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  2. Expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Expansion_of_the_universe

    Because of the high rate of expansion, it is also possible for a distance between two objects to be greater than the value calculated by multiplying the speed of light by the age of the universe. These details are a frequent source of confusion among amateurs and even professional physicists. [33]

  3. Accelerating expansion of the universe - Wikipedia

    en.wikipedia.org/wiki/Accelerating_expansion_of...

    The accelerated expansion of the universe is thought to have begun since the universe entered its dark-energy-dominated era roughly 5 billion years ago. [ 8 ] [ notes 1 ] Within the framework of general relativity , an accelerated expansion can be accounted for by a positive value of the cosmological constant Λ , equivalent to the presence of ...

  4. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    It represents the boundary between the observable and the unobservable regions of the universe, so its distance at the present epoch defines the size of the observable universe. Due to the expansion of the universe, it is not simply the age of the universe times the speed of light, as in the Hubble horizon, but rather the speed of light ...

  5. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    The Friedmann equations showed the universe might be expanding, and presented the expansion speed if that were the case. [5] Before Hubble, astronomer Carl Wilhelm Wirtz had, in 1922 [ 6 ] and 1924, [ 7 ] deduced with his own data that galaxies that appeared smaller and dimmer had larger redshifts and thus that more distant galaxies recede ...

  6. Cosmic inflation - Wikipedia

    en.wikipedia.org/wiki/Cosmic_inflation

    As the very early universe cooled it was trapped in a metastable state (it was supercooled), which it could only decay out of through the process of bubble nucleation via quantum tunneling. Bubbles of true vacuum spontaneously form in the sea of false vacuum and rapidly begin expanding at the speed of light. Guth recognized that this model was ...

  7. Particle horizon - Wikipedia

    en.wikipedia.org/wiki/Particle_horizon

    Much like the concept of a terrestrial horizon, it represents the boundary between the observable and the unobservable regions of the universe, [1] so its distance at the present epoch defines the size of the observable universe. [2] Due to the expansion of the universe, it is not simply the age of the universe times the speed of light ...

  8. Comoving and proper distances - Wikipedia

    en.wikipedia.org/wiki/Comoving_and_proper_distances

    How best to describe and popularize that expansion of the universe is (or at least was) very likely proceeding – at the greatest scale – at above the speed of light, has caused a minor amount of controversy. One viewpoint is presented in Davis and Lineweaver, 2004. [2]

  9. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    The expansion of the universe is understood to exceed the speed of light beyond a certain boundary. The speed at which light propagates through transparent materials , such as glass or air, is less than c ; similarly, the speed of electromagnetic waves in wire cables is slower than c .