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[13] [14] [15] Combining Slipher's velocities with Henrietta Swan Leavitt's intergalactic distance calculations and methodology allowed Hubble to better calculate an expansion rate for the universe. [16] Hubble's law is considered the first observational basis for the expansion of the universe, and is one of the pieces of evidence most often ...
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. [30] There is a disagreement between this measurement and the supernova-based measurements, known as the Hubble tension.
These gravitational waves can work as sort of standard sirens to measure the expansion rate of the universe. Abbot et al. 2017 measured the Hubble constant value to be approximately 70 kilometres per second per megaparsec. [22]
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.
The 100-inch (2.5 m) Hooker telescope at Mount Wilson Observatory that Hubble used to measure galaxy distances and a value for the rate of expansion of the universe. Edwin Hubble's arrival at Mount Wilson Observatory, California, in 1919 coincided roughly with the completion of the 100-inch (2.5 m) Hooker Telescope , then the world's largest.
The Big Bang is a physical theory that describes how the universe expanded from an initial state of high density and temperature. [1] The concept of an expanding universe was scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations.
The expansion of the universe is parameterized by a dimensionless scale factor = (with time counted from the birth of the universe), defined relative to the present time, so = =; the usual convention in cosmology is that subscript 0 denotes present-day values, so denotes the age of the universe.
Evaluating the Hubble parameter at the present time yields Hubble's constant which is the proportionality constant of Hubble's law. Applied to a fluid with a given equation of state , the Friedmann equations yield the time evolution and geometry of the universe as a function of the fluid density.