An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

The 24th part of a day; 60 minutes.
An angular unit of right ascension, equivalent to 15°.

Hour, from M.E. houre, from O.Fr. hore, from L. hora "hour, time, season," from Gk. hora "any limited time," used of day, hour, season, year; cognate E. → year.

Sâ'at, from Ar.

A telescope based coordinate specifying the angle, in the equatorial plane, from the meridian to a plane containing the celestial object and the north and south celestial poles.

→ hour; → angle.

A great circle passing through an object and the → celestial poles intersecting the → celestial equator at right angles.

→ hour; → circle.

A device for measuring time; it consists of a glass container having two compartments from the uppermost of which a quantity of sand runs in an hour into the lower one through a narrow tube.

Hour glass, from → hour + → glass.

Sâat-e šeni, from sâat, → hour + šeni, adj. of šen "sand."

A unit of energy equivalent to one kilowatt (1 kW) of power expended for one hour (1 h) of time. The kilowatt-hour is not a standard unit in any formal system, but it is commonly used to measure the consumption of electrical energy. To convert to → joules, use: 1 kWh = 3.6 × 10⁶ J = 3.6 × 10¹³→ ergs.

→ kilo-; → watt-hour.

The angle on the celestial sphere measured westward from the hour circle of the vernal equinox to that of the celestial body.

→ sidereal; → hour angle.

A unit of time used in the Roman and Ottoman empires that divided the day from sunrise to sunset into 12 equal numbers of hours, resulting in long summer hours and short winter hours.

M.E., from O.Fr. temporal, from L. temporalis "of time, temporary," from tempus (genitive temporis) "time, season, proper time or season," → time; → hour.

Sâ'at→ hour; fasli, of or pertaining to fasl→ season.

Unit of work or energy, equal to one watt for one hour, or 3.6 x 10¹⁰ ergs., or 3600 joules. The kilowatt-hour (kWh), i.e. 1,000 watts over the period of one hour, is the usual unit or measure of electricity supply or consumption. 1 kWh = 3.6 x 10⁶ J.

→ watt; → hour.

The number of → meteors expected to be seen under ideal conditions if the → radiant of the → meteoroid stream is at the → zenith of the → observer.

→ zenith; → hour; → rate.