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The measurement of the speed of gravity with the gravitational wave event GW170817 ruled out many modified gravity theories as alternative explanations to dark energy. [ 35 ] [ 36 ] [ 37 ] Another type of model, the backreaction conjecture, [ 38 ] [ 39 ] was proposed by cosmologist Syksy Räsänen: [ 40 ] the rate of expansion is not homogenous ...
The density of dark matter in an expanding universe decreases more quickly than dark energy, and eventually the dark energy dominates. Specifically, when the volume of the universe doubles, the density of dark matter is halved, but the density of dark energy is nearly unchanged (it is exactly constant in the case of a cosmological constant).
[66] [150] There are very many theories in this category, for example, replacing general relativity with a modified theory of gravity could potentially resolve the tension, [151] [152] as can a dark energy component in the early universe, [b] [153] dark energy with a time-varying equation of state, [c] [154] or dark matter that decays into dark ...
To make that assumption work, astronomers have used the concept of dark energy. Dark energy doesn’t actually exist, scientists say in shock claim that could solve one of the universe’s biggest ...
The researchers used a year of observations by the Dark Energy Spectroscopic Instrument (DESI) at Kitt Peak National Observatory in Arizona, which can capture light from 5,000 galaxies simultaneously.
In the context of this article, "faster-than-light" means the transmission of information or matter faster than c, a constant equal to the speed of light in vacuum, which is 299,792,458 m/s (by definition of the metre) [3] or about 186,282.397 miles per second.
In particular, general relativity predicts that light will move at the speed c with respect to the local motion of the exploding matter, a phenomenon analogous to frame dragging. The situation changes somewhat with the introduction of dark energy or a cosmological constant.
Since the 1990s, studies have shown that, assuming the cosmological principle, around 68% of the mass–energy density of the universe can be attributed to dark energy. [6] [7] [8] The cosmological constant Λ is the simplest possible explanation for dark energy, and is used in the standard model of cosmology known as the ΛCDM model.