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  2. Chronology of the universe - Wikipedia

    en.wikipedia.org/wiki/Chronology_of_the_universe

    The chronology of the universe describes the history and future of the universe according to Big Bang cosmology.. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level.

  3. Age of the universe - Wikipedia

    en.wikipedia.org/wiki/Age_of_the_universe

    In physical cosmology, the age of the universe is the time elapsed since the Big Bang: 13.8 billion years. [1] Astronomers have two different approaches to determine the age of the universe . One is based on a particle physics model of the early universe called Lambda-CDM , matched to measurements of the distant, and thus old features, like the ...

  4. The Five Ages of the Universe - Wikipedia

    en.wikipedia.org/wiki/The_Five_Ages_of_the_Universe

    The Primordial Era is defined as "−50 < n < 5". In this era, the Big Bang, the subsequent inflation, and Big Bang nucleosynthesis are thought to have taken place. Toward the end of this age, the recombination of electrons with nuclei made the universe transparent for the first time. The authors discuss the horizon and flatness problems.

  5. 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 .

  6. Reionization - Wikipedia

    en.wikipedia.org/wiki/Reionization

    In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages". Detecting and studying the reionization process is challenging but multiple avenues have been pursued.

  7. Cosmic age problem - Wikipedia

    en.wikipedia.org/wiki/Cosmic_age_problem

    The possible discrepancy between the ages of the Earth and the universe was probably one motivation for the development of the Steady State theory in 1948 as an alternative to the Big Bang; [5] in the (now obsolete) steady state theory, the universe is infinitely old and on average unchanging with time.

  8. Cosmic microwave background - Wikipedia

    en.wikipedia.org/wiki/Cosmic_microwave_background

    The CMB is landmark evidence of the Big Bang theory for the origin of the universe. In the Big Bang cosmological models, during the earliest periods, the universe was filled with an opaque fog of dense, hot plasma of sub-atomic particles. As the universe expanded, this plasma cooled to the point where protons and electrons combined to form ...

  9. Lambda-CDM model - Wikipedia

    en.wikipedia.org/wiki/Lambda-CDM_model

    The "Big Bang" scenario, with cosmic inflation and standard particle physics, is the only cosmological model consistent with the observed continuing expansion of space, the observed distribution of lighter elements in the universe (hydrogen, helium, and lithium), and the spatial texture of minute irregularities (anisotropies) in the CMB radiation.