視距外( 通信 ) OH
1. The line which bounds that part of the earth's surface visible to a spectator from a given point; the apparent junction of the earth and sky.
And when the morning sun shall raise his car
Above the border of this horizon. --Shak.
All the horizon round
Invested with bright rays. --Milton.
2. Astron. (a) A plane passing through the eye of the spectator and at right angles to the vertical at a given place; a plane tangent to the earth's surface at that place; called distinctively the sensible horizon. (b) A plane parallel to the sensible horizon of a place, and passing through the earth's center; -- called also rational horizon or celestial horizon. (c) Naut. The unbroken line separating sky and water, as seen by an eye at a given elevation, no land being visible.
3. Geol. The epoch or time during which a deposit was made.
The strata all over the earth, which were formed at the same time, are said to belong to the same geological horizon. --Le Conte.
4. Painting The chief horizontal line in a picture of any sort, which determines in the picture the height of the eye of the spectator; in an extended landscape, the representation of the natural horizon corresponds with this line.
Apparent horizon. See under Apparent.
Artificial horizon, a level mirror, as the surface of mercury in a shallow vessel, or a plane reflector adjusted to the true level artificially; -- used chiefly with the sextant for observing the double altitude of a celestial body.
Celestial horizon. Astron. See def. 2, above.
Dip of the horizon Astron., the vertical angle between the sensible horizon and a line to the visible horizon, the latter always being below the former.
Rational horizon, and Sensible horizon. Astron. See def. 2, above.
Visible horizon. See definitions 1 and 2, above.
n 1: the line at which the sky and Earth appear to meet [syn: apparent
horizon, visible horizon, sensible horizon, skyline]
2: the range of interest or activity that can be anticipated;
"It is beyond the horizon of present knowledge" [syn: view,
3: a specific layer or stratum of soil or subsoil in a vertical
cross section of land
4: the great circle on the celestial sphere whose plane passes
through the sensible horizon and the center of the Earth
[syn: celestial horizon]