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Adam Riess et al. found that "the distances of the high-redshift SNe Ia were, on average, 10% to 15% further than expected in a low mass density Ω M = 0.2 universe without a cosmological constant". [14] This means that the measured high-redshift distances were too large, compared to nearby ones, for a decelerating universe. [15]
Contrary to common misconception, it is equally valid to adopt a description in which space does not expand and objects simply move apart while under the influence of their mutual gravity. [2] [3] [4] Although cosmic expansion is often framed as a consequence of general relativity, it is also predicted by Newtonian gravity. [5] [6]
A space with a cosmological constant is qualitatively different: instead of moving outward, the cosmological horizon stays put. For any one observer, the distance to the cosmological horizon is constant. With exponentially expanding space, two nearby observers are separated very quickly; so much so, that the distance between them quickly ...
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.
Instead, astronomical observations show that the expansion of the universe is accelerating rather than being slowed by gravity, suggesting that a Big Freeze is much more likely to occur. [ 1 ] [ 2 ] [ 3 ] Nonetheless, some physicists have proposed that a "Big Crunch-style" event could result from a dark energy fluctuation.
These three possibilities correspond to parameter k of (0) flat space, (+1) a sphere of constant positive curvature or (-1) a hyperbolic space with constant negative curvature. Here the radial position has been decomposed into a time-dependent scale factor, R ( t ) {\displaystyle R(t)} , and a comoving coordinate, r {\displaystyle r} .
General relativity predicts that energy is equivalent to mass, and therefore, if the vacuum energy is "really there", it should exert a gravitational force. Essentially, a non-zero vacuum energy is expected to contribute to the cosmological constant, which affects the expansion of the universe.
The local geometry of the universe is determined by whether the relative density Ω is less than, equal to or greater than 1. From top to bottom: a spherical universe with greater than critical density (Ω>1, k>0); a hyperbolic, underdense universe (Ω<1, k<0); and a flat universe with exactly the critical density (Ω=1, k=0). The spacetime of ...