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The reachable Universe as a function of time and distance, in context of the expanding Universe.. In cosmology, the event horizon of the observable universe is the largest comoving distance from which light emitted now can ever reach the observer in the future.
The particle horizon, also called the cosmological horizon, the comoving horizon, or the cosmic light horizon, is the maximum distance from which light from particles could have traveled to the observer in the age of the universe. It represents the boundary between the observable and the unobservable regions of the universe, so its distance at ...
The particle horizon (also called the cosmological horizon, the comoving horizon (in Scott Dodelson's text), or the cosmic light horizon) is the maximum distance from which light from particles could have traveled to the observer in the age of the universe.
Event horizon, a boundary in spacetime beyond which events cannot affect the observer, thus referring to a black hole's boundary and the boundary of an expanding universe; Apparent horizon, a surface defined in general relativity; Cauchy horizon, a surface found in the study of Cauchy problems; Cosmological horizon, a limit of observability
Closed trapped surfaces are a concept used in black hole solutions of general relativity [1] which describe the inner region of an event horizon. Roger Penrose defined the notion of closed trapped surfaces in 1965. [2] A trapped surface is one where light is not moving away from the black hole.
where c is the speed of light, k is the Boltzmann constant, ħ is the reduced Planck constant, G is Newton's constant, and A is the surface area of the event horizon. [57] Like any physical system, a black hole has an entropy defined in terms of the number of different microstates that lead to the same macroscopic features.
'90s Week: The 1997 sci-fi horror film flopped in theaters and with critics. On its 25th anniversary, the director tells us about the one thing that made audiences take a second look.
This can be used to define a type of cosmic event horizon whose distance from the Earth changes over time. For example, the current distance to this horizon is about 16 billion light-years, meaning that a signal from an event happening at present can eventually reach the Earth if the event is less than 16 billion light-years away, but the ...