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  2. Universe - Wikipedia

    en.wikipedia.org/wiki/Universe

    This metric has only two undetermined parameters. An overall dimensionless length scale factor R describes the size scale of the universe as a function of time (an increase in R is the expansion of the universe), [152] and a curvature index k describes the geometry.

  3. Dirac large numbers hypothesis - Wikipedia

    en.wikipedia.org/wiki/Dirac_large_numbers_hypothesis

    The Dirac large numbers hypothesis (LNH) is an observation made by Paul Dirac in 1937 relating ratios of size scales in the Universe to that of force scales. The ratios constitute very large, dimensionless numbers: some 40 orders of magnitude in the present cosmological epoch.

  4. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...

  5. Physical cosmology - Wikipedia

    en.wikipedia.org/wiki/Physical_cosmology

    Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. [1]

  6. Big Bounce - Wikipedia

    en.wikipedia.org/wiki/Big_Bounce

    The theory explains that the universe will expand until all matter decays and ultimately turns to light. Since nothing in the universe would have any time or distance scale associated with it, the universe becomes identical with the Big Bang, resulting in a type of Big Crunch that becomes the next Big Bang, thus perpetuating the next cycle. [21]

  7. Cosmological principle - Wikipedia

    en.wikipedia.org/wiki/Cosmological_principle

    In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course ...

  8. Observational cosmology - Wikipedia

    en.wikipedia.org/wiki/Observational_cosmology

    This theory of rapid spatial expansion gave an explanation for large-scale isotropy by allowing causal connection just before the epoch of last scattering. [ 33 ] : 8.5.4 With this and similar theories, detailed prediction encouraged larger and more ambitious experiments.

  9. Shape of the universe - Wikipedia

    en.wikipedia.org/wiki/Shape_of_the_universe

    An infinite universe (unbounded metric space) means that there are points arbitrarily far apart: for any distance d, there are points that are of a distance at least d apart. A finite universe is a bounded metric space, where there is some distance d such that all points are within distance d of each other.