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  2. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    According to the theory of cosmic inflation initially introduced by Alan Guth and D. Kazanas, [23] if it is assumed that inflation began about 10 −37 seconds after the Big Bang and that the pre-inflation size of the universe was approximately equal to the speed of light times its age, that would suggest that at present the entire universe's ...

  3. Universe - Wikipedia

    en.wikipedia.org/wiki/Universe

    Because humans cannot observe space beyond the edge of the observable universe, it is unknown whether the size of the universe in its totality is finite or infinite. [3] [57] [58] Estimates suggest that the whole universe, if finite, must be more than 250 times larger than a Hubble sphere. [59]

  4. Shape of the universe - Wikipedia

    en.wikipedia.org/wiki/Shape_of_the_universe

    If the true value of the cosmological curvature parameter is larger than 10 −3 we will be able to distinguish ... (Pi and the size of the Universe)". Numberphile ...

  5. Big Bang - Wikipedia

    en.wikipedia.org/wiki/Big_Bang

    For distances comparable to the size of the observable universe, the attribution of the cosmological redshift becomes more ambiguous, although its interpretation as a kinematic Doppler shift remains the most natural one. [96] An unexplained discrepancy with the determination of the Hubble constant is known as Hubble tension. Techniques based on ...

  6. Expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Expansion_of_the_universe

    The history of the universe after inflation but before a time of about 1 second is largely unknown. [20] However, the universe is known to have been dominated by ultrarelativistic Standard Model particles, conventionally called radiation, by the time of neutrino decoupling at about 1 second. [21]

  7. Ultimate fate of the universe - Wikipedia

    en.wikipedia.org/wiki/Ultimate_fate_of_the_universe

    If the theory of inflation is true, the universe went through an episode dominated by a different form of dark energy in the first moments of the Big Bang, but inflation ended, indicating an equation of state more complex than those assumed for present-day dark energy. It is possible that the dark energy equation of state could change again ...

  8. Outer space - Wikipedia

    en.wikipedia.org/wiki/Outer_space

    Neither time nor size are to scale. The size of the whole universe is unknown, and it might be infinite in extent. [20] According to the Big Bang theory, the very early universe was an extremely hot and dense state about 13.8 billion years ago [21] which rapidly expanded.

  9. Great Debate (astronomy) - Wikipedia

    en.wikipedia.org/wiki/Great_Debate_(astronomy)

    Later in the 1920s, Edwin Hubble showed that Andromeda was far outside the Milky Way by measuring Cepheid variable stars, proving that Curtis was correct. [6] It is now known that the Milky Way is only one of as many as an estimated 200 billion (2 × 10 11) [7] to 2 trillion (2 × 10 12) or more galaxies in the observable Universe.