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  2. Rare Earth hypothesis - Wikipedia

    en.wikipedia.org/wiki/Rare_Earth_hypothesis

    The Rare Earth hypothesis argues that planets with complex life, like Earth, are exceptionally rare.. In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity, such as sexually reproducing, multicellular organisms on Earth, and subsequently human intelligence, required an improbable combination of astrophysical ...

  3. Cosmogony - Wikipedia

    en.wikipedia.org/wiki/Cosmogony

    The Big Bang theory, which explains the Evolution of the Universe from a hot and dense state, is widely accepted by physicists.. In astronomy, cosmogony is the study of the origin of particular astrophysical objects or systems, and is most commonly used in reference to the origin of the universe, the Solar System, or the Earth–Moon system.

  4. Big Bounce - Wikipedia

    en.wikipedia.org/wiki/Big_Bounce

    The Big Bounce hypothesis is a cosmological model for the origin of the known universe. It was originally suggested as a phase of the cyclic model or oscillatory universe interpretation of the Big Bang , where the first cosmological event was the result of the collapse of a previous universe.

  5. Galaxy formation and evolution - Wikipedia

    en.wikipedia.org/wiki/Galaxy_formation_and_evolution

    In cosmology, the study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies.

  6. 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.

  7. Cosmology - Wikipedia

    en.wikipedia.org/wiki/Cosmology

    The universe is generally understood to have begun with the Big Bang, followed almost instantaneously by cosmic inflation, an expansion of space from which the universe is thought to have emerged 13.799 ± 0.021 billion years ago. [8] Cosmogony studies the origin of the universe, and cosmography maps the features of the universe.

  8. Fermi paradox - Wikipedia

    en.wikipedia.org/wiki/Fermi_paradox

    This is an accepted version of this page This is the latest accepted revision, reviewed on 20 January 2025. Problem of the lack of evidence for alien life despite its apparent likelihood This article is about the absence of clear evidence of extraterrestrial life. For a type of estimation problem, see Fermi problem. Enrico Fermi (Los Alamos 1945) The Fermi paradox is the discrepancy between ...

  9. Nebular hypothesis - Wikipedia

    en.wikipedia.org/wiki/Nebular_hypothesis

    The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe.