In general relativity, an apparent horizon is a surface that is the boundary between light rays that are directed outwards and moving outwards, and those directed outwards but moving inwards.
Apparent horizons are not invariant properties of a spacetime. They are observer-dependent, and in particular they are distinct from absolute horizons.
See, however, the articles on ergosphere, Cauchy horizon, the Reissner-Nordström solution, photon sphere, Killing horizon and naked singularity; the notion of a horizon in general relativity is subtle, and depends on fine distinctions.
Read more about Apparent Horizon: Definition, Differences From The (Absolute) Event Horizon
Famous quotes containing the words apparent and/or horizon:
“I am from time to time congratulating myself on my general want of success as a lecturer; apparent want of success, but is it not a real triumph? I do my work clean as I go along, and they will not be likely to want me anywhere again. So there is no danger of my repeating myself, and getting to a barrel of sermons, which you must upset, and begin again with.”
—Henry David Thoreau (1817–1862)
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