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The other model was Fred Hoyle's steady-state model, in which new matter would be created as the galaxies moved away from each other. In this model, the universe is roughly the same at any point in time.
A flat universe implies a balance between gravitational potential energy and other energy forms, requiring no additional energy to be created. [ 138 ] [ 139 ] The Big Bang theory, built upon the equations of classical general relativity, indicates a singularity at the origin of cosmic time, and such an infinite energy density may be a physical ...
The traditional model of the Big Bang. The use of only general relativity to predict what happened in the beginnings of the universe has been heavily criticized, as quantum mechanics becomes a significant factor in the high-energy environment of the earliest stage of the universe, and general relativity on its own fails to make accurate predictions.
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).
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 [7] 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 ...
Dark energy dominates the total energy (74%) while dark matter (22%) constitutes most of the mass. Of the remaining baryonic matter (4%), only one tenth is compact. In February 2015, the European-led research team behind the Planck cosmology probe released new data refining these values to 4.9% ordinary matter, 25.9% dark matter and 69.1% dark ...
Thus, the Lambda-CDM model, the current standard model of cosmology which uses the FLRW metric, includes the cosmological constant, which is measured to be on the order of 10 −52 m −2. It may be expressed as 10 −35 s −2 (multiplying by c 2 ≈ 10 17 m 2 ⋅s −2 ) or as 10 −122 ℓ P −2 [ 29 ] (where ℓ P is the Planck length).
Refined models agree very well with observations with the exception of the abundance of 7 Li. The model is one of the key concepts in standard cosmology. Elements heavier than lithium are thought to have been created later in the life of the Universe by stellar nucleosynthesis, through the formation, evolution and death of stars.