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  2. Flatness problem - Wikipedia

    en.wikipedia.org/wiki/Flatness_problem

    The flatness problem (also known as the oldness problem) is a cosmological fine-tuning problem within the Big Bang model of the universe. Such problems arise from the observation that some of the initial conditions of the universe appear to be fine-tuned to very 'special' values, and that small deviations from these values would have extreme ...

  3. Big Bang - Wikipedia

    en.wikipedia.org/wiki/Big_Bang

    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.

  4. Horizon problem - Wikipedia

    en.wikipedia.org/wiki/Horizon_problem

    The horizon problem (also known as the homogeneity problem) is a cosmological fine-tuning problem within the Big Bang model of the universe. It arises due to the difficulty in explaining the observed homogeneity of causally disconnected regions of space in the absence of a mechanism that sets the same initial conditions everywhere.

  5. Conformal cyclic cosmology - Wikipedia

    en.wikipedia.org/wiki/Conformal_cyclic_cosmology

    Conformal cyclic cosmology (CCC) is a cosmological model in the framework of general relativity and proposed by theoretical physicist Roger Penrose. [1] [2] [3] In CCC, the universe iterates through infinite cycles, with the future timelike infinity (i.e. the latest end of any possible timescale evaluated for any point in space) of each previous iteration being identified with the Big Bang ...

  6. Initial singularity - Wikipedia

    en.wikipedia.org/wiki/Initial_singularity

    The traditional model of the Big Bang. The use of only general relativity to predict what happened in the beginnings of the universe has been heavily criticized, as quantum mechanics becomes a significant factor in the high-energy environment of the earliest stage of the universe, and general relativity on its own fails to make accurate predictions.

  7. Cosmic inflation - Wikipedia

    en.wikipedia.org/wiki/Cosmic_inflation

    The big bounce hypothesis attempts to replace the cosmic singularity with a cosmic contraction and bounce, thereby explaining the initial conditions that led to the big bang. The flatness and horizon problems are naturally solved in the Einstein–Cartan–Sciama–Kibble theory of gravity, without needing an exotic form of matter or free ...

  8. Cosmological lithium problem - Wikipedia

    en.wikipedia.org/wiki/Cosmological_lithium_problem

    Big Bang nucleosynthesis produced both lithium-7 and beryllium-7, and indeed the latter dominates the primordial synthesis of mass 7 nuclides. On the other hand, the Big Bang produced lithium-6 at levels more than 1000 times smaller. 7 4 Be later decayed via electron capture (half-life 53.22 days) into 7 3 Li

  9. History of the Big Bang theory - Wikipedia

    en.wikipedia.org/wiki/History_of_the_Big_Bang_theory

    The history of the Big Bang theory began with the Big Bang's development from observations and theoretical considerations. Much of the theoretical work in cosmology now involves extensions and refinements to the basic Big Bang model. The theory itself was originally formalised by Father Georges Lemaître in 1927. [1]