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-as of [20 SEPTEMBER 2024]–
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-in ‘physical cosmology’ + ‘astronomy’, dark energy is an unknown form of ‘energy’ which is hypothesized to permeate all of space, tending to ‘accelerate’ the ‘expansion’ of the ‘universe’-
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(“dark energy” is the most accepted hypothesis to explain the observations since the ‘1990s’ indicating that the universe is expanding at an accelerating rate)
(assuming that the “standard model of cosmology” is correct, the best current measurements indicate that “dark energy” contributes 68.3% of the total energy in the present-day ‘observable universe’)
*aka ‘concordance model of cosmology’*
The ΛCDM (Lambda cold dark matter) or Lambda-CDM model is a parametrization of the Big Bang cosmological model in which the universe contains three major components:
first, a cosmological constant denoted by Lambda (Greek Λ) and associated with dark energy;
second, the postulated cold dark matter (abbreviated CDM);
and third, ordinary matter.
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It is frequently referred to as the standard model of Big Bang cosmology because it is the simplest model that provides a reasonably good account of the following properties of the cosmos:
the existence and structure of the cosmic microwave background
the large-scale structure in the distribution of galaxies
the abundances of hydrogen (including deuterium), helium, and lithium
the accelerating expansion of the universe observed in the light from distant galaxies and supernovae
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The model assumes that general relativity is the correct theory of gravity on cosmological scales.
It emerged in the late 1990s as a concordance cosmology, after a period of time when disparate observed properties of the universe appeared mutually inconsistent, and there was no consensus on the makeup of the energy density of the universe.
The ΛCDM model can be extended by adding cosmological inflation, quintessence and other elements that are current areas of speculation and research in cosmology.
Some alternative models challenge the assumptions of the ΛCDM model.
Examples of these are
modified Newtonian dynamics,
entropic gravity,
modified gravity,
theories of large-scale variations in the matter density of the universe,
bimetric gravity,
scale invariance of empty space,
and decaying dark matter (DDM).
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(the ‘mass–energy’ of ‘dark matter’ / ‘ordinary (aka ‘baryonic’) matter” contribute (26.8% / 4.9%))
(other components (such as ‘neutrinos’ + ‘photons’) contribute a very small amount)
(again, on a ‘mass–energy equivalence basis’, the density of ‘dark energy’ (~ 7 × 10−30 g/cm3) is very low, much less than the ‘density’ of ‘ordinary matter’ or ‘dark matter’ within ‘galaxies’)
(however, it comes to dominate the ‘mass–energy’ of the ‘universe’ because it is uniform across space)
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(2 proposed forms for ‘dark energy’ are…)
#1
*the ‘cosmological constant’*
(a ‘constant energy density’ filling space homogeneously)
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#2
*scalar fields*
(such as ‘quintessence’ or ‘moduli’)
(‘dynamic quantities’ whose ‘energy density’ can vary in ‘time’ + ‘space’)
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(contributions from ‘scalar fields’ that are ‘constant’ in ‘space’ are usually also included in the ‘cosmological constant’)
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(the ‘cosmological constant’ can be formulated to be equivalent to the ‘zero-point radiation’ of ‘space’)
(aka –> the ‘vacuum energy’)
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(“scalar fields” that do change in ‘space’ can be difficult to distinguish from a ‘cosmological constant’ because the change may be extremely slow)
(‘high-precision measurements’ of the ‘expansion’ of the ‘universe’ are required to understand how the ‘expansion rate’ changes over ‘time’ + ‘space’)
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(in ‘general relativity’, the ‘evolution’ of the ‘expansion rate’ is ‘parameterized’ by the ‘cosmological equation’ of ‘state’)
(in other words…)
*the relationship between…*
‘temperature’ / ‘pressure’
AND
‘combined matter’ / ‘energy’ / ‘vacuum energy density’
(…for any region of ‘space’)
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(measuring the ‘equation of state’ for “dark energy” is one of the biggest efforts in ‘observational cosmology’ today)
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(adding the ‘cosmological constant’ to cosmology’s ‘standard FLRW metric’ leads to the ‘lambda-CDM model’, which has been referred to as the “standard model of cosmology” because of its precise agreement with observations)
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(“dark energy” has been used as a crucial ingredient in a recent attempt to formulate a “cyclic model” for the universe)
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*👨🔬🕵️♀️🙇♀️*SKETCHES*🙇♂️👩🔬🕵️♂️*
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💕💝💖💓🖤💙🖤💙🖤💙🖤❤️💚💛🧡❣️💞💔💘❣️🧡💛💚❤️🖤💜🖤💙🖤💙🖤💗💖💝💘
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*🌈✨ *TABLE OF CONTENTS* ✨🌷*
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🔥🔥🔥🔥🔥🔥*we won the war* 🔥🔥🔥🔥🔥🔥