Horizon \Ho*ri"zon\, n. [F., fr. L. horizon, fr. Gr. ? (sc. ?)
the bounding line, horizon, fr. ? to bound, fr. ? boundary,
limit.]
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.
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And when the morning sun shall raise his car
Above the border of this horizon. --Shak.
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All the horizon round
Invested with bright rays. --Milton.
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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.
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3. (Geol.) The epoch or time during which a deposit was made.
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The strata all over the earth, which were formed at
the same time, are said to belong to the same
geological horizon. --Le Conte.
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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.
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5. The limit of a person's range of perception, capabilities,
or experience; as, children raised in the inner city have
limited horizons.
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6. [fig.] A boundary point or line, or a time point, beyond
which new knowledge or experiences may be found; as, more
powerful computers are just over the horizon.
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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.
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Apparent \Ap*par"ent\, a. [F. apparent, L. apparens, -entis, p.
pr. of apparere. See Appear.]
1. Capable of being seen, or easily seen; open to view;
visible to the eye; within sight or view.
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The moon . . . apparent queen. --Milton.
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2. Clear or manifest to the understanding; plain; evident;
obvious; known; palpable; indubitable.
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It is apparent foul play. --Shak.
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3. Appearing to the eye or mind (distinguished from, but not
necessarily opposed to, true or real); seeming; as the
apparent motion or diameter of the sun.
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To live on terms of civility, and even of apparent
friendship. --Macaulay.
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What Berkeley calls visible magnitude was by
astronomers called apparent magnitude. --Reid.
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Apparent horizon, the circle which in a level plain bounds
our view, and is formed by the apparent meeting of the
earth and heavens, as distinguished from the rational
horizon.
Apparent time. See Time.
Heir apparent (Law), one whose to an estate is indefeasible
if he survives the ancestor; -- in distinction from
presumptive heir. See Presumptive.
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Syn: Visible; distinct; plain; obvious; clear; certain;
evident; manifest; indubitable; notorious.
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