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In standard cosmology, there are three components of the universe: matter, radiation, and dark energy. This matter is anything whose energy density scales with the inverse cube of the scale factor, i.e., ρ ∝ a −3, while radiation is anything whose energy density scales to the inverse fourth power of the scale factor (ρ ∝ a −4).
In physical cosmology, the dark-energy-dominated era is proposed as the last of the three phases of the known universe, the other two being the radiation-dominated era and the matter-dominated era. The dark-energy-dominated era began after the matter-dominated era, i.e. when the Universe was about 9.8 billion years old. [ 13 ]
The measured dark energy density is Ω Λ ≈ 0.690; the observed ordinary (baryonic) matter energy density is Ω b ≈ 0.0482 and the energy density of radiation is negligible. This leaves a missing Ω dm ≈ 0.258 which nonetheless behaves like matter (see technical definition section above) – dark matter.
The universe's contents include ordinary matter - stars, planets, gas, dust and all the familiar stuff on Earth, including people and popcorn - as well as dark matter, which is invisible material ...
In cosmology, the cosmic coincidence is the observation that at the present epoch of the universe's evolution, the energy densities associated with dark matter and dark energy are of the same order of magnitude, leading to their comparable effects on the dynamics of the cosmos. [1]
Dark matter is the biggest mystery of the cosmos. Scientists know that it has been vital to the universe since its beginning, and new discoveries reveal that it could create black holes , cause mass extinctions , and might even have helped to shape life on Earth.
The model assumes that standard matter provides a pressure which counterbalances the action due to the cosmological constant. Luongo and Muccino have shown that this mechanism permits to take vacuum energy as quantum field theory predicts, but removing the huge magnitude through a counterbalance term due to baryons and cold dark matter only. [25]
The fraction of the total energy density of our (flat or almost flat) universe that is dark energy, , is estimated to be 0.669 ± 0.038 based on the 2018 Dark Energy Survey results using Type Ia supernovae [8] or 0.6847 ± 0.0073 based on the 2018 release of Planck satellite data, or more than 68.3 % (2018 estimate) of the mass–energy density ...