沙罗周期

Saros \Sa"ros\, n. [NL., fr. Gr. ?] (Astron)
1. A Chaldean astronomical period or cycle, the length of
which has been variously estimated from 3,600 years to
3,600 days, or a little short of 10 years. --Brande & C.

2. A length of time (6535.82 days, or 18 years 11.32 days,
assuming 4 leap years in that interval), after which the
eclipses of the sun repeat their pattern, but are shifted
120[deg] west.


Cycle \Cy"cle\ (s?"k'l), n. [F. ycle, LL. cyclus, fr. Gr.
ky`klos ring or circle, cycle; akin to Skr. cakra wheel,
circle. See {Wheel}.]
1. An imaginary circle or orbit in the heavens; one of the
celestial spheres. --Milton.

2. An interval of time in which a certain succession of
events or phenomena is completed, and then returns again
and again, uniformly and continually in the same order; a
periodical space of time marked by the recurrence of
something peculiar; as, the cycle of the seasons, or of
the year.

Wages . . . bear a full proportion . . . to the
medium of provision during the last bad cycle of
twenty years. --Burke.

3. An age; a long period of time.

Better fifty years of Europe than a cycle of Cathay.
--Tennyson.

4. An orderly list for a given time; a calendar. [Obs.]

We . . . present our gardeners with a complete cycle
of what is requisite to be done throughout every
month of the year. --Evelyn.

5. The circle of subjects connected with the exploits of the
hero or heroes of some particular period which have served
as a popular theme for poetry, as the legend of Arthur and
the knights of the Round Table, and that of Charlemagne
and his paladins.

6. (Bot.) One entire round in a circle or a spire; as, a
cycle or set of leaves. --Gray.

7. A bicycle or tricycle, or other light velocipede.

8. A motorcycle.
[PJC]

9. (Thermodynamics) A series of operations in which heat is
imparted to (or taken away from) a working substance which
by its expansion gives up a part of its internal energy in
the form of mechanical work (or being compressed increases
its internal energy) and is again brought back to its
original state.
[Webster 1913 Suppl.]

10. (Technology) A complete positive and negative, or forward
and reverse, action of any periodic process, such as a
vibration, an electric field oscillation, or a current
alternation; one period. Hence: (Elec.) A complete
positive and negative wave of an alternating current. The
number of cycles (per second) is a measure of the
frequency of an alternating current.
[Webster 1913 Suppl. + PJC]

{Calippic cycle}, a period of 76 years, or four Metonic
cycles; -- so called from Calippus, who proposed it as an
improvement on the Metonic cycle.

{Cycle of eclipses}, a period of about 6,586 days, the time
of revolution of the moon's node; -- called {Saros} by the
Chaldeans.

{Cycle of indiction}, a period of 15 years, employed in Roman
and ecclesiastical chronology, not founded on any
astronomical period, but having reference to certain
judicial acts which took place at stated epochs under the
Greek emperors.

{Cycle of the moon}, or {Metonic cycle}, a period of 19
years, after the lapse of which the new and full moon
returns to the same day of the year; -- so called from
Meton, who first proposed it.

{Cycle of the sun}, {Solar cycle}, a period of 28 years, at
the end of which time the days of the month return to the
same days of the week. The dominical or Sunday letter
follows the same order; hence the solar cycle is also
called the {cycle of the Sunday letter}. In the Gregorian
calendar the solar cycle is in general interrupted at the
end of the century.