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  2. Outer space - Wikipedia

    en.wikipedia.org/wiki/Outer_space

    The temperature of outer space is measured in terms of the kinetic activity of the ... moon, and the company of stars float in the empty space, moving or standing still".

  3. Portal:Outer space - Wikipedia

    en.wikipedia.org/wiki/Portal:Outer_space

    The baseline temperature of outer space, as set by the background radiation from the Big Bang, is 2.7 kelvins (−270 °C; −455 °F). The plasma between galaxies is thought to account for about half of the baryonic (ordinary) matter in the universe, having a number density of less than one hydrogen atom per cubic metre and a kinetic ...

  4. Void (astronomy) - Wikipedia

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

    The first class consists of void finders that try to find empty regions of space based on local galaxy density. [28] The second class are those which try to find voids via the geometrical structures in the dark matter distribution as suggested by the galaxies. [29]

  5. Expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Expansion_of_the_universe

    The temperature of ultrarelativistic fluids, often called "radiation" and including the cosmic microwave background, scales inversely with the scale factor (i.e. ). The temperature of nonrelativistic matter drops more sharply, scaling as the inverse square of the scale factor (i.e. T ∝ a − 2 {\displaystyle T\propto a^{-2}} ).

  6. Empty space - Wikipedia

    en.wikipedia.org/wiki/Empty_space

    Outer space, especially the relatively empty regions of the universe outside the atmospheres of celestial bodies; Vacuum, a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure

  7. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    Using the upper limit of the cosmological constant, the vacuum energy of free space has been estimated to be 10 −9 joules (10 −2 ergs), or ~5 GeV per cubic meter. [3] However, in quantum electrodynamics , consistency with the principle of Lorentz covariance and with the magnitude of the Planck constant suggests a much larger value of 10 113 ...

  8. Interstellar medium - Wikipedia

    en.wikipedia.org/wiki/Interstellar_medium

    At lower temperatures, more levels than fine structure levels can be populated via collisions. For example, ... but in 'empty' space" (Birkeland 1913). ...

  9. Cosmological constant - Wikipedia

    en.wikipedia.org/wiki/Cosmological_constant

    When T μν is zero, the field equation describes empty space (a vacuum). The cosmological constant has the same effect as an intrinsic energy density of the vacuum, ρ vac (and an associated pressure). In this context, it is commonly moved to the right-hand side of the equation using Λ = κρ vac. It is common to quote values of energy ...