ho·ri·zon /həˈraɪzṇ/
 地平線,地平;眼界,見識


 horizon
 視距外( 通信 ) OH


 horizon
 軸 時軸


 Ho·ri·zon n.
 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.

 ◄ ►


 horizon
      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,
          purview]
      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]