Search results
Results from the WOW.Com Content Network
The expansion of the universe is the increase in distance between gravitationally unbound parts of the observable universe with time. [1] It is an intrinsic expansion, so it does not mean that the universe expands "into" anything or that space exists "outside" it.
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 earliest and most direct observational evidence of the validity of the theory are the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background and the relative abundances of light elements produced by Big Bang nucleosynthesis (BBN).
Infinite expansion does not constrain the overall spatial curvature of the universe.It can be open (with negative spatial curvature), flat, or closed (positive spatial curvature), although if it is closed, sufficient dark energy must be present to counteract the gravitational forces or else the universe will end in a Big Crunch.
The Big Crunch is a hypothetical scenario for the ultimate fate of the universe, in which the expansion of the universe eventually reverses and the universe recollapses, ultimately causing the cosmic scale factor to reach absolute zero, an event potentially followed by a reformation of the universe starting with another Big Bang. The vast ...
The thinning of matter over time reduces the ability of gravity to decelerate the expansion of the universe; in contrast, dark energy (believed to be a constant scalar field throughout the visible universe) is a constant factor tending to accelerate the expansion of the universe. The universe's expansion passed an inflection point about five or ...
In the Friedmann–Lemaître–Robertson–Walker metric, it can be shown that a strong constant negative pressure (i.e., tension) in all the universe causes an acceleration in the expansion if the universe is already expanding, or a deceleration in contraction if the universe is already contracting. This accelerating expansion effect is ...
The expansion of space summarized by the Big Bang interpretation of Hubble's law is relevant to the old conundrum known as Olbers' paradox: If the universe were infinite in size, static, and filled with a uniform distribution of stars, then every line of sight in the sky would end on a star, and the sky would be as bright as the surface of a ...