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Within an apparent horizon, light does not move outward; this is in contrast with the event horizon. In a dynamical spacetime, there can be outgoing light rays exterior to an apparent horizon (but still interior to the event horizon). An apparent horizon is a local notion of the boundary of a black hole, whereas an event horizon is a global notion.
The horizon is the apparent curve that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This curve divides all viewing directions based on whether it intersects the relevant body's surface or not.
Azimuth is measured eastward from the north point (sometimes from the south point) of the horizon; altitude is the angle above the horizon. The horizontal coordinate system is a celestial coordinate system that uses the observer's local horizon as the fundamental plane to define two angles of a spherical coordinate system: altitude and azimuth.
The equatorial describes the sky as seen from the Solar System, and modern star maps almost exclusively use equatorial coordinates. The equatorial system is the normal coordinate system for most professional and many amateur astronomers having an equatorial mount that follows the movement of the sky during the night. Celestial objects are found ...
Clouds near the horizon are typically further away from the viewer, while those high in the sky are closer, giving the impression of a flat, or gently curved, sky surface. An apparent distance theory evidently was first clearly described by Cleomedes around 200 A.D. The theory proposes that the horizon Moon looks larger than the zenith Moon ...
Go to a location with a good view of the horizon because the comet will not appear very high up in the sky until it's dimmer Give your eyes a few minutes to adjust to the dark
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
NASA experts say the darker the sky, the better your chances of seeing stars and celestial events. You may need to travel to make that happen, and if you need assistance in choosing destinations ...