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  2. Hubble volume - Wikipedia

    en.wikipedia.org/wiki/Hubble_volume

    In cosmology, a Hubble volume (named for the astronomer Edwin Hubble) or Hubble sphere, Hubble bubble, subluminal sphere, causal sphere and sphere of causality is a spherical region of the observable universe surrounding an observer beyond which objects recede from that observer at a rate greater than the speed of light due to the expansion of ...

  3. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    Assuming the mass of ordinary matter is about 1.45 × 10 53 kg as discussed above, and assuming all atoms are hydrogen atoms (which are about 74% of all atoms in the Milky Way by mass), the estimated total number of atoms in the observable universe is obtained by dividing the mass of ordinary matter by the mass of a hydrogen atom.

  4. Cosmological horizon - Wikipedia

    en.wikipedia.org/wiki/Cosmological_horizon

    Hubble radius, Hubble sphere (not to be confused with a Hubble bubble), Hubble volume, or Hubble horizon is a conceptual horizon defining the boundary between particles that are moving slower and faster than the speed of light relative to an observer at one given time. Note that this does not mean the particle is unobservable; the light from ...

  5. Hubble's law - Wikipedia

    en.wikipedia.org/wiki/Hubble's_law

    The Hubble length or Hubble distance is a unit of distance in cosmology, defined as cH −1 — the speed of light multiplied by the Hubble time. It is equivalent to 4,420 million parsecs or 14.4 billion light years. (The numerical value of the Hubble length in light years is, by definition, equal to that of the Hubble time in years.)

  6. Center of mass - Wikipedia

    en.wikipedia.org/wiki/Center_of_mass

    The experimental determination of a body's center of mass makes use of gravity forces on the body and is based on the fact that the center of mass is the same as the center of gravity in the parallel gravity field near the earth's surface. The center of mass of a body with an axis of symmetry and constant density must lie on this axis.

  7. Hubble Space Telescope - Wikipedia

    en.wikipedia.org/wiki/Hubble_Space_Telescope

    The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, renowned as a vital research tool and as a public relations boon for astronomy.

  8. History of the center of the Universe - Wikipedia

    en.wikipedia.org/wiki/History_of_the_center_of...

    A mandala creates a world center within the boundaries of its two-dimensional space analogous to that created in three-dimensional space by a shrine. [6] In medieval times some Christians thought of Jerusalem as the center of the world (Latin: umbilicus mundi, Greek: Omphalos), and was so represented in the so-called T and O maps. Byzantine ...

  9. Local Group - Wikipedia

    en.wikipedia.org/wiki/Local_Group

    The Triangulum Galaxy (M33) is the third-largest member of the Local Group, with a mass of approximately 5 × 10 10 M ☉ (1 × 10 41 kg), and is the third spiral galaxy. [6] It is unclear whether the Triangulum Galaxy is a companion of the Andromeda Galaxy; the two galaxies are 750,000 light years apart, [ 7 ] and experienced a close passage 2 ...