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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 ...
Assuming dark energy remains constant (an unchanging cosmological constant) so that the expansion rate of the universe continues to accelerate, there is a "future visibility limit" beyond which objects will never enter the observable universe at any time in the future because light emitted by objects outside that limit could never reach the ...
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 ...
Tegmark and others [168] have argued that, if space is infinite, or sufficiently large and uniform, identical instances of the history of Earth's entire Hubble volume occur every so often, simply by chance. Tegmark calculated that our nearest so-called doppelgänger is 10 10 115 metres away from us (a double exponential function larger than a ...
The Hubble eXtreme Deep Field (XDF) was completed in September 2012 and shows the farthest galaxies ever photographed at that time. Except for the few stars in the foreground (which are bright and easily recognizable because only they have diffraction spikes), every speck of light in the photo is an individual galaxy, some of them as old as 13.2 billion years; the observable universe is ...
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fundamental questions about its origin, structure, evolution, and ultimate fate. [1]
In 1927, by combining various measurements, including Hubble's distance measurements and Vesto Slipher's determinations of redshifts for these objects, Georges Lemaître was the first to estimate a constant of proportionality between galaxies' distances and what was termed their "recessional velocities", finding a value of about 600 km/s/Mpc.
In modern physical cosmology, the cosmological principle is the notion that the spatial distribution of matter in the universe is uniformly isotropic and homogeneous when viewed on a large enough scale, since the forces are expected to act equally throughout the universe on a large scale, and should, therefore, produce no observable inequalities in the large-scale structuring over the course ...