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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. [30] 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 ...
1998 – The first complete Einstein ring, B1938+666, discovered using the Hubble Space Telescope and MERLIN. [227] [228] 1998-99 – Scientists discover that the expansion of the Universe is accelerating. [229] [230] 1999 – Alessandra Buonanno and Thibault Damour introduce the effective one-body formalism. [231]
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 thinning of matter over time reduces the ability of the matter to gravitationally decelerate the expansion of the universe; in contrast, dark energy is a constant factor tending to accelerate the expansion of the universe. The universe's expansion passed an inflection point about five or six billion years ago when the universe entered the ...
Timeline of the expansion of the universe, where space, including hypothetical non-observable portions of the universe, is represented at each time by the circular sections. On the left, the dramatic expansion occurs in the inflationary epoch ; and at the center, the expansion accelerates (artist's concept; neither time nor size are to scale).
[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 ...
Experimental observations confirm expansion of universe according to Hubble's law. Since the universe is expanding, the equation for that expansion can be "run backwards" to its starting point. The Lambda-CDM concordance model describes the expansion of the universe from a very uniform, hot, dense primordial state to its present state over a ...