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  2. 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 notion of an expanding universe was first scientifically originated by physicist Alexander Friedmann in 1922 with the mathematical derivation of the Friedmann equations. [2][3][4][5]

  3. 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. [1]

  4. Timeline of the early universe - Wikipedia

    en.wikipedia.org/wiki/Timeline_of_the_early_universe

    The timeline of the early universe outlines the formation and subsequent evolution of the Universe from the Big Bang (13.799 ± 0.021 billion years ago) [1] to the present day. An epoch is a moment in time from which nature or situations change to such a degree that it marks the beginning of a new era or age. Times on this list are measured ...

  5. Graphical timeline of the Big Bang - Wikipedia

    en.wikipedia.org/wiki/Graphical_timeline_of_the...

    e. This timeline of the Big Bang shows a sequence of events as currently theorized by scientists. It is a logarithmic scale that shows second instead of second. For example, one microsecond is . To convert −30 read on the scale to second calculate second = one millisecond. On a logarithmic time scale a step lasts ten times longer than the ...

  6. 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.

  7. 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]

  8. Universe - Wikipedia

    en.wikipedia.org/wiki/Universe

    This process, known as Big Bang nucleosynthesis, lasted for about 17 minutes and ended about 20 minutes after the Big Bang, so only the fastest and simplest reactions occurred. About 25% of the protons and all the neutrons in the universe, by mass, were converted to helium , with small amounts of deuterium (a form of hydrogen ) and traces of ...

  9. 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 ...