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A higher expansion rate would imply a smaller characteristic size of CMB fluctuations, and vice versa. The Planck collaboration measured the expansion rate this way and determined H 0 = 67.4 ± 0.5 (km/s)/Mpc. [26] There is a disagreement between this measurement and the supernova-based measurements, known as the Hubble tension.
The accelerated expansion of the universe is thought to have begun since the universe entered its dark-energy-dominated era roughly 5 billion years ago. [ 8 ] [ notes 1 ] Within the framework of general relativity , an accelerated expansion can be accounted for by a positive value of the cosmological constant Λ , equivalent to the presence of ...
The universe's expansion rate, a figure called the Hubble constant, is measured in kilometers per second per megaparsec, a distance equal to 3.26 million light-years.
Detailed measurements of the expansion rate of the universe place the Big Bang singularity at an estimated 13.787 ± 0.02 billion years ago, which is considered the age of the universe. [12] There remain aspects of the observed universe that are not yet adequately explained by the Big Bang models.
In using Hubble's law to determine distances, only the velocity due to the expansion of the universe can be used. Since gravitationally interacting galaxies move relative to each other independent of the expansion of the universe, [43] these relative velocities, called peculiar velocities, need to be accounted for in the application of Hubble's ...
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 ...
High-precision measurements of the expansion of the universe are required to understand how the expansion rate changes over time and space. In general relativity, the evolution of the expansion rate is estimated from the curvature of the universe and the cosmological equation of state (the relationship between temperature, pressure, and ...
The International Astronomical Union uses the term "age of the universe" to mean the duration of the Lambda-CDM expansion, [13] or equivalently, the time elapsed within the currently observable universe since the Big Bang. The expansion rate at any time is called the Hubble parameter ˙, which is modeled as ˙ = + + + (), where are density ...