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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 Big Bang event 13-14 billion years ago initiated the universe, and it has been expanding ever since. Scientists in 1998 disclosed that this expansion was actually accelerating, with dark ...
That might mean there are unknown forces at work in the universe, for instance, or that there is a gap in our understanding of the cosmos that could require new physics.
Something is changing the expansion rate of the universe, scientists have said. For decades, researchers have been attempting to measure the “Hubble constant”, or the speed at which the cosmos ...
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 ...
If, however, the universe contains dark energy, then the resulting repulsive force may be sufficient to cause the expansion of the universe to continue forever—even if >. [10] This is the case in the currently accepted Lambda-CDM model , where dark energy is found through observations to account for roughly 68% of the total energy content of ...
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 physical universe is defined as all of space and time [a] (collectively referred to as spacetime) and their contents. [10] Such contents comprise all of energy in its various forms, including electromagnetic radiation and matter, and therefore planets, moons, stars, galaxies, and the contents of intergalactic space.