge, including that Bilröst is the best of bridges.
The Big Bang theory is the prevailing cosmological model that describes the early development of the Universe.
It is popularly reported that Hoyle, who favored an alternative " steady state " cosmological model, intended this to be pejorative, but Hoyle explicitly denied this and said it was just a striking image meant to highlight the difference between the two models.
Cosmologists therefore invoke a yet unexplored form of energy called dark energy ( dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe ) which account for certain cosmological observations mostly related to " accelerating expansion of Universe ".
The standard cosmological model is known as the ΛCDM model.
As a rule of thumb, a scattering or a decay process is cosmologically important in a certain cosmological epoch if the time scale describing that process is smaller or comparable to the time scale of the expansion of the universe, which is with being the Hubble constant at that time.
In the current cosmological epoch, the accelerated expansion due to dark energy is preventing structures larger than superclusters from forming.
In physical cosmology, cosmic inflation, cosmological inflation or just inflation is the theorized extremely rapid exponential expansion of the early universe by a factor of at least 10 < sup > 78 </ sup > in volume, driven by a negative-pressure vacuum energy density.
Objects beyond the cosmological horizon are moving away so fast that light ( or other electromagnetic radiation ) is unable to reach the observer.
In the Timaeus, Plato's major cosmological dialogue, the Platonic solid he associated with fire was the tetrahedron which is formed from four triangles and contains the least volume with the greatest surface area.
In the Timaeus, his major cosmological dialogue, the Platonic solid associated with air is the octahedron which is formed from eight equilateral triangles.
Water is one of the elements in ancient Greek philosophy, in the Asian Indian system Panchamahabhuta, and in the Chinese cosmological and physiological system Wu Xing.
In the Timaeus, his major cosmological dialogue, the Platonic solid associated with water is the icosahedron which is formed from twenty equilateral triangles.
cosmological and consistent
The general equations can be shown to be sufficiently consistent with classical tests of general relativity to be acceptable on physical principles, while still leaving considerable freedom to also provide interesting cosmological models.
Nevertheless, its cosmological predictions appear to be consistent with observations, so there is no compelling reason to adopt another theory.
However, soon after Einstein developed his static theory, observations by Edwin Hubble indicated that the universe appears to be expanding ; this was consistent with a cosmological solution to the original general-relativity equations that had been found by the mathematician Friedmann.
It requires the existence of a positive cosmological constant, and this is consistent with observed acceleration in the expansion of the Universe.
Other cosmological data are also consistent, and together tightly constrain the Model.
Unique to universes described by the FLRW metric, a de Sitter universe has a Hubble Law which is not only consistent through all space, but also through all time ( since the deceleration parameter is equal to ), thus satisfying the perfect cosmological principle that assumes isotropy and homogeneity throughout space and time.
In 2006, Steinhardt and Turok showed how the cyclic model could naturally incorporate a mechanism for relaxing the cosmological constant to very small values, consistent with current observations.
Einstein himself did not believe this result and so he added what he called a cosmological constant to his equations in an unsuccessful attempt to produce a theory consistent with a Steady State Universe.
The " Big Bang " scenario, with cosmic inflation and standard particle physics, is the only current cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe ( hydrogen, helium, and lithium ), and the spatial texture of minute irregularities ( anisotropies ) in the CMB radiation.
In cosmological problems, symmetry finds a role to play in the cosmological principle which restricts the type of universes that are consistent with large-scale observations ( e. g. the Friedmann-Lemaitre-Robertson-Walker ( FLRW ) metric ).
The distribution of these galaxies has since been found to be consistent with Cosmic Inflation, measurements of the Cosmic Microwave Background, and a nonzero cosmological constant, that is, with the existence of the now-accepted dark energy.
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